Numerical modeling of residual stresses and fatigue damage assessment of ultrasonic impact treated 304L stainless steel welded joints

摘要

Welding technology has been widely adopted to fabricate structures and components due to its low cost and easily accessible procedure. However, the welding methods usually impose tensile residual stresses on the fabricated part, that tend to be detrimental to fatigue properties of welded joints. Ultrasonic impact treatment (UIT) has been introduced as an increasingly popular post-weld treatment technique to improve fatigue performance of welded joints due to its high efficiency and reliability. In this paper, the simulations of welding and UIT processes were performed by means of finite element modeling to predict the residual stress distribution of the 304L stainless steel welded joints. Effects of the UIT on the residual stress distribution and fatigue performance were individually investigated. Finite element results indicated that the UIT introduced beneficial compressive stress up to depths of 2-3 mm in the butt and T-joint welds. The stress distribution at the potential crack plane and the respective stress intensity factors were calculated by taking into account residual stresses, to evaluate the fatigue crack propagation. The fatigue crack growth model was subsequently employed to predict fatigue lives of the welded joints. Results of the fatigue analysis showed that the UIT remarkably extended fatigue lives of the 304L welded joints.