Optimal Preparation Process for Fatigue Specimens Treated by Ultrasonic Peening
This paper addresses the issue of preparing small-scale fatigue specimens for properly evaluating the effect of ultrasonic peening on fatigue life of welded structures and metallic components by laboratory experiment. Axial fatigue test and four-point bend fatigue test were conducted on fatigue specimens including untreated specimens and specimens being peened before and after cutting process. Fracture surfaces of fatigue failure specimens were observed to determine the crack initiation sites. Residual stresses were measured on different widths of cutting pieces to investigate the residual stress relaxation caused by cutting. The experimental results demonstrate that for specimens being cut after peening treatment, residual stresses are relaxed at the cutting edge, which results in significant reduction of fatigue life improvement and potential fatigue failure from the cutting edge. It is concluded that small-scale fatigue specimens should be machined to the final shape first and then applied peening, which not only applies for ultrasonic peening treatment, but for other residual stress-based improvement techniques.
KeywordsUltrasonic peening Fatigue specimen Cutting Residual stress Fatigue life
The authors are grateful to the National Natural Science Foundation of China (Grant No. 51275343) for financial support.
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