Mechanical Engineering Commons^™

Kinetics Of Molten Metal Capillary Flow In Non-Reactive And Reactive Systems, Hai Fu

Theses and Dissertations--Mechanical and Aerospace Engineering

Wetting and spreading of liquid systems on solid substrates under transient conditions, driven by surface tension and viscous forces along with the interface interactions (e.g., a substrate dissolution or diffusion and/or chemical reaction) is a complex problem, still waiting to be fully understood. In this study we have performed an extensive experimental investigation of liquid aluminum alloy spreading over aluminum substrate along with corroboration with theoretical modeling, performed in separate but coordinate study. Wetting and spreading to be considered take place during a transient formation of the free liquid surface in both sessile drop and wedge-tee mating surfaces’ configurations. The …

Biventricular Finite Element Modeling And Quantification Of 3d Langragian Strains And Torsion Using Dense Mri, Zhanqiu Liu

Theses and Dissertations--Mechanical and Aerospace Engineering

Statistical data suggests that increased use of evidence-based medical therapies has largely contributed to the decrease in American death rate caused by heart disease. And my studies are about two applications of magnetic resonance imaging (MRI) as a non-invasive approach in evidence-based health care research. In my first study, the achievement of a pulmonary valve replacement surgery was assessed on a patient with tetralogy of Fallot (TOF). In order to evaluate the remodeling of right ventricle, two biventricular finite element models were built up for pre-surgical images and post-surgical images. In my second study, 3D Lagrangian strains and torsion in …

Diffusion-Mediated Deposition Of Proteins, Ruiqian Zhan

Theses and Dissertations--Mechanical and Aerospace Engineering

Gradients of proteins play a prominent role in many biological processes, from development of multicellular organisms to chemical signaling in the immune system. Deposition of surface gradients is a way to permanently modifying a surface’s properties, resulting in the creation of novel materials which have widespread applications in biologically relevant fields, such as directed cell growth, production of biocompatible implantable materials, and creation of functional biosensors. These types of surfaces can also be used as an ex vivo tool to help understand many biological processes by mimicking the environment in gradient-related phenomena in a controllable way. However, despite the large …

Comparisons Of Ablator Experimental Performance To Response Modeling And Effects Of Water Phase Transition In Porous Tps Materials, David L. Smith

Theses and Dissertations--Mechanical and Aerospace Engineering

The Mars Science Laboratory Entry Descent and Landing Instrumentation (MEDLI) project performed extensive arc jet tests for development, qualification, and calibration of instrumented heat shield plugs. These plugs each contained several thermocouples for recording near-surface and in-depth temperature response of the Phenolic Impregnated Carbon Ablator (PICA) heat shield. The arc jet test results are entered into a comprehensive database so that broad trends across the test series can be compared. One method of analysis is to compare with ablator material response calculations and solve the in-depth heat conduction equations. Using the near-surface thermocouple measurements as a boundary condition in numerical …

Development Of An Unmanned Aerial Vehicle For Atmospheric Turbulence Measurement, Brandon M. Witte

Theses and Dissertations--Mechanical and Aerospace Engineering

An unmanned aerial vehicle was developed to study turbulence in the atmospheric boundary layer. The development of the aircraft, BLUECAT5, and instrumentation package culminated in a series of flight experiments conducted in two different locations near Stillwater, Oklahoma, USA. The flight experiments employed the use of two of the unmanned aerial vehicles flying simultaneously, each containing a five-hole pressure probe as part of a turbulence-measuring instrumentation package. A total of 18 flights were completed with the objective to measure atmospheric properties at five altitudes between 20 and 120 meters. Multiple flights were flown over two days in which the effects …

Non-Dispersive Infrared (Ndir) Gas Sensor Utilizing Light-Emitting-Diodes Suitable For Applications Demanding Low-Power And Lightweight Instruments, Kyle Thurmond

Electronic Theses and Dissertations

Gas sensors that are low-power, light-weight, and rugged, while also remaining low-cost, have considerable appeal to areas from automotive to space flight. There are increasing demands for higher efficient vehicles with lower emissions in order meet regulations that are meant to mitigate or lessen the effects of climate change. An affordable, fast response sensor that can measure transient carbon monoxide (CO) and carbon dioxide (CO2) has broad application which can lead to more efficient, fuel flexible engines and regulations of harmful emissions. With compact, economical, low-power sensors that are able to continually monitor gases that are characteristic of burning materials, …

Study On Anisotropic Plasticity And Fracture Of Lightweight Metal Sheets, Yueqian Jia

Electronic Theses and Dissertations

How to reduce weight and increase fuel efficiency is a critical challenge in transportation industries. One way to resolve the problem is to adopting lightweight alloys (i.e. advanced high strength steel, aluminum alloys, or magnesium alloy) in structure designs and manufacturing. Fully understanding the mechanical properties of these materials is a key step. In order to fully characterize the plasticity and fracture of magnesium AZ31B-H24 sheets, a set of mechanical experiments (170 in total) were performed under both monotonic and non-proportional loading conditions, including monotonic uniaxial tension, notch tension, in-plane uniaxial compression, wide compression (or called biaxial compression), plane strain …

Characterization Of Slm-Manufactured Turbine Blade Microfeatures From Superalloy Powders, Brandon Ealy

Electronic Theses and Dissertations

The limits of gas turbine technology are heavily influenced by materials and manufacturing capabilities. Inconel remains the material of choice for most hot gas path (HGP) components in gas turbines, however recent increases in turbine inlet temperature (TIT) are associated with the development of advanced convective cooling methods and ceramic thermal barrier coatings. Increasing cycle efficiency and cycle specific work are the primary drivers for increasing TIT. Lately, incremental performance gains responsible for increasing the allowable TIT have been made mainly through innovations in cooling technology, specifically convective cooling schemes. An emerging manufacturing technology may further facilitate the increase of …

Catalytically Enhanced Heterogeneous Combustion Of Methane, Anthony Terracciano

Electronic Theses and Dissertations

Heterogeneous combustion is an advanced internal combustion technique, which enables heat recuperation within the flame by utilizing a highly porous ceramic media as a regenerator. Heat released within the gas phase convectively transfers to the solid media. This heat within the solid media then travels towards the inlet, enabling reactant preheating. Such heat redistribution enables stable burning of both ultra-lean fuel/air mixtures, forming a more diffuse flame through the combustion chamber, and results in reduced pollutant formation. To further enhance heterogeneous combustion, the ceramic media can be coated with catalytically active materials, which facilitates surface based chemical reactions that could …

Investigation Of Real Gas Effects On Centrifugal Compressor Analytical Methods For Supercritical Co2 Power Cycles, Lauren Blanchette

Electronic Theses and Dissertations

As supercritical carbon dioxide (sCO2) power cycles have shown potential to be the next generation power cycle, an immense amount of research has gone into developing this system. One of the setbacks facing development and optimization of this cycle is the unknown in current design and analysis methods ability to accurately model turbomachinery working with sCO2. Due to the desired inlet conditions to the compressor close proximity to the critical point, accurate design and analysis of this power cycle component is one of the main concerns. The present study provides aerodynamic analysis of a centrifugal compressor impeller blade with sCO2 …

Aeroelastic Investigation Of A Circumferentially Varying Tip Gap In An Axial Compressor Rotor, Ornan David Canon

Electronic Theses and Dissertations

The tip leakage flow in axial compressors is a significant factor in engine performance and a subject of investigation over the last several decades. Many studies have already shown that the vortices generated by this tip leakage can have a negative impact on the surrounding flow field and overall performance, and could potentially lead to excitations as well. This study examines the effect of these vortices on aeroelasticity. Specifically, it looks at the effect from a circumferentially varying tip gap, such as that produced by casing ovalization. For this project, the casing ovalization of an industrial gas turbine compressor was …

The Effect Of Vibrations On Cryogens Boil Off During Launch, Transfer And Transport, Erin Schlichenmaier

Electronic Theses and Dissertations

Boil-off of a cryogenic fluid which is caused by the temperature difference between the fluid and its environment is a phenomenon which has long been studied and is well understood. However, vibrational excitation of a cryogenic storage tank and the fluid inside it also play a role in the loss of cryogens. Mechanical energy applied to the system in the form of vibrational input is converted into thermal energy via viscous damping of the fluid. As a result, when a storage tank full of cryogenic fluids is vibrated, it boils off at an increased rate. A series of experiments were …

Design Optimization Of Sandwich Core, Mohammad Tauhiduzzaman

Open Access Theses & Dissertations

Ultralight sandwich structures comprising of low-density core with stiff facings have attracted significant research interest for their considerable weight saving applications. The aircraft industries are focusing on decreasing the structural mass to lower the manufacturing and operating costs. Design analysis of the sandwich cores using finite element analysis has been developed as a promising concept to feature sandwich structures with maximum strength, stiffness, and reduced weight. To obtain multifunctional behavior of sandwich panels, a profound investigation of geometrical and mechanical properties in the transverse plane is required because it is very susceptible to any kind loadings. Structural optimization is one …

Production Of Β-Silicon Carbide Nanofibers Using The Forcespinning® Method, Alfonso Salinas, Aleksey Altecor, Maricela Lizcano, Karen Lozano

Mechanical Engineering Faculty Publications

Silicon carbide (SiC) nanofibers were produced on a large scale using the Forcespinning® method. Non-oxide ceramics such as SiC are known for their low density, oxidation resistance, thermal stability, and wear resistance. The nanofibers were prepared using a solution-based method with polystyrene and polycarbomethylsilane as the precursor materials. Fiber spinning was performed under different parameters to obtain high yield, fiber homogeneity, and small diameters. The fibers were spun under a controlled nitrogen environment to prevent fiber oxidation. The resultant nonwoven nanofiber mats were then subjected to different heat treatments to evaluate the effect of these on the crystalline structure. Characterization …

Assessing Postural Stability Via The Correlation Patterns Of Vertical Ground Reaction Force Components, Chih-Yuan Hong, Lan-Yuen Guo, Rong Song, Mark L. Nagurka, Jia-Li Sung, Chen-Wen Yen

Mechanical Engineering Faculty Research and Publications

Background

Many methods have been proposed to assess the stability of human postural balance by using a force plate. While most of these approaches characterize postural stability by extracting features from the trajectory of the center of pressure (COP), this work develops stability measures derived from components of the ground reaction force (GRF).

Methods

In comparison with previous GRF-based approaches that extract stability features from the GRF resultant force, this study proposes three feature sets derived from the correlation patterns among the vertical GRF (VGRF) components. The first and second feature sets quantitatively assess the strength and changing speed of …

A Comprehensive Model Of The Transport Phenomena In Gas Metal Arc Welding, Junling Hu, Zhenghua Rao, Hai-Lung Tsai

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A comprehensive two-dimensional gas metal arc welding (GMAW) model was developed to take into account all the interactive events in the gas metal arc welding process, including the arc plasma, melting of the electrode, droplet formation, detachment, transfer, and impingement onto the workpiece, and the weld-pool dynamics and weld formation. The comprehensive GMAW model tracks the free surface using the volume of fluid method and directly modeled the coupling effects between the arc domain and the metal domain, thus eliminating the need to assign boundary conditions at the interface. A thorough investigation of the plasma arc characteristics was conducted to …

Geometric Consideration Of Nanostructures For Energy Storage Systems, Jonghyun Park, Jie Li, Wei Lu, Ann Marie Sastry

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Battery performance and its fade are determined by various aspects such as the transport of ions and electrons through heterogeneous internal structures; kinetic reactions at the interfaces; and the corresponding interplay between mechanical, chemical, and thermal responses. The fundamental factor determining this complex multiscale and multiphysical nature of a battery is the geometry of active materials. In this work, we systematically consider the tradeoffs among a selection of limiting geometries of media designed to store ions or other species via a diffusion process. Specifically, we begin the investigation by considering diffusion in spheres, rods, and plates at the particle level, …

Ionic And Electronic Conductivities Of Atomic Layer Deposition Thin Film Coated Lithium Ion Battery Cathode Particles, Rajankumar L. Patel, Jonghyun Park, Xinhua Liang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

It is imperative to ascertain the ionic and electronic components of the total conductivity of an electrochemically active material. A blocking technique, called the “Hebb-Wagner method”, is normally used to explain the two components (ionic and electronic) of a mixed conductor, in combination with the complex ac impedance method and dc polarization measurements. CeO₂ atomic layer deposition (ALD)-coated and uncoated, LiMn₂O₄ (LMO) and LiMn_1.5Ni_0.5O₄ (LMNO) powders were pressed into pellets and then painted with silver to act as a blocking electrode. The electronic conductivities were derived from the currents obtained using …

Silicon-Wall Interfacial Free Energy Via Thermodynamics Integration, Wan Shou, Heng Pan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

We compute the interfacial free energy of a silicon system in contact with flat and structured walls by molecular dynamics simulation. The thermodynamics integration method, previously applied to Lennard-Jones potentials [R. Benjamin and J. Horbach, J. Chem. Phys. 137, 044707 (2012)], has been extended and implemented in Tersoff potentials with two-body and three-body interactions taken into consideration. The thermodynamic integration scheme includes two steps. In the first step, the bulk Tersoff system is reversibly transformed to a state where it interacts with a structureless flat wall, and in a second step, the flat structureless wall is reversibly transformed into an …

The Coupled Photothermal Reaction And Transport In A Laser Additive Metal Nanolayer Simultaneous Synthesis And Patterning For Flexible Electronics, S. Tsai, Y. Liu, Heng Pan, C. Liu, M. Lee

Mechanical and Aerospace Engineering Faculty Research & Creative Works

No abstract provided.

Output Feedback Adaptive Control With Low-Frequency Learning And Fast Adaptation, Tanmay Rajpurohit, Wassim M. Haddad, Tansel Yucelen

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Although adaptive control has been used in numerous applications to achieve system performance without excessive reliance on system models, the necessity of high-gain learning rates for achieving fast adaptation can be a serious limitation of adaptive controllers. Specifically, in safety-critical systems involving large system uncertainties and abrupt changes in system dynamics, fast adaptation is required to achieve stringent tracking performance specifications. However, fast adaptation using high-gain learning rates can cause high-frequency oscillations in the control response, resulting in system instability. This paper develops an output feedback adaptive control framework for continuous-time minimum-phase multivariable dynamical systems for output stabilization and command …

Observation Of Late-Time Ablation In Electric Solid Propellant Pulsed Microthrusters, Matthew S. Glascock, Joshua L. Rovey, Shae Williams, Jason Thrasher

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Electric solid propellants are an interesting potential option for propulsion because they are ignited by an applied electric current. The electric nature of these materials leads to the capability for use in pulsed electric propulsion devices. In this work, the ablation process of an electric solid propellant during pulsed micro thruster operation is investigated using a triple Langmuir probe, thrust stand and high-speed video camera. Results include quantitative time-of-flight, ablation mass per pulse and impulse-per-pulse measurements. Additionally, qualitative images from the high-speed video are temporally correlated to these measurements. Analyses indicate 45±11% of the ablated mass per pulse is expelled …

Mass Spectrometry Of Selected Ionic Liquids In Capillary Electrospray At Nanoliter Volumetric Flow Rates, Shawn W. Miller, Benjamin D. Prince, Raymond J. Bemish, Joshua L. Rovey

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Capillary-based electrospray thrusters allow user-enabled control of the volumetric flow rate of the propellant. This control, coupled with mass spectrometry techniques spanning a large mass-to-charge range, enables elucidation of the composition of the electrospray beam and through further analyses, a better understanding of the physics occurring at the liquid/vacuum interface. In this work, mass spectra of selected ionic liquids electro sprayed from a capillary emitter are measured, using time-of-flight mass spectrometry, over a wide range of volumetric flow rates. The time-of-flight mass spectrometer enables simultaneous acquisition over a mass-to-charge range of 20 amu/q to ~500,000 amu/q in a single pulse …

Comparison Of Robust And Probabilistic Lmi-Based Design Of Adaptive Flight Controllers With Uncertain Input Dynamics, Mario Luca Fravolini, Tansel Yucelen, Benjamin Gruenwald, Merve Dogan, Marcello R. Napolitano

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Adaptive control-based schemes have been implemented to date in a variety of different ap-plications. However, the ability to obtain a predictable transient closed-loop performance in adaptive systems is still a challenging problem from a verification and validation point of view. To face this problem we have recently introduced an analysis and design framework for adaptive control systems in the presence of bounded uncertainty and bounded adaptive control (the boundedness can be enforced, for instance, by a parameter projection mechanism) showing that the transitory performance of a MRAC system can be expressed, analyzed, and optimized via a convex optimization formulation based …

Nebraska Summary: S1077 New Holland T7.245, Nebraska Tractor Test Lab

Nebraska Tractor Tests

ABOUT THE TEST REPORT AND USE OF THE DATA The test data contained in this report are a tabulation of the results of a series of tests. Due to the restricted format of these pages, only a limited amount of data and not all of the tractor specifications are included. The full OECD report contains usually about 30 pages of data and specifications. The test data were obtained for each tractor under similar conditions and therefore, provide a means of comparison of performance based on a limited set of reported data. EXPLANATION OF THE TEST PROCEDURES Purpose The purpose of …

Nebraska Summary: S1101 New Holland T6.175, Nebraska Tractor Test Lab

Nebraska Tractor Tests

ABOUT THE TEST REPORT AND USE OF THE DATA The test data contained in this report are a tabulation of the results of a series of tests. Due to the restricted format of these pages, only a limited amount of data and not all of the tractor specifications are included. The full OECD report contains usually about 30 pages of data and specifications. The test data were obtained for each tractor under similar conditions and therefore, provide a means of comparison of performance based on a limited set of reported data. EXPLANATION OF THE TEST PROCEDURES Purpose The purpose of …

Comparison Of Ignition Delays And Liquid Penetrations Of Jp-8, Synthetic Jp-8, And A Jp-8 Surrogate Under Diesel Engine Conditions, Kyle Yeakle

Dissertations, Master's Theses and Master's Reports

The U.S. Army and many NATO affiliates have adopted a ‘one fuel forward fuel policy’ (OFF). The goal of the OFF policy is reducing the logistics and cost involved with providing fuel for military vehicles. With this policy, the logical choice fuel is military grade jet petroleum, JP-8, because of the fuel constraints of turbo-jet engines. This requirement has made it necessary to run military compression ignited engines on JP-8. To reduce the Army’s reliance on petroleum based fuels an alternative fuel, synthetic JP-8, derived from coal and made in the Fischer-Tropsch production method is allowed to be blended up …

Experimental Study, Modelling And Controller Design For An Rcci Engine, Naga Nithin Teja Kondipati

Dissertations, Master's Theses and Master's Reports

Low Temperature Combustion (LTC) has got widespread attention over the past two decades in the field of Automotive Research and Development due to it’s potential for achieving higher efficiencies with near-zero engine out NOx and soot emissions. Among all the LTC strategies Reactivity controlled compression ignition (RCCI) has shown the most promising results due to it’s precise control over combustion phasing and heat release rate. However, RCCI being a dual-fuel stratified combustion, precise control over the injection timing of direct injected fuel and in-cylinder fuel reactivity of the mixture needs to be controlled effectively in order to achieve gross indicated …

On The Aerodynamic Properties Of Slotted-Flap Flow-Control Devices For Wind Turbine Applications, Muraleekrishnan Menon Menon Muraleedharan Nair

Dissertations, Master's Theses and Master's Reports

Wind energy is growing at a fast pace and utility-scale wind turbines growing in size with increasing rotor diameters. To sustain development of up-scaled wind turbines of tomorrow there is a need for innovation in load control methodologies. This thesis research targets an assessment of the aerodynamic properties of airfoil sections specifically intended for wind turbine applications, featuring them with flow-control devices. The use of fractional chord trailing-edge flaps as slotted-flap devices on aerodynamically active parts of a turbine blade were studied. As modular devices attached externally on existing blade designs, they comfortably form a cost-effective means for active load …

Predictive Control Of Power Grid-Connected Energy Systems Based On Energy And Exergy Metrics, Meysam Razmara

Dissertations, Master's Theses and Master's Reports

Building and transportation sectors account for 41% and 27% of total energy consumption in the US, respectively. Designing smart controllers for Heating, Ventilation and Air-Conditioning (HVAC) systems and Internal Combustion Engines (ICEs) can play a key role in reducing energy consumption. Exergy or availability is based on the First and Second Laws of Thermodynamics and is a more precise metric to evaluate energy systems including HVAC and ICE systems. This dissertation centers on development of exergy models and design of model-based controllers based on exergy and energy metrics for grid-connected energy systems including HVAC and ICEs.

In this PhD dissertation, …