One of the modern problems of the resource and safety operation estimation in turbines and compressors of gas and steam turbine construction is to study the relations of the stochastic process of micro- and macrocracks nucleation and growing in blades at operational high cycle and gigacyclic fatigue. It has been experimentally found that micro- and macrocracks occur perpendicular to the axis of the blade in the stress concentration zone root section from the bending forms of forced resonance vibrations. In general, the axial stress may be presented as the sum of the constant component and the discrete spectrum with a set of amplitudes and phase deviations between the components. Here is consider the blade asymmetric single-frequency axial loading, for which a constant stress component is determined by the known relations for an elastic cantilever beam as the maximum value of the sum of tensile stress from centrifugal forces and bending from aerodynamic forces at the point of their application, and the stress amplitude is found on a well-known solution of the bending problem for various deflections of rigidly fixed to the disk elastic beam without ties. The proposed method of the blade resource estimating at the loading is based on the theory of material scale-structural fatigue, according to which the stochastic fatigue process is considered at six scale-structural levels corresponding to different stages of the material evolution by various physical mechanisms. A hierarchical system of constitutive relations for the failure probability at the micro-, meso- and macrolevels is defined. It is chosen the stress amplitude as a variable, and material functions are determined according to standard fatigue strength tests taking into account the results of brittle cracks evolution studу and depending on the asymmetry parameter. Here is carried out the identification of basic constants for high cycle and gigacycle fatigue of no endurance materials. For each level of defects, fatigue curves are determined. The results for VD17 aluminum alloy and ZhS6K nickel alloy blades are discussed. By comparing the theoretical calculation with experimental data, the method is confirmed.
Завойчинская Э.Б. О методе оценки ресурса лопаточного аппарата газотур- бинного двигателя при асимметричном циклическом нагружении. Математиче- ское моделирование и численные методы. 2020. № 1. с. 45–63