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In spite of an increased awareness of welding residual stress threat to structural integrity, the extent of its influence on fatigue strength especially under multiaxial cyclic loading is still unclear and matter of debate. This uncertainty which leads to conservative assumptions in fatigue design codes is based on the lack of insight into the initial welding residual stress field and its behavior during the three phases of fatigue damage namely; crack free, crack initiation and crack propagation periods. Since a significant amount of fatigue failures in welded joints are caused by torsion or combined tension-torsion in machinery components, estimating the potential threat of the inevitable residual stresses to structural integrity seems to be mandatory for the design of the future lightweight welded components and structures.In this paper the axial and hoop residual stresses in cylindrical specimens with bead on tube welds out of S355J2H were determined experimentally by means of x-ray and neutron diffraction. After discussing briefly the sources and origins of the residual stress field, its behavior under pure torsional and combined tension-torsion loading will be presented.