Influence of welding residual stresses on fracture strength of specimens and pressure vessels

Abstract

Damage tolerant approaches have been employed increasingly in newlinethe design of critical engineering components. In these approaches, one has to newlineassess the residual strength of a component with an assumed pre-existing newlinecrack. In other cases, cracks may be detected during service. Then, there is a newlineneed to evaluate the residual strength of the cracked components in order to newlinedecide whether they can be continued safely or repair and replacement are newlineimperative. Pressure vessels are being commonly used in aerospace and ground newlineapplications. Fusion welding is an efficient joining process for manufacturing newlinemetallic pressure vessels. As a result of thermally induced plastic deformation newlineduring the welding process, the internal stresses namely, the welding residual newlinestresses are developed in the welded components and structures. Residual newlinestresses can have a detrimental effect on the integrity of a structure. newlineFor welding simulation, 2D axisymmetric and plane stress models newlineare generated utilizing the ANSYS and considering Gaussian distribution for newlinethe heat source. The residual stress analysis results are found to be in good newlineagreement with existing complex 3D finite element results. Thermo-mechanical finite element analysis has been performed to newlineassess the residual stresses developed in the carbon steel ASTM 36 carbon newlinesteel pressure vessel during welding and elasto-plastic analysis to examine the newlineeffect of residual stresses on failure pressure of the pressure vessel. It is noted that the failure pressure of unflawed cylindrical vessels is reduced in the newlinepresence of residual stress. newlineA simple relation for the characteristic length in the modified point newlinestress criterion is suggested for accurate fracture strength evaluation of newlinecracked bodies. Adequacy of the procedure is demonstrated considering the newlinefracture data of heat treated wrought aluminum alloy center crack tension newlinespecimens. newline