Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 101-104). Also available via the Internet.

Thesis (M.S.) University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (May 20, 2007) Vita. Includes bibliographical references.

Thesis (Ph.D)--Mechanical Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Salant, Richard F.; Committee Member: Bair, Scott; Committee Member: Cowan, Richard S; Committee Member: Danyluk, Steven; Committee Member: Scott, Waymond R. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Thesis (Ph. D.)--University of Texas at Austin, 2005. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--Mechanical Engineering, Georgia Institute of Technology, 2007. / Dr. Liang, Steven Y., Committee Chair ; Dr. Melkote, Shreyes N., Committee Member ; Dr. Vengazhiyil, Roshan Joseph, Committee Member ; Dr. Zhou, Chen, Committee Member ; Dr. Zhou, Min, Committee Member.

Oil ring seals are one major source of instability in high pressure centrifugal compressors. This thesis presents a method for analysis of an improved seal concept that has been used in very high pressure designs (900 PSI). The improved design uses a combination of ring seals and tilting pad bearing elements. The stable tilting pad is used to center the heavily grooved seal element. The eight stiffness and damping coefficients which represent the hydrodynamic forces between the journal and the seal assembly are computed by an automated computer code for evaluation of both the standard ring seal and the tilting pad elements. Both synchronous and nonsynchronous steady state characteristics have been included in the analysis. The nonsynchronous whirl of the rotor and its effects on the stiffness and damping coefficients of a 5 tilting pad seal have been given in the form of design curves. The effect of pad inertia which has been neglected in many bearing analysis codes has been incorporated in this seal analysis, and allowed the determination of the exact cross coupling stiffness and damping coefficients. / Master of Science

Tests were conducted in the Lubrication Laboratory of the Virginia Polytechnic Institute to study the effect of several metals on the deterioration of steam-turbine oils. A special test apparatus was constructed and three commercial turbine oils were tested in the presence of 14 different metal and metal combination. Included in this group of metals were five bearing metals, several metals now extensively used in turbine lubricating systems, and several metals that are not at present used in turbine oiling systems. Oxidation of the oils was accomplished by heating the oil in glass containers at 275°F for 200 hours, in the presence of the metals. The oil samples were then subjected to laboratory inspections to determine the extent of oxidation. It was found that in the case of oil A copper, lead and the copper-lead combination were increasingly effective in increasing the viscosity and acidity. Brass, copper, and copper-lead were increasingly effective in promoting sludge formation. With oil B copper, lead, and the copper-lead combination were increasingly effective in promoting sludge formation and increasing the viscosity. Steel, lead and the copper-lead combination were increasingly effective in producing acidity. Copper, metal No. 9, and the copper-lead combination were increasingly effective in increasing the viscosity of oil C. Copper, metal Ho. 5, and copper-lead produced acidity in increasing amounts. Aluminum, zinc, and cooper were increasingly effective in promoting sludge formation. Tin showed the least effect on solidity in the case of all three oil. It caused the lowest sludge formation with oils A and B and was low with oil C. The viscosity of oil A was least affected by metal No. 6, of oil B by metal No. 8, end of oil C by steel. / Master of Science

An experimental study of ceramic lubrication through the concept of tribopolymerization from the vapor phase is presented. Four vinyl monomer additives were studied, i.e., vinyl acetate, diallyl phthalate, lauryl methacrylate, and vinyl octadecyl ether. The liquid additives were heated, vaporized, and delivered to an enclosed alumina-on-alumina "pin-on-disk” contact region by a stream of dry nitrogen gas. Alumina ball wear reductions of up to 99% were observed and total wear reductions (ball and disk) of over 70% were also common. Colorful surface films visible to the naked eye were examined. Monomer concentration does not appear to have an effect over the range examined. But, higher monomer delivery temperatures have a significant beneficial effect in reducing wear. Selective FTIRM analysis shows evidence of both polymerization and monomer reactions with the alumina surface. It is believed that the surface films formed reduce adhesion and therefore decrease both wear and friction. The development, design, and construction of a high load, high speed, high frictional heat generation pin-on-disk machine is presented. A very successful geometry has been created and recommendations for added instrumentation and its future use for both liquid and vapor phase tests are presented. / Master of Science

Electromagnetic launchers are currently being developed for their use as military weapons. These devices launch a projectile to extremely high speeds using very large electric currents. One obstacle facing the development of electromagnetic launchers is damage to the rails and armature during launch. The damage occurs due to current arcing in the armature-rail interface and is denoted as a transition. One solution is to use a lubricant injection system contained inside the armature to provide a conductive lubricant to the interface. The lubricant will ensure good electrical contact, prevent solid-solid contact, and cool the interface to prevent a launch from transitioning. Various different armature designs are currently under development. Each design must be analyzed through armature-rail interface modeling in order to predict the physical behavior and identify causes of transitions. There have been many studies on the physical behavior of sliding contacts. Some of which are directly applied to electromagnetic launch. In particular the magneto-elastothermohydrodynamic model is the most comprehensive model found for use in simulating electromagnetic launch. It includes calculation of the electromagnetic field, elastic deformation of the armature, calculation of the armature temperature history, and a hydrodynamic study of the lubricant both in the injection system and the armature-rail interface. The magneto-elastothermohydrodynamic model has been applied to only one armature design with limited success due to the assumptions used. The magneto-elastothermohydrodynamic model is applied to six different armature designs each requiring modifications to be made in order to predict the distinct behavior of each launcher. Modifications to the model include consideration of turbulent flow in the injection conduit, unique injection configurations, dry-out of the armature-rail interface, two dimensional pressure fields, and analyses of cylindrical bore launcher designs. The results show the model is effective in predicting when a transition will occur and what physical event leads to a transition when compared to experimental launch data. Additionally, experimental observations are used to affirm the simulation of other physical characteristics. It is found by the simulation that the base case armature is successful in preventing a transition of the shot, which is consistent with the experimental results. The simulation of NRL shot 223 reveals that such a small amount of lubricant is supplied by the reservoirs that the armature-rail interface partially dries out making a transition likely at a time of 4.7 ms; agreeing with the experimentally observed transition at a time of 4.5 ms. It is determined that the transition of NRL shot 406 is not due to a lack of lubricant inside the interface and that the amount of lubricant which leaks from the joint is negligible. IAP shot 7 did not transition in the experiment, however, after a time of about 3.5 ms the muzzle voltage began to rise. The simulation presents a possible explanation, showing that the armature-rail interface is beginning to empty out after 4.2 ms. The simulation of the GTL-2-4C armature shows that the experimentally observed transition is caused by the reservoirs emptying out at about 2.1 ms. The exploratory simulation of a modified GTL-2-4C armature determines that the absence of the slit in the armature trailing edges will not prevent the transition nor extend the successful portion of the shot.

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