A discrete particle model study of the effect of temperature and geometry on the pseudoelastic response of shape memory alloys

Abstract

In this paper, the effects of temperature and geometry on the hysteresis behavior of shape memory alloy (SMA) under stress induced transformations are studied. We used a discrete model referred to as the constitutively informed particle dynamics (CPD), for the analysis. The CPD approach uses a multibody interaction derived from a polyconvex free energy appropriate for phase transforming materials. This approach is able to describe evolution of the phases in a sharp interface paradigm. Using such an approach allows discrete element models to describe complex material behavior such as phase transformations which were hitherto not possible. The temperature dependent pseudoelastic response is studied under uniaxial tension. The effect of temperature on this stress induced transformation is studied at four different temperatures. The results show an increase in hysteresis at higher temperatures. Next, the effect of geometry on hysteresis is studied in a tapered bar geometry. Tapered bars show hardening in the stress–strain curve. The influence of temperature and specimen geometry on the pseudoelastic stress–strain response would be essential to design and develop MEMS (Micro-Electro-Mechanical Systems) applications using these classes of smart materials.