3D Stress Criteria Guidelines for Application

This report provides guidelines for assessing stress results from 2D and 3D finite element analyses, in terms of the ASME Boiler and Pressure Vessel Code stress limits in the design by analysis Section III (Class 1, NB) and Section VIII, Division 2. An initial project (report included in this Bulletin) presents six short-term recommendations, four areas for additional consideration, and a number of issues requiring long-term research. A subsequent project (Guidelines) addresses four areas of consideration as the principal topic of this Bulletin: 1. The relation between failure mechanisms and the ASME Code stress categories; 2. The appropriate stresses for each category; 3. The appropriate locations for assessing each stress category; 4. The appropriate stresses for obtaining the membrane-plus-bending stresses. To enhance understanding of the four areas of consideration, eleven geometries are defined and evaluated through discussion and finite element results. Each of the four areas of consideration are discussed in detail and 2D axisymmetric and 3D example geometries are presented. Recommended code guidance is presented in a set of recommended guidelines which Sections VIII and III of the Code are using to develop a general appendix on finite element analysis. The guidelines address the failure modes that relate to membrane stresses, bending stresses, and membrane-plus-bending stresses, types of analyses for stress assessment, locations for evaluation, stress classification lines and planes and calculating membrane and bending stresses (linearization, principal stress and stress intensity).