The issues of durability and fatigue life of various structural materials occupy an important place in the operation of equipment and elements subjected to high stresses. To correctly predict its operation time, knowledge of the unique internal structure of a particular piece of operating equipment is required. To obtain such data, a multilevel model of acoustic emission signal flow is proposed in the article, which is based on the kinetic concept of strength and the selection of various stages of destruction in the kinetics of damage accumulation. The selected information, which accounts for the hypothesis of the linear summation of damage, is used in modern models for calculating fatigue life based on kinetic parameters, e.g., the activation energy of destruction and activation volume. The fracture activation energies, activation volume, destructive load, and fatigue life of various structural alloys and steels were calculated using the proposed acoustic emission model based on static test data from various scientific literature sources. For comparison, several methods of calculating kinetic parameters based on the thermal fluctuation concept of strength were used. In addition, numerical modeling was performed to select the structural lethargy coefficient from the elastic deformation zone. The results of the proposed model are in good agreement with the experimental data and allow—within the framework of more thorough tests and with a more accurate consideration of temperature—for the application of an engineering-based approach with which to evaluate the durability and residual service life of objects.

The article presents an approach to assessing the fracture toughness of structural alloys based on thermally activated crack growth and recording acoustic emission signals. The kinetic and structural features of the stable growth of the initiated crack are estimated using a multilevel acoustic emission model based on the time dependence of the logarithm of the cumulative acoustic emission count. The article provides an evaluation of the stable kinetic constants included in the equation of the thermal fluctuation steps of a crack according to literature sources and using the acoustic emission method. It is shown that parameters such as activation energy, activation area before the crack tip, and the rate of non-activation crack growth are stable and show a satisfactory correspondence between the reference literature and real experiments. The approach does not require a set of laboratory experiments to determine the empirical constants of traditional crack growth rate equations, and it also differs in that it takes into account the unique features of the destruction of a particular specimen or technological equipment and allows for a non-destructive assessment of fracture toughness. The values obtained are conservative. The concentration criterion of destruction requires further investigation.