X-ray fractography on fatigue fracture surface formed by crack propagation in initial tensile residual stress field
Akita Koichi; Inoue Tomohiro; Takahashi Satoru; Misawa Hiroshi; Kodama Shotaro
Abstract:Fatigue tests were performed using CCT specimens having initial tensile residual stress caused by welding. The residual stress distribution on the fatigue fracture surface was measured by X-ray diffraction method. The monotonic plastic zone depth corresponds to the Kmax,true which is the sum of the Kmax related to the applied maximum stress and the Kres caused by the initial residual stress. So, if the initial residual stress distribution is known, the Kmax or the applied maximum stress can be estimated from the monotonic plastic zone depth. The residual stress on the fatigue fracture surface corresponds to the sum of the tensile residual stress related to the Kmax,true and the compressive residual stress related to the DKeff. So, even if the initial residual stress distribution is unknown, the DKeff or the stress amplitude can be estimated from the residual stress on the fatigue fracture surface and the monotonic plastic zone depth. Key Words:initial residual stress, fatigue, fatigue fracture surface, X-ray stress measurement, residual stress, X-ray fractography, fracture analysis, plastic zone, stress intensity factor