The effect of ultrasonic impact treatment on residual stress of doubly-welded rib-to-deck joints in orthotropic steel decks

Purpose The purpose of this paper is to quantitatively investigate the effect of ultrasonic impact treatment (UIT) process parameters (including impact velocity, needle diameter, overlapping distance and offset distance) on welding residual stress (WRS) in a doubly-welded rib-to-deck joint (DRJ). Meanwhile, a multi-parameter optimization method was proposed to optimize the effect of UIT processes. Design/methodology/approach A 3D finite element model simulating UIT was developed to regulate the WRS in DRJ and experimentally validated. A multivariable UIT optimization method, employing the Robbins–Monro stochastic approximation algorithm with gradient feedback, was proposed, and its efficacy was demonstrated through numerical experiments. Subsequently, the effect of different UIT process parameters on the WRS of DRJ was investigated using the optimized parameters. Findings Optimized parameter combination achieved 43.5% higher surface compressive stress and 119% deeper compressive layer. Impact velocity and needle diameter mainly affect residual stress magnitude at the DRJ weld toe, while overlapping distance and offset distance govern the residual stress distribution patterns in the DRJ. Originality/value This study deepens the understanding of UIT's regulatory effects on WRS in the DRJ. The application of UIT-driven WRS control demonstrates significant potential to enhance fatigue life and provide practical guidance for fatigue-resistant design of orthotropic steel decks.