A one-dimensional strain-rate-dependent constitutive model for superelastic shape memoryalloys

Abstract

Recently, there is increasing interest in using superelastic shape memory alloys (SMAs) incivil, mechanical and aerospace engineering, attributed to their large recoverable strainrange (up to 6–8%), high damping capacity, and excellent fatigue property. In this research,an improved Graesser’s model is proposed to model the strain-rate-dependent hystereticbehavior of superelastic SMA wires. Cyclic loading tests of superelastic SMA wires arefirst performed to determine their hysteresis properties. The effects of the strainamplitude and the loading rate on the mechanical properties are studied andformulated using the least-square method. Based on Graesser’s model, an improvedmodel is developed. The improved model divides the full loop into three parts:the loading branch, the unloading branch before the completion of the reversetransformation and the elastic unloading branch after the completion of reversetransformation, where each part adopts its respective parameters. Numerical simulationsare conducted using both the original and the improved Graesser’s models. Comparisonsindicate that the improved Graesser’s model accurately reflects the hysteresischaracteristics and provides a better prediction of the SMAs’ actual hysteresis behaviorthan the original Graesser’s model at varying levels of strain and loading rate.