Thermally induced deformations and associated residual stresses are unavoidable in welded structures and constructions. The residual stresses affect the fracture, fatigue, and stress corrosion cracking behaviour in welded joints, and the welded structures and constructions suffer from restrictions set by these stresses.
Today's practice is quite conservative; welding residual stresses as high as the material’s yield strength are normally anticipated. Significant savings could thus be made if the level and distribution of residual stresses could be predicted in an effective way. Appropriate manufacturing and heat treatment procedures could then be evaluated early in the design stage, and more precise input to further lifetime and failure assessment could be given. Quantifying the deformations and stresses and assessing their effect on structural integrity are, however, still fundamental issues, which legitimate RESIA's principal project objective.
Sub-goals for the RESIA Project are:
Slug catcher - a typical welded structure. Photo: Statoil; reproduced according to separate agreement.
Develop a novel procedure for structural integrity assessment based on quantitative modelling of residual stresses and associated changes in the microstructure and mechanical properties of the material.
Establish an industrially useful simulation tool that quantifies residual stress distributions in welded steel components and structures.
Develop constitutive equations tailored for residual stress prediction that capture the most relevant micro-structural effects in high strength steels.
Establish a reliable method by which the parameters in these constitutive equations can be experimentally identified and determined.
Validate the new models by comparing modelling results to experimental measurements obtained within the project or found in the literature.
Demonstrate the usefulness of the project results through selected case studies that show how residual stresses affect the structural integrity of typical welded joints.