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Mechanical Engineering Commons™

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2003

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Articles 301 - 313 of 313

Full-Text Articles in Mechanical Engineering

Thermohydrodynamic Analysis Of Compressible Gas Flow In Compliant Foil Bearings, Zhengchun Peng Jan 2003

Thermohydrodynamic Analysis Of Compressible Gas Flow In Compliant Foil Bearings, Zhengchun Peng

LSU Master's Theses

This thesis deals with the development of mathematical models and numerical schemes for simulating the hydrodynamic pressure and temperature rise of compliant foil bearings lubricated by a thin gas film in between its compliant bearing surface and the rotating shaft. The model accounts for the compressibility of gas, the compliance of the bearing surface, and the interaction between the pressure field and temperature field of the gas film in the bearing system. Numerical solutions obtained over a fairly large range of operating speeds show excellent agreement with existing experimental data from both load performance test and bearing temperature measurement. A …

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The Rapid Template Fabrication Process For Producing A Liga Heat Exchanger Bonded To A Mechanical Seal, Jason Patrick Tuma Jan 2003

The Rapid Template Fabrication Process For Producing A Liga Heat Exchanger Bonded To A Mechanical Seal, Jason Patrick Tuma

LSU Master's Theses

Mechanical seals are widely used in the chemical processing, aerospace, and automotive, industries. When a mechanical seal fails, considerable cost is typically involved in replacing the seal. Most seal failures are a result of high temperatures generated by frictional heating. Effectively removing the heat generated would significantly increase the mechanical seal’s work life and lead to significant monetary savings. One method of removing the heat generated is bonding an effective LIGA micro heat exchanger to the mechanical seal and forcing coolant through the heat exchanger. Previous work on this subject revealed promising results, especially for micro heat exchangers with microstructures …

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Structure And Mechanical Properties Of Ti-Si-N Coatings, Xiaodong Zhang Jan 2003

Structure And Mechanical Properties Of Ti-Si-N Coatings, Xiaodong Zhang

LSU Master's Theses

In order to better define conditions under which ~{!0~}super-strengthening~{!1~} occurs in the Ti-Si-N system, we performed detailed experimental studies on how the structure and mechanical properties of Ti-Si-N coatings are influenced by the deposition temperature. Different series of Ti-Si-N specimens were prepared in an inductively coupled plasma (ICP)-assisted reactive sputtering system at both low and high temperatures. Coating compositions were measured by Rutherford backscattering spectrometry (RBS) technique, surface roughness was examined on an atomic force microscope (AFM), coating thicknesses were obtained by performing cross-sectional scanning electron microscopy (SEM), and their structure examined with transmission electron microscopy (TEM). Vibrational frequency results …

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Precipitate Growth Features In The Duplex Size Gamma Prime Distribution In The Superalloy In738lc, Indranil Roy Jan 2003

Precipitate Growth Features In The Duplex Size Gamma Prime Distribution In The Superalloy In738lc, Indranil Roy

LSU Master's Theses

IN738LC is a modern, nickel base superalloy utilized at high temperatures in aggressive environments. Durability of this superalloy is dependent on the retention of strengthening by Gamma Prime precipitates. The precipitate growth features in the duplex size (fine and coarse) precipitate distribution was studied by heating the alloy for various times in vacuum at selected temperatures in the range 800 °C to 1100 °C. Increasing the holding times from 1 hour to 100 hours shows joining of the fine particles to form bigger particles, leading to distinct raft patterns. Two different Gamma Prime precipitate growth processes had been observed: merging …

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Minimization Of Power Losses In Active Magnetic Bearing Control, Nader Motee Jan 2003

Minimization Of Power Losses In Active Magnetic Bearing Control, Nader Motee

LSU Master's Theses

A solution to the problem of AMB control with reduced electrical power losses will be presented in this thesis. The proposed control solution will be founded on the integrator backstepping technique, which decouples the rotor stabilization problem from the bias flux design problem. It further allows for the easy redesign of the control law to compensate for uncertainties in the AMB system. A class of nonlinear controllers will be developed that reduces the AMB power losses in comparison to standard fixed-bias controllers, while containing no control singularity. Control laws will be presented for the standard AMB operating mode where both …

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An Experimental Investigation Of Whirl Instability Including Effects Of Lubricant Temperature In Plain Circular Journal Bearings, Darryl, Jr. Chauvin Jan 2003

An Experimental Investigation Of Whirl Instability Including Effects Of Lubricant Temperature In Plain Circular Journal Bearings, Darryl, Jr. Chauvin

LSU Master's Theses

The purpose of this thesis is to experimentally investigate the effect of lubricant temperature on the presence of whirl instability in journal bearings. The first set of conditions that are studied is an extremely low eccentricity rotor and the occurrence of oil whirl at the start-up of the experiment. Lubricant temperature, bearing temperature, frequency and amplitude of vibration, and rotational speed are monitored and analyzed in relation to presence of whirl instability. Additionally, another rotor with a slightly higher eccentricity is tested with respect to the presence of such instability. Particularly with this rotor, the system is brought just below …

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Evaluation Of Fire-Fighting Helmet Surface Technology For High Radiant Heat Applications, David L. Barnett Jan 2003

Evaluation Of Fire-Fighting Helmet Surface Technology For High Radiant Heat Applications, David L. Barnett

University of Kentucky Master's Theses

Protective helmets used by fire-fighters must be designed to minimize the amount of heat transferred to the users head while providing durability, comfort, and affordable costs. This thesis highlights the evaluation of new helmet technology specifically tailored to high radiant heat environments to advance the state-of-the-art in head protection for this application. The research focused on the assessment of the outer shells of helmets and the properties of the surfaces. The development included the evaluation of radiation heat transfer, in a laboratory environment, to various helmet shell surface constructions. Industry standards were considered, and critiqued. Experiments were designed to isolate …

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Experimental Investigation Of Separation In A Low Pressure Turbine Blade Cascade Model, Brian Hollon Jan 2003

Experimental Investigation Of Separation In A Low Pressure Turbine Blade Cascade Model, Brian Hollon

University of Kentucky Master's Theses

The flow field around a low pressure turbine blade is examined using smoke-wire flow visualization, static surface pressure measurements, and particle image velocimetry (PIV). The purpose of the experimental study is to investigate the transition and separation characteristics on low pressure turbine blades under low Reynolds number (Re) and varying freestream turbulence intensity (FSTI). A cascade model consisting of 6 Pratt andamp; Whitney PAK-B low pressure turbine blades was examined in a wind tunnel using PIV and flow visualization. Smoke-wire visualization was performed for test section exit angles of 93°, 95°, and 97°, in the range Re = …

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Measurements In A Rotating Serpentine Duct With Multiple Rib Arrangements, Rahul Bharadwajh Jan 2003

Measurements In A Rotating Serpentine Duct With Multiple Rib Arrangements, Rahul Bharadwajh

University of Kentucky Master's Theses

The effect of rotation on flow in a gas turbine blade cooling duct model is investigated experimentally. The present work consists of velocity measurements at different locations in a test section with a 180° bend with ribs on one wall. Three geometric rib parameters are considered; rib-rib spacing, rib orientation angle and rib blockage ratio. PIV is used for flow visualization and analysis. Along with the clean duct measurements, ribs with blockage ratios, b/h, of 0.25 and 0.125 were considered. The b/h = 0.25 cases have been comprehensively analyzed while the b/h = 0.125 cases have been studied at …

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Study Of The "Poor Man's Navier-Stokes" Equation Turbulence Model, Stewart Andrew Bible Jan 2003

Study Of The "Poor Man's Navier-Stokes" Equation Turbulence Model, Stewart Andrew Bible

University of Kentucky Master's Theses

The work presented here is part of an ongoing effort to develop a highly accurate and numerically efficient turbulence simulation technique. The paper consists of four main parts, viz., the general discussion of the procedure known as Additive Turbulent Decomposition, the derivation of the "synthetic velocity" subgrid-scale model of the high wavenumber turbulent fluctuations necessary for its implementation, the numerical investigation of this model and a priori tests of said models physical validity. Through these investigations we have demonstrated that this procedure, coupled with the use of the "Poor Mans Navier-Stokes" equation subgrid-scale model, has the potential to be …

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Predictions For Multi-Scale Shock Heating Of A Granular Energetic Material, Venugopal Jogi Jan 2003

Predictions For Multi-Scale Shock Heating Of A Granular Energetic Material, Venugopal Jogi

LSU Master's Theses

This thesis addresses the multi scale heating of a granular energetic solid due to shock loading. To this end, an existing mathematical model that has been used to predict low pressure bulk and localized heating of the granular high-explosive HMX ([CH2NNO2]4) is extended to account for compressibility and melting of the pure phase solid. Dense granular HMX has a heterogeneous structure composed of randomly packed small grains (average size ~ 100 µm) having a free-pour density that is approximately 65% of the pure phase solid density. The shock loading response of this material is …

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Evaluation Of Mechanical Fitness For Service Of High Temperature Hydrogen Attacked Steels, Brent Matthew Saba Jan 2003

Evaluation Of Mechanical Fitness For Service Of High Temperature Hydrogen Attacked Steels, Brent Matthew Saba

LSU Master's Theses

A novel approach is introduced in evaluating one of industry’s most complex corrosion phenomena, high temperature hydrogen attack (HTHA). Limited efforts have been made by industry to address this degradation mechanism and even less data are available to properly utilize their evaluation techniques. The predominant fracture mechanics based analysis of HTHA relies on Charpy V-Notch (CVN) impact test data. In the face of limited CVN test data, accurate results are shaky at best. The HTHA evaluation set forth in this paper combines the analysis tools of plastic collapse and both static and dynamic fracture mechanics. The first condition addresses plastic …

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A Disjoining Pressure For Small Contact Angles And Its Applications, Qingfang Wu Jan 2003

A Disjoining Pressure For Small Contact Angles And Its Applications, Qingfang Wu

LSU Master's Theses

A thin liquid film experiences additional intermolecular forces when the film thickness h is less than roughly 100 nm. The effect of these intermolecular forces at the continuum level is captured by the disjoining pressure . Since dominates at small film thicknesses, it determines the stability and wettability of thin films. To leading order, a thin film can be treated as uniform and . This form, however, cannot be applied to films with non-zero contact angles. A recent ad-hoc derivation to include the slope leads to a that allows a contact line to move without slip. This work derives a …

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