http://hdl.handle.net/1974/802 Sun, 19 May 2013 05:35:52 GMT 2013-05-19T05:35:52Z http://hdl.handle.net/1974/8025 Title: FABRICATION AND STUDY OF AC ELECTRO-OSMOTIC MICROPUMPS Authors: Guo, Xin Abstract: In this thesis, microelectrode arrays of micropumps have been designed, fabricated and characterized for transporting microfluid by AC electro-osmosis (ACEO). In particular, the 3D stepped electrode design which shows superior performance to others in literature is adopted for making micropumps, and the performance of such devices has been studied and explored. A novel fabrication process has also been developed in the work, realizing 3D stepped electrodes on a flexible substrate, which is suitable for biomedical use, for example glaucoma implant. There are three major contributions to ACEO pumping in the work. First, a novel design of 3D “T-shaped” discrete electrode arrays was made using PolyMUMPs® process. The breakthrough of this work was discretizing the continuous 3D stepped electrodes which were commonly seen in the past research. The “T-shaped” electrodes did not only create ACEO flows on the top surfaces of electrodes but also along the side walls between separated electrodes. Secondly, four 3D stepped electrode arrays were designed, fabricated and tested. It was found from the experiment that PolyMUMPs® ACEO electrodes usually required a higher driving voltage than gold electrodes for operation. It was also noticed that a simulation based on the modified model taking into account the surface oxide of electrodes showed a better agreement with the experimental results. It thus demonstrated the possibility that the surface oxide of electrodes had impact on fluidic pumping. This methodology could also be applied to metal electrodes with a native oxide layer such as titanium and aluminum. Thirdly, a prototype of the ACEO pump with 3D stepped electrode arrays was first time realized on a flexible substrate using Kapton polyimide sheets and packaged with PDMS encapsulants. Comprehensive experimental testing was also conducted to evaluate the mechanical properties as well as the pumping performance. The experimental findings indicated that this fabrication process was a promising method to create flexible ACEO pumps that can be used as medical implants and wearable devices. Description: Thesis (Ph.D, Mechanical and Materials Engineering) -- Queen's University, 2013-05-06 10:57:48.077 Tue, 07 May 2013 04:00:00 GMT http://hdl.handle.net/1974/8025 2013-05-07T04:00:00Z http://hdl.handle.net/1974/7992 Title: Laser Welding of Alumina Ceramic Substrates with Two Fixed Beams Authors: Sedore, Blake Abstract: Laser welding was investigated as a potential joining technology for alumina ceramic substrates. The objective of this study was to develop a method to preheat the ceramic using a single defocused laser beam prior to welding. Engineering ceramics are employed in a variety of systems and environments due to their unique properties. Joining technologies must be developed to facilitate the manufacture of complex or large ceramic components. Laser welding is advantageous as it forms joints rapidly, and does not introduce intermediate materials to form the bond, which can have deleterious effects. The Laser Machining System (LMS) at Queen’s University was adapted for this study. A defocused far-infrared (FIR) laser beam was positioned to overlay a focused near-infrared (NIR) laser beam; the defocused FIR beam preheated the ceramic substrate and the focused NIR beam formed the weld. A finite element model was developed in COMSOL MultiPhysics to simulate the preheating processes and to develop a preheating protocol. The protocol was implemented using the FIR beam and adjusted to achieve preheating temperatures of 1450, 1525, and 1600degC. Welds were performed on 1 mm thick alumina plates using the preheating protocols and NIR beam powers of 25, 50, and 75 W. Weld speed was held constant throughout the study at 0.5 mm/s. The preheating protocols were successful at achieving near-constant preheating temperatures, with standard deviations below 32 degrees. Partially penetrating welds were formed with the NIR beam at 25 W, and fully penetrating welds at 50 and 75 W. Large pores were present in the 25 W and 50 W welds. Minimal porosity was observed in the welds formed at 75 W. All of the welded plates experienced a transverse fracture that extended perpendicular to weld, and a longitudinal fracture extending parallel to the weld. This study shows that a fixed defocused laser beam can successfully preheat alumina substrates to the high temperatures required for welding; however, non-homogenous cooling results in fracture. Increasing the preheating beam diameter or introducing an auxiliary means to provide a controlled cool-down cycle may mitigate these effects. Description: Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2013-04-29 17:59:57.43 Tue, 30 Apr 2013 04:00:00 GMT http://hdl.handle.net/1974/7992 2013-04-30T04:00:00Z http://hdl.handle.net/1974/7988 Title: Multi-sensor besed framework for gear condition monitoring Authors: Rezaei, AIDA Abstract: In recent years, there has been considerable interest in developing efficient machine diagnostics and prognostics tools for quantitative estimation of systems condition and remaining useful life. Often, it is beneficial to combine several measures into a single feature for machine condition monitoring purposes. Selection of appropriate features represents a key step to satisfy machine condition monitoring requirements. Gearboxes represent one of those complex systems where classification of fault stages and types (diagnostics) and remaining useful life prediction (prognostics) remain a challenging task. This thesis focuses on certain aspects of engineering tribology related to gearbox components diagnostics and prognostics based on multi-sensor measurements. A dynamic large-scale mechanical system test-bed has been designed, built, and commissioned. This apparatus is based on the accessory gearbox of the GE J85 turbojet engine, which operates in a number of aircrafts, such as the Canadair CT-114 Tutor. The test rig is equipped with a high speed data acquisition system along with a variety of sensing technologies such as vibration, sound, and acoustic emission transducers in addition to thermocouples, power cells and loading mechanisms. Various attributes are compared for detecting faulty gears and a non-parametric statistical method is used as a quantitative measure of transmission quality. The feature importance level is determined by the significant difference level; and the independent coefficient of the candidate feature is used to compare and rank different time and frequency features. An optimal feature set is then evaluated using the support vector machine classification method by considering a monotonically increasing classification rate. In addition, the selected feature subset has the potential to achieve a better recognition rate than those selected by other heuristic methods such as the mutual information method. This thesis also introduces two metrics which identify the appropriate prognostic feature: load stability ratio and degradation value. The two criteria can be used to compare candidate prognostic features to determine which are most useful for prognosis. An optimization-based method is then used to obtain the optimal feature. The optimized feature can be used with a degradation path modeling to estimate RUL (remaining useful life) for the specific gear system. Description: Thesis (Ph.D, Mechanical and Materials Engineering) -- Queen's University, 2013-04-27 16:51:19.654 Tue, 30 Apr 2013 04:00:00 GMT http://hdl.handle.net/1974/7988 2013-04-30T04:00:00Z http://hdl.handle.net/1974/7965 Title: Stiffness Analysis of Cable-Driven Parallel Robots Authors: Moradi, Amir Abstract: The aim of this thesis is the stiffness analysis of cable-driven parallel robots. Cable-driven parallel robots have drawn considerable attention because of their unique abilities and advantages such as the large workspace, light weight of cable actuators, easy disassembly and transportation of the robot. The mobile platform of a cable-driven parallel robot is attached to the base with multiple cables. One of the parameters that should be studied to make sure a robot is able to execute a task accurately is stiffness of the robot. In order to investigate the stiffness behaviour of a robot, the stiffness matrix can be calculated as the first step. Because cables act in tension, keeping the positive tension in cables becomes a challenge. In order to have a fully controllable robot, an actuation redundancy is needed. These complexities are addressed in the thesis and simulations. In this thesis, the complete form of the stiffness matrix is considered without neglecting any terms in calculation of the stiffness. Some stiffness indices such as single-dimensional stiffness based on stiffness ellipse, directional stiffness and condition number of the stiffness matrix are introduced and calculated and stiffness maps of the robot are developed. In addition, the issue of unit inconsistency in calculating the stiffness index is addressed. One of the areas which is also addressed in this thesis is failure analysis based on the stiffness of robot. The effect of the failure in one or more cables or motors is modelled and stiffness maps are developed for the failure situation. It is shown that by changing the anchor position and mobile platform orientation, the lost stiffness after failure of a cable or motor can be retrieved partially. Optimum anchor position and mobile platform orientation are identified to maximize the area of the stiffness map. Condition number of the stiffness matrix while robot is following a trajectory is optimized. In addition, when one cable fails during the path planning, the recovery of the robot is studied. Finally, these analyses on stiffness and failure provide the designer with the necessary and valuable information about the anchor positions and actuator toques. Description: Thesis (Ph.D, Mechanical and Materials Engineering) -- Queen's University, 2013-04-27 08:47:26.297 Sat, 27 Apr 2013 04:00:00 GMT http://hdl.handle.net/1974/7965 2013-04-27T04:00:00Z