抄録
In order to clarify how compression load affects interior-originating fatigue fracture surfaces of high strength steel, uniaxial tension fatigue tests were carried out under different stress rations (R=0.3,0 and -1). The results were as follows; Interior-originating fractures under R=-1 occurred in shorter fatigue lives than those under R=0.3. Optically Dark Area (ODA) was formed even in short fatigue life of (10)^5 cycles. The morphology of ODA was closely related to the stress ratio, especially compression stress. Even though the fracture origin of the specimen was not inclusion, ODA was formed on the fracture surface.
