A simple R-phase transformation model for engineering purposes

For in vivo biomedical applications of shape memory alloys, actuators based on the R-phase/austenite transformation as present in certain TiNi alloys are particularly suited. Numerical modeling and optimization can improve the design of such actuators. In this paper, a one- and three-dimensional constitutive model for this R-phase/austenite transformation is presented. In contrast to previous work, its formulation is particularly directed towards the efficiency in finite element based design optimization, next to its agreement with experimental data. Important features of this model are its simplicity, an explicit stress–strain relationship and its path-independence.