Issue 36

Sz. Szávai et alii, Frattura ed Integrità Strutturale, 36 (2016) 36-45; DOI: 10.3221/IGF-ESIS.36.04 36 Focused on Fracture Mechanics in Central and East Europe Numerical simulation of dissimilar metal welding and its verification for determination of residual stresses Sz. Szávai http://orcid.org/0000-0002-8311-2870 Bay Zoltán Nonprofit Ltd., Engineering Division szabolcs.szavai@bayzoltan.hu Z. Bezi Bay Zoltán Nonprofit Ltd., Engineering Division zoltan.bezi@bayzoltan.hu C. Ohms European Commission Joint Research Centre, Institute for Energy and Transport carsten.ohms@ec.europa.eu A BSTRACT . This paper summarizes the results of the through-thickness residual stress distributions on dissimilar metal weld (DMW) mock-up. DMWs, as welded joints between ferritic steels and either austenitic stainless steels or nickel-based alloys, are commonly found in piping systems of NPPs as well as in other industrial plants. The welding of the mock-up is simulated by the 3D finite element model using temperature and phase dependent material properties. The commercial finite element code MSC.Marc is used to obtain the numerical results by implementing the Goldak’s double ellipsoidal shaped weld heat source and combined convection radiation boundary conditions. Residual stress measurements are performed on welded joints to validate the simulation results. The validated residual stress distributions can be used for the life time assessment and failure mode predictions of the welded joints. K EYWORDS . Dissimilar metal welding; Finite element analysis; Residual stress; Phase transformation. I NTRODUCTION issimilar metal welds are generally used in piping systems of nuclear power plants as well as in other industrial plants to connect low alloy ferritic steel components and austenitic stainless steel or nickel-based alloys. DMWs are produced by fusion welding and their structural stability is strongly affected by welding conditions and post weld heat treatment. This type of welding process produces large residual stresses. The maximum value of tensile stress is commonly equal to the yield strength of joint materials. The residual stress of welding can significantly impair the performance and reliability of welded structures. The integrity assessment and life estimation for such welded structures require consideration of residual stresses. Therefore, it is necessary to map and assess the distribution of these residual stresses in welded joints. D