Estimation of Fracture Mechanics Parameters Under Displacement-Controlled Elastic Plastic Fatigue Conditions

Abstract

Accurate prediction of the residual life of components under long-term service is urgently needed due to requirements for the reduction of the maintenance costs of thermal power plants. Quantitative prediction of crack growth under displacement-controlled conditions such as thermal fatigue is a key to the fulfillment of this need. In a previous paper, the present authors proposed a simplified prediction method of fracture mechanics parameters such as J and C* of a perforated plate under thermal fatigue, on the basis of the reference stress approach under displacement-controlled conditions. In this paper, the fracture mechanics parameters of a CCT specimen and structural models of CrMoV cast steel under displacement-controlled conditions were numerically and experimenttally examined on the basis of the proposed method. The ratio of the elastic and the inelastic crack opening displacement, as well as the ratio of the elastic and the inelastic load point displacement, was used to correlate the fracture mechanics parameters in the elastic and inelastic region. As a result of the study, the proposed method based on displacement was found to be insensitive to small variation in the predicted results of macroscopic load in comparison with the original reference stress method, and is considered to be applicable to displacement-controlled conditions such as thermal fatigue.