K-0517 高強度鋼SNCM439における超高サイクル疲労特性に関する研究(S04-2 高強度鋼の超高サイクル疲労(1))(S04 金属材料の組織と疲労強度信頼性)

概要

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The present study investigates giga-cycle fatigue properties of a high strength steel SNCM 439, a Ni-Cr-Mo steel known as a bearing steel. Cantilever rotating bending fatigue tests have been made on the SNCM 439 steel at room temperature in air. The characteristic duplex S-N diagram has been obtained for the SNCM 439 steel. Two types of fracture modes were observed according to the applied stress level; i.e., surface fracture was observed at stress levels higher than 1200 MPa, whereas internal fracture at those lower than 1200 MPa. At the lower stress levels, fish-eye cracks were observed as the origin of fatigue fracture and were always initiated at Al_2O_3 inclusions in the present study. Statistical distributions of fatigue lives of the present high strength steel were determined at five stress levels by the use of Weibull probability paper. It was found that fatigue life followed the composite Weibull distribution at the five stress levels investigated, indicating that the fracture mode is different at higher and lower stress levels.
一般社団法人日本機械学会の論文
2001-08-22