Shape memory alloys (SMAs) are a relatively new class of functional materials, exhibiting special thermo-mechanical behaviors, such as shape memory effect and superelasticity, which enables their applications in seismic engineering as energy dissipation devices. This paper investigates the properties of superelastic shape memory alloys and highlights the influence of strain rate on superelastic behavior under various strain amplitudes by cyclic tensile tests on NiTi SMA wires. A novel constitutive equation is proposed to describe the strain-rate dependent hysterestic behavior of superelastic SMAs at different strain levels. This development is based on the Graesser and Cozzarelli's model, which has the advantage of simplicity. To verify the effectiveness of the proposed constitutive equation, experiments on a superelastic NiTi wire with different strain rates and strain levels are conducted. Experimental results and the numerical simulation based on the proposal constitutive equation are in close agreement. The results in this paper are useful for future design of superelatic SMA-based energy dissipation devices for seismic protection of structures.

Date Published: 1 November 2007
PDF: 8 pages
Proc. SPIE 6423, International Conference on Smart Materials and Nanotechnology in Engineering, 64230O (1 November 2007); doi: 10.1117/12.779311

Published in SPIE Proceedings Vol. 6423:
International Conference on Smart Materials and Nanotechnology in Engineering
Shanyi Du; Jinsong Leng; Anand K. Asundi, Editor(s)