TDFAD APPROACH TO HIGH TEMPERATURE DEFECT ASSESSMENT AND ITS ENGINEERING APPLICATION

摘要

＜正＞From the idea of failure of defective structures at high temperature being controlled by two mechanisms: fast fracture due to creep crack growth initiating at the crack tip and creep rupture on the weakened section, a time-dependent failure assessment diagram （TDFAD） is developed on the basis of the time dependent crack tip parameter J integral. According to the proposed TDFAD method, detailed crack initiation and creep crack growth analysis is avoided in safety assessments of high temperature structures by performing simple calculations of stress intensity factor and limit load. To evaluate the creep toughness parameter Kmat, three different expressions are suggested on the basis of experimental load-line displacement, creep crack initiation and growth parameters as well as the isochronous stress-strain curve. The influence of service factors such as temperature and service-time on the proposed TDFAD is discussed by using the properties of 2.25CrlMo steel and an example is also presented to illustrate t