Mathematical modelling of welding : sensitivity of residual stresses and thermal dilatations on welding parameters

Abstract

In South Africa, the determination of residual stress distribution and undesirable metallurgical phase fractions that are formed in components during welding are been dealt with in a destructive or semi-destructive manner. This dissertation is an attempt at enhancing the acquisition of residual components found in welded structures. It shows how finite element methods can be used to obtain these results. TIG welding is modeled as a thermo-mechano-metallurgical (TMM) problem. The mathematical and finite element models for welding described in this study is based on the work performed by Ronda and Oliver. These models has not yet fully been incorporated into any of the existing computational tools and therefor, a commercial computational software program, SYSWELD 2, was employed to perform the welding simulations. The Leblond material models are incorporated into this software program, and the model that is used for this study is described in this text. Computational simulations were performed to study the effects that the sensitivity of welding parameters would have on the resulting shape and size of Heat Affected Zones, depth and width of penetration, temperature fields, metallurgical solid phase fractions, as well as residual stress distribution and deformation. The results of these simulations were compared to laboratory experiments.