Finite element calculations in support of stress corrosion crack propagation

摘要

Stress corrosion cracking (SCC) results from an interaction between a stressed material andrnits environment. It is a mechanico-electrochemical phenomenon that involves bothrnmechanical and electrochemical processes and their interaction. Whether a crack willrnpropagate depends on local conditions, I.e. those experienced by the material at the tip of arnSCC crack. Hence, it is imperative that the mechanical and electrochemical loading at therncrack-tip are evaluated. However, in order for measured, laboratory crack growth ratesrn(CGRs) - obtained on specimens - to be extrapolated to predict component CGRs, a unifiedrnapproach to calculate the crack-tip conditions is essential. In the underlying paper, finiternelement calculations of the electrochemistry in a crack are coupled to analytical mechanicalrncalculations. The assumed mechanism for crack propagation is the slip-dissolution model.rnHence, the mechanical loading is the crack-tip strain rate and the electrochemical loading isrnthe electrode potential at the crack-tip. Two systems have been investigated: 304 stainlessrnsteel in dilute sulphuric acid solutions and 316 stainless steel in boric acid - lithium hydroxidernsolutions. Both material-environment combinations are relevant to SCC in light waterrnreactors. The model uses material and environmental parameters that can, to a great extent,rnbe obtained independently of measured CGRs.