Engineering Commons^™

Towards A Cyber-Physical Manufacturing Cloud Through Operable Digital Twins And Virtual Production Lines, Md Rakib Shahriar

Graduate Theses and Dissertations

In last decade, the paradigm of Cyber-Physical Systems (CPS) has integrated industrial manufacturing systems with Cloud Computing technologies for Cloud Manufacturing. Up to 2015, there were many CPS-based manufacturing systems that collected real-time machining data to perform remote monitoring, prognostics and health management, and predictive maintenance. However, these CPS-integrated and network ready machines were not directly connected to the elements of Cloud Manufacturing and required human-in-the-loop. Addressing this gap, we introduced a new paradigm of Cyber-Physical Manufacturing Cloud (CPMC) that bridges a gap between physical machines and virtual space in 2017. CPMC virtualizes machine tools in cloud through web services …

Exploring Convergence Of Snake Skin-Inspired Texture Designs And Additive Manufacturing For Mechanical Traction, Catherine Sue Tiner

Graduate Theses and Dissertations

This research focuses on the understanding, development, and additive manufacture of a 3D printed snake skin-inspired texture pattern. The design functionalities of snake skin were determined through the study of the snake species Python Regius otherwise known as the ball python. Each scale of a snake has hierarchical texture with hexagonal macro-patterns aligned on the ventral surface of the skin with overriding anisotropic micro textured patterns such as denticulations and fibrils. Using a laser-powder bed fusion (L-PBF) process, 420 stainless steel samples were 3D printed which closely resemble the above described directional texture of natural snake skin. This printed surface …

Microextrusion 3d Printing Of Optical Waveguides And Microheaters, Edidiong Nseowo Udofia

Graduate Theses and Dissertations

The drive for smaller and more compact devices presents several challenges in materials and fabrication strategies. Although photolithography is a well-developed method for creating microdevices, the disparate requirements in fabrication strategies, material choices, equipment and process complexities have limited its applications. Microextrusion printing (μEP) provides a promising alternative for microfabrication. Compared to the traditional techniques, the attractions lie in the wide range of printable material choice, greater design freedom, fewer processing steps, lower cost for customized production, and the plurality of compatible substrates. However, while extrusion-based 3D printing processes have been successfully applied at the macroscale, this seeming simplicity belies …

Predicting The Mechanical Properties Of Nanocomposites Reinforced With 1-D, 2-D And 3-D Nanomaterials, Scott Edward Muller

Graduate Theses and Dissertations

Materials with features at the nanoscale can provide unique mechanical properties and increased functionality when included as part of a nanocomposite. This dissertation utilizes computational methods at multiple scales, including molecular dynamics (MD) and density functional theory (DFT), and the coupled atomistic and discrete dislocation multiscale method (CADD), to predict the mechanical properties of nanocomposites possessing nanomaterials that are either 1-D (carbyne chains), 2-D (graphene sheets), or 3-D (Al/amorphous-Si core-shell nanorod).

The MD method is used to model Ni-graphene nanocomposites. The strength of a Ni-graphene nanocomposite is found to improve by increasing the gap between the graphene sheet and a …

Fault Adaptive Workload Allocation For Complex Manufacturing Systems, Charlie B. Destefano

Graduate Theses and Dissertations

This research proposes novel fault adaptive workload allocation (FAWA) strategies for the health management of complex manufacturing systems. The primary goal of these strategies is to minimize maintenance costs and maximize production by strategically controlling when and where failures occur through condition-based workload allocation.

For complex systems that are capable of performing tasks a variety of different ways, such as an industrial robot arm that can move between locations using different joint angle configurations and path trajectories, each option, i.e. mission plan, will result in different degradation rates and life-expectancies. Consequently, this can make it difficult to predict when a …

The Role Of Inter-Particle Behavior In Iron Oxide Nanoparticle Induction Heating, Hayden Seth Carlton

Graduate Theses and Dissertations

Due to their multi-functional nature, iron oxide nanoparticles present themselves in a myriad of scientific disciplines, but perhaps the most interesting property of these nanomaterials can be seen in their immense thermal response under the influence of alternating magnetic fields. Currently popularized as an alternative cancer treatment through localized hyperthermia, iron oxide nanoparticle induction heating presents an interesting physical phenomenon that distinguishes itself from macroscopic induction heating. Understanding how a single spherical particle behaves is relatively simple and remains well documented; however, magnetic interactions of a single particle often extend over many length scales, affecting numerous neighboring particles in the …

Motor Control Systems Analysis, Design, And Optimization Strategies For A Lightweight Excavation Robot, Austin Jerold Crawford

Graduate Theses and Dissertations

This thesis entails motor control system analysis, design, and optimization for the University of Arkansas NASA Robotic Mining Competition robot. The open-loop system is to be modeled and simulated in order to achieve a desired rapid, yet smooth response to a change in input. The initial goal of this work is to find a repeatable, generalized step-by-step process that can be used to tune the gains of a PID controller for multiple different operating points. Then, sensors are to be modeled onto the robot within a feedback loop to develop an error signal and to make the control system self-corrective …

Modeling Of Complex Parts For Industrial Waterjet Cleaning, Braden James

Graduate Theses and Dissertations

Industrial high-pressure waterjet cleaning is common to many industries. The modeling in this paper functions inside a collaborative robotic framework for high mix, low volume processes where human robot collaboration is beneficial. Automation of pressure washing is desirable for economic and ergonomic reasons. An automated cleaning system needs path simulation and analysis to give the operator insight into the predicted cleaning performance of the system. In this paper, ablation, the removal of a substrate coating by waterjet, is modeled for robotic cleaning operations. The model is designed to work with complex parts often found in spray cleaning operations, namely parts …

Towards Environmentally Sustainable And Cost-Effective Food Distribution In The U.S., Jasmina Burek

Graduate Theses and Dissertations

Distribution centers (DCs) and supermarkets have an important role in food sustainability, but no previous research has accounted for their environmental impact. The purpose of this research was to assess environmental sustainability of grocery, perishables, and general merchandise DCs; to estimate food storing and retailing impact; and to provide cost-effective strategies to reduce DCs’ environmental impacts. The importance and relevance of the research is threefold: improving sustainability of DCs, food storing, and food retailing. The main method used in this research was the life cycle assessment (LCA) method. An initial study calculated environmental impacts of the Wal-Mart Stores, Inc. DCs, …

Interfacial Tailoring Of Lithium-Ion Batteries By Atomic/Molecular Layer Deposition, Qian Sun

Graduate Theses and Dissertations

Lithium-ion batteries (LIBs) are promising energy storage devices, which play significant roles in addressing problems related to fossil fuels depletion and environmental pollution. Since the 1990s, LIBs have attracted great attention for many applications. Nowadays, LIBs are dominating portable electronics, having several advantages over their forerunners, such as high voltage (3.3~4.2 V) [1,2], low self-discharge (< 5~10 %/month) [3,4], wide operation temperature (-20~60 °C) [5,6], and fast charge/discharge rate [7,8]. However, LIBs deliver an energy density of 100-220 Wh/kg in practice to date, which is far from their theoretical ones, thus hindering their further applications in electric vehicles. Additionally, LIBs have been plagued by other problems, such as intolerance to overcharge/overdischarge, low heat resistance, lithium dendrites growth, large volume change of the silicon anode, large polarization and even safety problems.

Atomic layer deposition (ALD) and molecular layer deposition (MLD) are two important techniques, both proceeding in self-limiting gas-solid reactions and exhibiting excellent capabilities for ultra-thin films, conformal coatings, and controllable growth. They can be employed to address the problems of LIBs mentioned above by …

A Generative Statistical Approach For Data Classification In A Biologically Inspired Design Tool, Marvin Manuel Arroyo Rujano

Graduate Theses and Dissertations

The objective of the research this thesis describes is to find a way to classify text-based descriptions of biological adaption to support Biologically Inspired design. Biologically inspired design is a fairly new field with ongoing research. There are different tools to assist designers and biologists in bio-inspired design. Some of the most common are BioTRIZ and AskNature. In recent years, more tools have been proposed to aid and make research in the field easier, for example, the Biologically Inspired Adaptive System Design (BIASD) tool. This tool was designed with the goal of helping designers in early design stages generate more …

The Effect Of Incorporating End-User Customization Into Additive Manufacturing Designs, Jonathan D. Ashley

Graduate Theses and Dissertations

In the realm of additive manufacturing there is an increasing trend among makers to create designs that allow for end-users to alter them prior to printing an artifact. Online design repositories have tools that facilitate the creation of such artifacts. There are currently no rules for how to create a good customizable design or a way to measure the degree of customization within a design. This work defines three types of customizations found in additive manufacturing and presents three metrics to measure the degree of customization within designs based on the three types of customization. The goal of this work …

Development Of A Rapid Fatigue Life Testing Method For Reliability Assessment Of Flip-Chip Solder Interconnects, Cody Jackson Marbut

Graduate Theses and Dissertations

The underlying physics of failure are critical in assessing the long term reliability of power packages in their intended field applications, yet traditional reliability determination methods are largely inadequate when considering thermomechanical failures. With current reliability determination methods, long test durations, high costs, and a conglomerate of concurrent reliability degrading threat factors make effective understanding of device reliability difficult and expensive. In this work, an alternative reliability testing apparatus and associated protocol was developed to address these concerns; targeting rapid testing times with minimal cost while preserving fatigue life prediction accuracy. Two test stands were fabricated to evaluate device reliability …

Comparative Study Of Power Semiconductor Devices In A Multilevel Cascaded H-Bridge Inverter, Kenneth Mordi

Graduate Theses and Dissertations

This thesis compares the performance of a nine-level transformerless cascaded H-bridge (CHB) inverter with integrated battery energy storage system (BESS) using SiC power MOSFETs and Si IGBTs. Two crucial performance drivers for inverter applications are power loss and efficiency. Both of these are investigated in this thesis. Power devices with similar voltage and current ratings are used in the same inverter topology, and the performance of each device is analyzed with respect to switching frequency and operating temperature. The loss measurements and characteristics within the inverter are discussed. The Saber® simulation software was used for the comparisons. The power MOSFET …

Intelligent Application Of Flexible Ac Transmission System Components In An Evolving Power Grid, Robert Wall

Graduate Theses and Dissertations

The world revolves around energy and the energy sector is continually transforming and evolving. The status quo has been set by governing agencies in the United States for completely reliable power. The demand for energy efficiency continually rises for multiple reasons. Technology has improved for all sectors of the power grid, including renewable energy sources, fault protection, and SMART grid technology. The addition of new energy sources has led to the decommissioning of inefficient energy sources. The implementation of new technologies and power load on a large scale, coupled with the removal of grid stabilizers has posed different challenges that …

A Numerical Investigation Of Bio-Inspired Scaffolds And Surface Textures, Yucong Gu

Graduate Theses and Dissertations

Synthetic scaffolds are widely used as implants to repair bone fracture. Without a proper design, scaffolds could pose significant health risks to the patient and fail to heal the bone properly. A good synthetic scaffold needs to have high porosity and large pore size to allow new bone cells to form on it. However, a scaffold with higher porosity and larger pore size tends to have reduced mechanical strength. Thus, it is important to find a structural design which allows the implant to have a high porosity and large pore size while retaining high strength. In this research, a 3D-printable …

Microheater Array Powder Sintering (Maps) For Printing Flexible Electronics, Nicholas Holt

Graduate Theses and Dissertations

Microheater array powder sintering (MAPS) is a novel additive manufacturing process that uses an array of microheaters to selectively sinter powder particles. MAPS shows great promise as a new method of printing flexible electronics by enabling digital curing of conductive inks on a variety of substrates. MAPS operation relies on establishing a precision air gap of a few microns between an array of microheaters, which can reach temperatures of 600°C, and a layer of conductive ink which can be deposited onto a flexible substrate. This system presents challenges, being: the fabrication of a microheater that can reach suitable temperatures in …

Fluid Phase Separation Via Nanochannel Array, John Lee

Graduate Theses and Dissertations

Microelectromechanical systems (MEMS) and nanoelectromechanical systems (NEMS) generate ideas and techniques for creating new devices at the micro/nano scale. This dissertation study designed a gas generator system utilizing nanochannels for phase separation that is useful for micro-pneumatic actuators, micro-valves, and micro-pumps. The new gas generator has the potential to be an integral part of a propulsion system for small-scale satellites. Nano/picosatellites have limited orientation capability partly due to the current limitations of microthruster devices. Development of a self-contained micro propulsion system enables dynamic orbital maneuvering of pico- and nano-class satellites.

Additionally, the new gas generator utilizes a high efficiency, green …

Effects Of Hydration And Mineralization On The Mechanical Behavior Of Collagen Fibrils, Marco Fielder

Graduate Theses and Dissertations

Bone is a composite biomaterial with a structural load-bearing function. Understanding the biomechanics of bone is important for characterizing factors such as age, trauma, or disease, and in the development of scaffolds for tissue engineering and bioinspired materials. At the nanoscale, bone is primarily composed of collagen protein, apatite crystals, and water. Though several studies have characterized nanoscale bone mechanics as the mineral content changes, the effect of water, mineral, and carbon nanotube (CNT) content and distribution in fibril gap and overlap regions is unexplored. This study used molecular dynamics to investigate the change in collagen fibril deformation mechanisms as …

Phase Transitions In Monochalcogenide Monolayers, Mehrshad Mehboudi

Graduate Theses and Dissertations

Since discovery of graphene in 2004 as a truly one-atom-thick material with extraordinary mechanical and electronic properties, researchers successfully predicted and synthesized many other two-dimensional materials such as transition metal dichalcogenides (TMDCs) and monochalcogenide monolayers (MMs). Graphene has a non-degenerate structural ground state that is key to its stability at room temperature. However, group IV monochalcogenides such as monolayers of SnSe, and GeSe have a fourfold degenerate ground state. This degeneracy in ground state can lead to structural instability, disorder, and phase transition in finite temperature. The energy that is required to overcome from one degenerate ground state to another …

Understanding The Evolution Of Surface Texture Under Boundary Lubrication, Salil T. Bapat

Graduate Theses and Dissertations

The objective of this research was to understand the evolution of surface texture under boundary/mixed lubrication (BL). Significant material/energy losses occur during BL because of direct contact between the two surfaces. Traditionally, tribofilms have been studied extensively for BL while textures have been used as a static engineering design parameter to enhance lubricant film properties. However, texture is dynamic at the tribological mating interface, where both physical and chemical interactions are continuously modulated. The evolution and the interplay between the tribofilm and texture is least studied in the literature, which is the focus of this research.

MoS2-based lubricants, known for …

Development Of Microdialysis Probes In Series Approach Toward Eliminating Microdialysis Sampling Calibration: Miniaturization Into A Pdms Microfluidic Device, Randy Espinal Cabrera

Graduate Theses and Dissertations

A new microdialysis sampling method and microfluidic device were developed in vitro. The method consisted of using up to four microdialysis sampling probes connected in series to evaluate the relative recovery (RR) of different model solutes methyl orange, fluorescein isothiocyanate (FITC)-dextran average mol. wt. 4,000 (FITC-4), FITC-10, FITC-20, and FITC-40. Different flow rates (0.8, 1.0, and 1.5 µL/min) were used to compare experimentally observed relative recoveries with theoretical estimations. With increasing the number of probes in series, the relative recovery increases and ~100% (99.7% ± 0.9%) relative recovery for methyl orange was obtained. For larger molecules such as fluorescein isothiocyanate …

Exploring Energy, Comfort, And Building Health Impacts Of Deep Setback And Normal Occupancy Smart Thermostat Implementation, Zachary Ethan Alderman

Graduate Theses and Dissertations

As smart thermostat adoption rates continue to increase, it becomes worthwhile to explore what unanticipated outcomes may result in their use. Specific attention was paid to smart thermostat impacts to deep setback and normal occupancy states in a variety of conditions while complying with the ventilation and temperature requirements of ASHRAE 90.2-2013. Custom weather models and occupancy schedules were generated to efficiently explore a combination of weather conditions, building constructions, and occupancy states. The custom modeling approach was combined with previous experimental data within the Openstudio graphics interface to the EnergyPlus building modeling engine. Results indicate smart thermostats add the …

3d Printed Pcu/Uhmwpe Polymeric Blends For Artificial Knee Meniscus, Raissa Araujo Borges

Graduate Theses and Dissertations

3D printing was used to fabricate porous artificial knee meniscus material from biocompatible polymeric blends of polycarbonate-urethane (PCU) and ultra-high-molecular-weight polyethylene (UHMWPE) to enable “weep” lubrication that mimics the native meniscus. 3D printed and molded pure PCU, as well as molded PCU and UHMWPE, were used for comparison. Preliminary printing was done to evaluate the impact of process parameters on the results. The samples were subject to a variety of rotational oscillating friction and wear tests under simulated body fluid and loading conditions to replicate the natural motion of the knee. Results show that 3D printed PCU samples yielded a …

Developing Methods Of Obtaining Quality Failure Information From Complex Systems, Oladapo Olalekan Bello

Graduate Theses and Dissertations

The complexity in most engineering systems is constantly growing due to ever-increasing technological advancements. This result in a corresponding need for methods that adequately account for the reliability of such systems based on failure information from components that make up these systems.

This dissertation presents an approach to validating qualitative function failure results from model abstraction details. The impact of the level of detail available to a system designer during conceptual stages of design is considered for failure space exploration in a complex system. Specifically, the study develops an efficient approach towards detailed function and behavior modeling required for complex …

A Spreadsheet Algorithm For Determining The Economic Feasibility Of Micro-Chp Systems In The Arkansas Manufacturing Sector, Ford R. Lewallen

Graduate Theses and Dissertations

Combined heat and power (CHP) systems are not new to the market. However, advances in technology, specifically MicroTurbines, have presented new opportunities for installations of micro-CHP units - defined as 50 kWe to 300 kWe, specifically at small- to medium-sized industrial facilities. One pressing concern is whether or not an industrial plant has a high enough process thermal load requirement to fully utilize the energy output.

This thesis will discuss simulations that were run on several actual electric and thermal load combinations, which correspond to types of manufacturing facilities commonly found in Arkansas. Analysis of the plant usage profiles will …

Deformation Behavior Of Al/A-Si Core-Shell Nanostructures, Robert Andrew Fleming

Graduate Theses and Dissertations

Al/a-Si core-shell nanostructures (CSNs), consisting of a hemispherical Al core surrounded by a hard shell of a-Si, have been shown to display unusual mechanical behavior in response to compression loading. Most notably, these nanostructures exhibit substantial deformation recovery, even when loaded much beyond the elastic limit. Nanoindentation measurements revealed a unique mechanical response characterized by discontinuous signatures in the load-displacement data. In conjunction with the indentation signatures, nearly complete deformation recovery is observed. This behavior is attributed to dislocation nucleation and annihilation events enabled by the 3-dimensional confinement of the Al core. As the core confinement is reduced, either through …

An Economic Analysis Of Residential Photovoltaic Systems With And Without Energy Storage, Rodney Moses Kizito

Graduate Theses and Dissertations

Residential photovoltaic (PV) systems serve as a source of electricity generation that is separate from the traditional utilities. Investor investment into residential PV systems provides several financial benefits such as federal tax credit incentives for installation, net metering credit from excess generated electricity added back to the grid, and savings in price per kilowatt-hour (kWh) from the PV system generation versus the increasing conventional utility price per kWh. As much benefit as stand-alone PV systems present, the incorporation of energy storage yields even greater benefits. Energy storage (ES) is capable of storing unused PV provided energy from daytime periods of …

Computer Simulation Of Pore Migration Due To Temperature Gradients In Nuclear Oxide Fuel, Ian Wayne Vance

Graduate Theses and Dissertations

A phase-field simulation model is being presented that captures the thermal-gradient-driven migration of pores in oxide fuel associated with fuel restructuring. The model utilizes a Cahn-Hilliard equation supplemented with an advection term to describe the vapor transport of fuel material through the pore interior due to gradients in vapor pressure. In addition, the model also captures changes in a migrating pores’ morphology. Simulations demonstrate that the model successfully predicts pore migration towards the hottest portion of the fuel, the centerline. The simulations also demonstrate changes in pore shape that are in agreement with previous experimental observations. Initially isotropic pores are …

Characterization Of Plastic Deformation Evolution In Single Crystal And Nanocrystalline Cu During Shock By Atomistic Simulations, Mehrdad Mirzaei Sichani

Graduate Theses and Dissertations

The objective of this dissertation is to characterize the evolution of plastic deformation mechanisms in single crystal and nanocrystalline Cu models during shock by atomistic simulations. Molecular dynamics (MD) simulations are performed for a range of particle velocities from 0.5 to 1.7 km/s and initial temperatures of 5, 300 and 600 K for single crystal models as well as particle velocities from 1.5 to 3.4 km/s for nanocrystalline models with grain diameters of 6, 11, 16 and 26 nm. For single crystal models, four different shock directions are selected, <100>, <110>, <111> and <321>, and dislocation density behind the shock wave …