OS1513 Effect on Repeated Stress in Hydrogen Gas of TiNi Shape Memory Alloy

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  • OS1513 水素環境下における繰返し応力がTINI形状記憶合金の寿命に及ぼす影響

Abstract

TiNi shape memory alloys (SMA) receive the great attention because of their unique shape memory properties and commercial potential. However, TiNi alloys are apt to absorb hydrogen and deteriorate in various hydrogen environments, and the behavior of TiNi alloy fatigue life under the hydrogen environment has not been elucidated yet. By comparing fatigue test in air and fatigue test in hydrogen environment, the fatigue life of later clearly decreased than the other. At this time, a brittle layer was not formed on the fracture surface of the specimen for fatigue test in hydrogen environment However, macroscopically fracture surface was showing signs of brittle fracture. Furthermore, by comparing fatigue test in hydrogen environment and constant stress test and SSRT, the relationship between maximum stress and charging time showed good agreement with each other in low stress area about 300 MPa. On the other hand, in high stress area about 1000 MPa, large difference can be seen in the life of each. Therefore, the destruction under high stress amplitude is controlled by the damage due to stress fluctuation. On the other hand, destruction under low stress amplitude is controlled by the hydrogen embrittlement and the maximum stress.

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