Estimation of welding deformations and residual stresses based on the eigen-strain methodology

Abstract

The concept of assurance of structural integrity has been taken into accounted especially for energy-related structures where flaw evaluations are conducted based on the fracture mechanics and non-destructive inspections. In evaluations near welded locations, three-dimensional welding residual stresses must be given quantitatively. However, residual stresses only on surfaces can be measured by the X-ray technique. It is inadequate to apply the thermo-elasto-plastic simulation because it gives qualitative information owing to complexity of actual welding process. Moreover, it is required to predict welding deformations in the design process. Authors proposed a new method to evaluate both welding deformations and residual stresses based on the eigen-strain methodology, which is applicable to the finite element (FEM) analysis. In the proposed method, three-dimensional eigen-strains are estimated by the inverse analysis using the Truncated Singular Value Decomposition (TSVD) method and the penalty method. Numerical simulations are carried out for a butt-welded plate with larger angular deformation in the thickness direction. As a result, eigen-strains to express both welding deformations and residual stresses with higher accuracy could be estimated successfully.