FEM prediction of the pseudoelastic behavior of NiTi SMA at different temperatures with one temperature testing results

In this paper, a finite element method (FEM) has been applied to predict the pseudoelastic behavior of NiTi shape memory alloys at different temperatures with only one temperature testing results. A three-dimensional micromechanical model has been developed based on Gall and Lim's expression for Gibbs free energy. The difference of elastic properties between austenite and martensite are taken into consideration. The formulations for the evolution of volume fraction of the 24 martensite variants are derived. The time-discrete evolutionary equations are presented with the expression of the mechanical Jacobian matrix. This model has been implemented as UMAT into ABAQUS, which is used to simulate the pseudoelastic behavior by aggregate grains. The grain number in the aggregate is big enough to have little influence of the grain number on the simulated behavior. Tensile experiments are performed at 28, 35 and 50 °C. The experimental results at 35 °C are used to validate the pseudoelastic model and derive the model parameters, which are used to predict the pseudoelastic behavior at 28 and 50 °C. Two kinds of predictions are presented. One considers different elastic modulus at different temperatures. And the other uses the same elastic modulus at different temperatures. Both show satisfactory agreement with the experimental results.