抄録
Fretting fatigue, which is a composite phenomenon of metal fatigue and friction, is one of the major factors in the design of mechanical components. Since hydrogen can influence both fatigue and friction, importance of fretting fatigue is highlighted in hydrogen equipment. The fretting fatigue strength of austenitic stainless steels significantly reduced by the effects of hydrogen. One of the major reasons for the reduced fretting fatigue strength in hydrogen gas is adhesion between contacting surfaces. Friction force is transmitted through the small area of the adhered spots, severe stress concentration then arises in the vicinity of the adhered spots. This increase in mechanical stress assists crack initiation. Furthermore, evidences of severe cyclic plastic deformation is found at the adhered part. The plastic deformation results microstructure change. These are other important factors for the reduction in fatigue strength due to hydrogen, because plastic deformation is essential for the functions of hydrogen regarding HELP mechanism, hydrogen diffusion and hydrogen concentration. Fretting fatigue test of hydrogen charged materials are also carried out. Internal hydrogen also reduced critical stress to crack initiation, and it resulted reduction in the fretting fatigue strength.
