Physical Fundamentals of a Local Approach to Analysis of Brittle Fracture of Metals and Alloys

Abstract

We give a review of original investigations and the literature data on the local approach to the description of brittle (quasibrittle) fracture of metals with emphasis on the physical aspect of the problem. Two variants of the local approach are considered, namely: deterministic and probabilistic ones. We show that the local fracture stress σ _F is not a constant but varies depending on the local plastic deformation and the degree of its inhomogeneity. We establish that a considerable excess of the local fracture stress over the brittle strength of a metal R _MC under uniaxial tension is caused by a scale effect related to the localization of the induced fracture in an extremely small region. We consider a new variant of the local approach to brittle fracture without the Weibull distribution. In this case, the probability of fracture is found by computer simulation of the processes of formation of incipient cracks and loss of their stability. This approach enables us to separate the influence of the microstructure of a metal and its stress-strain state in the vicinity of a notch or a sharp crack on the local fracture stress. We established three main factors that control the regularities of micro- and macrofracture of a metal under conditions of stress concentration. These factors are the distribution of the lengths and orientations of incipient cracks and their density.