PSI - Issue 65

Emelyanov I.G. et al. / Procedia Structural Integrity 65 (2024) 83–91 Emelyanov I.G., Puzyrev P.I. / Structural Integrity Procedia 00 (2024) 000–000

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excessive pressure, and sometimes operated in contact with hydrogen-containing environments. Negative influence hydrogen-containing environment on the mechanical properties of metals during operation structures is one of the significant factors determining the operation life of many hazardous facilities. Modern shell structures used in the aerospace industry, chemical and hydrogen energy industries are often operated in a hydrogen-containing environment. Hydrogen, when interacting with various metal alloys, can change their properties, both positively and negatively. The negative effect is most often manifested in the form of hydrogen embrittlement, characterized by a significant decrease in mechanical properties when they are saturated with hydrogen above a certain critical level. Issues of interaction of hydrogen with metals have been studied since the beginning of the last century and therefore a huge amount of theoretical and experimental experience has been accumulated. It has been established that the various forms and uncertainty of configurations of the existence of hydrogen in alloys (proton, atom, molecule, hydride, hydrocarbons, etc.) complicate the theoretical study of metal-hydrogen systems, Archakov (1985). The abnormally high diffusion mobility of hydrogen atoms in metals leads to the fact that even the introduction of the first portions of hydrogen is accompanied by a fairly noticeable response of the metal to this effect. However, the structure and properties of metals were mainly studied after saturation with hydrogen, i.e., under thermodynamically equilibrium conditions, therefore, only residual phenomenological effects were recorded, and possible nonlinear effects caused by diffusion were not considered. The issue of the impact of hydrogen-containing environments on the mechanical characteristics of materials has been the subject of numerous monographs, Archakov (1985), Astafiev (1998), Kolachev (1985), Galaktionova (1959). The accumulated experimental material on the hydrogen damageability of metals made it possible to classify the types of hydrogen embrittlement, develop models and theory, and solve some applied problems to increase the hydrogen resistance of structures. However, destruction of metal structures due to hydrogen embrittlement still occurs. The danger of unpredictable destruction of metals under the influence of hydrogen exists, and the reasons for this may be three circumstances presented in the work, Kolachev (1985). Firstly, the variety of forms of manifestation of hydrogen embrittlement, which makes it difficult to predict destruction, and secondly, the low predictability of destruction under the influence of diffusion-mobile hydrogen and the strong influence on this mobility of various physical fields, including force fields. Finally, the uncertainty in the amount of critical hydrogen concentration in the destruction zones significantly affects the accuracy of predictions. To determine the stress state and service life of any metal structure operating in a hydrogen-containing environment, it is necessary to know the changes in mechanical properties during operation, which will depend on hydrogen saturation. This study proposes a mathematical model that allows us to take into account hydrogen distribution in a metal shell structure. To achieve this, it is necessary to solve the boundary problem of hydrogen diffusion and determine the distribution of hydrogen concentration in the structure at various time intervals. It is assumed that the structure under investigation is a cylindrical shell, with a thickness h, with variable geometric and mechanical parameters along the generatrix, which can be subject to a mechanical distributed load q. Figure 1 shows the shell in a curvilinear orthogonal coordinate system s, θ , γ , where s is the meridional and θ circumferential coordinates, γ is the direction of the outer normal to the shell surface (-h/2 ≤γ≤ h/2). 2. Problem statement

Fig. 1. Cylindrical shell.