After 100 years of research, researchers continue to consider how time-dependent environmental effects can be included in existing 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 (ECSA) at a crack tip.  A phenomenological model is developed for the effects of crack tip strain rate, film-rupture and repassivation rates on ECSA.  Analysis of hold-time CGR data provides a method of separating cyclic- and static-load hold-time effects on ECSA.  Five model parameters, each having physical interpretation, are found to have reasonable magnitudes. 

In order to study the fatigue damage and cycle life of TC4 titanium alloy for aero-engine blades under various load conditions, uniaxial fatigue, multi-stage loading and multiaxial fatigue tests were carried out. The critical plane method combined with von Mises criterion was used to study the fatigue life distribution under various loading paths, and the results were verified by experiments. Based on the nonlinear residual strength model and Poisson stochastic process, the reliability prediction of aero-engine compressor blade under maximum continuous working condition was completed. The results show that the fatigue damage and life distribution of TC4 titanium alloy for aeroengine blade under various conditions can be accurately predicted by the method proposed in this paper and the reliability of the blade can still be maintained above 0.9 after it works for 3000 hours under the maximum continuous working condition.