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Full-Text Articles in Mechanical Engineering

A Vacuum Four-Ball Tribometer To Evaluate Liquid Lubricants For Space Applications, Masabumi Masuko, William R. Jones Jr, Ralph Jansen, Ben Ebihara, Stephen V. Pepper, Larry S. Helmick Jul 1993

A Vacuum Four-Ball Tribometer To Evaluate Liquid Lubricants For Space Applications, Masabumi Masuko, William R. Jones Jr, Ralph Jansen, Ben Ebihara, Stephen V. Pepper, Larry S. Helmick

Science and Mathematics Faculty Publications

The design and operation of a vacuum tribometer, based on the four-ball configuration, is described. This tribometer evaluates the tribological characteristics of liquid lubricants for space applications. Operating conditions include: room temperature, loads to approximately 1000N, speeds to approximately 500 rpm, and pressures of approximately 10(exp -6)Pa. Tests can also be run at atmospheric pressure with air or nitrogen. Some typical test results are included.


Studies On Nonequilibrium Phenomena In Supersonic Chemically Reacting Flows, Rajnish Chandrasekhar Jul 1993

Studies On Nonequilibrium Phenomena In Supersonic Chemically Reacting Flows, Rajnish Chandrasekhar

Mechanical & Aerospace Engineering Theses & Dissertations

This study deals with a systematic investigation of nonequilibrium processes in supersonic combustion. The two-dimensional, elliptic Navier-Stokes equations are used to investigate supersonic flows with nonequilibrium chemistry and thermodynamics, coupled with radiation, for hydrogen-air systems. The explicit, unsplit MacCormack finite-difference scheme is used to advance the governing equations in time, until convergence is achieved.

For a basic understanding of the flow physics, premixed flows undergoing finite rate chemical reactions are investigated. Results obtained for specific conditions indicate that the radiative interactions vary substantially, depending on reactions involving HO$\sb2$ and NO species, and that this can have a noticeable influence ...


Structure Characterization With Thermal Wave Imaging, Kurt Bryan Jan 1993

Structure Characterization With Thermal Wave Imaging, Kurt Bryan

Review of Progress in Quantitative Nondestructive Evaluation

Thermal imaging is a technique of recent interest for the nondestructive evaluation of materials. This method attempts to characterize the internal structure of a sample (perhaps to locate flaws-cracks, bubbles, corrosion, etc.) by using its surface temperature response to an external heating. Some recent work on this subject is detailed in [2], [3], [4] and [6].


Dual-Band Infrared Imaging Applications: Locating Buried Minefields, Mapping Sea Ice And Inspecting Aging Aircraft, Nancy Del Grande, Philip F. Durbin, Dwight E. Perkins Jan 1993

Dual-Band Infrared Imaging Applications: Locating Buried Minefields, Mapping Sea Ice And Inspecting Aging Aircraft, Nancy Del Grande, Philip F. Durbin, Dwight E. Perkins

Review of Progress in Quantitative Nondestructive Evaluation

We discuss the use of dual-band infrared (DBIR) imaging for three quantitative NDE applications: locating buried surrogate mines, mapping sea ice thicknesses and inspecting subsurface flaws in aging aircraft parts. Our system of DBIR imaging offers a unique combination of thermal resolution, detectability, and interpretability. Pioneered at Lawrence Livermore Laboratory, it resolves 0.2 °C differences in surface temperatures needed to identify buried mine sites and distinguish them from surface features. It produces both surface temperature and emissivity-ratio images of sea ice, needed to accurately map ice thicknesses (e.g., by first removing clutter due to snow and surface roughness ...


Photothermal Measurement Of Metal Film Thickness In Integrated Circuit Devices, Xioa-Dung Wu, Gordon S. Kino Jan 1993

Photothermal Measurement Of Metal Film Thickness In Integrated Circuit Devices, Xioa-Dung Wu, Gordon S. Kino

Review of Progress in Quantitative Nondestructive Evaluation

Metal films have been used extensively in very-large-scale integration (VLSI) devices. They are used to build interconnects, field-effect transistor gates, diffusion barriers, and conduction pads for input or output leads. Metals such as aluminum, tungsten, titanium and platinum are deposited on an insulating layer [1,2]. The metal film thicknesses range from 100 Å to 1 µm. Due to the ever-growing need for high speed, high density, and low power dissipation in integrated circuit (IC) technology, accurate control of the metallization process becomes essential to ensure the quality and yield of the final product. One of the important parameters in ...


Thermal Wave Detection And Analysis Of Defects In Structural Composite Materials, D. Crowther, L. D. Favro, P.-K. Kuo, R. L. Thomas Jan 1993

Thermal Wave Detection And Analysis Of Defects In Structural Composite Materials, D. Crowther, L. D. Favro, P.-K. Kuo, R. L. Thomas

Review of Progress in Quantitative Nondestructive Evaluation

One criticism which can be leveled at thermal wave images is that their resolution is often less than that of the very best ultrasonic images of similar targets. This reduction of the resolution arises from the transverse diffusion of heat in the thermal waves reflected from the subsurface defects in the sample. In this paper we describe a technique for removing the blurring of pulsed thermal wave images of planar defects through the reconstruction of the shape of the scatterer by use of inverse scattering techniques. Although the method at present is restricted to planar defects, this special class of ...


Thermal Method For Depth Of Damage Determination In Insulating Materials, P. Howell, K. Elliott Cramer, William P. Winfree Jan 1993

Thermal Method For Depth Of Damage Determination In Insulating Materials, P. Howell, K. Elliott Cramer, William P. Winfree

Review of Progress in Quantitative Nondestructive Evaluation

Impact damage often may produce little visible surface damage, yet extensive subsurface delaminations, greatly reducing the load carrying capacity of the composite part [1]. For large composite structures typical of aerospace applications, thermal NDE techniques have been shown to provide quantitative information regarding the area and depth of hidden damage in composite samples [2] [3]. For a quantitative assessment of damage, where a noncontacting method capable of imaging large areas at a time is required, thermal techniques have some advantages.


On Characterizing Operating Conditions Of Ultrasonic Systems Using Mtf And Related Techniques, R. Zilber, K. Shiloh Jan 1993

On Characterizing Operating Conditions Of Ultrasonic Systems Using Mtf And Related Techniques, R. Zilber, K. Shiloh

Review of Progress in Quantitative Nondestructive Evaluation

For a given sample under test, the quality of the ultrasonic image obtained by scanning is greately influenced by the choice of the equipment as well as by the operating conditions. The possibilities of choosing the different parameters is very wide, even if the basic ultrasonic system is determined. The parameters to select before starting an experiment include the transducer itself, its position relative to the sample, the different settings such as gain, attenuation and damping, the mode of detection, etc. The selection is usually dictated by qualitative indications which can be inaccurate or even misleading. Consequently it is very ...


A Model Of Coal Combustion Dynamics In A Fluidized Bed Combustor , Kenneth William Junk Jan 1993

A Model Of Coal Combustion Dynamics In A Fluidized Bed Combustor , Kenneth William Junk

Retrospective Theses and Dissertations

A model of coal combustion dynamics in a fluidized bed is developed in this study. The model is carried out on the premise that the total combustion response can be decomposed into two distinct processes: volatile combustion and char combustion. For an impulse in the feed rate of coal, the transient response of volatile combustion is modeled as an exponential decay. In contrast with volatile combustion, the transient response of char combustion cannot be approximated by an exponential decay. Instead, the transient response of char combustion is based on a closed-form solution to a population balance equation. This solution is ...


Visualizing Thermodynamic Stability And Phase Equilibrium Through Computer Graphics , Daniel Charles Coy Jan 1993

Visualizing Thermodynamic Stability And Phase Equilibrium Through Computer Graphics , Daniel Charles Coy

Retrospective Theses and Dissertations

In a landmark paper, J. W. Gibbs introduced a fundamental thermodynamic surface for pure materials and, later, expanded that analysis to mixtures. While Gibbs certainly had images of these surfaces in his mind, he described them in words rather than drawings. Since Gibbs time, a number of researchers have produced representations of these surfaces, but their studies have been limited because of the difficulty of creating and visualizing the data sets required. In this work, computer graphics has been used to visualize a variety of these models for pure, binary, and ternary systems;Fundamental-equation surfaces produced from Legendre transforms of ...


Determining Char Burning And Sulfur Sorption Rates From Dynamic Analysis Of Co2 And So2 Profiles , Nearchos J. Christofides Jan 1993

Determining Char Burning And Sulfur Sorption Rates From Dynamic Analysis Of Co2 And So2 Profiles , Nearchos J. Christofides

Retrospective Theses and Dissertations

This work introduces a method for determining coal devolatilization, char burning, limestone calcination, and sulfur sorption rates based on the analysis of CO[subscript]2 and SO[subscript]2 profiles from a fluidized bed combustor. The technique is non-intrusive and can be performed under realistic combustion conditions. The method involves batching coal or limestone samples in a fluidized bed heated with propane gas or other fuel. Carbon dioxide and sulfur dioxide profiles are analyzed with linear models to obtain characteristic time constants for coal devolatilization, char burning, and sulfur sorption. Time constants for coal devolatilization and char burning can be ...


Carbon In Fly Ash Analysis Using Photoacoustic Spectroscopy , Jeffrey Raymond Dykstra Jan 1993

Carbon In Fly Ash Analysis Using Photoacoustic Spectroscopy , Jeffrey Raymond Dykstra

Retrospective Theses and Dissertations

Photoacoustic absorption spectroscopy (PAS) was investigated as a method for on-line monitoring of carbon in fly ash from coal-fired boilers. PAS is based on the periodic heating of a gas when amplitude-modulated radiation is absorbed by the gas or by particles suspended in the gas. This periodic heating produces an acoustical wave that can be detected by a microphone. Because the PAS signal is based solely on the absorption of radiation (by carbon) and not scattering of radiation (by mineral matter), it has the potential for distinguishing unburned carbon from mineral matter suspended in the flue gas. Two radiation sources ...