Investigation of fracture behavior and deformation capacity of high-strength steel butt-welded joints

Performance-based design of high-strength steel welded structures requires accurate prediction of their load-bearing capacity as well as deformation capacity. There have been several studies undertaken on the load-bearing capacity of high-strength steel butt-welded (HSSBW) joints, but very few studies are performed on their deformation capacity. This study investigates the fracture behavior as well as the deformation capacity of double-V HSSBW joints with strength-matching welding materials, taking into account the effects of different heat inputs, steel strengths, and steel processing methods. To evaluate the deformation capacity, fracture initiation criterion, and fracture propagation model of four zones within the butt-welded joints, including hardened heat-affected zone (HHAZ), softened heat-affected zone (SHAZ), welding material zone (WM), and base metal zone (BM), are first calibrated from experimental results and numerical analysis results. The calibrated material models are validated against the test data. Numerical analyses are then performed to predict the fracture behavior and deformation capacities of the welded joints utilizing the verified material models. According to the analysis results, heat inputs no more than 1.9 kJ/mm impose a limited influence on the fracture behavior of each zone within the double-V HSSBW joints. If the heat input is below 1.9 kJ/mm, QT steel welded joints exhibit a higher deformation capacity than TMCP steel welded joints. When compared to the tension specimens made of pure base metal, the reduction of the deformation capacity of the double-V HSSBW joints was even more than 30 % and it is more significant than the reduction of load-bearing capacity, therefore, evaluation of the deformation capacity of the welded joints is very essential for the performance-based design of high-strength steel welded structures.