Browsing by Subject "Mechanical engineering"
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Item Ablation and ignition by impinging jet flows(2013-12) Kurzawski, Andrew Joseph; Ezekoye, Ofodike A.Two separate heat transfer problems that involve jet flows impinging on a reacting target are studied through modeling and experimentation. The first system is an ablating carbon-carbon specimen exposed to high heat fluxes from an oxy-acetylene torch which has applications in atmospheric re-entry vehicles. The second system involves the penetration of hot gases into the void space in a compartment. The fire protection stands to benefit from knowledge of this system, both in building component design and informing firefighting personnel. Both problems can be modeled as a jet flow impinging on a flat surface where hot gases from the jet lead to primarily convective heat transfer. Ablation experiments are outlined and a theoretical framework is developed. A serial inversion technique is tested for predicting the recession rate observed in the experiments. A novel inversion technique that takes advantage of parallel computing is developed to circumvent the shortcomings of the serial technique. These techniques are then compared to synthetically generated and experimental data for different data streams and error signals. Compartment-scale experiments were conducted to test hot gas penetration into void spaces. Anecdotal evidence was observed outside of the intended test section prompting further investigation into the mechanics of ignition in void spaces. A theoretical framework is established to predict possibility of ignition under varied environmental factors. A leakage-scale experiment is constructed to gain insight into conditions that result in ignition of materials in void spaces.Item Carbon composite strengthening: Effects of strain rate sensitivity and feature size(2012-05) Brannigan, Eric; Jankowski, Alan F.; Rivero, Iris V.; Idesman, Alexander V.Strain rate sensitivity of strength is analyzed for a bulk, turbostratic carbon reinforced epoxy resin composite. The strength of the composite was measured using a rate-modified version of the standard, 3-point bending test. Rate sensitivity of stress was calculated by varying the strain rate of stress on the samples, and measuring the increase in yield strength. Metal reinforced carbon matrix composite coatings were also examined, with CuC, NiC, and CuNiC samples analyzed using nano-indentation and tapping mode AFM hardness and modulus measurements. The carbon structures within the coatings are nanoscale, and characterization of the carbon features in the coatings and the bulk fiber composite allow for conclusions to be drawn regarding the structured relationship within metallic and non-metallic carbon composites. For the fibers, we find that bending strength is rate sensitive as attributed to the turbostratic carbon-fiber component. The material has a strength to weight ratio comparable to Ti-6Al-4V alloy. For the coatings, we find that the hardness and elastic modulus are dependent on whether the morphology is layered versus particulate, with the nanodisperse morphology having the highest hardness and elastic modulus.Item Development of a fully automated rapid irradiated sample transport system for neutron activation analysis(2014-12) Copple, Blake Robert; Biegalski, Steven R.; Landsberger, SheldonThe need for trace, minor and main element analysis becomes more prevalent each year with an every expanding variety of applications. Neutron Activation Analysis (NAA) is an attractive non-destructive analysis tool that can be utilized on small samples regardless of what physical state the material is in. The analysis process however, typically requires researchers to physically handle a radioactive sample in order to transport the sample to detection systems for data gathering. The purpose of this project was to design a Fully Automated Rapid Irradiated Sample Transit (FARIST) system that could deliver samples into a reactor core and then transfer them to a detector for analysis with zero human interaction. The system would be designed to hold up to 30 samples prior to analysis with the irradiation, decay, and counting times programmed in initially so that once analysis was initiated, no user interaction was required for the next 29 samples. The last requirement of the system was that it supports cyclic NAA. This work discusses the science and history behind NAA as well as the design, construction, installation, and testing of the new FARIST system.Item The development of replicated optical integral field spectrographs and their application to the study of Lyman-alpha emission at moderate redshifts(2015-08) Chonis, Taylor Steven; Hill, Gary J.; Finkelstein, Steven L; Gebhardt, Karl; Greene, Jenny E; Jaffe, Daniel TIn the upcoming era of extremely large ground-based astronomical telescopes, the design of wide-field spectroscopic survey instrumentation has become increasingly complex due to the linear growth of instrument pupil size with telescope diameter for a constant spectral resolving power. The upcoming Visible Integral field Replicable Unit Spectrograph (VIRUS), a baseline array of 150 copies of a simple integral field spectrograph that will be fed by 33,600 optical fibers on the upgraded Hobby-Eberly Telescope (HET) at McDonald Observatory, represents one of the first uses of large-scale replication to break the relationship between instrument pupil size and telescope diameter. By dividing the telescope's field of view between a large number of smaller and more manageable instruments, the total information grasp of a traditional monolithic survey spectrograph can be achieved at a fraction of the cost and engineering complexity. To highlight the power of this method, VIRUS will execute the HET Dark Energy Experiment (HETDEX) and survey ~420 square degrees of sky to an emission line flux limit of ~1e-17 erg/s/cm^2 to detect ~1e6 Lyman-alpha emitting galaxies (LAEs) as probes of large-scale structure at redshifts of 1.9Item Factors in charge preparation and their effect on performance and emissions from a direct injection spark ignition engine(2001-08) Alger, Terrence Francis; Matthews, Ronald D.; Hall, Matthew JohnThe effects of flow field and Start Of Injection (SOI) timing were investigated to determine their effect on mixture preparation in a direct injection spark ignition engine. The flow field and SOI timing were varied in order to produce changes in the location and amount of surface wetting and to vary the extent of in-cylinder mixing. The equivalence ratio at the spark plug was measured using a fiber optic probe developed at The University of Texas at Austin. The flow field and SOI timing were shown to have an effect on both the equivalence ratio history and the equivalence ratio at ignition, as well as the cyclic variation in its value. A separate technique, also developed at The University of Texas at Austin, used IR absorption to measure the time resolved hydrocarbon (HC) emissions in the exhaust port. The location of the in-cylinder surface wetting had a strong influence on the level of HC emissions from the engine. Engine performance was influenced by both the amount of mixing and surface wetting. Liquid fuel effects in the cylinder were investigated using schlieren imaging and Mie scattering to visualize both the in-cylinder evaporation of fuel films and particulate matter formation respectively. In-cylinder evaporation was found to be a slow process and dependent on the difference between the fuel boiling point and the piston surface temperature. The in-cylinder formation of particulates was found to be dependent on the in-cylinder flow field and showed high cycle-to-cycle fluctuations.Item Parallel finite element simulator of planetary gear trains(2001-05) Bajer, Andrzej; Demkowicz, LeszekItem Thermal characterization of InAs interfacial misfit arrays using nanosecond thermoreflectance method(2015-05) Nguyen, Khai Ta; Wang, Yaguo; Bahadur, VaibhavThermal properties are of the utmost importance because of the ever growing demands given to us by high-power and ultrafast electronics. A nanosecond thermoreflectance method was developed to determine the thermal conductivities of InAs interfacial misfit arrays (IMF). These interfacial misfit arrays were designed to improve the optical properties, such as photoluminescence, of these materials in order to improve electronic devices. A study was performed to see if the thermal properties of these materials were affected in any way. The nanosecond thermoreflectance method was benchmarked with control samples of InAs and GaAs substrates, and the thermal conductivities were close to that of bulk value. After performing the experiments, it was found that the thermal conductivity varies inversely with photoluminescence. It was also found that the thermal interface resistance between the growth and the substrate was inversely proportional to the thickness of the IMF growth.Item Transformational indicators : deciding when to develop transformable products(2010-08) Camburn, Bradley Adam; Wood, Kristin L.; Jensen, DanTransformable products (or transformers), those with two or more functional states, are increasingly utilized by our society. As the mobility and complexity of life increases, so must the adaptability of the products which we use. We need new design techniques to develop more adaptable devices, such as transformers. The purpose of this study is to propose a response to the question “When is it preferable to implement a design approach focused on developing transformable products over an approach focused on developing primary function, non transforming products?” Our response to this question comes in the form of a method. The method helps a designer or design team consider the benefits of developing a transformer at an early stage in the design process. Research includes a deductive and an inductive study which are used to identify transformation indicators or context properties and usage factors that identify when it is preferable to build a transformable device. Static function-state indicators are also presented. These are contrary to transformation indicators in that they identify contexts suitable for developing non-transforming devices. Our technique seeks to improve the outcome of a design project by encouraging the consideration of transformable solutions and aiding in the selection of an appropriate design process. This method for testing the presence of these indicators in exemplary design contexts is presented. One such application is the design of an autonomous bridge-health monitoring system.Item Universal design : designing products that all individuals can use(2013-08) Talley, Austin Bates; Crawford, Richard H.In today's world there is a need for products and services that are accessible to all individuals. Universal Design is the concept that products and environments should be usable by all people, to the greatest extent possible, without the need for adaptation or specialization. There is a growing need for such products. However, many products are not accessible to all potential customers, arguably due to a lack of experience, design tools, and engineering methods for creating universally designed products. This research compares paired products to determine the differences between "Universal Design (UD)" and "Standard" Products. For each pair of products, a functional model and activity diagram were developed and analyzed. For each product pair, the identified differences in the products were recorded in a Universal Design differences database. Through systematic analysis of the Universal Design differences database and other research in Universal Design, a set of three Handheld Universal Design Tools was created. The toolset consists of the Handheld Universal Design Checklist, The Handheld Universal Design Guidelines, and the Handheld Universal Design Matrix. These three tools are designed to be used in the concept generation phase of product design or redesign. The Handheld Universal Design Tools were evaluated using a human subjects experiment. Control and test groups were asked to generate concepts for redesigning a product. The metrics of quality, universality, laterality, senior usability and inclusivity were used to evaluate the design concepts. The results of the study suggest that Handheld Universal Design Tools assist engineers in generating design concepts appropriate for Universally Designed products. As a part of the research, Universal Design was presented to first year mechanical engineering students with pre- and post- surveys on the students' perceptions of engineering. Subsequent analysis of the surveys indicated that exposure to Universal Design affects students' perceptions of engineers' overall role in society and their capacity to help others. The Handheld Universal Design Checklist, Guidelines and Matrix represent an initial step to provide engineers with tools to create Universally Designed products.