One dimensional constitutive model with transformation surfaces for phase transition in shape memory alloys considering the effect of loading history

Abstract

Existing constitutive models for Shape Memory Alloys (SMAs) assume that both forward and reverse transformations occur when the thermodynamic driving force reaches a specific amount regardless of loading history. In this article, these assumptions are examined, and some cases are introduced where these models predict contradictory results. The effects of initial martensitic volume fraction on both forward and reverse transformations are shown by carrying out simple tensile tests on SMA wires. In line with these experiments, a one-dimensional constitutive model with new transformation conditions is proposed phenomenologically in order to model pseudoelastic behavior. The constitutive model is proved to be consistent with the theory of continuum mechanics. New transformation surfaces are introduced to govern transformations start conditions, rather than using preexisting common phase diagrams. As a result, history-dependent transformation start temperatures are determined. The obtained experimental stress-strain diagrams, available DSC test results, and experimental strain-temperature responses are used to validate the proposed model. It is shown that loading history affects transformation start conditions.