Microscopic and Mesoscopic Evaluations of Materials. Multi-axial Constitutive Equations of Polycrystalline Shape Memory Alloy(1st Report, Modelling and Formulation).

Abstract

Quite unique and interesting behaviors of shape memory alloy under complex loading conditions, including the complicated path dependency, have been observed in systematic experiments by applying some combiened loads of axial force and torque to the thin-walled tubular specimen of Cu-based polycrystalline shape memory alloy. A set of constitutive equations is proposed, which can describe the complicated behaviors observed in the experiments. The mesoscopic approach is employed in the formulation because the complicated behaviors are closely related with the microstructural changes of materials, and the obtained equations show a reasonable coincidence with the exprimental results. In this first paper, the process of modelling and the detail of formulated constitutive equations are described, and the comparison between experimental resutls and computed results by using the proposed constitutive equations are shown in the second report.