Numerical study of pseudoelastic shape memory alloy helical springs

Shape memory alloys (SMA's) are a class of smart materials with the intrinsic properties of shape memory effect (SME) and pseudoelasticity (PE) due to their solid-solid martensitic phase transformations under various thermomechanical loadings. Due to these features, SMA's have been used in many engineering fields such as biomedical, aerospace, and robotics in various forms including spring as actuator elements. In this paper, the pseudoelastic response of SMA helical springs under an axial force is studied numerically. An enhanced one-dimensional constitutive model is assumed to describe the shear stress-strain response within the coils, and equilibrium as well as geometric consistency is utilized to evaluate the axial response of an SMA spring. The numerical results are shown to be in a good agreement with available experimental data indicating validity of the proposed approach. The effects of variations in the material parameters on the axial force-displacement response of an SMA spring are further investigated.

Keywords:

Shape memory alloy , SMA , spring , Constitutive equation , Numerical solution