Thesis (Ph. D.)--INSEAD, 1996. / Includes bibliographical references (leaves 259-269).

Thesis (Ph. D.)--University of Hawaii, 1992. / Includes bibliographical references (leaves 352-368).

The objective of this research work is to investigate the practicality of magnetic workholding of non-magnetic synthetic quartz during high-speed grinding. This research work is sponsored by Quartzdyne and will be used as the starting point to applying single-piece rounding of its quartz. Hypotheses were created that would permit the authors to conclude that magnets are in fact worthwhile workholders for non-magnetic materials. Designs of Experiments were used to reject or fail to reject the null hypotheses. Experiments were carried out using a custom HAAS lathe, modified into a grinding center with an NSK live spindle, and neodymium-iron-boron magnets used to obtain both the holding and shear forces. Lastly, purchased polyolefin foam bumpers were used to increase the shear force, values were obtained with the Starrett force measurement machine. Input variables for the Design of Experiments (DOE) comprised of the holding force, feed-rate, part rotation, and in-feed size of cuts. Sample rotation relative to the magnets was the singular output variable. Experimental results were fitted with the correct distribution and modeled. Once a statistically significant model was attained input settings that minimized quartz sample rotation were determined and used to create an optimized program. Two sets of experiments were needed before the data could be properly fitted with a model. Thirteen out of fifteen samples remained stationary during the optimized program, which was adequate in failing to reject the second null hypothesis; a static sample at 350 RPM will remain static when undergoing high-speed rounding of its outside perimeter. Comparison of cycle times was crucial in reaching this conclusion; in fact, the cycle time of 7 minutes and 58 seconds for the optimized program was substantially less than Quartzdyne's estimated batch flow per piece cycle time of around 15 minutes. Obtaining a model was not possible or needed for the first hypothesis due to all experiments having zero rotation, therefore the authors also failed to reject the first null hypothesis; a static sample sandwiched between two permanent magnets with adequate holding force will remain stationary during rotation (min 250 RPM) Larger in-feed size cuts are possible when the quartz is square in shape –interrupted cuts. As it becomes cylindrical, cuts were reduced to experimental levels. Also, due to the amount of material being removed, the resin bonded wheel required dressing, without it rotation is expected. Variation was noticed while quantifying the shear force; it is attributed to the polyolefin foam bumper with its inconsistent coefficient of friction. A more uniform material, which can provide repeatable shear force values, would lessen the variation. All optimized program samples turned out perfectly round- even the two that had slight rotation.

Ti-6Al-4V has a wide range of applications such as in the automotive and aerospace industries. Nevertheless, titanium alloys are very difficult to machine by conventional methods. Micro-EDM is a non-conventional machining method that uses the thermal effect of precisely controlled sparks. Manufacturers are looking for the methods and optimal settings to increase the productivity of micro-EDM in terms of lessening machining time and tool wear. Moreover, surface integrity of the machined area is crucial for some products such as biomedical implants. The objective of this study was to investigate the effects of the micro-EDM process parameters on response variables, in order to understand the behavior of each parameter as well as to determine their optimal values. Although, there is a substantial amount of literature studying different aspects of micro-EDM, most of them were designed based on the one-factor-at-a-time experiments instead of studying all factors, simultaneously. This research was conducted through a series of experiments using a full factorial design. An analysis of variance was employed to analyze the findings and to determine the effect and significance of each process parameters on the response variables. The process parameters included voltage, capacitance, electrode rotational speed, and electrode coating. Voltage and capacitance were studied separately as well as in combination in terms of the discharge energy. Response variables consisted of machining time, tool wear, crater size, microhardness, and element characterization. The surface morphology and element characterization were studied through the application of SEM and EDS analysis. The findings indicated that voltage had a decreasing effect on machining time, while it increased the crater size. Capacitance decreased machining time and tool wear. It had an increasing effect on the surface hardness. The effects of the TN-coating and electrode rotational speed were not statistically significant. Voltage and capacitance were the only parameters affecting element characterization. The affected elements included Ti, Al, C, and W. The optimal process parameters for two sets of response variables were determined using Minitab 17.

As the aerospace industry continues to incorporate composites into its aircraft, there will be a need for alternative solutions to the current autoclaving process. Liquid composite molding (LCM) has proven to be a promising alternative, producing parts at faster rates and reduced costs while retaining aerospace grade quality. The most important factor of LCM is controlling the resin flow throughout the fiber reinforcement during infusion, as incomplete filling of fibers is a major quality issue as it results in dry spots or voids. Void formation occurs at the resin flow front due to competition between viscous forces and capillary pressure. The purpose of this work is to characterize capillary pressure in vacuum infusion, and develop a model that can be incorporated into flow simulation. In all tests performed capillary pressure was always higher for the carbon fiber versus fiberglass samples. This is due to the increased fiber packing associated with the carbon fabric. As the fabric samples were compressed to achieve specific fiber volumes an increase in capillary pressure was observed due to the decrease in porosity. Measured values for capillary pressure in the carbon fabric were ~2 kPa, thus the relative effects of Pcap may become significant in flow modeling under certain slow flow conditions in composite processing.

Discrete-event simulation can be a useful tool in analyzing complex system dynamics in various industries. However, it is difficult for entry-level users of discrete-event simulation software to both collect the appropriate data to create a model and to actually generate the base-case simulation model. These difficulties decrease the usefulness of simulation software and limit its application in areas in which it could be potentially useful. This research proposes and evaluates a data collection and analysis methodology that would allow for the programmatic generation of simulation models using production tracking data. It uses data collected from a GPS device that follows products as they move through a system. The data is then analyzed by identifying accelerations in movement as the products travel and then using those accelerations to determine discrete events of the system. The data is also used to identify flow paths, pseudo-capacities, and to characterize the discrete events. Using the results of this analysis, it is possible to then generate a base-case discrete event simulation. The research finds that discrete event simulations can be programmatically generated within certain limitations. It was found that, within these limitations, the data collection and analysis method could be used to build and characterize a representative simulation model. A test scenario found that a model could be generated with 2.1% error on the average total throughput time of a product in the system, and less than 8% error on the average throughput time of a product through any particular process in the system. The research also found that the time to build a model under the proposed method is likely significantly less, as it took an experienced simulation modeler .4% of the time to build a simple model based off a real-world scenario programmatically than it did to build the model manually.

Sinkholes are hazardous to buildings and their occupants, so a sensing device that can monitor underground changes is vital. Void Technology, developed in the Research and Development Center at Western Kentucky University, is creating a device that can improve monitoring for any movement underground. This device, created by Void Technology, is equipped with ESP8266, which is a Wi-Fi module that can send its information to the router in a wireless network. The focus of this thesis is on designing and developing an IOS framework application to show the signal strength capabilities in different buildings to find the optimum placement of the Void Technology devices. Each building, based on various construction materials, had different attenuations that could cause signal loss from the application to the ESP82266. The optimum place was found with this designed application. From this test experiment, it can be concluded that the application can show the signal strength based dBm. Thus, this new application is cost-effective as well as user friendly and which can help both the installer and homeowner to find the best position for installing The Void Technology with optimum signal strength.

The ductility of Q&P 1180 steel was studied with regard to retained austenite transformation under different strain paths. Specimens were tested in uniaxial tension in a standard test frame as well as in situ in the scanning electron microscope (SEM). Then digital image correlation (DIC) was used to compute the effective strain at the level of the individual phases in the microstructure. Stretching experiments were also performed using limiting dome height (LDH) tooling, where specimens were strained in both biaxial and plane strain tension. The experiments were done incrementally, for each strain path, and the retained austenite at each level of strain was measured using electron backscatter diffraction (EBSD). Retained austenite levels in the uniaxial tension case dropped from an initial measured level of about 8% to about 2% during an initial strain increment of 0.02, but then stabilized as the specimen was strained to 0.1. In the plane strain and biaxial tension cases retained austenite also dropped significantly during an initial strain increment of about 0.04, but then continued to decrease as the specimens were strained to failure. Biaxial tension, in particular, was the most effective strain path for transforming retained austenite to martensite, resulting in a final volume fraction of 0.3% at an effective strain of 0.3. Retained austenite in the plane-strain tension case dropped at a faster rate than in the biaxial tension case, but finished at about 1% at a strain of 0.1. The greatest limit strains were seen in the biaxial tension case, which may be partly explained by the more effective conversion of retained austenite than was seen in the uniaxial tension case.

Many factors contribute to people's physical inactivity, but among the leading factors is a lack of motivation. Fitness trackers have been shown to encourage an increase in exercise, but they are frequently abandoned within a few short months. For this thesis I developed and asynchronous-play social gaming platform, FitPlay Games, to fill the gap in motivation left by current fitness trackers. By providing users with a variety of asynchronous cooperative and competitive gaming styles, this platform enable them to find a motivation technique that works best for their lifestyle and fitness prowess. The platform encourages prolonged use of fitness trackers, helping users to have more healthy lifestyles. Individual games are designed to allow both the novice and the maven to have a chance at winning, leveling the playing field, and increasing motivation to win. The effectiveness, usability, and enjoyability of the social games will be assessed, with an emphasis on understanding differences in play habits due to gender and lifestyle.

Porous tungsten is used to manufacture dispenser cathodes due to it refractory properties. Surface porosity is critical to functional performance of dispenser cathodes because it allows for an impregnated ceramic compound to migrate to the emitting surface, lowering its work function. Likewise, surface roughness is important because it is necessary to ensure uniform wetting of the molten impregnate during high temperature service. Current industry practice to achieve surface roughness and surface porosity requirements involves the use of a plastic infiltrant during machining. After machining, the infiltrant is baked and the cathode pellet is impregnated. In this context, cryogenic machining is investigated as a substitutionary process for the current plastic infiltration process. Along with significant reductions in cycle time and resource use, surface quality of cryogenically machined un-infiltrated (as-sintered) porous tungsten has been shown to significantly outperform dry machining. The present study is focused on examining the relationship between machining parameters and cooling condition on the as-machined surface integrity of porous tungsten. The effects of cryogenic pre-cooling, rake angle, cutting speed, depth of cut and feed are all taken into consideration with respect to machining-induced surface morphology. Cermet and Polycrystalline diamond (PCD) cutting tools are used to develop high performance cryogenic machining of porous tungsten. Dry and pre-heated machining were investigated as a means to allow for ductile mode machining, yet severe tool-wear and undesirable smearing limited the feasibility of these approaches. By using modified PCD cutting tools, high speed machining of porous tungsten at cutting speeds up to 400 m/min is achieved for the first time. Beyond a critical speed, brittle fracture and built-up edge are eliminated as the result of a brittle to ductile transition. A model of critical chip thickness (hc) effects based on cutting force, temperature and surface roughness data is developed and used to study the deformation mechanisms of porous tungsten under different machining conditions. It is found that when hmax = hc, ductile mode machining of otherwise highly brittle porous tungsten is possible. The value of hc is approximately the same as the average ligament size of the 80% density porous tungsten workpiece.