Keyword: «stress intensity factor»

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.

It is assumed that the decrease in crack resistance at low temperature may be associated with a decrease in the size of the plastic zone. A large plastic zone has the effect of «blunting» the crack tip. With a decrease in temperature, due to an increase in the yield strength and a decrease in the size of the plastic zone, this effect is significantly reduced, which leads to a significant decrease in crack resistance. Using a combination of classical mechanics and fracture mechanics approaches, an associated expression for a crack resistance is obtained. The expression qualitatively describes the experimentally obtained curves of the ductile-brittle transition zone. It is shown that, in addition to such factors as the scale effect, features of the crystal structure of the metal, the parameters of classical mechanics and fracture mechanics can make a significant contribution to the phenomenon of cold brittleness.