Correlation of Experimental Erosion Data with Elastic‐Plastic Impact Models

Abstract

Five target materials of varying mechanical properties were eroded with natural quartz sand and S i c particles. The targets were four commercially available Si3N, materials and MgF,. Several particle size ranges between 10 and 1000 pm. accelerated to several velocities between 61 and 275 m/s, were used for erosion testing. The erosion results are presented in terms of two models which have been developed for elastic-plastic impact damage. ECENT investigations have shown that R a number of erosion mechanisms for ceramics can exist and that erosion and impact is a complex process.'-4 Essentially, two types of models have been proposed for solid-particle impact (single particle) and erosion (multiparticle) of brittle materials. The earlier models were based on elastic interaction between target and particle, and predicted that material removal occurs by the intersection of ring cracks on the target surface. This process has been observed on several materials under static and low-velocity impact conditions with relatively large spherical particle^.',^ More recent analysis has treated static and dynamic plastic indentation, which is characterized by plastic deformation of the contact area between the particle and the target, with radial cracks propagating outward from the contact zone, and with subsurface lateral cracks propagating outward on planes nearly parallel to the surface. This type of damage, termed elastic-plastic, is observed for impact with angular particles of generally greater hardness than the target.',2Two expressions have been derived for elastic-plastic impact.5,6Details of the derivations are given in the references. Generally, the expressions relate erosion to the depth of damage and area of lateral cracking.The expressions are as follows:(2) ppl I /19R I 1 /lv,22/9Kc-4/3HI/9after Ruff and Weiderhorn,"where V=erosion volume loss per impact p,=particle density pc= target density p,=particle shear modulus p,=target shear modulus R,=particle radius vp=particle velocity K,= target fracture toughness H = target hardnessThe major differences between the two expressions are in the particle density, particle velocity, and target hardness dependencies. These expressions are based on single impacts and were developed for isotropic materials under idealized conditions. The validity of the above expressions to predict erosion can be assessed by comparing a plot of experimental erosion data as a function of the expressions.Five target materials were eroded with Sic and quartz particles. The targets were hot-pressed Si,N4, pressureless-sintered Si,N,,, two reaction-bonded Si,N,'s, and MgFZ. Properties relevant to erosion are Table I. Target and Particle Properties shown in Table I. Particle properties are also given. Six particle sizes between 10 and 385 pm average of quartz particles and 8 and 940 pm average of Sic particles were used for erosion testing. Between three and five particle velocities for each particle size were evaluated. Velocities ranged between 61 and 275 m/s. All tests were performed at 90" ...

Indentation analysis: applications in the strength and wear of brittle materials

“…(8), relative to the square root dependence in strength equations). Furthermore, the scatter in erosion data is such that it is difficult to distinguish between different theories (Gulden, 1981;Wiederhorn & Hockey, 1982). Nevertheless, all such theories lead to more or less the same main conclusions, that the wear rate increases with particle kinetic energy and diminishes with material toughness, as intuitively expected.…”

Indentation Fractography: A Measure of Brittleness

“…For contacts in impact loading, Pi can be eliminated in favor of incident kinetic energy U i (via an appropriate contact equation) [58] to obtain an erosion equation. The most important predictions of this model, concerning the manner in which the removal rate increases with contact load or energy and decreases with material toughness, have been confirmed in extensive experimental studies on erosive wear in brittle glasses and ceramics [66][67][68][69].…”

“…Of the crack systems discussed in sections 2 and 3 it is the lateral which constitutes the most effective chipping mode [1] (although the cone crack can also be effective in this regard, especially when overlap between adjacent contact sites is frequent). These removal processes can be either highly deleterious or highly beneficial, depending on whether one is seeking to minimize or to maximize the removal process; that is, whether one is concerned with erosive wear [66][67][68][69] or with machining [70J properties.…”

Micro-grooving on quartz crystals by an abrasive air jet

“…Finnie [27] studied the effect of spherical particles on brittle materials and reported that the velocity and impact angle of particles are the primary factors for the erosion of brittle materials, although he stated that to a different degree, particle size, shape, hardness, and strength are also important. Gulden [32,33] studied the effects of soft silica particles on silicon nitride. The author observed that no lateral fracture propagated due to impact and, therefore, suggested that the energy of the particle changed to the plastic deformation of the particles themselves and erosion was due to minor chipping.…”