Title: Simulation of quasi-brittle fracture

Abstract

Perfectly brittle or just fragile destruction occurs without plastic deformation. Quasi-brittle fracture involves the presence of a plastic zone in front of the crack edge. Purpose: to describe the factors that determine crack resistance in quasi-brittle fracture. It was assumed that the stress-strain state near the crack tip in quasi-brittle fracture can be described on the basis of: a) known numerous experimental observations, namely: at a certain stage of loading plastic deformations are localized in two, symmetrical with respect to the crack plane, bands (straight lines) of fluidity; b) the assumption that the stress-strain state near the crack tip is adequate to the stress state of the soft layer, in both cases the development of plastic deformations is maintained by neighboring areas where the yield strength is not reached; c) radiographic studies of the newly formed fracture surface, which allow to determine the energy costs of quasi-brittle fracture [8], the proposed formulaК_(1с ) = 0,5σв (3h0)1/2, де σв [МРа] – temporary resistance to destruction; h0 [m] is the height of the irregularities of the newly formed surface. In this paper, we propose the conclusion that a detailed description of the stress-strain state near the top of the separation crack under conditions of plane deformation is not mandatory. Destruction by crack propagation is unambiguously determined by the coordinates of points A and B. Most likely the coordinates of the points are as follows:А(0;σ0,2); В(х0;σut), де σ0,2 – is the conditional yield strength [MPa]; σut - maximum, theoretical strength [MPa]; х0 = k (σut - σ0.2) [m]. Determining the proportionality factor k requires additional research. If σ0.2 = σut , then there is absolutely fragile destruction. As the yield strength σ0,2 increases with decreasing temperature, the fracture becomes more brittle.