Damping Properties of Shape Memory Alloys for Seismic Applications

Abstract

Shape memory alloys (SMAs) in martensitic form and austenitic form are studied to evaluate their damping potential for applicat ions in earthquake engineering. Shape memory alloy wires and bars are subjected to cyclical loading s similar to that expected during a seismic event. The damping properties of the shape memory alloy s in both the martensitic form and austenitic form are c ompared with respect to bar size, loading rate, and maximum strain cycle. The results show that in the superelastic form, the damping properties of shape memory alloys are generally low, ranging from 2%-7% equivalent viscous damping. The damping properties generally peak at 4%5% strain and begin to degrade at larger strains . In the martensitic form, shape memory alloys have significant energy dissipation with equivalent viscous damping ratios ranging from 15%-25%. Strain rate effects are evaluated by loading the bars at rates up to 2Hz (maximum strain rate of 7.90% per second). The results show that increased strain rates lead to a red uction in the energy dissipation capabilities of shape memory alloys in both forms. The effectiveness of using shape memory alloys for damping applications is evaluated through a comparison with current passive energy dissipation technology in the field of earthquake engineering showing the viability of using shape memory alloys for passive damping applications.