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environment. The model can be used to forecast pipeline resources, taking into account

internal pressure, the actual concentration of hydrogen in the metal, and the geometric

parameters of the crack.

The results of the dissertation were used in practice at the Scientific and

Production Enterprise with Foreign Investments «UKRTRUBOIZOL» LLC when

performing forecast estimates of the future long-term operation of pipelines under

specific conditions. They also serve to improve existing and develop new technologies

for manufacturing large-diameter pipes for main gas-oil pipelines and heating

networks. This allows for improving product quality and formulating new technical

requirements for them.

Keywords: hydrogen embrittlement; hydrogen concentration; hydrogen diffusion and

trapping; pipeline; pipeline steel; crack-like defect; stress-strain state; finite element

method; stress intensity factor; fatigue crack growth resistance; fatigue fracture;

residual life; material strength; fracture mechanism; mathematical modelling.