The process of brittle failure is considered as a hierarchical stochastic process of defect development at the micro-, meso- and macrostructural levels. The limit states of each level are determined by the lines of microhardness levels. According to the approach of A. A. Ilyushin and its development by V. G. Zubchaninov, the fatigue failure process is determined by the loading process. According to the model of scale-structural fatigue, a system of constitutive relations is written for the probability distribution function of brittle failure depending on the loading process, and high-cycle fatigue curves are constructed based on defect levels at irregular cyclic loading. For alloy 2024-T42 and steel S25C at symmetric loading consisting of two and three blocks with different amplitudes and numbers of cycles, the results of calculations using the model and their correspondence to experimental data are presented.

Eleonora B. Zavoychinskaya, Doctor of Sciences in Physics and Mathematics, Professor; e-mail: elen@velesgroup.com; https://orcid.org/0009-0001-9642-5008; AuthorID: 8942

Georgii E. Lavrikov, Student; e-mail: george.lavrikov@yandex.ru; https://orcid.org/0009-0003-8258-2066; AuthorID: 1197792