Engineering Commons^™

Method Of Making Quasicrystal Alloy Powder, Protectivecoatings And Articles, Jeffrey E. Shield, Alan I. Goldman, Iver E. Anderson, Timothy W. Ellis, R. William Mccallum, Daniel J. Sordelet

Department of Mechanical and Materials Engineering: Faculty Publications

A method of making quasicrystalline alloy particulates wherein an alloy is superheated and the meltis atomized to form generally spherical alloy particulates free of mechanical fracture and exhibiting a predominantly quasicrystalline in the atomized condition structure. The particulates can be plasma sprayed to form a coating or consolidated to form an article of manufacture.

Numerical Investigation Of Shock-Induced Combustion Past Blunt Projectiles, Jagjit K. Ahuja

Mechanical & Aerospace Engineering Theses & Dissertations

A numerical study is conducted to simulate shock-induced combustion in premixed hydrogen-air mixtures at various free-stream conditions and parameters. Two-dimensional axisymmetric, reacting viscous flow over blunt projectiles is computed to study shock-induced combustion at Mach 5.11 and Mach 6.46 in hydrogen-air mixture. A seven-species, seven reactions finite rate hydrogen-air chemical reaction mechanism is used combined with a finite-difference, shock-fitting method to solve the complete set of Navier-Stokes and species conservation equations. In this approach, the bow shock represents a boundary of the computational domain and is treated as a discontinuity across which Rankine-Hugoniot conditions are applied. All interior details of …

Studies Of Mixing Processes In Gases And Effects On Combustion And Stability, Frank Paul Kozusko Jr.

Mathematics & Statistics Theses & Dissertations

Three physical models of laminar mixing of initially separated gases are studied. Two models study the effects of the mixing dynamics on the chemical reactions between the gases. The third model studies the structure and stability of a laminar mixing layer in a binary gas. The three models are:

1. Two ideal and incompressible gases representing fuel and oxidizer are initially at rest and separated across an infinite linear interface in a two dimensional system. Combustion, expected as the gases mix, will lead to a rapid rise in temperature in a localized area, i.e. ignition. The mixing of the gases …

On The Reuse Of Bolts Which Have Been Torqued To Yield, Dal B. Lee, Joseph Foyos, Martin L. Smith, Omar S. Es-Said, Otto Kossuth

Mechanical Engineering Faculty Works

Bolts are torqued to yield in automotive engines to fasten aluminum alloy cylinder heads to cast iron cylinder blocks. This tightening method provides a reliable, even, and controllable clamping force that prevents warping of the soft cylinder head and ensures a leak-tight joint. It has one drawback: Since the bolts yield during engine assembly, they work harden even as their ultimate strength decreases. Upon reuse, yield stress more closely approaches ultimate strength. Fastener geometry and mechanical properties, now changed, supply changed joint-clamping force. For reasons such as these. Ford Motor Company recommends that bolts torqued to yield be replaced each …

Nonlinear Transient Thermal Analysis By The Force-Derivative Method, Narayani V. Balakrishnan

Mechanical & Aerospace Engineering Theses & Dissertations

The force-derivative method (FDM) represents a series of higher-order modal methods which offer an increasingly improved approximation of the higher modes neglected in the basic mode-displacement method (MDM). The FDM includes additional terms which involve the forcing function and derivatives of the forcing function with respect to time. The mode-acceleration method (MAM), extensively used in structural analysis, is a first-order form of the FDM which includes only one correction term that depends on the forcing function itself. The success of the FDM in many structural dynamic applications has prompted its application for solving transient thermal problems. The superior convergence of …

Dynamic Unstructured Method For Prescribed And Aerodynamically Determined Relative Moving Boundary Problems, Kamakhya Prasad Singh

Mechanical & Aerospace Engineering Theses & Dissertations

A new methodology is developed to simulate unsteady flows about prescribed and aerodynamically determined moving boundary problems. The method couples the fluid dynamics and rigid-body dynamics equations to capture the time-dependent interference between stationary and moving boundaries. The unsteady, compressible, inviscid (Euler) equations are solved on dynamic, unstructured grids by an explicit, finite-volume, upwind method. For efficiency, the grid adaptation is performed within a window around the moving object. The Eulerian equations of the rigid-body dynamics are solved by a Runge-Kutta method in a non-inertial frame of reference. The two-dimensional flow solver is validated by computing the flow past a …

Circulation Measurements About A Rapidly Pitching Airfoil Using An Ultrasonic System, F. J. Weber, Jr., William W. Durgin, H. Johari

Office of the Provost Scholarship

An ultrasonic system was developed to measure the circulation about a sinusoidally pitching NACA 4418 airfoil. The system consisted of two opposing ultrasonic ranging modules arranged such that the differences between the sound propagation times in opposite directions could be related to the instantaneous circulation. For the stationary airfoil, the measured lift coefficient was within 5% of the tabulated data while the observed stall angle was 2° less than the tabulated value. Measured hysteresis loops verified the applicability of the ultrasonic system to the dynamic stall problem. Measured maximum lift coefficients increased linearly with reduced frequency up to a value …

Field Commissioning Of A Daylight-Dimming Lighting System, Florida Solar Energy Center, David Floyd

FSEC Energy Research Center®

An Elementary School cafeteria in Florida was commissioned with a fluorescent lighting system that dims in response to available daylight. The lighting system's performance and commissioning aspects were evaluated through real time measurement of lighting and air conditioning power, work plane illumination, and interior/exterior site conditions. The new system produced a 27% reduction in lighting power due to dimming. Lower than expected dimming system performance was observed prior to effective commissioning. Difficulties encountered are discussed as well as recommendations for performance improvements.

Photovoltaic Applications For Disaster Relief. 11-95. Copies 1, 2&3., Florida Solar Energy Center, William Young

FSEC Energy Research Center®

No abstract provided.

A Comparative Study Of The Stress Concentration Factors Arising Between Two Equal, Nearly Intersecting, Perpendicular, Pressurized Holes In An Infinite Solid With Those Arising Due To An Infinite Series Of Such Holes, Paul J. Drogowski

Masters Theses

Finite element analysis is used to determine the stress concentration factors arising from two equal, perpendicular, nearly intersecting, pressurized holes in an infinite solid while varying the distance and pressure ratios between the holes. The results are compared and contrasted with those previously obtained for an infinite series of such holes. A ratio of the distance between the holes to the diameter of the holes at which the holes can be considered to be single holes in an infinite solid is determined. A study is performed to determine a correlation between the location of the region of maximum stress and …

Design And Development Of Microswitches For Micro-Electro-Mechanical Relay Matrices, Mark W. Phipps

Theses and Dissertations

Many different micro-electro-mechanical switches were designed in the Multi-User MEMS processes (MUMPs) and deep x-ray lithography and electroforming (LIGA) processes. The switches were composed of actuators that operated based upon either electrostatic forces or thermal forces. A thermally activated beam flexure actuator that operated based upon differential heating was used extensively. This actuator, which was fabricated in the MUMPs process, was able to deflect up to 12 microns with a total input power of less than 25 mW. The thermal resistance, which was needed to model this actuator, was determined from a material constant, 1.9 ± 0.08 m^1.5-°C-W …

Effects Of Blowing Ratios On Heat Transfer To The Throat Region Of A Porous-Walled Nozzle, Fu-Jung Chen

Theses and Dissertations

The effects of transpiration cooling on heat transfer in the throat region of a porous-walled nozzle were investigated. The experiments were performed in the AFIT low speed shock tube fitted with a Mach 2 nozzle. A blowing region was limited to the area from 1.3 cm prior to the throat to 1.2 cm downstream of the throat. The blowing ratios from -0.0002 (suction) to 0.0117 (blowing) of the main stream flow were studied. Heat flux data were taken from both sides of the nozzle. One side was transpiration cooled by secondary air injection through a porous wall, while the other …

Time Dependence Of Multiply Scattered Diffuse Ultrasound In Polycrystalline Media, Joseph A. Turner, Richard L. Weaver

Department of Engineering Mechanics: Faculty Publications

Time domain results are presented for the multiply scattered longitudinal intensity backscattered from a polycrystalline medium. The results are solutions to the ultrasonic radiative transfer equation (URTE), the derivation of which is based upon radiative transfer theory. Unlike steady-state solutions obtained previously, time domain solutions will more closely correspond to experiments that use tone burst sources. This paper is concerned with the time dependence of the backscattered longitudinal intensity from a polycrystalline medium excited by a normally incident longitudinal wave idealized as an impulsive deposition of energy. It is shown that multiple scattered effects become significant at times on the …

First Line Supervisor Perceptions: The Effectiveness Of Specific Safety Training Materials, Cynthia Houlson

Graduate Research Papers

The problem of this study was to determine whether first line supervisors, who have been exposed specifically to Safety Focus Topics, perceived them as an effective tool in filling their role as a safety trainer.

Relationship Of The Second Order Nonlinear Optical Coefficient To Bandgap In Inorganic Non-Centrosymmetric Crystals, A. G. Jackson, M. Ohmer, S. R. Leclair

Mechanical and Materials Engineering Faculty Publications

The purpose of this paper, is to provide a means of estimating and comparing the wavelength conversion efficiency (figure of merit, FOM) of new nonlinear materials knowing only their bandgap. The approach for the estimates is trend analysis of existing data^1-28 for the second order nonlinear coefficient, x⁽²⁾ijk, or d_ij =x⁽²⁾ijk^/2, the index of refraction n, and the bandgap E. No underlying physical basis for the result will be presented. The result of this trend analysis, in the form of plots of x⁽²⁾ vs E and FOM vs E …

Advanced Rover Chassis, Eric Alan Poulson, Collin Lewis, Todd Graves

Undergraduate Honors Capstone Projects

Background:

The six wheeled rover vehicle detailed in this design is intended as an upgrade test bed for the sensor array and autonomous navigation algorithms in use by Utah State University's Center for Self-Organizing and Intelligent Systems (CSOIS). The CSOIS's sensor suite can successfully detect and avoid unnavigable obstacles up to five vehicle lengths in front of the vehicle. The center presently uses a modified RC type chassis and only supports two wheel drive. This chassis was adequate to bring the CSOIS's algorithms to a proof-of-principles state, but in order to place the system in any practical application, a full …

Tractor Test Museum Committee Minutes April 21, 1995, Tractor Museum

Lester F. Larsen Tractor Museum: Planning and Development Documents

Hitchcock Foundation Potential Committee Member Tree Removal

Assessment Of Infiltration Practices In The Florida Energy Code, Florida Solar Energy Center, James Cummings

FSEC Energy Research Center®

The Florida Department of Community Affairs has contracted with the Florida Solar Energy Center (FSEC) to review the current infiltration practices of the Florida Energy Code to determine, based on analysis of the best currently available infiltration data, whether there is need for three infiltration practices, and to make recommendations of what "point multipliers" should be applied to the infiltration practice(s). An advisory committee of industry, utility, and research representatives was formed to review the findings of the project and express opinions about the form the infiltration practices should take. This committee met twice, reviewed each of the reports produced …

Comparison Of Rapid Prototyping Systems For Implementation Into The Product Development Cycle, Daniel S. Koenig

Graduate Research Papers

The problems with the implementation and use of RP technology is choosing the best system from the fifteen or more RP systems commercially available and more than 20 other systems under development throughout the world (Wohlers, 1993). The problem of this study was to evaluate each of six preselected RP systems based on key characteristics. This study provides pertinent data so that those teams and individuals involved in the implementation and the use of a RP process can make sound decisions.

Reduced Small Engine Emissions With Perforated Plates, Derek S. Lindsay

Honors Capstone Projects and Theses

No abstract provided.

Ole Miss Engineer 1995

Ole Miss Engineer

No abstract provided.

A New Spray Evaporation Model Based On Droplet Interface Phenomena, Nihad E. Daidzic, Gangolf Kohnen, Martin Sommerfeld

Aviation Department Publications

In this work the influence of droplet shape oscillations on droplet evaporation is shown. Through nonlinear mode interactions, turbulence and aerodynamic triggering of vibrations cause by vortex shedding, droplets always oscillates in spray flows. Droplet shape oscillation cause higher evaporation rates through several physical phenomena such as an average increase of the superficial surface area, periodic micro-convection and boundary layer destruction, and local saturation pressure changes due to local curvature effects. The inviscid theory of small-amplitude droplet oscillations was used which resulted in better agreement with the measurement data of droplet size distributions in sprays for different axial coordinates.

An Analysis Of The Disposition Of Used Foundry Sand With Thermal Reclamation, Douglas Miller

Graduate Research Papers

The purpose of this study was to identify the economic and environmental concerns for the disposal, reuse, or reclamation of used foundry sand and show how foundries have developed options to landfills. The sand type and the reclamation processes available are the factors to use in determining whether disposal, reuse, or reclamation is appropriate. The continued use of landfills for disposal of used sand strongly indicates that reclamation and reuse techniques were either not understood or not as economical as disposal. Public concerns and new environmental laws demand that alternate means of disposal for used foundry sand should be developed …

Aerodynamic Design Optimization With Consistently Discrete Sensitivity Derivatives Via The Incremental Iterative Method, Vamshi M. Korivi

Mechanical & Aerospace Engineering Theses & Dissertations

In this study which involves advanced fluid-flow codes, an incremental iterative formulation (also known as the "delta" or "correction" form), together with the well-known spatially split approximate-factorization algorithm, is presented for solving the large, sparse systems of linear equations that are associated with aerodynamic sensitivity analysis. For the smaller two dimensional problems, a direct method can be applied to solve these linear equations in either the standard or the incremental form, in which case the two are equivalent. However, iterative methods are needed for larger two-dimensional and three dimensional applications because direct methods require more computer memory than is currently …

Non-Linear Boundary-Layer Receptivity Due To Distributed Surface Roughness, Tahani R. Amer

Mechanical & Aerospace Engineering Theses & Dissertations

The process by which a laminar boundary layer internalizes the external disturbances in the form of instability waves is known as boundary-layer receptivity. The objective of the present research was to determine the effect of acoustic excitation on boundary-layer receptivity for a flat plate with distributed variable-amplitude surface roughness through measurements with a hot-wire probe. Tollmien-Schlichting mode shapes due to surface roughness receptivity have also been determined, analyzed, and shown to be in agreement with theory and other experimental work. It has been shown that there is a linear relationship between the surface roughness and receptivity for certain roughness configurations …

Component Mode Synthesis-Based Design Methodology For Structural Modification And Synthesis, Venkateshwarlu Maroju

Mechanical & Aerospace Engineering Theses & Dissertations

In this work, structural modification and synthesis techniques based on component mode synthesis are presented. The component mode synthesis method formulates the eigenvalue equation of an entire structure in terms of the vibration characteristics of individual components in the assembly. Through this functional relationship, the individual components are successfully treated as the design entities in the proposed methodology. Unlike conventional design modification techniques that can only treat the properties of the finite elements as the design variables, this technique uses the vibration and static responses of the individual components as the design entities. The sensitivity derivatives of the global responses …

Finite Element Nonlinear Random Response Of Composite Panels Of Arbitrary Shape To Acoustic And Thermal Loads Applied Simultaneously, Roger R. Chen

Mechanical & Aerospace Engineering Theses & Dissertations

The nonlinear random response of composite plates to the simultaneously applied, combined acoustic/thermal loads are investigated in this dissertation. A finite element formulation for the nonlinear random response is developed. The three-node Mindlin plate element with improved transverse shear is extended and employed. The extension includes the development of the thermal geometric matrix, the mass matrix, the first- order and second-order nonlinear stiffness matrices, and the thermal and mechanical load vectors. An innovative solution procedure has been created which is believed to be the first attempt to analyze nonlinear random response of complex composite panels subjected to simultaneous acoustic and …

Closed-Loop Identification Of Unstable Systems In Time And Frequency Domains, Hyun Chang Lee

Mechanical & Aerospace Engineering Theses & Dissertations

This dissertation presents closed-loop identification algorithms of an unstable system in the time and frequency domains. In the time domain, the projection filter, which is a linear transformation which projects (transforms) a finite number of input-output data of a system into its current space, is used to relate the state-space model with a finite difference model. The method developed can take into account the effects of process noise as well as measurement noise and identify open-loop systems with unknown feedback dynamics in the closed-loop operation. Then the recursive relations between Markov parameters and the ARX model are derived to identify …

Modeling And Simulation Of Load Introduction For Fuselage Crown Panel Testing, Kevin P. Belack

Mechanical & Aerospace Engineering Theses & Dissertations

This paper discusses the mechanism and behavior of load introduction to internally pressurized fuselage crown panels. Emphasis is placed on the finite element modeling of a simulated pressure-box test machine and representative fuselage crown panel. The geometry and mesh requirements for the finite element model are examined through numerical studies which gradually increase in complexity. These numerical studies culminate in the detailed specification of boundary conditions, mesh densities, load introduction mechanisms, element choice and solution process for the simulation of a pressure-box test machine and test panel.

The results obtained using the finite element model are then compared with experimental …

Extension To The Dynamic Modeling Of The Large Angle Magnetic Suspension Test Fixture, Lucas E. Foster

Mechanical & Aerospace Engineering Theses & Dissertations

The Large Angle Magnetic Suspension Test Fixture (LAMSTF) is a laboratory scale proof-of-concept system. The configuration is unique in that the electromagnets are mounted in a circular planar array. A mathematical model of the system had previously been developed, but was shown to have inaccuracies. These inaccuracies showed up in the step responses. Eddy currents were found to be the major cause of the modeling errors. In the original system, eddy currents existed in the aluminum baseplate, iron cores, and the sensor support frame. An attempt to include the eddy current dynamics in the system model is presented. The dynamics …