A Local Approach to Brittle Fracture Analysis and Its Physical Interpretation

The paper presents a review of studies dedicated to the development of a local approach to brittle fracture in metals and alloys. To work out a statistical criterion of local fracture in a metal in the vicinity of a stress concentrator is shown to be the key task of the local approach. The author substantiates a possibility of describing the process of brittle (quasibrittle) fracture in metals ahead of the notch on the basis of “primary principles,” i.e., on the basis of the analysis of the processes of formation and catastrophic growth of crack nuclei. The physical effects have been established, which must be allowed for in the development of the local fracture criterion. The author considers the main factors that govern the size of the “process zone.” This parameter has been found to depend on the value of the relative gradient of the local plastic strain intensity. The appropriateness of using the Weibull distribution to describe quasibrittle fracture of metals is analyzed. It is demonstrated that the Weibull parameters are not material's constants as postulated in the conventional variant of the local approach. Their values depend on the local plastic strain and the metal stress state in the vicinity of the stress concentrator.