PSEUDOELASTICITY OF TINI SHAPE-MEMORY ALLOY (DEPENDENCE ON MAXIMUM STRAIN AND TEMPERATURE)

In order to investigate the basic properties of pseudoelasticity of TiNi shape memory alloy, tensile tests with various maximum strains at constant temperature were performed. Based on the experimental results, dependence of the stress-strain curve in the pseudoelastic region on maximum strain and temperature was discussed. The results are summarized as follows. If maximum strain occurs in the stress-induced martensitic (SIM) transformation region, the reverse transformation stress assumes a constant value at each temperature. The modulus of elasticity decreases in proportion to maximum strain. This occurs due to the fact that the fraction of the martensitic phase increases. The residual strain increases in proportion to the amount of SIM transformation strain and temperature. The dissipated strain energy increases in proportion to the amount of SIM transformation strain, but depends slightly on temperature. The recoverable strain energy increases in proportion to maximum strain and temperature.