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This thesis describes the advances made by the author on the direct modelling of the fatigue growth of planar cracks A versatile step-by-step 3D finite element technique has been developed, which calculates the stress intensity factors at a set of points on the crack front according to linear elastic fracture mechanics principles and then applies a fatigue crack growth la\v to this set of points to obtain a new crack profile The software DUCK developed has a good capability of automatic remeshing so that the fatigue propagation of arbitrary shaped cracks can be conveniently followed The stress intensity factor calculation using the 3D finite element method has been improved and widely verified to be of good accuracy generally, which provides an important guarantee for the fatigue growth prediction. Several major problems associated with the stress intensity factor calculation, such as crack front definition, free surface layer and mesh abutting the crack front, as well as J-integral path independence, have been discussed A variety of cracked geometries of either theoretical or practical significance have been modelled by the numerical technique, including internal defects in infinite solids, surface cracks in finite thickness plates, round bars and pressure vessels, and initially multiple surface small cracks. Many results useful for the fatigue assessment of each kind of crack, such as stress intensity factor variations, fatigue shape changes and fatigue lives, have been obtained. By comparing with existing numerical methods and some limited experimental data found in the literature, it is shown that the numerical simulation technique is reliable and can predict the fatigue propagation of complex crack configurations, which is seldom possible for methods with assuming crack front configurations Meanwhile, due to the highly automated procedure or the technique, it has become straightforward to model the fatigue growth of practical cracked components, as demonstrated by the computations in this thesis. It is believed that such a numerical simulation technique has a great potential and will play an useful role in the area of fatigue study and assessment.

acase@tulane.edu / Women’s reproductive health is a severely understudied field and is associated with an abundance of clinically significant pathologies such as pelvic organ prolapse (POP) and preterm birth (PTB). While the exact etiologies of these disorders are unknown, onset is understood to be predominately due to failure of the muscles and connective tissues of the pelvic floor. These failures are attributed to the suboptimal remodeling and maladaptive constituent turnover of the soft tissue extracellular matrix (ECM) including elastic fibers, collagen fibers, glycosaminoglycans / proteoglycans (GAGs/PGs), and smooth muscle cells. Both the vagina and the uterosacral ligament (USL) act as supportive structures that maintain the healthy state of the pelvic floor. Disruption of the elastic fiber and GAG metabolism within the extracellular matrix of these tissues has been suggested to result in the mechanical failure associated with pelvic floor disorders, however, the relationship between microstructure and mechanics is relatively unknown. Histological analysis paired with the biaxial testing of these pelvic floor supporting structures is an important step in providing additional insight into the specific structure-function mechanisms of these tissues. Therefore, the overall objective of this study is to establish a basic understanding of the structure and function of the extracellular matrix constituents within vital soft tissue (vagina, USL) of the murine and human pelvic floor. To elucidate the role of specific constituents, vaginal tissue from female mice in estrus were tested using an extension-inflation biaxial testing protocol pre and post digestion of both elastin and hyaluronan, the most abundant GAG in the extracellular matrix. The digestion of elastin (supported by histological area fraction analysis) resulted in a decreased compliance and an increased dilation of the vaginal wall. Results from the digestion of hyaluronan were inconclusive, as the mechanical response varied with treatment time. Finally, human uterosacral ligaments of postmenopausal, prolapsed patients were tested on a custom built planar biaxial device. This study revealed an inverse relationship between the mechanical stiffness parameters and the ratio of elastin to collagen within the USL. The present findings provide useful information to help understand the etiology behind POP, and help in the development of computational models for the prediction and assessment of observed microstructural changes associated with soft tissue failure. / 1 / Daniel Capone

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Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 110-116). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.)-University of California, December 1963. / TID-4500 (24th Ed.). Part II. Bibliography references : p. 31-32.

Thesis (Ph.D.)--University of Iowa, 2009. / Includes separate files for thesis supplements. Thesis supervisor: David E. Stewart. Includes bibliographical references (leaves 107-109).

Thesis--M. Phil., University of Hong Kong, 1985.

Mode of access: World Wide Web. / Thesis (Ph. D.)--University of Hawaii at Manoa, 2005. / Includes bibliographical references (leaves 94-111). / Electronic reproduction. / Also available by subscription via World Wide Web / xv, 111 leaves, bound ill. (some col.) 29 cm

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