METHOD AND S-N GAGE FOR MEASURING FATIGUE LIFE

摘要

PURPOSE:To make a fatigue life measureable in regarding it as a aroughly linear quantity by affixing a thin film material consisting of a material causing martensite transformation on the surface of a member. CONSTITUTION:The relations between the rate of increase in martensite in a material and cycle ratios of the case in which metastable austenite stainless steel is subjected to repetition of tension-compression with various forces are linear as shown in the figure. A thin film material consisting of a material causing martensite transformation, for example, metastable austenite stainless steel, that is, an S-N gage, is affixed on the surface of a material to be measured of fatigue life by utilizing such relations. If repetitive stresses are loaded upon the member, the same repetitive stresses are loaded on the S-N gage as well, and the gage causes martensite transformation. At a proper time, the S-N gage is stripped, and the rate of increase in martensite is measured from a change in magnetic permeability or by an X-ray diffraction method, whereby the fatigue life of the S-N gage, and further the fatigue life of the member are measured.