Fracture behavior of corroded high-strength steel butt weld joints based on a modified ductile-to-brittle transition CAFE model

High-strength steel (HSS) has recently emerged as a complementary constructional building material in civil infrastructures. Welding is a method used for assembling and connecting HSS structural components. However, the coupling effect of corrosion and weld defects can lead to brittle cleavage in HSS joints, posing serious structural safety risks. Predicting fracture behavior in corroded HSS welds is challenging due to complex factors such as geometry changes, material degradation, and the competition mechanisms between toughness and brittleness. Therefore, to meet the need, this study aims to unveil the fracture mechanism of corroded HSS weld joints and elucidate the governing factors affecting their behavior through the integration of experimental and numerical approaches. The significance of this work lies in the development of a new modified approach that integrates an uncoupled ductile fracture model with a cellular automata- finite element brittle array, providing a novel means to comprehensively understand the ductile- brittle transition in corroded Q460 butt weld joints. To calibrate the model, a comprehensive experimental study, using Q460 steel butt joint specimens in exposure to accelerated corrosion tests, surface scanning, and monotonic tensile tests, was conducted to establish a correlation between corrosion parameters and mechanical property deterioration in welded joints. Fracture patterns corresponding to different corrosion degrees were analyzed using digital image correlation technology and electron microscope scanning. The results revealed that the combined approach accurately predicted both the fracture initiation and propagation processes. The modified model indicated that the cleavage brittle fracture mechanism began affecting material failure when the heat-affected zone (HAZ) corrosion rate reached 17 %. Typical cleavage fracture characteristics occurred when the corrosion rate exceeded 50 %. Fractures predominantly occurred in the HAZ due to its complex tension-shear stress state and severe corrosion. As the corrosion rate increased, the fracture trend shifted toward brittleness.