A discussion on deformation of solids by the impact of liquids, and its relation to rain damage in aircraft and missiles, to blade erosion in steam turbines, and to cavitation erosion - Practical aspects of cavitation

1966 ◽  
Vol 260 (1110) ◽  
pp. 267-294 ◽  
Keyword(s):  
Laboratory Tests ◽  
Cavitation Erosion ◽  
Erosion Resistance ◽  
Drop Impact ◽  
Fatigue Tests ◽  
Steam Turbines ◽  
Threshold Velocity ◽  
Number Of Factors ◽  
Drop Impact Test ◽  
The Impact

Damage produced by cavitation under field conditions can be a serious problem. The main causes of this damage and its characteristics are discussed briefly and possible remedial measures are examined. Accelerated laboratory tests are found to play an important part in cavitation erosion research, but interpretation of results needs care. Most past investigators have tended to treat cavitation damage and droplet erosion as unrelated phenomena and only qualitative correlations between the respective simulated tests have been possible. This paper presents an attempt to correlate quantitatively the results of three different erosion tests. A broad correlation between results of the drop impact erosion and constricted tube cavitation tests shows general agreement. A more detailed, but restricted, correlation has been obtained between results of drop impact and vibratory cavitation erosion tests. In both correlations, however, there is evidence of some discrepancies between corrodible and incorrodible materials. A number of factors which govern the rate of damage in the various laboratory tests are of interest. In particular, in the drop impact test the velocity of collision and the jet diameter are shown to have significant effects. There is a marked similarity between the behaviour of materials in this test and in fatigue tests and also evidence of a threshold velocity below which measurable damage ceases. The other laboratory tests were found to have their own particular controlling parameters, but the general phenomenon of cavitation erosion is more complex and is not discussed in detail. By conducting comparative tests under reproducible conditions it has been possible to classify a variety of new and traditional materials in order of relative erosion resistance and thus provide some guide to their selection for service. While the results add to the evidence that hardness is the major attribute controlling erosion resistance other properties such as ductility, elasticity and fatigue strength are seen to be significant.

The Evaluation of the Cavitational Damage in MgAl2Si Alloy Using Various Laboratory Stands

2016 ◽  
Vol 252 ◽  
pp. 61-70
Author(s):  
Robert Jasionowski ◽  
Dariusz Zasada ◽  
Wojciech Polkowski
Keyword(s):  
Cavitation Erosion ◽  
Erosion Resistance ◽  
Flow Conditions ◽  
Final Phase ◽  
Testing Conditions ◽  
Jet Impact ◽  
Cavitation Tunnel ◽  
Actual Flow ◽  
Cavitation Erosion Resistance ◽  
The Impact

Evaluation of cavitation erosion resistance of is carried out by using various testing stands, that differ by the way of cavitation excitation and its intensity. These various testing conditions have led to a standardization of some part of laboratory stands, that in turn allows a direct comparison of results obtained in different laboratories. The aim of this study was to determine the course of cavitational destruction of MgAl2Si alloy samples tested on three different laboratory stands. The research was conducted on a vibration stand according to ASTM G32, where cavitation is forced by the vibrating element; in the cavitation tunnel reflecting actual flow conditions, and on a jet impact stand- simulating the impact microjet in the final phase of the cavitational bubbles implosion. Each laboratory stand has given a different course of cavitational destruction.

A discussion on deformation of solids by the impact of liquids, and its relation to rain damage in aircraft and missiles, to blade erosion in steam turbines, and to cavitation erosion - The formation of microjets in liquids under the influence of impact or shock

1966 ◽  
Vol 260 (1110) ◽  
pp. 94-95 ◽  
Keyword(s):  
Cavitation Erosion ◽  
Concave Surface ◽  
Short Film ◽  
Steam Turbines ◽  
Small Cavity ◽  
The Impact

If a small cavity or bubble in a liquid is subject to impact or to shock, tiny Munroe jets may be formed on its concave surface. The velocity of these microjets may be high. A short film illustrating the formation of these small jets in cavities and in coalescing drops was shown.

A discussion on deformation of solids by the impact of liquids, and its relation to rain damage in aircraft and missiles, to blade erosion in steam turbines, and to cavitation erosion - The collapse of cavitation bubbles and the pressures thereby produced against solid boundaries

1966 ◽  
Vol 260 (1110) ◽  
pp. 221-240 ◽  
Keyword(s):  
Cavitation Erosion ◽  
Experimental Information ◽  
Liquid Jets ◽  
Steam Turbines ◽  
Jet Formation ◽  
Cavitation Damage ◽  
Cavity Collapse ◽  
New Ideas ◽  
The Impact ◽  
Shape Changes

Our object is to present a broad review of this subject as a branch of hydrodynamics, referring both to the well known ‘implosion’ mechanism first analysed by Lord Rayleigh and, more particularly, to the recently perceived possibility that effects of equally great violence, such as to damage solid boundaries, may arise through the impact of liquid jets formed by collapsing cavities. In §2 a few practical facts about cavitation damage are recalled by way of background, and then in §3 the significance of available theoretical and experimental information about cavity collapse is discussed. The main exposition of new ideas is in §4, which is a review of the factors contributing to shape changes and eventual jet formation by collapsing cavities. Finally, in §5, some new experimental observations on the unsymmetrical collapse of vapour-filled cavities are presented.

A discussion on deformation of solids by the impact of liquids, and its relation to rain damage in aircraft and missiles, to blade erosion in steam turbines, and to cavitation erosion - Damage to solids caused by cavitation

1966 ◽  
Vol 260 (1110) ◽  
pp. 245-255 ◽  
Keyword(s):  
Mechanical Properties ◽  
Cavitation Erosion ◽  
Cavitation Resistance ◽  
Steam Turbines ◽  
Single Event ◽  
Cavitation Damage ◽  
Erosion Damage ◽  
Highly Sensitive ◽  
Wide Range ◽  
The Impact

This paper describes the early stages of cavitation damage observed in cavitating venturi tunnels. The cavitating fluids were water and mercury, and a wide range of specimen materials were used. The damage was found to consist of single-event symmetical craters and irregular fatigue-type failures. The degree of damage was highly sensitive to minor flow perturbations, and this is discussed. The effect of stress level in the specimen before testing, and relations between cavitation resistance and the mechanical properties of the materials are considered.

A discussion on deformation of solids by the impact of liquids, and its relation to rain damage in aircraft and missiles, to blade erosion in steam turbines, and to cavitation erosion - Conclusion

1966 ◽  
Vol 260 (1110) ◽  
pp. 311-315
Keyword(s):  
High Speed ◽  
Rear Surface ◽  
Peak Load ◽  
Brittle Materials ◽  
Front Surface ◽  
Drop Impact ◽  
Surface Flow ◽  
Steam Turbines ◽  
Brittle Solids ◽  
The Impact

Basic studies show that the measured impact pressure can be accounted for by assuming compressible deformation of the liquid drop in the first stages of impact. The distribution of pressure under a drop produces a shallow indentation in the surface of ductile solids and a ring fracture in brittle materials. The flow of liquid across the surface from under the drop leads to erosive shearing along the edges of the deformed area. Although in theory erosion due to surface flow would not occur on perfectly smooth surfaces, ideal conditions of this kind are impracticable. The smallest discontinuities (step heights down to about 1000 A) have been shown to act as nuclei for erosion pits. The short duration of the peak load during drop impact gives the impact an explosive character. In brittle materials the reflexion and interference of stress waves can cause extensive fracture in regions remote from the initial impact area. Spalling of the rear surface of a thin plate due to drop impact on the front surface could be an important mechanism in the failure of ceramic radomes in high speed aircraft and missiles. To some extent the strength of brittle solids can be improved by treatments which alter the size or number of surface flaws.

Quantitative Evaluation of Cavitation Erosion

1998 ◽  
Vol 120 (1) ◽  
pp. 179-185 ◽  
Author(s):  
Shuji Hattori ◽  
Hiroyuki Mori ◽  
Tsunenori Okada
Keyword(s):  
Impact Energy ◽  
Cavitation Erosion ◽  
Erosion Resistance ◽  
Impact Load ◽  
Bubble Collapse ◽  
Impact Loads ◽  
Volume Loss ◽  
Developed Pressure ◽  
Cavitation Erosion Resistance ◽  
The Impact

In order to evaluate the quantitative cavitation-erosion resistance of materials, a pressure-detector-installed specimen was developed, which can measure both the impact load produced by cavitation bubble collapse and the volume loss simultaneously. Test specimens (pressure-detection rod) used were nine kinds of metals and were exposed to vibratory cavitation. A linear relation was obtained for all materials between the accumulated impact energy ∑Fi2 calculated from the distribution of impact loads and the volume loss, independent of test conditions. Impact energy accumulated during the incubation period and the energy for a unit material removal in steady-state period were obtained from the relation. These values are very Important concerning quantitative erosion resistance evaluation. That is, when the distribution of impact loads is acquired for different cavitation conditions, the volume loss can be estimated. This idea was applied to the venturi cavitation erosion. The experimental results for venturi test corresponds well with the prediction using these impact energy values. It was concluded that the quantitative impact energy values of materials can be determined independent of the apparatus and the test condition by using the newly developed pressure-detector-installed specimen.

A discussion on deformation of solids by the impact of liquids, and its relation to rain damage in aircraft and missiles, to blade erosion in steam turbines, and to cavitation erosion - The resistance of materials to impact erosion damage

1966 ◽  
Vol 260 (1110) ◽  
pp. 193-203 ◽  
Keyword(s):  
Mechanical Properties ◽  
Mass Loss ◽  
Incubation Period ◽  
Turbine Blade ◽  
Cavitation Erosion ◽  
Steam Turbines ◽  
Microstructural Characteristics ◽  
Erosion Damage ◽  
The Impact ◽  
Impact Erosion

The behaviour of established and potential turbine blade and erosion shield materials subject to impact erosion by water droplets of controlled size has been investigated over a range of impact velocities up to 1040 ft./s. Both the topographical form and the microstructural characteristics of damage have been studied, and correlated with the conditions of the test and the mechanical properties and phase constitution of the materials. It has been found that the rate of erosion, as measured by mass loss, changes during the course of a test. An initial incubation period is generally followed, successively, by periods of increasing, constant, and then decreasing rates of erosion, possibly culminating in a second steady, but lower, rate of erosion.

A discussion on deformation of solids by the impact of liquids, and its relation to rain damage in aircraft and missiles, to blade erosion in steam turbines, and to cavitation erosion - The erosion of solids by the repeated impact of liquid drops

1966 ◽  
Vol 260 (1110) ◽  
pp. 121-139 ◽  
Keyword(s):  
Cavitation Erosion ◽  
Impact Load ◽  
Steam Turbines ◽  
Repeated Impact ◽  
Ductile Metals ◽  
Liquid Drops ◽  
Liquid Impact ◽  
Erosion Behaviour ◽  
Brittle Polymers ◽  
The Impact

An investigation of the erosion of solids by repeated liquid impact at relatively low velocities has been carried out. The work has shown that even at low velocities compressible behaviour of the liquid is important in determining the impact pressure. An attempt has also been made to determine the distribution of the impact load. The mechanism of erosion in brittle polymers and in ductile metals has been studied. The effect of altering the conditions of impact on the erosion behaviour is described.

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