Finite element calculation of load-biased thermal cycling of shape memory alloy

Inhomogeneous deformation is one of the essential characters of shape memory alloy. Specimen is composed of many variants which have different strain. There exist a phase interface between two different phases and its mobility will depend on several factors such as curvature and orientation of the interface. The shape memory alloys exhibit hysteresis and one of the main reasons to cause hysteretic behavior is thought to be the internal inhomogeneity. It is thought that the phase interfaces display irregularities in the motion and the resultant state is metastable one which requires a very long relaxation time. In this work, spatially inhomogeneous frictional force to the volume change of the variants is assumed to account for the irregular behavior of the phase transformation. Its effect on the production of the macroscopic strain of a shape memory alloy is investigated using finite element calculation. Load-biased thermal cycling of a shape memory alloy is considered. The numerical result is compared with experimental data of Ti-44.5Ni-5Cu-0.5V (at.%) alloy. A better agreement is obtained for the experimental data when the inhomogeneous friction is assumed.