METHOD OF DESIGNING LONG LIFE FATIGUE STRENGTH FOR METALLIC MATERIAL

摘要

PROBLEM TO BE SOLVED: To provide a method of designing long life fatigue strength of a metallic material with increase in the size of ODA (a hydrogen effecting area observed to be blackish with a metallurgical microscope) according to a life to be expected for usage of a mechanical part taken into account to allow an optimal mechanical part according to a service life set to be designed.;SOLUTION: A method of designing fatigue life is provided in which, based on fatigue test results, a functional relationship is determined between the number of stress cycles until failure and the size of a hydrogen effecting area around an inclusion where trapped hydrogen makes effects, an equivalent defect size, which is the size, after expansion of the inclusion, corresponding to the stress cycles to be expected for usage of a mechanical part in which a metallic material is used, is determined by the functional relationship, and the mechanical part is designed using the equivalent defect size for a calculation of long life fatigue strength such as allowable stress so that an increase in the size of ODA according to a life to be expected for usage of the mechanical part is taken into account.;COPYRIGHT: (C)2012,JPO&INPIT