Determination of residual stress in hybrid laser-arc welded U-rib-to-deck joints by thermo-metallurgical-mechanical simulation and neutron diffraction

Welding residual stress is crucial to the fatigue performance and reliability of U-rib-to-deck joints, and its accurate measurement and control remains challenging and lacking an effective approach. In this paper, a thermometallurgical-mechanical finite element model considering solid-state phase transformation was developed to investigated the residual stress states of U-rib-to-deck joints fabricated using hybrid laser-arc welding technique. Neutron diffraction testing was conducted to determine the residual stress distribution in three orthogonal directions to validate the model. The results showed that solid-state phase transformation involving changes in mixed phase properties and transformation strain significantly influenced the residual stress in hybrid laser-arc welded U-rib-to-deck joints. The low yield strength property of the supercooled austenite and the volumetric expansion of the bainite transformation strain are crucial for residual stress reduction. A reasonable S-shaped agreement trend was observed between residual stress simulation and neutron diffraction data along the potential crack propagated path. Thermo-metallurgical-mechanical modeling helps to control welding residual stress fields via simulation methods, which is crucial to consider solid-state phase transformation. These findings provide support for assessing the fatigue performance of U-rib structures using hybrid laser-arc welding.