Kravchuk A. Determination of energy characteristics of fracture and their anisotropy for heat-resistant steels at impact bending

The object of study is the process of cracks initiation and propagation in of different types specimens under static and dynamic loading. The purpose of the work is to establish the laws of fracture and anisotropy of energy characteristics during cracks initiation and propagation in heat-resistant steels of the NPPs 1st circuit under impact bending tests. Research methods - experimental and numerical methods for studying the initiation and propagation of cracks under static and dynamic loading. Theoretical and practical results are: new data on energy characteristics were obtained and regularities of fracture during crack initiation and propagation in specimens of heat-resistant steels 22K, 10GN2MFA, 15Kh2NMFA of the NPPs 1st circuit were established taking into account anisotropy of their properties. The scientific novelty of the obtained results is to establish the regularities of variation of fracture energy characteristics depending on temperature and their anisotropy, as well as the velocity of crack propagation depending on its direction during impact bending of specimens from heat-resistant steels in characteristic areas of ductile and brittle fracture, and establishment the relationship between the specific fracture energy under impact bending of Charpy specimens and the critical stress intensity factor. The results of the dissertation work were used in the development of recommendations for improving the normative base, as well as for solving important issues for the nuclear power industry of Ukraine: life-time assessment and searching for additional strength reserves for the elements of the primary circuit equipment of the South-Ukrainian NPP and Rivne NPP. The obtained results can be used to increase the accuracy and reliability of assessing the strength and life-time of the NPPs 1st circuit equipment elements using new data on the fracture energy characteristics of heat-resistant steels 10GN2MFA, 22K and 15Kh2NMFA.