| 摘要 |
A long life fatigue strength design method for metallic material capable of designing an optimum mechanical part according to a set service life by considering an increase in ODA (area affected by hydrogen observed blackish by a metallurgical microscope) dimensions according to the predicted usable life of the mechanical part, comprising the steps of obtaining, from the results of a fatigue test, a functional relation between the number of repetitions of stress up to rupture and the dimensions of a hydrogen affected area around inclusions affected by trapped hydrogen, obtaining, from the functional relation, equivalent defect dimensions as the dimensions of the inclusions after an increase in dimensions corresponding to the number of repetitions of predicted working stress of the mechanical part using the metallic material, and designing the mechanical part by using the equivalent defect dimensions for the calculation of a long life fatigue strength such as an allowable stress, whereby a rupture life design can be performed with the increase in ODA dimensions taken into account according to the predicted usable life of the mechanical part.
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