A thermodiffusion problem of hydrogenation of a steel shell structure

The processes of heat transfer and diffusion in metals are characterized by different physical periods. However they are described by structurally similar equations of mathematical physics. This fact is used in the paper to adapt the well-defined mathematical principles set for heat transfer to the purposes of solving the problems of hydrogen diffusion into metals. An approach is assumed which is based on the substitution of the heat transfer equation with an equivalent variable equation utilized to calculate parameters of complexly shaped bodies and boundary conditions of various types via the finite-element method. The necessity of utilizing the numerical methods used in the research is dictated by the main direction of the algorithm applied to the determination of the interrelated influence of hydrogen and mechanical stresses on the kinematics of deformation and fracture of structural elements. The calculation of the stress-strain state of actual structural elements is carried out by means of numerical methods only. An analytical solution of the problem of heat distribution in a rod is utilized to test software based on the finite-element method. The goal of the research is to develop an approach necessary to solve a related thermodiffusion problem of hydrogen saturation in a steel shell structure and to determine the law of hydrogen concentration distribution in the body of a shell depending on temperature and the hydrogen concentration at the boundaries. As an example, a problem of hydrogen penetration into the wall of a diffusion device is solved. The solution would allow one to evaluate changes in the mechanical properties of materials and the service life of a product. The approach proposed here has allowed us to determine the kinematics of the processes of heat transfer and hydrogen saturation in steel walls of a cylindrical section of the device. The applied importance of the results obtained is based on the fact that the temperature, pressure and concentration of hydrogen over the inner surface are in correspondence with the operational conditions.