Effect of Loading Rate on the Superelastic Behavior of SMAs Under Multi-axial Loading Conditions; Analytical Modeling and Experiment

摘要

Multi-axial behavior of shape memory alloy (SMA) bars with circular cross section is studied by considering the effect of temperature gradient in the cross section as a result of latent heat generation and absorption during forward and reverse phase transformations. The local form of energy balance for SMAs by taking into account the heat flux effect is coupled to a closed-form solution of SMA bars subjected to multi-axial loading. Non-Mises definitions are employed for the effective stress and strain to enable the model to capture the coupling between tension and torsion. The resulting coupled thermo-mechanical equations are solved for SMA bars with circular cross sections. A number of experiments were conducted and the results were then successfully compared with the model. It is shown that the isothermal solution is valid only for specific combinations of ambient conditions and loading rates. The present approach is a beneficial platform in modeling and analysis of applications with high loading rates.