Thermodiffusion problem of determining the stress state of a steel shell structure

Abstract

In various engineering industries, including railroad transport, metal structural elements are sometimes operated under external thermomechanical loads while being also exposed to aggressive environments. The impact of an aggressive environment on the mechanical properties of metals is one of the dominant factors, which determines structure strength and service life, as it usually deteriorates the mechanical properties of materials. The thermodiffusion problem of determining the stress state of a steel shell structure is considered. The subject of the study is a compound steel shell of revolution loaded with internal pressure and operating in a hydrogen-containing environment at high temperatures. The purpose of this study is to determine the stress state of the shell taking into account the changes in the mechanical properties due to simultaneous exposure to temperature and hydrogen. In the suggested approach, the thermodiffusion and mechanical problems are coupled by taking into account the changes in stress-strain diagrams of steel samples as temperature and hydrogen concentration increase. The boundary problem of heat conduction and diffusion is solved using the finite elements method. The system of differential equations for the boundary problem of shell stress state is integrated using S. K. Godunov’s method of discrete orthogonalization. The method is based on stepwise orthogonalization of the solution vectors of the Cauchy problem. The obtained solution allowed determining the site of maximal stresses and drawing conclusions on the strength of the studied structure when increasing hydrogen concentration and internal pressure.