Plasticity-based distortion analysis for fillet-welded thin plate T-joints

The characteristic relationship between cumulative plastic strains and angular distortion of fillet welded thin plate T-joints was studied using numerical analysis. A 3D thermo-elastic-plastic analysis incorporating the effects of moving heat and non-linear material properties was performed to obtain the characteristic cumulative plastic strain distributions and angular distortion. The procedure of plasticity-based distortion analysis (PDA) was developed to map each cumulative plastic strain component into elastic models using equivalent thermal strains. PDA determined the quantitative individual angular distortions induced by cumulative plastic strains, demonstrating their contribution to the total angular distortion and the unique relationship between cumulative plastic strains and distortion.; PDA was used to investigate the effects of external restraints and thermal management techniques on the relationship between cumulative plastic strains and angular distortion of T-joints and T-tubular connections, and the limitation of the 2D model application in the distortion analysis of T-joints. It was shown that PDA was a very effective tool in investigating the relationship between cumulative plastic strains and distortion.; The following significant findings were observed in this study. (1) Distortion was uniquely determined under the specified cumulative plastic strain distribution. (2) The transverse cumulative plastic strain produced bend-down angular distortion in T-joints. Vertical and longitudinal components induced relatively small bend-down and bend-up angular distortion, respectively. Most bend-up angular distortion produced by the xy-plane shear cumulative plastic strain existed in and around the welded region. (3) Angular distortion was reduced by increasing the degree of external restraint. External restraint mainly controlled individual angular distortion induced by the transverse cumulative plastic strain. (4) Heat sinking increased angular distortion of T-joints. Heat sinking affected individual angular distortions induced by the nominal components of cumulative plastic strains. (5) TIG pre-heating resulted in the reduction of angular distortion of T-joints. TIG pre-heating mainly controlled individual angular distortion induced by xy-plane shear cumulative plastic strain. (6) Angular distortion in T-tubular connections was induced by the transverse, vertical and xy-plane shear cumulative plastic strains. Heat sinking effectively reduced angular distortion. (7) The relationship between cumulative plastic strains and angular distortion in T-joints obtained from the 2D and 3D models was inherently different.