Thermomechanical behavior of shape memory alloy under complex loading conditions

The thermo-mechanical behavior of polycrystalline shape memory alloy (SMA) under multi-axial loading with varying temperature conditions has been stud ied by experiments. Recently the research has been extended theoretically a nd a mechanical model of polycrystalline SMA and the corresponding mesoscop ic constitutive equations have been developed. The model presented in this paper is constructed on the basis of the crystal plasticity and the deforma tion mechanism of SMA. The variants in the crystal grains and the orientati ons of crystal grains in the polycrystal are considered in the proposed mod el; the constitutive equations are derived on the basis of the proposed mod el. The volume fraction of the martensite variants in the transformation pr ocess and the influence of the stress state on the transformation process a re also considered. Some calculated results obtained by the constitutive eq uations are presented and compared with the experimental results. It is fou nd that the deformation behavior of SMA under complex loading conditions ca n be well reproduced by the calculation of the constitutive equations. (C) 1999 Elsevier Science Ltd. All rights reserved.