Fracture Mechanics Approach to Stress Corrosion Cracking of Pipeline Steels: When Hydrogen Is the Circumstance
Stress corrosion cracking is a problem of major concern in pipeline steels. This paper deals with the fracture mechanics approach to the phenomenon. Paraphrasing the famous sentence by Ortega y Gasset “yo soy yo y mi circunstancia”, one could say that the material is itself and its circumstance, the latter being the physico-chemical and mechanical environment. The paper analyzes situations in which the circumstance enhances hydrogen embrittlement. A theoretical study is provided of the validity of the fracture mechanics approach to hydrogen assisted cracking, analyzing the K-dominance condition to elucidate the role of the far field and the effect of history, the latter recalling the words of the Spanish poet Antonio Machado: “hoy es siempre todavía”, and perhaps T. S. Eliot’s “and all is always now”.
KeywordsStress Intensity Factor Crack Growth Rate Hydrogen Concentration Linear Elastic Fracture Mechanic Hydrogen Diffusion
Many results summarized in this paper are taken from previous works reported in the list of references. Special acknowledgement is gratefully given to the co-author of such papers: Dr. Viktor Kharin (formerly with the Pidstryhach Institute for Applied Mechanics and Mathematics of Lvov, now Associate Professor at the University of Salamanca).
Previous research works in which this paper is based were funded by the Spanish Institutions CICYT (Grant MAT97-0442), DGICYT (Grants UE94-0001 and SAB95-0122), and Xunta de Galicia (Grants XUGA 11801A93, 11801B95 and 11802B97) and the European Institutions CEE (Human Capital and Mobility) and NATO (Scientific Programme).
In addition, the author wishes to thank the financial support of his research at the University of Salamanca provided by the Spanish Institutions MCYT (Grant MAT2002-01831), MEC (Grant BIA2005-08965), MCINN (Grant BIA2008-06810), JCyL (Grants SA067A05, SA111A07 and SA039A08).
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