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.

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.

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 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.

The mechanism of a splash on a dry solid surface

2011 ◽  
Vol 690 ◽  
pp. 148-172 ◽  
Author(s):  
Shreyas Mandre ◽  
Michael P. Brenner
Keyword(s):  
Solid Surface ◽  
High Speed ◽  
Liquid Droplet ◽  
Contact Point ◽  
Quantitative Agreement ◽  
Gas Pressure ◽  
Liquid Viscosity ◽  
Ink Jet ◽  
Jet Printing ◽  
The Impact

AbstractFrom rain storms to ink jet printing, it is ubiquitous that a high-speed liquid droplet creates a splash when it impacts on a dry solid surface. Yet, the fluid mechanical mechanism causing this splash is unknown. About fifty years ago it was discovered that corona splashes are preceded by the ejection of a thin fluid sheet very near the vicinity of the contact point. Here we present a first-principles description of the mechanism for sheet formation, the initial stages of which occur before the droplet physically contacts the surface. We predict precisely when sheet formation occurs on a smooth surface as a function of experimental parameters, along with conditions on the roughness and other parameters for the validity of the predictions. The process of sheet formation provides a semi-quantitative framework for studying the subsequent events and the influence of liquid viscosity, gas pressure and surface roughness. The conclusions derived from this framework are in quantitative agreement with previous measurements of the splash threshold as a function of impact parameters (the size and velocity of the droplet) and in qualitative agreement with the dependence on physical properties (liquid viscosity, surface tension, ambient gas pressure, etc.) Our analysis predicts an as yet unobserved series of events within micrometres of the impact point and microseconds of the splash.

Numerical Study on High-Speed Impact Between a Water Droplet and a Deformable Solid Surface

2012 ◽  
Author(s):  
Yongqiang Han ◽  
Yonghui Xie ◽  
Di Zhang
Keyword(s):  
Solid Surface ◽  
Water Droplet ◽  
High Speed ◽  
Numerical Study ◽  
Contact Radius ◽  
Deformable Solid ◽  
Theoretical Predictions ◽  
Steam Turbine Blade ◽  
Set Up ◽  
The Impact

In this study an axisymmetric model is set up to study the impact of a spherical water droplet with a planar deformable solid surface using the Lagrange-Euler coupling method which is based on a penalty formulation. The diameter and velocity of the droplet are 0.4 mm and 500 m/s respectively, while the solid is a kind of steam turbine blade material. The generated pressure distribution in the droplet and its variation with time, the formation of lateral jet, the deformation and stress distribution in the solid are obtained and investigated. It is shown that the compressibility of the droplet and the solid plays a significant role during the impact. The water-hammer pressure and the maximum contact edge pressure are calculated and in good agreement with the existing theoretical predictions. The calculated contact radius for shock departure is larger than that of the conventional theoretical prediction, which is analyzed and attributable to the radial motion of the liquid in the compressed region. The formation of the high-speed lateral jet is calculated and the time for the observable jetting is much later than that of the shock departure. This delay is discussed and the reason needs more research. The pressure of the contact edge region remains highest even after a considerable time of shock departure and lateral jetting. In the mean time, a saucer-shaped depression is generated in the center of the impact. The stress waves in solid move faster even before shock departure in the liquid. This causes disturbance of the solid surface before the high-speed lateral jetting and provides site for the scouring action of it, and subsequently may cause material damage and erosion.

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.

scholarly journals Unsteady Numerical Calculation of Oblique Submerged Jet

Energies ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4728
Author(s):  
Weixuan Jiao ◽  
Di Zhang ◽  
Chuan Wang ◽  
Li Cheng ◽  
Tao Wang
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Pressure Coefficient ◽  
High Energy ◽  
Impact Pressure ◽  
Maximum Pressure ◽  
Flow Angle ◽  
Free Jet ◽  
Velocity Flow ◽  
The Impact

A water jet is a kind of high-speed dynamic fluid with high energy, which is widely used in the engineering field. In order to analyze the characteristics of the flow field and the change of law of the bottom impact pressure of the oblique submerged impinging jet at different times, its unsteady characteristics at different Reynolds numbers were studied by using the Wray–Agarwal (W-A) turbulence model. It can be seen from the results that in the process of jet movement, the pressure at the peak of velocity on the axis was the smallest, and the velocity, flow angle, and pressure distribution remain unchanged after a certain time. In the free jet region, the velocity, flow angle, and pressure remained unchanged. In the impingement region, the velocity and flow angle decreased rapidly, while the pressure increased rapidly. The maximum pressure coefficient of the impingement plate changed with time and was affected by the Reynolds number, but the distribution trend remained the same. In this paper, the characteristics of the flow field and the law of the impact pressure changing with time are described.

scholarly journals Time-resolved imaging of a compressible air disc under a drop impacting on a solid surface

2015 ◽  
Vol 780 ◽  
pp. 636-648 ◽  
Author(s):  
E. Q. Li ◽  
S. T. Thoroddsen
Keyword(s):  
Solid Surface ◽  
High Speed ◽  
Theoretical Models ◽  
Adiabatic Compression ◽  
Time Resolved ◽  
Time Resolved Imaging ◽  
Rapid Deceleration ◽  
Drop Impacts ◽  
The Impact ◽  
Surface Minima

When a drop impacts on a solid surface, its rapid deceleration is cushioned by a thin layer of air, which leads to the entrapment of a bubble under its centre. For large impact velocities the lubrication pressure in this air layer becomes large enough to compress the air. Herein we use high-speed interferometry, with 200 ns time-resolution, to directly observe the thickness evolution of the air layer during the entire bubble entrapment process. The initial disc radius and thickness shows excellent agreement with available theoretical models, based on adiabatic compression. For the largest impact velocities the air is compressed by as much as a factor of 14. Immediately following the contact, the air disc shows rapid vertical expansion. The radial speed of the surface minima just before contact, can reach 50 times the impact velocity of the drop.

Effect of Stand-Off Distance on Impact Pressure of High-Speed Water Jet Injected in Water

2011 ◽  
Vol 52-54 ◽  
pp. 1873-1878 ◽  
Author(s):  
Anirut Matthujak ◽  
Chaidet Kasamnimitporn ◽  
Wuttichai Sittiwong ◽  
Kulachate Pianthong
Keyword(s):  
Pressure Sensor ◽  
Nozzle Exit ◽  
High Speed ◽  
Video Camera ◽  
Water Jet ◽  
Impact Pressure ◽  
High Speed Video Camera ◽  
Impact Phenomena ◽  
Acceleration Method ◽  
The Impact

This study is to measure the impact pressure of high-speed water jet injected in water at the stand-off distance from the nozzle exit. The high-speed water jets are generated by the impact of a projectile, which known as impact acceleration method, launched by Horizontal Single Stage Power Gun. The maximum averaged jet velocity of about 374.24 m/s in water was generated in this experiment. The impact pressure of high-speed water jet in water at the stand-off distance 15, 20, 30 and 40 mm from the nozzle exit was measured by the PVDF pressure sensor. Moreover, the impact phenomena of the jet were visualized by a high-speed video camera with shadowgraph optical arrangement. From the pressure sensor, two peak over-pressures are always observed in this experiment. From visualization, it was found that the two peak over-pressures of 24 GPa and 35 GPa at x = 15 mm were generated by the jet and the bubble impact, respectively. The peak over-pressure decreases exponentially as the stand-off distance between the PVDF pressure sensor to the nozzle exit increases. Moreover, the jet and the bubble impact on the PVDF pressure sensor, shock waves, and bubble deformation were obviously observed in this study.

Erosion Behaviors of Impeller Material FV520B in Centrifugal Compressor

2014 ◽  
Vol 894 ◽  
pp. 110-115 ◽  
Author(s):  
Guang Cun Wang ◽  
Jian Feng Li ◽  
Xiu Jie Jia ◽  
Zhao Ju Zhu ◽  
Qi Guo
Keyword(s):  
Centrifugal Compressor ◽  
High Speed ◽  
Erosion Rate ◽  
Impact Angle ◽  
Erosion Model ◽  
Micro Cutting ◽  
Erosion Testing ◽  
Erosion Mechanism ◽  
Compressor Impeller ◽  
The Impact

To study the erosion behaviors and mechanism of impeller material FV520B in centrifugal compressor, the erosion experiments with polygonal alumina particles were carried out on the high-speed erosion testing system. Microstructure of the erosion zone was analyzed by SEM to reveal the erosion mechanism. An erosion model to calculate the erosion rate of FV520B was developed. The results showed that, FV520B exhibited the erosion characteristics of typical plastic materials, the highest erosion rate occurred at the impact angle of 24°, the lowest erosion rate occurred at normal impact angle. The velocity index at the impact angle 24° and 90° were 3.37 and 3.68, it grew as the impact angle increased. The erosion mechanism of FV520B was micro-cutting and deformation wear, at low impact angles, the erosion was dominated by micro-cutting wear, while at high impact angle greater than 60 °, the erosion was dominated by deformation wear. Also the predictions of the erosion model were in good agreement with the results of experiments, indicating that this model can be used to estimate the erosion rate of compressor impeller under different working conditions.

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