scholarly journals Air mediates the impact of a compliant hemisphere on a rigid smooth surface

Soft Matter ◽  
2021 ◽  
Author(s):  
Siqi Zheng ◽  
Sam Dillavou ◽  
John M. Kolinski
Keyword(s):  
Elastic Body ◽  
Elastic Properties ◽  
Impact Velocity ◽  
Solid Surface ◽  
High Speed ◽  
Smooth Surface ◽  
High Speed Imaging ◽  
The Impact ◽  
Rigid Smooth

When a soft elastic body impacts upon a smooth solid surface, the intervening air fails to drain, deforming the impactor. High-speed imaging with the VFT reveal rich dynamics and sensitivity to the impactor's elastic properties and the impact velocity.

scholarly journals Rebound of self-lubricating compound drops

2020 ◽  
Vol 6 (11) ◽  
pp. eaay3499 ◽  
Author(s):  
Nathan Blanken ◽  
Muhammad Saeed Saleem ◽  
Carlo Antonini ◽  
Marie-Jean Thoraval
Keyword(s):  
Solid Surface ◽  
High Speed ◽  
Water Drop ◽  
Three Dimensional ◽  
Strong Impact ◽  
High Speed Imaging ◽  
Three Dimensional Printing ◽  
Compound Drops ◽  
The Impact ◽  
Dimensional Printing

Drop impact on solid surfaces is encountered in numerous natural and technological processes. Although the impact of single-phase drops has been widely explored, the impact of compound drops has received little attention. Here, we demonstrate a self-lubrication mechanism for water-in-oil compound drops impacting on a solid surface. Unexpectedly, the core water drop rebounds from the surface below a threshold impact velocity, irrespective of the substrate wettability. This is interpreted as the result of lubrication from the oil shell that prevents contact between the water core and the solid surface. We combine side and bottom view high-speed imaging to demonstrate the correlation between the water core rebound and the oil layer stability. A theoretical model is developed to explain the observed effect of compound drop geometry. This work sets the ground for precise complex drop deposition, with a strong impact on two- and three-dimensional printing technologies and liquid separation.

Experimental investigation of the quasi-static and impact tests on the energy absorption characteristics of coupler rubber buffers used in railway vehicles

2018 ◽  
Vol 233 (9) ◽  
pp. 937-950 ◽  
Author(s):  
Shuguang Yao ◽  
Zhixiang Li ◽  
Wen Ma ◽  
Ping Xu ◽  
Quanwei Che
Keyword(s):  
Energy Absorption ◽  
Impact Velocity ◽  
High Speed ◽  
Compression Tests ◽  
Static Compression ◽  
Static Tests ◽  
Impact Tests ◽  
High Speed Trains ◽  
The Impact ◽  
Absorption Characteristics

Coupler rubber buffers are widely used in high-speed trains, to dissipate the impact energy between vehicles. The rubber buffer consists of two groups of rubbers, which are pre-compressed and then installed into the frame body. This paper specifically focuses on the energy absorption characteristics of the rubber buffers. Firstly, quasi-static compression tests were carried out for one and three pairs of rubber sheets, and the relationship between the energy absorption responses, i.e. Eabn  =  n ×  Eab1, Edissn =  n ×  Ediss1, and Ean =  Ea1, was obtained. Next, a series of quasi-static tests were performed for one pair of rubber sheet to investigate the energy absorption performance with different compression ratios of the rubber buffers. Then, impact tests with five impact velocities were conducted, and the coupler knuckle was destroyed when the impact velocity was 10.807 km/h. The results of the impact tests showed that with the increase of the impact velocity, the Eab, Ediss, and Ea of the rear buffer increased significantly, but the three responses of the front buffer did not increase much. Finally, the results of the impact tests and quasi-static tests were contrastively analyzed, which showed that with the increase of the stroke, the values of Eab, Ediss, and Ea increased. However, the increasing rates of the impact tests were higher than that of the quasi-static tests. The maximum value of Ea was 68.76% in the impact tests, which was relatively a high value for the vehicle coupler buffer. The energy capacity of the rear buffer for dynamic loading was determined as 22.98 kJ.

High Speed Liquid Impact Onto Wetted Solid Surfaces

1994 ◽  
Vol 116 (2) ◽  
pp. 345-348 ◽  
Author(s):  
H. H. Shi ◽  
J. E. Field ◽  
C. S. J. Pickles
Keyword(s):  
Shock Wave ◽  
Liquid Layer ◽  
Solid Surface ◽  
High Speed ◽  
Shear Failure ◽  
Soda Lime ◽  
Liquid Jet ◽  
Soda Lime Glass ◽  
The Impact

The mechanics of impact by a high-speed liquid jet onto a solid surface covered by a liquid layer is described. After the liquid jet contacts the liquid layer, a shock wave is generated, which moves toward the solid surface. The shock wave is followed by the liquid jet penetrating through the layer. The influence of the liquid layer on the side jetting and stress waves is studied. Damage sites on soda-lime glass, PMMA (polymethylmethacrylate) and aluminium show the role of shear failure and cracking and provide evidence for analyzing the impact pressure on the wetted solids and the spatial pressure distribution. The liquid layer reduces the high edge impact pressures, which occur on dry targets. On wetted targets, the pressure is distributed more uniformly. Despite the cushioning effect of liquid layers, in some cases, a liquid can enhance material damage during impact due to penetration and stressing of surface cracks.

scholarly journals When does a granular material behave like a continuum fluid?

2012 ◽  
Vol 704 ◽  
pp. 1-4 ◽  
Author(s):  
John R. de Bruyn
Keyword(s):  
Granular Material ◽  
Temporal Resolution ◽  
High Speed ◽  
High Impact ◽  
High Temporal Resolution ◽  
Granular Bed ◽  
Fluid Limit ◽  
High Speed Imaging ◽  
Impact Energies ◽  
The Impact

AbstractA flowing granular material can behave like a collection of individual interacting grains or like a continuum fluid, depending in large part on the energy imparted to the grains. As yet, however, we have no general understanding of how or under what conditions the fluid limit is reached. Marston, Li & Thoroddsen (J. Fluid Mech., this issue, vol. 704, 2012, pp. 5–36) use high-speed imaging to investigate the ejection of grains from a granular bed due to the impact of a spherical projectile. Their high temporal resolution allows them to study the very fast processes that take place immediately following the impact. They demonstrate that for very fine grains and high impact energies, the dynamics of the ejecta is both qualitatively and quantitatively similar to what is seen in analogous experiments with fluid targets.

scholarly journals The effects of surface tension on the spreading ratio during the impact of multiple droplets onto a hot solid surface

2018 ◽  
Vol 197 ◽  
pp. 08016
Author(s):  
Rafil Arizona ◽  
Teguh Wibowo ◽  
Indarto Indarto ◽  
Deendarlianto Deendarlianto
Keyword(s):  
Surface Tension ◽  
Ethylene Glycol ◽  
Solid Surface ◽  
High Speed ◽  
Frame Rate ◽  
Stainless Steel Surface ◽  
Droplet Spreading ◽  
Secondary Droplets ◽  
The Impact ◽  
Maximum Spreading

The impact between multiple droplets onto hot surface is an important process in a spray cooling. The present study was conducted to investigate the dynamics of multiple droplet impact under various surface tensions. Here, the ethylene glycol with compositions of 0%, 5%, and 15% was injected through a nozzle onto stainless steel surface as the multiple droplet. The solid surface was heated at the temperatures of 100 °C, 150 °C, and 200 °C. To observe the dynamics of multiple droplets, a high speed camera with the frame rate of 2000 fps was used. A technique of image processing was developed to determine the maximum droplet spreading ratio. As the result, the surface tension contributes significantly to maximum spreading ratio. As the droplet surface tension decreases, the maximum spreading ratio increases. The maximum spreading ratio appears when the percentage of the ethylene glycol is 15% at the temperature of 150°C. From the visual observation, it is shown that a slower emergence of secondary droplets (droplet splashing) is carried out under a lower surface tension. Hence, surface tension plays an important role on the behavior of emerging secondary droplets. Furthermore, results of the experiments are useful for the validation of available previous CFD models.

Effect of Timing and Velocity of Impact on Ventricular Myocardial Rupture

1983 ◽  
Vol 105 (1) ◽  
pp. 1-5 ◽  
Author(s):  
Ian V. Lau
Keyword(s):  
Impact Velocity ◽  
High Speed ◽  
Left Ventricular ◽  
High Impact ◽  
Muscle Stiffness ◽  
Cardiac Rupture ◽  
Myocardial Wall ◽  
High Impact Velocity ◽  
Myocardial Rupture ◽  
The Impact

The effects of impact timing during the cardiac cycle on the sensitivity of the heart to impact-induced rupture was investigated in an open-chest animal model. Direct mechanical impacts were applied to two adjacent sites on the exposed left ventricular surface at the end of systole or diastole. Impacts at 5 m/s and a contact stroke of 5 cm at the end of systole resulted in no cardiac rupture in seven animals, whereas similar impacts at the end of diastole resulted in six cardiac ruptures. Direct impact at 15 m/s and a contact stroke of 2 cm at the end of either systole or diastole resulted in perforationlike cardiac rupture in all attempts. At low-impact velocity the heart was observed in high-speed movie to bounce away from the impact interface during a systolic impact, but deform around the impactor during a diastolic impact. The heart generally remained motionless during the downward impact stroke at high-impact velocity in either a systolic or diastolic impact. The lower ventricular pressure, reduced muscle stiffness, thinner myocardial wall and larger mass of the filled ventricle probably contributed to a greater sensitivity of the heart to rupture in diastole at low-impact velocity. However, the same factors had no role at high-impact velocity.

Numerical Modeling of Hydrodynamic Impact and Local Slamming Effects

2015 ◽  
Author(s):  
Ali Mohtat ◽  
Ravi Challa ◽  
Solomon C. Yim ◽  
Carolyn Q. Judge
Keyword(s):  
Numerical Method ◽  
Impact Velocity ◽  
High Speed ◽  
Impact Behavior ◽  
Analytical Prediction ◽  
Arbitrary Lagrangian Eulerian ◽  
Hydrodynamic Impact ◽  
Ale Formulation ◽  
Wide Range ◽  
The Impact

Numerical simulation and prediction of short duration hydrodynamic impact loading on a generic wedge impacting a water free-surface is investigated. The fluid field is modeled using a finite element (FE) based arbitrary Lagrangian-Eulerian (ALE) formulation and the structure is modeled using a standard Lagrangian FE approximation. Validation of the numerical method against experimental test data and closed form analytical solutions shows that the ALE-FE/FE continuum approach captures the impact behavior accurately. A detailed sensitivity analysis is conducted to study the role of air compressibility, deadrise angle, and impact velocity in estimation of maximum impact pressures. The pressure field is found to be insensitive to air compressibility effect for a wide range of impact velocities and deadrise angles. A semi-analytical prediction model is developed for estimation of maximum impact pressures that correlates deadrise angle, impact velocity, and a nonlinear interaction term that couples hydrodynamic effects between these parameters. The numerical method is also used to examine the intrinsic physics of water impact on a high-speed planing hull with the goal of predicting slamming loads and resulting motions.

Study on the Dimensionless Model of High-Speed Penetration Efficiency

2015 ◽  
Vol 789-790 ◽  
pp. 362-367
Author(s):  
Mei Li Song ◽  
Xiao Ming Wang ◽  
Wen Bin Li
Keyword(s):  
Impact Velocity ◽  
High Speed ◽  
Diameter Ratio ◽  
Target Strength ◽  
Mechanical Parameters ◽  
Engineering Model ◽  
Model Calculations ◽  
Dimensionless Equation ◽  
Penetration Ability ◽  
The Impact

Penetration efficiency reflects high speed projectile penetration ability with the impact velocity (>800m/s) variation. To further study the penetration efficiency engineering model, the physical and mechanical parameters that affect the penetration efficiency of high-speed projectiles penetrating into concrete target are analyzed, penetration efficiency dimensionless quantities are determined, such as projectile’s length to diameter ratio, projectile and target strength ratio, etc. The dimensionless equation of penetration efficiency is got by using the homogeneous principles of the laws of physics dimensionless. According to experimental data, a function of dimensionless penetration efficiency and dimensionless projectile speed is fitted. Finally, the model is verified by test, and the model calculations and experiment results agree well. The model obtained in this paper can estimate the projectile’s impact velocity when the penetration efficiency reaches the maximum, it would be a theoretical guidance for high speed penetration effects experiments.

Drop impingement erosion of metals

1970 ◽  
Vol 314 (1519) ◽  
pp. 549-565 ◽  
Keyword(s):  
Fatigue Failure ◽  
Solid Surface ◽  
Liquid Flow ◽  
High Speed ◽  
Erosion Rate ◽  
Impact Pressure ◽  
Specimen Surface ◽  
Microplastic Deformation ◽  
Metal Fatigue ◽  
The Impact

The object of the work has been to investigate experimentally the mechanisms of erosion in metals and alloys under drop impingement attack. For this purpose an apparatus of the wheel and jet type has been used to erode aluminium, copper, iron, cobalt and alloys of these metals. The various stages in the process from the first detectable microplastic deformation to the eventual pitting and removal of material from the surface have been investigated. In addition, experiments were carried out with the purpose of examining the effects of the normal impact pressure of a liquid on a surface in the absence of shear forces associated with liquid flow. This was achieved by propagating impact-generated compression waves through a liquid column in a filled and sealed cylinder onto a specimen surface inside the cylinder. With this arrangement the initial damage—small shallow depressions in the specimen surface— was identical with that produced under standard drop impact conditions in the wheel and jet apparatus. In either case the calculated values of the maximum impact pressure were lower than the average yield strength of each metal investigated. A complementary series of experiments was carried out in order to examine the erosive effects of liquid flow over the surface in the absence of high impact pressures. The technique used here involved a continuous high-speed water jet impinging against a solid surface at glancing incidence. This study showed that while flat well polished surfaces were apparently unaffected by the flow, lightly roughened surfaces or surfaces which contained the shallow impact depressions were severely eroded in regions adjacent to discontinuities. These various experiments suggest that the initial yielding which gives rise to the depression is associated with non-uniformity in the strength, structure and shape of the solid surface rather than with local variations in the impact pressure over the surface. The subsequent acceleration in the erosion rate is linked with the increased roughening of the surface and with an increase in the shear damage. When the surface becomes very rough and pitted, the impinging drop is deflected into less damaging streams by surface projections. This effect would account for the eventual decrease observed in the erosion rate. Further studies of the structure of the eroded surfaces have shown that the fractures have a number of features which are characteristic of metal fatigue failure. The connexion between erosion and fatigue is illustrated by similarities between the endurance curves for erosion and for the same metal in a standard fatigue test. As in the case of fatigue failure, strain energy to fracture appears to be one of the most important mechanical properties determining the erosive behaviour of a ductile metal.

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