Residual Stress Finite Element Analysis and Measurements of a Tube Penetration J-Groove Attachment Weld in a Hemispherical Head of a Large Ferritic Pressure Vessel: Part I — Centre Nozzle

A programme of work was undertaken to gain an understanding of the residual stress levels in the tube penetration J-groove attachment welds in a hemispherical head of a large stainless steel clad ferritic pressure vessel. In this first part, of a two part paper, the finite element analyses that were carried out to model the centre nozzle penetration are described. Two axisymmetric residual stress finite element models were developed. One used an accurate representation of the weld bead deposition sequence and the other a bead lumping approach to model bead deposition. The results from the finite element analyses were compared with both surface and through thickness stress measurements. These measurements were taken on a mock-up weld that was representative of the actual component. The surface measurements were taken by using an incremental centre hole drilling technique (ICHD). The through thickness values were obtained from deep hole drilling (DHD) measurements. The DHD measurements were taken before and after the cladding of the mock-up. The analytical results from the two axisymmetric models showed the simpler blocked dump model approach to be reasonable in capturing the general level of stress. The finite element analysis results showed good agreement with the measurements in the radial direction, but predicted greater than the measured values in the hoop direction.