Finite element analysis of wave propagation in austenitic stainless steel welds with three-dimensional solidification structures predicted by cellular automaton method

Abstract

Austenitic stainless steels have been extensively used in nuclear power plants, and therefore, their welds must undergo ultrasonic testing (UT). However, conducting UT on the far side of these welds poses significant challenges. A thorough understanding of wave propagation in these welds is essential for enhancing the performance of UT. In this study, we executed precise three-dimensional simulations of wave propagation within welds containing a solidification structure using the finite element method (FEM). A three-dimensional cellular automaton finite difference model was developed for predicting the solidification structure of multilayer and multipass austenitic stainless-steel welds (ASSW) based on the welding process. This model incorporated elements such as heat flow, grain growth, grain melting, and alloy addition during welding. Further, it accurately replicated the experimental peak temperature at measurement points near a welding groove for an SUS316L ASSW featuring seven layers and seven passes. The predicted solidification structure for the SUS316L ASSW closely matched actual macrographic results. We integrated the forecasted solidification structure into an FEM code to simulate wave propagation in ASSW, and we compared the numerical outcomes with experimental findings for both normal and angle beam testing. The numerical results precisely mirrored the experimental observations. Longitudinal waves traversed the welds smoothly, whereas shear waves encountered significant disruption. In addition, the intensity of all echoes determined through the numerical analysis aligned closely with the experimental results, exhibiting a variation of less than 2 dB.