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A generalized model is developed for calculating the fatigue limit of the material based on the data on its microstructure. The experimental results of fatigue and cyclic fracture toughness tests and the data on the analysis of the microstructure of two-phase (a b + ) titanium VT3-1 alloy with a different microstructure (globular, bimodal and fine lamellar microstructure) have shown that the dependence of the fatigue limit on the structural parameter, which is responsible for the material fatigue strength, has a nonlinear S-like nature. The formula for calculating the fatigue limit is justified by the data on the microstructural parameters and by the results of static tensile tests of the material, with a fair agreement obtained between the calculated and experimental results. The model has been validated for materials with another type of the crystal lattice [steel containing 0.16% C with a body-centered cubic lattice (bcc) and brass 70/30 with a face-centered cubic lattice (fcc)] and has shown a satisfactory agreement between the experimental and calculation results.Introduction. In view of the current widespread use of advanced structural materials in mechanical engineering and also the extension of the notion about the ultimate potential of traditionally used alloys due to the optimization of their processing, the need to determine the characteristics of resistance to fatigue fracture increases dramatically. It should be noted that the traditional correlation relationships that connect the characteristics of cyclic strength with those of static strength and microstructure cannot be used for novel advanced materials and new processes for manufacturing components as being untested and such that do not provide the desired accuracy for determining the fatigue strength characteristics. The carrying out of experimental studies on the fatigue strength characteristics of new alloys in order to optimize their manufacturing process with the methods specified in current standards results in extremely high consumption of material resources and time. In many cases, an important point is that the required data on the material strength under cyclic loading are to be obtained in the shortest possible time (for instance, to verify the correctness of the engineering design or technology decision made), and the data from traditional long-term tests obtained untimely quite often lose their value.One of the most important parameters of the material microstructure which is currently associated with the fatigue limit is the grain size, d. Already the pioneering studies on the effect of the grain size on the fatigue fracture resistance started as early as the 30s of the last century have revealed that the fatigue limit increases with a decrease in the grain size. However, in a number of papers it was noted that a finer microstructure does not necessarily result in the lifetime change. The linear relationship between the yield stress and the parameter of microstructure 1 d derived in [1, 2] and a similar relationship for the fatigue ...

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