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The main equations of the mathematical model are formulated, which allow

                  to  estimate  the  influence  of  hydrogen  and  mechanical  load  on  the  plastic

                  deformation  of  metal.  It  is  shown  that  hydrogen  can  increase  or  decrease  the

                  dislocation  rate  depending  on  the  conditions  of  hydrogen  concentration,

                  temperature, and applied stress in iron. At low concentrations, hydrogen enhances

                  the movement of dislocations, thereby increasing the rate of plastic deformation.

                         On  the  basis  of  theoretical  concepts  known  in  the  literature  and

                  experimentally substantiated hypotheses, a new mathematical model of hydrogen-

                  induced crack growth in metals under the action of static load was built, taking

                  into account the mechanisms of hydrogen influence on metal deformation, and on

                  this basis, a method for estimating the residual length was developed. eternity of

                  structural elements in water.

                         It has been quantitatively established that for the values of the concentration

                  of pre-absorbed hydrogen, the durability of a plate with a crack is an order of

                  magnitude lower than for the concentration of hydrogen that gradually diffuses

                  from the top of the crack into the prefracture zone. This is due to the fact that the

                  gradual flooding of the prefracture zone first plasticizes it, thereby spitting out the

                  top of the crack, increasing its opening and retarding its propagation. The obtained

                  results indicate that plasticizing the material with hydrogen has a positive effect
                  on the durability of structural elements in hydrogen-containing environments.

                         All  the  theoretical  developments  of  the  thesis  are  brought  to  a  specific
                  engineering methodology for predicting the safe operation of elements of thermal

                  power equipment, taking into account the action of the operating environment.
                         The developed models, methods, and software are used in the Karpenko

                  Physico-Mechanical Institute of the National Academy of Sciences of Ukraine

                  during  the  execution  of  the  topics  of  the  departmental  order  of  the  National

                  Academy of Sciences of Ukraine in the Department of Acoustic Methods and

                  Means  of  Technical  Diagnostics  III-7-20  (state  registration  number

                  0120U101792, 2020 - 2022) and NFDU competitive project No. 2020.02/0049

                  (state registration number 0120U104904, 2020 – 2022).

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