超音波ショットピーニングによるTiNi形状記憶合金線材の疲労寿命向上

抄録

The fatigue property of shape memory alloy (SMA) is one of the most important subjects in view of evaluating functional characteristics of SMA elements. In the present paper, the ultrasonic shot peening (USP) was applied to induce the compressive residual stress on full surfaces of TiNi SMA wire. The influence of USP on the bending fatigue life was investigated. The results obtained are summarrized as follows: (1) Stress level in the tensile test increases slightly by USP. (2) If SMA was treated by the USP, the fatigue life becomes longer. The larger the bending strain amplitude, the shorter the fatigue life is. (3) The surface hardness of SMA wire becomes harder by USP. (4) The fatigue crack nucleates at the internal specimen near the surface of the USP-treated layer.