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.

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 - High speed liquid impact

1966 ◽  
Vol 260 (1110) ◽  
pp. 79-85 ◽  
Keyword(s):  
High Speed ◽  
Cavitation Erosion ◽  
High Strain ◽  
Strain Rates ◽  
Steam Turbines ◽  
High Speeds ◽  
Liquid Impact ◽  
Deformation Patterns ◽  
The Impact ◽  
Very High

A study has been made of the deformation at high strain rates of solids under the impact of liquids. A method is described for projecting a short liquid jet against a solid surface at speeds up to 1200 m/s. The flow of the liquid and the deformation of the solid during impact have been examined by high speed photographic methods. An attempt has been made to measure the magnitude and duration of the load by means of a piezoelectric pressure transducer. There is evidence that the liquid behaves initially on impact in a compressible manner. Part of the deformation of the solid is due to this compressible behaviour and part to the erosive shearing action of the liquid flowing at very high speeds out across the surface. The mode of deformation in brittle and in plastically deforming materials has been investigated. The deformation patterns produced are shown to be characteristic of liquid impact. The predominating mechanism of deformation depends on the mechanical properties of the solid and on the velocity of impact.

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 initial stages of deformation in metals subjected to repeated liquid impact

1966 ◽  
Vol 260 (1110) ◽  
pp. 140-143 ◽  
Keyword(s):  
Shock Waves ◽  
Cavitation Erosion ◽  
Loading Conditions ◽  
Steam Turbines ◽  
Hydrodynamic Loading ◽  
Liquid Impact ◽  
Rapid Flow ◽  
The Impact

Experiments have been carried out to investigate the initial stages in the deformation of metals due to repeated liquid impacts. The initiation of damage is discussed and a comparison made with the initial stages of deformation in metals subjected to similar hydrodynamic loading conditions due to the action of shock waves in a liquid. The destructive role played by the rapid flow of liquid across the surface of a specimen after impact is also described.

scholarly journals 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 - Introduction

1966 ◽  
Vol 260 (1110) ◽  
pp. 76-77 ◽  
Keyword(s):  
Cavitation Erosion ◽  
Water Drop ◽  
Short Interval ◽  
Dynamic Strength ◽  
Strength Properties ◽  
Steam Turbines ◽  
Small Water ◽  
Liquid Impact ◽  
The Impact ◽  
Very High

The meeting will begin by considering the physics of liquid impact and the nature, magnitude and duration of the stresses which are produced when a solid is struck by a jet or by a drop of liquid. Even with moderate impacts the pressures developed in the solid are considerable and at high velocities the pressures are very great indeed, and are sufficient to produce deformation of the strongest solids. As we shall see a small water drop, the size of a raindrop, striking a solid moving at a speed of about 500 m/s (Mach 1.5) will exert a pressure of ca. 130 Kg/mm 2 (1.9 x 10 5 Lb./ in. 2 ) on the surface of the solid. The effect resembles that of a small explosion and at this stress level most solids and structural materials are permanently damaged either by plastic flow or by fracture. Since the pressure is applied for a very short interval of time (a few microseconds), it is the dynamic strength properties of the solid at very high rates of strain which are important. Both the nature and duration of the stresses and the mechanism by which deformation occurs will be considered. Apart from the shock pressure the rapid tangential flow of the liquid across the surface will produce deformation and these two effects interact. If the solid is subjected to multiple liquid impact, deformation will occur at much lower impact velocities and pressures. We shall consider the physics of both these processes.

scholarly journals Impact Response of Hammerhead Pier Fibrous Concrete Beams Designed with Topology Optimization

2020 ◽  
Author(s):  
Meivazhisalai Parasuraman Salaimanimagudam ◽  
Covaty Ravi Suribabu ◽  
Gunasekaran Murali ◽  
Sallal R. Abid
Keyword(s):  
Topology Optimization ◽  
Concrete Beams ◽  
Impact Load ◽  
Impact Resistance ◽  
Adaptive Mesh ◽  
Impact Response ◽  
Adaptive Meshing ◽  
Repeated Impact ◽  
Ductility Ratio ◽  
The Impact

Reducing the weight of concrete beams is a primary (beyond strength and durability) concern of engineers. Therefore, this research was directed to investigate the impact response of hammerhead pier concrete beams designed with density-based method topology optimization. The finite element topology optimization was conducted using Autodesk fusion 360 considering three different mesh sizes of 7 mm, 10 mm, and adaptive meshing. Three optimized hammerhead beam configurations; HB1, HB2, and HB3, respectively, with volume reductions greater than 50 %. In the experimental part of this research, nine beams were cast with identical size and configuration to the optimized beams. Three beams, identical to the optimized beams, were tested under static bending for verification purposes. In comparison, six more beams, as in the preceding three beams but without and with hooked end steel fibers, were tested under repeated impact load. The test results revealed that the highest flexural capacity and impact resistance at crack initiation and failure were recorded for the adaptive mesh beams (HB3 and HB3SF). The failure impact energy and ductility ratio of the beam HB3SF was higher than the beams HB1SF and HB2SF by more than 270 %. The results showed that the inclusion of steel fiber duplicated the optimized beam’s impact strength and ductility several times. The failure impact resistance of fibrous beams was higher than their corresponding plain beams by approximately 2300 to4460 %, while their impact ductility ratios were higher by 6.0 to 18.1 times.

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 - The application of dislocation etching techniques to the study of liquid impacts

1966 ◽  
Vol 260 (1110) ◽  
pp. 101-120 ◽  
Keyword(s):  
Liquid Droplet ◽  
Effective Area ◽  
Optical Microscope ◽  
Dislocation Loops ◽  
Steam Turbines ◽  
Liquid Drops ◽  
Dislocation Etching ◽  
Chemical Etch ◽  
The Impact ◽  
Droplet Impacts

Erosion damage is very often the cumulative result of a series of liquid droplet impacts which individually do not produce any deformation visible under the optical microscope. Such collisions do, however, produce dislocations in the crystalline structure surrounding the area of impact, and in suitable materials these dislocations can be revealed by chemical etch pitting. The technique is particularly easy to apply to freshly cleaved lithium fluoride crystals, and it has been used to study several types of impact. The impact of solid balls produces symmetrical rosettes of dislocations lying on {110} planes, and the dimensions of the rosettes can be related to the area of contact and stress distribution calculated from the theory of the collision of elastic/plastic bodies. Similar, but less symmetrical, rosettes are produced by liquid impacts and, by comparison of the extent and distribution of the dislocation loops in the two cases, it has been possible to make an estimate of the pressure and effective area of contact for liquid drops of various sizes, quantities which are otherwise difficult to measure. The behaviour of liquids other than water has also been investigated.

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.

Studies of two-dimensional liquid-wedge impact and their relevance to liquid-drop impact problems

1985 ◽  
Vol 401 (1821) ◽  
pp. 225-249 ◽  
Keyword(s):  
High Speed ◽  
Liquid Drop ◽  
Time History ◽  
Drop Impact ◽  
High Speed Photography ◽  
Two Dimensional ◽  
Surface Geometry ◽  
Repeated Impact ◽  
Liquid Impact ◽  
The Impact

In the initial stage of liquid-drop impact, the contact region expands faster than the wave speed in the liquid. This causes compressible behaviour in the liquid, and high transient pressures. High-velocity jetting results when the wave motion in the liquid overtakes the expanding contact edge and moves up the free surface of the drop. The detailed pressure fields in this early time history of impact have been calculated by Lesser ( Proc . R . Soc . Lond . 377, 289 (1981)) for both two and three-dimensional liquid masses and for targets of finite admittance. An important result is that the edge pressures exceed the central ‘water-hammer’ pressure 3ρ 0 CU i and at the time of shock-detachment approach ca . 3ρ 0 CU i . At this stage the edge pressures, for both spherical drops and two-dimensional liquid wedges, depend only on the impact velocity and the instantaneous angle between the liquid and solid surfaces. This suggests that the essential features of the early stage of liquid impact can be usefully studied by producing impacts with two-dimensional liquid wedges, and predicted data for pressures, shock angles and velocities are presented. Experiments are described for producing impacts with preformed shapes by using water-gelatine mixtures and observing the impact events with high-speed photography. The results confirm the main features of the model and give information on edge pressures, jetting, cavitation in the liquid and the effect of the admittance of the solid. The relevance of the results to the damage and erosion of materials subjected to liquid impact is discussed. In particular, it is possible to explain the apparently low damage-threshold of some materials, the form of damage and its development with repeated impact. The study highlights the importance of the detailed surface geometry in the region of contact.

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