No description available.

To design and test hip joint prosthesis it is essential to know the magnitude and character of forces that may be applied to them in-vivo. For this thesis the hip joint forces of 40 to 60 year old subjects (five male and six female normal subjects and five male hip replacement) were studied. To allow the calculation of hip joint forces data from three-dimensional motion analysis and force plates were applied to a model of the lower limb. The model included the hip, knee and talocrural joints with 3 hip, 8 knee and 8 ankle joint forces, 4 knee ligaments and 47 muscle elements. A double linear optimisation technique (first minimising the maximum muscle stress then minimising the sum of the forces in the force bearing structures) was applied to solve the redundancy problem of force distribution in the muscles. Walking and stair, ramp and camber negotiation were characterised. Ground reaction forces, joint angles, intersegmental forces and moments, joint and ligament forces and muscle forces are presented. Muscle forces predictions were in general agreement with those in the literature, although the model was not capable of correctly distributing forces in the vasti or in the ankle only muscles as patella and talocalcaneonavicular joint equilibria were not included. In general, hip replacement subjects demonstrated lower hip joint forces than normal subjects. The range of maximum resultant hip joint forces for all activities was 3.04 to 11.85 for male normal subjects, 4.18 to 11.50 for female normal subjects, 3.73 to 6.81 and 2.21 to 8.77 for male hip replacement subjects for their natural and replaced sides respectively. The results presented define in three dimensions the hip joint forces in both pelvic and femoral axes systems and thus characterise the probable in-vivo requirements of hip joint prostheses during performance of the activities studied.

M.Tech.

No description available.

The burden of osteoarthritis continuous to increase. While joint replacement surgery provides a cost effective and efficacious treatment for end stage osteoarthritis, no treatment exists to prevent or slow the progression of the disease. Understanding the cellular and molecular changes in the synovium following trauma and in early osteoarthritis could facilitate the identification of novel therapeutic targets. Previous studies identified synovial hyperplasia following intra-articular fractures, cartilage injury and in osteoarthritis. In mice, proliferation of synovial mesenchymal stromal/stem cells (MSCs) leads to synovial hyperplasia following joint surface injury. The driver for this expansion of MSCs in the synovium is unknown. Recently, YAP, a key downstream effector of the Hippo pathway, has been shown to causes tissue overgrowth due to modulation of MSC proliferation. The joint surface injury model of osteoarthritis was used to investigate whether YAP may play a role in synovial hyperplasia following joint surface injury. This work shows that synovial hyperplasia is common to both healer and non-healer mouse strains after joint injury and that Yap expression is up regulated on a protein and mRNA level. Using the same injury model in a mouse with a conditional knockout of Yap in Gdf5 lineage cells, showed that a Yap knockout in Gdf5 progeny cells prevented hyperplasia of synovial lining after joint surface injury, suggesting that YAP is required for MSCs in the synovium to proliferate. In patient synovial samples, YAP expression was up regulated in activated synovium, including a subset of CD55 positive fibroblast-like synoviocytes in the synovial lining. Proliferating cells were positive for active YAP. This suggests that findings in our mouse model are clinically relevant. Furthermore, modulation of YAP and synovial MSC proliferation after JSI provides a means to study the role of synovial hyperplasia after trauma. This could lead to a potential novel therapeutic target for the treatment of posttraumatic osteoarthritis.

Capacitor discharge welding (CDW) is a rapid solidification joining process under the influence of one-dimensional thermal gradients. Although CDW is useful for joining small parts and dissimilar metals, CD welded joints have a large variability in weld strength. CDW is not widely accepted because of a lack of automated process control. Studying the sources of variability in the CDW process can guide the automation of CDW. Therefore, the objectives of this study were to investigate sources of variability that affect weld strength and to generate a model to predict the weld strength variability in CDW. The source of variability was investigated by using screening experiments. Four different materials, stainless steel, Nitronic 50 Steel, copper, and low oxygen copper (C101), were selected to represent various levels of thermal conductivity and absorbed gas content. Thermal conductivity, percentage of gas content absorbed, diameter, and welding time were treated as the independent variables while the dependent variables were the standard deviation of CD weld strength as a percentage of base material strength and the mean of CD weld strength as a percentage of base material strength. A screening experiment and a statistical analysis of the data were used to develop a predictive model of the weld strength variability in CDW. Electron photomicrographs of weld fracture surfaces and dynamic current and resistance curves for each welding cycle were used to support conclusions from the statistical analysis. Conclusions of this study are that thermal conductivity and absorbed gas content do have a significant influence on weld strength variability in CDW. / Graduation date: 1999

Thesis (M.S.)--Oregon State University, 1981. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Thesis (M.S.)--Oregon State University, 1982. / Typescript (photocopy). Includes bibliographical references (leaves 76-79). Also available on the World Wide Web.

Impact force and deformation behavior of adhesively bonded single lap composite joints for transverse impact are studied through a pilot project and validated using Finite Element Analysis (FEA). At present there is no standard which provides guidelines in testing adhesively bonded joints or structures at coupon level. An attempt is made here to formulate the testing procedure through an experiment. Adhesively bonded glass-epoxy lap joints are transversely impacted using three different hemispherical impactors at three different energy levels. The effect of impactor diameter on impact force, target deformation and energy absorption are of particular interest. An explicit non-linear contact analysis using LS-Dyna-3D is carried out. FEA results are observed to be in close agreement with the experimental results. The results show that for a same impact energy level larger impactor generates more force whereas smallest diameter produces highest deformation and most through thickness damage. The same finite element model is used to investigate the effect of lay-up schedules and number of plies on impact force and deformation in composite lap joint. The study of various lay-up schedules reveals that fibers in [0/90] direction have better control on target deformation than fibers in [45/-45] direction for the given boundary condition in transverse impact. Also as the numbers of plies are increased the system becomes stiffer resulting in high impact force. The target deformation is observed to become more localized with increase in laminate thickness. / Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering / "May 2006." / Includes bibliographic references (leaves 62-64).