Master of Philosophy (M.Phil.)

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Browsing Master of Philosophy (M.Phil.) by Subject "MECHANICAL ENGINEERING-Dissertations"

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    Design and development of PZT based micropump for microfluidic applications
    (2020) Munas FR; Amarasinghe Y.W.R
    The present technical context is promptly growing in implementing onsite microfluidic utensils utilized in microfluidics owing to their great demand. The microfluidics mainly involves in implementing minuscule devices to deal with minute volumes of fluids. Manufacturing these microfluidic devices like micropumps is a great challenge and micropumps are very much indispensable to regulate and convey fluid in minute scale. In this research a PZT based micropump was designed and developed for microfluidic applications. A PZT actuated brass diaphragms and a comprehensive flow arrangement are the important elements of this micropump structure. Basically, the design prominences on a cross junction, engendered by a nozzle jet with a pump chamber and two inlet and an outlet channel respectively. In this sense, the fluid flow rectification is done by nozzle jet feature to expedite the fluid path within the system during every vibration cycle of PZT diaphragm. This micropump device was developed with layer by layer fabrication of polymethyl methacrylate (PMMA) plates using laser cutters and all the layers were squeezed in to attain required structure. In order to recognize the physiognomies of flow and to verify the experimental outcomes with simulated data, numerical simulation analysis in ANSYS were carried out. In addition, the PZT diaphragms were under taken for eigenfrequency study analysis in COMSOL Multiphysics as well. In this sense, the applied frequency of the piezoelectric diaphragms was varied by using the prescribed control system developed for this device. As per the test results, the maximum flow rate of 31.15 ml/min achieved at the frequency of 100 Hz. In addition, the thin film deposition techniques and the thermo elastic damping analysis on PZT actuators were also analyzed to identify the performance enhancement of this micropump. Since monitoring pressure and getting response is vital in microfluidic devices, design and simulation of MEMS based piezoresistive pressure sensor has been carried out. According to the piezoresistive structural coupled field analysis, the optimal diaphragm structure was chosen among three kinds of diaphragms considered for this study. Further, the thermo mechanical behavior of piezoresistive pressure sensors have also been considered in this research. At last, the complete numerical simulation was done for the micropump fluid flow coupled with the designed pressure sensor. According to this analysis, the pressure sensor gives the favorable sensitivity variation over micropump discharge pressure. Hence the developed micropump is not only for a specific application but also worthwhile in a wide range of microfluidic applications.
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    Development of safe operational criteria for ships based on vibration analysis
    (2019) Dasanayaka DMPM; Perera PABAR
    The origin of shipboard vibrations is dominantly determined by vessels propulsion system, main machinery, auxiliary systems, pumps, breaking of the waves at the ship hull, etc. All of these peripherals and systems origin the static and dynamic induction of vibration onboard a ship while various analytical and statistical methods may be declared to assess the levels of vibration in order to declare a combined safe operational criteria for ships depending on the spectrums. Few similar researches had been completed on identification and quantified estimation of the noise or the multiple vibrations resulted from ship and machinery during passage. However, those researches were addressed mainly towards developing a relationship for a single new ship or category particularly prior to commissioning. This research was focused on studying the shipboard transferred vibration (of the vessel's structure and to sea) and vibration spectra generated by shipboard machinery / structures using portable vibration analysers for in-service ships. Data was recorded onboard classes of ships/ craft (new and old) through a series of sea trials to establish a common relationship for ships and to comprehend use this methodology as a tool in understanding complex patterns of ship vibration spectra to predict possible defects. The study commenced on 05th May 2014 under the patronage and guidance of the Department of Mechanical Engineering, University of Moratuwa to identify the unique patterns of shipboard vibration signatures generated whilst vessels are on sail, paying attention to the external forces and to develop a data base with existing vibration levels after being identified as safe operational limits (depending on the observations based on datum readings). The research data was collected using two modern vibration analysers (Make: Areva, Model: Oneprod MVP -2C, Country of Origin: France, Frequency Range: 0 – 40,000 Hz) integrated with Areva XPR 300 software system uploaded computers for the spectrum analysing task. Sea trials at following conditions had been carried out. a. Sea State : 3 and below; b. Ship Loading Condition : Full Load, Half Load; c. Wind Condition : Moderate < 15 knots; d. Sea Direction : Ahead, Astern Numerical relationships and probabilities were established using practical outcomes of the sea trials. Data analysis and Spectrum datum comparison were used to identify and quantify the safe operational vibration limits with respect to individual classes of ships being the primary outcome. The similar defect patterns and respective statistics were averaged to find out a common relationship to identify a figure named “Shipboard Machinery Vibration Safety Index (Sv)”, which was the secondary outcome of the study.