X-Ray Investigation of Fatigue Damage of Metals : On the Changes in Half-Value Breadth of X-Ray Diffraction Line, Residual Stress, Micro-Structrue, and Micro-Hardness Due to Stress Repetitions

Abstract

In the previous papers, the authors reported that the half-value breadths of metals read from X-ray diffraction lines changed with the application of alternating stresses at constant or varying stress amplitude, and it was found that the change of half-value breadth b/B (B and b are the initial and the current value of half-value breadth respectively)-logn/N (n/N is the cycle ratio) or b/B-logΣn/N (Σn/N is the summation of cycle rations under a varying stress amplitude) relations were expressed by a straight line irrespective of the magnitude of applied stress or stress history. Namly, the authors offered a certain method of nondestructive prediction of fatigue life. The studies carried out by the authors previously, however, did not treat the interpretation of the change in half-value breadth from the viewpoint of the mechanism of fatigue. In this connection, in order to reach a better understanding of the change in half-value breadth, they investigated the changes in half-value breadth of X-ray diffraction line, residual stress, microstructure, and micro-hardness due to stress cycles, and discussed on a change of half-value breadth.