Corrosion fatigue mechanical variables

Corrosion fatigue depends strongly on the combined interactions of the mechanical (loading), metallurgical, and environmental variables.31... 

From studies of service behavior and from extensive laboratory investigations, the well-established terms stress-corrosion cracking (SCC) and corrosion fatigue have been shown to relate to a continuum of failure modes classified as environment-sensitive fracture. In many environments, the addition of stress, with associated strains, introduces a variable that can result in brittle failure in the sense of very limited plastic flow in otherwise ductile materials such as the stainless steels. Environment-sensitive fractures propagate at an advancing crack tip at which, simultaneously, the local stresses can influence the corrosion processes, and the corrosion can influence the crack-opening processes. Since these processes proceed by kinetic mechanisms, they are time and stress dependent with the result that the crack propagation rate can become very sensitive to the stress application rates. Conventional SCC usually has been associated with static stress, but this is seldom realized... 

The time to failure observed in corrosion fatigue testing with non-precracked specimens not only depends on the applied mechanical load and the corrosivity of the environment but also on other variables such as ... 

Corrosion fatigue is related to, but uniquely distinct from, SCC [71], Purely time-dependent CF crack propagation in SCC-prone alloys is governed by the integrated amount of time-based crack extension per fatigue load cycle. In such cases CF and SCC occur by the same mechanism and are affected by the same variables, as modeled by simple linear superposition [49,52,53], SCC is discussed elsewhere in this manual. 

The variables affecting corrosion fatigue may be classified into three categories (a) mechanical... 

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