Journal
ENGINEERING FRACTURE MECHANICS
Volume 185, Issue -, Pages 210-226Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.engfracmech.2017.05.021
Keywords
Hydrogen embrittlement; Cohesive zone models; Hydrogen diffusion; Finite element analysis; Fatigue crack growth
Categories
Funding
- Ministry of Economy and Competitiveness of Spain [MAT2014-58738-C3]
- People Programme (Marie Curie Actions) of the European Union's Seventh Framework Programme (FP7) under REA [609405]
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We present a compelling finite element framework to model hydrogen assisted fatigue by means of a hydrogen- and cycle-dependent cohesive zone formulation. The model builds upon: (i) appropriate environmental boundary conditions, (ii) a coupled mechanical and hydrogen diffusion response, driven by chemical potential gradients, (iii) a mechanical behavior characterized by finite deformation J2 plasticity, (iv) a phenomenological trapping model, (v) an irreversible cohesive zone formulation for fatigue, grounded on continuum damage mechanics, and (vi) a traction-separation law dependent on hydrogen coverage calculated from first principles. The computations show that the present scheme appropriately captures the main experimental trends; namely, the sensitivity of fatigue crack growth rates to the loading frequency and the environment. The role of yield strength, work hardening, and constraint conditions in enhancing crack growth rates as a function of the frequency is thoroughly investigated. The results reveal the need to incorporate additional sources of stress elevation, such as gradient-enhanced dislocation hardening, to attain a quantitative agreement with the experiments. (C) 2017 Elsevier Ltd. All rights reserved.
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