Numerical modelling on residual stress of heavy-thick T-joints with multiple pass peening

The manufacturing process of heavy-thick T (HTT) joints with main plate thickness of 50 and 80 mm improved by portable pneumatic needle-peening (PPP) treatment with multiple passes is investigated in this study. Experimental measurements during the welding and peening of HTT joints are performed to obtain the temperature histories, residual stresses, and profile shapes of weld toe and PPP groove. A simulation framework for the multi-pass welding and peening processes of HTT joint with high accuracy is proposed. Simulation strategies are introduced in detail, including template-based mesh refinement, residual stress interpolation, peening frequency scaling, definition of multi-pass peening, and determination of welding and peening process parameters. Extensive validations are performed on the welding fusion sizes, temperature histories, as-welded and as-peened residual stresses, and geometrical profiles of weld toe and peening-induced groove. Based on the established framework, the effects of indentation depths and pass shift of the multi-pass treatment are discussed. The results show that under the conditions investigated, the final permanent indentation depth is insensitive to the process parameters of the preceding pass. However, the final as-peened residual stresses can be substantially improved by enlarging the indentation depth of the preceding pass. Specifically, increasing the indentation depth of first pass from 0.0728 to 0.1365 mm, 73% and 42% enhancements of peak compressive residual stresses on the main plate and in thickness direction are numerically revealed. Multiple passes are recommended in the practice of high frequency peening process.