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The paper formulates a new calculation model of hydrogen-induced crack

                  growth  in  metals  under  the  action  of  static  load,  which  is  based  on  modern

                  physical and mechanical theories of their deformation and destruction. On this

                  basis, a method of assessing the residual durability of structural elements with

                  cracks was developed, taking into account the mechanisms of hydrogen influence

                  on metal deformation.

                         In particular, a mathematical model of hydrogen diffusion in a piecewise

                  heterogeneous body in a three-dimensional setting was constructed; an algorithm

                  and  corresponding  numerical  programs  were  developed  for  calculating  the

                  distribution of hydrogen concentration in the entire volume of three-dimensional

                  bodies,  taking  into  account  the  effect  of  force  and  temperature  factors.  A

                  certificate of copyright registration for the work №107646 was obtained for the

                  developed program for calculating the concentration of hydrogen in volumetric

                  elements of structures under the action of force loads "DIFEUS 3D".

                         In the case of piecewise heterogeneous bodies on the border of the transition

                  between subregions of homogeneity, the hydrogen solubility function will have a

                  jump, which means that the hydrogen concentration function will also have a

                  jump, which follows from the condition of continuity of the hydrogen chemical

                  potential function throughout the region. For this purpose, instead of the hydrogen
                  concentration,  the  so-called  hydrogen  potential  function,  which  is  continuous

                  throughout the region, was introduced. This made it possible to also obtain an
                  analytical solution of the differential equation in partial derivatives of the 2nd

                  order. As a result, the dependences of hydrogen concentration on time along the
                  grain boundary, in the grain itself, and their total value in the iron bicrystal were


                         Based on the obtained theoretical results, a characteristic value of hydrogen

                  concentration in low-carbon steel, which changes the mechanism of hydrogen's

                  influence on steel deformation, was established, which does not contradict the

                  experimental data known in the literature for this class of steels.

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