ОЦЕНКА ДЛИТЕЛЬНОЙ ПРОЧНОСТИ ЭЛЕМЕНТОВ КОНСТРУКЦИЙ ПРИ ТЕРМОМЕХАНИЧЕСКОМ НАГРУЖЕНИИ

Abstract

The paper discusses the issue of evaluating strength and service life of critical engineering facilities, the exploitation properties of which are characterized by multi-parametric nonstationary thermal-mechanical effects. The main degradation mechanisms of structural materials (metals and their alloys), characteristic for such facilities, are examined. Basic requirements to mathematical models of such processes are formulated.In the framework of mechanics of damaged media, a mathematical model is developed, which describes processes of inelastic deformation and damage accumulation due to creep. The model consists of three interconnected parts: relations defining inelastic behavior of the material, accounting for its dependence on the failure process; equations describing damage accumulation kinetics; a strength criterion of the damaged material.The results of numerically simulating the carrying capacity of a reactor vessel of a NPP in the event of a hypothetical accident are presented. The accident conditions were modeled by applying pressure modeling the effect of meltdown, constant internal pressure and temperature varying within the part of the vessel in question. The analysis of the obtained numerical results made it possible to note a number of characteristic features accompanying the process of deformation and failure of such facilities, connected with the time and place of the forming macrocracks, the stressed strained state history and the damage degree in the failure zone, etc.In general, the results of comparing the numerical and experimental data make it possible to conclude that the proposed defining relations adequately describe degradation of initial strength properties of the material for the long-term strength mechanism and can be effectively used in evaluating long-term strength of structural elements under thermal-mechanical loading.