Master of Science

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The analysis of ring type seals is of great concern for the designer of high speed and high pressure centrifugal compressors. Computers now play a major role in allowing for a quick evaluation of the floating ring seal. Since the accuracy of the rotor shaft stability evaluation depends on the validity of the dynamic seal characteristics, every step in the evaluation must be carefully scrutinized and updated to include the latest in theory and practical operating experience. This thesis presents the theory and results of one such extension to the current published analysis of oil ring seals. The new analysis includes the influence of the sealing fluid temperature gradients on the leakage flow rate and seal dynamic characteristics for multi-ring and/or multi-land ring configurations. Using classical short bearing theory but allowing for temperature and pressure dependent viscosity variations across the seal, the resulting pressure profiles have been determined numerically utilizing a finite difference solution technique. This thesis discusses the method used to calculate the flow and pressure profiles for oil seals, their influence on the seal dynamic characteristics, and the importance of their consideration on actual turbomachinery stability. / Master of Science

This study developed, explored, and refined techniques for the in vitro study of cartilage-on-cartilage friction, deformation, and wear. Preliminary results of in vitro cartilage-on- cartilage experiments with emphasis on wear and biochemistry are presented. Cartilage-bone specimens were obtained from the stifle joints of steers from a separate controlled study. The load, sliding speed, and traverse of the lower specimens were held constant as lubricant and test length were varied. Lubricants tested consisted of a phosphate buffered saline solution, bovine serum, and bovine synovial fluid. Synovial fluid as a lubricant produced the least amount of damage to the cartilage. Serum produced more wear and damage than synovial fluid, but less than buffered saline (which produced the most damage). Three-hour tests produced more wear than one-hour tests, with severe damage to the lower plug in several of the three-hour tests. Analysis of the results was possible through: data acquisition of normal load, tangential load, and LVDT displacement; photomacrographs; ESEM and SEM surface studies; stained cross-sectional slides of cartilage; and hydroxyproline analysis of cartilage wear. Detailed procedures and discussion of results are presented along with recommended changes for future biotribology research. / Master of Science

Introduction: At the present time there are, on the market, numerous lubricating aids which are designed to improve the lubricating qualities of the various mineral lubricating oils, especially those intended for automotive use. The manufacturers of some of these make statements concerning them that to any fair-minded individual are startling. With this in mind, it has been the purpose of the author to try to verity these claims or else disprove them. It would be impossible in the time allowed to test allot these aids; so a representative few were chosen which covered the field quite thoroughly. From the results shown by the use of these aids in an internal combustion engine, as well as those shown by the physical property tests in the laboratory, it seems as though their suitability for industrial use would be demonstrated. In other words, the results should show which of the arguments put forth by the manufacturers of the various products are of sound basis and which are stated merely for the sake of advertising and publicity. / Master of Science

Yes / Fretting wear has a significant influence on wire rope fatigue life when in cyclic bending, particularly for crossed-wire contacts, where the interfacial motion of the surfaces is complex and multi-axial. To simulate these contacts in a controlled manner, a laboratory-scale, crossed-cylinder, reciprocating fretting wear test was developed. A broad range of contemporary lubrication technologies were evaluated using this method and a systematic multivariate statistical analysis was performed to identify the most significant lubrication-related parameters with respect to these fretting wear conditions. Wear area increase per slip cycle was the most relevant measure of wear damage, as this captured the influence of changes in the fretting wear regime during the test. The ability of a lubricant to reduce damaging fretting wear during the run-in phase was the biggest influence on long-term fretting wear, particularly for grease-lubricated contacts.

by Lam Yip-mou Charles. / Thesis (M.B.A.)--Chinese University of Hong Kong, 1981. / Bibliography: leaves 104-106.

Made available in DSpace on 2014-06-11T19:28:21Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-06-15Bitstream added on 2014-06-13T19:57:38Z : No. of bitstreams: 1 silvaneto_jf_me_bauru.pdf: 1785488 bytes, checksum: 20f9f159b1b215b07f4c95af3fa0d932 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / No processo de retificação e utilização de fluidos de corte é uma maneira de implementar a qualidade final ao processo, pois os fluidos têm como finalidade a lubrificação na área de contato entre a peça e ferramenta e a refrigeração das superfícies, assim evitando danificações na superfície da peça. Com isso, a utilização de fluidos de corte tem sido constantemente estudada, visando diminuir a utilização deste, pois a utilização de fluidos de corte tem seus problemas. O custo do produto final aumenta consideravelmente com o uso de fluidos de corte no processo de retificação, além de que os fluidos de corte são substâncias tóxicas e nocivas tanto às pessoas quanto ao meio ambiente. Portanto indústrias, universidades e centro de pesquisas são levados a pesquisar métodos alternativos menos prejudiciais ao meio ambiente. Dentre as alternativas surge e técnica da mínima quantidade de lubrificante (MQL), que também tem suas desvantagens, como por exemplo, a formação de uma borra de óleo na superfície de corte do rebolo, o que gera uma rugosidade maior na peça. Porém, visando minimizar esse problema podem ser usados jatos de ar comprimido incidindo na superfície de corte do rebolo, com o objetivo de limpar a superfície de corte do rebolo, com o objetivo de limpar a superfície do rebolo. Dessa forma, avaliou-se a eficiência desse sistema de ar comprimido para a limpeza e pôde-se verificar que, a utilização da limpeza juntamente com a técnica do MQL, torna-se viável, pois de uma maneira geral a técnica do MQL com limpeza obteve melhores resultados na qualidade da peça e desgaste da ferramenta, em relação ao MQL sem limpeza. A limpeza com um ângulo tangente à superfície do rebolo foi a condição de limpeza que obteve melhores resultados para a limpeza o que comprova que a melhoria na técnica do... / In grinding process the use of cutting fluids is a way to implement the final quality of the process because the fluids are intended for the lubrication in the contact area between the work piece, the tool and the cooling of the surfaces avoiding damages on the work piece surface. However, the use of cutting fluids has been constantly studied in order to reduce its use since this practice brings a lot of problems about. The final product cost increases considerably along with the use of cuting fluids in gringing process, besides those substances are toxic and harmful to people and to the environment as well. Therefore, industries, universities and research center have been taken as sites for investigating less harmfulll alternative methods to the environment. Among such alternatives comes up of minimum quantify of lubricant technique (MQL), which also has some disadvantages, such as the formation of oil sludge on the cut surface of the wheel, which creates a greater surface roughness on the work piece. However, in order to minimize this problem compressed air jets can be used focusing on the cut surface of the wheel, in order to clean it. Thus, we could evaluated the effectiveness of that compressed air system used for cleaning, and it was possible to observe that the use of cleaning with the MQL technique is feasible because from a general view the use of the MQL technique in the cleaning process showed better results in the quality of the work piece and wornout of the tool comparing to the to the MQL with no cleaning. The cleaning with a tangent angle to the surface of the wheel was the condition of cleanliness that showed better results for the cleanliness which proves that the improvements for the MQL techniques does not lead to significant results compared to the conventional technique. However, the MQL technique with cleanliness has its... (Complete abstract click electronic access below)

Friction and wear mitigation is typically accomplished by introducing a shear accommodating layer (e.g., a thin film of liquid) between surfaces in sliding and/or rolling contacts. When the operating conditions are beyond the liquid realm, attention turns to solid coatings. Solid lubricants have been widely used in governmental and industrial applications for mitigation of wear and friction (tribological properties). Conventional examples of solid lubricants are MoS2, WS2, h-BN, and graphite; however, these and some others mostly perform best only for a limited range of operating conditions, e.g. ambient air versus dry nitrogen and room temperature versus high temperatures. Conversely, lubricious oxides have been studied lately as good potential candidates for solid lubricants because they are thermodynamically stable and environmentally robust. Oxide surfaces are generally inert and typically do not form strong adhesive bonds like metals/alloys in tribological contacts. Typical of these oxides is ZnO. The interest in ZnO is due to its potential for utility in a variety of applications. To this end, nanolaminates of ZnO, Al2O3, ZrO2 thin films have been deposited at varying sequences and thicknesses on silicon substrates and high temperature (M50) bearing steels by atomic layer deposition (ALD). The top lubricious, nanocrystalline ZnO layer was structurally-engineered to achieve low surface energy {0002}-orientated grain that provided low sliding friction coefficients (0.2 to 0.3), wear factors (range of 10-7 to 10-8 mm3/Nm) and good rolling contact fatigue resistance. The Al2O3 was intentionally made amorphous to achieve the {0002} preferred orientation while {101}-orientated tetragonal ZrO2 acted as a high toughness/load bearing layer. It was determined that the ZnO defective structure (oxygen sub-stoichiometric with growth stacking faults) aided in shear accommodation by re-orientating the nanocrystalline grains where they realigned to create new friction-reducing surfaces. Specifically, high resolution transmission electron microscopy (HRTEM) inside the wear surfaces revealed in an increase in both partial dislocation and basal stacking fault densities through intrafilm shear/slip of partial dislocations on the (0002) planes via a dislocation glide mechanism. This shear accommodation mode mitigated friction and prevented brittle fracture classically observed in higher friction microcrystalline and single crystal ZnO that has potential broad implications to other defective nanocrystalline ceramics. Overall, this work has demonstrated that environmentally-robust, lubricious ALD nanolaminates of ZnO/Al2O3/ZrO2 are good candidates for providing low friction and wear interfaces in moving mechanical assembles, such as fully assembled rolling element bearings and microelectromechanical systems (MEMS) that require thin (~10-200 nm), uniform and conformal films.

Inconel 718 has widespread use in critical industries like aerospace, marine, and power generation. However, its challenging machinability, characterized by tool chipping/failure, and poor surface quality, remains a significant concern. Despite numerous efforts to enhance tool performance in machining hard-to-machine materials, the issue of sudden tool failure and chipping persists. This study presents an innovative in-situ tool treatment method, complemented by an optimized recoating strategy, aimed at tackling these challenges. The approach involves the application of a lubricating soft metallic Al-Si alloy coating to the tool’s faces, which can be recoated when needed. During subsequent Inconel machining, the Al-Si layer deposited on the tool melts due to high temperatures. The molten material fills microcracks on the tool surface, preventing their propagation. Moreover, the tool can slide on the beneficial tribo-films Al-Si layer which reduces friction, sticking, seizure, and built-up edge formation, resulting in decreased tool wear and chipping. The newly developed pre-machined recoating method has yielded promising outcomes, reducing cutting force and significantly improving tool lifespan compared to the PVD benchmark and uncoated tools. Additionally, this novel method enhances surface quality and minimizes undesirable microstructural alterations induced by machining. / Thesis / Master of Applied Science (MASc) / Chipping and excessive tool wear pose significant challenges in machining high-strength alloys like Inconel 718, limiting their applicability across various industries. According to research, conventional strategies used to deal with the machining challenges posed by Inconel 718 have not produced the best results. The goal of this research is to overcome the machining issues associated with such a difficult-to-cut material innovatively by depositing soft metallic coatings as a solid lubricant to enhance the machining performance. In this study, a cost-effective novel in-situ deposition technique with recoating capability as an alternative to conventional coatings is presented to achieve this goal. This innovative approach aims to improve tool performance during Inconel 718 machining significantly. This study also provides a thorough insight into the application of solid lubricants in machining, discussing their mechanisms, effectiveness, constraints, and potential to boost productivity and environmental sustainability. Furthermore, comprehensive investigations have been conducted to gain deeper insights into the prevalent wear mechanisms and surface treatments that can lead to improved machining performance for Inconel 718.