A constitutive model for cyclic actuation of high-temperature shape memory alloys

Abstract

In this work, a three dimensional constitutive model for High Temperature Shape Memory Alloys (HTSMAs) is presented. To describe the evolution of the cyclic actuation behavior of such alloys, viscoplastic mechanisms and transformation induced plasticity are introduced in addition to the classical transformation behavior of Shape Memory Alloys. Based on contin- uum thermodynamics, the evolution of phase transformation, plasticity induced transforma- tion, retained martensite and viscoplasticity are described. Deformation mechanisms that occur over the operational range of such HTSMAs have been identified from the thermome- chanical behavior of a NiTiPd alloy. The proposed model has therefore been validated based on the prediction of the thermomechanical behavior of the studied NiTiPd HTSMA alloy under di↵erent loading conditions. Careful attention is devoted to the calibration procedure to identify the contribution of the di↵erent mechanisms independently. Finite element anal- ysis (FEA) is performed to demonstrate the capabilities of the model to describe the cyclic behavior of HTSMA devices.