Finite element prediction of post-weld distortion using the linear elastic shrinkage volume method

Despite comprehensive research efforts in recent years, very little of the finite element modelling of welding processes has found an application in industry. In most cases the very long times required to obtain a solution continue to be the key hindrance. This fact has motivated the authors to investigate simplified approaches to the modelling of welding processes. Using the NISA™ finite element code, a simple method has been developed to predict the structural distortions which result from the transient non-linear localised heating phenomena inherent to arc welding processes. The model is based on the simplifying assumption that the volumetric changes occurring during fusion welding can be approximated by the linear thermal contraction of the designated shrinkage volume. This shrinkage volume then generates the internal forces which interact with the rigidity of a given structure to produce distortion. This approach enables the use of linear elastic steady-state finite element methods instead of non-linear transient formulations. The net results are significantly reduced solution times and more importantly the ability to predict distortions in large, highly complex welded structures. An experimental program, which looks at the distortion in a number of simple butt joint preparations was embarked upon. Initial results were in good qualitative agreement with the modelled predictions.