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Published on: January 16, 2019
Modeling hydrogen-assisted fatigue crack growth in low-carbon steel focusing on thermally activated
1Department of Mechanical Engineering, Kyushu University, Fukuoka, Japan.
Abstract:
Hydrogen-assisted (HA) fatigue crack growth (FCG) occurs in ferritic steels, wherein H-dislocation interaction plays a vital role. We aim to model the HAFCG mechanism based on the obstruction of dislocations within the crack tip zone. Our modeling framework is as follows: H is condensed into crack tip and trapped by dislocations; these H significantly decrease dislocation mobility; stress relief via crack blunting is suppressed; localized brittle fracture triggers HAFCG. This model was substantiated experimentally in H2 gas at various load frequencies and temperatures. Theoretical formulations were established considering the thermal equilibrium of H-trapping and dislocation breakaway from the H atmosphere.
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