Experimental cyclic plasticity characterization of iron-based shape memory alloys for seismic applications

This paper presents experimental findings on the inelastic cyclic behaviour of iron-based shape memory alloys (Fe-SMAs), focusing on their potential use in seismic applications. The research employed loading protocols that replicated the strain amplitudes, ranges, and rates, typically observed during earthquake loading conditions, to examine the primary characteristics of rate-independent and rate-dependent cyclic plasticity. It is shown that the material demonstrates a stable and symmetrical stress-strain hysteresis behaviour. At quasi-static loading rates, the material exhibits a strong resemblance to mild steel in terms of kinematic and cyclic hardening. Specifically, a stable hysteresis loop can be achieved within a few cycles of straining, and isotropic hardening depends mainly on the accumulated plastic strain. At higher loading rates, viscoplasticity and thermal effects influence the hardening response. It is shown that seismic-induced straining could cause surface temperatures to exceed 200°C. The impact of post-test thermal activation on the cyclic behaviour is also investigated. The study is further extended to the fabrication and testing of energy dissipaters using multi-fuse and grooved Fe-SMA cores encased in stainless steel tubes, demonstrating stable hysteresis response prior to buckling, and a minimum cyclic average strain capacity of 10 %. • Response of Fe-SMA under earthquake representative uniaxial loading is studied. • Rate-independent and rate-dependent cyclic plasticity characteristics are discussed. • Fe-SMA demonstrates a stable and symmetrical stress-strain hysteresis behaviour. • The effect of heat treatment on the cyclic response prior to retesting is examined. • Buckling-restrained dampers with Fe-SMA cores could show a stable cyclic behaviour.