Influence of the modes of thermomechanical preloading on the resistance of heat-resistant steels to brittle fracture

We describe the methods and results of the experimental investigation of the influence of various modes of thermomechanical preloading on the resistance of nuclear pressure-vessel steels to brittle fracture. We studied specimens of different thickness (25-150 mm) made of the base and weld metals of the vessels of water-moderated, water-cooled nuclear power reactors. The materials under consideration belong to different strength classes. It is shown that the postive effect of thermomechanical preloading is preserved or even strengthened after the subcritical ductile growth of a crack in the process of preloading. We compare the available experimental data with the results of numerical calculations performed by using the Chell model. It is shown that the Chell model fails to explain some experimental data. Materials studied include 15Kh2MFA and 15Kh2NMFA heat-resistant steels.