Iain Finnie

Some observations on the erosion of ductile metals

Abstract The factors which may influence the erosion of ductile metals are listed. It is shown that the effect of some of these variables may be predicted on simple fundamental grounds. On this basis, quantitative predictions may be made for the erosion of ductile metals by hard abrasive grains which strike at grazing angles. Other aspects of erosion which are not as well understood at the present time, are also discussed.

Some reflections on the past and future of erosion

This review will focus on erosion by abrasive particles in the absence of corrosion. The importance of fluid flow conditions in the solution of practical erosion problems will be discussed and illustrated by an example. Our present understanding of the mechanisms of material removal in ductile and brittle solids will then be reviewed, and some areas which require additional insight will be identified. Finally, some thoughts on predicting the brittle-ductile transition in erosion will be presented.

On the size effect in abrasive and erosive wear

Abstract It is a familiar observation that the wear process in erosion and both two- and three-body abrasion of ductile metals becomes less efficient as the eroding or abrading particle size decreases below about 100 μm. At least a dozen explanations have been presented for this phenomenon, with most studies having been restricted to one type of wear. In the present work we present results for erosion and two-and three-body abrasion using a range of particle sizes, and we draw on the grinding and metal-cutting literature. It is concluded that the only explanation for the size effect which cannot be discounted is that shallow surface layers exhibit a higher flow stress than that of the bulk material when they are abraded or eroded.

On the velocity dependence of the erosion of ductile metals by solid particles at low angles of incidence

Abstract An earlier analytical study of the erosion of ductile metals by rigid abrasive grains was based on the volume removed when a grain cut into the surface. Among other things, this predicted a dependence of volume removal on particle velocity of the form volume ≈ (velocity) n where n = 2. However, subsequent experimental work has shown that n is greater than 2. Several alternative mechanisms of material removal have been proposed to explain this effect. In this paper, the original analysis is re-examined. By making a more realistic assumption about the location of the forces during particle-surface interaction, values of the exponent n are predicted which are in the range observed experimentally.

Erosive wear of composite materials

Abstract The erosive wear behavior of selected polymer matrix composite materials was investigated using an erosion wear tester. Scanning electron microscopy was used to characterize the eroded surface. The results show that the erosive wear rates in these materials are at least an order of magnitude greater than that of low carbon steel. Of the composites tested, continuous graphite fiber-epoxy composites showed erosive wear that is typical of brittle materials (maximum wear rate when the impingement is normal to the surface), while continuous aramid fiber-epoxy and chopped graphite fiber-polyphenylene sulfide showed quasi-ductile behavior (maximum wear rate at 25°–45° impingement angle). These results are discussed in terms of the observed failure modes.

A classification of three-body abrasive wear and design of a new tester.

Abstract A study of the literature reveals that while a considerable amount of work has been conducted on two-body abrasive wear, relatively little has been done about the equally important problem of three-body abrasive wear. A classification of the various types of three-body abrasive wear is presented. Following an examination of existing three-body abrasive wear testers and their limitations a novel tester to simulate a certain type of three-body wear has been designed. With simple modifications the tester can also simulate two-body wear. The paper describes the new tester and some preliminary results.

The influence of impingement angle on the erosion of ductile metals by angular abrasive particles

Abstract The erosion of ductile metals by angular abrasive particles at grazing angles of incidence is generally accepted as being due to a cutting mechanism. By contrast, a number of widely different mechanisms have been proposed to explain erosion at perpendicular or near-perpendicular angles of impingement. In the present work the influence of the roughness of an eroded surface is examined. It is shown that measurements of surface profile may be combined with the analysis of a grain striking a smooth surface to predict the value of erosion for globally perpendicular impact.

On the formation of surface ripples during erosion

Abstract An interesting, but hitherto unexplained, aspect of erosive wear by solid particles is the regular ripple pattern which often forms on the eroded surface. A mechanism by which these ripples may arise is proposed and the parameters which govern ripple growth and size are obtained. Observations of ripple formation confirm various aspects of the theory.

Measurement of Near Surface Residual Stresses Using Electric Discharge Wire Machining

It has been shown that near surface residual stresses may be deduced form surface strains produced by making a cut of progressively increasing depth. The process of electric discharge wire machining (EDWM) greatly improves the ability of the method to resolve a stress gradient near the surface. However, the EDWM process may also introduce residual stresses

Measurement of Residual Hoop Stresses in Cylinders Using the Compliance Method

A method is proposed for measurement of the hoop stress in an axisymmetric residual stress field in cylinders in which the axial stress is independent of the axial coordinate. The method involves measuring strains at the outside surface while an axial crack is cut progressively from the outside. Experimental results are presented for two short cylindrical rings cut from a long quenched cylinder. Good general agreement is obtained with X-ray and hole drilling measurements of residual stresses.