DEFORMATION OF SHAPE-MEMORY ALLOYS DUE TO THERMOINDUCED TRANSFORMATION

In this paper, a macro-scale, phenomenological constitutive model for shape memory alloys is used in conjunction with energy balance equatio ns to study the evolution of temperature and deformation profiles seen in SMA wires under specific thermal and mechanical boundary condition s. The general, fully coupled thermo-mechanical problem is formulated and analytical solutions are determined for the decoupled case and lim it cases. Results for two specific initial/boundary value problems are presented here: 1) resistive heating of an SMA wire-initial detwinned martensite leads to strain recovery (contraction) on heating; 2) defo rmation wave in a semi-infinite, initially austenitic SMA wire cooled at the boundary-deformation zone propagates and expands as the wire tr ansforms to martensite (expansion). In both cases, the region and exte nt of transformation is identified, indicating the magnitude of actuat ion obtained. Implications of the modeling for the active control of s tructures are discussed.