Experimental investigation and modeling of the loading rate and temperature dependent behavior of a high performance SMA

This study explores the superelastic behavior of a recently developed Ni45.3Ti29.7Hf20Pd5 alloy that has favorable mechanical properties (high strength and hysteresis) over the well-known shape memory alloys. The effects of aging on shape memory properties of Ni45.3Ti29.7Hf20Pd5 polycrystalline alloys are revealed first. Next, the dependence of the superelastic response of an aged Ni45.3Ti29.7Hf20Pd5 alloys on the strain amplitude, loading rate and test temperature are examined via uniaxial compression tests. Then, the superelastic response of a solutionized sample is compared with that of the aged sample. Finally, a soft computing approach that employs neural networks and fuzzy logic is used to model the highly nonlinear behavior of Ni45.3Ti29.7Hf20Pd5 alloys by considering the loading rate and temperature effects. The tests results show that solutionized sample has wider stress hysteresis, larger energy dissipation and the equivalent viscous damping than the aged sample. It is found that loading rate does not significantly influence the superelastic behavior of NiTiHfPd. In addition, an increase in temperature shifts the hysteresis loops upward but result in no considerable change in damping characteristics. 2