X-ray Investigation on the Fatigue Damage of Metals

Abstract

In the present paper, the fatigue process is studied by observing the half-value breadth of the X-ray diffraction lines taken from (310) atomic plane with C0-Kα radiation, which were obtained from the specimens of carbon steel wire, cast iron and cast steel stressed alternately in rotary bending. It is found that during the fatigue process the change of half-value breadth is directly related with the change in micro-stresses. Considering from the change of half-value breadth due to stress cycles, the authors think that the fatigue process consists of three sequent stages, namely the first stage of fatigue, secondary stage of fatigue, and tertiary stage of fatigue. At the end of the secondary stage of fatigue the half-value breadth has a constant value irrespective of the magnitude of applied stress. The relation between b/B and log n/N (b and B are the current and the initial value of half-value breadth, and n and N are the current and the ultimate number of stress cycles) is represented by a straight line irrespective of the magnitude of alternate applied stress. This relation supplies a possibility for the non-destructive prediction of the fatigue life.