Prediction of Fracture Mechanics Parameters for Cracked Structures under Displacement-Controlled Elastic-Plastic Fatigue Conditions
Takumi TOKIYOSHI, Toshihide IGARI, Akihiro KANAYA and Hironori KINO
Abstract:Quantitative prediction of crack growth under displacement-controlled conditions such as thermal fatigue is a key to the residual life prediction of plant components. In a previous paper, the 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 experimentally and numerically examined on the basis of the proposed method. The ratio of the inelastic and the elastic crack opening displacement, as well as the ratio of the inelastic and the elastic load point displacement, was used to correlate the fracture mechanics parameters in the inelastic and elastic regions. The proposed method based on displacements was found to be insensitive to a small variation in the predicted macroscopic load in comparison with the original reference stress method, and is considered to be applicable to displacement-controlled conditions such as thermal fatigue. Key Words:Fracture mechanics, Elastic-plastic fatigue, Displacement-controlled fatigue, Inelastic analysis, CrMoV cast steel