The NeT bead-on-plate benchmark for weld residual stress simulation

Fracture mechanics based structural integrity assessments of pressure vessels and piping are widely used to support the economic and safe management of operating engineering plant. Assessments of defects at weldments can be highly sensitive to the through-thickness distribution of residual stress assumed in the fracture calculations. Increasingly, finite element modelling approaches are applied to predict residual stress in engineering structures arising from the welding process. However, such methods are complex and require analysts to make many assumptions and approximations. Guidelines covering the calculation of residual stresses in weldments are being prepared for inclusion in the R6 defect assessment procedure and will be accompanied by a series of validation benchmarks. The benchmarks will allow analysts to evaluate and improve the accuracy of weld modelling approaches and assess their suitability for use in fracture assessments. The first part of this paper presents an austenitic stainless steel bead-on-plate weldment validation benchmark based on the extensive round robin measurements performed by members of the European NeT project. The benchmark defines thermal and residual stress performance targets against which a weld simulation approach can be evaluated. Guidance is also provided on how to validate predicted residual stress profiles for use in a high integrity fracture assessment. The second part of this paper provides a commentary on how the weld simulation accuracy and performance targets have been established. (C) 2008 Elsevier Ltd. All rights reserved.