Mechanical Engineering Commons^™

Luminescence Enhancement Of Cdte Nanostructures In Laf3:Ce/Cdte Nanocomposites, Mingzhen Yao, Xing Zhang, Lun Ma, Wei Chen, Alan G. Joly, Jinsong Huang, Qingwu Wang

Department of Mechanical and Materials Engineering: Faculty Publications

Radiation detection demands new scintillators with high quantum efficiency, high energy resolution, and short luminescence lifetimes. Nanocomposites consisting of quantum dots and Ce³⁺ doped nanophosphors may be able to meet these requirements. Here, we report the luminescence enhancement of LaF₃:Ce/CdTe nanocomposites which were synthesized by a wet chemistry method. CdTe quantum dots in LaF₃:Ce/CdTe nanocomposites are converted into nanowires, while in LaF₃ /CdTe nanocomposites no such conversion is observed. As a result, the CdTe luminescence in LaF₃:Ce/CdTe nanocomposites is enhanced about five times, while in LaF₃ /CdTe nanocomposites no enhancement was …

Directional Annealing-Induced Texture In Melt-Spun (Sm12Co88)99Nb1 Alloy, Tanjore V. Jayaraman, P. Rogge, Jeffrey E. Shield

Department of Mechanical and Materials Engineering: Faculty Publications

Developing texture in nanocrystalline permanent magnet alloys is of significant importance. Directional annealing is shown to produce texture in the permanent magnet alloy (Sm₁₂Co₈₈)₉₉Nb₁. Melt spinning produced isotropic grain structures of the hard magnetic metastable SmCo₇ phase, with grain sizes of ∼300 nm. Conventional annealing of melt-spun (Sm₁₂Co₈₈)₉₉Nb₁ alloy produced Sm₂Co₁₇ phase with random crystallographic orientation. Directional annealing of melt-spun (Sm₁₂Co₈₈)₉₉Nb₁ alloy, with appropriate combinations of annealing temperature and translational velocity, produced Sm_{2 …}

Skewed Bridge Behaviors: Experimental, Analytical, And Numerical Analysis, Bang-Jo Chun

Wayne State University Dissertations

In the US, nearly 33.5% of highway bridges are skewed. In the past, these skewed bridges have been analyzed as straight bridges. Nevertheless, there exists an extensive literature indicating the mechanical behavior of skewed bridges being quite different from their straight counterparts. In this thesis, to better understand the behavior of skewed bridges, experimental, numerical, and analytical researches have been conducted. The analytical method proposed here is the first of its kind in the skewed bridge research, and is expected to aid the bridge engineers with their design.

First, a three dimensional finite element analysis (FEA) model was developed and …

Test 1974: John Deere 6100d, 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 …

Numerical And Analytical Verification Of A Multiscale Computational Model For Impact Problems In Heterogeneous Viscoelastic Materials With Evolving Damage, Bruno Bachiega Araujo

Department of Engineering Mechanics: Dissertations, Theses, and Student Research

Composites are engineered materials that take advantage of the particular properties of each of its two or more constituents. They are designed to be stronger, lighter and to last longer which can lead to the creation of safer protection gear, more fuel efficient transportation methods and more affordable materials, among other examples.

This thesis proposes a numerical and analytical verification of an in-house developed multiscale model for predicting the mechanical behavior of composite materials with various configurations subjected to impact loading. This verification is done by comparing the results obtained with analytical and numerical solutions with the results found when …

Aircraft Conceptual Design - An Adaptable Parametric Sizing Methodology, Gary John Coleman

Mechanical and Aerospace Engineering Dissertations - Archive

Aerospace is a maturing industry with successful and refined baselines which work well for traditional baseline missions, markets and technologies. However, when new markets (space tourism) or new constrains (environmental) or new technologies (composite, natural laminar flow) emerge, the conventional solution is not necessarily best for the new situation. Which begs the question "how does a design team quickly screen and compare novel solutions to conventional solutions for new aerospace challenges?" The answer is rapid and flexible conceptual design Parametric Sizing. In the product design life-cycle, parametric sizing is the first step in screening the total vehicle in terms of …

Constrained Dynamics Approach For Motion Synchronization And Consensus, Divya Bhatia

Mechanical and Aerospace Engineering Theses - Archive

In this research we propose to develop constrained dynamical systems based stable attitude synchronization, consensus and tracking (SCT) control laws for the formation of rigid bodies. The generalized constrained dynamics Equations of Motion (EOM) are developed utilizing constraint potential energy functions that enforce communication constraints. Euler-Lagrange equations are employed to develop the non-linear constrained dynamics of multiple vehicle systems. The constraint potential energy is synthesized based on a graph theoretic formulation of the vehicle-vehicle communication. Constraint stabilization is achieved via Baumgarte's method. The performance of these constrained dynamics based formations is evaluated for bounded control authority.The above method has been …

Ideal Cycle Analysis Of A Regenerative Pulse Detonation Engine For Power Production, Rafaela Bellini

Mechanical and Aerospace Engineering Dissertations - Archive

Over the last few decades, considerable research has been focused on pulse detonation engines (PDEs) as a promising replacement for existing propulsion systems with potential applications in aircraft ranging from the subsonic to the lower hypersonic regimes. On the other hand, very little attention has been given to applying detonation for electric power production. One method for assessing the performance of a PDE is through thermodynamic cycle analysis. Earlier works have adopted a thermodynamic cycle for the PDE that was based on the assumption that the detonation process could be approximated by a constant volume process, called the Humphrey cycle. …

Stress Analysis Of Laminated Composite Beam With I-Section, Jitesh Cherukkadu Parambil

Mechanical and Aerospace Engineering Theses - Archive

The advantage of material properties and flexibility of choosing material have made composite materials a primary preference for structural application. Unlike isotropic materials, the parametric study of composite beams for optimized design is complicated due to high number of parameters involved in designing like lay-up sequence, and layer configuration. Moreover, the limitations of FEA techniques in designing have created a need for an analytical closed-form solution for stress analysis of laminated composite beams. The objective of this study focuses on the development of an analytical method for stress analysis of composite I-beam. This method includes the structural response due to …

Solution To Multi Term Boltzmann Equation For Plasma Assisted Combustion, Antriksh Luthra

Mechanical and Aerospace Engineering Theses - Archive

Plasma assisted ignition and combustion (PAIC) is a technology where plasma is generated by high voltage, nano second pulse duration and high repetitive rate pulses. The high reduced electric field during the pulse allows efficient electronic excitation and molecular dissociation, thereby generating a pool of chemically active radical species. This speeds up the reaction process needed to generate a high speed flame a very high energy is liberated though the mode of excited electrons to the neutral molecules of the fuel in such a way that the energy sent should not go in momentum transfer but it should be so …

Kinematic Analysis Of A Quadruped Robot Capable Of Working As A Machining Tool, Raghu Mandayam Anand

Mechanical and Aerospace Engineering Theses - Archive

Parallel robots have been proposed for some time now due to their potential advantages over serial robots in high load bearing, acceleration, stiffness and with lower moving mass. Mobile parallel configurations, i.e. multi-legged walking vehicles have been and are the focus of a great deal of current research. This thesis attempts to provide insights into the kinematic analysis of a quadruped robot capable of both walking and more importantly functioning as a machining tool. The gait analysis of quadruped robots has been extensively investigated and is not the focus of this research; however the gait ability is considered in the …

Effects Of Freezing On The Mechanical Properties Of Engineered Tissues, Lacey Mlcak

Mechanical and Aerospace Engineering Theses - Archive

Cryopreservation is used to preserve cells and tissues at low temperatures for short and long term uses. Some examples of where cryopreservation is used include the storage of organs, blood, embryos, and artificial tissues. A current challenge of cryopreservation is being able to understand and quantify the effects of freezing/thawing on the functional properties of tissues such as mechanical properties. This study investigated the changes in viscoelastic parameters of engineered tissues before and after freezing by performing creep-relaxation tests using a dynamic mechanical analyzer. Three types of engineered tissues were studied with varying cell and collagen concentrations for two different …

Experimental Study Of The Effects Of Thermally Conductive Microporous Coatings On Low Heat Flux Pool And Flow Boiling, Matthew Mlcak

Mechanical and Aerospace Engineering Theses - Archive

This study examines the effect of the Thermally Conductive Micro-porous Coating (TCMC) developed at the University of Texas at Arlington, on an extended length heater in flow boiling. The study was performed with application to heat transfer in a tankless hot water heater in mind. The coating is composed of copper particles of micron size soldered to each other and to the substrate. The optimal TCMC (75µm particles with a thickness of 425µm±25µm) was first determined from pool boiling tests. The coating was then tested in flow boiling utilizing tap water as the working fluid at two different levels of …

Thermo-Mechanical Analysis Of A 3d Package In Microelectronics And Cooling Technologies For An Igbt Thermal Tester In Power Electronics, Abhilash Ramachandran Menon

Mechanical and Aerospace Engineering Theses - Archive

In the past, compact components such as chip scale packages and flip chip packages were the work horses of miniaturization. However emerging applications are now demanding even higher packaging density which has led to the evolution of 3D packaging, some of the advantages being minimal conductor length, reduce speed limiting inter chip interconnects. This has resulted in the emergence of 3D packaging technologies like stacked package, through silicon vias (TSV), package on package (PoP) etc. In order to address the various challenging requirements, PoP is seen as the leading 3D packaging platform by the system designers and semiconductor suppliers. PoP …

Buckling And Post Buckling Of Structural Components, Shruti Deshpande

Mechanical and Aerospace Engineering Theses - Archive

Structural members and components, such as shells and trusses of different geometries, form the intricate and deep seated parts in the manufacturing of missiles submarines, rockets, airplanes, automobiles etc and find applications in civil structures such as bridges. These members are comprised of components like conical frusta, cylindrical panels and shallow trusses. In many cases, the sole purpose of such shell structures is to absorb the energy generated due to impact which means, that these structures are subjected to heavy loads and can experience failure due to buckling. The objective of this work is to study the buckling and post …

Aerodynamic Shape Optimization Of 3d Gas Turbine Blade Using Differerential Evolution Method, Darshak Joshi

Mechanical and Aerospace Engineering Theses - Archive

This paper outlines the aerodynamics shape optimization process of a 3D VKI gas turbine blade using Computational Fluid Dynamics (CFD) and differential evolution optimization method. The main objective of this work is to improve outlet total pressure for better aerodynamic performance. This benefit is achieved by optimizing the stacking line path of the turbine blade in 3D annular cascade for which higher exit total pressure is achieved. The optimization process starts with generating a 3D annular cascade with a boundary domain and meshing it using GAMBIT and is then solved in FLUENT using viscous flow analysis. The original stacking line …

Simulation Of Indeterminate Multi-Point Impact And Contact With Friction, Adrian Rodriguez

Mechanical and Aerospace Engineering Theses - Archive

This work presents a method for determining the post-impact behavior of a rigid-body undergoing simultaneous, multiple impacts with friction. A discrete algebraic model is used with an event-driven function which finds impact events. In this work, the indeterminate nature of the equations of motion encountered at impact are examined. A velocity constraint is developed based on the rigid-body assumption to address the equations and an impact law is used to determine the impulsive forces. The slip-state of each contact point is then determined and appropriate methods are used to resolve the post-impact velocities. Friction is treated as a complementarity problem …

Reanalysis For Static And Steady State Structure Response, Kunal Rohit Parikh

Mechanical and Aerospace Engineering Theses - Archive

Reanalysis of a structure has become very important in structural analysis, as it reduces the cost and the computational time required to measure the response of the structure after it has been modified. As the importance of reanalysis has become clear, more and more research has been carried out in the field of reanalysis, which has lead to many different methods to carry out reanalysis. There are various methods which can be used for any single structural reanalysis problem and it would give us different results depending upon the method selected. Due to lot of methods which are available to …

Richtmyer-Meshkov Instability In Reactive Mixtures., Madhuri Ungarala

Mechanical and Aerospace Engineering Theses - Archive

This research analyzes the effect of reactivity on the Richtmyer-Meshkov instability with particular emphasis on the velocity and wave number scaling and on the effect of free detonation instability modes on the interface corrugation rate. This analysis is performed by solving numerically for the first order perturbation generated by the shock-induced acceleration of an initially corrugated interface. The objective of this research is to analyze the effect of mixture reactivity on the process supported by a shock sweeping across a corrugated interface from high density to low density fluid. This scenario is antithetical to the classical Richtmyer analysis where transmitted …

Analysis Of Thrust Development In A Pulse Detonaton Engine, Kishore Nekkanti

Mechanical and Aerospace Engineering Theses - Archive

Pulse detonation engines (PDE) employ detonation waves to compress and burn the fuel and oxidizer mixture which results in the release of high pressure and temperature. The objective of the present study is to analytically model the PDE cycle and to study the pressure, temperature, velocity and density distributions during the Taylor rarefaction wave, reflected rarefaction wave and the blow down process. A two-dimensional supersonic nozzle is designed analytically by using the method of characteristics. The average values of nozzle thrust for one PDE cycle are calculated analytically using the impulse function and thrust coefficient. The variation of PDE thrust …