Modeling the Influence of Strain-Rate in Superelastic Shape Memory Alloys

Abstract

Shape Memory Alloys (SMAs) are materials with appealing properties. They have the ability to recover stress-induced strains performing the superelastic effect, ideally resulting in insignificant residual strain (re-centering capability). A dependency of their behavior, exhibiting different hysteresis loops, has been reported on temperature and loading rate variations, maximum deformation, material composition and treatments. Presenting a wide applicability potential, SMAs have been intensively investigated in various sectors possessing a considerable place in structural engineering. Studies have been published developing constitutive models to simulate their behavior presenting some drawbacks: the inability to capture the ratedependent nature, the large number of parameters, complexity and difficulty of implementation. In this context, a uniaxial rate-dependent constitutive model based on Graesser and Cozzarelli model for superelastic SMAs, aimed at capturing their essential hysteretic response has been developed. After the verification of the model prediction comparing it with experimental data derived from literature, a comparison with the rate-independent model of Auricchio and Sacco (1997) is attempted to indicate the effect of the rate-dependency. Results showed that the proposed model managed to successfully simulate the influence of strain rate using a simple equation rendering feasible the potential implementation of a robust solution algorithm easy to program in commercial software constituting a valid and effective computational tool for the analysis of superelastic SMAs.