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<p>The objectives of this investigation were to experimentally and analytically evaluate the  performance of a valve train cam and oscillating roller follower mechanism. Of particular interest  was the effect of operating conditions on the slide-to-roll ratio (SRR) of the roller follower. In order to experimentally measure the SRR at the cam-roller contact, a valve train test rig  (VTTR) was utilized. The VTTR contained a section of a heavy-duty diesel engine valve train that  was instrumented with encoders and Hall effect sensors to measure the camshaft and roller  follower angular velocities as a function of operating parameters.  To corroborate the experimental with analytical results, a numerical model for the cam and  oscillating roller follower was developed. In this modeling approach, the roller angular velocity  was determined via a torque balance between the frictional torque of the pin-roller follower and  cam-roller follower interfaces. The pin-roller friction was obtained by developing a time-dependent hydrodynamic journal bearing model with variable speed and load. Friction maps were  developed for the cam-roller follower interface using a ball-on-disk EHD2 rig to capture the  friction behavior across a range of entraining velocities, contact pressures, and SRRs. Additional  areas of investigation included thermal effects and wear in the pin-roller contact. Overall, good agreement was obtained between the experimental and analytical roller  follower angular velocity, with the normalized RMS errors less than 7%, across all operating  conditions investigated. The analytical investigation determined that thermal effects in the pin-roller contact are insignificant for the typical operating conditions. However, it was shown that the  pin-roller friction torque is critical in causing roller follower slip, as the SRR greatly increases  once the pin-roller friction torque is greater than the cam-roller friction torque. Finally, pin-roller  local wear was demonstrated to have detrimental effects on the SRR of the roller follower once a  critical wear depth was reached. </p>

Coolant application is critically important in grinding, preventing workpiece damage and increasing the quality of manufactured components. However, delivery of grinding fluids is difficult to achieve, due to issues unique to grinding processes such as the air layer that surrounds the wheel. Coherent jets, which maintain their shape over a significant distance, are one of the most effective methods of coolant delivery and a significant amount of research has been devoted to developing them. Results of this work, which has largely focused on contoured nozzles, have been modest. Inspired by laminar fountains and wind tunnel design, the present work focuses on the development of a coherent, laminar jet. The developed jet possesses extreme coherence, and appears to resemble a glass rod with its stability and clarity. Investigations were carried out, comparing the coherence and cooling ability of the developed system to that of a commercially available coherent nozzle. Models for the structure of the air layer and to predict the conditions necessary for a jet to penetrate the air layer were also developed. The developed jet outperformed the commercial system both in terms of coherence and manufacturing productivity. The model was validated with experimental values, and appears to provide excellent agreement to those results. This work details the background, design, and experimentation involved in creating these innovative systems. / Thesis / Master of Applied Science (MASc)

京都大学 / 新制・課程博士 / 博士(工学) / 甲第24605号 / 工博第5111号 / 新制||工||1978(附属図書館) / 京都大学大学院工学研究科機械理工学専攻 / (主査)教授 平山 朋子, 教授 松原 厚, 教授 小森 雅晴 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

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A common approach in numerical studies of elastohydrodynamic lubrication (EHL) is based on solving the Reynolds equation that governs pressure distribution in thin lubricant films. The Reynolds equation is derived from the Navier-Stokes equations by taking assumptions that are considered valid when the thickness of the lubricant film is much smaller than its length. A massive increase in the computing power over the last decades has enabled the use of CFD (computational fluid dynamics) approach, based on the Navier-Stokes equations, in solving the EHL problem. Comparisons between the CFD and Reynolds approach have generally shown very good agreement. Differences can occur when the thin film assumptions of the Reynolds equation are not applicable. In this study, a CFD approach has been chosen with the aim of investigating effects of asperities and rheology at high loads on the behavior of the thin EHL films. A high quality mesh was generated in ANSYS ICEM CFD, while ANSYS Fluent has been employed in solving the Navier-Stokes equation by finite volume method (FVM). For EHL modeling, a set of user-defined functions (UDFs) were used for computing density, viscosity, wall temperature, heat source and elastic deformation of one of the contacting surfaces. Two lubricants were used, a commonly used oil in CFD analyses of EHL and Squalane. Non-Newtonian fluid behavior and thermal effects were considered. For Squalane, the two rheology models, Ree-Eyring and Carreau were compared. Squalane has been chosen in this study since it is one of the rare fluids with known parameters for both rheology models. Finally, the influence of surface roughness was explored for the cases of a single asperity and a completely rough wall. A surface roughness profile is generated in MATLAB by using the Pearson distribution function. In the cases where the surfaces are assumed to be completely smooth, the obtained results at the pressure of about 0.5 GPa closely correspond to literature, both in the case of Newtonian and non-Newtonian fluid behavior. At the pressure of about 1 GPa, severe shearing of the lubricant film has been noticed, characterized by a pronounced shear-band and plug flow. It was found that the choice of viscosity and rheology models has a large influence on the obtained results, especially at the high pressure levels. Finally, it was discovered that the developed CFD model of EHL has a great potential in studying the effects of surface roughness on the lubricant film behavior.