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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
constructed.
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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