ЧИСЛЕННОЕ МОДЕЛИРОВАНИЕ УСТАЛОСТНОЙ ДОЛГОВЕЧНОСТИ ДЕТАЛЕЙ АВИАЦИОННЫХ ГТД ПРИ ЦИКЛИЧЕСКОМ ДВУХЧАСТОТНОМ НАГРУЖЕНИИ

Abstract

The problem of assessing the resource characteristics of responsible engineering facilities, taking into account the peculiarities of operational loading modes, is discussed. The processes of fatigue durability of polycrystalline structural alloys under cyclic two-frequency loading (with the combined action of mechanisms of low and multi-cycle fatigue) are considered. A mathematical model describing the processes of cyclic elastoplastic deformation and accumulation of fatigue damage in structural alloys under multiaxial disproportionate modes of combined thermomechanical loading has been developed from the modern positions of damaged medium mechanics and fracture mechanics. The model consists of three interrelated parts: relations determining the cyclic elastic-plastic behavior of the material, taking into account the dependence on the destruction process; evolutionary equations describing the kinetics of fatigue damage accumulation; criteria for the strength of the damaged material. The variant of the defining elastic-plasticity relations is based on the idea of the yield surface and the principle of gradiency of the velocity vector of plastic deformations to the yield surface at the loading point. This version of the equations of state reflects the main effects of cyclic elastic-plastic deformation of the material for arbitrary folded loading trajectories. The variant of kinetic equations of fatigue damage accumulation is based on the introduction of a scalar damage parameter, is based on energy principles and takes into account the main effects of formation, growth and fusion of microdefects under arbitrary complex cyclic loading regimes. A joint form of the evolutionary equation of fatigue damage accumulation in the areas of low- and multi-cycle fatigue is proposed. As a criterion of the strength of the damaged material, the condition of reaching the critical value of the damage value is used. The results of numerical simulation of fatigue durability of a compact sample (model of the disk deflector of the high pressure turbine of an aviation gas turbine engine) are presented with cyclic two-frequency loading. The results of the comparison of the calculated and experimental data showed that the proposed model qualitatively and with the accuracy necessary for practical calculations quantitatively describes the fatigue life of structural elements under cyclic two-frequency loading.