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The low-cycle fatigue of a TiNi shape memory alloy was investigated by the rotating-bending fatigue tests in air, in water and in silicone oil. (1) The influence of corrosion fatigue in water does not appear in the region of low-cycle fatigue. (2) The temperature rise measured through an infrared thermograph during the fatigue test in air is four times as large as that measured through a thermocouple. (3) The fatigue life at an elevated temperature in air coincides with the fatigue life at the same elevated temperature in water. (4) The shape memory processing temperature does not affect the fatigue life. (5) The fatigue equation is proposed to describe the fatigue life depending on strain amplitude, temperature and frequency. The fatigue life is estimated well by the proposed equation. [S0094-4289(00)01102-6]

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The influence of the strain rate on the superelastic behaviour associated with the martensitic transformation is investigated by tensile tests for TiNi shape memory alloy. The results are summarized as follows. The increase in the temperature due to the stress-induced martensitic transformation measured by a non-contact method is an order of magnitude larger than that measured through a thermocouple. The increase in the transformation stress associated with an increase in the strain rate appears to be due to the temperature rise. The superelastic behaviour depending on the strain rate is well expressed by the proposed constitutive equation considering the temperature variation. The proposed equation is useful for the design of superelastic elements.

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