A STUDY OF THE EFFECT OF PRE-STRAINING ON ANGULAR DISTORTION IN ONE-PASS FILLET WELDING INCORPORATING LARGE-DEFORMATION THEORY

By using the finite element method based on the large deformation theo ry, the effect of pre-straining on angular distortion of one-pass fill et weldments was analysed for the free-end and constrained-end conditi on. Pre-straining by an additional concentrated load caused a large th ermal deformation during heating, and reduced the reverse distortion d uring cooling and consequently the residual distortion. Geometric chan ge of the fillet weldment caused by pre-straining during welding induc ed an initial stress effect on the stiffness to the further deformatio n, which is due to a developed in-plane stress. This initial stress ef fect could be considered in the large deformation theory to be based o n the updated Lagrangian method, while it could not in the small defor mation theory. As the pre-straining load increased in the free-end con dition, the initial stress effect also increased. In the constrained-e nd condition, the initial stress effect played an important role in th e deformation of the fillet weldment, even without pre-straining. By c omparing the results predicted by the large deformation theory with th ose by the small deformation theory and experiments, it can be shown t hat the large deformation theory is able to describe the distortion ph enomenon in fillet welding reasonably well.