Welding

Welding is one of the most prevailing manufacturing processes. A critical concern is its quality in terms of residual stresses and deformations as well as the welding strength. In spite of such a key interest, the analysis of welding deformations has not been so successful as in structural analysis. This is partly because welding involves much more complex phenomena than purely mechanical processes, and such complexities are manifested by the kinetics process regarding the phase evolution and by the thermo-mechanical processes as well.

Multi-physics diagram of welding process

An efficient and systematic numerical implementation of the thermo-elastoplastic constitutive equation of Lebond, which accounts for transformation plasticity in welding, has been carried out for finite element analysis. Hyperelastic formulation based upon the multiplicative decomposition has been exploited, and this enables one to bypass the objective integration for stress update, and moreover to obtain the unique associative flow rule from the principle of the maximum plastic dissipation. For fast convergence of the solution, the tangent modulus consistent with the stress-update algorithm has been calculated in consideration of the transformation plasticity.

The results are in a good agreement with those from commercial welding software "S". We confirm that the present implementation undergoes the fewer iterations to reach convergence.

Perpendicular & shear stresses along the weld line