| AISI 4140 Steel was austenitized in salt bath, oil quenched, then tempered to 650℃. Macroscopic residual stress and microscopic residual stress during repeated bending fatigue process of the steel were measured by shift of X-Ray diffraction Bragg Angle (2θ) of (211) plane; and broadening of integral breadth, respectively, using half value breadth method for the study on the possibility of fatigue life estimation of the steel. 1. Fatigue life estimation of the steel by measuring the variation of macroscopic residual stress during fatigue process is believed to be impossible. 2. Half value breadth ratio, B/Bo(B, Bo ; current, initial value of half value breadth, respectively.) of the steel during the fatigue process increased to a maximum point which is believed to be the fatigue initiation point, then began to decrease and decreased rapidly on the stage of fracture. Considering these facts, the useful life of AISI 4140 steel can be estimated roughly by X-Ray diffraction method. |
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