Mathematical simulation of low cycle fatigue of high-loaded engine parts

Abstract

The paper discusses main aspects of low cycle fatigue influence on the lifetime of engine parts. The importance and history of the problem, the main experiments and the effects impacting the low cycle fatigue of structural materials are described. A hypothesis about the existence of a thermomechanical surface of structural material, generalized to the case of a cyclical loading was used to approximate the loops of cyclic nonisothermal elastoplastic deformation curves. The cyclic deformation curve model is based on the following three parameters: the elastic modulus during unloading, the Bauschinger effect and the conversion parameter of the nonlinear part of its first halfcycle. This model also accounts for the accumulated plastic strain, as well as the testing temperature. The criterion of durability is formulated, based on the dependence between the number of halfcycles to failure and the accumulated plastic deformation. Deformation theory of plasticity, generalized to the case of cyclic deformation, in combination with the durability model and technology of ''dying'' elements is applied to the finite element analysis of low cycle fatigue of gas turbine engine parts. The results of calculations are demonstrated. Keywords: Gas turbine engine, Low cycle fatigue, Nonisothermal plasticity, Finite element modeling, Durability modeling, Cyclic loading