Experimental and numerical investigation on ductile fracture behavior of welded areas under tensile and shear forces

Due to complex stress conditions, welded joints in steel and concrete-filled steel tubular trusses are considered weak parts and are susceptible to failure by fracture. To investigate the ductile fracture behavior of steel tubular welded joints under a combination of tension and shear, this study took 36 specimens from the base/tube metal (BM), heat-affected zone (HAZ) and weld metal (WM) in welded areas. The fracture behavior of five kinds of specimens were compared. Then, to simulate fracture patterns of specimens, this study developed a new Shear- Modified GTN model (SMGTN), which was based on two types of damage variables: tension and shear. The particle swarm optimization (PSO) algorithm was employed to calibrate SMGTN model parameters. Finally, the stress conditions, damage, and fracture patterns of various specimens were analyzed. The result demonstrated that the larger the radius or shear center rotation angle of notched specimens, the larger the fracture displacement. The materials in BM, HAZ, and WM regions exhibited different ductile behavior under different stress conditions. The calibrated parameters of SMGTN model in this study accurately predicted the fracture displacement and development patterns in the BM, HAZ, and WM regions.