PSI - Issue 40

I.G. Emel’yanov et al. / Procedia Structural Integrity 40 (2022) 124–128 I. G. Emel’yanov / StructuralIntegrity Procedia 00 (2022) 000 – 000

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consideration of all possible factors of the influence of forces, temperature and environment on the material of the structure. And the study of the mechanical properties of materials is usually carried out for standard experiments of the same type in terms of the nature of loading. It is impossible to experimentally investigate the material for all the variety of possible combinations of loads of different physical nature that arise during the operation of structures. Therefore, the lack of the necessary information sometimes has to be compensated for by model representations. This article proposes a method for determining the stress state and the limiting state of a shell metal structure – a muffle, under thermomechanical loads. The studied muffle is a thin-walled steel shell of revolution with a flat cover, loaded with an internal excess pressure of a hydrogen-containing gas and non-stationary thermal heating. The muffle is designed for high-temperature annealing of electrolytic steel in bell-type furnaces. Under the action of operational loads, noticeable permanent deformations are formed in the muffle structure. 2. PROBLEM STATEMENT The problem of determining the limiting state of a thin-walled metal structure under non-isothermal loading processes and taking into account contact with an aggressive medium can be represented as consisting of several independent tasks: 1) development of a model of the structure under study, which makes it possible to determine its stress state under a thermomechanical load. 2) development of a model of the structure under study, which makes it possible to determine the non-stationary temperature distribution. 3) Determination of the mechanical parameters of the construction material under thermomechanical loading and taking into account the influence of an aggressive environment on the mechanical parameters of the material. 4) Selection of the criterion for the limiting state of the structure. 3. ASSUMPTIONS AND METHODS FOR SOLVING THE PROBLEM Determination of the stress state of the muffle shell. The main element of the muffle is a cylindrical shell and a flat round cover made of St3ps steel. Inside the structure there is nitrogen gas with hydrogen content and overpressure. During operation, thermomechanical loads from its own weight, excess pressure and thermal radiation will act on the shell. Thus, given the vertical arrangement of the structure, its stress state will be axisymmetric. When determining the stress state of the muffle shell, we will use the classical shell theory based on the Kirchhoff – Love hypotheses, Grigorenko and Vasilenko (1981), Donnell (1976). The shell under study, with thickness h , is determined by a continuous median surface with curvilinear orthogonal coordinates s ,  ,  (Fig. 1). Where s – meridian and  – circumferential coordinates.

Fig. 1. Shell of revolution.

Taking into account that the stress state of the investigated structure will be axisymmetric, the problem will be described by a system of six ordinary differential equations, Shevchenko and Prokhorenko (1981), Emelyanov and Mironov (2012), Babeshko and Shevchenko (2007),