PHENOMENOLOGICAL ANALYSIS ON SUBLOOPS AND CYCLIC BEHAVIOR IN SHAPE-MEMORY ALLOYS UNDER MECHANICAL AND OR THERMAL LOADS

A theoretical framework is presented, from the phenomenological point of view, for the cyclic uniaxial deformation in shape memory alloys subjected to the thermal and/or mechanical loads by introducing three internal variables; the local residual stress and strain and the volume fraction of the martensic phase accumulated during cyclic forward and reverse martensitic transformations. The cyclic effect on the stress-strain and strain-temperature hysteresis loops is discussed. The subloops due to incomplete transformations are also analyzed by assuming the transformation starting stress or temperature which depends on the preloading. Numerical results explain qualitatively well the observations on the thermomechanical behaviors of shape memory alloys.