Effects of water environment and temperature on fatigue bending strength of Ni-Ti super elastic wire

Abstract

Fatigue bending tests on Ni-Ti super elastic wire have been conducted. In order to examine fatigue fracture behavior in the human body condition, three types of conditions were tested; under dripping cold water, warm water and laboratory air. The curvature of specimen was calculated with specified maximum strain and specimen was loaded with cyclic vending deformation using handcrafted fatigue testing machine. As testing results, the number of cycles to failure decreased with increasing maximum strain under every environmental condition. Under the warm dripping water conditions, fatigue limit stress seemed to larger than that of under cold drip and laboratory air conditions. The number of cycles to failure varied slower than with maximum strain under the warm water condition than cold water and laboratory air conditions. In the fractured surface, dimensions of cleavage fractured area  became smaller with increasing maximum strain. The variation range of  in under dripping warm water was smaller than laboratory air and cold water conditions.