Original paper(Vol.48 No.7 pp.711)

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 actual stress distribution along circumference of specimen 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. We proposed a method to collect separately the diffraction profile at each position along circumference of specimen. Actual stress distributions at the maximum tensile applied stress were measured during fatigue test. As results, the shape of actual stress distribution was keeping stable with increasing number of cycles until crack initiation. After crack initiation, the actual stress at the position of crack initiation was decreased suddenly near 0 MPa, and the distribution was shaped "V" type. The "V" type distribution was appeared when crack length reached greater in size than a width of irradiation area. These results show that the method proposed in this study is available to detect a position and period of crack initiation.

Key Words:X-ray stress analysis, Single exposure technique, Fatigue strength, Fatigue damage, Rotary bending fatigue test