Keyword: «stress field»

The necessity of studying the dependence between the acoustic emission (AE) total count emanating from the crack tip and the stress intensity factor (SIF) is substantiated. A hypothesis is proposed that the distribution of the density of AE sources at the crack tip is uneven, has a probabilistic nature and is described by the Weibull distribution. The density distribution of AE sources at the crack tip is modeled, and the AE total count predicted by this model under primary quasi-static loading is calculated. It is shown that the proposed intensity distribution of AE sources at the crack tip leads to a relationship between the AE total count and SIF that is closer to the experimental data. Examples of calculations are given according to the proposed model, the results of which indicate the presence of a clear dependence of the exponent in the expression of the number of AE acts on the SIF on the presence of the given in this paper or similar spatial distribution of the density of AE sources.

The article investigates the influence of temperature on the stress triaxiality in the prefracture zone at the crack tip. Based on the asymptotic expansion of stress tensor components, the concept of an effective stress triaxiality coefficient, calculated at the boundary of the plastic zone, is proposed. An analytical relationship between the effective stress triaxiality coefficient and temperature has been established via the temperature dependence of the yield strength, described by the thermally activated flow model. It is shown that a decrease in temperature leads to a monotonic increase in the effective stress triaxiality coefficient. The obtained results provide a quantitative explanation for the physical mechanism of cold brittleness: an increase in stress triaxiality with decreasing temperature creates favorable conditions for the transition from a ductile to a brittle fracture mechanism.

The paper presents an investigation of the stress triaxiality distribution in the vicinity of a crack tip. It has been established that the stress triaxiality values remain finite at the crack tip despite the presence of stress field singularity. The study demonstrates that positive T-stresses lead to a more pronounced decrease in stress triaxiality with increasing distance from the crack tip compared to negative T-stresses. A significant difference in triaxiality levels between plane stress and plane strain conditions has been identified. Under plane strain conditions, the stress triaxiality exceeds that of plane stress conditions by a factor of three, which explains the increased susceptibility to brittle fracture when deformation is constrained in the thickness direction.