Micromechanical estimates of the critical values of j-integral for the steel of steam pipelines

Abstract

We analyze the level of damage to 14MoV63 steel for steam pipelines under the conditions of crack-growth initiation according to the mechanism of ductile fracture. The state of the material after service for about 100,000 h at the power plant is estimated by using a combined experimental and numerical procedure based on the local approach to fracture. The level of damage is determined by analyzing the material taken from the pipeline (aged) and new (virgin) material of the same grade (for the sake of comparison). The critical values of the J-integral are determined on single-edge notched bend (SENB) specimens both experimentally and by using a simplified procedure of local approach without knowing the microstructural parameters. Two micromechanical models are applied: the Rice - Tracey models modified by Beremin (uncoupled) and the complete Gurson model (coupled).