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iX Google Scholar

Explore these independent scientific papers to learn more about how iX Cameras is contributing to scientific research in universities and corporations worldwide.
Capillary-enhanced two-phase micro-cooler using copper-inverse-opal wick with silicon microchannel manifold for high-heat-flux cooling application
Elsevier
This paper describes a cooling system for microelectronics to efficiently dissipate heat while maintaining operation temperature within acceptable limits. An i-SPEED 7 high-speed camera from iX Cameras was used to closely monitor boiling dynamics during the experiments. [Read More]
Author: H Kwon, Q Wu, D Kong, S Hazra, K Jiang, S Narumanchi, H Lee, JW Palko, EM Dede
Abstract:
In this work, we demonstrate a two-phase capillary-fed boiling micro-cooler that consists of a ≈ 25-μm-thick copper inverse opal (CIO) porous wicking structure for high-heat-flux boiling and a silicon 3D-manifold for distributed liquid delivery and vapor extraction across a 0.5 cm × 0.5 cm heated area. At low inlet water mass flow rates of 1.5 to 1.9 g(min)−1, the micro-cooler displays nearly two-phase boiling with exit vapor quality ≈ 1 and a high critical heat flux (CHF) of 253 to 320 W cm−2 with low superheat of ≈ 10 °C resulting in a thermal resistance of boiling ≈ 0.025 cm2 °C W−1 or heat transfer coefficient of 0.4 MW m−2 °C−1. For higher flow rates of 5, 10, and 15 g(min)−1, the micro-cooler exhibits a hybrid single-phase and two-phase cooling regime where the contribution of the sensible heat (single-phase) cooling is linearly added to that of the two-phase cooling. For the highest flow rate of 15 g(min)−1, the CHF is increased to ≈ 500 W cm−2 resulting in an overall thermal resistance of ≈ 0.18 cm2 °C W−1. However, the two-phase heat transfer effectiveness, which estimates the utilization level of the inlet mass flow rate for two-phase boiling, is reduced to ≈ 0.11. To achieve the best cooling system performances, the micro-cooler must operate entirely within the two-phase boiling regime (exit vapor quality or two-phase heat transfer effectiveness ≈ 1). Ideally, the “coolant” should be delivered near its saturation temperature (≈ 100 °C for water), which provides significant advantages for the energy-efficient operation of data centers and power electronics. We present detailed analysis with Infrared and high speed camera images at various inlet flow rates and heat fluxes to understand complex heat transfer in the micro-cooler. Furthermore, a conjugate thermofluidic simulation model, which incorporates the physics of capillary-fed boiling in a porous copper layer, agrees well with the experimental data.
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Metal vapor-induced arc instability in stationary TIG-welding
Springer
These experiments in welding arc stability are based on a special setup with a separate lateral laser generation of metal vapor into a TIG arc between two tungsten electrodes. The process was recorded using an i-SPEED 220 high-speed camera from iX Cameras. [Read More]
Author: I Henze, T Mattulat
Abstract:
The stability of the arc in arc welding processes is primarily relevant to the joint quality. However, the influencing factors which determine the arc stability are still partly unknown. Combining arc welding with laser welding enhances arc stability. The laser-induced metal vapor is often named as one stabilizing factor. But this contradicts the presumptions of arc welding researchers who mentioned the metal vapor as a destabilizing factor especially when high amounts are present in the arc. This investigation analyzes the specific influence of metal vapor on arc conductivity as one aspect of arc stability by producing metal vapor using a laser process on a separately placed substrate material. Furthermore, the arc current was varied at a constant metal vapor amount. The investigations show that the metal vapor presence increases the arc voltage by at least 20% and its fluctuation amplitude by at least 51% which was presumed to mean a decreased electrical conductivity and therefore decreased arc stability. The arc instability was lower for higher arc currents at constant metal vapor amounts. Therefore, higher arc currents increase the arc stability of welding arcs in the presence of a constant metal vapor amount.
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Role of oil droplet size on dynamic pore wetting of active carbon and particle-bubble interaction: New inspiration for enhancing the porous mineral floatability
Elsevier
This paper investigates the dynamic pore wetting behavior of active carbon particles in the water-oil emulsion using low-field nuclear magnetic resonance. An i-SPEED 713 high-speed camera was used to perform measurements during the experiments. [Read More]
Author: Y Mao, P Shen, L Dong, X Yu, G Xie, Y Li, H Wang, W Xia, D Liu
Abstract:
The dynamic pore wetting plays a vital role in the flotation separation process of porous mineral particles, such as low-rank coal, fly ash and chrysocolla, etc. This paper investigated the dynamic pore wetting behavior of active carbon particles in the water-oil emulsion by 1H low-field nuclear magnetic resonance (1H LF-NMR). The influence of oil droplet size on pore wetting process was revealed. The change in the surface properties of particles before and after wetting was analyzed by contact angle and FTIR measurements. The particle-bubble attachment process in the emulsion and pure water was compared. The total pore wetting percentage of active carbon had a first-order kinetic relationship with the wetting time. The emulsion was beneficial to decrease the pore wetting percentage of particles compared with water. And the pore wetting percentage decreased with the decrease of oil droplet size in emulsion. The pores were easily filled by the oil droplet with small size and the hydrophobicity of sample surface was improved, which prevented the subsequent pore wetting by water. As a result, the detachment force of particle-bubble was increased with the help of micro-oil droplets. This work attempts to provide a new inspiration for the study of porous mineral flotation.
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Elucidating the transfer dynamics of high-viscosity silver paste for laser-induced forward transfer of continuous line
Elsevier
In this paper, the transfer dynamics of high-viscosity silver paste for LIFT (laser-induced forward transfer) of continuous line are investigated over hundreds of laser pulses. The side view of the paste transfer process was captured at 5000 fps by an i-SPEED 221 high-speed camera from iX Cameras. [Read More]
Author: Yanmei Zhang, Xiuli He, Chongxin Tian, Yucui Yu Zhuang Shu, Gang Yu, Shaoxia Li
Abstract:
Laser-induced forward transfer (LIFT), as an innovative 3D direct-write method, has been increasingly applied for various material printing in many applications. Elucidating the transfer process of paste is crucial to manipulate the printing quality. In this work, the transfer dynamics of high-viscosity silver paste in LIFT of continuous line was systematically investigated based on the cumulative effect from images obtained over hundreds of laser pulses. The influences of process parameters, including the laser energy input (single pulse energy, repetition frequency, and scanning speed) and the thickness of paste film, on the bump height and expansion velocity of bump front were analyzed. With increasing the single pulse energy or repetition frequency, or decreasing the scanning speed or film thickness, the evolution of bump morphology and sputtering varies from just a tiny bump with no sputtering, to a moderate-sized bump with a small amount of sputtering and rebounding, and further to a large bump with intense sputtering and rebounding. A non-dimensional group in terms of Reynolds and Weber numbers was proposed to categorize different evolution regimes and claim the physical mechanism on LIFT of continuous line. When the Reynolds number is greater than 0.01 and the Weber number is greater than 0.1, the inertial effect is sufficient to resist the viscous and capillary effects, inducing the paste to bulge and transfer downwards. A moderate-sized bump with no visibly fragmented sputtering is desirable for the transfer of continuous grid lines. The forming status of grid lines can be predicted according to the behavior of paste transfer, and the predicted grid line state agrees well with the actual state. This can provide process and theoretical references for printing continuous grid lines with LIFT.
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Transverse impacts‐induced deformation and damage of 3D angle‐interlock woven composites at elevated temperatures
Wiley Online Library
This paper investigates impact tests of 3D woven composites conducted at elevated temperatures. The damage process was recorded at 25,000 fps with an i-SPEED 716 high- speed camera from iX Cameras. [Read More]
Author: Chunlei Ren, Jingnan Wei, Menglong Jia
Abstract:
This paper investigated the effect of elevated temperature on the impact-induced deformation and damage behavior of 3D angle-interlock woven composites. The transverse impacts were carried out at high temperatures of 90°C and 130°C using Split Hopkinson Pressure Bar matched with controlled environmental device. A meso-scale finite element model considering the thermal-mechanical coupling has been developed, and the numerical results were compared with the experimental data and high-speed photography to study the effect of temperature and reinforcement architecture on the dynamic behaviors of the composites. The damage mechanisms at elevated temperatures were studied. Results show that the impact resistance of the 3D angle-interlock woven composites degraded at the glassy region of the epoxy resin, then enhanced at the glass transition temperature (Tg), this phenomenon became more pronounced in the warp direction. Such behavior should be ascribed to the improved toughness and ductility of the resin matrix. The local plastic deformation of resin before damage slowed down matrix cracking and composites failure. Further, the reinforcement play a key role in the adiabatic heating and plastic deformation of the composites at high temperature.

Highlights

  • The impact test of 3D woven composites was conducted at elevated temperatures.
  • The high temperature significantly affects the dynamic properties of composites.
  • The increased toughness and plasticization of resin diminished impact damage.
  • A mesoscale thermo-mechanical coupled finite element model was developed.
  • The reinforcement plays a key role in the damage process and adiabatic heating.
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Exploring debris flow deposit morphology in river valleys: Insights from physical modeling experiments
Elsevier
In this study, a series of laboratory experiments were conducted to investigate the impact of the water content, slope, and grain size distribution on the deposit morphology of debris flows in river valleys. An i-SPEED 7 series camera from iX Cameras was positioned on a riverbank to capture the movement of debris flows. [Read More]
Author: CJ Li, YX Hu, G Fan, QY Zhu, DR Liu, JW Zhou
Abstract:
A comprehensive understanding of the deposit morphodynamics of debris flows in river valleys is crucial for disaster prevention and mitigation in mountainous areas. However, debris flows in river valleys are complex and variable, and the influence of the composition and terrain on deposit mechanisms and morphology remains unclear. In this study, a series of laboratory experiments were conducted to investigate the impact of the water content, slope, and grain size distribution on the deposit morphology of debris flows in river valleys. In the experiments, debris flows form narrow and elongated shuttle-shaped deposits upon entering river valleys. Increased water content and slope enhance the mobility of debris flows, resulting in wider deposit widths, gentler deposit slopes, and larger deposit areas. An increase in the gravel fraction partially facilitates the movement and deposition of debris flows. However, a large number of coarse particles may increase internal friction within the debris flow, hindering the spread of deposits and resulting in a relatively concentrated deposit with a steeper morphology. Furthermore, the debris flow regime shifts from friction to collision as the water content, slope, and gravel fraction increase. Debris flows dominated by collision forces exhibit higher mobility and a wider impact area, potentially leading to more severe disaster consequences. Compared with unconfined debris flows, the deposit area of debris flows in the river valley is smaller, and the deposit width to height ratio is larger. There is a power function relationship between deposition area and Savage number in river valleys. Additionally, particle sorting and flow regime transformation during the movement and deposition of debris flows can significantly impact the morphology and internal structure of the deposits in river valleys and then affect the development of debris flow dam breaching. In summary, this study utilized experiments to simulate natural debris flows, offering fresh insights into the depositional behavior of debris flows in river valleys.
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Influence of a hemispherical bulge on a flat wall upon the collapse jet of cavitation bubbles
AIP Publishing Physics Fluids
An i-SPEED 510 from iX Cameras was utilized to record the rapid collapse behaviors of cavitation bubbles. The collapse was induced by a hemispherical bulge on a flat wall. [Read More]
Author: X Wang, C Zhang, J Shen, Y Zhang, X Xi
Abstract:
Uneven sections along a wall cause local flow deterioration and can result in severe cavitation erosion. This paper investigates the influence of a hemispherical bulge on a flat wall upon the collapse dynamics of a cavitation bubble in terms of the Kelvin impulse theory and high-speed photography based on the Weiss theorem and the image method. The evolution and characteristics of the bubble collapse morphology, the flow field distribution, and the Kelvin impulse (in terms of strength, direction, and directional sensitivity) are analyzed for symmetric and asymmetric configurations. The results show that the bubble collapse jet can be divided into three scenarios: mainly induced by the hemispherical bulge, mainly induced by the flat wall, and broadly equivalent effects of both. Additionally, as the dimensionless distance between the bubble and the flat wall increases, the range of the jet attraction zone induced by the bulge initially increases, subsequently decreases, and ultimately converges to the diameter of the bulge. The maximum width of the attraction zone can reach 3.45 times the radius of the bulge. Finally, the spatial sensitivity of the jet direction is found to be significant near the junction between the flat wall and the bulge.
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Ammonia absorption by water droplet in a small controlled atmosphere wind tunnel
Elsevier
Ammonia absorption into a water droplet was investigated using particle tracking velocimetry (PTV) with polystyrene microspheres. An ultrahigh-speed i-SPEED 716 camera from iX Cameras was used to capture the motion trajectories of the stained microspheres inside the droplets. [Read More]
Author: J Bai, W Wang, G Qiu, X Huang, P Yin, Z Li, L Teng
Abstract:
The mass transfer characteristics during ammonia absorption into a sessile water droplet in a small controlled-atmosphere wind tunnel were investigated using particle tracking velocimetry (PTV) with polystyrene microspheres. The results showed that the flow field inside the droplet transformed from Marangoni convection to Rayleigh convection in the absence of gas flow. As the gas velocity increased, the drag force-induced circulation inhibited the Marangoni convection in the initial stage of the mass transfer process and Rayleigh convection in the advanced stage. However, the suppressed Marangoni convection cells recurred at high initial ammonia concentrations. Compared with the initial ammonia concentration in the wind tunnel and droplet size, the gas velocity significantly increased the gas-phase mass transfer coefficient. Furthermore, a calculation model for ammonia absorption by a moving droplet was derived based on the Colburn analogy and the two-film theory. The gas-phase mass transfer coefficients calculated using the model coincided with the experimental results. These results will help the design of water curtains.
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Deciphering controls of pore‐pressure evolution on sediment bed erosion by debris flows
Advancing Earth and Space Sciences
An i-SPEED 7 Series high-speed camera from iX Cameras in the cross-stream direction recorded the erosion process. [Read More]
Author: H Zheng, X Hu, Z Shi, D Shen, T De Haas
Abstract:
Pore-fluid pressure (PP) plays an important role in bed erosion, but the mechanisms that control PP evolution and the resulting feedbacks on flow dynamics are unclear. Here, we develop a general formulation, allowing quantification of the propensity for PP evolution of saturated and unsaturated bed sediments. We conduct erosion experiments by systematically varying grain composition and water content of beds, for investigating effects of PP evolution on flow erosion. With increasing water content, PP shows a slight rise in deforming beds with drained behavior but significant larger rise in undrained beds. Regardless of bed composition, the erosion rate of beds presents a synchronous change tendency with PP evolution due to the loss in basal friction. PP instigates positive feedback that induces a remarkable gain of flow velocity and momentum on wet beds with undrained behavior. Our results help explain observations of volume growth and long run out of debris flows.
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Experimental study on crack propagation characteristics of unconventional reservoir rocks
Elsevier
The fracture behavior differences of shale, sandstone, and coal were carefully compared in this study. DIC was used to track the evolution of the strain and displacement fields on the surface of the specimen, and the increase in crack propagation was recorded with a high-speed camera from iX Cameras. [Read More]
Author: Z Wang, H Lian, W Liang, P Wu, W Li, Y Yu
Abstract:
This study investigates the fracture behaviour of three types of specimens (shale, sandstone, and coal), which are commonly found in unconventional reservoirs, based on mode Ⅰ single-edge notch beam (SENB) test. We employ the Digital Image Correlation technique to track the strain evolution and crack propagation paths of the three types of materials and compare their fracture characteristics. The experimental results show that both the surface roughness and crack initiation angle of the coal are larger comparing with that of sandstone and shale, which demonstrates the ductile property of coal and fracturing difficulty in coal seam. Moreover, the average velocity difference of crack propagation is obvious, which is 53.76 × 103, 453, and 0.33 mm/s in shale, sandstone, and coal, respectively. The elastoplastic J-R curves, which reflects the influence of the plastic zone, are presented to analyze the energy dissipation characteristics of three types of specimens during crack propagation. It is found that the J-integral of shale and sandstone does not increase with crack propagation, but the J-integral of coal shows obvious increasing trend with crack propagation due to the effect of plasticity. In addition, microscopic analysis is conducted using a petrographic microscope and scanning electron microscope (SEM) to explain the plastic zone differences at the notch tips of shale, sandstone, and coal. This study is a preliminary and significant step of hydraulic fracturing application in unconventional reservoirs for efficient recovery of the berried natural gas.
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Salinity-Driven Interface Self-Assembly of a Biological Amphiphilic Emulsifier to Form Stable Janus Core–Shell Emulsion for Enhancing Agrichemical Delivery
ACS Publications
This study turns waste into treasure by combining metal ions in agrichemicals with natural amphiphilic molecules to prepare stable emulsions for enhancing agrichemical rainfastness and weakening environmental risk. Impact processes on the PTFE surface were recorded with an i- SPEED 508 camera from iX Cameras. [Read More]
Author: Y Wu, Z Bao, S Zhang, R Liu, Y Ping, M Ma, Y Gao, C He, T Wu, Y Ma, C Zhang, F Du
Abstract:
Agrichemical losses are a severe threat to the ecological environment. Additionally, some agrichemical compounds contain abundant salt, which increases the instability of formulations, leading to a lower agrichemical utilization and soil hardening. Fortunately, the biological amphiphilic emulsifier sodium deoxycholate alleviates these problems by forming stable Janus core–shell emulsions through salinity-driven interfacial self-assembly. According to the interfacial behavior, dilational rheology, and molecular dynamics simulations, Janus-emulsion molecules are more closely arranged than traditional-emulsion molecules and generate an oil–water interfacial film that transforms into a gel film. In addition, at the same spray volume, the deposition area of the Janus emulsion increased by 37.70% compared with that of the traditional emulsion. Owing to the topology effect and deformation, the Janus emulsion adheres to rice micropapillae, achieving better flush resistance. Meanwhile, based on response of the Janus emulsion to stimulation by carbon dioxide (CO2), the emulsion lost to the soil can form a rigid shell for inhibiting the release of pesticides and metal ions from harming the soil. The pyraclostrobin release rate decreased by 50.89% at 4 h after the Janus emulsion was exposed to CO2. The Chao1 index of the Janus emulsion was increased by 12.49% as compared to coconut oil delivery in soil microbial community. The Janus emulsion ingested by harmful organisms can be effectively absorbed in the intestine to achieve better control effects. This study provides a simple and effective strategy, which turns waste into treasure, by combining metal ions in agrichemicals with natural amphiphilic molecules to prepare stable emulsions for enhancing agrichemical rainfastness and weakening environmental risk.
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Numerical Analysis of Thermal Flow Dynamics of Arc Plasma and Molten Pool in Hollow Cathode Arc Welding with Oxygen Content
MDPI
The mechanism of the pulsed Hollow Cathode Arc Welding (HCAW) process was revealed using a fully coupled model with a hollow cathode. The shape of the welding arc was captured by an i-SPEED 7 Series camera from iX Cameras. [Read More]
Author: Y Yang, B Du, J Huang, Z Lei, F Xu, Q Sun, P Wei, D Wang
Abstract:
The mechanism of the pulsed hollow cathode arc welding (HCAW) process was revealed using a fully coupled model with a hollow cathode. We solved the governing equations with the Marangoni effect to study the dynamic behaviors of a molten pool with a square pulsing current (200~400 A, 900 Hz) and varying O2 content; the dynamics of the arc plasma and the weld pool in the HCAW process were investigated quantitatively. The results show that the intensity of the arc plasma was more significantly weakened by the design of the hollow cathode in HCAW than that in GTAW with a solid hollow cathode. We could obtain a stable molten pool even with a large pulsing current section (200 A–400 A) at higher frequencies. The flow dynamics of the molten pool were mainly dominated by the Marangoni effect with varying oxygen content, and we could promote penetration by increasing O2 content in HCAW.
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Preparation of core-shell structured Al-5Li@ HTPB powders with improved stability and combustion performance by using perfluoroalkylsilane as a surfactant
Elsevier
The ignition and combustion processes of AI-5Li and AI-5Li@HTPB powders were captured with an i-SPEED 726 high-speed camera from iX Cameras. [Read More]
Author: J Zhu, S Wang, W Xiong, J Wang, X Li, M Zou
Abstract:
Aluminum-lithium alloy powder exhibits better thermal properties and combustion performances than aluminum, thus showing promising applications in the field of energetic materials such as explosives and propellants. However, the high activity of lithium also raises issues of stability and compatibility with propellant components, deteriorating the powder's overall performance. In this study, a facile coating method is presented using 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFOTS) as a surfactant to coat hydroxyl‑terminated polybutadiene (HTPB) on the surface of Al-5Li powder, forming the core-shell composite Al-5Li@HTPB. The microstructure and chemical composition characterized by SEM, EDS, XPS, FT-IR, and nano-CT demonstrated that a uniform and dense layer was successfully coated on the surface. The thermal analysis results showed a significant improvement in the thermal properties and stability compared to pure Al-5Li. In addition, ignition tests were conducted, and the results showed that Al-5Li@HTPB could reduce the ignition delay time and significantly reduce agglomeration. Overall, our strategy provides a novel method to solve the stability issues of Al-Li powders and simultaneously enhance combustion performance.
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Controllable self‐transport of bouncing droplets on ultraslippery surfaces with wedge‐shaped grooves
Wiley
The impact behaviors of droplets under various impact velocities are explored. The impact process was recorded using an i-SPEED 726R high-speed camera from iX Cameras. [Read More]
Author: C Yue, Q Dai, X Yang, C Gachot, W Huang, X Wang
Abstract:
Preventing the accretion of droplets on surfaces is vital and slippery liquid-infused porous surfaces (SLIPS) have promising application prospects, such as surface self-cleaning and droplet transportation. In this work, controllable self-transport of bouncing droplets on ultraslippery surfaces with wedge-shaped grooves is reported. The impact behaviors of droplets on SLIPS under various impact velocities and diameters are explored, which can be classified as hover, total bounce, partial bounce, Worthington jet, and crush. SLIPS with wedge-shaped grooves were designed to transport accreted droplets. An energy and transport model is established to explain the impact and self-transport mechanism, where the Laplace pressure and moving resistance between droplets play a key role. Finally, SLIPS with branched wedge-shaped grooves were designed for droplet self-transport and demonstrated advantages. This work provides a general reference for spontaneous motion control of sessile droplets, droplets with initial impacting velocity, or even liquid films.
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Regression Rate and Combustion Efficiency of Composite Hybrid Rocket Grains Based on Modular Fuel Units
MDPI
The coaxial core section of the combustion engine’s injector was a fiber optic viewport, which was connected via fiber optics to an i-SPEED 220 high-speed camera and acted as a carrier of radiation luminescence. [Read More]
Author: J Pan, X Lin, Z Wang, R Wang, K Wu, J Liang, X Yu
Abstract:
This study investigated combustion characteristics of composite fuel grains designed based on a modular fuel unit strategy. The modular fuel unit comprised a periodical helical structure with nine acrylonitrile–butadiene–styrene helical blades. A paraffin-based fuel was embedded between adjacent blades. Two modifications of the helical structure framework were researched. One mirrored the helical blades, and the other periodically extended the helical blades by perforation. A laboratory-scale hybrid rocket engine was used to investigate combustion characteristics of the fuel grains at an oxygen mass flux of 2.1–6.0 g/(s·cm2). Compared with the composite fuel grain with periodically extended helical blades, the modified composite fuel grains exhibited higher regression rates and a faster rise of regression rates as the oxygen mass flux increased. At an oxygen mass flux of 6.0 g/(s·cm2), the regression rate of the composite fuel grains with perforation and mirrored helical blades increased by 8.0% and 14.1%, respectively. The oxygen-to-fuel distribution of the composite fuel grain with mirrored helical blades was more concentrated, and its combustion efficiency was stable. Flame structure characteristics in the combustion chamber were visualized using a radiation imaging technique. A rapid increase in flame thickness of the composite fuel grains based on the modular unit was observed, which was consistent with their high regression rates. A simplified numerical simulation was carried out to elucidate the mechanism of the modified modular units on performance enhancement of the composite hybrid rocket grains.
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Single-track geometrical characteristics under different energy input and mass addition in coaxial laser cladding
Springer
The observation system comprised a pneumatic powder feeder, two strong LED light sources, and an i-SPEED 210 high-speed camera from iX Cameras. [Read More]
Author: YH Bian, CX Tian, B Chen, BX Dong, SX Li, ZY Li, YR Nan, XL He, G Yu
Abstract:
To provide a broad processing window with a high deposition rate, a comprehensive analysis of single-track geometrical characteristics over a wide range of laser energies and mass inputs in laser cladding is necessary. The formation of a single cladding track of Inconel 718 on a substrate by coaxial laser cladding, with a wide range of laser power from 1 200 W to 3 900 W and a powder feeding rate from 5 g/min to 35 g/min, was studied from both theoretical and experimental points of view. A quantitative model of powder concentration distribution was developed based on the powder transport morphology obtained by high-speed photography. Linear regression models were established between nine geometrical characteristics and the combined process parameters of laser power and powder feeding rate, written as PαFβ, to quantitatively analyze the geometrical characteristics of the clad. These were confirmed by large correlation coefficients and analysis of residuals. From the findings we deduced that more energy input enhanced the outward direction of Marangoni convection, leading to the melt pool undergoing evolution from shallow dilution and flat dilution to fluctuating dilution. An almost linear relationship was found between the cladding width, W, and the laser power, indicating that laser energy accumulation was a major factor in the evolution of W. The increase ratio of the cladding height, hc, ranged from 640% to 360% along with an increase in the powder feeding rate, implying that the evolution of hc, was dominated by the powder feeding rate. The total area of the cross-section, A; the area of the clad, Ac; the area of the molten substrate, Am; the total height of the cross-section, H; the penetration depth, hm; the dilution ratio, D; and the wetting angle, θ, were determined by a complex coupling of energy input and mass accumulation, and they are proportional to P0.5F0.2, P0.2F0.5, P0.5/F0.2, P0.3F, P0.5/F0.2, P0.2/F0.2, and P0.2/F0.2, respectively. This research aims to provide general knowledge on the influence of energy input and mass addition on the geometrical characteristics of the clad and its related influence mechanism. Such information could provide a reference and basis for promoting the practical application of laser cladding technology.
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Multiple ballistic impacts of UHMWPE fiber metal laminates: Experiments and simulations
Elsevier
The ballistic performance of UHMWPE fiber metal laminate plates under multiple ballistic impacts were investigated. Two i-SPEED 720 high-speed cameras from iX Cameras captured the impact events from different views and measure the projectile veolocity. [Read More]
Author: C Ni, J Zhang, L Qiang, B Zheng, Z Zhao, J Deng, F Chen, R Zhang
Abstract:
Fiber metal laminate (FML) has demonstrated great potential as a multifunctional structure with ballistic resistance capabilities. Typical projectile weapons, such as sub-machine guns or machine guns equipped with 7.62 mm ammunition, can cause multiple impacts at various locations. However, the specific behavior of FML under multiple ballistic impacts has remained unclear. To address this gap, a comprehensive investigation was conducted to explore the ballistic performance of FML under multiple impacts by a combined experimental and numerical method. The FML composed of two steel layers and one UHMWPE composite layer was subjected to both single and double impact tests. Cylindrical blunt projectiles with a caliber of 7.62 mm were utilized, with impact velocities ranging from 200 to 400 m/s. By adjusting the position of clamping fixture and keeping the projectile trajectory constant, a horizontal offset of 15 mm was set between the locations of the first and second impacts. Additionally, three-dimensional finite element simulations were employed to elucidate the penetration mechanisms of FML. The results revealed that the damage and failure caused by the first impact had minimal influence on the subsequent ballistic performance, and a consistent resistance against penetration under multiple ballistic impacts could be maintained when the spacing distance between impact points was greater than 15 mm. However, when the spacing distance was reduced, the residual velocities of FML under the three impacts gradually increased. As the velocity of the first impact was gradually increased while keeping the velocity of the second impact constant and above the ballistic limit, tearing cracks were observed to occur on the rear steel sheet of FML plate and then propagated between the penetrated holes, leading to a larger-scale failure area. Moreover, for interval time between impacts greater than 100 μs, there was no significant effect on the residual velocity of the projectiles.
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Experimental investigation of the characteristics of combustion in the full hydrogen blending range of methane-hydrogen mixtures in a MILD model combustor
Elsevier
The combustion stability and pollutant emissions of the jet-induced MILD model combustor were analyzed in comparison to varying hydrogen contents. The reaction zone was captured using a LaVision acquisition system and an intensified charge-coupled device camera, an i-SPEED 7 series high-speed camera from iX Cameras. [Read More]
Author: N Yang, Y Xiong, Z Liu, X Xu
Abstract:
MILD combustion technology is expected to enable safe and stable low-emission combustion of hydrogen-doped fuels, or pure hydrogen fuels, in gas turbines designed for zero-carbon emissions. To improve combustion stability at high hydrogen content while maintaining low NOx emissions, a MILD model combustor was modified, specifically the upstream fuel/air distribution and mixing method. And the combustion stability of the modified MILD combustor was significantly extended. Here, the combustion characteristics of the modified MILD combustor are experimentally investigated at 0–100% hydrogen contents. The investigation results demonstrate that unlike the combustion stability region at low hydrogen concentrations, a narrow thermoacoustic instability region occurs at 60% hydrogen content. As the hydrogen content increases, the instability region becomes narrower while shifting towards lower equivalence ratios. The change in hydrogen content is accompanied by a significant peak energy migration of the dynamic pressure. The OH* chemiluminescence images showed that the heat release zone became more concentrated with increasing hydrogen content. And the dominance of high-frequency peak energy correlates to lateral motion, whereas the dominance of low-frequency peak energy corresponds to axial motion. This transition in flame dynamics occurs not only for different hydrogen contents but also for different equivalence ratios of pure hydrogen combustion. In contrast, NOx emissions are not sensitive to hydrogen content. At the same time, the MILD model combustor produces low emissions, with NOx emissions of less than 10 ppm@15%O2 at adiabatic flame temperatures ranging from 1200 K to 2100 K. These results show that the MILD model combustor has favorable fuel suitability.
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Advancing sustainable casting through cryogenic gradient forming of frozen sand molds: design, error control, and experimental validation
Elsevier
The fracture mechanics model and chip formation mechanism of frozen sand mold cutting were analyzed. Time-series photos of frozen chips were obtained using a high-speed digital camera (i-SPEED 726 from iX Cameras) with the capability of capturing up to 1,000,000 fps. [Read More]
Author: J Shi, Z Shan, H Yang, S Dong, Q Liu
Abstract:
Owing to its exceptional casting performance, substantial utilization of recycled sand, and environmentally sustainable characteristics, frozen sand mold casting technology has found extensive application across diverse sectors, including aerospace, power machinery, and the automotive industry. The focus of the present study was on the development of frozen sand mold formulations tailored for efficient machining, guided by the performance and cutting fracture mechanism of frozen sand molds. A regional temperature control device was developed for the purpose of conducting cryogenic cutting experiments on frozen sand molds with varying geometrical characteristics and molding materials. The impact of milling process parameters on the dimension accuracy of both sand molds and castings, as well as castings’ surface roughness, were systematically investigated by a whole-process error flow control method. The findings indicate that precise and efficient processing of complicated sand molds was achievable by using sand particles with sizes ranging from 106 to 212 μm, and water content between 4 and 5 wt.%, freezing temperature below –25°C, and cutting temperature within the range of –5 to 0 ℃. Through the frozen-casting of representative components, it was validated that the machining error of the frozen sand mold was within ± 0.25 mm. Additionally, the dimensional accuracy of the flywheel shell casting conformed to the CT8 specifications. This study provides theoretical guidance for the selection of frozen-casting sand formulations and close-loop control of process size chains for complex metal parts, as well as an overall solution for the realization of sustainable development of green casting.
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Non‐coalescence of nonidentical droplets in oil under a DC electric field
Wiley
Excessive electric field strength causes the droplets to contact but not coalesce, severely deteriorating the oil-water separation efficiency. An ultra high-speed camera (i-SPEED 716 from iX Cameras) is employed to capture the coalescence and non-coalescence processes of droplets in the electric field. [Read More]
Author: X Huang, M Chen, Y Huang, X Luo, L Teng, L Xiao, J Li
Abstract:
Excessive electric field strength causes the droplets to contact but not coalesce, severely deteriorating the oil–water separation efficiency. The investigation of the non-coalescence of nonidentical droplets in oil under a DC electric field is conducted using high-speed photography. The effects of droplet volume ratio and interfacial tension ratio on the characteristics and critical parameters for droplet non-coalescence are systematically explored. The results show the critical electrocapillary number for the non-coalescence of nonidentical droplets and critical contact cone angle decreases as the volume sum increases or the interfacial tension ratio decreases, which is related to the competition between the resultant electric field force and the interfacial tension force. These results contribute to optimizing the operating parameters of the electric coalescer and improving the oil–water separation efficiency.
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Effect of characteristic structure of nested composite hybrid rocket fuel grain on combustion properties
Elsevier
i-SPEED high-speed camera uses in hybrid rocket fuel study. [Read More]
Author: R Wang, X Lin, Z Wang, K Wu, J Pan, Z Zhang, J Luo
Abstract:
This study investigates ways to improve the combustion properties of composite grain. The flame images were directed to an optical fiber by a gradient-index lens and captured using an i- SPEED 220 high-speed camera from iX Cameras.
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Process comparison of laser deep penetration welding in pure nickel using blue and infrared wavelengths
Springer
i-SPEED 7 Series high-speed camera in laser welding process. [Read More]
Author: M Möbus, R Pordzik, A Krämer, T Mattulat
Abstract:
In laser beam deep penetration welding, the total absorption is significantly increased compared to heat conduction mode welding. An i-SPEED 7 high-speed camera from iX Cameras was used for spatter tracking in an experimental welding setup. This setup included measurements of airborne acoustic emissions.

The high-speed camera i-Speed7 (iX Cameras Ltd.) with an AF 180 mm 3.5 Di LD Macro 1:1 SP lens (TAMRON Europe GmbH) and a connected BN810 narrow near-IR bandpass filter was used for spatter tracking with a frame rate of 20 kHz and a resolution of 1064 × 762 pixel (0.007 mm per pixel). It was positioned 90° to the welding direction and in a 0° tilt angle so that an image section of about 7 mm width and 5 mm height around the process zone could be captured.
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Reaction process and temperature-resistant properties of B/KNO3/PVDF composites using thermal analysis
Elsevier
iX high-speed camera used to study thermal analysis techniques. [Read More]
Author: C Li, M Li, H Song, X Zhan, C Xu, B Ye, J Wang
Abstract:
Using thermal analysis techniques to explore the relationship between temperature and physical and chemical changes in materials is crucial for studying the reaction process of energetic materials. The combustion process of energetic sticks at different heating temperatures and heating times was observed using an i-SPEED 221 high-speed camera from iX Cameras.
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Intensification of flotation separation process of residual carbon from coal gasification fine slag using ultrafine carbon particles conditioning
Taylor & Francis
i-SPEED high-speed camera used in coal separation study. [Read More]
Author: Y Liang, H Wang, R Chen, D Li, Q Tian, L Li, H Zhang
Abstract:
This process uses flotation to separate residual carbon from coal gasification fine slag. An i- SPEED 230 high-speed camera from iX Cameras was used to record the process.
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Research on the Internal Flow Difference between Peak and Valley Conditions of Water Jet Propulsion Pump during Working at Hump Region
MDPI.com
An i-SPEED high-speed camera was used in cavitation research. [Read More]
Author: H Han, Y Long, J Zhong
Abstract:
A water jet propulsion pump is used to generate propulsion for watercraft. Vibrations in the pump were identified in these tests. An i-SPEED 3 high-speed camera from iX Cameras was used to capture the position and morphological evolution of cavitation inside impellers.
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Vortex dynamics in the near wake of a surface-mounted hemisphere
AIP.org
i-SPEED 7 Series high-speed camera used in PIV and hydrogen bubble visualization techniques. [Read More]
Author: J Liu, J Wang, Y Zhu, C Pan - Physics of Fluids
Abstract:
In this study, the dynamics of vortical structures for the flow over an isolated surface-mounted hemisphere are investigated with time-resolved particle image velocimetry and hydrogen bubble visualization techniques. Particle images were recorded by an i-SPEED 716 high-speed camera from iX Cameras.
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Preparation and combustion properties of laminated sticks of B–CuO and B–Bi2O3
Elsevier
i-SPEED 2 Series high-speed camera used to record combustion properties. [Read More]
Author: S Haoyu, L Chenyang, G Fubing, C An, L Shijiao
Abstract:
The combustion process of the sticks was recorded by i-SPEED 221 high-speed cameras from iX Cameras. The cameras captured the macroscopic combustion effect of the stick at a frame rate of 2000 fps and an exposure time of 300 µs, and the microscale combustion effect of the stick at a frame rate of 1000 fps and an exposure time of 100 µs.
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Dynamic strength and full-field cracking behaviours of pre-cracked rocks under impact loads
Elsevier
i-SPEED 7 Series high-speed camera used to study dynamic strength and cracking of impact loads. [Read More]
Author: L Liu, H Li, G Zhang, S Fu
Abstract:
Impact loads have a significant influence on the dynamic strength and cracking behaviors of pre-cracked rocks, which plays a key role in the stability and safety of rock engineering. In this study, impact tests were performed by using a split Hopkinson pressure bar in conjunction with a high-speed photography technique performed with an iX Cameras i-SPEED 7.
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Efficient electro-demulsification of O/W emulsions and simultaneous oil removal enabled by a multiscale porous biocarbon electrode
Elsevier
i-SPEED 2 Series high-speed camera was used to capture the dynamics of the demulsification process. [Read More]
Author: K Wang, H Zhao, Y Zhang, X Li, M Xu, M Song
Abstract:
Wastewater may contain substantial amounts of oil and additives, which pose threats to the environment and human health. Demulsification is a crucial pretreatment stage for wastewater. An i-SPEED 221 high-speed camera from iX Cameras was used to capture the dynamics of the demulsification process.
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Effects of Al powder on the reaction process and reactivity of B/KNO3 energetic sticks
Elsevier
The i-SPEED 221 high-speed camera is used to track flame propagation of energetic sticks during burning. [Read More]
Author: C Li, M Li, H Song, C Xu, L Gao, B Ye, J Wang
Abstract:
Boron/potassium nitrate (B/KNO3) is a type of critical energetic composite material (ECM). However, the inert oxide layer on the B surface of B/KNO3 hinders the contact between pure fuel and oxidant, thus limiting energy release This limitation could be eliminated by adding highly reactive Al powder. To discern the effects of Al powder size on the reaction process and reactivity of B/KNO3, this study prepared Al/B/KNO3/polyvinylidene fluoride (PVDF) energetic sticks using the direct ink writing (DIW) technology. This study characterized the macroscopic morphology and structure of the energetic sticks using a laser scanning microscope and a scanning electron microscope, examined the reaction process of the composites using a differential scanning calorimeter and a thermogravimetric analyzer, and observed the flame propagation behavior of energetic sticks and energetic architectures using a high-speed camera. Furthermore, it tested the pressure output characteristics of the energetic composites using a closed volume tank. The results show that adding Al powder can improve the combustion efficiency of B/Al composite fuels and reduce the agglomeration of the combustion products. The Al powder with various particle sizes affects various reaction stages of the composite. The combustion and pressure output tests suggest that adding Al powder with a particle size of 1 μm yielded high reactivity and that flame jump propagation appeared in energetic architectures when the channel spacing was below 10 mm. These findings provide a guide for modifying the B/KNO3 energetic composites and regulating the reactivity of energetic sticks.
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Rapid surface texturing to achieve robust superhydrophobicity, controllable droplet impact, and anti-frosting performances
Springer
iX Camera i-SPEED 726 high-speed camera used to study droplet impact. [Read More]
Author: Q Dai, L Chen, J Pan, L Shi, D Liu, W Huang, X Wang
Abstract:
Robust superhydrophobic surfaces with excellent capacities of repelling water and anti-frosting are of importance for many mechanical components. In this work, wear-resistant superhydrophobic surfaces were fabricated by curing a mixture of polyurethane acrylate (PUA) coating and 1H,1H,2H,2H-Perfluorodecyltrichlorosilane (HFTCS) on titanium alloy (TC4) surfaces decorated with micropillars pattern, thus, composite functional surfaces with PUA coating in the valleys around the micropillars pattern of TC4 were achieved. Apparent contact angle on fabricated surfaces could reach 167°. Influences of the geometric parameters of micropillars pattern on the apparent contact angle were investigated, and the corresponding wear-resistant property was compared. Droplet impact and anti-frosting performances on the prepared surfaces were highlighted. An optimized design of surface texture with robust superhydrophobicity, controllable droplet impact, and anti-frosting performances was proposed. This design principle is of promising prospects for fabricating superhydrophobic surfaces in traditional mechanical systems.
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Lubricant Droplets Can Bounce on Wetted Cylinders
Journal of Materials and Engineering
The i-SPEED 726R records droplet bounce phenomenon of polyalphaolefin, olive oil, silicone oil, and paraffin oil on wetted cylinders was reported. [Read More]
Author: C Yuea, Q Daia, J Wanga, W Huanga, X Wanga
Abstract:
In this work, the droplet bounce phenomenon of polyalphaolefin, olive oil, silicone oil, and paraffin oil on wetted cylinders was reported. With a uniform oil film with a thickness of 0.06 mm formed on the cylinder, typical categories of spread, maximum, retract, deposit, and bounce existed. The ratio of the maximum spreading diameter and the initial diameter was negatively corrected with the viscosity due to the viscous resistance. The effect of tangential velocity from 0 m/s to 0.75 m/s on the spreading was investigated, which shows a strong promotion for it. The force analysis explained the mechanism of bouncing caused by the compressed air film, and oil droplets would bounce if the support force was larger than the combined force of gravity and inertia force. The findings in the work provide a basic understanding of droplets impact on wetted and rotating surfaces and design concepts for applications in modern industry.
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Local control of magnetic microbubble behavior by magnetic field and pulsed ultrasound
Elsevier
The i-SPEED 727 high-speed camera is used to study the localization of magnetic microbubbles (MMBs), shown to be essential to the efficacy in therapeutic application such as targeted drug delivery. [Read More]
Author: Z Du, R Pan, F Li, R Mo, C Wang
Abstract:
The localization of magnetic microbubbles (MMBs) to a target site has been shown to be essential to their efficacy in therapeutic applications such as targeted drug delivery and gene therapy. In this work, the MMBs’ dynamic equations of vibration, horizontal and vertical motion in a fluid-filled tube, subject to a magneto-acoustic complex field, are established by Lagrange method. The responses and capture efficiency under three ultrasonic pulses waveform in a magnetic field are numerically analyzed. The regulation effects of the external field are observed by experiments. The results show that the transport behavior is influenced by bubble size, original position, liquid flow rate, tube diameter, parameters of acoustic and magnetic field. For the same acoustic parameters, square wave pulse can make stronger vibrate compared with cosine wave and sawtooth wave, which pushes MMBs closer to the magnet. In addition, high frequency and large amplitude pulse are benefit to translation, and increasing the cycle number in a single pulse can also promote translation. In practical applications, variable parameters such as bubble speed and magnet length can be used to improve the capture efficiency. The observations of high-speed camera are consistent with the prediction of theoretical model, which indicates the model is mostly correct.
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Effect of ultrasonication on rising characteristics of a single gas bubble
Elsevier
An i-SPEED 230 high-speed camera from iX Cameras was used to investigate the effect of ultrasonication on bubble rising behaviors in deionized water and MIBC (Methyl Isobutyl Carbinol) solution. [Read More]
Author: Y Liang, H Wang, R Zhou, D Li, H Zhang
Abstract:
In recent years, ultrasonication has been used to enhance flotation process. Gas bubble is the unique carrier during mineral flotation, and thus its characteristics play an important role. However, the bubble rising characteristics under ultrasound action are not clear. Therefore, this paper aims to investigate the effect of ultrasonication on bubble rising behaviors in deionized water and MIBC (Methyl Isobutyl Carbinol) solution. A laboratory visualization system of bubble motion with ultrasonication was designed based on the high-speed dynamic video technology to record the bubble rising process and analyze bubble rising characteristics. Bubble aspect ratio was found to increase with the surfactant concentration increasing, but the rising velocity was in opposite state. In each solution, a significantly higher bubble sphericity was observed with ultrasonication than that without ultrasonication, conversely, the bubble rising velocity was smaller under the action of ultrasonication. A roughly negative linear relationship was found between the bubble shape and rising velocity, and the ultrasonication diminished this relationship. Marangoni effect was considered as the cause of MIBC affecting the bubble motion, and possible explanations of ultrasonication affecting the bubble motion were given from the perspective of bubble surface wave, cavitation bubble oscillation and sound radiation force.
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Adaptive powder nozzle setup for enhanced efficiency in laser metal deposition
aip.org
Laser-based additive manufacturing is an increasingly important production technology for the processing of metallic materials. An i-SPEED 7 high-speed camera from iX Cameras was used to capture high-speed videos to observe the powder entering the melt pool and being ejected from the powder injector. [Read More]
Author: A Bohlen, T Seefeld - Journal of Laser Applications
Abstract:
Laser metal deposition (LMD) is a blown powder process used for the additive manufacturing of large and/or complex parts. The laser spot size is determined by the fiber optic cable and the imaging ratio of the process optics. Spot sizes typically used in LMD can range from 200 μm to several millimeters, whereby zoom optics can be employed to change the laser spot focus within seconds during the process. However, industrial powder nozzles are still static in terms of powder spot size. Changing the powder spot size in line with the laser spot size could ensure the favorable dual outcome of time savings when printing large volumes while also generating fine near-net-shape features. To help overcome the current limitations in the LMD process, this work examines an adaptive powder nozzle setup. In this discrete coaxial layout of three single lateral powder injectors, the individual powder injectors can be adjusted closer to or further from the process to, respectively, dilate or shrink the powder stream focus. Different inner diameters of powder injectors are hereby examined. The resulting powder propagation behavior is characterized for different setups of the single powder nozzles. Single beads are welded with different nozzle setups for fine and coarse powder spots, while the laser spot size is changed accordingly using zoom optics. The laser power is a closed-loop controlled by a two-color pyrometer to achieve comparative process temperatures. The single beads are evaluated with regard to their geometry. High-speed imaging provides supplementary information on weld bead generation.
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Investigation of thermal behavior of powder stream and molten pool during laser-based directed energy deposition
Elsevier
Laser-powder interaction and molten pool evolution are two main physical processes in laser-based directed energy deposition. In this study, the powder stream was generated by a lateral powder feeding device and was observed by an i-SPEED 210 high-speed camera from iX Cameras. [Read More]
Author: B Chen, B Dong, Y Bian, S Li, C Tian, X He, G Yu
Abstract:
Laser-powder interaction and molten pool evolution are two main physical processes in laser-based directed energy deposition (L-DED), which greatly affect the morphology and quality of the deposition layer. In this research, a comprehensive three-dimensional analytical-numerical model which integrates a laser-powder interaction model and material deposition model is developed to study the multi-physics coupling characteristics in L-DED process. The concentration of the powder stream is modeled based on conservation of mass and is in good agreement with the experimental result which is captured by high-speed camera. The effects of main parameters, including laser power, powder feeding rate, powder feeding angle and defocus length on the laser attenuation and the temperature distribution of the in-flight powder particles are analyzed. The results show that the laser attenuation rate increases from 0.72% to 1.36% with the powder feeding angle increasing from 45 deg. to 65 deg-. However, the laser attenuation rate is almost the same with the defocus length of 25 mm, 35 mm and 45 mm. Moreover, the peak powder temperature on the deposition surface increases with the increase of powder feeding angle and decrease of defocus length. Accordingly, the heat and mass input conditions at the molten pool surface for the material deposition model, including powder mass flux, effective laser intensity and powder temperature are obtained from the laser-powder interaction model. The heat transport and fluid dynamics of the molten pool are discussed based on the calculated results from material deposition model. Finally, the calculated molten pool geometry shows good agreement with the experimental results with the relative error <8.5%. This work is helpful in process optimization from the point of view of adjusting the parameters related to the powder stream and deeper understanding of laser-powder interaction and molten pool evolution during the L-DED process.
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Experimental Study on the Fracture Process Zones and Fracture Characteristics of Coal and Rocks in Coal Beds
Springer
… Among them, the i-SPEED 508 high-speed camera produced by IX cameras in the UK was used to capture the failure process of the specimen surface, with a resolution of 1208 × 800, a shutter speed of 1/2000 s, and a frame speed of 25 fps … [Read More]
Author: Z Wang, H Lian, W Liang, P Wu, W Li, Y Yu
Abstract:
In this work, the physical, mechanical, and fracturing properties of three different types of rock (shale, sandstone, and coal) are studied through three-point bending tests. The fracturing characteristics are further investigated by acoustic emission (AE) and digital image correlation (DIC). The modified fracture mechanics (MFM) theory, which considers the influence of fracture process zone (FPZ) length, is constructed to calculate the fracture toughness with greater accuracy than that obtained using standard linear elastic fracture mechanics (LEFM). The experimental results indicate that the coal shows more significant nonlinear fracture behaviour than sandstone and shale. For the geometry of the FPZ, coal has the largest FPZ area, and the FPZ length-to-width ratios for shale, sandstone, and coal are 0.86, 1.96, and 1.93, respectively. Furthermore, the FPZ length varies dramatically, while the FPZ width is almost stable among the three types of rock. Using the proposed MFM approach, the average fracture toughness values of shale, sandstone, and coal are 1.019, 0.419, and 0.058 MPa × m0.5, respectively, which are much lower than those calculated by the standard LEFM. For the average fracture energy, sandstone exhibits the largest value (236.55 J/m2), while coal exhibits the lowest value (42.99 J/m2). These newly observed fracture toughness and fracture energy differences among the three materials provide a theoretical basis for the implementation of hydraulic fracturing in the joint exploitation of shale gas, tight sandstone gas, and coalbed methane.
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Stab resistance mechanism of lightweight PLA/CFRP hybrid composite structures
Science Direct
… Moreover, we used an i-SPEED 716 high-speed camera (IX Cameras Ltd, UK) with 10,000 frames per second to record the local changes during the impact process. Because the surface of CFRP is smooth epoxy resin, to avoid the reflex during … [Read More]
Author: Z Du, Z Liu, C Chen, X Wang
Abstract:
The preparation of lightweight and high-performance material is of great significance for developing stab-resistant clothing. This paper proposes a stab-resistant composite structure combining lightweight polylactic acid (PLA) and carbon fiber reinforced polymer (CFRP). The effect of stacking sequence and filling density on the puncture resistance of composite structures was investigated by dynamic puncture and quasi-static puncture. Puncture load, energy and depth are studied as key parameters of puncture resistance. This paper investigated composite structures' failure process and damage morphology using high-speed camera photography and microscopic imaging techniques. The results show that the composite structure exhibits the strongest puncture resistance when CFRP is designed on the top layer of PLA. The higher the filling density, the lower the puncture depth of the composite structure, but the increase in the overall weight eventually leads to a decrease in the puncture specific energy (PSE). The introduction of the bottom PLA delays the penetration point of the composite structure and increases the absorption of the penetration energy by the CFRP before penetration. The final damage modes of composite structures include fiber fracture, slip and pull-out, matrix fracture and peel damage, as well as fracture damage and plastic deformation of PLA materials.
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2D spectrum slicing for sequentially timed all-optical mapping photography with 25 frames
Applied Physics
Sequentially timed all-optical mapping photography (STAMP) is a promising technology for observing ultrafast phenomena. Increasing the frame number during one shot is critical to enhance the capability of STAMP, but the rearrangement of the frames significantly intensifies the complexity of the system. In this work, we design a spectrum-slicing method, allowing for the separation and arrangement of the frames simultaneously in a two-dimensional manner. [Read More]
Author: Z Li, X Yuan, Y Weng, D Wang, S Wang, S Liu
Abstract:
Sequentially timed all-optical mapping photography (STAMP) is a promising technology for observing ultrafast phenomena. Increasing the frame number during one shot is critical to enhance the capability of STAMP, but the rearrangement of the frames significantly intensifies the complexity of the system. In this work, we design a spectrum-slicing method, allowing for the separation and arrangement of the frames simultaneously in a two-dimensional manner. The experimental results show that our system can capture 25 images in one shot with a spatial resolution of 2.46 μm and a frame rate of 2.5 Tfps, indicating its potential for the observation of highly dynamic events
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Experimental study of the quasi-static and dynamic fracture toughness of notched and repaired concrete using semi-circular bend method
Elsevier
This study uses an i-SPEED 716 to obtain the initiation and propagation processes of fracture in repaired concrete specimens. [Read More]
Author: R Cai, J Mao, H Qi, J Qu, Q Guo
Abstract:
Concrete constructions commonly contain cracks or defects during forming and service, repair operations are necessary in many situations. However, limited investigations conducted on the dynamic fracture toughness (DFT) of repaired concrete structures. This paper investigates the cracking behavior of concrete structures through notched dynamic semi-circular bend (NSCB) tests performed using a split Hopkinson pressure bar (SHPB) apparatus with two measurement techniques, namely digital image correlation (DIC) and crack propagation gauge (CPG), to capture the flying half angular velocity and crack propagation speed of NSCB concrete specimens under various loads. The results demonstrate a linear increase in both DFT and crack propagation speed of concrete with the loading rate. Additionally, a threshold value exists beyond which the crack speed stabilizes, and the DFT is not evidently influenced by the notch depths. The cracks propagate along the aggregates and remain mostly intact under a relatively low loading rate. With an increased loading rate, the damage pattern of some otherwise deflected aggregates changes resulting in crack penetration and significantly reducing the fracture surface roughness. Repaired specimens exhibit greater energy dissipation at the same loading rate, thereby producing flying fragments with lower kinetic energy, which can prevent secondary damage to internal personnel and structures.
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Polarisation and rheology characterisation of monoolein/water liquid crystal dynamical behaviour during high-viscosity injector extrusion
Elsevier
An i-SPEED 2 Series camera was set up to capture the polarization-mediated transmission of the sample stream. Still images were extracted, and the intensity differences along a stream of small crystals and lipids were analyzed and plotted. [Read More]
Author: C Darmanin, F Babayekhorasani, A Formosa
Abstract:
Hypothesis - The use of monoolein/water mixtures in serial crystallography experiments using high-viscosity injectors (HVI) results in significant departures from equilibrium behaviour. This is expected to include changes in phase, viscosity, and associated flow behaviour. It should be possible to detect these changes, in-situ, using a combination of polarisation and rheology characterisation techniques. Experiments - A systematic study was performed using monoolein, varying the water content to create a range of mixtures. Injection induced phase changes within the HVI flow were established using real-time cross-polarization measurements. Dynamic flow characteristics and viscosity was characterized by particle tracking and rheology. Findings - HVI injection induces deformation and phase changes within monoolein (MO)/water mixtures which can be detected through variations in the transmitted intensity during in-situ polarisation studies. The heterogeneity of the extruded sample results in a highly viscous cubic phase in the central region of the stream and a less viscous lamellar-rich phase at the edges adjacent to the walls. The extent of these variations depends on sample composition and injection conditions. Shear-thinning behaviour and increasing heterogeneity in the vicinity of the capillary walls under dynamic flow conditions. This is the first report observing injection induced dynamical behaviour in MO/water mixtures under realistic flow conditions.
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Enhancing fluidization quality of nanoparticle agglomerates by combining vibration, stirring and jet assistances
Elsevier
The images of fluidization were recorded using a high-speed camera from iX Cameras. [Read More]
Author: L Zhang, D Liu, X Wu, W Zhang, H Feng
Abstract:
Gas fluidization is an efficient method to process nanoparticles. In this study, we employ 3D printing to fabricate a hollow stirring structure of blades with jet holes and position it in a vibrating fluidized bed to realize an integration of vibration, stirring and jetting assistance methods, without increasing structural complexity. The fluidization of SiO2, Al2O3 and TiO2 nanoparticle agglomerates with different primary particle sizes and surface properties are investigated. The combination of vibration and stirring improves the bed expansion obviously, while a further addition of the gas jets at a velocity of a few meters per second allows a further small improvement of bed expansion. The jets slightly reduce the agglomerate size in the dense bed, the agglomerate size at the bed outlet, and the elutriation rate. By combining vibration, stirring and jets, the fluidization is enhanced while the elutriation is kept low during fluidization lasting for a few hours.
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Laboratory investigation of scale effects in bursting failure of quasi-brittle materials
Elsevier
We placed the i-SPEED 726 high-speed camera in front of the coal specimens to record at 40,000 fps. All tested coal specimens exhibited a bursting failure pattern. [Read More]
Author: F Gao, X Peng, G Yuan, W Liu
Abstract:
Understanding the scale effect in the behavior of solid materials is important when small-scale models are used to predict the behavior of real structures. Tremendous efforts have been devoted to investigating the scale effect in the strength of quasi-brittle materials. However, limited studies have focused on the whether there is a scale effect in bursting failure, which is a typical failure pattern of quasi-brittle structures. Here, we conduct a series of unconfined compression tests on coal samples using a specialized designed loading machine to produce bursting failure in the laboratory. We use cubic coal samples with a large range of sizes from 50 to 300 mm to investigate the scale effect in bursting failure of quasi-brittle materials. We use acoustic emission technology to monitor microcreaking within the samples and a high-speed camera to capture the bursting failure process. We demonstrate that there is a strong scale effect in bursting failure of quasi-brittle materials in terms of mechanical properties including compressive strength and deformability, strain energy density, bursting severity, and precursor time. We found that ejection of localized pieces from the skin of the structure is a precursor of catastrophic bursting failure of quasi-brittle materials. We conclude that the relationship between the precursor time (T) and structure size (M) of bursting failure is logarithmic and can be described as logT = a + bM where a and b are constants. This relationship provides a guideline when models obtained from laboratory tests are used to predict strength and behavior at the intermediate (mines and rock slopes) and large scales (earthquakes).
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Towards an Understanding of the Challenges in Laser Beam Welding of Copper – Observation of the Laser-Matter Interaction Zone in Laser Beam Welding of Copper and Steel Using in Situ Synchrotron X-Ray Imaging
Springer
An i-SPEED 727 high-speed camera from iX Cameras was used in the synchrotron X-ray welding setup for the experimental copper welding process. [Read More]
Author: F Kaufmann, J Schrauder, M Hummel, C Spurk
Abstract:
The increasing demand for contacting applications in electric components such as batteries, power electronics and electric drives is boosting the use of laser-based copper processing. Laser beam welding is a key for an efficient and high-quality electric vehicle production due to its local, non-contact energy input and high automation capability enabling reproducible weld quality. Nevertheless, a major challenge in process design is the combination of energy-efficiency and precise process guidance with regard to weld seam depth and defect prevention (i.e. spatter, melt ejections), partly caused by the high thermal conductivity of copper. High power lasers in the near infrared range and emerging visible laser beam sources with excellent beam quality can provide a suitable joining solution for this purpose. However, the underlying physical phenomena are currently only partly understood and a reflection on the challenges of laser beam welding of copper compared to well researched steel processing has not yet been carried out. In order to improve the understanding of the effect of the different material properties and the influence of process parameters on the vapor capillary and melt pool geometry in laser beam welding, in situ synchrotron investigations on Cu-ETP and S235 using 515 and 1030 nm laser sources were conducted. The material phase contrast analysis was successfully used to distinguish vapor capillary and melt pool phase boundaries during the welding process with high spatial and temporal resolution up to 5 kHz. A significantly different vapor capillary geometry and sensitivity to parameter variation were found between the steel and copper material. In addition, the visualization of characteristic melt flows revealed different melt pool dynamics and a pronounced eddy close to the melt pool surface for copper, which is assumed to be causal for the observation of pronounced spatter formation during copper welding in a certain process window.
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Combustion Characteristics of a Swirl-Radial-Injection Composite Fuel Grain with Applications in Hybrid Rockets
MDPI
An i-SPEED 220 from iX Cameras was used to acquire images of the combustion chamber flame in the lab-scale hybrid rocket engine setup. [Read More]
Author: R Wang, X Lin, Z Wang, K Wu, Z Zhang, J Luo, F Li
Abstract:
The combustion characteristics of a swirl-radial-injection composite fuel grain were experimentally and numerically investigated. This composite grain permits swirl-radial oxidizer injection based on three hollow helical blades, each having a constant hollow space allowing uniform oxidizer injection into the main chamber along the axial direction. The oxidizer enters from channel inlets located along a hollow outer wall. This wall, together with the three blades, is fabricated as one piece from acrylonitrile-butadiene-styrene using three-dimensional printing. Paraffin-based fuel is embedded in the spaces between adjacent blades. Firing tests were conducted with gaseous oxygen as the oxidizer, using oxidizer mass flow rates ranging from 7.45 to 30.68 g/s. Paraffin-based fuel grains using conventional fore-end injection were used for comparison. Regression rate boundaries were determined taking into account the erosion of the oxidizer channels. The data show that the regression rate was significantly increased even at the lower limit. Images of the combustion chamber flame and of the exhaust plume were also acquired. The flame was found to be concentrated in the main chamber and a smoky plume was observed, consistent with the high regression rate. A three-dimensional simulation was employed. The present design was found to improve fuel/oxidizer mixing and combustion efficiency compared with a fuel grain using fore-end injection. Both the experimental results and numerical simulations confirmed the potential of this swirl-radial-injection fuel grain.
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Study on the effect of Er:YAG laser irrigation on the root canal system with different mechanical preparation tapers
Stomatology
… Study on the effect of Er:YAG laser irrigation on the root canal system with different mechanical preparation tapers … The root canals were prepared by Er:YAG laser irrigation,hand empty … [Read More]
Author: ZHAO Sijia,HE Xinyu1(),YU Yue2XUE Xiaowei,PAN Chong
Abstract:
Objective To study the effect of Er:YAG laserirrigation on root canal system with different mechanical preparation tapers. Methods Er:YAG laser irrigation process was conducted in different prepared resin tooth models(15/. 05, 20/. 06 and 25/. 08). The bubble oscillation in root canal was recorded by a high speed camera and the gray scale integral of the bubbles was calculated. The third molars with vital pulp were collected and divided into three groups for different taper root canal preparation(13/. 02, 15/. 05, 20/. 06 and 25/. 08)after extraction. The root canals were prepared by Er:YAG laser irrigation, hand empty needle washing and 5.25% NaClO, respectively. The specimens were fixed, decalcified, embedded, sectioned and stained by HE. The residual pulp tissue was observed and analyzed statistically. Results Under the same mono-pulse energy, the gray scale integral of air bubbles in root canals of 15/. 05 group was significantly less than 20/. 06 and 25/. 08 group(P<0.05); there was no significant difference between 20/. 06 and 25/. 08 groups(P>0.05). The pathological results showed that the risk of residual pulp in Er:YAG laser group was lower than that of empty needle group under the same condition(P<0.05). Compared with 25/. 08 group, 15/. 05 group had a higher residual risk of residual pulp(P<0.05), but 20/. 06 group had no significant difference(P>0.05). Conclusion Under same parameters, the effect of Er:YAG laser on root canal system has no significant difference between 20/. 06 and 25/. 08 group, but both groups have better cleaningeffects than 15/. 05 group.
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Effect of adjuvants on physicochemical properties of lime sulfur on flower/paraffin and application on flower thinning
NIH.gov
Impact experiments were performed by high-speed photography method using an i-SPEED 220 from iX Cameras. Droplets fell from a peristaltic pump onto the surface of a flat paraffin plate. The images were analyzed to quantitatively track the droplet’s impact process. [Read More]
Author: Y Li, Y Liu, C Wu, R Zhao, M Li, J Cai, L Ma
Abstract:
Adjuvants can effectively enhance the utilization rate of pesticides, but the application of adjuvants in plant growth regulators is rarely studied.MethodsThis work explored the effects of adjuvants dioctyl sulfosuccinate sodium salt (AOT) and methyl oleate (MO) on lime sulfur (LS), especially the drop behavior on flower and paraffin surface. Results The results showed that the addition of AOT and AOT+MO can significantly reduce the static and dynamic surface tension of LS from 72mN/m to 28mN/m and 32mN/m respectively, and increase the spreading factor from 0.18 to 1.83 and 3.10 respectively, reduce the bounce factor from 2.72 to 0.37 and 0.27 respectively. The fluorescence tracer test showed that the addition of adjuvants could promote the spreading and permeation of droplets. The field test results revealed that the flower thinning rate of adjuvant and non-adjuvant were 80.55% and 54.4% respectively, and the flower thinning effect of adding adjuvant was the same as that of artificial which the flower thinning rate was 84.77%. The quality of apples treated with adjuvants was similar to that treated with artificial, and the weight of single fruit increased by 24.08% compared with CK (spray water).
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Study of the characteristics and combustion efficiency of liquid kerosene/oxygen-enriched air rotating detonation wave with different modes
Elsevier
To capture the optical characteristics of the combustion chamber, an i-SPEED 7 Series high-speed camera was installed at the end of the chamber. The lens of the camera faces the exit direction of the combustion chamber, and a quartz glass baffle is placed between the combustion chamber and high- speed camera to isolate the impact of the exhaust. The camera is maintained at a 600 x 600 resolution to capture the annular combustor with a frame rate of 30,000 fps and is triggered by the rising edge voltage signal. [Read More]
Author: X Han, Y Huang, Q Zheng, Q Xiao, H Xu, F Wang, Y Wu
Abstract:
In a liquid kerosene rotating detonation engine (RDE), detonation waves often exhibit different propagation modes. The propagation characteristics with different modes are worthy of further study. To further investigate the propagation characteristics, a series of experiments was conducted, and the flow field characteristics under different modes were comparatively studied using high-speed photography and pressure sensors. The modal features and mode change trends obtained in the experiments were simulated using numerical methods. Based on this, the combustion efficiencies of the different modes were quantitatively characterized. The results showed that with increasing propellant mass flux, the detonation wave gradually changes from the two-counter wave mode to the single-wave mode, and the interim mode is a hybrid mode. Compared with the two-counter wave mode, the velocity deficit of a single wave is smaller, and the reaction zone is more compact. Numerical simulations show that a higher proportion of fuel is consumed by more violent chemical reactions in the single-wave mode; that is, the combustion efficiency in the single-wave mode is higher than that in the two-wave mode. The results provide a reference for further understanding the liquid fuel detonation phenomenon and improving fuel combustion efficiency.
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Directional fracturing of granite cylinder via nitromethane-based energetic materials driven by electrical wire explosion
AIP.org
Longer period self-luminous images of EM load explosion and fracturing processes of granite cylinders were taken by an i-SPEED 510 high-speed camera from iX Cameras. [Read More]
Author: Q Wang, Y Hu, M Zhang, Z Tao
Abstract:
The combination of electrical wire explosion and low sensitivity energetic materials is an efficient and practical method to generate controllable strong pressure waves, which is a potential alternative to explosives in directional fracturing applications. In this paper, a new configuration of hybrid load is proposed to generate synchronized pressure waves for directional fracturing, with the advantages of lower energy storage and smaller blast-hole diameters. The pressure wave of hybrid load explosion is measured, and the explosion synchronicity of the two loads at the microsecond level is verified by self-illumination images. Then, two-hole granite cylinders are used to verify the feasibility of directional fracturing, and the results show that the double loads explosion formed directional fractures connecting the two holes and a horizontal failure plane. The fracturing process, including fracture initiation, propagation, and connection, is recorded with a high-speed camera and is reproduced in numerical simulation. Based on the experimental and numerical results, the fracture morphology is characterized as four areas, and the fracturing mechanism is analyzed.
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Membrane flux response technology for early warning of initial surface scaling in membrane distillation
Elsevier
An i-SPEED 221 high-speed camera from iX Cameras connected to an online monitor was used to observe the structure of membrane surface during the membrane distillation process. [Read More]
Author: Z Yuan, R Zhao, G Sun, P Li, S Yin, G Zhou
Abstract:
Membrane distillation (MD) is a promising green separation technology for the treatment of high salinity wastewater attributed to excellent salt rejection, which is significant in relevant environmental and chemical engineering application. However, membrane scaling is an inevitable issue during long-term membrane distillation process. Thus, we developed a membrane flux response technology with data processing method to in-situ monitor the membrane scaling according to the reduction of permeate flux. By real-time analyzing the derivative of deviation between theoretical and experimental fluxes, early warning of initial membrane surface scaling was observed at initial nucleation stage. Besides, such timely detection was also achieved under different temperatures and flow velocities of feed solution, even for the poor light transmittance aqueous solution (such as NiSO4 and CoSO4 solution), which exhibited wide application potential on diverse high salinity wastewater systems. In addition, the metastable zone width of salt solution within MD system was obtained for the efficient operation design. To sum up, membrane flux response technology provides an early warning at imminent membrane scaling, which will maintain the great separation effect for a fresh feed solution after a facile cleaning by pure water, indicating the extension of device lifetime.
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Fracture Resistance Biomechanisms of Walnut Shell with High‐Strength and Toughening
Wiley
The kinematics and kinetics of walnut and macadamia dropping from the height of 1m to a rigid plate were analyzed. An i-SPEED 3 high-speed camera with 2000 Hz frequency was used to record the motion (tracks and linear velocity) of walnut and macadamia in the whole process of dropping. [Read More]
Author: Lizhen Wang, Peng Xu, Huan Yin, Yanxian Yue, Wei Kang, Jinglong Liu, Yubo Fan
Abstract:
Walnut shell is lightweight material with high-strength and toughening characteristics, but it is different from other nut shells’ microstructure with two or three short sclerotic cell layers and long bundle fibers. It is essential to explore the fracture resistance biomechanism of lightweight walnut shell and how to prevent damage of bionic structure. In this study, it is found that the asymmetric mass center and geometric center dissipated impact energy to the whole shell without loading concentration in the loading area. Diaphragma juglandis is a special structure improved walnut shell's toughening. The S-shape gradient porosity/elastic modulus distribution combined with pits on single auxetic sclerotic cells requires higher energy to crack expansion, then decreases its fracture behavior. These fantastic findings inspire to design fracture resistance devices including helmets, armor, automobile anti-collision beams, and re-entry capsule in spacecraft.
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Droplets bouncing on rotating curved surfaces with elevated temperatures
Elsevier
… droplets bouncing on curved surfaces with elevated temperatures are reported. The bouncing … droplets bouncing on wetted and curved surfaces with elevated temperatures. … [Read More]
Author: C Yue, Q Dai, W Huang, X Wang
Abstract:
In this work, droplets bouncing on curved surfaces with elevated temperatures are reported. The bouncing and depositing phenomena of different lubricant droplets are confirmed. The influence of initial diameter, tangential velocity, and surface roughness on the impact dynamics of silicone oil droplets on wetted curved surfaces is investigated, and the temperature dependence of the bouncing phenomenon is highlighted. Bouncing and depositing thresholds under various conditions are summarized. It is found that surface roughness has the most significant negative effect on the bounceable velocity range, followed by initial diameter and tangential velocity. A theoretical model and force analysis are established to explain the bouncing mechanism. The modified Bond numbers and Ohnesorge numbers are introduced to predict the bouncing thresholds. This work provides sufficient experimental and theoretical insights into manipulating droplets bouncing on wetted and curved surfaces with elevated temperatures.
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Measurement of surface tension with free-falling oscillating molten metal droplets: a numerical and experimental investigation
Springer
The last droplet to exit the crucible typically has a larger initial deformation and lower initial velocity. The droplet generation process triggers an i-SPEED 210 from iX Cameras. The high-speed images are used to determine the oscillation frequency of the produced droplets. [Read More]
Author: Kiana Fahimi, Lutz Mädler & Nils Ellendt
Abstract:
Rayleigh’s equation has been widely used to determine surface tension from oscillating droplets. In this study, the use of a drop-on-demand droplet generator is proposed to create free-falling, oscillating, molten metal droplets for this purpose. To examine the applicability of the droplet generator, extensive numerical simulations in three and two-dimensions were performed. The effect of gravity, initial velocity and initial deformation on the frequency and pattern of the droplet oscillation was investigated. The use of this generator enables the creation of thousands of droplets in the course of a single experiment and the droplets have a much shorter exposure time to possible unwanted contaminations, due to a rapid measurement principle. Furthermore, the adjustable nozzle size of the generator provides flexibility in terms of droplet size, which affects the range of validity of Rayleigh’s method. To validate the method, the surface tension of molten copper in an argon atmosphere was determined over a temperature range of 1400–1620 K. The determined linear relation is expressed as σ [mN m−1] = (1307 ± 98) − (0.22 ± 0.015) (T−1356) (T in K).
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High-resolution PIV measurements of the shock boundary layer interaction within a highly loaded transonic compressor cascade
scholarworks.calstate.edu
Both snapshot as well as time-resolved PIV measurements are performed on a transonic compressor cascade. [Read More]
Author: J. Klinner, E. J. Munoz Lopez, A. Hergt, C. Willert
Abstract:
Both snap-shot as well as time-resolved PIV (TR-PIV) measurements are performed on a transonic com- pressor cascade to elucidate the underlying shock-boundary layer interaction process. In order to align both the instantaneous passage shock and the boundary layer along with its separation downstream of the shock foot, shadowgraph imagery is acquired synchronous with TR-PIV recordings. Statistics from PIV snapshots reveal that the passage shock fluctuates by up to 13% of the chord. Frequencies of shock motion lay in a range between 500 and 600 Hz with an additional specific tone near 1142 Hz. With TR-PIV, the velocity field in the interaction region is sampled at 20 kHz, which temporally resolves the motion of the shock foot and captures size variations of the separation region. The thickness of the laminar boundary layer (BL) is found to grow as the shock moves downstream. A rapid upstream motion of the shock leads to even higher BL growth rates and large scale flow separation downstream. Proper orthogonal decomposition (POD) of the snap-shot PIV data reveals that 50% of the energy is contained in the first 4 modes. The corresponding POD eigenvalue spectrum exhibits a -11/9 decay slope as predicted in literature for the inertial range of inhomogeneous turbulence.
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Experimental study on propagation, quenching, and re-initiation characteristics of rotating detonation wave with liquid kerosene-oxygen-enriched air
Science Direct
The results of this study reveal the mechanism of liquid fuel quenching and re-initiation. This mechanism significantly restrains the instability of liquid fuel detonation waves. [Read More]
Author: Xinpei Han, Yuanding Wang, Quan Zheng, Yakun Huang
Abstract:
In a rotating detonation engine (RDE), specifically a low-activity liquid fuel RDE, ensuring the continuous and stable propagation of detonation waves is important. In the RDE experiment with oxygen-enriched air as the oxidant and liquid kerosene as the fuel at room temperature, the stability of the rotating detonation wave (RDW) is found to be extremely inadequate. This inadequacy is manifested by more than 10 times of quenching and re-initiation within 500 ms. This frequent quenching and re-initiation phenomena considerably differ from those of the gaseous fuel RDE. Consequently, the velocity deficit of the detonation wave increased and the propulsion performance of the RDE was affected. In a further study using pressure sensors and high-speed cameras, the quenching phenomenon was found to be related to the supply state of the propellant, and the re-initiation phenomenon was related to the chemical reaction zone in the combustion chamber. To verify the foregoing, a special control test was performed. After improving the supply state of the corresponding propellant, the unstable characteristic of liquid fuel was effectively suppressed and a stable RDW with a velocity of 1321 m/s was obtained. The results of this study reveal the mechanism of liquid fuel quenching and re-initiation. This mechanism significantly restrains the instability of liquid fuel detonation waves.
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Design and Test of a Lateral-Approaching and Horizontal-Pushing Transplanting Manipulator for Greenhouse Seedlings
American Society of Agricultural and Biological Engineers
A lateral-approaching and horizontal-pushing transplanting manipulator for greenhouse seedlings was developed to minimize the damage of their stems and leaves during transplanting. Through the high-speed camera test, the end-effector could approach plug seedlings in a lateral sliding way to effectively shelter the seedling plants. [Read More]
Author: Luhua Han, Menghan Mo, Haorui Ma, Francis Kumi, Hanping Mao
Abstract:
A lateral-approaching and horizontal-pushing transplanting manipulator for greenhouse seedlings was developed to minimize the damage of their stems and leaves during transplanting. The manipulator is composed of a pick-up robotic arm, an end-effector, two conveyors, and a control system. The robotic arm liking a spatial 3-DoF displacement mechanism to achieve a point-to-point circuitous locomotion of the end-effector was designed with the mechanism combination innovation method, which consisted of two crossing high-speed linear modules and a pushing slide cylinder. The end-effector of a pincette-type mechanism uses two cylinder fingers and four pins to pick up and release the seedlings. Each conveyor adopts a flat-belt transmission mode to move the plug tray/growth pot to the working position of the end-effector. The control system coordinates the flexible automation of each component. A physical prototype of the manipulator was constructed and its performance was tested under laboratory conditions. Through the high-speed camera test, the end-effector could approach plug seedling in lateral sliding way to effectively shelter the seedling plants. On the whole, the maximum holding angles of these seedling plants were larger than 45° with little effects on the subsequent growth. The corresponding performance tests showed that the average success ratios for automatic transplanting were up to 97.57% for typical pepper and cabbage seedlings. The lateral-approaching and horizontal-pushing transplanting performance was satisfactory.
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Physical dealloying for two-phase heat transfer applications: pool boiling case
Cornell University
In this work, physical dealloying was explored as a simple and green method to microstructure the surface of commercial brass for pool boiling heat transfer coefficient enhancement. An i-SPEED 210 high-speed camera from iX Cameras was utilized to image the boiling process. [Read More]
Author: Artem Nikulin, Yaroslav Grosu, Jean-Luc Dauvergne, Asier Ortuondo, Elena Palomo del Barrio
Abstract:
In this work, physical dealloying was explored as a simple and green method to microstructure the surface of commercial brass for pool boiling heat transfer coefficient enhancement. Three samples were dealloyed for 0.5, 1 and 3 hours at 650 ℃, turning the smooth surface into a porous one with a depth of 175, 200 and 223 μm. The boiling experiments carried out in ethanol at 78 ℃ have shown, that the maximum enhancement of heat transfer coefficient between 110 and 150% was achieved for the sample dealloyed for 0.5 h. Longer intervals of dealloying reduce boiling performance, but it is still much higher compared to smooth brass. This simple method can be customized for various thermal management equipment, such as conventional, plate and micro heat exchangers, all types of heat pipes, HVAC equipment etc., where the heat transfer occurs with phase change.
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Cavitation bubbles structures below a soft boundary in an ultrasonic field
Science Direct
The dynamic behavior of cavitation bubbles plays a critical role in the utilization of cavitation energy. The evolution of bubble clusters below the free surface of tap water with many gas nuclei was observed using an i-SPEED 726 from iX Cameras at 20,000 fps. [Read More]
Author: Fan Li, Chenyang, Xianmei Zhang, Chenghui Wang
Abstract:
We studied the layer structure of bubbles just below water/air and water/EPE (Expand aple poly ephylene) interfaces using high-speed photography. The layer structure was generated by floating spherical clusters, the source bubbles of which were identified to come from the attachment of bubble nuclei at the interface, the floating of bubbles in the bulk liquid, or bubbles generated on the surface of the ultrasonic transducer. The boundary shape affected the layer structure, which assumed a similar profile below the water/EPE interface. We developed a simplified model composed of a bubble column and bubble chain to describe interface impacts and the interaction of bubbles in a typical branching structure. We found that the resonant frequency of the bubbles is smaller than that of an isolated single bubble. Moreover, the primary acoustic field plays an important role in the generation of the structure. A higher acoustic frequency and pressure were found to shorten the distance between the structure and the interface. A hat-like layer structure of bubbles was more likely to exist in the low-frequency (28 and 40 kHz) intense inertial cavitation field, in which bubbles oscillate violently. By contrast, structures composed of discrete spherical clusters were more likely to form in the relatively weak cavitation field at 80 kHz, in which stable and inertial cavitation coexisted. The theoretical predictions were in good agreement with the experimental observations.
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Plume ejection and product in laser cleaning of ferrite paint
Science Direct
This paper discusses ways of optimizing laser defocus distance and lap rate to reduce surface spatter and improve cleaning quality when removing ferrite paint from aircraft. [Read More]
Author: Chen Zou, Shusen Zhao, Haijun Yu, Zhiyan Zhang, Han Liang
Abstract:
Ferrite paint are commonly used on the surface of aluminum alloys. It contains metal oxide particles, significantly affecting laser paint removal when a nanosecond pulsed laser was used to clean the ferrite paint. In this paper, we experimentally investigate and analyze the plume ejection characteristics and the product during the laser cleaning of the paint. Driven by ablative gas recoil pressure, the ferrite paint was vaporized by the laser pulse into a mixture of molten droplets, resin residual particles, and carbides, and they were then ejected from the laser scanning area with the plume to form a black spatter powder on the cleaned surface. A physical model for calculating the ejection angle of the laser-cleaning plume is established. The results show that the thermal diffusion rate of paint and substrate, laser pulse duration, and laser scanning speed determine the plume ejection angle. Optimizing laser defocus distance and lap rate could significantly reduce surface spatter and improve cleaning quality. Furthermore, through the analysis of XPS, we found that the valence state of the residual ferrite paint changes after the laser cleaning and may affect the residual paint's microwave-absorbing performance. Therefore, removing the ferrite paint layer completely and then re-spray rather than only removing a certain paint depth is necessary.
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Experimental and Numerical Investigation of Ballistic Resistance of Polyurea-Coated Aluminum Plates under Projectile Impacts
MDPI
The effects of the spraying thickness and the position on the response of aluminum plates under impact loading were studied with an i-SPEED 508 from iX Cameras. [Read More]
Author: Hubei Key Laboratory of Blasting Engineering of Jianghan University
Abstract:
The effects of the spraying thickness and the position on the response of aluminum plates under impact loading were studied. The impact tests and numerical simulation were conducted for the penetration process of polyurea-coated 2024 aluminum plates with tungsten sphere impacts. The results indicate the impact resistance performance is similar at slower impact velocity (500–1000 m/s), and the front (or double-side) coating has a smaller advantage. When the impact velocity rises to 1500 m/s, the back coating has a better energy-absorbing performance. The polyurea perform more efficiently with the increase in the impact velocity because the elastomer has large-scale deformation. By comparing the different thicknesses of the back coating, the residual velocity of the fragment has small changes and the impact energy absorption increased with the increase in the coating thickness. The separated phenomenon is serious in front of the bonding face with shear compression failure. In the back polyurea layer, the stripping area is smaller than the front bonding face, and the petaloid cracking is formed with tensile failure.
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Molecular selection and environmental evaluation of eco-friendly surfactants to efficiently reduce pesticide pollution
Science Direct
This study provides a new strategy for the development of efficient and environment-friendly pesticide synergists and sustainable agricultural development. [Read More]
Author: Zhenping Bao, Tanling Wu, Rui Liu, Songhao Zhang, Yupu Chen, Tianyue Wu
Abstract:
Surfactants are widely used in industrial and agricultural production, especially as agrochemicals. However, the improvement of pesticide utilization by surfactants as the synergist should be achieved without adverse effects on crops, non-target organisms and related ecological environment, which is a lack of attention. Herein, the influence of the nonionic surfactant Triton X (TX) series with different hydrophilic chain lengths on the “Pesticide-Crop-Ecology” system was systematically studied. The impact behavior of TX droplets on the scallion leaf surface was predicted first by molecular dynamics (MD) simulation. Then the impact behavior, adhesion properties and foliar retention of TX droplets on the scallion leaf were investigated by physical experiments. The results showed that the TX-102 structure could increase leaf retention of pyraclostrobin (PYR) by 15.66% due to its fast molecular migration rate, strong adhesion and appropriate wettability with leaves. Furthermore, the environmental effect of the selected TX-102 was fully evaluated, and it was found that TX-102 was relatively safe for both Vicia faba cells and human 293t cells, although it slightly promoted the effect of PYR on cell apoptosis. Importantly, TX-102 has a potential repair effect on the damage to dominant soil bacteria caused by PYR. This study provides a new strategy for the development of efficient and environment-friendly pesticide synergists and sustainable agricultural development.
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Ignition response of NEPE-based propellants under drop weight through experiments and numerical simulation
Journal of Energetic Material
Experimental and numerical studies were conducted to investigate the effects of drop height on the ignition mechanism of NEPE nitrate ester plasticized polyether-based propellants. A modified drop-weight system was equipped with a high-speed camera to capture the ignition response images during the whole impact process. [Read More]
Author: Hongzheng Duan, Xiao Hou, Kun Yang, Wubuliaisan Maimaitituersun & Fenglei Huang
Abstract:
Experimental and numerical studies were conducted to investigate the effects of drop height on the ignition mechanism of NEPE nitrate ester plasticized polyether-based propellants. A modified drop-weight system was equipped with a high-speed camera to capture the ignition response images during the whole impact process. A macro-mesoscopic thermomechanical model considering the microcrack and viscous shear flow hotspot formation mechanism was established. The experimental results showed that the ignition responses of the propellants heavily depended on drop height, and the main ignition mechanism was viscous shear flow. The whole loading process could be summarized into three stages: radial extension (viscous shear flow), macroscopic crack initiation and ultimate failure (multiple macroscopic cracks or ignition). The ignition threshold was 35 cm. The posttest scanning electron microscopy (SEM) images further revealed that viscous shear flow played an important role in the ignition of propellants. The numerical simulation results indicated that viscous shear flow was the dominant ignition mechanism compared with the microcrack hotspot mechanism. Point A (along L1) was the most dangerous location under the drop-weight experiment. The predicted features of ignition evolution were consistent with the experimental results and prove that the critical drop height of ignition was 35 cm.
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A new strategy for eliminating bottom hole defects during aluminum droplet printing within a broad temperature range
Science Direct
A high-speed camera was used to develop a new strategy for aluminum fabrication. [Read More]
Author: Lin Su, Lehua Qi, Hongcheng Lian, Jun Luo
Abstract:
Fabrication of hole-free aluminum structures through metal droplet-based 3D printing is an important channel for high-performance aluminum parts in aerospace applications. Unfortunately, completely eliminating bottom hole defects has proven challenging due to the narrow printing temperature range and complex hole defect evolution rules. In this work, by tailoring the overlap ratio (η) and substrate temperature (Ts), we proposed a novel strategy to eliminate bottom hole defects of overlapping droplets in a broad temperature range. Combining the high-speed sequence images and the numerical simulation model, the evolution mechanism of bottom hole defects with distinct overlap ratios was revealed. The result demonstrats that the bottom hole defect evolution is dominated by the droplet spreading order and the competition of inertial and capillary forces. Moreover, a regime map was summarized, where the substrate temperature window for the hole-free region at the valley (η = 0) is expanded by 114% compared to the peak (η = 0.6). Finally, a simple and effective strategy was presented, which could enlarge the printing temperature range for eliminating bottom hole defects. This work might provide theoretical guidance for the low-cost and high-quality droplet printing of multitudinous metal components.
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Experimental Study of Strainbursts Caused by Stress Concentration and Local Mine Stiffness Decrease as Mining Proceeds
Springer - Rock Mechanics and Rock Engineering
A high-speed camera was used to evaluate a laboratory experiment to produce strainbursts resulting from excavation-induced stress concentration and local mine stiffness decreasing. [Read More]
Author: Fuqiang Gao, Guiyang Yuan, Wenju Liu & Xiangyuan Peng
Abstract:
The important role of local mine stiffness (LMS) on rock strainbursts has been extensively recognized. Understanding the evolution of LMS as mining proceeds is of significance to rockburst prevention. Existing studies on this topic, however, are limited to theoretical and numerical methods. In this study, an experimental study is performed using in-house built equipment to produce strainbursts resulting from excavation-induced stress concentration and LMS decreasing. The process of excavations and their resultant disturbance is produced using real coal blocks in the laboratory. A novel method is proposed for calculating LMS, based on which the evolution of LMS with excavations is quantitatively evaluated. The influence of initial LMS on the strainbursts is also investigated. The experimental result demonstrated that there is a critical threshold value of LMS below which the coal pillar fails with a bursting pattern. The threshold is related to the post-peak stiffness of the coal pillar. The experimental study proposes a novel method for producing strainbursts and evaluating LMS in the laboratory.
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High-Speed Digital Photography of Vapor Cavitation in a Narrow Gap Flow
Fluids
… high-speed camera (IXCameras i-Speed 720) is used to capture bubble formation and transport inside the liquid film. The maximum data capacity of the camera is 20 Gpx/s. Hence, the resolution and frame rate have to be balanced … [Read More]
Author: P Reinke, T Beckmann, C Ahlers, J Ahlrichs
Abstract:
Digital photography of cavitation in narrow gap flows, e.g., lubrication films in journal bearings or squeeze film dampers, demands a high time-resolution and a solution to approaching the particular spatial restrictions. Typically, the lubrication film thickness is in the range of a few microns and the characteristic time for vapor bubble generation and collapse is about one millisecond, respectively. The authors have developed a Journal Bearing Model Experiment, which is designed according to similarity laws providing fully similar flow conditions to real journal flows while offering ideal access to the flow by means of optical measurement equipment. Compared with other methods, e.g., pulsed laser, electrical discharge, tube arrest, applied to produce vapor bubbles, the work on hand applies a dynamic variation of the minimum film thickness to produce suction cavitation, which proves the applicability of this novel approach to study vapor cavitation in fluid films similar to lubricant flows. The results are obtained by means of digital high-speed photography of vapor bubbles from inception to implosion triggered by the dynamic variation of the minimum film thickness of a narrow gap flow. Moreover, the results are set in relation to a general overview of cavitation processes.
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A Dual DIC System for Analysis of Dynamic Mechanical Properties of Large Sandstone under Uniaxial Compression Load
Sustainability
… The high-speed camera used in this experiment was IX Cameras i-speed 221 with image resolution of 1616 pixels × 1706 pixels, and focal length of its lens is 25 mm. The sandstone sample size was 500 mm × 500 mm. In this paper, random black … [Read More]
Author: Y Zhong, F Chen, X Gao, Z Guo, J Sun, L Zhang
Abstract:
In this paper, an experiment is carried out to acquire the dynamic mechanical properties of a simulated sandstone tunnel by a dual DIC system. The sandstone tunnel is simulated by large sandstone with a prefabricated hole in the center. The speckle size required by DIC system was evaluated, and the results showed that for large specimens a marker pen could be used to spot speckles and make sure that the diameters of speckle points in an image should be ranged from three to five pixels. The dual DIC system is composed of a low-speed camera and a high-speed camera. The low-speed camera is used to record the speckle patterns of the sandstone in one side during the whole process of compression load, and the high-speed camera is placed in the other side to record speckle patterns for 11.5 seconds before and after failure. It is realized that monitoring whole process of deformation and instantaneous failure in two directions is required. Measurement results are effectively analyzed. The results are shown as follows: At the initial stage of loading the sandstone is in an elastic stage without macroscopic cracks. With the increase in compression load the sandstone has several small stress releases and several obvious macroscopic cracks. In the final stage of loading, the distribution of normal stress and shear stress are almost the same, and cracks are subjected to the coupling effect of normal stress and shear stress. The two ends of the prefabricated hole perpendicular to the applied load direction are prone to cracks parallel to the applied load direction.
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Electric‐Field‐Driven Printed 3D Highly Ordered Microstructure with Cell Feature Size Promotes the Maturation of Engineered Cardiac Tissues
Advanced Science
… afterward, the applied voltage was turned on again and the jet behaviors in the printing process were recorded by the charge-coupled device (CCD) camera (iSpeed-221, IX Cameras, UK). Electrostatic interaction between two fibers has been proposed … [Read More]
Author: G Zhang, W Li, M Yu, H Huang, Y Wang, Z Han, K Shi
Abstract:
Engineered cardiac tissues (ECTs) derived from human induced pluripotentstem cells (hiPSCs) are viable alternatives for cardiac repair, patient-specificdisease modeling, and drug discovery. However, the immature state of ECTslimits their clinical utility. The microenvironment fabricated using 3D scaffoldscan affect cell fate, and is crucial for the maturation of ECTs. Herein, theauthors demonstrate an electric-field-driven (EFD) printed 3D highly orderedmicrostructure with cell feature size to promote the maturation of ECTs. Thesimulation and experimental results demonstrate that the EFD jet microscale3D printing overcomes the jet repulsion without any prior requirements forboth conductive and insulating substrates. Furthermore, the 3D highlyordered microstructures with a fiber diameter of 10–20μmandspacingof60–80μm have been fabricated by maintaining a vertical jet, achieving thelargest ratio of fiber diameter/spacing of 0.29. The hiPSCs-derivedcardiomyocytes formed ordered ECTs with their sarcomere growth along thefiber and developed synchronous functional ECTs inside the 3D-printedscaffold with matured calcium handling compared to the 2D coverslip.Therefore, the EFD jet 3D microscale printing process facilitates thefabrication of scaffolds providing a suitable microenvironment to promote thematuration of ECTs, thereby showing great potential for cardiac tissueengineering.
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High Performance nAl@ CuO Core-shell Particles with Improved Combustion Efficiency and the Effect of Interfacial Layers on Combustion
Journal of Alloys and Compounds
… The burning rate was measured from images taken by a high-speed camera (IX Cameras ispeed 230, Pune, Swiss). FTIR spectra were acquired on a Bruker Tensor 27 spectrometer. The molecular-weight changes in solution were determined by gel … [Read More]
Author: X Sun, S Xiu-Duo, ZF Yuan, PJ Liu, T Wang, QL Yan
Abstract:
Nanoscale aluminium (nAl)-based composites find important applications in propellant, explosives and pyrotechnics, and the improved combustion efficiency is always desirable but challenging. A core-shell nAl@CuO composite with improved combustion performance was prepared by means of a biological interfacial layer, which is inspired by the fast polymerization and strong adhesion of juglone and tannic acid in walnut peel juice. It is found that interfacial layer contains phenolic hydroxyl and amino groups, which could interact with nAl and introduce the growth of CuO crystal, respectively. Obtained nAl@CuO shows higher stability but 1.2 times more heat release than that of the mechanically mixed nAl/CuO. In addition, nAl@CuO also has 5 times faster burning rate than the mechanically mixed one. It is believed that interfacial layer hindered the direct contact of reactants but improved mass transport/diffusion efficiency in nAl@CuO. Thus, Al based composites with higher stability and superior combustion efficiency could be obtained by this interfacial layer.
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On the wave propagation modes and operation range in rotating detonation combustor with varied injection and outlet throat
Physics of Fluids
… A high-speed camera (iX Cameras: i-SPEED 7) is placed at the aft end of the RDC to capture the flame luminosity. The camera is triggered by the control system to realize a synchronous measurement. The images are captured at 30 kfps at a … [Read More]
Author: Y Wu, G Xu, C Ding, C Weng
Abstract:
The rotating detonation combustor (RDC) has received remarkable attention in the aerospace community. In this work, an experimental RDC model supplied by liquid kerosene and oxygen-enriched air is established. A parametric survey is performed with different injection throats, outlet restrictions, and equivalence ratios to analyze the rotating detonation wave propagation modes comprehensively. Dynamic pressure transducers and a high-speed camera are both employed to identify wave modes synchronously. Overall, the propagation modes are found to be highly dependent on the injection throat and combustor outlet restriction. With a large injection to annulus area ratio of 0.3, a single-wave mode is characterized when no restriction is added at the combustor outlet. Reducing the outlet area leads to a decrease in the wave frequency and a narrower steady rotating detonation propagation regime. The propagation stability of the rotating detonation is strengthened when the injection to annulus area ratio decreases to 0.2. A dual-wave collision mode and a four-wave collision mode are observed, depending on the outlet restriction. A preliminary stable RDC operation range correlated with outlet to injection throat area ratio and equivalence ratio is achieved. Furthermore, an interval value of the outlet to injection throat area ratio is proposed to reach the potential positive total pressure gain. These findings should serve as the reference for RDC configuration design in air-breathing and gas-turbine propulsion systems.
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Fundamental abrasive contact at high speeds: scratch testing in experiment and simulation
Institute of Engineering Design and Product Development
The understanding and experimentation of abrasive wear mechanisms at high speeds is still poorly investigated in literature. This is mainly due to a lack of suitable, well-instrumented test rigs for fundamental, single abrasive wear events. Standard … [Read More]
Author: M Varga, AMV Cervellón, S Leroch, SJ Eder, H Rojacz
Abstract:
The understanding and experimentation of abrasive wear mechanisms at high speeds is still poorly investigated in literature. This is mainly due to a lack of suitable, well-instrumented test rigs for fundamental, single abrasive wear events. Standard scratch tests, which are often utilized for studies of abrasion phenomena, operate in the low-speed range up to some mm/s, while applications suffering from abrasive wear often operate at speeds exceeding 1 m/s (e.g., rolling, grinding, machining). Numerical approaches, especially particle-based methods, allow the simulation of such fast deformation processes, but rely on hardening models that require a precise knowledge of material parameters. Thus, the Johnson-Cook material model was parametrized using data from high-speed compression tests of pure aluminum. A series of scratch tests with increasing depths were then simulated using the particle- based Material Point Method (MPM). Experimentation was done on a pendulum scratch test rig equipped with a Rockwell C diamond cone. By adjusting the balance point of the swing arm of ~1 m length, a velocity of 6.8 m/s was achieved at its tip as measured with a high-speed camera. Scratches of several depths were performed, and their force signals acquired. Post-test analyses comprised topography measurements and EBSD on cross-sections of the scratches to investigate the microstructural changes due to the high-speed wear event. Scratch topographies and abrasive mechanisms compared favorably between experiment and simulation for the aluminum. The extent of strain hardening was significantly reduced compared to low-speed experiments. The calibration of the high-speed force sensor was successful and now allows the investigation of new alloys and determination of material parameters under high-speed abrasive conditions.
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Functional Gradation of Aluminum Alloy by Impact of Ballistics as Severe Plastic Deformation Process
International Journal of Impact Engineering
… Impact velocities of the projectile were measured using a high-speed camera (iX-camera, model i-SPEED 726, manufactured by iX Cameras) which captures the events at a maximum of 1× 10 6 frame per second (fps). Due to the limitations of the light source … [Read More]
Author: VD Mishra, A Mishra, L Verma, G Rajesh, BC Rao
Abstract:
In the present effort, impact of bullets fired at high speeds on a stationary target was used as a high strain-rate plastic deformation method to generate Functionally Graded Materials (FGMs). The bullet-shaped Aluminum alloy Al5052 specimens impacted the UHMWPE target at different projectile velocities ranging from 100 m/s to 750 m/s, to study the effect of the impact speed. Moreover, few of the projectiles impacted along the longitudinal axis whereas the remaining projectiles impacted with an obliquity to investigate the effect of leading-edge shape. The metallography of the projectile specimens fired at 750 m/s shows grain refinement from 70 ± 3μm at the rear/ un-deformed point to 10 ± 1μm at the front/ severely deformed point which is in the impact zone. Similar but of less magnitude variations were observed at other impact speeds also. The hardness variation was 45% (70 ± 3 HV at the rear surface to 102 ± 2 HV at the front face) at 750 m/s. Moreover, least variation in hardness and grain size was observed for projectile impacted at lowest velocity tested (100 m/s). Further, functionality in hardness and grain refinement was seen in graded direction due to shape of the projectile specimens, impact velocity, and target material. Depending upon the impact angles, axisymmetric (impacted normal to the longitudinal axis) or unsymmetrical (impacted at an angle) variation of grain refinement and hardness was observed.
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Influence of the composition of separately laser-generated metal vapor on arc stability
The International Journal of Advanced Manufacturing
… The process was recorded using a high-speed camera (iX Cameras i-SPEED 220) with a recording frequency of 2000 Hz. Four samples were welded for each parameter set. The material was cleaned with ethanol before the experiments, and … [Read More]
Author: I Henze, P Woizeschke
Abstract:
The presence of metal vapor influences arc stability in both arc and hybrid welding. It is assumed that the composition of the metal vapor, and therefore the substrate material composition, plays an important role due to the different ionization energies of the material elements. In this study, a special setup is used to investigate the influence of metal vapor on the behavior of a vertically oriented arc generated between two equal electrodes by a separate laser-induced vapor generation using a transversally oriented laser beam welding process with additional support materials beside the process zone of the arc. Several aluminum alloys, steel materials, and titanium alloys are used as vapor-producing support materials.

The experiments show that the arc voltage increased under the presence of metal vapor, which implies a decrease in arc stability, leading partially to an extinction of the arc. The influence of the ionization energy is evaluated by calculating the average ionization energy for each material composition. In the case of inducing metal vapor into the arc zone, a smaller ionization energy and a lower amount of alloying elements of the support material result in a lower arc voltage increase and, therefore, higher arc stability. A higher effect on the arc stability when using elements with a smaller ionization energy for the second electron than the first argon electron is not measurable.
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Linear woodcutting of European beech: experiments and computations
Wood Science and Technology
… The experiments were also captured by an iX Cameras i-SPEED 726 high-speed monochromatic acquisition set with a frame rate of 200,000 fps. The exposure time of 13 ns required a Dedotec COOLH laser stroboscope as a light source. … [Read More]
Author: P Kubík, F Šebek, P Krejčí, M Brabec, J Tippner
Abstract:
Hardwood species are becoming increasingly important with the growing need for a diversity of forests that have recently been facing global temperature changes or conifer pests. This further leads to the growth of its potential as a building material that may originate from sustainable production. As hardwoods need to be properly processed, the article deals with the disintegration of European beech. The influence of wood grain direction, uncut chip thickness and cutting speed on the cutting force magnitudes was experimentally investigated using the device with a rotating arm of approximately 4 m in diameter. Then, the disintegration process was modelled using the finite element method in Abaqus/Explicit. The developed material model consisting of orthotropic elasticity and plasticity with rate-independent and rate-dependent tensile–compressive failure asymmetry was implemented through the user subroutine, while the crack initiation and propagation were realized using the element deletion technique. The computationally predicted average values of cutting forces and chip shapes were, except for a few tests, in good agreement with the experiments. It means that the model may be used for further investigation, such as the influence of tool wear.
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Reinforcing efficiency of nanophases with various geometric shapes on interfacial bonding in multiscale composites
Elsevier
… The failure process of specimen was captured using a high-speed camera (iX Cameras i-SPEED 726) at a recording rate of 3 × 10 5 fps. ZEISS EVO18 scanning electron microscope (SEM) was used to observe the carbon fibers coated with … [Read More]
Author: K He, H Liao, Z Liu, Y Liu, L Tang, B Yang, L Zhou
Abstract:
Introduction of nanophases into the interface between fibers and matrix in fiber-reinforced polymer composites can form multiscale composites with significantly improved interfacial bonding. The nanophases of various geometric shapes (e.g., nanotubes, nanoparticles, or nanosheets) show quite different reinforcing efficiency. To elucidate the underlying mechanisms of this discrepancy, a multiscale mechanical model is proposed to establish the relation between the geometric shape of nanophases at nano-/micro-scale and the transverse tensile strength of composites at macro-scale. Three typical carbon-based nanophases are chosen for comparison, i.e., fibrous carbon nanotubes (CNTs), granular buckminsterfullerene (BF) nanoparticles, and lamellar graphene oxide (GO) nanosheets. The study indicates that high aspect ratio nanotubes have the superior enhancing effect as individual, but the advantage could be counteracted by the relatively low distribution density in the interfacial region due to their geometric features. The two factors need to be carefully balanced to achieve the desired ultimate performance of multiscale composites.
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Effects of the electric field on the overall drop impact on a solid surface
Physical Review Fluids
… A high-speed video camera (i-SPEED 726, iX Cameras) with a frame rate up to 272251 fps is used for the bottom view to capture the fast initial contact. The resolving power is up to 1.35 μm/px and the exposure time is as short as 289 ns. [Read More]
Author: Y Tian, Z Peng, Y Liu, L Di, Z Zhan, D Ye, Y Guan
Abstract:
Depositing drops on a solid surface without entrapping bubbles is desirable for many spray coating and printing applications. Tian et al. [J. Fluid Mech. 946, A21 (2022)] reported that an electric field can be applied to eliminate air bubble entrapments for neutral drops. Herein we provide a complete physical picture of the entire process of a drop impacting onto the solid surface under an external electric field. The electrohydrodynamic behavior during the drop impact is divided into three stages: the deformation of the drop in the electric field prior to contact, the initial contact of the drop with the substrate, and the rich postcontact phenomena including spreading, receding, jetting, and fragmentation. The results show that under the increasingly stronger electric fields, the modest drop oscillation transforms into a vertically stretched spindle. As the drop approaches the substrate, the electric stress at the south pole increases rapidly, which sharpens the bottom surface into a conical shape. The cone angle is determined by both the impact velocity and the electric field strength. After the contact, the surface electric stress tends to pull the drop upward, breaking up the drop, forming several jetting modes, and reducing the maximum spreading radius. The various drop deposition modes are summarized in a phase diagram, which sheds light on identifying appropriate electric fields for high-quality drop depositions without air bubble entrapments or jettings.
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Kinematic responses of an autorotating samara to concentrated crosswind
Physics of Fluids
… A test specimen crossing through a given laser sheet induces scattered laser light that is received by a high-speed camera (i-speed 720, IX Cameras). The laser sensors were setup from 0.04 to 2.0 m above the ground, tuned to emit 3.0 mm thick … [Read More]
Author: PX Niu, MD Atkins, YY Liu, TJ Lu, T Kim
Abstract:
A single-winged maple seed (samara) is dispersed laterally by a crosswind in contrast to simply descending straight down (zero dispersion) in quiescent air. This article presents the general kinematic response of a particular type of samaras (Acer buergerianum) in stable autorotation to the disturbance of a concentrated crosswind (simulated via slot jet) with the crosswind strength varied distinctively from weak to strong. A relatively weak crosswind slower than the tip velocity of the stably autorotating samara causes only damped undulations of its descent trajectory. In contrast, we demonstrate that the samara exhibits a bi-modal response when disturbed by a relatively strong crosswind (velocity greater than samara tip velocity). The strong crosswind enables the samara either to float laterally with the crosswind or drop-out through the crosswind with the switching of its rotational direction. Regardless of crosswind strength, stable autorotation is re-established after the samara leaves the crosswind zone, albeit accompanied by large-scale undulations in its descent trajectory. More importantly, before landing, the samara regains its original terminal descent velocity achieved in quiescent air.
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Microfluidic-templated cell-laden microgels fabricated using phototriggered imine- crosslinking as injectable and adaptable granular gels for bone regeneration
Acta Biomaterialia
… For the visualization of the formation of droplets in a single-channel device, videos were taken using a high-speed camera (ispeed.221, ix Cameras, UK) and an optical microscope (ae2000, Motic, China). To visualize the top view of each layer … [Read More]
Author: C An, R Zhou, H Zhang, Y Zhang, J Liu, W Liu, B Bao
Abstract:
Injectable granular gels consisting of densely packed microgels serving as scaffolding biomaterial have recently shown great potential for applications in tissue regeneration, which allow administration via minimally invasive surgery, on-target cargo delivery, and high efficiency in nutrient/waste exchange. However, limitations such as insufficient mechanical strength, structural integrity, and uncontrollable differentiation of the encapsulated cells in the scaffolds hamper their further applications in the biomedical field. Herein, we developed a new class of granular gels via bottom-up assembly of cell-laden microgels via photo-triggered imine-crosslinking (PIC) chemistry based on the microfluidic technique. The particulate nature of the granular gels rendered them with shear-thinning and self-healing behavior, thereby functioning as an injectable and adaptable cellularized scaffold for bone tissue regeneration. Specifically, single cell-laden, monodisperse microgels composed of methacrylate- and o-nitrobenzene-functionalized hyaluronic acid and gelatin were prepared using a high-throughput microfluidic technique with a production rate up to 3.7 × 108 microgels/hr, wherein the PIC chemistry alleviated the oxygen inhibition on free-radical polymerization and facilitated enhanced fabrication accuracy, accelerated gelation rate, and improved network strength. Further in vitro and in vivo studies demonstrated that the microgels can serve as carriers to support the activity of the encapsulated mesenchymal stem cells; these cell-laden microgels can also be used as cellularized bone fillers to induce the regeneration of bone tissues as evidenced by the in vivo experiment using the rat femoral condyle defect model. In general, these results represent a significant step toward the precise fabrication of engineered tissue mimics with single-cell resolution and high cell-density and can potentially offer a powerful tool for the design and applications of a next generation of tissue engineering strategy.
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Designing Difunctional Promoters for Hypergolic Ignitions of Green Bipropellants Combining Ionic Liquids with H2O2
Industrial & Engineering Chemistry Research
… The process of the hypergolic drop test was monitored by using I-Speed 508, I-Speed 230 high-speed cameras (iX Cameras, United Kingdom) recording at 2000 frames s –1 . The hypergolic process of AMIMDCA + 5%P-Al with 90%H 2 O 2 was further … [Read More]
Author: B Wang, Z Wang, Y Jin, K Wang
Abstract:
The emergence of tetrahydroborate (BH4–)/cyanoborohydride (BH3CN–) anion-based ionic liquid fuels in combination with high test peroxide (>90%H2O2, HTP) oxidizers has accelerated the greening of bipropellants. However, most BH4– and BH3CN– anion-based ionic liquids are sensitive to water, making it difficult to store them. Here, novel difunctional promoters are designed for hypergolic ignition of BH4–/BH3CN– anion-free ionic liquids with 90%H2O2. The transition metal in anions of promoters is expected to catalyze the exothermic decomposition of H2O2, and the substituted borohydride in cations of promoters acts as the ignition source. These novel difunctional promoters show good solubility in commercially available 1-allyl-3-methylimidazolium dicyanamide and 1-butyl-3-methylimidazolium dicyanamide ionic liquid fuels, and the composite fuels exhibit high density, acceptable viscosity, and high thermostability. The addition of difunctional promoters ensures the smooth hypergolic ignition of BH4–/BH3CN– anion-free ionic liquid fuels with a minimum ignition delay time of 34.0 ms, and no apparent microexplosion and secondary combustion are observed during the ignition process. With the increase in the amount of the promoter, density specific impulses of the composite fuels improve gradually. This work provides a platform strategy for designing promoters by synergy of cations and anions and makes efforts to seek green bipropellants.
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On axisymmetric dynamic spin coating with a single drop of ethanol
Journal of Fluid Mechanics
… The dynamic spin-coating process was recorded from oblique (with an angle of 45 to the horizontal plane) and side views using two synchronized high-speed cameras (i-SPEED 220, iX-cameras) and illuminated by two light-emitting diode light … [Read More]
Author: Y Pan, Z Wang, X Zhao, W Deng, H Xias
Abstract:
We carried out experimental and numerical investigations on the axisymmetric spreading evolution of dynamic spin coating with a single drop of ethanol. The results show that the dynamic spreading process consists of two stages: inertial spreading stage and centrifugal thinning stage. These two stages are connected by a transient state in between characterized by the minimum contact line moving velocity. The Weber number determines the spreading in the first stage, similar to the case of the impact of a drop on a static substrate. The rotational Bond number has a marginal effect on the inertia spreading and the radius at the transient state. In the centrifugal thinning stage, the rotational Bond number dominates the flow while the effect of the Weber number is negligible.
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A novel braiding method and impact behaviors of 3-D braided composite three-way integrated circular tubes
Composite Structures
… We used i-SPEED 716 high-speed camera (IX Cameras Ltd, UK) to record the evolution of the dynamic deformation. The higher the temporal resolution (frame rate), the lower the spatial resolution (pixel value) [24]. To achieve a balance between … [Read More]
Author: Q Wang, X Gao, M Hu, B Gu, B Sun
Abstract:
3-D braided composite three-way circular tubes are integrated seamless connected tubes used for high strength connecting joints. We developed a novel braiding method of ‘yarn-added, yarn realigned’ to prepare three-way tubular preforms. Low-velocity impact compressions (LVIC) along axial direction were conducted to find effects of branch length and braiding layers on impact damage with drop-weight tester, high-speed camera, Micro-CT and digital image correlation (DIC). It was found that the three-way braided tubes have uniform structure both at the branches and joint regions. There is shear band induced by the weakened interface appeared after the peak load and formed within 60 μs under impact. The ultimate strength was positively correlated with the impact energy and braiding layers, while negatively correlated with the branch tube length. The test results showed that the branch length affected the position of stress concentration, and the influence of braiding layers on the LVIC behaviors is more significant than that of the branch length.
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Strain rate effect on compressive damages of thermo-oxidative aged 3D braided composites
Elsevier
Revealing mechanical behaviors of three-dimensional five-directional (3D5d) braided composites at different strain rates is a key point to its durability design and structural optimization. Here we report compressive responses, surface … [Read More]
Author: Shanghai Frontier Science Research Center for Modem Textiles
Abstract:
Revealing mechanical behaviors of three-dimensional five-directional (3D5d) braided composites at different strain rates is a key point to its durability design and structural optimization. Here we report compressive responses, surface deformations and failure behaviors of aged 3D5d braided composites under different strain rates with digital image correlation (DIC) technique, X-ray micro-computed (micro-CT) tomography and finite element analysis (FEA). The compressive rigidity, peak stress, maximum strain, energy absorption, surface strain and damages exhibit strain rate strengthening effects and ageing weakening behaviors. The strain concentration zone transfers from X-shaped to transverse V-shaped at the square cross-section with the increasing of strain rate. Moreover, ageing effect does not change the internal shear mode, while it changes the near-surface crack distribution along axial direction and crack propagation path under impact loading. The failure modes show strain rate correlation. The FEA results reveal the failure mechanisms of the aged 3D5d braided composites under different strain rates.
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Anisotropic degradation mechanism on low-velocity impact of 3D braided composites after thermo-oxidative ageing
Elsevier
… The high-speed camera (i-Speed 716, IX Cameras Ltd, UK) was used to record damage and failure evolution processes with a 10,000 frames per second and 800,000 pixels. In addition, the optical microscope and SEM were used to observe … [Read More]
Author: Yuanyuan Wu, Jinhui Guo, Limeng Xun, Baozhong Sun, Bohong Gu
Abstract:
Anisotropic mechanical behaviors are the most prominent feature of 3D braided composites compared with homogeneous materials. This study reports anisotropic low-velocity impact behaviors of 3D braided carbon fiber/epoxy composites along in-plane (IP) and out-of-plane (OP) directions after thermo-oxidative ageing. The stress–strain responses, local strain and damage evolution were obtained. The stress distribution of each yarn and the interface damage propagation were analyzed with numerical analysis method. The retention rate of peak stress of 94.4% and elastic modulus of 91.45% along OP direction are greater than those along IP direction, which are 76.21% and 71.27% respectively. It reveals that the OP direction loading has a better performance on resistance ageing degradation than that in IP loading, and the stiffness degradation is more sensitive. There are X-shape shear damages along OP direction, and interior damages in surrounding area and yarn path along IP direction. Furthermore, the tight braided structure contributed to resisting degradation of mechanical properties along IP direction.
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Machine Learning to Predict the Interfacial Behavior of Pesticide Droplets on Hydrophobic Surfaces for Minimizing Environmental Risk
ACS Sustainable Chem. Eng.
… reticulata Blanco leaf surface was recorded at 4000 fps with i-SPEED 220 high-speed cameras (iX cameras). The retention of pesticide liquids was evaluated by the spraying method. Leaves were placed on a homemade 45 slope for spraying to … [Read More]
Author: Ridan Song, Yanling Wu, Zhenping Bao, Yuxia Gao
Abstract:
Achieving accurate and efficient target deposition of pesticide droplets is the principal factor in minimizing environmental risk. For hydrophobic surfaces, adding tank-mix adjuvants containing surfactants to modulate interfacial behavior is warranted, which lacks common laws to guide practical applications directly. Machine learning is developing rapidly and makes many data-based decisions in various industrial processes. Hence, according to machine learning-based analysis of fundamental physical quantities, proposing quantitative sustainability metrics to improve interface behavior is essential. Comparing the interfacial behavior of five adjuvants, the common denominator is that droplets in the Wenzel state with higher adhesion tension and lower contact angles can generate the pinning force that causes energy dissipation, reduces pesticide losses, and weakens environmental pollution. Simultaneously, the interfacial behavior of pesticide droplets including adjuvants on citrus leaves is verified, while the phytotoxicity experiment under high temperature and the laboratory bioassay are carried out. The results show that the eco-friendly alkyl polyglycoside (APG) as the glycosidic surfactant has nontarget biosafety and better mite control, which can be exploited as a commercial tank-mix adjuvant for promotion. This study provides a new insight into guiding adjuvants added to pesticides on account of quantitative sustainability metrics, which has important implications for food safety and agricultural green development.
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Experimental results and mathematical formulation of non-spinning stone-skipping process
Scientific Reports
… Our experimental setup contains a throwing machine, four separated water tanks aligned at suitable distances away from the throwing machine, a high-speed camera (Olympus ix Cameras, 2000fps in 1024 × 768 resolution with lens of Nikon 24–85 … [Read More]
Author: Hsuan-Wei Tsai, Hsieh-Chen Tsai, Wen-Fang Wu & Chun-Liang Lai
Abstract:
Following a previously published paper in studying stone-skipping processes, detailed experimental figures are revealed in this paper. A mathematical model is also provided to explain the observed phenomena and measured data. The model separates the skipping process into several stages. It emphasizes, in particular, a hitting stage and a sliding stage, and also includes capillary-gravity wave resistance in its formulation. During these two stages, scale analysis is applied first to evaluate the relative importance among various forces acting on the stone. After reasonable simplification, a numerical algorithm is established to depict motion of the stone starting from its first hit of water to final sink. The total number of skips under specified initial throwing conditions can be predicted accordingly. The agreement between the analytical and experimental results indicates the applicability of the proposed model.
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3D-Printed Parahydrophobic Functional Textile with a Hierarchical Nanomicroscale Structure
American Chemical Society
Functional textiles with superhydrophobicity and high adhesion to water, called parahydrophobic, are attracting increasing attention from industry and academia. The hierarchical (micronanoscale) surface patterns in nature provide an excellent … [Read More]
Author: ACS Nano
Abstract:
Functional textiles with superhydrophobicity and high adhesion to water, called parahydrophobic, are attracting increasing attention from industry and academia. The hierarchical (micronanoscale) surface patterns in nature provide an excellent reference for the manufacture of parahydrophobic functional textiles. However, the replication of the complex parahydrophobic micronanostructures in nature exceeds the ability of traditional manufacturing strategies, which makes it difficult to accurately manufacture controllable nanostructures on yarn and textiles. Herein, a two-photon femtosecond laser direct writing strategy with nanoscale process capability was utilized to accurately construct the functional parahydrophobic yarn with a diameter of 900 μm. Inspired by rose petals, the parahydrophobic yarn is composed of a hollow round tube, regularly arranged micropapillae (the diameter is 109 μm), and nanofolds (the distance is 800 nm) on papillae. The bionic yarn exhibited a superior parahydrophobic behavior, where the liquid droplet not only was firmly adhered to the bionic yarn at an inverted angle (180°) but also presented as spherical on the yarn (the maximum water contact angle is 159°). The fabric woven by the bionic yarn also exhibited liquid droplet-catching ability even when tilted vertically or turned upside down. Based on the excellent parahydrophobic function of bionic yarn, we demonstrated a glove that has very wide application potential in the fields of water droplet-based transportation, manipulation, microreactors, microextractors, etc.
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The mechanism of stab resistance of carbon fiber reinforced polymer
Elsevier
… Moreover, an i-SPEED 716 high-speed camera (IX Cameras Ltd, UK) with 10000 frames per second was used to record the local changes during the impact process. As the surface of CFRP is a smooth epoxy resin, to avoid reflection during … [Read More]
Author: Key Laboratory of Textile Science & Technology, Donghua University, Shanghai
Abstract:
In this paper, the puncture resistance of carbon fiber reinforced polymer (CFRP) with different thicknesses under various puncture energy was studied by in-situ observation. The puncture failure process of CFRP was analyzed using a high-speed camera and thin-film pressure sensor in terms of damage image and local pressure change. The experimental results show that the puncture threshold load (PTL) representing material penetration is usually located at the initial loss position of material stiffness. The penetration load can be divided into linear growth and delamination failure zones. Image localization was used to mark the puncture feature points on the puncture force–displacement curve to help characterize the puncture failure process. The theoretical equations of puncture force and displacement before material penetration are proposed and verified by introducing yield stress and friction force, and the correlation between the material thickness and the puncture resistance was proved. In addition, the failure modes and fracture morphology of CFRP after puncture are analyzed and summarized. After puncture impact, fiber fracture, pull out and slip deformation under the action of tensile force and cutting force, and matrix fracture and peel damage. The increase of impact energy leads to a broader range of impact damage but does not change the failure modes.
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Mechanism investigation for the influence of laser power on droplet transfer behaviors in laser-MIG hybrid welding
Elsevier
The stability of droplet transfer plays an important role in the weld formation and spatters suppression during the laser-MIG hybrid welding. However, a debate exists on whether increased laser power improves or suppresses the droplet transfer. In … [Read More]
Author: State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology
Abstract:
The stability of droplet transfer plays an important role in the weld formation and spatters suppression during the laser-MIG hybrid welding. However, a debate exists on whether increased laser power improves or suppresses the droplet transfer. In this study, the role of laser heat source was investigated in a wide range of laser power. The transfer frequency was firstly improved by increasing laser power, and then it was decreased once the laser power proceeded a critical value. The variation of droplet transfer frequency was determined by the competition between electromagnetic force and metal vapor reaction force. With increasing laser power, the arc conductivity was better and the arc current was improved, leading to increase of the electromagnetic force. As a result, the droplet transfer was promoted and the deposition rate of wire metal was increased. However, rapid increase of metal vapor reaction force was obtained when the laser power exceeded the critical value, producing a greater resistance on droplet transfer. Furthermore, the critical value of laser power was mainly determined by the characteristics of laser source, materials, laser focusing distance and laser-arc distance. This work will provide more guidance on matching processing parameters of the laser-MIG hybrid welding to improve weld formation and suppress spatters by stabilizing the droplet transfer.
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A survival model of thoracic contusion spinal cord injury in the domestic pig
doi.org
… nonlinearity/hysteresis 0.56 N), and impactor displacement via a magnetic linear position sensors (BTL6-G500-M0102-PF-S115, nonlinearity ±200 μm, accuracy ± 5 μm, Balluff, Neuhausen, Germany) attached to the rail; high speed video (iSpeed TR … [Read More]
Author: Ms. Christine Gayen , Ms. Madeleine Amy Bessen , Mr. Ryan Dorrian
Abstract:
Spinal cord injury (SCI) frequently results in motor, sensory and autonomic dysfunction for which there is currently no cure. Recent preclinical and clinical research has led to promising advances in treatment; however, therapeutics indicating promise in rodents have not translated successfully in human trials, likely due, in part, to gross anatomical and physiological differences between the species. Therefore, large animal models of SCI may facilitate the study of secondary injury processes that are influenced by scale, and assist the translation of potential therapeutic interventions. The aim of this study was to characterize two severities of thoracic contusion SCI in female domestic pigs, measuring motor function and spinal cord lesion characteristics, over two weeks post-SCI. A custom instrumented weight drop injury device was used to release a 50 g impactor from 10 cm (n=3) or 20 cm (n=7) onto the exposed dura, to induce a contusion at the T10 thoracic spinal level. Hind limb motor function was assessed at 8 and 13 days post-SCI using a 10-point scale. Volume and extent of lesion-associated signal hyperintensity in T2-weighted magnetic resonance (MR) images was assessed at 3, 7 and 14 days post-injury. Animals were transcardially perfused at 14 days post-SCI and spinal cord tissue was harvested for histological analysis. Bowel function was retained in all animals and transient urinary retention occurred in two animals after catheter removal. All animals displayed hind limb motor deficits. Animals in the 10 cm group demonstrated some stepping and weight bearing and scored a median 2-3 points higher on the 10-point motor function scale at 8 and 13 days post-SCI, than the 20 cm group. Histological lesion volume was 20 % greater, and 30 % less white matter was spared, in the 20 cm group than in the 10 cm group. The MR signal hyperintensity in the 20 cm injury group had a median cranial-caudal extent approximately 1.5 times greater than the 10 cm injury group at all three time points, and median volumes 1.8, 2.5 and 4.5 times greater at day 3, 7 and 14 post-injury, respectively. Regional differences in axonal injury were observed between groups, with amyloid precursor protein immunoreactivity greatest in the 20 cm group in spinal cord sections adjacent the injury epicenter. This study demonstrated graded injuries in a domestic pig strain, with outcome measures comparable to miniature pig models of contusion SCI. The model provides a vehicle for the study of SCI and potential treatments, particularly where miniature pig strains are not available and/or where small animal models are not appropriate for the research question.
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Memristive Fast-Canny Operation for Edge Detection
IEEE
Memristor-based in-memory computing paradigm is a promising path for edge detection in image preprocessing on end devices that reduces the computational pressure on data centers. However, the implementation of the well-performing … [Read More]
Author: J Tian, HJ Zhou, H Bao, J Chen, XD Huang, JC Li
Abstract:
Memristor-based in- memory computing paradigm is a promising path for edge detection in image preprocessing on end devices that reduces the computational pressure on data centers. However, the implementation of the well-performing Canny operator for edge detection faces challenges in terms of computational time and area overhead when mapped to memristor arrays. In this work, we proposed an efficient memristive one-step implementation of a fast-Canny operator. Exploiting the associative property of multiplication, the conventional Canny operator consisting of Gaussian and Sobel operators is converted into a fast-Canny operator and mapped to an array of nine parallel memristors. Then, the output currents are the final pixels of the edge image. To verify the feasibility of the method, successful edge detection with high accuracy (OIS = 0.73) is achieved in device-aware simulation under device variation (<50%) and image noise ( σ = 6%). Additionally, the implementation of the fast-Canny operator on memristor arrays can reduce the processing time by half and save the area of buffer compared to the prior two-convolution Canny operation. Our work suggests that the memristive fast-Canny operator could be a promising and efficient hardware solution for edge detection at the network edge.
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Surface properties of Tetranychus urticae Koch (Acari: Tetranychidae) and the effect of their infestation on the surface properties of kidney bean (Phaseolus vulgaris L.) hosts
Wiley Online Library
… The impact behavior of the 0.033 wt % acaricide droplets on kidney leaves was recorded using a high-speed camera, i-SPEED 220 (iX Cameras, UK), and further analyzed using the i-… [Read More]
Author: Z Lu, Y Gao, C Zhang, Z Bao, W Wang
Abstract:
Background
The wettability of the target surfaces affects the wetting and deposition of pesticides on them. The properties of leaf surfaces change after infestation by Tetranychus urticae Koch. Studying the surface wettability of T. urticae and the changes in leaf wettability after infestation is important to guide the use of acaricides.

Results
The body surface of T. urticae is an ellipsoidal crown covered with dense cuticle striations and hairs arranged in different directions, which makes the surface of T. urticae rough and hydrophobic. The abaxial surfaces of the leaves are rougher and more hydrophobic than the adaxial surfaces. After infestation by T. urticae, the faded spots were sunken on the adaxial surface and raised on the abaxial surface, where they had formed new wide peaks and valleys. The adaxial surface became obviously rougher and more hydrophobic, while the roughness of the abaxial surface became slightly larger, and the change in hydrophobicity was not obvious. The contact angles of the studied commercial acaricide on these surfaces were greater than 65° and were affected by the infestation. Reducing the surface tension can allow for better wetting of these surfaces and eliminate changes in leaf wettability.
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Microstructure and Mechanical Properties of Low-Carbon High-Strength Steel Fabricated by Wire and Arc Additive Manufacturing
mdpi.com
Wire and arc additive manufacturing (WAAM) is a novel technique for fabricating large and complex components applied in the manufacturing industry. In this study, a low-carbon high-… [Read More]
Author: L Sun, F Jiang, R Huang, D Yuan, C Guo, J Wang
Abstract:
Wire and arc additive manufacturing (WAAM) is a novel technique for fabricating large and complex components applied in the manufacturing industry. In this study, a low-carbon high-strength steel component deposited by WAAM for use in ship building was obtained. Its microstructure and mechanical properties as well as fracture mechanisms were investigated. The results showed that the microstructure consisted of an equiaxed zone, columnar zone, and inter-layer zone, while the phases formed in different parts of the deposited component were different due to various thermal cycles and cooling rates. The microhardness of the bottom and top varied from 290 HV to 260 HV, caused by temperature gradients and an inhomogeneous microstructure. Additionally, the tensile properties in transversal and longitudinal orientations show anisotropy characteristics, which was further investigated using a digital image correlation (DIC) method. This experimental fact indicated that the longitudinal tensile property has an inferior performance and tends to cause stress concentrations in the inter-layer areas due to the inclusion of more inter-layer zones. Furthermore, electron backscattered diffraction (EBSD) was applied to analyze the difference in Taylor factor between the inter-layer area and deposited area. The standard deviation of the Taylor factor in the inter-layer area was determined to be 0.907, which was larger than that in the deposited area (0.865), indicating nonuniform deformation and local stress concentration occurred in inter-layer area. Finally, as observed from the fracture morphology on the fractured surface of the sample, anisotropy was also approved by the comparison of the transversal and longitudinal tensile specimens
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Spacing effect on pool boiling performance of three triangular pitched and vertically oriented tubes
Elsevier
… All measurements are performed with a DAQ Rigol M300 connected together with an IX-cameras i-SPEED 210 high speed camera at 800 fps (5) to a common computer. The four … [Read More]
Author: A Nikulin, JL Dauvergne, A Ortuondo
Abstract:
There is a scarcity of available data on boiling process in vertically oriented tube bundles in accessible sources. Lack of systematic studies is limiting further expansion of this highly efficient process of heat transfer into heat recovery field. In this paper boiling process of three triangular pitched and vertically oriented tubes has been studied in ethanol at 78 °C. The main focus of this work was to study the effect of tube spacings on heat transfer coefficient (HTC) and bubbles behavior (bubble departure diameter in particular) that were visualised with the help of a high speed camera. Experiments were performed in a wide range of tube spacings (from 10.75 to 0.25 mm) and heat flux densities (from 3 to 70 kW/m2).
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Effect of thermo-oxidative ageing on the thermo-mechanical responses of 3D braided carbon fiber/epoxy composites during high-speed impact
Taylor & Francis
… A high-speed camera (ispeed 716, iX Cameras Inc.) at 10 μs per frame was employed to visualize the deformation and failure of 3D braided composites. All the specimens were cut into … [Read More]
Author: S Liu, X Wu, S Liu, B Sun, B Gu - The Journal of The Textile
Abstract:
By developing a thermo-mechanical coupled model, we quantitatively analyzed the effect of thermo-oxidative ageing on the temperature, thermal strain and thermal stress histories of braided composites during high-speed impact. We also considered temperature dependence of elastic modulus during impact in this model. The proposed model was first applied to the unaged composites, then the results were compared to the impact responses captured by the split Hopkinson bar and the high-speed camera. The comparisons of the experimental and numerical results show that the proposed model could capture the adiabatic temperature rise, stress-strain responses and failure process of braided composites during high-speed impact. The validated model was subsequently employed to thermo-oxidative aged composites. Results show that the temperature rise, thermal strain and thermal stress all depend on the mechanical properties of resin, and they decreased with the increase of ageing temperature since the performance of resin is compromised by thermo-oxidation ageing. The change of resin performance after ageing leads to the change in the temperature rise during impact, so the stiffness of composites will decrease in varying degrees after ageing.
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Erosion Mechanisms of Debris Flow on the Sediment Bed
Wiley Online Library
… A high-speed camera (i-SPEED7, iX Cameras, sample frequency 179 Hz) in the cross-stream direction was used to observe the erosion process. A 3D laser scanner (ScanStation P40, … [Read More]
Author: H Zheng, Z Shi, S Yu, X Fan… - Water Resources Research
Abstract:
Debris flows are common geological hazards in mountainous regions worldwide. The scale of debris flows can be significantly enhanced by basal erosion and bank collapse in the transportation process, resulting in an increase in casualties and property losses. However, the mechanisms of this growth are largely unclear. Here, we conduct a series of experiments to investigate the erosion of two different bed sediments (coarse-grained and widely graded) by released flows with three different densities and two different volumes. The erosion mechanisms of bed sediments are revealed by comparing detailed sensor data for flow level, pore pressure and total normal stress. A flow nose develops on the coarse-grained bed sediment, resulting in a high flow depth and low velocity, while a tabular flow develops on the widely graded bed sediment, leading to a low flow depth and high velocity. The mean erosion rates of the coarse-grained bed sediment are generally higher than those of the widely graded bed sediment due to significant pore pressure developed in coarse-grained bed sediment. The feedback effect of bed sediment on the erosion process strongly influences the flow depth and velocity, which in turn affects the mean erosion rate of bed sediment. The interaction between the overlying flow and sediment bed controls the erosion pattern: coarse-grained bed sediment is eroded by a layer of mass movement whereas widely graded bed sediment is progressively scoured. The interaction between debris flow and bed sediment during erosion is principally attributed to pore-pressure transmission.
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Metal transfer behaviour of CMT-based step-over deposition in fabricating slant features
Elsevier
… For the imaging system, the metal transfer behaviour was recorded using a high-speed digital camera (i-speed 7-716 high-speed camera, iX Cameras company) with a … [Read More]
Author: Z Yan, Y Zhao, F Jiang, S Chen, F Li, W Cheng
Abstract:
The metal transfer behaviour of slant feature of thin-walls fabricated by cold metal transfer (CMT) process in step-over deposition mode was observed by high speed camera. A slanted short circuiting transfer (SSCT) was generated during deposition and then analysed by asymmetrical magnetic and force model, complicating metal transfer behaviour in comparison with conventional deposition process. The SSCT allowed the droplet to transfer obliquely into the molten pool on previous layer, owing to the pushing force generated by unevenly distributed electromagnetic field in asymmetrical deposition model. The surface tension between wire and liquid metal is the most important force that retarded droplet transfer. The retraction force and electromagnetic force are the main forces to promote droplet transition. The positive forces that promote droplet transfer process can be arranged as Fem > Fr > Fg. The wall width was mainly affected by wire feed speed and the inclined angle can be significantly increased with increasing step-over distance.
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Near-fiber nanomechanical mapping and impact failure mechanism of 3D braided composites subjected to thermo-oxidative environment
Elsevier
… Moreover, we used i-SPEED 716 high-speed camera (IX Cameras Ltd, UK) with 10000 frames per second to record the local changes during impact process, including crack initiation, … [Read More]
Author: Y Wu, W Cao, J Guo, L Xun, B Sun, B Gu
Abstract:
The macroscopic mechanical behaviors generally correlate with nanomechanical properties, especially elastic modulus. This paper presents the thermo-oxidative ageing effects on nanoscale elastic modulus and impact failure mechanism of 3D braided composites at micro and macro levels using PeakForce Quantitative Nano-Mechanics (PF-QNM) and digital image correlation (DIC) technologies. The values of nanoscale elastic modulus of near-fiber resin pocket were about three times than that of global modulus in neat resin under low-velocity impact compression (LVIC) loading. However, the modulus retention rates were consistent which was ∼88% after ageing for 16 days at 180 °C. The decline of them has provided a direct evidence for resin degradation after ageing. In addition, the in-plane impact failure mechanism of braided composites mainly contained five modes, i.e., matrix cracking, interface cracking, matrix fracture and peeling off, fiber buckling and slipping, and fiber breakage. Thermo-oxidative ageing only changed the crack propagation path but not the damage modes.
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New Insights into the Role of Laser Power in the Droplet Transfer of Laser-Mig Hybrid Welding
SSRN
… The droplet transfer was monitored by a high-speed camera (i-SPEED 221, iX Cameras) with an ultraviolet (UV) filter of 550 nm and optical filter of ND8 lenses. The sampling frequency … [Read More]
Author: F Liu, B Yang, H Wang, C Tan, G Wang, B Chen
Abstract:
The stability of droplet transfer plays an important role in the weld formation and spatters suppression during the laser-MIG hybrid welding. However, a debate exists on whether increased laser power improves or suppresses the droplet transfer. In this study, the role of laser heat source was investigated in a wide range of laser power. The droplet transfer was firstly improved by increasing laser power, and then it was suppressed once the laser power proceeded a critical value. The variation of droplet transfer frequency was determined by the competition between electromagnetic force and metal vapor reaction force. With increasing laser power, the arc conductivity was better and the arc current was improved, leading to increase of the electromagnetic force. As a result, the droplet transfer was promoted and the deposition rate of wire metal was increased. However, rapid increase of metal vapor reaction force was obtained when the laser power exceeded the critical value, producing a greater resistance on droplet transfer. Furthermore, the critical value of laser power was mainly determined by the characteristics of laser source, materials and laser-arc distance. This work will provide more guidance on matching processing parameters of the laser-MIG hybrid welding to improve weld formation and suppress spatters by stabilizing the droplet transfer.
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Modeling and Experimental Analysis of Shear-Slitting of AA6111-T4 Aluminum Alloy Sheet
mdpi.com
This work presents experimental studies with numerical modeling, aiming at the development of guidelines for shaping aluminum alloy AA6111-T4, t = 1.5 mm thick, with the use of a … [Read More]
Author: Ł Bohdal, L Kukiełka, S Legutko, R Patyk
Abstract:
This work presents experimental studies with numerical modeling, aiming at the development of guidelines for shaping aluminum alloy AA6111-T4, t = 1.5 mm thick, with the use of a shear-slitting operation. During the experimental tests, parametric analyses were conducted for the selected material thickness. For the purposes of the material deformation’s analysis, a vision system based on the digital image correlation (DiC) method was used. Numerical models were developed with the use of finite element analysis (FEA) and the mesh-free method: smoothed particle hydrodynamics (SPH), which were used to analyze the residual stress and strain in the cutting zone at different process conditions. The results indicate a significant effect of the horizontal clearance between knives on the width of the deformation zone on sheet cut edge. Together with the clearance value increase, the deformation zone increases. The highest burrs on the cut edge were obtained, when the slitting speed was set to v = 17 m/min, and clearance to hc = 6%t. A strong influence was observed of the horizontal clearance value at high slitting speeds on burr unshapeliness. The most favorable conditions were obtained for v = 32 m/min, hc = 0.062 mm, and rake angle of upper knife for α = 30°. For this configuration, a smooth sheared edge with minimal burr height was obtained.
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Development of a novel device for analysis of high-speed cutting processes considering the influence of dynamic factors
The International Journal of Advanced Manufacturing Technology
Previous methods for the investigation of high-speed cutting processes for bio-based materials failed since essential principles for the investigation of dynamic processes have not been … [Read More]
Author: O Dvoracek, D Lechowicz, T Krenke, B Möseler
Abstract:
Previous methods for the investigation of high-speed cutting processes for bio-based materials failed since essential principles for the investigation of dynamic processes have not been taken into account. The novel self-developed device, based on the principle of a rotor arm, enables a detailed analysis of cutting processes. The rotor arm has a diameter of 4 m, enabling precise analysis of cutting processes. The device enables analysis of speeds up to 100 m/s of the more or less linear cutting process. Stiffness of the set-up, the natural frequency of the system, and a series of cuts per test may cause a convoluted signal demanding dynamic calibration of the measurement chain. The newly developed device enables the conduction of single cuts per examination at relatively high speed. Thus, the influence of the previous cut is eliminated. Previous research has not provided a possibility to study linear cutting processes at the mentioned velocity. The accuracy of the device was proven within various examinations. A correction based on real chip thickness measurement was applied. Finally cutting of beech, using a wide set of parameters, was examined. The cutting forces of the beech sample increased linearly with chip thickness. Nevertheless, the influence of velocity showed non-linear progression. The smallest force was observed at 20 m/s. From this cutting speed, force always increased when velocity was changed.
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Bioinspired Functional Structures for Lubricant Control at Surfaces and Interfaces: Wedged-Groove with Oriented Capillary Patterns
ACS Publications
… The macroscope manipulation process was captured via a digital camera (D750, Nikon, Japan) and a high-speed camera (i-SPEED 726R, iX Cameras, UK), and the … [Read More]
Author: S Chen, Q Dai, X Yang, J Liu, W Huang… - ACS Applied Materials
Abstract:
In this work, a design concept of bioinspired functional surfaces is proposed for lubricant control at surfaces and interfaces subjected to external thermal gradients. Inspired by the conical structures of cactus and the motion configuration of Centipedes, a bioinspired surface of wedged-groove with an oriented capillary pattern is constructed. The effect of geometrical parameters on the directional lubricant manipulation capacity and sliding anisotropy is discussed. It is found that by regulating the orientation of the capillary pattern, a controllable lubricant self-transport capacity can be achieved for varying conditions from surfaces to interfaces, with or without thermal gradients. The lubricant self-transport process is captured, and the mechanism is revealed. The design philosophy of the proposed bioinspired functional surface is believed to have potential applications for lubricant control in modern machinery and complex liquid control in lab-on-a-chip and microfluidics devices.
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Collisional interaction process between a bubble and particles with different hydrophobicity
Elsevier
… These messages were obtained using an image digital analysis program (ProAnalyst, iX Cameras Inc., UK). The original images with the RGB color format were converted to the … [Read More]
Author: H Wang, Y Liang, D Li, R Chen, X Yan… - Separation and Purification
Abstract:
The collisional interaction process between bubbles and particles is considered to play an important role in flotation. This paper aims to investigate the effect of particle hydrophobicity on the bubble-particle collision and subsequent interaction process. Four types of bubble-particle interaction behaviors were observed, namely the non-collision, the collision but without attachment, the attachment with jump-in after collision, and the attachment without jump-in after collision. The ‘jump-in’ event was interpreted as the rupture of the water film, providing the formation and growth of a ‘three-phase contact line’ (TPCL). The mildly hydrophobic particle could attach to the bubble surface without the rupture of the water film, whereas the highly hydrophobic particle had the higher collision and attachment probability. The significant effect of particle hydrophobicity was found in the observed particle trajectories and velocities. The distance between the bubble and the particle of weakly hydrophobicity and mildly hydrophobicity remained almost constant in the particle sliding process on the bubble surface. However, the highly hydrophobic particle was observed to jump in instantaneously after a short interaction time. Influenced by hydrodynamic drag, the maximum sliding velocity of any particles near the bubble’s equatorial plane was higher than the particle terminal velocity, and highly hydrophobic particle had a higher difference. The analysis of the individual force components of particle provides valuable insights into the kinematic properties of particle as it slides. The hydrodynamic drag coefficient decreased with an increase in the particle contact angle, implying the highly hydrophobic particle had a smaller hydrodynamic drag. Additionally, the reaction force was introduced for the first time to satisfy the radial force balance relationship, and explanations were proposed in terms of its source.
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Regulating droplet impact and wetting behaviors on hydrophobic leaves using a nonionic surfactant
Elsevier
… The droplet impact behavior on hydrophobic leaves was recorded at 4,011 frames per second with an i-SPEED 220 high-speed camera (iX Cameras Inc., UK). The droplet diameter was … [Read More]
Author: R Zhao, M Yu, Z Sun, L Li, X Guo, Y Xu, X Wu - Department of Applied Chemistry
Abstract:
Droplet rebound from hydrophobic leaves is a major factor influencing pesticide utilization. The use of a surfactant is a major strategy to reduce droplet rebound, promoting pesticide deposition on hydrophobic agricultural plant leaves. However, most surfactants known to regulate droplet rebound are either anionic or cationic. In this study, ethoxylated propoxylated 2-ethyl-1-haxanol (EH 6) was identified as a nonionic surfactant that inhibits droplet rebound while promoting the complete spreading of the droplet on hydrophobic leaves. Compared with the widely reported nonionic surfactant Tween 20, EH 6 performs better at concentrations above 0.3%. This phenomenon can be attributed to the rapid migration of EH 6 from the bulk to the newly generated interface, significantly reducing the surface tension. We introduce a simple and effective strategy that can be used to enhance droplet deposition on hydrophobic plant surfaces, which may offer future economic and environmental benefits.
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Dynamic formation characteristics and mechanism of hybrid laser arc welding surface layer by Ni-based filler metal based on rotating laser induction
Elsevier
… The molten pool was observed by the I-Speed 7 high-speed camera (iX Cameras, UK). The sampling frequency is 10 000 frames/s. A semiconductor laser is used as the background … [Read More]
Author: X Liu, Y Guo, W Zhang, D Wu, R Huang, M Yang… - Journal of Materials
Abstract:
This study used a nickel-based filler metal to fabricate a surfacing layer on a low-carbon steel substrate by a hybrid welding process with a rotating laser and arc. The surfacing layer's weld formation was studied using optical microscopic observation (OM). The microstructure of the layers was studied by using the scanning electron microscope (SEM), energy dispersive spectrum (EDS) and X-ray diffraction (XRD). The arc, metal transfer, molten pool flow behaviors, and U–I characteristics during hybrid laser arc welding (HLAW) were analyzed using the arc analyzer and high-speed camera. The results show that a rotating laser improves the weld formation of gas metal arc welding (GMAW). The microstructure of the two surfacing layers consists of dendritic γ phase and a small amount of Laves and NbC phases. The high dilution rate of the HLAW surfacing layer results in relatively more Laves and fewer NbC phases. The arc length of HLAW is dynamically deflected with the rotation of the laser, which expands the arc action and heating area of the molten pool. The droplet transfer mode changed from globular transfer dominant in GMAW to the projected transfer dominant in HLAW. The location where the droplet transfer into the molten pool is dynamic changed, forming a multi-point impact on the molten pool. Combined with the deflected arc with the laser rotating laser, the HLAW has a broad and deep molten pool. Understanding the metal transfer behavior of Ni-based alloys in rotating laser-induced arc hybrid surfacing is of great significance for improving surfacing forming.
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Improvement of process repeatability and resolution in abrasive air jet machining via viscous slurry entrainment
Journal of Manufacturing Processes
… The changes of powder mass flow rate captured by the high-speed camera (I-SPEED 716, IX cameras, UK) in system I due to the decreasing powder height and in system due to the vibrating feeder. These pictures were provided by Zhang et al. [17]. … [Read More]
Author: Y Hu, Q Dai, W Huang, X Wang
Abstract:
The unsteady powder mass flowrate of the available feeding systems and the bad control of the areas being eroded have been often noticed in the abrasive air jet machining process. In addition to the delivery of dry powder, the powder can be evenly mixed with liquid to form a slurry, and then sent to the mixing chamber of an air jet machine; i.e., multiphase jet machining (MJM) was proposed in this paper. The method whereby using the viscous water to suspend the abrasives was found to enhance the stability of powder mass flowrate, thereby decreasing the fluctuation in the machining depth. Whereafter, five types of liquid-based slurries were prepared and their effects on the jet erosion zone were investigated. It was found that the control of the erosion zone was improved to varying degrees when the abrasives were transported into the air jet by viscous liquid as the carrier fluid due to the two roles: reducing the occurrence of third and/or second particle impacts; inducing a viscous boundary layer that could reduce the negative effect of the divergence of jet beam and particle rebounding. In particular, the use of an oil-based slurry could completely eliminate the unwanted frosted zone around the machined features. CFD simulations were used to understand the mechanisms causing these effects. Overall, it is shown that the abrasive air jets can be designed to have a good resolution, so it is feasible to mill or polish surface without the need for a mask to define the edges.
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Preparation and Properties of Nitrocellulose/Viton Based Nano Energetic by Direct Writing
International Conference
… The i-SPEED 726 high-speed camera (iX Cameras, UK) was used to record the combustion process in air, with a shutter speed of 5000 fps and a focal length of 50 mm. The flame temperature is measured by a 50 mm METIS H3 high-speed infrared … [Read More]
Author: Y Jiao, S Li, S Ding, D Yang, C Bai, J Liu, Y Luo, G Li
Abstract:
Direct writing technology is a promising approach for the preparation of reactive materials. The polymer binder provides a mechanically stable, processable and shapeable energetic structure for composites. Herein, Direct-writing energetic inks consisting of nitrocellulose (NC) and VitonF2311 as well as nanothermite were developed. Firstly, Fourier transform infrared spectroscopy (FT-IR) was used to analyze the intermolecular hydrogen bonds in the hybrid polymers, and the stability of the network structure was characterized by rheometer, and the mechanical properties of binders were also tested. The results show the best binder formulation is 20 wt% NC and 80 wt% F2311. The elongation at break of the binder is 600.94%, and the elastic modulus is 8.29 MPa. NC provides high tensile strength for the hybrid binder; F2311 provides high fracture tensile rate for the hybrid binder, and as a high-energy initiator, pre-ignition reaction occurs when the temperature reaches 350 °C. Then the as-prepared inks not only has excellent rheological properties so that it can be loaded with 90 wt% nanothermite, but also possess a homodisperse for components and good combustion performance. The average flame temperature is about 2400 K at atmospheric pressure.
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Large-scale single-cell encapsulation in microgels through metastable droplet-templating combined with microfluidic-integration
Biofabrication
… To determine the stability of droplets formed with different concentrations of PFAs, we use a high-speed camera (ispeed.221, iX Cameras, UK) and an optical microscope (ae2000, Motic, China) to observe the merging behavior of droplets in a … [Read More]
Author: H Zhang, L Zhang, C An, Y Zhang, F Shao, Y Gao
Abstract:
Current techniques for the generation of cell-laden microgels are limited by numerous challenges, including poorly uncontrolled batch-to-batch variations, processes that are both labor- and time-consuming, the high expense of devices and reagents, and low production rates; this hampers the translation of laboratory findings to clinical applications. To address these challenges, we develop a droplet-based microfluidic strategy based on metastable droplet-templating and microchannel integration for the substantial large-scale production of single cell-laden alginate microgels. Specifically, we present a continuous processing method for microgel generation by introducing amphiphilic perfluoronated alcohols to obtain metastable emulsion droplets as sacrificial templates. In addition, to adapt to the metastable emulsion system, integrated microfluidic chips containing 80 drop-maker units are designed and optimized based on the computational fluid dynamics simulation. This strategy allows single cell encapsulation in microgels at a maximum production rate of 10 ml hr-1 of cell suspension while retaining cell viability and functionality. These results represent a significant advance toward using cell-laden microgels for clinical-relevant applications, including cell therapy, tissue regeneration and 3D bioprinting.
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Reducing the contact time using macro anisotropic superhydrophobic surfaces—Effect of parallel wire spacing on the drop impact
nature.com
Surfaces designed to reduce the contact time of impacting droplets are potentially of great importance for fundamental science and technological applications, for example, anti-icing, self … [Read More]
Author: M Song, Z Liu, Y Ma, Z Dong, Y Wang, L Jiang
Abstract:
Surfaces designed to reduce the contact time of impacting droplets are potentially of great importance for fundamental science and technological applications, for example, anti-icing, self-cleaning and heating transfer applications. Previous studies have shown that the contact time can be reduced via introducing one or several crossing macroscale wires on superhydrophobic surfaces (SHSs). However, the impacts that strike far from the wires (off-center impacts) have contact times that are equal to those obtained on SHSs. Here we demonstrate that this problem can be largely solved by using macro anisotropic SHSs (macro-aniso-SHSs)—in which the wires are parallel and macroscaled. The droplet contact time depends on the spacing between the macrostripes and is remarkably reduced by 40–50% when the spacing is comparable to the droplet size. Obvious differences in the contact time are not observed for impacts that are centered on the stripe and in the groove. The impacts centered in the groove produce new hydrodynamics that are characterized by extended spreading, easy break up and bouncing in a flying-eagle configuration. The study discusses the underlying mechanisms of the impact processes. Moreover, the effect of parallel wires on the contact time is discussed by comparing the droplet impact data for grooved rice leaves and non-grooved cabbage leaves. The enhanced drop mobility associated with the macro-aniso-SHSs should be very useful in many industrial applications.
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The Bond-Slip Relationship at FRP-to-Brick Interfaces under Dynamic Loading
mdpi.com
… The strain was measured by a two-dimensional digital image correlation (DIC) method combined with a high-speed camera (iX Cameras, Rochford Essex, UK) … [Read More]
Author: D Zhang, J Yang, LY Chi
Abstract:
Interface debonding between fiber reinforced polymers (FPR) and substrates is the principal failure mode for FRP-reinforced structure. To understand the bond–slip relationship at FRP-to-brick interfaces under dynamic loading, the influences of the dynamic enhancement of material performance on the bond–slip curve were studied. Single-lap shear tests under two different loading rates were performed, and the slip distribution curves at different loading stages were fitted to derive the bond–slip relationship. Then a numerical model considering the strain rate effects on materials was built and verified with test results. Further, the influences of brick strength, FRP stiffness and slip rate on the bond–slip relationship were investigated numerically. The research results show that FRP stiffness mainly influences the shape of the bond–slip curve, while brick strength mainly influences the amplitude of the bond–slip curve. The variations of the bond–slip relationship under dynamic loading, i.e., under different slip rates, are mainly caused by the dynamic enhancement of brick strength, and also by the dynamic enhancement of FRP stiffness, especially within a specific slip rate range. The proposed empirical formula considering dynamic FRP stiffness and dynamic brick strength can be used to predict the bond–slip relationship at the FRP-to-brick interface under dynamic loading
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Damage mechanisms of 3-D rectangular braided composite under multiple impact compressions
Elsevier
... apparatus. The compressive deformation was recorded with i-SPEED 716 high-speed camera from IX cameras Ltd (United Kingdom) as shown in Fig ... [Read More]
Author: X Gao, B Sun, B Gu - Aerospace Science and Technology
Abstract:
This paper reports the damage mechanisms of 3-D carbon fiber/epoxy braided composite under multiple impact compressions along out-plane direction. The multiple compression tests were conducted on a split Hopkinson pressure bar (SHPB) apparatus. The compressive deformations and damages were photographed with high speed camera and compared with those from finite element analyses (FEA). We found that the initial compressive damages are fiber/resin interface damage and resin fragmentation. Then the braided preform was in a severe shear damage which accompanied with further damages of interface and resin under the followed impact compressions. The energy absorptions by the reinforcement and epoxy resin at the multiple impacts were decomposed. The braided composite has the highest energy absorption capability at the first impact. The yarn orientation in braided preform leads to non-uniform stress and strain distribution. This non-uniformity easily induced the local damage and furthermore the catastrophic failure under the multiple compressions.
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