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Type of Document	Dissertation
Author	Nguyen, Olivier T.
Author's Email Address	olivier_thanh_nguyen AT yahoo.com
URN	etd-12032004-161201
Persistent URL	http://resolver.caltech.edu/CaltechETD:etd-12032004-161201
Title	Cohesive models of fatigue crack growth and stress-corrosion cracking
Degree	PhD
Option	Aeronautics
Advisory Committee	Advisor Name Title Michael Ortiz Committee Chair
Keywords	None
Date of Defense	2000-07-09
Availability	unrestricted
Abstract The aim of this dissertation was to develop models of fatigue crack growth and stress-corrosion cracking by investigating cohesive theories of fracture. These models were integrated in a finite-element framework embedding a contact algorithm and techniques of remeshing and adaptive meshing. For the fatigue model, we developed a phenomenological cohesive law which exhibits unloading-reloading hysteresis. This model qualitatively predicts fatigue crack growth rates in metals under constant amplitude regime for short and long cracks, as well as growth retardation due to overload. Quantitative predictions were obtained in the case of long cracks. We developed a chemistry-dependent cohesive law which serves as a basis for the stress-corrosion cracking model. In order to determine this cohesive law, two approaches, based on energy relaxation and the renormalization group, were used for coarse-graining interplanar potentials. We analyzed the cohesive behavior of a large--but finite--number of interatomic planes and found that the macroscopic cohesive law adopts a universal asymptotic form. The resulting stress-corrosion crack growth rates agreed well with those observed experimentally in 'static' fatigue tests given in the literature.
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