A Phenomenological Model for Superelastic Shape Memory Alloy Helical Springs

Due to their capabilities of large recoverable deformation, energy dissipation and self-recovery, Nitinol superelastic shape memory alloy (SMA) helical springs can be used as base isolation components to protect isolated structures. In such applications, to design the specific isolation component which consists of SMA helical springs, it is essential to study the force-displacement relationship model of the SMA springs under cyclic loading. In this paper, two types of SMA springs are trained using Nitinol superelastic SMA wires. Based on the data of a series of cyclic loading tests, a phenomenological model is established to model the superelasticity or pseudoelasticity of the SMA springs. The developed model describes the force-displacement relationship of SMA springs subjected to general dynamic load. Comparative studies show that for the proposed phenomenological model, the simulation results of force-displacement relationship of the SMA springs agree very well with the experimental ones, which demonstrates the effectiveness of the proposed model.