Constitutive Modeling of Shape Memory Alloy Including Martensite-transformation-induced Plasticity

The stress-strain curves of as-received shape memory alloys (SMAs), which are often used as sensors or/and actuators, vary among cyclic loadings. This phenomenon is caused by an irreversible process induced by the martensite transformation. To reproduce it mathematically, the one-dimensional phase transformation model previously proposed by the present author and his coworkers is developed. Specifically, new phases composed of the austenitic phase and the residual martensitic phase are introduced. To verify the validity of the model, cyclic tensile loading tests of as-received superelastic SMA wires are carried out and the measured stress-strain curves are compared with those obtained by calculation. The result shows that the present model can reproduce the variation of the stress-strain curve for the first several cycles with reasonable accuracy.