OS0909 Ti-50.4at%Ni形状記憶合金の疲労寿命特性に及ぼす表面処理の影響

Abstract

In this study, the effects of surface smoothness on fatigue characteristics of Ti-50.4at%Ni shape memory alloy (which is used as self-expanding stent) wire are investigated. The Ti-Ni specimen is a wire 1mm in diameter. The surface smoothness is varied by the physically polishing and electro-polishing. The surface and fractured surface are observed by scanning electron microscope (SEM). The surface of electro-polished specimen is smoother than the other specimen. The fatigue characteristics of specimen is investigated by the rotary bending tests in the water kept 310K. The applied vending strain (ε_<ap>) is varied from 1 to 6% in this study. When the ε_<ap>, is above 3%, fatigue characteristic of electro-polished specimen is better than the other specimen, while ε_<ap> is below 3%, physically polished specimen also become good as well as fatigue characteristic of electro-polished specimen. Furthermore, the fracture origins of all specimen are found on the surface of each specimen. In consequence, fatigue characteristics are improved with increasing of the surface smoothness.