Discussion on fatigue design of welded joints enhanced by ultrasonic peening treatment (UPT)

Large numbers of fatigue testing results of welded joints after ultrasonic peening treatment (UPT) were analyzed and summarized. Differences in fatigue design between as welded and UPT joints were discussed. Results indicate that material strength has effect, to a certain extent, on the fatigue performance of UPT welded joints. Contrast tests show that slope m values (6.3–23) of S–N curves of UPT welded joints are much bigger than 3.0 (recommended by the international institute of welding-IIW). It is not appropriate to simply use m as 3.0 to analyze the fatigue testing data of UPT joints. Furthermore, after UPT, fatigue strength is not independent of the average stress any more, so stress ratio should be taken into account for fatigue design.