ニッケルチタン形状記憶合金の超弾性サイクル試験における機能疲労

抄録

Nickel Titanium shape memory alloy exhibits shape memory effect and superelasticity. In general, the superelasticity of commercial NiTi wire is around 7% in elongation and the superelastic strain becomes less than the original value after the repetition of superelasticity cycles. Eggeler et al. (2004) called the decrease “functional fatigue”. In this paper superelasticity was repeated for more than 100 times in a wide range of temperature and load. We found that the plateau stress of the stress-induced transformation decreased but that of strain reversal did not change. We also found that the superelasticity strain decreased faster as the temperature was higher. It is suggested that the change is a typical autocatalytic process.