Two-way shape memory effect of a Ti rich NiTi alloy: experimental measurements and numerical simulations

In this paper the two-way shape memory effect (TWSME) of a Ni-51 at.% Ti alloy is investigated and a numerical model is developed, which allows real time simulations of its hysteretic behaviour strain versus temperature. The two-way shape memory effect (TWSME) was induced through a proper thermo-mechanical training, carried out at an increasing number of training cycles and for two values of training deformation. The TWSME was measured under different applied stresses and the hysteretic behaviour in the strain-temperature response was recorded. In order to evaluate the thermal stability of the hysteresis loops the material was subjected to many cycles, by repeated heating and cooling, between A(f) (austenite finish temperature) and M(f) (martensite finish temperature). The numerical method is based on a phenomenological approach and was developed in a Matlab (R) function, which calculates the model parameters from a set of experimental data, and a Simulink (R) model, which is efficient enough for use in real time applications. The accuracy of the proposed model was analysed through systematic comparisons between experimental measurements and numerical predictions.