applied fracture mechanics

Chapter 8Early Corrosion Fatigue Damage on StainlessSteels Exposed to Tropical Seawater:A Contribution from SensitiveElectrochemical TechniquesNarciso Acuña-González, Jorge A. González-Sánchez,Luis R. Dzib-Pérez and Aarón Rivas-MenchiAdditional information is available at the end of the chapterhttp://dx.doi.org/10.5772/526981. IntroductionA major concern in the design of engineering structures is the ability of components tomaintain their integrity during their entire life service even when subjected to a combinationof fluctuating loads and aggressive environments. The requirement for reliable structuralintegrity is particularly important for structures, involved in fundamental fields such astransportation, oil and gas production and energy generation. Fatigue and corrosion fatiguefailures take place in components and structures as result of complex loading histories.There are different stages of fatigue damage in engineering components where defects maynucleate on initially smooth or undamaged sections, followed by microstructural crackformation, stable propagation and finally unstable crack propagation where catastrophicfailure occurs.Total fatigue life is often considered as a process of fourth major stages [1,2]:a. Initiation or nucleation of fatigue cracks: substructural and microstructural which causenucleation or permanent damage,b. Small-Crack growth: the creation and growth of microscopic cracks,c. Macro-Crack propagation: the growth and coalescence of microscopic flaws to form“dominant cracks” and stable propagation of dominant macrocracksd. Final fracture: structural instability or complete fracture.Then, fatigue life of engineering components and structures can be dened as the periodduring which cracks initiate from defects and propagate. The largest fraction of fatigue life© 2012 Acuña-González et al., licensee InTech. This is an open access chapter distributed under the termsof the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permitsunrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.