Numerical Study on Influence of Gap Upon Transverse Shrinkage in Welding

Welding distortion is caused by the local shrinkage produced during the welding thermal cycle. The local shrinkage can be separated into four, namely transverse shrinkage, longitudinal shrinkage, transverse bending and longitudinal bending. In this research, the influence of the root gap on the transverse shrinkage is closely examined from the aspect of closing or opening of the root gap with the movement of the welding torch. Since the contact phenomena between the two surfaces forming the root gap is important, interface element is introduced to a thermal elastic-plastic FEM. The butt welding and the fillet welding model are used to study the influence of gap size and the pitch of tack welding. Once the relation between the size of the gap and the transverse shrinkage is obtained, it can be introduced to the elastic FEM using the inherent deformation to predict the welding distortion of large structures.