Tesi di Dottorato

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Author: search.filters.author.Bruno,LuigiHas files: Yes

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    Biomechanics of the human eye slera
    (2014-02-14) Fazio,Massimo Antonio; Bruno,Luigi; Rizzuti,Sergio
    The biomechanics of the optic nerve head and peripapillary sclera have been hypothesized to play a central role in the individual susceptibility to glaucoma, which is the second leading cause of blindness worldwide. The aim of this work is to provide a mechanical testing and experimental data analysis procedure to characterize mechanical properties of human sclera. The overall goal of performing scleral tissue mechanical testing is to elucidate the role of ocular biomechanics in the development of this disease by constructing eye-specific finite element models of the posterior pole. In this work it has been developed and validated a new methodology for computing sub-micrometer scale IOP-induced deformation obtained during pressurization testing of human scleral shells. Genetic Algorithm-based procedure and a microstructure-based numerical fitting method have been adopted to assess structural material properties of the testes eyes. Preliminaries results show the range of nonlinear, anisotropic mechanical properties of posterior sclera from normal eyes of human donors.
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    Caratterizzazione elasto-plastica mediante prove di trazione e interferometria speckle
    (2014-01-23) Bova,Marco; Poggialini,Andrea; Bruno,Luigi; Olivito,Renato Sante
    In the present work of thesis an experimental equipment for elasto-plastic characterization of engineering materials by tensile tests is presented. The stress state is imposed to the specimen by a testing machine fixed on the optical table and designed for optimizing the performance of a speckle interferometer. All three displacement components are measured by a portable speckle interferometer fed by three laser diodes of 50 mW, by which the deformations of small surfaces can be fully analyzed in details. The whole equipment is driven by control electronics designed and realized on purpose, by which it is possible to accurately modify the intensity of the illumination sources, the position of a PZT actuator necessary for applying phaseshifting procedure, and the overall displacement applied to the specimen. The experiments were carried out by a virtual instrument implemented in National Instrument LabVIEW environment, while the processing of the experimental data in Wolfram Mathematica environment. The thesis first reports some preliminary results obtained by a specimen subjected to 3D rigid body motions; the results showed a high accuracy and repeatability of the interferometer. Then, the whole experimental apparatus was employed for the elasto-plastic characterization of a high strength steel specimen. The σ-ε curve for the material was determined and the experimental data were approximated using Ramberg-Osgood and Hollomon’s constitutive models.