Mechanical Engineering Commons^™

Influence Of Surface Modification On Corrosion And Biocompatibility Of Titanium Alloys, Zia Ur Rahman

Theses and Dissertations - UTB/UTPA

Titanium alloys enhance the quality and longevity of human life by replacing or treating various parts of the body. However, the aggressive body fluids lead to corrosion and metal ions dissolution. These ions leach to the adjacent tissues and causes adverse reactions. Surface modifications improve corrosion resistance and biological activity. In this investigation, electropolishing, magnetoelectropolishing, titanium coating and hydroxyapatite coating were carried out on commercially pure titanium (CPTi), Ti6Al4V and Ti6Al4V-ELI (Extra Low Interstitials). These surface modifications are known to affect surface chemistry, morphology, wettability, corrosion resistance and biocompatibility of these materials. In vitro cyclic potentiodynamic polarization tests were conducted …

Pvc Pipe Longevity Report: Affordability And The 100+ Year Benchmark Standard, Steven Folkman

Mechanical and Aerospace Engineering Faculty Publications

In the United States and Canada, underground water infrastructure was installed during three main time periods because of population growth in the 1800s, 1900–1945, and post 1945. Pipes made of iron constructed in each of these three eras will all start to fail at nearly the same time over the next couple of decades due to the corrosion of the iron pipes. Additionally, the life span of the materials used since the 1960's has changed. Grey cast iron pipes are no longer manufactured and the new ductile iron material has been made thinner to reduce costs, but as a result, …

Numerical Analysis Of The Extrusion Of Fiber Optic And Photonic Crystal Fiber Preforms Near The Glass Transition Temperature, Mohamed Trabelssi

All Dissertations

Conventional clad core fiber optic technology has relied on a concentric structure of glass of different refraction indices. These conventional fibers suffer from constraints and limitations related to thermal expansion compatibility between the core and the glass. The new fiber technology broadly characterized as Microstructured Optic Fibers (MOFs) is intended to lift the limitations of conventional clad core fibers and also extend the range of application of fiber optics. Photonic Cristal Fibers(PCFs) are a special family of Microstructured Optic Fibers characterized by the presence of holes in the cross section of the fiber that are organized in a hexagonal pattern. …

Design Optimization Of A Composite Wing Box For High-Altitude Long-Endurance Aircraft, Philip T. Arévalo

Doctoral Dissertations and Master's Theses

A design optimization process is developed to define the wing box structure for High-Altitude Long-Endurance Aircraft (HALE). The goal of this study is to determine the best tradeoff between mass and rigidity of a HALE aircraft wing structure. A preliminary composite laminate structural design procedure is described which uses a NASTRAN-based Finite Element Analysis (FEA), and the Hierarchical Evolutionary Engineering Design System (HEEDS) MDO software to define a locus of acceptable, optimized wing box design definitions.

Damage Stability Of Inland Towboats, Kyle Stephen Tyson

Senior Honors Theses

The focus of this report is to investigate whether a towboat would be able meet damaged stability requirements. In order to evaluate what type of damage stability requirements could be considered, two damage stability criteria were selected for this investigation: Offshore Supply Vessel and Passenger Vessel Damage Criteria. Two vessels are then evaluated using General Hydrostatic Software (GHS) to find the maximum allowable vertical center of gravity allowed by each set of criteria. These values are then compared to the vessels’ operating conditions to show if the vessels would currently be able to operate. Ultimately it is found that the …

Manufacture And Characterization Of Silver And Copper Nanostructures Produced Via Forcespun Nylon 6 Nanofibers, Wenqian Zhao

Theses and Dissertations - UTB/UTPA

Nylon 6 nanofibers were produced using the Forcespinning® method and were deposited with silver or copper thin films using the high vacuum thermal evaporation technique for surface functionalization of nanostructures. The changes in surface composition, morphology and surface energy of native and metallic coated Nylon 6 nanofibers were examined. Their antibacterial properties of native, silver or copper coated Nylon 6 nanofibers were tested. Furthermore, the Nylon 6 nanofibers were used as templates in order to obtain silver or copper nanotubes where the polymer was removed after high temperature calcination. The metallic coated Nylon 6 nanofibers and metallic nanotubes morphology and …

Asymmetric Unilateral Transfemoral Prosthetic Simulator, Tyagi Ramakrishnan

USF Tampa Graduate Theses and Dissertations

amputation, which includes reduced force generation at the knee and ankle, reduced control of the leg, and different mass properties relative to their intact leg. The physical change in the prosthetic leg leads to gait asymmetries that include spatial, temporal, or force differences. This altered gait can lead to an increase in energy consumption and pain due to compensating forces and torques. The asymmetric prosthesis demonstrated in this research aims to find a balance between the different types of asymmetries to provide a gait that is more symmetric and to make it overall easier for an amputee to walk.

Previous …

An Experimental Study Of Bio-Inspired Force Generation By Unsteady Flow Features, Wesley N. Fassmann

Theses and Dissertations

As the understanding of the workings of the biological world expands, biomimetic designs increasingly move into the focus of engineering research studies. For this thesis, two studiesinvolving leading edge vortex generation for lift production as observed in nature were explored intheir respective flow regimes. The first study focused on the steady state analysis of streamwise vortices generated byleading edge tubercles of an adult humpback whale flipper. A realistic scaled model of a humpbackflipper was fabricated based on the 3D reconstruction from a sequence of 18 images taken whilecircumscribing an excised flipper of a beached humpback whale. Two complementary modelswith smooth …

Bridging The Nano- And Macro-Worlds: Thermal Property Measurement Using Thermal Microscopy And Photothermal Radiometry – Application To Particle-Irradiation Damage Profile In Zirconium Carbide, Colby Bruce Jensen

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Multiscaled experimental investigations of heat transfer from nanoscales to macroscales are requisite to progress in energy technologies. In nuclear applications, material properties can undergo significant alteration due to destructive interaction with irradiating particles at microstructural levels that affect bulk properties. This study expands the current knowledge base regarding thermal transport in ion-irradiated materials through the use of a multiscaled experimental approach using four complementary thermal wave methods. For the first time, the in-depth thermal conductivity profile of an ion-irradiated sample is measured directly.

Global Evaluation Of Biofuel Potential From Microalgae, Jeffrey W. Moody

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The objective of the proposed work is to determine the productivity potential of microalgae around the world based on the current large uncertainty of the productivity
potential found in literature. To achieve this objective, a validated thermal and biological growth model was utilized coupled with weather data files from weather stations around the world. This enabled a realistic assessment of the productivity potential based on actual climatic variables. Sensitivity of microalgae lipid productivity to biomass production, temperature, and variability was performed illustrating the importance of biological and temporal resolution. Results from modeling work were leveraged for a scalability assessment based …

Retrofitting Two Solar Hot Water Systems For Year Round Operation, Zachary A. Cook

All Graduate Plan B and other Reports, Spring 1920 to Spring 2023

Solar energy in a variety of applications is again becoming more widely used. Solar collectors have been installed during the construction of two Utah State University buildings: Wetlands Discovery located in Kaysville, Utah and Swaner Nature Preserve located in Park City, Utah. While these systems are capable of capturing a significant amount of solar energy, problems have been encountered when the demand is less than the system’s capacity. This project report documents the problems encountered while operating the two solar water heating systems and how the systems were modified to be operational year round under typical operating conditions. The peak …

Nanostructured Transition Metal Oxides For Energy Storage And Conversion, Qiang Li

Theses and Dissertations - UTB/UTPA

The conventional film configuration of electrochemical electrodes hardly fulfills the high energy and efficiency requirements because heavy electroactive material deposition restricts ion diffusion path, and lowers power density and fault tolerance. In this thesis, I demonstrate that novel nanoarchitectured transition metal oxides (TMOs), e.g. MnO2, V2O5, and ZnO, and their relevant nanocomposites were designed, fabricated and assembled into devices to deliver superior electrochemical performances such as high energy and power densities, and rate capacity. These improvements could be attributed to the significant enhancement of surface area, shortened ion diffusion distances and facile penetration of electrolyte solution into open structures of …

Analysis Of Bolted Joints Under Medium And High Impact Loading, Deepak Somasundaram

UNLV Theses, Dissertations, Professional Papers, and Capstones

Understanding the transient behavior of structures with bolted joints when subjected to medium and high shock or impact loads can be challenging due to their nonlinear response, which is induced by the complex interactions between the bolts and the structure. While few researchers have considered shock transmission through bolted joints at low impact loading, there are little literature on shock transmission through bolted joints under high loading conditions. Low impact loading condition generally excites the lower order frequencies but under high impact loading higher order frequencies are excited. Typical factors that affect the response of a bolted joint include, preload …

Simulations Of Interfacial Electrokinetics With Applications To Microfluidic Systems, Sebastian Uppapalli

UNLV Theses, Dissertations, Professional Papers, and Capstones

Electrokinetics plays an important role in facilitating fluid transport and particle manipulation in microfluidic systems. This dissertation studies the mechanics of electrokinetic phenomena for microscale particles and drops. The work aims to increase the understanding of complex electrokinetic phenomena for applications in Lab-on-Chip technology, assembly of colloidal particles and two-phase flow sensing. The standard model consisting of the Poisson-Nernst-Planck equations is used to study the electric double layer polarization of charged dielectric particles and channel wall which plays a major role in control and manipulation of colloidal particles and understanding of electrohydrodynamic flow field.

The cases of polarization of "soft" …

Numerical Study Of A Novel Fin Configuration Of A High Temperature Ceramic Plate Fin Heat Exchanger, Vijaisri Nagarajan

UNLV Theses, Dissertations, Professional Papers, and Capstones

Compact heat exchangers are widely used in industries due to their compactness, reduced space, energy requirement and desired thermal performance. The proposed ceramic plate fin heat exchanger (PFHE) based on the offset strip fin design is used in applications which require extreme operating temperatures. It is well known that the compact heat exchanger requires small fins and channels to achieve high heat transfer rate and thermal performances. The fins in the ceramic heat exchanger ensure periodic restart of the boundary layer region which increases the thermal performance or heat transfer enhancement of the heat exchanger.

In this dissertation a novel …

Design And Analysis Of Hydrogen Powered Actuator Integrating Metal Hydride Storage System, Md Mainul Hossain Bhuiya

UNLV Theses, Dissertations, Professional Papers, and Capstones

The multi-fold purposes of this dissertation consists of construction, simulation and validation of a model describing hydrogen sorption kinetics in metal hydride. The project involves a comprehensive review of engineering applications involving metal hydrides and furthermore, design and investigation of a thermo-kinetically driven actuation system integrating metal hydrides for compact and soft robotic actuation. This will also shed some light on the feasibility of designing a damping system integrating metal hydride. Firstly, a mathematical model along with comprehensive simulation strategy of hydrogen absorption and desorption processes in porous metal hydride compacts was developed. A two dimensional axisymmetric model was built …

The Design And Implementation Of A Multi-Chip Power Module Layout Synthesis Tool, Brett W. Shook

Graduate Theses and Dissertations

This thesis presents the design and implementation of a software tool, referred to as PowerSynth, which is used to synthesize multi-chip power module (MCPM) layouts and also aids in the overall design process. MCPMs allow power electronics systems to achieve higher efficiencies and reduced size, weight, and cost through the compact integration of devices into a single package. MCPM design is highly multidisciplinary which involves electrical, thermal, and mechanical performance considerations. Conventionally, the design process may require several iterations and multiple software modeling tools to create high performance MCPMs. The layout of an MCPM consists of a pattern of metal …

High Temperature Ltcc Based Sic Double-Sided Cooling Power Electronic Module, Hao Zhang

Graduate Theses and Dissertations

This objective of this dissertation research is to investigate a module packaging technology for high temperature double-sided cooling power electronic module application. A high-temperature wire-bondless low-temperature co-fired ceramic (LTCC) based double-sided cooling power electronic module was designed, simulated and fabricated. In this module, the conventional copper base plate is removed to reduce the thermal resistance between the device junctions to the heat sink and to improve the reliability of the module by eliminating the large area solder joint between the power substrate and the copper base plate. A low-temperature co-fired ceramic (LTCC) substrate with cavities and vias is used as …

Fundamentals Of Machine Design And Manufacturing: Design Of A Compliant Winding Machine, Gazal Kaur Nagi

Doctoral Dissertations and Master's Theses

A Sparton Electronics Compliant Winding Machine has been redesigned for improved performance. Thorough study of the existing machine identified issues such as the inconsistent diameter and pitch of the compliant wind, outdated equipment, as well as safety and ergonomic issues. A comprehensive methodology for the design of the new machine is presented through using CAD systems and advanced analysis tools, such as Finite Element Analysis, and HEEDS. Resulting, the machine is successfully re-designed to fully control the diameter and the pitch of the product via servo motors and a control panel. The safety and ergonomic issues are effectively resolved by …

Simulation Of Thermal Transit-Time Flow Meter For High Temperature, Corrosive And Irradiation Environment, Elaheh Alidoosti

UNLV Theses, Dissertations, Professional Papers, and Capstones

In the environments of high temperature (300o C - 1000o C), corrosive and even irradiation application, the challenges of providing reliable and accurate flow rate measurement is significant. In comparing with many other existing technologies for normal operation environments, correlated thermal transit-time flow meter show its advantages of resolving the challenges encountered in those harsh conditions. The correlated thermal signals can be detected by two separated thermal sensors (for example, thermocouples) in series alignment along the pipe, and derive the flow rate. It was evaluated to have accurate measurement for small pipe at slow fluid speed. In the higher flow …

Study Of Water Transport Phenomena On Cathode Of Pemfcs Using Monte Carlo Simulation, Karn Soontrapa

UNLV Theses, Dissertations, Professional Papers, and Capstones

This dissertation deals with the development of a three-dimensional computational model of water transport phenomena in the cathode catalyst layer (CCL) of PEMFCs. The catalyst layer in the numerical simulation was developed using the optimized sphere packing algorithm. The optimization technique named the adaptive random search technique (ARSET) was employed in this packing algorithm. The ARSET algorithm will generate the initial location of spheres and allow them to move in the random direction with the variable moving distance, randomly selected from the sampling range, based on the Lennard-jones potential of the current and new configuration. The solid fraction values obtained …

Inkjet Printing Of Three-Dimensional Vascular-Like Constructs From Cell Suspensions, Changxue Xu

All Dissertations

Inkjet printing has found an increasing number of biofabrication applications, specifically organ printing, which has been emerging as a promising solution to the organ donor shortage. While some studies have been conducted to investigate various engineering problems associated with DOD inkjet printing of biological material-based fluids, the pinch-off, the cell-laden droplet formation, the effects of electric field on droplet formation, and challenges in 3D vascular-like construct fabrication haven't been systematically investigated. The objective of this study is to investigate the pinch-off, the cell-laden droplet formation, the effects of electric field on droplet formation, and manufacturing challenges during fabrication using DOD …

Adaptive And Robust Braking-Traction Control Systems, John Adcox

All Dissertations

The designs of commercial Anti-Lock Braking Systems often rely on assumptions of a torsionally rigid tire-wheel system and heavily rely on hub-mounted wheel speed sensors to manage tire-road slip conditions. However, advancements in high-bandwidth braking systems, in-wheel motors, variations in tire/wheel designs, and loss of inflation pressure, have produced scenarios where the tire's torsional dynamics could be easily excited by the braking system actuator. In these scenarios, the slip conditions for the tire-belt/ring will be dynamically different from what can be inferred from the wheel speed sensors. This dissertation investigates the interaction of tire torsional dynamics with ABS & traction …

System Identification Of A Small Low-Cost Unmanned Aerial Vehicle Using Flight Data From Low-Cost Sensors, Nathan V. Hoffer

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Remote sensing has usually been done with satellites and manned aircraft. While they can be useful, satellites and manned aircraft have issues in how quickly you can get data, process it, and go back to get more data. Small low-cost unmanned aerial vehicles (UAVs) overcome these issues. To collect precise data a precise model of the UAV is needed to develop the autopilot, make sure the aircraft flies well, and does not break. One method of making a model is system identification (system ID). In this thesis system ID of a small low-cost fixed-wing T-tail UAV is done. The equations …

Spacecraft Guidance Techniques For Maximizing Mission Success, Shane B. Robinson

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Traditional spacecraft guidance techniques have the objective of deterministically minimizing fuel consumption. These traditional approaches to guidance are developed independently of the navigation system, and without regard to stochastic effects. This work presents and demonstrates a new approach to guidance design. This new approach seeks to maximize the probability of mission success by minimizing the variance of trajectory dispersions subject to a fuel consumption constraint. The fuel consumption constraint is imposed by formulating the dynamics in terms of a steering command, and placing a constraint on the final time. Stochastic quadratic synthesis is then used to solve for the nominal …

Uncertainty Analysis Of Mechanical Properties From Miniature Tensile Testing Of High Strength Steels, Deepthi Rao Malpally

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

This Miniature mechanical testing study is concerned with the use of miniature specimens to identify the mechanical properties of stainless steel Type 304, sensitized Type 304 and SA516 Grade 70 carbon steel as a viable replacement for the standard sized mechanical testing. The study aims at obtaining suitable specimen geometry and tensile testing procedure for miniature mechanical testing whose mechanical properties are comparable to that of conventional specimens of ASTM A370-10 of the same steel. All specimens are at and the gauge length cross section will be varied to obtain suitable geometry. The miniature tensile testing results are further validated …

Anisotropy Of The Reynolds Stress Tensor In The Wakes Of Counter-Rotating Wind Turbine Arrays, Nicholas Michael Hamilton

Dissertations and Theses

A wind turbine array was constructed in the wind tunnel at Portland State University in a standard Cartesian arrangement. Configurations of the turbine array were tested with rotor blades set to rotate in either a clockwise or counter-clockwise sense. Measurements of velocity were made with stereo particle-image velocimetry. Mean statistics of velocities and Reynolds stresses clearly show the effect of direction of rotation of rotor blades for both entrance and exit row turbines. Rotational sense of the turbine blades is visible in the mean spanwise velocity W and the Reynolds shear stress -[macron over vw]. The normalized anisotropy tensor was …

Bifurcation Type Change Of Ac Electrostatically Actuated Mems Resonators Due To Dc Bias, Dumitru Caruntu, Kyle N. Taylor

Mechanical Engineering Faculty Publications

This paper investigates the nonlinear response of microelectromechanical system (MEMS) cantilever resonator electrostatically actuated by applying a soft alternating current (AC) voltage and an even softer direct current (DC) voltage between the resonators and a parallel fixed ground plate. The AC frequency is near natural frequency. This drives the resonator into nonlinear parametric resonance. The method ofmultiple scales (MMS) is used to solve the dimensionless differential equation of motion of the resonator and find the steady-state solutions.The reduced order model (ROM) method is used to validate the results obtained using MMS. The effect of the soft DC voltage (bias) component …

A Sinteractive Ni-Bazr0.8Y0.2O3-Δ Composite Membrane For Hydrogen Separation, Shumin Fang, Siwei Wang, Kyle S. Brinkman, Fanglin Chen

Faculty Publications

BaZr_0.8Y_0.2O_3−δ (BZY) is an excellent candidate material for hydrogen permeation membranes due to its high bulk proton conductivity, mechanical robustness, and chemical stability in H₂O- and CO₂-containing environments. Unfortunately, the use of BZY as a separation membrane has been greatly restrained by its highly refractory nature, poor grain boundary proton conductivity, high number of grain boundaries resulting from limited grain growth during sintering, as well as low electronic conductivity. These problems can be resolved by the fabrication of a Ni–BZY composite membrane with large BZY grains, which requires the development …

Application Of Limited Mixing In The Hele–Shaw Geometry In Fabrication Of Janus Hydrogels, Md Mahmudur Rahman

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

It is widely accepted that cells behave differently responding to the stiffness of their extracellular matrix (ECM). Such observations were made by culturing cells on hydrogel substrates of tunable stiffness. However, it was recently proposed that cells may sense how strongly they are tethered to ECM, not the local stiffness of ECM. To investigate both hypotheses, we developed a method to fabricate Janus polyacrylamide (PAAM) gels. We squeeze two drops of different concentrations in the Hele-Shaw geometry to generate radial Stokes flow. When the drops coalesce, limited mixing occurs at the interface due to the narrow confinement, and diffusion normal …