Synergism between fatigue and cyclic‐stress corrosion cracking: Electrochemically active surface area

Abstract After over 50 years of research on the topic, researchers continue to consider how time‐dependent environmental effects can be integrated with cycle‐dependent fatigue crack growth rate (CGR) models. Early corrosion‐fatigue (CF) model assumptions were that cycle‐dependent CF and time‐dependent stress corrosion cracking (SCC) contributions are separable, operate in parallel, are non‐interacting. However, research has shown that CF and SCC may interact synergistically to produce CGRs greater than that obtained by simple summation. Proposed here is that CF and SCC mechanisms may interact synergistically as each is dependent on the electrochemically active surface area (E‐ASA) at a crack tip. A phenomenological model is developed for the effects of crack tip strain rate, film‐rupture, and repassivation rates on E‐ASA. Analysis of hold‐time CGR data provides a method of separating cyclic‐ and static‐load hold‐time effects on E‐ASA. Five model parameters, each having physical interpretation, are found to have reasonable magnitudes.