Dynamic thermal tensioning for welding distortion control of thin-walled T-beam structures in large PCTC shipbuilding

IntroductionLongitudinal bending distortion is a major manufacturing problem in thin-walled T-beam stiffened structures used in large Pure Car and Truck Carrier (PCTC) ships. This study investigates the formation mechanism of welding distortion under different welding speeds and develops an induction-assisted dynamic thermal tensioning method for active distortion control.MethodsThermo-elasto-plastic finite element models were established to investigate the transient temperature field, plastic-zone evolution, residual stress distribution, and bending distortion of T-beams under high- and low-speed welding conditions. A temperature-dependent modified Johnson–Cook constitutive model for AH36 steel was developed from tensile tests at multiple temperatures and strain rates and implemented in ABAQUS through a UMAT subroutine. The constitutive model was validated against an independent AH36 butt-welding experiment. The effects of induction heating temperature and heating distance were then investigated numerically, followed by full-scale validation on a high-speed tandem submerged arc welding production line for large PCTC shipbuilding.ResultsLow-speed welding produced a larger plastic compression zone and greater longitudinal shrinkage strain accumulation because of the longer high-temperature residence time, resulting in more severe final longitudinal bending distortion. High-speed welding was mainly characterized by transient thermo-elastic sagging during the welding stage. Induction-assisted dynamic thermal tensioning effectively reduced longitudinal bending distortion by regulating the temperature field and longitudinal shrinkage in the web region. The best-performing induction heating conditions depended on the welding speed. In the full-scale production experiments, the selected induction heating parameters reduced the longitudinal bending distortion of the T-beam by up to 66.7%, and the observed regulation trends were consistent with the numerical results.