Mechanical Engineering Commons^™

Fatigue Based Structural Design Exploration Via Engineering Data Analytics, Hao Li

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In manufacturing industry, a successful machine development requires the durability of structure components to meet fatigue life targets. The typical way to obtain fatigue design loads for conceptual design exploration is based on hand calculations or historical data to capture envelopes of expected system responses, which may not guarantee to capture actual damaging loads. In this study, a new approach is developed to extract a fatigue design load set directly from measured load data for a conceptual design exploration. The proposed framework integrates the techniques from data analytics and physics based engineering mechanics to amplify and detect fundamental damaging load …

Stochastic Modeling Of Geometric Mistuning And Application To Fleet Response Prediction, Emily Brooke Henry

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An improved spatial statistical approach and probabilistic prediction method for mistuned integrally bladed rotors is proposed and validated with a large population of rotors. Prior work utilized blade-alone principal component analysis to model spatial variation arising from geometric deviations contributing to forced response mistuning amplification. Often, these studies considered a single rotor measured by contact probe coordinate measurement machines to assess the predictive capabilities of spatial statistics through principal component analysis. The validity of the approach has not yet been demonstrated on a large population of mistuned rotors representative of operating fleets, a shortcoming addressed in this work. Furthermore, this …

An Experimental Investigation On The Micro Air Vehicle, Shih Kang Huang

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An experimental investigation was conducted to study the flow characteristics of the flow around the flapping wings of a four-wing flapper as well as the lift and thrust coefficient of a four-wing flapper. In the present study, a clap-and-fling type of four-wing flapper was designed and manufactured by using several flexible materials, such as PET film, latex, and aluminized Mylar. Different cross-strut patterns and dimensions of wings were manufactured and tested to optimize the wing designs. In addition to taking the lift and thrust measurements using a highly sensitive force moment sensor unit, a high-resolution Particle Image Velocimetry (PIV) system …

Experimental Assessment Of Photovoltaic Irrigation System, Khalil Raza

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Agriculture is a significant measure of an economy for a number of countries in the world. Currently, the agriculture sector relies heavily on conventional sources of energy for irrigation and other purposes. When, considering factors such as increasing costs of fossil fuels and extending new power lines, especially to remote locations where grid electricity is either inaccessible or expensive, a solar PV (photovoltaic) irrigation system can be an effective choice for irrigating farmland. Solar power eliminates the need to run electrical power lines to remote agriculture locations, which quickly turns the monetary equation in favor of solar irrigation over grid-powered …

Validation Studies Of Sc/Tetra Code In 2d And 3d Simulations, Shuo Mao

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In this thesis, 2D CFD simulations, 3D CFD simulations, and one 2D Fluid-Structure Interaction (FSI) problem were investigated using combined CFD and an FEA (Finite Element Analysis) tool. Discussions focused on turbulence models, mesh sizes, prism layer sizes, under-relaxation-factor, etc. The solution of CFD simulation and FSI simulation was validated using the results of previous CFD solvers and experimental data presented in the literature. The SST model results for the 2D mixing layer, 2D airfoil near-weak, axisymmetric subsonic jet, and 2D convex curvature boundary layer studies agree with previous CFD results within a 1% error. The k-e model with wall …

Computational Investigation Of Rotary Engine Homogeneous Charge Compression Ignition Feasibility, Michael Irvin Resor

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The Air Force Research Laboratory (AFRL) has been investigating the heavy fuel conversion of small scale Unmanned Aerial Vehicles (UAV). One particular platform is the Army Shadow 200, powered by a UEL Wankel rotary engine. The rotary engine historically is a proven multi-fuel capable engine when operating on spark ignition however, little research into advanced more efficient compression concepts have been investigated. A computational fluid dynamics model has been created to investigate the feasibility of a Homogeneous Charge Compression Ignition (HCCI) rotary engine. This research evaluates the effects, rotor radius to crankshaft eccentricity ratio, known as K factor, equivalence ratio, …

Oil Droplet Behavior At A Pore Entrance In The Presence Of Crossflow: Implications For Microfiltration Of Oil-Water Dispersions, Nikolai V. Priezjev, Tohid Darvishzadeh, Volodymyr V. Taravara

Mechanical and Materials Engineering Faculty Publications

The behavior of an oil droplet pinned at the entrance of a micropore and subject to clossflow-induced shear is investigated numerically by solving the Navier-Stokes equation. We found that in the absence of crossflow, the critical transmembrane pressure required to force the droplet into the pore is in excellent agreement with a theoretical prediction based on the Young-Laplace equation. With increasing shear rate, the critical pressure of permeation increases, and at sufficiently high shear rates the oil droplet breaks up into two segments. The results of numerical simulations indicate that droplet breakup at the pore entrance is facilitated at lower …

Heterogeneous Relaxation Dynamics In Amorphous Materials Under Cyclic Loading, Nikolai V. Priezjev

Mechanical and Materials Engineering Faculty Publications

Molecular dynamics simulations are performed to investigate heterogeneous dynamics in amorphous glassy materials under oscillatory shear strain. We consider three-dimensional binary Lennard-Jones mixture well below the glass transition temperature. The structural relaxation and dynamical heterogeneity are quantified by means of the self-overlap order parameter and the dynamic susceptibility. We found that at sufficiently small strain amplitudes, the mean square displacement exhibits a broad subdiffusive plateau and the system undergoes nearly reversible deformation over about 104 cycles. Upon increasing strain amplitude, the transition to the diffusive regime occurs at shorter time intervals and the relaxation process involves intermittent bursts of large …

Anisotropic Compositional Expansion And Chemical Potential For Amorphous Lithiated Silicon Under Stress Tensor, Valery I. Levitas, Hamed Attariani

Mechanical and Materials Engineering Faculty Publications

Si is a promising anode material for Li-ion batteries, since it absorbs large amounts of Li. However, insertion of Li leads to 334% of volumetric expansion, huge stresses, and fracture; it can be suppressed by utilizing nanoscale anode structures. Continuum approaches to stress relaxation in Li_xSi, based on plasticity theory, are unrealistic, because the yield strength of Li_xSi is much higher than the generated stresses. Here, we suggest that stress relaxation is due to anisotropic (tensorial) compositional straining that occurs during insertion-extraction at any deviatoric stresses. Developed theory describes known experimental and atomistic simulation …

A Comparative Study Of Three Different Chemical Vapor Deposition Techniques Of Carbon Nanotube Growth On Diamond Films, Betty T. Quinton, Paul N. Barnes, Chakrapani V. Varanasi, Bang-Hung Tsao, Kevin J. Yost, Sharmila M. Mukhopadhyay

Mechanical and Materials Engineering Faculty Publications

This paper compares between the methods of growing carbon nanotubes (CNTs) on diamond substrates and evaluates the quality of the CNTs and the interfacial strength. One potential application for these materials is a heat sink/spreader for high-power electronic devices. The CNTs and diamond substrates have a significantly higher specific thermal conductivity than traditional heat sink/spreader materials making them good replacement candidates. Only limited research has been performed on these CNT/diamond structures and their suitability of different growth methods. This study investigates three potential chemical vapor deposition (CVD) techniques for growing CNTs on diamond: thermal CVD (T-CVD), microwave plasma-enhanced CVD (MPE-CVD), …

Nanomaterials Synthesis, Applications, And Toxicity 2012, Mallikarjuna Nadagouda, Dionysios Demetriou Dionysiou, Darren A. Lytle, Thomas F. Speth, Sharmila M. Mukhopadhyay

Mechanical and Materials Engineering Faculty Publications

Nanotechnology presents new opportunities to create better materials and products. Nanomaterials find wide applications in catalysis, energy production, medicine, environmental remediation, automotive industry, and other sectors of our society. Nanomaterial-containing products are already available globally and include automotive parts, defense application, drug delivery devices, coatings, computers, clothing, cosmetics, sports equipment, and medical devices. This special issue includes emerging advances in the field, with a special emphasis given to nanomaterial synthesis and applications.

A Computational Approach To Simulating The Performance Of A 24-Hour Solar-Fuel Cell-Hydrogen Electric Power Plant, Michael K. Gustafson

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World energy demand has risen from about 375 exajoules (EJ) in 1990 to around 600 EJ today. The Energy Information Administration predicts that by the year 2035, this figure will rise to around 800 EJ. This places large stresses on the electric generation infrastructure. Increasingly this demand is being met by renewable energy sources. There are several reasons this is the case. The prices of renewables are dropping quickly and reaching grid parity in more regions. Utilizing renewable energy generation can help achieve energy security: adverse weather or military conflicts are less likely to impact supply routes when energy is …

Dynamic Simulation Of Turbine Engine Used With Molten Carbonate Fuel Cell For Power Generation In The Megawatt Range, Carlos Eduardo Gutierrez

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Molten carbonate fuel cells (MCFC) have a high operating temperature of approximately 650° C (1200° F) to achieve sufficient conductivity of its carbonate electrolyte. Therefore, a gas turbine engine coupled with a MCFC is desirable since the turbine engine can be used to provide hot gas to the cathode, and the cathode gas residue can be used to raise the temperature of the natural gas and water vapor mixture (fuel) before it enters the MCFC at the anode. Dynamic models of a hybrid power plant consisting of a gas turbine engine and a MCFC with their respective components were developed …

Shock Correlation Investigation In A Gaseous Fueled Axisymmetric Scramjet Flowpath, Jaime Omar Larios-Barbosa

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A pressure-based investigation was conducted on a gaseous fueled axisymmetric scramjet flowpath in Research Cell 22 located at Wright Patterson AFB. The investigation followed the work performed by Waltrup and Billig using combustion data to validate the form of the correlation in an attempt to achieve a good predictive tool for isolator length. Two years of axial wall pressure data using Mach values of 1.8 and 2.2 were analyzed in this investigation. The combustion data was shown to follow the same quadratic distribution show in Waltrup and Billig's work with the data being shifted to the right relative to the …

Wing Damage Effect On Dragonfly's Aerodynamic Performance During Takeoff, Kuo Gai

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Insect wing damage resulted from living environment or predation commonly happens in nature. This usually results in deterioration of insect's flight performance and as a consequence, the insect needs adjustment of flapping wings to compensate the effect from the wing loss. In this study, a dragonfly (Erythemis simpliciolis) with and without wing loss is chosen to study the change of aerodynamic performance of flapping wings. Three cases including flight with intact wings (IW), flight with one-sided forewing damage (OFD), and flight with double-side forewing damage (DFD) are determined. An integrated study using high-speed photogrammetry, three-dimensional surface reconstruction, and direct numerical …

Effect Of Process Variables On Sub-Melt Thermal Behavior And Solid-State Phase Transformations In Beam-Based Additive Manufacturing Of Ti-6al-4v, Heather N. Doak

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The success of laser and electron beam-based fabrication processes for additive manufacture and repair applications requires the ability to control melt pool geometry while maintaining a consistent and desirable microstructure. Previous work has employed a process map approach to link melt pool geometry to solidification microstructure (grain-size and morphology) in beam-based fabrication of Ti-6Al-4V. The current work extends the approach to investigate the effects of process variables on solid-state phase transformations below the solidification temperature through Finite Element Modeling, the 3-D Rosenthal Solution, and experimentation. Process maps for solid-state microstructure could be used to help maintain consistent and reliable mechanical …

Design And Improve Energy Efficiency And Functionalities Of Electrical Wheelchairs, Dewei Guan

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There are millions of people who have lost their abilities to walk and wheelchairs offer the ONLY opportunities for their interactions with people and environments outside their houses. These individuals are becoming more and more eager to adapt modern technologies on their wheelchairs to improve quality of social life and the life of freedom. However, most available electric wheelchairs, driven by traditional lead-acid batteries and gear motors, are heavy and bulky in design with low energy efficiency, limited travel radius, and scarce communication/navigation functionalities. This project is to design and prototype an electric wheelchair that is lighter, more flexible in …

An Experimental Investigation On The Control Of Tip Vortices From Wind Turbine Blade, Zhe Ning

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Wind turbine dynamics, wake effects and environmental impacts have been identified the most significant research topics needed for wind resource characterization and wind power generation. Among these issues, tip vortices generated from the blade tip have been recognized as a substantial resource for the turbulent wake flow as well as the aerodynamic noise emission from a wind turbine. An experimental study is conducted to characterize the evolution of the tip vortices downstream of a well-designed horizontal axis wind turbine (HAWT) model. In addition to measuring dynamic wind loads (both aerodynamic forces and moments) and power output from the wind turbine …

Steps In The Development Of A Full Particle-In-Cell, Monte Carlo Simulation Of The Plasma In The Discharge Chamber Of An Ion Engine, Bryan James Penkal

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The design and development of ion engines is a difficult and expensive process. In order to alleviate these costs and speed ion engine development, it is proposed to further develop a particle-in-cell (PIC), Monte-Carlo collision (MCC) model of an ion engine discharge chamber, which has previously been worked on by the Wright State Ion Engine Modeling Group. Performing detailed and accurate simulations of ion engines can lead to millions of dollars in savings in development costs.

In order to recognize these savings more work must be done on the present day models used to simulate ion engine performance. The work …

Bull's-Eye Structure With A Sub-Wavelength Circular Aperture, Masoud Zarepoor

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This research focuses on improving the spatial resolution of terahertz (THz) imaging. Using a sub-wavelength aperture in a metal ground plane is the most common way to improve the spatial resolution, but a sub-wavelength aperture has low radiation transmission. To increase the radiation transmission of a sub-wavelength aperture, periodic circular grooves were put in the metal around the aperture. The sub-wavelength circular aperture and the periodic circular grooves around it are known as the bull's-eye structure. The bull's-eye structure shows high radiation transmission at its design frequency, and it also has sub-wavelength spatial resolution. This research designed the bull's-eye structure …

Structural-Acoustic Analysis And Optimization Of Embedded Exhaust-Washed Structures, Ryan N. Vogel

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The configurations for high speed, low observable aircraft expose many critical areas on the structure to extreme environments of intense acoustic pressure loadings. When combined with primary structural and thermal loads, this effect can cause high cycle fatigue to aircraft skins and embedded exhaust system components. In past aircraft design methods, these vibro-acoustic loads have often been neglected based on their relatively small size compared to other thermal and structural loads and the difficulty in capturing their dynamic and frequency dependent responses. This approach is insufficient for effective advanced designs of complex aerospace structures, such as internal ducted exhaust systems …

Effects Of Crossflow Velocity And Transmembrane Pressure On Microfiltration Of Oil-In-Water Emulsions, Nikolai V. Priezjev, Tohid Darvishzadeh

Mechanical and Materials Engineering Faculty Publications

This study addresses the issue of oil removal from water using hydrophilic porous membranes. The effective separation of oil-in-water dispersions involves high flux of water through the membrane and, at the same time, high rejection rate of the oil phase. The effects of transmembrane pressure and crossflow velocity on rejection of oil droplets and thin oil films by pores of different cross-section are investigated numerically by solving the Navier-Stokes equation. We found that in the absence of crossflow, the critical transmembrane pressure, which is required for the oil droplet entry into a circular pore of a given surface hydrophilicity, agrees …

Analysis Of Solid Oxide Fuel Cell-Gas-Turbine Hybrid System Technology For Use In Aircraft, Jeremy Milliner, Rory Roberts

Explorations – The Journal of Undergraduate Research, Scholarship and Creativity at Wright State

Solid oxide fuel-cell-gas-turbine (SOFC/GT) hybrid systems are a technology that provides a more efficient source of energy for a variety of uses. One potential use is to provide more efficient energy to aircraft, which is the subject of this work. Potential applications to aircraft and results from a computer model of a SOFC/GT are presented here.

An Experimental Investigation On The Trailing Edge Cooling Of Turbine Blades, Zifeng Yang, Hui Hu

Mechanical and Materials Engineering Faculty Publications

An experimental study was conducted to quantify the flow characteristics of the wall jets pertinent to trailing edge cooling of turbine blades. A high-resolution stereoscopic particle image velocimetry (PIV) system was used to conduct detailed flow field measurements to quantitatively visualize the evolution of the unsteady vortices and turbulent flow structures in the cooling wall jet streams and to quantify the dynamic mixing process between the cooling jet stream and the mainstream flows. The detailed flow field measurements were correlated with the adiabatic cooling effectiveness maps measured by using pressure sensitive paint (PSP) technique to elucidate underlying physics in order …

Molecular Dynamics Simulations Of Oscillatory Couette Flows With Slip Boundary Conditions, Nikolai V. Priezjev

Mechanical and Materials Engineering Faculty Publications

The effect of interfacial slip on steady-state and time-periodic flows of monatomic liquids is investigated using non-equilibrium molecular dynamics simulations. The fluid phase is confined between atomically smooth rigid walls, and the fluid flows are induced by moving one of the walls. In steady shear flows, the slip length increases almost linearly with shear rate. We found that the velocity profiles in oscillatory flows are well described by the Stokes flow solution with the slip length that depends on the local shear rate. Interestingly, the rate dependence of the slip length obtained in steady shear flows is recovered when the …

Novel Platform Development Using Assembly Of Carbon Nanotube, Nanogold And Immobilized Rna Capture Element For Rapid, Selective Sensing Of Bacteria, Elizabeth I. Maurer, Kristen K. Comfort, Saber M. Hussain, John J. Schlager, Sharmila M. Mukhopadhyay

Mechanical and Materials Engineering Faculty Publications

This study examines the creation of a nano-featured biosensor platform designed for the rapid and selective detection of the bacterium Escherichia coli. The foundation of this sensor is carbon nanotubes decorated with gold nanoparticles that are modified with a specific, surface adherent ribonucleiuc acid (RNA) sequence element. The multi-step sensor assembly was accomplished by growing carbon nanotubes on a graphite substrate, the direct synthesis of gold nanoparticles on the nanotube surface, and the attachment of thiolated RNA to the bound nanoparticles. The application of the compounded nano-materials for sensor development has the distinct advantage of retaining the electrical behavior …

Interfacial Friction Between Semiflexible Polymers And Crystalline Surfaces, Nikolai V. Priezjev

Mechanical and Materials Engineering Faculty Publications

The results obtained from molecular dynamics simulations of the friction at an interface between polymer melts and weakly attractive crystalline surfaces are reported. We consider a coarse-grained bead-spring model of linear chains with adjustable intrinsic stiffness. The structure and relaxation dynamics of polymer chains near interfaces are quantified by the radius of gyration and decay of the time autocorrelation function of the first normal mode. We found that the friction coefficient at small slip velocities exhibits a distinct maximum which appears due to shear-induced alignment of semiflexible chain segments in contact with solid walls. At large slip velocities, the friction …

Evaluating Superconducting Ybco Film Properties Using Xray Photoelectron Spectroscopy, Paul N. Barnes, Justin C. Tolliver, Timothy J. Haugan, Sharmila M. Mukhopadhyay, John T. Grant

Mechanical and Materials Engineering Faculty Publications

Initial results have been recently reported that suggest a potential correlation exists between the full-width-halfmaximum (FWHM) of the Y(3d) peak obtained by x-ray photoelectron spectroscopy (XPS) and the critical current density a YBa₂Cu₃O₇-x film can carry. In particular, the Y(3d_5/2) demonstrated a stronger correlation. Transport currents were determined by the 4-point contact method using the 1μV/cm criterion. An apparent correlation was also suggested between the Y(3d) FWHM and ac loss data points were acquired to further test the usefulness of the correlations. Samples were created by pulsed laser deposition of YBa_{2 …}

Dechlorination Of Environmental Contaminants Using A Hybrid Nanocatalyst: Palladium Nanoparticles Supported On Hierarchical Carbon Nanostructures, Hema Vijwani, Abinash Agrawal, Sharmila M. Mukhopadhyay

Mechanical and Materials Engineering Faculty Publications

This paper demonstrates the effectiveness of a new type of hybrid nanocatalyst material that combines the high surface area of nanoparticles and nanotubes with the structural robustness and ease of handling larger supports. The hybrid material is made by fabricating palladium nanoparticles on two types of carbon supports: as-received microcellular foam (Foam) and foam with carbon nanotubes anchored on the pore walls (CNT/Foam). Catalytic reductive dechlorination of carbon tetrachloride with these materials has been investigated using gas chromatography. It is seen that while both palladium-functionalized carbon supports are highly effective in the degradation of carbon tetrachloride, the rate of degradation …

Computational Investigation Of Ethanol And Bifuel Feasibility In Solstice Engine, Adam Michael Blake

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A Gasoline Direct Injection (GDI) engine enables an increased fuel efficiency and higher power output than a conventional Port Fuel Injection (PFI) system. By injecting pressurized fuel straight into each cylinder of an internal-combustion engine, the degree of fuel atomization is increased, as well as the fuel vaporization rate. In order to further harness the effects of direct injection, ethanol is implemented as a fuel. The cooling effect of ethanol fuel droplets changing to vapor inside the combustion chamber facilitates a higher compression ratio, thus increasing engine power and efficiency. Three dimensional computational simulation is used to investigate the feasibility …