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This thesis presents a novel device for measuring the viscoelastic properties of biological tissue. The ability to measure the mechanical properties of tissue is of special interest for many medical applications; ranging from disease diagnostics to surgical operations and simulations. In practice, physicians use a technique called palpation to detect the presence of viscoelastic property changes which are associated with the healthiness of tissue. Palpation relies exclusively on the expertise and experience of the physician and is only effective if the difference in tissue stiffness is profound. Current technologies for the measurement of tissue healthiness, including ultrasound, have been shown to be incapable of detecting isoechoic lesions even though they were significantly stiffer than surrounding tissue. The new device presents a reliable, accurate and quantitative method for determining the mechanical properties of soft tissue. Consequently, the healthiness of the tissue or the presence of lesions can be found.

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Thesis (Ph. D.)--Lehigh University, 1999. / Includes vita. Includes bibliographical references (leaves 214-219).

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1991. / Vita. Abstract. Includes bibliographical references (leaves 302-308). Also available via the Internet

Thesis (MS)--Montana State University--Bozeman, 2009. / Typescript. Chairperson, Graduate Committee: David A. Miller. Includes bibliographical references (leaves 114-117).

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Experiments have shown that the addition of small amounts of long-chained polymer additives to a Newtonian fluid produces desirable lubricants. Additives added to oil make the fluid viscoelastic. The effect of viscoelasticity on lubrication characteristics has recently taken on added significance with the move to yet lower-viscosity lubricants for improved energy efficiency. Any factor influencing load-bearing capacity and wear is clearly of renewed importance. The general trend towards the usage of high performance lubricants and environmentally friendly products also support the design of new lubricants. This thesis is aimed at investigating viscoelastic flows within eccentric rotating cylinders (practical application - journal bearings) using a commercial finite element software POLYFLOW. Numerous validations are performed and excellent agreements are achieved. Steady shear and small-amplitude oscillatory shear (SAOS) experiments are performed for specific lubricants including mineral-based and bio-based lubricants to characterize their rheological behavior. Experimental data are fitted by a viscoelastic constitutive model used for numerical simulations. The effects of fluid viscoelasticity between eccentric rotating cylinders on the flow field and on the lubrication performances are revealed in 2D and 3D respectively. From 2D investigation, an increased load capacity on the inner cylinder is found to be achieved by increasing the viscoelasticity of flow. For the first time, to our knowledge, 3D results for an UCM (Upper-Convected Maxwell) fluid at steady state are presented and the flow patterns along the axial direction within the eccentric rotating cylinders are investigated. The viscoelastic effects of those lubricants on the journal bearing performances are revealed and compared at various temperatures. The modeling and numerical simulations used to predict the flow of lubricant in a journal bearing can generate important economic benefits. This research will lead to advanced predictive tools that can be used to improve the design of journal bearing and to propose new economically viable and environmentally friendly lubricants. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

<p>Models of human musculoskeletal tissue are the missing component needed to make significant advances in clinical orthopedics. Developing these models requires an in-depth knowledge of techniques and procedures which are rarely considered or taught in universities.  Essential skills like deriving the foundational physics and the constitutive theory from first principles are the building blocks which will deliver future models or ligaments, tendons, and muscles. This thesis presents the first step in a journey to understand these modeling techniques in order to move toward developing a model of human tissue. The material utilized in the experiments</p> <p>was recipe of Ecoflex 00-20 which represents an idealized example of a large deformation viscoelastic solid. The Finite Strain Viscoelastic constitutive law was derived from first principles, uni-axial tension experiments provided the raw data, and the constitutive laws were fit to the data. The derived model outperformed most of the models with some exceptions described in the results. These results justify the development of more complicated models and experiments such as modeling surface field data and considering more complicated material properties.</p>

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