Measurement of internal residual stress field in multi-layer fillet welded joint of ultra-thick circular plate and tube

It is well known that both the internal and surface residual stresses in welded joints have great influence on the corrosion resistance and creep and fatigue strength of welded structures. In this study, the inherent strain theory and stress released method by the electric charge cutting were used to measure the internal residual stress field in a multi-layer fillet welded joint of ultra-thick plates and tube. A L-shape sample and several C-shape samples were cut from the original plate-tube fillet welded joint to separate the efficient inherent strain components. The inherent strain components in the L-sample and C-samples were the same as those in the welded joint. They were identified by performing inversely an elastic finite element analysis. Finally, by applying the identified inherent strains into the original welded joint modeled by FEM, the 3D welding residual stress field was reproduced by elastic analysis. It was shown that the circumferential stress σ_θ was obviously larger than other residual stress components in the plate-tube fillet welded joint. The tensile residual stress on the welded surface was smaller than that under the surface of 10 mm. The residual stresses on the inner surface of the tube were smaller than those on the welded surface and the axial stress component on the inner surface of the tube was compressive which may be contributed by water cooling during welding.