Fatigue damage accumulation: the role of corrosion on the early stages of crack development

It is now recognised that a complex load history may lead to structural damage that cannot be predicted on the basis of simple uniaxial loading conditions. The application of a single overload can induce sufficient crack growth such that the fatigue limit of a material is compromised. In a similar manner, it is possible to transgress the fatigue limit of a material by applying a number of corrosion cycles which lead to an increase in the size of the defect(s) present in the material beyond that of a 'threshold condition'. Damage accumulation within materials arises owing to the load and environmental history experienced throughout the lifetime of a component or structure. Furthermore, damage owing to load or environment in isolation impacts less on the durability of a structure/component, compared with that when conjoint effects of load and environment are experienced. This paper discusses the contribution that arises from environmental processes, such as corrosion, to final material failure. Synergy owing to corrosion and static/cyclic stress are discussed for both passive (stainless steel) and active (carbon steel) materials.