Thesis (M.S.)--Ohio University, August, 1993. / Title from PDF t.p.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING / Bibliography: leaf 68. / by Clarence Teh-Ching Chang. / M.S.

Thesis (M.S.)--University of Wisconsin--Madison, 1966. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

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

Os desenvolvimentos de novos motores têm resultado no aumento constante dos carregamentos mecânicos e térmicos dos componentes. Além de estarem expostos a condições desfavoráveis ao desgaste, os novos componentes do motor devem garantir desempenho similar, ou muitas vezes superior, aos dos componentes atuais. Para os anéis de pistão, o desempenho é dado pela sua capacidade de vedação e raspagem, que podem ser mensurados em motor pelos resultados de consumo de óleo lubrificante (COL) e fluxo de gases para o cárter (blow-by). Sendo assim, a proposta desse trabalho foi a de avaliar-se a influência do tratamento superficial a laser para endurecimento da pista de desgaste do anel de pistão de segundo canalete, em termos do desempenho de vedação e raspagem. Foram comparados dois protótipos, utilizando como padrão um anel de pistão de produção corrente, comercialmente fornecido a clientes. O efeito do tratamento térmico a laser nos anéis foi avaliado em relação a distorções dimensionais. Após isto, foram realizados testes tribológicos de bancada com o objetivo de conhecer o comportamento do anel depois do tratamento laser. De maneira geral o tratamento superficial por laser na superfície de anéis de pistão mostraram resultados significativos no aspecto aumento de dureza, com alguns deméritos no aspecto dimensional que pode interferir na boa funcionalidade do sistema tribológico anel lubrificante cilindro. / The new engine developments are providing engine mechanical and thermal loads increase on the components. Besides the unfavorable wear conditions, the components should provide similar or improved performance compared with current baselines. For piston rings, the performance is given by the ring capacity of sealing and scrapping. These performances can be measured in a engine by the results of lube oil consumption (LOC) and Blow-by. So, the proposal of this work is to evaluate the influence of laser hardening on the second ring wear and verify the sealing and scrapping performance. It was compared two prototypes, being as parameter the current piston ring supplied to customer. Firstly, it was compared the dimensional of the laser hardening effect. After that, it were tested these prototypes in bench tests in order to know the ring performance after laser hardening. In general terms, the superficial treatment by laser on the piston rings surface have showed significant results in the hardness aspects, with some demerits in the dimensional aspect that can interfere in the good functionality of the tribological system, piston rings lubricant cylinder liner.

Os desenvolvimentos de novos motores têm resultado no aumento constante dos carregamentos mecânicos e térmicos dos componentes. Além de estarem expostos a condições desfavoráveis ao desgaste, os novos componentes do motor devem garantir desempenho similar, ou muitas vezes superior, aos dos componentes atuais. Para os anéis de pistão, o desempenho é dado pela sua capacidade de vedação e raspagem, que podem ser mensurados em motor pelos resultados de consumo de óleo lubrificante (COL) e fluxo de gases para o cárter (blow-by). Sendo assim, a proposta desse trabalho foi a de avaliar-se a influência do tratamento superficial a laser para endurecimento da pista de desgaste do anel de pistão de segundo canalete, em termos do desempenho de vedação e raspagem. Foram comparados dois protótipos, utilizando como padrão um anel de pistão de produção corrente, comercialmente fornecido a clientes. O efeito do tratamento térmico a laser nos anéis foi avaliado em relação a distorções dimensionais. Após isto, foram realizados testes tribológicos de bancada com o objetivo de conhecer o comportamento do anel depois do tratamento laser. De maneira geral o tratamento superficial por laser na superfície de anéis de pistão mostraram resultados significativos no aspecto aumento de dureza, com alguns deméritos no aspecto dimensional que pode interferir na boa funcionalidade do sistema tribológico anel lubrificante cilindro. / The new engine developments are providing engine mechanical and thermal loads increase on the components. Besides the unfavorable wear conditions, the components should provide similar or improved performance compared with current baselines. For piston rings, the performance is given by the ring capacity of sealing and scrapping. These performances can be measured in a engine by the results of lube oil consumption (LOC) and Blow-by. So, the proposal of this work is to evaluate the influence of laser hardening on the second ring wear and verify the sealing and scrapping performance. It was compared two prototypes, being as parameter the current piston ring supplied to customer. Firstly, it was compared the dimensional of the laser hardening effect. After that, it were tested these prototypes in bench tests in order to know the ring performance after laser hardening. In general terms, the superficial treatment by laser on the piston rings surface have showed significant results in the hardness aspects, with some demerits in the dimensional aspect that can interfere in the good functionality of the tribological system, piston rings lubricant cylinder liner.

The objectives of this research are the prediction of the thermodynamic behavior of a multi-stage intercooled reciprocating compressor and its progressive loss of performance due to leakage. A theoretical model is developed to simulate the thermodynamics of the compressor system and the lubricating condition and wear of the piston ring pack for a multi-stage intercooled reciprocating compressor. A first law of thermodynamics approach is used to determine the thermodynamic properties of the gas inside the cylinders, the intercoolers and the inlet and discharge manifold. The compressor valves are modeled as single degree-of-freedom, spring-mass=damper systems. The flows through the valves are calculated based on the steady flow equations for equivalent orifices. The lubricating condition of the piston ring pack are determined on the basis of hydrodynamic lubrication theory. The wear of the piston rings is assumed to occur when the hydrodynamic oil film between the piston ring and cylinder bore breaks down. Based on the theoretical model, a computer program is developed. This program is tested on an Ingersoll-Rand Model 242, two stage aircooled reciprocating air compressor. The comparison of the experimental values of the pressure variations in the first cylinder with the value predicted by the computer program shows a reasonable match. The computer program predicts the pressure, temperature and mass flow rates for each cylinder and the intercooler. Also predicted is the wear rate of each piston ring. The progressive loss in the compressor mass discharge, and hence the loss in its performance, is determined by calculating the leakage losses several times, updating the leakage area each time based on the wear rate of the piston rings. The result shows a drop of about 15 percent in the discharge rate of the Model 242 compressor after 8000 hours of running time. / Master of Science

Automobiles have become an integral part of our daily life as more and more mopeds, motor cycles, cars, trucks, busses and trains are being used for transport. The main parts of an automotive engine are cylinder, piston assembly, connecting rod and crank shaft. The piston assembly consists of Piston, Piston rings and Piston Pin. Piston rings are important parts of a piston assembly. Any non-conformance in any quality characteristic of the piston ring leads to deterioration of engine performance. M/S Goetze (India) Limited a medium scale industry and a sister concern of engineering giant M/S Escorts Limited is manufacturing "GOETZE PISTON RINGS" and is producing about 800 varieties of piston rings ranging from 35.00 mm to 228.5 mm nominal diameter. The management was facing serious problem due to high scrap rate in certain types of their manufactured piston rings. Hence instead of trying to handle all of them at the same time, it seemed reasonable to tackle and find a suitable approach to solve the quality problem by taking the most notorious ring first, so that once the methodology is understood, documented and applied to the quality problem of this ring, the same can also be invoked for other rings to improve upon their quality, and thus reducing the scrap rate. One particular ring of 83.0 mm diameter which is delicate and costly, having an average scrap rate of 36.2% in past three years is selected for the study. No systematic effort was made in the past to identify the quality characteristics and the processes which were responsible for this high scrap rate and thus no immediate measure could be recommended. As a matter of fact at the beginning of the study it was not even clear which quality characteristics were mainly responsible for such high rejection. So in July' 1999 a pareto analysis was done for the first time to identify the culpability of each quality characteristic for the rejection of the ring. From the Pareto analysis it was observed that maximum proportion of rejection was due to nonconformity in axial thickness. The scrap rate due to nonconformity in axial thickness were collected for each month from Jul’ 999 to Jan'2000 which averaged at 8.7%. Since in every month the major malefactor for rejection was the nonconformity of axial thickness it was decided to first try to improve the quality of axial thickness, before trying to tackle other quality issues associated with this particular piston ring under study. Once the most problematic quality characteristic namely the axial thickness was identified, as a first step towards the goal of improving the quality of axial thickness, it was necessary to pay attention and isolate the manufacturing processes or operations affecting the axial thickness and study them in detail. So first, the entire manufacturing process flow diagram of the piston ring was studied. From the process flow diagram it appeared that there are 4 operations affecting axial thickness viz. Rough Grinding ,Medium Grinding, First Lapping and Finish Lapping. So each of these processes was critically observed to assess whether they were under statistical control or not. Studies were conducted at each of these 4 operations by collecting samples using the rational subgroup method and control charts were plotted. From the control charts, it was observed that the Rough Grinding and Medium Grinding operations were in statistical control with acceptable Cp, Cpk values. But First Lapping and Finish Lapping operations were not in statistical control. Thus we finally identified the two critical processes namely the First Lapping and Finish Lapping operations which were not in statistical control but were crucially affecting the quality of axial thickness. Since the First and Finish Lapping operations were identified as the major source of the quality problem, an in-depth study was undertaken to analyze these two processes. A brain storming session was conducted with all concerned personnel from production, maintenance, design, quality assurance and tool room to get all possible causes which might be affecting the axial thickness variation at these two processes. During the brain storming session the team suggested that the First Lapping process can be processed in medium grinding machine (DFS machine) instead of Lapping machine. The reasons behind this were two fold. First since the aim of the First Lapping is just to remove excess material which was deposited during chrome plating, the same operation can be performed in DFS machine. Since the required surface finish on axial surface was any way being aimed at the Finish Lapping operation, a similar precursory First Lapping'operation in a Lapping machine was really felt not necessary. Secondly since the performance of the DFS machine was found to be under control, albeit for the grinding operation, it was hoped that the Lapping operation in the same machine would also exhibit a similar performance. For this purpose a study was conducted on the First Lapping operation with the DFS machine. It was found that the process was well within the control limit with decent Cp and Cpk values. Thus this procedure of performing the First Lapping operation in a DFS machine took care of the first one of the two problematic processes affecting the quality of axial thickness. Next for tackling the problem with the other critical process, viz. the Finish Lapping operation, various causes were suggested by the team for axial thickness variation in the Finish Lapping operation. Based on these causes, an Ishikawa diagram (cause and effect diagram) was prepared. This Ishikawa diagram had thrown light into number of possible deficiencies in Man, Machine, Method and Material which were responsible for axial thickness variation at finish Lapping. The Ishikawa diagram was carefully analyzed. The causes were narrowed down to 6 factors. These are Grinding wheel rotating speed, Grinding Time, Grinding pressure, Holding plate, Holes (fixtures) within the holding plate and Positions within a ring. The 3 factors namely grinding wheel speed, time and pressure were identified as the control factors. Holding plate, Hole position within a plate and Checking position within a ring on the other hand were the noise factors whose different levels might exhibit a variability of axial thickness. Since there were only 3 control factors, it was decided to conduct a full factorial experiment with each control factor at 3 levels. Hence altogether there were 27 experiments at a fixed given combination of speed, time and pressure. There were 4 holding plates with each plate having 6 slotted holes leading to machining 24 rings at a time during the finish lapping operation. Next 3 measurements were taken for each one of these 24 rings. Thus altogether there were 72 observations for one of these experiments. Each experiment was replicated twice by taking measurements for 2 consecutive batches of rings. From the analysis of variance of the results of these experiments for both S/N ratio and mean it was observed that all the three main factors and their interactions were significant. The Normality assumption of standardized residuals for the S/N ratio and mean was validated by normal probability plot and Kolmonogorov-Smirnoff test. The homoscedasticity assumption was validated through Bartlett’s test and residual plots. It was found that the experiment no. 23 (Speed 84 RPM, Time 10 sees and Pressure 300 daN) yielded highest S/N ratio (η) with mean within the specification limit. That the mean and S/N ratio for the experiment no.23 were significantly different from others was established by means of Tukey's multiple comparison test. Next control charts for experiment no. 23 were plotted and was found to be well within control with acceptable Cp and Cpk values. Hence we concluded that the non-conformance in axial thickness can be substantially reduced by using the following optimal setting of factors i.e. grinding speed with 84 RPM, grinding pressure with 300 daN and grinding time with 10 seconds. Using this optimal setting the earlier average rejection rate of 8.7% due to non-conformance in axial thickness was reduced to 0.05%. Under this optimal setting, the process capability index (Cpk) of finish Lapping operation was estimated to be 2.5, which is well above acceptable standard. Due to this reduction in rejection rate in one quality characteristics of one particular ring out of 800 types, the net savings to the organization is approximately Rs. 10,44,000 per year.

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Made available in DSpace on 2016-03-15T19:36:39Z (GMT). No. of bitstreams: 1 Eduardo Nocera.pdf: 12755331 bytes, checksum: 08a19b90827b2e4f2954b2f799e3d18d (MD5) Previous issue date: 2013-09-19 / MAHLE / Piston rings are metal parts which, when installed on the pistons in the cylinders of the engine, become circular with variable pressure and self-expansive, providing a movable seal between the combustion chamber and the crankcase. These components are subjected to intense functional demand, being asked to submit a low wear rate and maintain their structural and functional integrity under high temperatures and pressures. Due to these requirements, the technique is known of providing up-to-face contact with coatings or surface treatments to improve wear. Currently the majority of applications in the compression rings are martensitic stainless steels. These rings have their tribological properties improved by gas nitriding treatment which gives the steel surface intermediate properties between metallic and ceramic materials with high resistance to adhesive wear, as well as to wear by abrasion. This technology has been applied since the 90s with great success and high market penetration. With demand growing for reducing emissions was introduced in the market the Otto cycle engines with bifuel, better known as Flex engines. The principle of operation of these engines is the use of gasoline and ethanol at any mixing. The compression ratio of the piston is optimized for gasoline and not optimized for ethanol, since the latter does not have limitations to the phenomenon of detonation and this fact makes it occurs more Ethanol injection into the combustion chamber providing an improper fuel does not wash burnt in the cylinder wall. The result was the creation of a different tribological system in the area of operation of the rings where the nitrided layer began to suffer a detachment. This study aimed to find a solution for this detachment, where the nitride layer was changed. The modification consisted in decreasing the precipitation of carbides in the grain boundaries through migration carbon more to the core of the ring making it more robust to cracks and less susceptible to hydrogen embrittlement. Was created two nitriding stages, one richer in nitrogen which provides the wear resistance required for applying and the second stage causes the carbon to become more concentrated in the core hindering the generation of cracks and, consequently, the detachment. There was a decrease in the hardness of the nitrided layer without deteriorating the wear resistance, creating a unique solution and extending the life of this technology. / Os Anéis de Pistão são peças de metal que, quando instaladas nos pistões dentro dos cilindros dos motores, tornam-se circulares com pressão variável e auto-expansivas, proporcionando uma vedação móvel entre a câmara de combustão e o carter do motor. Estes componentes são submetidos à intensa demanda funcional, sendo solicitados a apresentarem uma baixa taxa de desgaste e a manterem sua integridade estrutural e funcional sob temperaturas e pressões elevadas. Em função destas exigências, é conhecida a técnica de prover-se a face de contato com o cilindro destes componentes revestimentos ou tratamentos de superfície para melhorar a resistência ao desgaste. Atualmente grande parte das aplicações nos anéis de compressão são em aços inoxidáveis martensíticos. Estes anéis têm suas propriedades tribológicas melhoradas pelo tratamento de nitretação gasosa o qual confere ao aço propriedades superficiais intermediárias entre os materiais metálicos e cerâmicos, com alta resistência ao desgaste adesivo, assim como ao desgaste por abrasão. Esta tecnologia vem sendo aplicada desde os anos 90 com absoluto sucesso e alta penetração de mercado. Com a demanda por redução de emissões crescendo foi introduzido no mercado os motores de ciclo Otto bicombustíveis, mais conhecidos como motores flex. O princípio de funcionamento destes motores é a utilização de gasolina e etanol em qualquer mistura. A taxa de compressão do Pistão é otimizada para gasolina e não otimizada para o Etanol, pois este último não possui limitações para o fenômeno de detonação e este fato faz com que ocorra mais injeção de Etanol na câmara de combustão proporcionando uma indevida lavagem de combustível não queimado na parede do cilindro. A consequência foi a criação de um tribo sistema diferente na região de funcionamento dos Anéis onde a camada nitretada começou a sofrer um destacamento. Este trabalho visou buscar uma solução para este destacamento, onde a camada nitretada foi alterada. A alteração consistiu em diminuir a precipitação de carbonetos nas fronteiras dos grãos através da migração do carbono para o núcleo do anel deixando-o mais robusto à nucleação de trincas e menos susceptível a fragilização por hidrogênio. Foram criados dois estágios de nitretação, sendo o primeiro estágio mais rico em nitrogênio o qual confere ao anel a resistência ao desgaste necessária para a aplicação, e o segundo estágio faz com que o carbono fique mais concentrado no núcleo. O problema de destacamento foi resolvido onde houve uma diminuição na dureza da camada nitretada sem a deterioração da resistência ao desgaste do anel, criando uma solução única e estendendo a vida desta tecnologia sem aumento de custos.