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SUMMARY

Soviak I. M. Computational and experimental model for predicting the influence

of hydrogen concentration in metal on the durability of a pipeline with a crack-

like defect. – Qualifying scientific work on the rights of the manuscript.

Dissertation for the degree of Doctor of Philosophy in Specialty 113 «Applied

Mathematics». Field of knowledge 11 «Mathematics and Statistics». – Karpenko Physico-

Mechanical Institute of the National Academy of Sciences of Ukraine, Lviv, 2026.

The dissertation is devoted to mathematical modeling and computational-

experimental forecasting of the influence of hydrogen concentration in metal on the

residual durability of a pipeline with a crack-like defect. The importance and relevance

of this research lie in the fact that pipeline systems for transporting hydrogen-

containing environments during long-term operation undergo operational damage,

ultimately leading to the appearance of crack-like defects in the pipe wall. Defects of

this type are extremely dangerous, since their unpredictable development can lead to
catastrophic failure of some sections of the pipeline, causing significant economic and

environmental losses.
The paper formulates a computational and experimental model to assess the

residual durability of a pipeline with an internal semi-elliptical crack, taking into
account the value of the hydrogen concentration in the metal, which is considered a

key parameter in this study. The model is based on a combination of calculation of the

stress-strain state in the vicinity of the crack contour, mathematical description of

hydrogen diffusion and trapping in pipeline steel, experimental determination of the

characteristics of its cyclic crack resistance depending on hydrogen concentration in

the metal, and calculation of the fatigue crack growth period to the critical size, which

determines the residual durability of the defective pipeline element.

A three-dimensional finite element model of a pipeline fragment with an internal

semi-elliptical crack under internal pressure is constructed. The fields of hydrostatic