3D Simulation of a Peripheral Adapter J-Groove Attachment Weld in a Vessel Head

In Pressurized Water Reactors, most of components have large thicknesses and their manufacturing processes often require multipass welding. In spite of the stiffness of these components, the distortion issue may be important for operational requirements (e.g. misalignment) or controllability reasons (Non Destructive Examinations have to be feasible). These requirements may be difficult to meet by adjusting welding processes. Indeed because of the complexity of mechanisms involved during a welding operation and the high number of influencing parameters, this process is still essentially based on the experience of the welder. Furthermore the experimental estimation of the stress and distortion level in the component remains a difficult task that is subject to errors even if techniques are currently improved to become more accurate. That is the reason why AREVA NP has put many efforts into developing welding numerical simulations, in order to have a better understanding of the involved physical phenomena and also to predict the residual state allowing a qualification of the manufacturing processes in the very early phase of the welded components design. Within the framework of a R&D program whose main objective was to improve tools for numerical simulation of industrial cases of welding, AREVA NP has decided to validate new methodologies based on 3D computation by comparison with measurements. For this validation task the chosen test case concerns a peripheral adapter J-groove attachment weld on a vessel head. For such an application, operations of post-joining straightening have to be limited, if not prohibited, because of their cost or the impossibility to use them in front of a steel giant. The control of distortions during welding operations constitutes an important stake for which simulation can be of great help. Regarding distortions issues, an accurate metal deposit sequence modeling is mandatory, especially for multipass welding on such a complex geometry. The aim of this paper is to present, through a peripheral adapter J-groove attachment weld mock-up, the capabilities AREVA NP has in order to predict, in an efficient way the consequences of complex welding operations requiring 3D transient numerical simulations.