On the Formation and Propagation of Macroscopic Martensitic Front in Shape Memory Alloy Wire

Abstract

In the present paper we investigate the conditions under which the formation of a martensitic phase transformation front in a shape memory alloy (SMA) sample is possible at a macroscopic level. The phenomenon is a result of the interplay between thermal and mechanical effects. Specifically, it is shown that the shape memory materials exhibiting negligible or weak transformation hardening are prone to macroscopic transformation front formation. However, the constitutive law that regulates internal hysteresis loops formation is responsible for the internal structure of the propagating front. The phase transformation kinetics is dependent, among others, on the crystalline state of the sample (monocrystalline versus polycrystalline), its chemical composition and thermo-mechanical treatment. The present investigations are based on numerical simulations performed for a NiTi wire with the aid of finite element method. Thermo-mechanical coupling effects are taken into account during numerical simulation experiments.