FATIGUE LIFE IMPROVEMENT AND PREDICTION FOR AS-WELDED AND PEENED CAR COMPONENT UNDER AXIAL-TORSIONAL LOADINGS

摘要

Both shot and ultrasonic peening treatments were used to improve fatigue strength of a welded specimen. Fatigue tests were conducted under in phase axial-torsional loading for three kinds of specimens. It is found that the ultrasonic peening is better than the shot peening for fatigue life improvement. Based on the testing data and FE analyses of the critical damage planes of the specimens, a new damage parameter was used to correlate well the fatigue lives for aswelded and the welded specimens with the ultrasonic peening treatment. Based on the relationship between the new damage parameter and fatigue lives obtained from the as-welded and peened specimens respectively, the FE results of a welded component were used to predict the fatigue lives of the component with and without the ultrasonic peening treatment. It is found that the predicted lives agree reasonably with the testing data for the as-welded component, the predicted fatigue life improvement of the welded component after ultrasonic peening treatment is obvious.