Modeling and simulation of weld residual stresses and ultrasonic impact treatment of welded joints

Most structures are fabricated using welded joints because of its low cost, structural strength and geometric flexibility. Welding is considered a highly complex metallurgical process that results in irregular geometries, material imperfections/flaws and tensile residual stresses. High tensile residual stresses and stress concentrations resulting from the weld process have a significant impact on fatigue life of structures, and thus a topic of great concern in product design. Ultrasonic impact treatment (UIT) is regarded as one of the most effective post welding treatment techniques to enhance the fatigue performance of welded structures. The UIT aims to introduce fatigue-beneficial compressive stresses by plastically deforming the weld toe and reduce stress concentrations by modifying local weld geometries. In this study, 3D modeling and simulation using finite element (FE) method has been performed to simulate welding process and numerical modeling of the UIT process to predict weld residual stress distribution of butt and T weld joints. The predicted numerical results under as-welded and UIT treatment conditions were compared to present weld residual stress improvements. Compared results shows that the UIT has potential applications on the fatigue design of welded structures, can lead to lighter structures and products, in which structures can be down-sized and optimized to reduce weights.