Finite Element Analysis Investigating the Sliding Contact of a Shape Memory Alloy Substrate

Abstract

Recent experimental wear tests have demonstrated that shape memory alloys offer better wear resistance than conventional wear resistant materials and therefore make them ideal candidates as tribological materials. The wear resistance of shape memory alloys has been attributed to its pseudoelasticity and high yield strength. To date however, an extensive computational study that simulates the contact behavior of these alloys during a typical sliding wear process has not been investigated. This study uses the finite element method to analyze the sliding contact behavior between a rigid cylinder and a two dimensional shape memory alloy semi-infinite half-space. An experimentally validated constitutive model is used to capture the pseudoelastic effect exhibited by these alloys. The finite element contact model is validated with closed form solutions for well known normal and sliding elastic contact problems. Parametric studies involving key shape memory alloy material parameters (maximum recoverable transformation strain, the inherent difference between the elastic moduli of martensite and austenite phase, various isothermal loading paths) and coefficients of friction are conducted to study the effects on the sliding response. It is shown that the sliding response of SMAs is strongly temperature dependent, with significant residual stresses present in the half-space at temperatures below the austenitic finish temperature. An increase in the maximum transformation strain causes the stress distribution to be spread over a wider area and causes a significant decrease in the maximum von Mises stress in the half-space. The ability of shape memory alloys to undergo a stress induced transformation to a more compliant phase, also causes a reduction in the Mises stress and further demonstrates why pseudoelastic SMAs offer better wear resistance that conventional wear resistant materials.