Engineering Commons^™

Additive Layer Manufacturing Of Ti-6al-4v By Electron Beam Melting From Powder Particles: Solid, Mesh And Foam Components Study, Sara M. Gaytan

Open Access Theses & Dissertations

Additive Manufacturing by Electron Beam Melting Rapid Manufacturing is a technology that consists of the fabrication of a CAD design by melting powder particles in a layer by layer fashion. In this study, Ti-6Al-4V has been utilized to fabricate solid, mesh and foam components by EBM technologies. Powder analysis of Ti-6Al-4V was performed to obtain a better understanding of the porosity obtained by the system. After proper optimization of the machine, and porosity control, microstructural analysis was performed to the components already mentioned and correlated by transmission electron microscopy. Besides the microstructural analysis, tensile and hardness testing was performed to …

Hybrid Approach For Site Selection Using Impact Assessment And Principal Component Analysis, Ugandhar Reddy Kondamadugula

Open Access Theses & Dissertations

Principle component analysis (PCA) is used to analyze week data of emission of particulate material from the Residential community. In this Thesis we selected five sites maps where sensors are arranged to collect particulate materials PM0.25, PM 10.Impact Assessment on the site areas are done in the first case,the results Impact Assessment on the site shows that the Global warming potential is really high at the site when the analysis is run for hundred years the Global warming potential has a very high impact on Environment leading to various health hazards. Secondly Principal Component Analysis is used to find out …

Assessing Repeatability Of Four-Point Bending Method For Estimating Fatigue Cracking Of Hot Mix Asphalt, Sara -. Montazeri

Open Access Theses & Dissertations

The objective of this thesis was to assess the repeatability of four-point bending method for estimating fatigue cracking of hot mix asphalt. This experimental research examined the influence of mix proportions, specifically asphalt and air void contents, on fatigue behavior of asphalt beam specimens in the laboratory tested with four-point bending method of loading. Following the relevant specifications, the strain-controlled mode of loading was selected. Fatigue failure is expected to occur at the cycle which the flexural stiffness of asphalt specimen reduced to 50% of initial amount. Up to a 1,000,000 cycles of loading were applied to each specimen.

Different …

High Temperature Oxidation Characteristics Of Nb-10w-Xcr Alloys, Maria Del Pilar Moricca

Open Access Theses & Dissertations

The use of refractory metals in high temperature applications has been attractive for several years. Systems based on niobium represent a potential new generation of refractory materials systems because of their low density, high melting points, and strength at elevated temperatures. Despite these desirable characteristics, the widespread use of niobium-based alloys is limited because its oxidation resistance is still inadequate for structural applications. Understanding the oxidation kinetics of Nb-based alloys and the role of the different phases in the oxidation process is of crucial importance to improve the oxidation resistance of these materials.

The effect of Cr content on the …

Design Of A Low Voltage Analog To Digital Converter, Praveen Kumar Palakurthi

Open Access Theses & Dissertations

For the past 40 years, the number of transistors per chip has been increasing at an exponential rate confirming Moore's Law regarding the growth of chip complexity. Increases in transistor count have led to enhancements in functionality and made possible products with features that were unimaginable ten years ago. Consequently, the resulting increase in digitization in all electronics, across a wide range of applications, requires the Analog-to-Digital Converters (ADCs) with a higher resolution and lower power consumption. The evolution of the integrated circuit technologies and scaling methodologies partially helps in providing faster circuits and allowing complex functionalities in a given …

Electric Power Distribution Optimization Using Evolutionary Algorithms, Sowmya Parimi

Open Access Theses & Dissertations

In the present research, a new evolutionary algorithm is developed to solve the component allocation problem in electricity distribution systems. The problem addresses the upgrade/design of an electricity distribution system with the objective of minimizing expected system downtime subject to cost and repair time constraints. The algorithm is tested on the Dual Element Spot Network (DESN) configuration which is one of the most commonly used configurations by the power industry. This algorithm is demonstrated with two examples.

Microstructural Characterization Of Overaged Gtd-111 Hp Turbine Buckets, Oscar Quintero

Open Access Theses & Dissertations

Superalloys are metallic materials that exhibit excellent mechanical strength and creep resistance at high temperatures. They have good surface stability and are corrosion resistant. Superalloys are mostly used in the aerospace industry, gas turbine engines and blades (hot zones of gas turbines), and where extreme heat is encountered. The focus of this research was on the GTD-111 Ni-base superalloy, which is a General Electric (GE) proprietary superalloy mostly used in gas turbine blades with the form of high pressure or first stage buckets. This alloys features better mechanical properties, creep resistance, and a higher stress rupture temperature than the commonly …

Discrete Element Modelling Of Silicon Nitride Ceramics: Crack Formation And Propagation In Indentation Test And Four Point Bending Test, Rajeev Senapati

Open Access Theses & Dissertations

Advanced ceramic materials have been extensively used in aerospace, automobile and other industries. However, the reliability of the advanced ceramics is the major concern because of the brittle nature of the materials. This work aims to model silicon nitride ceramics using Discrete Element Method (DEM) and simulating the crack formation and propagation. DEM software package PFC2D is used to simulate indentation test and four point bending test on silicon nitride ceramics and the behaviour of crack formation and propagation is identified. The numerical representation of ceramic materials is done by generating a densely packed particle system using the specimen genesis …

Integrated Finite Element Analysis Program To Evaluate Pavement Performance And Predict Non-Destructive Testing Response, Cesar Tirado

Open Access Theses & Dissertations

The response of a pavement system under wheel loading has been a subject of research for many decades. Several models have been developed to predict pavement performance based on layer deformation and fatigue cracking. Among them stand out computer programs based on linear elasto-static layered systems and viscoelastic-plastic models; however, newer or more advanced constitutive models cannot be rigorously incorporated into them. In contrast, finite element techniques allow incorporation of nonlinear and viscoelastic-plastic behavior of the pavement materials but licensing of software and the need to train personnel greatly limits its use by highway agencies. A mechanistic-empirical (M-E) approach for …

Impacting Testing Of High Temperature Ceramics Through The Use Of A Vitiated Heater For Hot And Cold Fire Collisions, Adrian Trejo

Open Access Theses & Dissertations

Material testing is a crucial step during the design process as particular materials serve as safety and life saving conditions. In this study, a MoSi2 is chosen as the target specimen to undergo impact under high temperatures. An impact apparatus is designed and constructed for the purpose of propelling alumina particles at high velocities. A nozzle using compressed nitrogen gas is used to fire the particle at the desired velocities. Due to the possibility of thermal shock occurring at higher temperatures, a separate nozzle utilizing vitiation heating is designed to fire the particle at equally higher temperatures to prove the …

An Experimental Study Of The Hydrodynamics Of Multiphase Flow In Fluidized Beds, Gerardo Vargas

Open Access Theses & Dissertations

Fluidized bed reactors have been widely used as a gasifier in coal gasification processes to convert coal into other forms of energy. At this stage, full fluidization is required to attain the best thermochemical reaction within the fluid-solid mixture. This can only be achieved if the fluid is maintained between minimum fluidization and terminal velocities. To better understand the hydrodynamics of multiphase flow, a fluidized bed was designed and constructed to carry out the investigation. Compressed air and 1-mm glass beads were used to determine gas minimum fluidization and terminal velocities at three different particle concentrations. The solids were enclosed …

Methodology To Develop A Minimum Cost Acceptance Sampling Plan For Highway Construction, Gandhar Wazalwar

Open Access Theses & Dissertations

Quality Assurance has always been a part of manufacturing processes. Since World War II, Acceptance Sampling has been introduced and implemented for quality control and improvement. Since statistical methods are applied for quality assurance, especially in acceptance sampling, various methods are becoming popular among the highway agencies over the period of time. As a result, several specifications have been designed to date based upon different statistical theories, each with its own advantages and shortcomings. Acceptance is a form of quality assurance which is employed as an audit tool for decision making to accept or reject the product based on its …

Vision-Based Virtual Mouse System, Tom Wanjala Watiti

Open Access Theses & Dissertations

This thesis describes a virtual mouse system that utilizes machine vision technology to enable a user to navigate through software window screens on a standard personal computer, access and control software, and/or peripheral devices attached to the personal computer. Utilizing the virtual mouse, the user can execute the standard control functions of the system mouse required to perform software application selection functions and navigation tasks without physical interface with the controlled computer. The machine vision algorithm utilizes a set of four simulated photoelectric sensors, with Gaussian filter sensitivities, to compute and track the mouse location. By utilizing Gaussian filters, instead …

Estimating Variation In Stiffness And Volume Change Of Clays From Geochemical And Index Properties, Cynthia Roxanna Zuniga

Open Access Theses & Dissertations

Clayey soils from six different locations in Texas were analyzed and evaluated with respect to their expansion and shrinkage and change in stiffness associated with moisture content variation. These soils consist of five high plasticity-index (PI) clays (PI greater than 25) and one low-PI clay (PI = 17). The behavior of the clays changes dramatically with moisture content fluctuation, thus causing stiffness and volume changes throughout the year. Total or differential volume movements caused by swell or shrinkage strains of expansive soils and reduction in modulus can exert enough pressure to damage the pavements and cause maintenance problems.

The intent …

Laminar Burning Velocities Of Gas Mixtures, Vishwanath Reddy Ardha

Open Access Theses & Dissertations

In this study, burning velocities of hydrogen-carbon monoxide (H2-CO) mixtures, which are primary constituents of syngas fuels, are measured. The effect of different burner systems, H2 concentration, and different measurement techniques on the burning velocities of H2-CO mixtures is also discussed. The burning velocities of H2-CO mixtures increase with the increase in H2 content in the mixture. When compared with different burner systems using different methods, the burning velocity data almost coincide in the lean condition, but at rich condition the data stray away from each other. The burning velocities of actual syngas compositions (based on different sources of coal) …

Failure Analysis And Materials Characterization Of Hip Implants, Amanda Marie Bastidos

Open Access Theses & Dissertations

This research focused on the microstructural characterization and failure analysis of hip implant components. The main hip components analyzed were the femoral heads and the ultra-high molecular weight polyethylene (UHMWPE) liners. Previous research has shown that hip implants tend to fail by the PE liners due to adhesive and abrasive wear, delamination, and third body particles (metals, ceramics, and PE). The methods and procedures for analyzing the said failures consisted of non-destructive and destructive evaluations. Non-destructive evaluations included of techniques such as visual characterization and dye penetrant inspection (DPI)-which displayed macroscopic surface details and presented initial clues as to the …

Synthesis Of Maleic Anhydride Grafted Polypropylene-Butadiene Copolymer And Its Application In Pp/Ommt/Sbs Composite As Compatibilizer, Qiaohuan Cheng, Zhanxia Lu, Hugh Byrne

Articles

Maleic Anhydride (MA) grafted propylene-butadiene copolymer (PPB) was prepared. FTIR and 1H-NMR results indicated that the MA molecules reacted with the double bond in the butadiene unit of the PPB and the grafting percentage increased with the butadiene content in the initial copolymer. GPC results showed the introduction of butadiene in the copolymer prevented the degradation of the PPB. The MA-g-PPB (MPPB) was applied in PP/SBS/OMMT composite as compatibilizer. In the presence of 10phr MPPB, the impact strength of the composite was improved by ~20%. XRD patterns indicated the formation of β-phase crystallization of polypropylene in the presence of MPPB …

Reconfigurable End Effector Allowing For In-Hand Manipulation Without Finger Gaiting Or Regrasping, Jacob Ames Ziesmer

Master's Theses (2009 -)

The goal of this thesis is to move a step towards the solution of the bin picking problem. A novel metamorphic end effector is proposed, tested for proof of concept and analyzed using standard techniques of degrees of freedom and graph theory as well as a classical dynamic analysis. Once proof of concept was achieved, the results from the analysis were formed into an optimization program with the hope of finding a more stable, predictable mechanism.

Development Of A Velocity Metric For Rigid-Body Planar Motion, Luis Ernesto Criales Escobar

Master's Theses (2009 -)

Two motions of motion quality have been developed for planar motion. They are the "best motion measure" and the "velocity metric". The "best motion measure" identifies the best motion for a given displacement. The "velocity metric" quantifies the discrepancy between two planar motions for the same rigid body.

The best motion measure compares the motion of each particle on the body to an "ideal", but usually unobtainable, motion. This ideal motion moves each particle from its current position to its desired position on a straight-line path. Although the ideal motion is not a valid rigid body motion, this does not …

Mesoscale Behavior Of An Aluminum-Manganese Dioxide-Epoxy Mixture Under Shock Loading: From Milli To Nano-Sized Aluminum Particles, Andrew Fraser

Master's Theses (2009 -)

The main focus of this thesis is to explore the dynamic shock compaction of multiple component mixtures, specifically Al-MnO₂-Epoxy. This will be facilitated by initially simulating the bulk dynamic response in a mesoscale configuration and then comparing these results to experimental data. The mesoscale simulations were performed in the shock code CTH. The first section will discuss the matching of experimental data to computational results. With the goal of determining the bulk shock Hugoniot, a one-dimensional flyer plate configuration was created while using a grain-geometry imported from an scanning electron microscope (SEM) micrograph of the mixture. Both the …

Capillary Perfusion Kinematics In Lungs Of Oxygen-Tolerant Rats, Madhavi Ramakrishna

Master's Theses (2009 -)

Motivation:

Prolonged exposure to oxygen at high concentrations (hyperoxia), a common treatment for hypoxemia, is toxic to the lungs. Rats exposed to 85% O₂ for 5-7 days develop tolerance to the otherwise lethal effects of 100% O₂. Elucidating the factors that contribute to this tolerance could further our understanding of the mechanisms of lung O₂ toxicity. Since vascular remodeling involving loss of capillary volume and endothelial surface area has been reported in lungs from rats exposed to 85% O₂ for 7 days, we were interested in evaluating the effect of this hyperoxia model on lung …

Eeg During Pedaling: Brain Activity During A Locomotion-Like Task In Humans, Sanket G. Jain

Master's Theses (2009 -)

This study characterized the brain electrical activity during pedaling, a locomotor-like task, in humans. We postulated that phasic brain activity would be associated with active pedaling, consistent with a cortical role in locomotor tasks. 64 channels of electroencephalogram (EEG) and 10 channels of electromyogram (EMG) data were recorded from 10 neurologically-intact volunteers while they performed active and passive (no effort) pedaling on a custom-designed stationary bicycle. Ensemble average waveforms, two dimensional topographic maps and amplitude of the beta (13-35 Hz) frequency band were analyzed and compared between active and passive trials. The absolute amplitude (peak positive-peak negative) of the EEG …

Characterization Of The Electromagnetic Fields Inside A Wire Mesh Cage For Biotelemetry, Johnny Bernard Lienau

Master's Theses (2009 -)

A wire mesh cage composed of thin conductive wires will influence the behavior of electromagnetic fields within it. Theory suggests that the cage will behave like a low Q cavity. Many researchers have investigated electromagnetic field behavior in solid walled cavities and waveguides, but little of this work has probed into the effects of a wire mesh. Additionally, few studies have investigated RF communication in these types of environments. The primary goal of this work is to research wireless communication inside a low Q wire mesh cavity in the 200-700 MHz range. Through simulated and experimental results, ideal antenna locations …

The Effect Of Office Chair Backrest Design On The Body's Metabolic Response To Office Work, Stephen H. Freier

Master's Theses (2009 -)

Most office chairs have a backrest that is wider at the shoulders than at the hips. Recently, a new office chair was developed that has a backrest that is narrower at the shoulders and wider at the hips (upwardly tapered backrest). The upwardly tapered backrest should allow users to increase their ventilatory efficiency, compared to a conventional, wide backrest. This new backrest design will hypothetically allow a user to retract their scapulae, increase expansion of the chest cavity, thus allowing the lungs more space to expand. Specific measures of improved ventilatory efficiency are an increase in tidal volume (V_{t …}

Time-Optimal Control Of Discrete-Time Systems With Known Waveform Disturbances, Jennifer Lynn Riffer

Master's Theses (2009 -)

In this thesis, a discrete-time observer based disturbance accommodation controller is designed that is capable of minimizing the effect of disturbances with known waveform in both the system state and measurement as fast as possible while also driving the state to zero. This control is achieved by designing a single control input to accommodate disturbances in both the system state and measurement. For controller design, the state and measurement equations are augmented, and a least squares minimization technique is used to find a control input that drives the system state and measurement to zero, guaranteeing deadbeat response. During the design …

A Mixed-Dimensionality Modeling Approach For Interaction Of Heterogeneous Steam Reforming Reactions And Heat Transfer, Jeroen Valensa

Master's Theses (2009 -)

Hydrogen is most often produced on an industrial scale by catalytic steam methane reforming, an equilibrium-limited, highly endothermic process requiring the substantial addition of heat at elevated temperatures. The extent of reaction, or conversion efficiency, of this process is known to be heat transfer limited. Scaling the industrial process equipment down to the size required for small, compact fuel cell systems has encountered difficulties due to increased heat losses at smaller scales. One promising approach to effectively scale down the reforming process is to coat the catalyst directly onto the heat exchange surfaces of an integrated reactor/heat exchanger. In this …

Development And Implementation Of Novel Bristle Tool For Surface Treatment Of Metallic Components, Piyush Khullar

Master's Theses (2009 -)

Despite advances in paints and coatings technology, protective coatings are prone to eventual corrosion, degradation and/or failure. Consequently, a corrosive layer will develop that can undermine the performance and integrity of structural components. Therefore, both the corrosive layer and defunct coating must be periodically removed, and an acceptable level of surface cleanliness and texture must be obtained prior to the reapplication of new paint. Currently, an array of processes and equipment are used for efficiently cleaning and conditioning metallic surfaces, such as grit blasting, needle guns, and a variety of non-woven and coated abrasive tools.

This research investigates the method …

Systems Identification Of Sensorimotor Control For Visually Guided Wrist Movements, Chintan Poladia

Master's Theses (2009 -)

The sensorimotor control system is a complicated system in which the neural controller uses the feedback information from sensory modalities (visual, proprioceptive, vestibular, auditory, etc.) to actuate the musculo-skeletal system in order to execute intended movements. It has been an ongoing research to decode this sensorimotor integration. The current study utilized a systems identification approach in conjunction with a one-degree-of-freedom robotic manipulandum to quantify (delays, noises, wrist dynamics and controller parameters) a simplified (linear time-invariant) model of sensorimotor control for visually guided wrist stabilization movements.

Four sensorimotor tasks were used to characterize the parameters of the sensorimotor control model. Open …

Observed Superspin-Glass Behavior In Ni0.5zn0.5fe2o4 Nanoparticles, Antony Adair

Open Access Theses & Dissertations

In this investigation we seek to identify the magnetic behavior of Ni0.5Zn0.5Fe2O4 nanoparticles though AC-susceptibility and DC-magnetization measurements. Powder x-ray diffraction was performed to determine the purity and average diameter ( ~ 9nm) of the particles. Aditionally, structure was confirmed by comparison through the International Centre for Diffraction Data's Powder Diffraction File [52] (PDF # 08-0234).

Zero-field cooled and field cooled DC magnetization measurements (bifurcation and blocking temperature), as well as M(H) hysteresis (below and above the blocking temperature) lead us to initially suggest that the material may in fact be superparamagnetic. However, further investigation of the real AC susceptibility …

Application Of Sensor Fusion To Human Locomotor System, John Kweku Avor

Open Access Theses & Dissertations

This research study proposes a multi-sensor data fusion technique to determine the complex interactions between the sensory, muscular and mechanical components of the human locomotor systems (neuromechanics). The object in this work is to demonstrate the viability in using inertial sensors for accurate gait phase determination and to present the acceleration effect specific body segment contributes in order to establish a functional gait. The current method used in determining gait phases consist of combining ground reaction force and angular data, this method is time consuming and cannot be totally reliable. We found out that gait phases can be determined distinctively …