51312-01152-A Phenomenological Model for Environmentally Assisted Cracking of Pipeline Steels in Near-Neutral pH

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Product Number: 51312-01152-SG

ISBN: 01152 2012 CP

Author: Baotong Lu

Publication Date: 2012

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A phenomenological model is proposed for the environmentally assisted cracking of pipeline steels in the near-neutral pH soil environment based on the following hypotheses: (1) cracking is dominated by the corrosion fatigue promoted by hydrogen embrittlement; (2) the cracked pipes considered are under the K-dominative condition (3) there is a fracture process zone (FPZ) in the plastic zone ahead of the crack tip within which the ductility of material declines because of the hydrogen-enrichment produced by the stress-assisted diffusion; (4) the microcrack(s) initiate as the local strain exceeds the fracture ductility propagate with increasing load and eventually connect with the main crack leading to crack growth; (5) the crack growth rate is a power function of the FPZ size. The comparison with the data of laboratory indicates that the new model can provide reasonable predictions for the dependence of the crack growth rates on the stress intensity factor stress ratio loading frequency solution pH and electrochemical potential. The crack dormancy conditions have been characterized by employing the concept of threshold of crack growth. The dependence of crack dormancy on the stress ratios loading frequency and environmental variables is formulated by the model developed in this study.