EXPERIENCES USING 3-DIMENSIONAL FINITE-ELEMENT ANALYSIS FOR LEAK-BEFORE-BREAK ASSESSMENT

Because of practical limitations, analytical problems in fracture mechanics have often been solved using simplified geometries (e.g. plane stress/strain, shell models). We have applied the Leak-Before-Break approach extensively to the large diameter piping of a new nuclear power plant. Various piping components such as elbows, tee and branch connections with postulated cracks were analyzed. Since no credible geometric simplification was possible, fully three-dimensional (3D) analytical models were found to be essential. The paper describes our experiences in performing 3D Finite Element (FE) analysis of these components. Included are comparisons of numerical and test results of compact specimens, material modeling considerations, handling of 3D effects, such as the variation of the J-integral along a crack front, and especially, the effects of plasticity. The overall intent of the paper is not simply to present specific numerical results, but rather to give some perspective on the effort required and results attainable. © 1990.