Mechanical Engineering Commons^™

Development Of An Electro-Centrifugal Spinning Setup For Nanofiber Production Research, David A. Treviño

Theses and Dissertations

Nanofiber production methods have been developed and improved over the course of decades. Each process allows for the creation of fibers with distinct properties that provide benefits to growing number of applications. On the same note, every process has shortcomings that keep them from being universally valid for all applications. This research considers electrospinning and centrifugal spinning systems and attempts to create a process which maintains high fiber qualities like small and consistent fiber diameters, and improved fiber alignment while providing a high fiber yield. The electro-centrifugal (EC) spinning machine that resulted was designed utilizing computer aided design (CAD) software …

Feasibility Analysis Of Embedding Optical Fiber Sensor Into Additively Manufactured Part, Mahmudul Hasan Porag

Theses and Dissertations

The research tried to examine the viability of the embedment of optical fiber sensors in Additively built components, packaging the sensors within the components, and characterizing the sensors for sensing a specified measurement. Optical fiber sensors are popular due to their small size, resilience against electromagnetic radiation, and reliability in potentially dangerous conditions. Embedding fibers inside a product allows for the monitoring of critical areas, allowing for preemptive action in the case of a breakdown. Coupons of Inconel 718 were made using laser powder-bed fusion (LPBF), with the fabrication settings tuned to determine whether such a development was possible. After …

Mechanics Modeling Of Non-Rigid Origami: From Qualitative To Quantitative Accuracy, Jiayue Tao

All Dissertations

Origami, the ancient art of paper folding, has recently evolved into a design and fabrication framework for various engineering systems at vastly different scales: from large-scale deployable airframes to mesoscale biomedical devices to small-scale DNA machines. The increasingly diverse applications of origami require a better understanding of the fundamental mechanics and dynamics induced by folding. Therefore, formulating a high-fidelity simulation model for origami is crucial, especially when large amplitude deformation/rotation exists during folding.

The currently available origami simulation models can be categorized into three branches: rigid-facet models, bar-hinge models, and finite element models. The first branch of models assumes that …

Infusing Kirigami Principles Into Design Of Mechanical Properties, Hesameddin Khosravi

All Dissertations

The emergence of mechanical metamaterials — which derive their properties primarily from the underlying architecture rather than the constituent material — has unleashed a new era of material design and functionalities. To fully materialize the promising potentials of metamaterials, it is crucial to develop versatile, scalable, and easy-to-fabricate methods that can both generate and tailor the underlying periodic architecture. To this end, we propose the use of kirigami — a popular recreational art of cutting and manipulating paper — as a platform to create periodicity and super-stretchability. Kirigami has become a design and fabrication framework for constructing metamaterials, robotic tools, …

Direct Ink Write And Thermomechanical Characterization Of Thermoset Composites, Sergio Dante Favela

Open Access Theses & Dissertations

This research will be divided into two sections. The first section discusses direct ink writing and thermomechanical characterization for thermoset composites. The thermoset ink is prepared with fillers aiding the printing process by modifying the rheology of the ink and geometry retention by allowing for the part to have an initial UV cure step. Three specimen formulations with different weight percentages were printed by material extrusion in the shape of tensile specimens following ASTM standard D638 to characterize the mechanical properties at room temperature, 100â?? and 200â??. Furthermore, the ink resin was characterized through DSC, TGA, and rheology testing. The …

Synthetic Data Generation For Intelligent Inspection Of Structural Environments, Noshin Habib

Open Access Theses & Dissertations

Automated detection of cracks and corrosion in pavements and industrial settings is essential to a cost-effective approach to maintenance. Deep learning has paved the path for vast levels of improvement in the area. Such models require a plethora of data with accurate ground truth and enough variation for the model to generalize to the data, which is notwidely available. There has been recent progress in computer graphics being used for the creation of synthetic data to address the issue of deficient data availability, but it is limited to specific objects, such as cars and human beings. Textures and deformities within …

High-Temperature Valve Design For A Solid Oxide Fuel Cell/Gas Turbine Hybrid System Utilizing Smart Materials, Alba Jazmin Leyva

Open Access Theses & Dissertations

The topic of this project includes extensive research on the Solid Oxide Fuel Cell Gas Turbine (SOFC/GT) hybrid system located at the National Energy Technology Laboratory. The goal is to reduce pollution and generate energy by using natural gas and a combination of fuel cells, heat exchangers, bypass valves, turbines, and combustors as components working together to produce clean energy. The SOFC/GT system works by having the fuel cell pressurized by the gas turbine. The turbine then produces exhaust gas for the fuel cell, because the turbine recovers the majority of the heat and the pressurization contributes to the enhancement …

Fabrication, Microstructure And Mechanical Characterization Of Crvnbtaw High Entropy Alloy Coatings Using Magnetron Sputtering, Jorge Quezada

Open Access Theses & Dissertations

In this project a CrVNbTaW high entropy alloy was evaluated. The samples were made using radio frequency magnetron sputtering and were made under similar conditions. The deposition parameters were explored to find the ideal deposition process. The process included a pressure from 0.1-2mTorr, 600C, 1 hour duration, at 100W power to guns, and constant argon flow. The samples were fabricated under similar parameters using silicon steel and sapphire substrates. The samples were analyzed and characterized using X-ray diffraction, scanning electron microscopy, atomic force microscopy, nanoindentation and corrosion testing. Based on these results we were able to get a better understanding …

Fabrication And Characterization Of Iron-Based Catalysts For The Dehydrogenation Of Fossil Fuels, Victoria Isabel Reyes

Open Access Theses & Dissertations

For a prosperous and sustainable future, hydrogen is an encouraging solution due to its simple transition for industrial decarbonization and synergy for economic development. Paradoxically, current hydrogen production pathways release substantial amount of greenhouse gases into the atmosphere contributing to climate change. To keep up with increasing demand, hydrogen could be produced through microwave-assisted thermocatalytic dehydrogenation of fossil fuels without emitting carbon dioxide. This requires specified catalysts to meet the requirements of hydrogen yield and selectivity. The objective of the present research is to fabricate, characterize, and compare iron-based alumina (FeAl_x O_y) catalysts produced via solution combustion synthesis and iron-based …

Analysis Of Propeller Designs Focusing On Lowering Sound Pressure Level Through Reduced Tip Loading, Luca A. Zeitvogel

Theses and Dissertations

This research focused on potential design optimizations for small propellers. Designs sought to reduce noise generated without sacrificing efficiency by “unloading” the propeller tip by reducing angle of attack near the tip. To see if nearfield performance improvements translated to a reduction in farfield sound pressure level, farfield experimental acoustic testing was performed on propellers that had been measured experimentally in the nearfield. The farfield results provided limited insight due to an equipment malfunction during testing. However, a large data set was obtained, which provides opportunities for future analyses. A computational simulation sought to recreate some of the nearfield experiments …

Modeling, Control And Estimation Of Reconfigurable Cable Driven Parallel Robots, Adhiti Raman Thothathri

All Dissertations

The motivation for this thesis was to develop a cable-driven parallel robot (CDPR) as part of a two-part robotic device for concrete 3D printing. This research addresses specific research questions in this domain, chiefly, to present advantages offered by the addition of kinematic redundancies to CDPRs. Due to the natural actuation redundancy present in a fully constrained CDPR, the addition of internal mobility offers complex challenges in modeling and control that are not often encountered in literature.

This work presents a systematic analysis of modeling such kinematic redundancies through the application of reciprocal screw theory (RST) and Lie algebra while …

Multiple Heat Exchanger Cooling System For Automotive Applications – Design, Mathematical Modeling, And Experimental Observations, Zaker Syed

All Dissertations

The design of the automotive cooling systems has slowly evolved from engine-driven mechanical to computer-controlled electro-mechanical components. With the addition of computer-controlled variable speed actuators, cooling system architectures have been updated to maximize performance and efficiency. By switching from one large radiator to multiple smaller radiators with individual flow control valves, the heat rejection requirements may be precisely adjusted. The combination of computer regulated thermal management system should reduce power consumption while satisfying temperature control objectives. This research focuses on developing and analyzing a multi-radiator system architecture for implementation in ground transportation applications. The premise is to use a single …

Development And Characterization Of Forcespinning® Mesquite Gum Nanofibers, Cristobal Rodriguez, Victoria Padilla, Karen Lozano, Alexa Villarreal, Luis A. Materon, Robert Gilkerson

Mechanical Engineering Faculty Publications

In this study, nanofibers incorporating Prosopis glandulosa mesquite gum (MG) exudate combined with biodegradable polymers, pullulan (PL) and chitosan (CH), were produced via the Forcespinning® technique. The nonwoven composite membranes were characterized via scanning electron microscopy followed by thermogravimetric and Fourier-transform infrared spectroscopy analysis. MG nanofiber composites comprised long, continuous fibers with an average fiber diameter of 523 ± 180 nm and 760 ± 225 nm for 18.1 and 28 wt% of MG, respectively. These composite membranes were water-stable after crosslinking via heat treatment with a ∼3 % water absorption capacity, and demonstrated a thermal capability with an increasing …

Assembly Of Ceramic Particles In Aqueous Suspensions Induced By High-Frequency Ac Electric Field, James E. John Iv

Mechanical & Aerospace Engineering Theses & Dissertations

Ceramic materials processed using colloidal methods have been the focus of a great deal of research aimed at tailoring the final structure and microstructure of the finished ceramic sample. To this end, various external field effects have been investigated to modify the suspension microstructure without manipulating the ceramic particles directly. In a previous work in the field of ice templating it has been shown that AC electric fields are able to produce microstructural changes in ice templated ceramics that have significantly improved the final mechanical properties. However, the mechanisms for this process are still not well understood in ceramics.

To …

Dynamic Surface Tension Of Surfactants Through Separation Of Diffusion And Dilation Effects, Brandon Ortiz

UNLV Theses, Dissertations, Professional Papers, and Capstones

Surfactants are biphilic monomers that adsorb to interfaces and have the ability to reduce interfacial tension. From this reduction in interfacial tension, surfactants are able to function as emulsifiers, detergents, and wetting agents among a variety of other things. Despite their ubiquity surfactants and surfactant behaviors, in particular those in highly dynamic environments, are not yet well characterized. In these environments, surfactants undergo significant distortions to droplet, bubble, and foam geometries which induce changes to the surface tension. This establishes a need to understand how surfactants respond to distortions of geometry through diffusion and dilational effects. To address this need, …

Mechanoelectrical Behavior In Polyvinyl Chloride (Pvc) Based Soft Polymer Gel Smart Sensors For Soft Robotic Applications, Justin Neubauer

UNLV Theses, Dissertations, Professional Papers, and Capstones

Polyvinyl chloride (PVC) gels are a class of electroactive polymer that contain a PVC-based polymeric lattice and various amounts of plasticizer. PVC and plasticizer are industrially available and are commonly used in a wide range of applications including cable insulation, flexible hosing, and healthcare equipment. There are many plasticizer types available, some being extremely biocompatible with implementations in food-safe applications and even food additives for human consumption. Plasticizer weakly bonds to the long polymerized chains of the polymer lattice decreasing the modulus of the composite material. By adding excessive amounts of plasticizer, the bonding sites of these long carbon chains …

Tympanostomy Tubes In Children: A Fem Study Of Adverse Effects, Manuel Nicolas Jaramillo Bucheli

Theses and Dissertations

Background: The current study investigates if tympanic (myringotomy) tubes affect hearing by comparing the harmonic displacement response to sound excitation within the hearing frequency range for healthy vs. surgically-treated pediatric tympanic membranes. The use of ear myringotomy tubes has proven an effective method for combating recurrent ear infections in infants and children. These tubes are placed in the tympanic membrane through an incision and connect the middle ear to the external ear, thereby allowing fluid drainage and middle-ear ventilation. While this treatment has been proven beneficial in alleviating urgent pus accumulation in the middle ear, recent research shows that it …

High Throughput And Highly Controllable Methods For In Vitro Intracellular Delivery, Justin Brooks, Grayson Minnick, Prithvijit Mukherjee, Arian Jaberi, Lingqian Chang, Horacio D. Espinosa, Ruiguo Yang

Department of Mechanical and Materials Engineering: Faculty Publications

In vitro and ex vivo intracellular delivery methods hold the key for releasing the full potential of tissue engineering, drug development, and many other applications. In recent years, there has been significant progress in the design and implementation of intracellular delivery systems capable of delivery at the same scale as viral transfection and bulk electroporation but offering fewer adverse outcomes. This review strives to examine a variety of methods for in vitro and ex vivo intracellular delivery such as flow-through microfluidics, engineered substrates, and automated probe-based systems from the perspective of throughput and control. Special attention is paid to a …

Measurement Of Low-Speed Impinging Jet Structure Using Temperature Sensitive Paint, Arthur Dean Woodworth

Masters Theses

Temperature sensitive paint (TSP) is used to analyze surface flow structures driven by a jet impinging on a heated steel sheet. Temperature and Nusselt number images are calculated from CCD images of the TSP surface. TSP calibration is discussed. Skin friction data is obtained from the temperature images.

Data is collected for metal and 3D-printed plastic nozzles of varying shape and size at one or two jet airspeeds depending on the nozzle. For the circular nozzles, data is collected for four Reynolds numbers at impinging angles of 90, 70, and 50 degrees. For the elliptical nozzles and the star-shaped nozzle, …

Ultrasound Mediated Tissue Growth In Bioinspired Scaffolds, Marco Fielder

Graduate Theses and Dissertations

Porous scaffolds mechanically stimulated with ultrasound are used for the treatment of bone conditions such as osteoporosis or traumatic bone injury. However, one current issue in these treatment techniques is designing a scaffold structure with a high structural integrity that also does not impede tissue growth. A larger ultrasound wave transmission would also allow more of a scaffold to receive mechanical stimulation from ultrasound. Controlling mesenchymal stem cell seeding of tissue scaffolds also has potential for developing optimal seeding patterns to maximize or control tissue growth in the scaffold based on an individual’s physiology. There is also a need for …

Thermal Design And Energy Analysis Of A Greenhouse In Microgravity Conditions, Nivedha Karigiri Madhusudhan

Theses and Dissertations

The recent progress in commercial space flights and prospects for interplanetary space missions has attracted more attention towards developing sustainable built environments in microgravity conditions. An important factor in establishing a sustainable living condition for outer space applications is the ability to produce food. The thermal design considerations in a greenhouse have a major impact on the survival, water efficiency, quantity, and quality of plants produced. The extremely low environmental temperatures necessitate the use of heaters which do consume energy. Given the scarcity of energy access, it is important to achieve proper thermal conditions with the lowest possible energy requirements. …

Numerical Simulation Of Electroosmotic Flow Of Viscoelastic Fluid In Microchannel, Jianyu Ji

Mechanical & Aerospace Engineering Theses & Dissertations

Electroosmotic flow (EOF) has been widely used in various biochemical microfluidic applications, many of which often involve the use of viscoelastic non-Newtonian fluids. Due to the existence of the elastic effect, the viscoelastic EOF develops into chaotic flow under extremely low Reynolds numbers, which is known as elastic turbulence. The mechanism of elastic turbulence in electroosmotic flow remains unclear. Numerical simulation plays an important role in understanding the mechanisms of elastic turbulence. This dissertation is aimed to study the EOF of viscoelastic fluids in constriction microchannels under various direct current (DC) and alternating current (AC) electric fields. First, the EOF …

Framework For The Utilization Of The Agile Methodology In Engineering Consulting Services, Cristian Daniel Nuñez

Theses and Dissertations

The guidelines that form the Agile methodology framework are developed and adapted to the engineering consulting services industry. Four tools recommended by the literature are developed and adapted for the specific case of this industry. The implementation of the use of these tools is intended to help adopt the Agile methodology more effectively. A company that performs consulting services for airports is taken as a case study. This company did not officially implement the Agile methodology at the time this research has been done. The data is obtained through a survey designed to associate the company's activities with the guides …

Design And Optimization Of High-Power Density Permanent Magnet Motor With Integrated Cooling For Aircraft Propulsion, Aravindakshan Thirumalai Ananthanpillai

Theses and Dissertations

There is a critical need for the electrification of transportation systems. While power density required for ground-based vehicles can, to some extent, be met by current off-the-shelf motors and generators, aircrafts require significant improvements both in terms of power density and efficiency. The concept relies on the tight integration of a high-power density dual-rotor permanent magnet motor, high power density SiC power converters, and a shared closed loop cooling system rejecting the heat in the propulsion ducted fan air stream. The motor is based on a dual-rotor configuration using permanent magnets forming ideal Halbach arrays allowing for high magnetic loading …

The Effect Of Zonation, Biofouling, And Corrosion Products On Cathodic Protection Design For Offshore Monopiles, Caglar Erdogan

Theses and Dissertations

Cathodic protection (CP) is required to prevent corrosion of the submerged steel for offshore wind monopile foundations in the marine environment. The design of these systems depends on the environmental conditions, including temperature, salinity, pH, dissolved oxygen, depth, micro- and macro-organisms, and water flow rates. The standards utilized to design cathodic protection systems consider only some of these conditions. This research identified the gaps in knowledge for the design of corrosion prevention systems for offshore wind monopile foundations and investigated the changes in cathodic current densities due to macro-galvanic cells, fouling communities and corrosion products established on uncoated vertical steel …

Study On The Spatiotemporal Dynamic Of Ground-Level Ozone Concentrations On Multiple Scales Across China During The Blue Sky Protection Campaign, Haoji Wu, Lin Pei, Xiaowei Zhu, Bin Guo, Dingming Zhang, Multiple Additional Authors

Mechanical and Materials Engineering Faculty Publications and Presentations

Surface ozone (O3), one of the harmful air pollutants, generated significantly negative effects on human health and plants. Existing O3 datasets with coarse spatiotemporal resolution and limited coverage, and the uncertainties of O3 influential factors seriously restrain related epidemiology and air pollution studies. To tackle above issues, we proposed a novel scheme to estimate daily O3 concentrations on a fine grid scale (1 km × 1 km) from 2018 to 2020 across China based on machine learning methods using hourly observed ground-level pollutant concentrations data, meteorological data, satellite data, and auxiliary data including digital elevation model (DEM), land use …

Evaluation And Implementation Of Lean Engineering Principles For Improving A University Rocket Team, Alan Garcia

Open Access Theses & Dissertations

In the present day, lean is a tool applied to manufacturing industries trying to reduce wasteand non-value-added work to every process during the supply chain. While implementing lean thinking in the industry has been highly effective, it is less common for academic purposes. However, it can also improve performance if the concept is correctly applied. The purpose of this thesis is to show and analyze the application of Lean Engineering thinking and its six principles to the Sun City Summit Rocket Team from the University of Texas at El Paso which competed in the Intercollegiate Rocket Engineering Competition (IREC) Spaceport …

Fabrication And Characterization Of Germanium Functionalized Porous Nickel Oxide Electrodes For Application In Supercapacitors, Cristina Gonzalez

Open Access Theses & Dissertations

Limited fossil fuel, increasing population, pollution, and climate change are motivating society to use renewable and clean energy techniques. However, the intermittent nature of renewable sources hinders their continuous availability and use. Energy storage devices such as supercapacitors and batteries are essential for sustainable development but their high cost limits its bulk use. The cost of energy storage devices mainly depends on materials, synthesis process and device fabrication. Therefore, low cost 3-D mesoporous nickel germanium fictionalize nickel oxides electrode materials has been developed by using facile fabrication techniques for supercapacitor application. 3-D mesoporous nickel provides the high surface area and …

The Qualification Of Sealability And Creep Relaxation Of Additively Manufactured Zytel Gaskets For Pem Fuel Cells, Robert Lazarin

Open Access Theses & Dissertations

The purpose of this thesis is to study the feasibility of low-cost additive manufacturing of gaskets for proton exchange membrane fuel cells exposed to extreme temperature conditions ranging from -55°C to 100°C. With the growing popularity and decreasing costs of additive manufacturing technologies, specifically Material Extrusion (ME), research is being conducted to determine the feasibility of ME components. Thermally cycled PEMFCs may exhibit accelerated gasket deterioration, therefore, the mechanical stability of material extruded gaskets following a harsh thermal cycle must be assessed. The feasibility of the material extruded gaskets will be proven by manufacturing optimization and mechanical testing. The target …

Novel Interlaminar Reinforcement To Enhance The Impact Damage Resistance Of Carbon Fiber-Reinforced Polymer Matrix Composites, Daisy Haidee Mariscal

Open Access Theses & Dissertations

Aerospace, aircraft, marine, and automobile applications are increasingly using composite materials for lighter, higher stiffness, and strength properties. Despite these advantages, composite materials have one major disadvantage. The through-thickness properties are extremely weak when subjected to impact damage. When a composite material is subjected to a low-velocity impact, there is hardly any visible damage on the surface compromising the composite material internally without any external notice. Internal damage may be delamination, which is the most common, matrix cracking, and fiber breakage. A composite material is made up of layers of fiber. The interlaminar region is located in between these layers. …