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Thesis (Ph. D.)--University of Wisconsin, 1967. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

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In this thesis, the fatigue response of arteries to four specific physiological conditions representative of various morphological changes that artery undergo during its lifetime, was explored. Single layered nonlinear elastic micromechanical model of artery was developed for this purpose. A comparative study was completed on fatigue response, in the form of available life and shear stress accumulation, between hypertensive and normotensive arteries. The effects of morphological changes of ageing arteries on the fatigue response of the artery were studied. Change in stiffness, arterial dilation and remodeling were taken into consideration. The effect of undulation of the artery, due to weakening of arterial walls with age or hypertension, on fatigue response, is the third aspect of this study. Lastly, the contribution of the surrounding linear elastic tissue material on fatigue response of the artery was investigated to reflect the in-vivo condition of artery where it is always surrounded by different tissues.

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In this dissertation, the fatigue characteristics of three newly developed experimental compositions for aluminum 7175, with improved mechanical strength, that uses magnesium-calcium alloy instead of pure magnesium are studied. Specimens of each variant were fabricated and subjected to fatigue life testing, fatigue life data analysis, and observation of their fracture characteristics through optical microscopy and scanning electron microscopy (SEM), and metallography to study their grains and surface characteristics. Fatigue life testing shows all three variants have a fatigue strength that is approaching approximately 200 MPa. ECO7175v3 is shown to have the highest fatigue strength of approximately 220 MPa at 5x107 cycles, approximately 40% of its tensile strength of 550 MPa. This is shown by its considerably higher fatigue strength coefficient determined by Basquin's equation compared to the other two variants. ECO7175v1 is shown to generally have large scatter in its fatigue life at higher stress levels (65% or higher of their tensile strength) with coefficient of variations typically twice or more to those of ECO7175v2 and ECO7175v3. The results of the SEM analysis shows that irrespective of the stress levels, ECO7175v1 and ECO7175v3 all have crack initiation points at the surface with no inclusions to act as stress concentrators. The lack of inclusions are supported by the reliability analysis which shows the hazard rates for all variants remains relatively constant the majority of the time before increasing towards the end. These trends for all variants indicates failures are due to wear-outs instead of defects, which were not seen. Reliability analysis also shows that at any given fatigue life cycle and stress level, ECO7175v3 has a lower probability of failure when compared to ECO7175v1 and ECO7175v2. On the other hand, at any given fatigue life cycle and stress level, ECO7175v1 is shown to have a higher probability of failure when compared to ECO7175v2 and ECO7175v3.