The two way shape memory effect of shape memory alloys: an experimental study and a phenomenological model

The paper presents a macroscopic description for the simulation of the two way shape memory effect (TWSME) of shape memory alloys (SMA), and is an extension of a previous work dealing with the global thermomechanical behavior of SMA. The model is set in the framework of the thermodynamics of irreversible processes. Two internal variables are taken into account : the volume fraction of self-accommodating (pure thermal effect) and oriented (stress-induced) product phase. A term dedicated to the modeling of the trained SMA is added to the specific free energy derived for the non-trained SMA. This term φed, depends on the thermomechanical procedure of training submitted to the sample. In the present case, it accounts for the stress tensor σed applied during thermal cycling. The parameters of the model have been identified for a Cu–Zn–Al SMA, and the simulated results show good agreement with experiments.