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This thesis is missing page 48, all other copies of this thesis are missing the page as well. -Digitization Centre / Metal injection molding (MIM) employs the advantages of injection molding and powder metallurgy and provides a high productivity means to form intricate, low-cost, high performance metal parts. One of the most unique characteristics of MIM is the binder system and the consequent debinding step, which is considered to be major process improvement barrier in the MIM process. A MIM part with a thick section suffers from a long debinding cycle and it is difficult to avoid defects. Therefore, it is always of interest to find out a method to quickly debind a thick part without defects. PowderFlo® feedstock combines metal powder with an aqueous agar-gel binder system and requires simple air-drying followed by thermal debinding. However, previous studies on this agar-gel binder feedstock mainly focus on sintering, while the debinding step has lacked sufficient attention. A debinding study on agar-gel binder system is conducted in the present project. The metal compacts are formed via compression molding and injection molding, followed with thermal debinding in order to understand the effects of process parameters on debinding with respect to thickness to determine a good debinding schedule. The thickness transition between thick and thin section is particularly important in the debinding to find a protocol to make parts with both thick and thin sections. Thermal debinding experiments show that the initial heating rate is the most significant factor due to it may cause visible defect directly and an increase of initial and secondary heating rates may retard binder removal. The air-drying time has less influence on binder extraction for thicker section. Extending the holding time for water and polymer removal is beneficial to obtain better dimensional control. The overall debinding process parameters have larger effects on thicker parts. For the thickness transition, it is suggested to avoid the combination of too thin and too thick section, increase the joint area, and provide uniform packing during molding. / Thesis / Master of Applied Science (MASc)

No / A comprehensive study into the performance of 4 injection molding machines is reported, using identical mold, polymer, and processing conditions. Start-up dynamics and process repeatability were directly compared across machine technologies. One servohydraulic, one proportional hydraulic and two servoelectric machines were used in the study, ranging in age from 14 years to 1 year old at the time of the study. Experiments were carried out at identical set molding conditions for a run of 400 parts and part quality and process parameters monitored. Results showed a significant start up period in each case, correlating strongly to mold temperature. Age of machine proved to be the most significant factor in determining process repeatability; modern machines having significantly lower variation than older ones. Differences between the operating characteristics of hydraulic and electric machines were detected, control of screw position in hydraulic machines being less repeatable, although this had a minor effect on part repeatability. Electric machines were found to use up to 4 times less energy than their hydraulic counterparts and operate more efficiently.

This study investigates the effects of a split injection strategy on combustion performance and exhaust emissions in a high speed direct injection optical diesel engine. The investigation is focused on the effects of injection timing, quantity, and the dwell angle between the injections using commercially available diesel fuel. Three different split injection strategies including 50:50, 30:70, and 70:30 have been investigated. Additionally, the effect of total injected fuel quantity using total fuel quantities of 10 mm3 and 20 mm3 has been investigated. Moreover, the effect of variable and fixed dwell angle in split injections has been examined for five different values between 5o CA and 25o CA in the case of variable and 10o CA for the fixed dwell timing. The last parameter investigated was the injection timing, nine injection timings have been tested for each of the strategies. A Ricardo Hydra single cylinder optical engine running at 1500 rpm was used in this investigation. Conventional methods such as direct in-cylinder pressure measurements and heat release rate analysis have been employed. In addition, optical techniques such as high speed video imaging and two-colour have been applied, aimed at in depth analysis of the effects of the aforementioned parameters on engine performance and emissions. Furthermore, a significant amount of effort was devoted to the development and application of the Laser Induced Excipex Fluorescence (LIEF) technique so that simultaneous fuel liquid and fuel vapour distribution could be visualised. This investigation concludes that split injection strategies have the potential to reduce diesel exhaust emissions while maintaining a good level of fuel economy, provided that injection timings and the dwell angle between injections are appropriately selected. Further investigations are required in order to examine the effect of split injection under different engine operating conditions and speeds. In addition, the effect of alternative fuels must be considered. Moreover, the application of LIEF technique for quantitative fuel vapour concentration measurement should be considered through further optimisation of the LIEF system and careful calibration experiments.

Thèse d'exercice : Médecine : Nancy 1 : 2009. / Titre provenant de l'écran-titre.

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Thèse (Ph. D.)--Université Laval, 2008. / Titre de l'écran-titre (visionné le 12 janvier 2009). Bibliogr.