Abstract
The purpose of this investigation is to detect a damage from actual stress distribution in the surface of specimen by using X-ray diffraction technique during fatigue test. An apparatus to measure the actual stress distribution along specimen circumference was fabricated by use of a cantilever type rotary bending fatigue machine and a stress analyzer based on single exposure technique with two position sensitive proportional counters. The authors developed a method for collecting separately the diffraction profile at each position along the circumference. Actual stress distributions at the maximum tensile applied stress were dynamically measured. As a result, the shape of the distribution was keeping stable with the increase in the number of stress cycles until crack initiation. When the crack length reached greater in size than the width of irradiation area, the actual stresses at the crack position were suddenly decreased down to 0MPa, and the distribution showed a V-shape. These results show that the method adopted in this study is available for detecting both the position and the period of crack initiation.
