Coupled Thermomechanical Analysis of Shape Memory Alloy Actuator

Abstract

AbstractThe shape memory alloys (SMAs) exhibit large displacement and force capabilities due to the stress and temperature-dependent martensitic phase transformation inside them. Modeling its behavior accurately requires coupled thermomechanical analysis, considering latent heat term during phase transformations, thermoelastic heat terms, thermal and mechanical loading, boundary conditions, etc. Moreover, the variation of material properties, e.g., modulus of elasticity, thermal expansion coefficient, specific heat, during phase transformation also significantly affects the simulation results. In this work, both the stress and thermal equilibrium equations are solved simultaneously in an incremental finite element framework, taking into account all the terms mentioned above. The constitutive model of SMA, as proposed by Qidwai and Lagoudas (Int J Numer Methods Eng 47:1123–1168, [1]), has been considered here. The developed FE model has been able to predict the coupled response of an SMA actuator accurately, under different thermomechanical boundary conditions. Finally, the response of a non-uniform SMA actuator is simulated considering resistive heating, and it is found that the presence of non-uniformity significantly affects the thermal and mechanical response of the SMA actuator, particularly during partial phase transformations. The simulation results also demonstrate the need of coupled analysis while modeling SMA behavior.KeywordsShape memory alloyCoupled thermomechanical analysisSMA actuatorMaterial non-linearity