A Constitutive Model of Shape Memory Alloys with Consideration of Martensitic Hardening Effect

Shape memory alloys (SMAs) exhibiting remarkable thermo-mechanical behaviors, such as the shape memory effect and superelasticity, have attracted much attention in the past decades. This paper presents experimental characteristics and a constitutive model of superelastic Nitinol SMAs for potential vibration damping applications in earthquake engineering. The proposed constitutive equation improves the Graesser and Cozzarelli's model and is capable of modeling the martensitic hardening effect under large amplitudes, critical for structural 'fail-safe' design for extreme loads. To verify the effectiveness of the proposed constitutive model, experiments on a superelastic NiTi wire with different strain levels were conducted. Comparisons between experimental and numerical results predicted by the proposed model show that observed and modeled behavior are in close agreement.