Elasto-plastic hemispherical contact models for various mechanical properties

Abstract

This work uses the finite element technique to model the elastoplastic deformation of a hemisphere contacting a rigid flat for various material properties typical of aluminium, bronze, copper, titanium and malleable cast iron. Additionally, this work conducted parametric finite element method (FEM) tests on a generic material in which the elastic modulus and Poisson's ratio are varied independently while the yield strength is held constant. A larger spectrum of material properties are covered in this work than in most previous studies. The results from this work are compared with two previously formulated elastoplastic models simulating the deformation of a hemisphere in contact with a rigid flat. Both of the previously formulated models use carbon steel mechanical properties to arrive at empirical formulations implied to pertain to various materials. While both models considered several carbon steels with various yield strengths, they did not test materials with various Poisson's ratios or elastic moduli. The previously generated elastoplastic models give fairly good predictions when compared with the FEM results for various material properties from the current work, except that one model produces more accurate predictions overall, especially at large deformations where other models neglect important trends due to decreases in hardness with increasing deformation.

The effect of contact conditions and material properties on elastic-plastic spherical contact

“…They provided convenient dimensionless expressions for the contact load, contact area and mean contact pressure, covering a wide range of interferences for a single value of the Poisson's ratio (ν = 0.3). Similar results were then obtained by Quicksall et al [2004] and Jackson and Green [2005]. Etsion et al [2005] studied the process of loading-unloading of an elastic-plastic loaded sphere in contact with a rigid flat under perfect slip condition.…”

An analysis of three-dimensional elasto-plastic sinusoidal contact

“…Jackson and Green [14] also provide a more complicated model which may describe large deformations better than the Kogut and Etsion (KE) model. However, Quicksall et al [15] found that the Jackson and Green and KE model agree fairly well for small deformations and the KE model is also much easier to algebraically manipulate. For these reasons, the KE model is used in the current work to model the initial elasto-plastic deformation of the sinusoidal surfaces.…”

A Comparison of the Predictions of a Finite Element Model and Multiscale Model for a Rough MEMS Electrical Contact

“…It is also worth noting that the pressure is actually greater than the value of 2.8·S y that is often rounded up to 3·S y and used to approximate the real contact area [21]. The contact pressure is up to 16% higher than 2.8·S y , As is noted in other works, for some surfaces this pressure can even be much greater than 3·S y [6,12,[22][23][24][25][26][27][28] or sometimes even less [29][30][31]. Most rough surface contact models do not succeed at predicting this.…”