Shape‐Memory Alloys as New Materials for Aseismic Isolation

Abstract

New results are presented in the area of hysteretic modeling and experimental characterization of shape memory alloys (SMAs). A stress‐induced micromechanical phase transition occurs in SMAs that causes inelastic deformation and gives rise to a large energy‐absorbing capacity. Because it is possible to achieve large hysteretic deformation in SMAs without incurring plastic deformation, SMAs have potential for use in earthquake‐engineering passive damping schemes. In order to represent such energy‐absorbing behavior, an existing one‐dimensional model of hysteresis is modified to include the macroscopic characteristics of SMAs. Also, the results of cyclic material‐characterization tests applied to a nickel‐titanium SMA known as Nitinol are presented. Hysteretic behavior closely resembling that of the superelastic material was obtained in the laboratory for cyclic strain levels up to 4.5%. The model of SMA behavior is also compared to the cyclic responses of Nitinol.