| Popis: |
Further development of power and, primarily, engine engineering is associated with significantly increasing specific indicators. For example, the main trend in development of gas turbine engines is to increase gas parameters before the turbine. At the same time, there is an intensive growth of thermal and mechanical tension, and first of all this applies to the parts and components of the flow range. The destruction of these structural elements may have grave consequences. Increasing reliability and durability of responsible components of engines under operating conditions of complex cyclic thermo-mechanical loading is one of the priority tasks of modern engine engineering.One of the factors to determine a design performance is high-temperature creep. When solving the problems of deformable solid mechanics (DSM) in terms of creep, various options of the theory of hereditary creep and three main technical theories of aging, flow and hardening are widely used. There are also theories known that use an apparatus of the structural models and mechanical analogues to describe the creep. Most theories satisfactorily describe the creep strain under constant or slowly changing loads. Analysis of stress-strain states under variable loads is better described by the theories of flow and hardening, and the theory of hardening has some advantages over the theories of flow, as it gives more exact approximation for experiment results. From the point of view of the computing cycle arrangement, the technical theories have well-known advantages over the hereditary ones.When using the finite element method (FEM) to solve the boundary value problems of DSM considering the creep strain, an explicit or implicit Euler scheme is very often used. Depending on the features of the problem under consideration, a solution algorithm is constructed either in accordance with the method of initial stress, or by the method of initial strains. The method of initial strains when solving the problems in terms of creep is used more often, because the application of an initial stress method for this class of problems is technically much more complicated. The paper examines the explicit and implicit Euler schemes in combination with FEM. Both schemes are formulated in accordance with the method of initial strains. A constitutive relation was chosen in the form of the theory of flows. |
