PSI - Issue 40

2

Vladlen Nazarov / Structural Integrity Procedia 00 (2022) 000 – 000

342 © 2022 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the15th International Conference on Mechanics, Resource and Diagnostics of Materials and Structures. Keywords: Cylindrical tube; internal pressure; radial displacement; porosity; hydrogen corrosion at high temperature. 1. Introduction In the industry of fuel energy, in order to increase the efficiency of power plants, it is proposed to use water vapor Bogomolov et al. (2011) with high pressure and temperature parameters. It is proposed to use hydrogen as a fuel, which can enter into a chemical reaction with the material of the reactor in the form of a thick walled steel cylindrical tube Bebelin (1997). Since the operating temperature of the reactor can be higher than the temperature of dissolution of carbides in steel, a chemical reaction involving hydrogen and carbides will be possible either when the reactor is heated or cooled. Decarburization of steel can affect the strength and service life of the reactor for generating steam with high pressure and temperature parameters. Vladlen Nazarov et al. / Procedia Structural Integrity 40 (2022) 341–347

Nomenclature sec 

relative increase in the cross sectional area of the cylindrical tube porosity or relative change in the area of an infinitely narrow ring



cross sectional area

s

a b ,

internal and external boundary radii after deformation radial displacements in incompressible material radial displacements in compressible material

r u r u



radial strain

r 

tangential strain

 

h p pressure of products (methane gas) after chemical interaction of hydrogen and steel tube carbides h c concentration of products (methane gas) after chemical interaction of hydrogen and steel tube carbides h eq c equilibrium concentration of methane gas h t time of decarburization of steel The process of initiation of main cracks in a cylindrical tube under the internal pressure of gaseous hydrogen under creep conditions at high temperatures has two features, which are determined by the possibility of chemical interaction of diffusing hydrogen from the cavity with the material of the cylindrical tube. In the absence of such a chemical interaction, the main crack is one (rarely two) and it originates at the outer boundary radius at which the effective tangential stress takes the greatest value and reaches the ultimate strength. When the chemical reaction of hydrogen with steel carbides proceeds, gaseous methane is formed, which accumulates in micropores Natan et al. (1983). When the methane pressure reaches a critical value, micropores will begin to join and form main cracks. Under conditions of hydrogen corrosion, main cracks will form on the inner boundary radius of the cylindrical tube Shannon et al. (2004). When describing the onset of the fracture process or the process of hydrogen corrosion, the dependence of porosity on the radius may be required. 2. Assumptions and geometric As a rule, when determining the stresses and strains in a cylindrical tube inflated by internal pressure, the material is considered incompressible King et al. (1967) and Bhatnagar et al. (1974) and Gupta et al. (2001) and Singh et al. (2010) and Sharma et al. (2018) and Gagandeep et al. (2020). In fact, micropores can form during deformation. These micropores can influence the degradation process. For this purpose, we will consider the process of axisymmetric deformation of a cylindrical tube (Fig. 1) taking into account the process of pore formation.