The evaluation method for grain refinement effect of UIT on fatigue life of welded joints based on crystal plasticity

Abstract

Ultrasonic impact treatment (UIT) is regarded as one of the most promising post-weld techniques for improving the fatigue performance of welded joints because of its complex enhancement effects. However, difficulties in evaluating the multiple enhancement effects of UIT, especially the effect of grain refinement, on the fatigue life of welded joints have significantly hindered the application of this technique. Thus, a fatigue life evaluation method based on crystal micro-plastic slip (p) was proposed in this study, and the united p-N curve for both as-welded joints and welded joints subjected to UIT with different impact parameters was determined by re-analyzing relevant experimental data in the literature. The proposed p-N curve was then used to evaluate the fatigue performance of nine rib-to-deck joints in orthotropic steel bridge decks, which further verified the applicability of the united p-N curve for fatigue performance evaluation of as-welded and UIT joints under complex loading conditions. Finally, the grain refinement effect of UIT on the fatigue performance of welded joints was discussed and analyzed. The results showed that the fatigue life of the as-welded joints was extended by 10.4 % ∼ 17.1 % owing to the grain refinement effect of UIT.