Engineering Commons^™

Resilient And Residual Properties Of Egyptian Asphalt Concrete, Medhat Habil Shehata

Archived Theses and Dissertations

No abstract provided.

Characterization Of Fatigue Behavior Of 2-D Woven Fabric Reinforced Ceramic Matrix Composite At Elevated Temperature, Daniel J. Groner

Theses and Dissertations

This study investigated the fatigue behavior and associated damage mechanisms in notched and unnotched enhanced Sic-SiC ceramic matrix composite specimens at 1100°C. Stiffness degradation, strain variation, and hysteresis were evaluated to characterize material behavior. Microscopic examination was performed to characterize damage mechanisms. During high cycle-low stress fatigue tests, far less fiber-matrix interface debond was evident than in low cycle-high stress fatigue tests. Notched specimens exhibited minimal stress concentration during monotonic tensile testing and minimal notch sensitivity during fatigue testing. Damage mechanisms were also similar to unnotched.

Fatigue Behavior Of A Cross-Ply Ceramic Matrix Composite Subjected To Tension-Tension Cycling With Hold Time, Scott A. Grant

Theses and Dissertations

This study was carried out to investigate the elevated temperature behavior of the SiC-MAS5 cross- ply [0-90]_4S ceramic matrix composite manufactured by Corning Inc. to fatigue with loading waveforms that combine the characteristics of stress rupture and high cycle fatigue. The test results were compiled in the form of S-N (cycles to failure), S-T (exposure time versus cycles to failure), S-S (energy exposure versus cycles to failure), normalized modulus degradation, strain progression, and hysteresis loop progression. From the mechanical behavior demonstrated by these curves, relationships between the effect of the environment and loading waveform were developed. In addition, a …

Method Of Manufacture Of Multiple-Element Piezoelectric Transducer, Lawrence J. Busse, Jeffry W. Stevenson, Wayne Huebner

Materials Science and Engineering Faculty Research & Creative Works

An improved method for fabrication of a multiple-element piezoelectric transducer and the transducer produced thereby. A green precursor tape is produced by doctor-blade tape-casting of a slurry containing lead zirconate-titanate (PZT) powder. After drying, individual strips of the tape are stacked between flat plates of previously sintered PZT, and sintered to form PZT strips; Pb from the previously sintered PZT plates makes up any Pb lost from the surfaces of the tape strips during sintering. The PZT strips are stacked interposed by layers of a thermoplastic polymer, and heated to a temperature above the melting point of the polymer, forming …

Nature Of The Ferroelectric Phase Transition In Pbtio3, Noam Sicron, B. Ravel, Y. Yacoby, Edward A. Stern, Fatih Dogan, John J. Rehr

Materials Science and Engineering Faculty Research & Creative Works

We have measured quantitatively the temperature dependence of the local distortions of PbTiO3 crystals below and above the structural ferroelectric phase transition, using x-ray absorption fine-structure (XAFS) measurements. Two probe atoms, Pb and Ti, were used. The results were analyzed by fitting parametrized theoretical XAFS spectra to the experimental results. These measurements provide quantitative ‘‘distortion parameters’’ defined as the difference between the distance of the probe to its nearest neighbor measured in the actual structure and that in a centrosymmetric structure with the same unit cell dimensions. At low temperatures the Pb-edge spectra were fit using four shells and included …

Low Pressure Chemical Vapor Deposition Of Silicon Nitride Films From Ditertiarybutylsilane, Xiangqun Fan

Theses

In this study amorphous stoichiometric silicon nitride films were synthesized by low pressure chemical vapor deposition (LPCVD) using DTBS (ditertiarybutylsilane) and ammonia (NH₃). The growth kinetics were determined as a function of temperature in the range of 600-900 00, pressure in the range of 0.2-1.1 Torr, DTBS flow rate in the range of 10-50 sccm, and NH₃/DTBS flow ratio in the range of 5-20. At constant condition of pressure (0.5 Torr), DTBS flow rate (10sccm) and NH₃ flow rate (100 sccm), the deposition rate of as-deposited silicon nitride films was found to follow an Arrehnius …

High Strength Alumina And Process For Producing Same, James M. Staehler, William W. Predebon, Bruce J. Pletka

Michigan Tech Patents

A vacuum hot pressed alumina material having small, isometric grains; a uniform distribution thereof; relatively low, predominantly transgranular porosity; and a density approaching the theoretical density of pure alumina produced by vacuum hot pressing alumina powder which contains at least 98.0% alumina, is substantially free of any sintering aids or any other additives, and has a median particle size less than about 3 microns, in a vacuum hot press operated at a temperature of at least about 1350° C. and a pressure of at least 28 MPa (3500 PSI) for a sintering period of at least 1.5 hours. The vacuum …

The Current Voltage Characteristics Of Electron Beam Controlled Thin Film Diamond Switches, Christopher Anthony Molina

Electrical & Computer Engineering Theses & Dissertations

The dark current of natural diamond thin films and the induced current due to electron-beam irradiation was measured up to a range of 7000Ncm'. The contact material was aluminum, annealed and unannealed. Switching experiments were performed with electron energies ranging from 70keV to 172keV. The switching results obtained are strongly dependent on the biasing polarity, incident electron energy, and whether the contact is blocking or Ohmic in nature. A simple model which takes traps into consideration allows us to explain the various switching responses. The range of electrons which define, in part, the switch mode was measured for one sample …

Effect Of Additives On Anomalous Deposition In Zinc-Cobalt Alloy Electrogalvanizing, H. M. Wang, Thomas J. O'Keefe

Materials Science and Engineering Faculty Research & Creative Works

Alloys of Zn-Co were deposited from sulphate electrolytes containing various additives to study their influence on the anomalous behavior of the reactions. The effects of antimony, germanium and arsenic on the Zn-Co alloy composition and structure were examined. The results showed that the composition and structure of Zn-Co alloys deposited could be dramatically changed by antimony, and to a lesser extent by germanium and arsenic. A concentration of Sb(III) as low as 5 mg dm-3 increased the cobalt content by a factor of approximately 3; however, the deposit morphology was very dendritic. Germanium additions nearly doubled the cobalt content and …

Finite Element Analysis Of Workability In Bulk Forming Processes, Nagi Hosni Abbasi

Archived Theses and Dissertations

No abstract provided.

Effect Of Poly Acrylate Addition On Coating Color Rheology, Water Retention And Coating Performance, Shambhu Nath

Masters Theses

Five polyacrylate samples were used to study their effects on coating color rheology, water holding and runnability. The Cylindrical Laboratory Coater was used to apply the coatings and study the runnability of the coating colors. The healing tendencies of the coatings were studied by inducing a scratch under the blade. The higher acid level and degree of crosslinking of the polyacrylate gave higher viscosity and the higher acid level also gave higher water retention. Coating colors containing polyacrylates were less prone to dilatancy at high shear. The addition of polyacrylate reduced the healing of coating colors, but for the same …

36th Rocky Mountain Conference On Analytical Chemistry

Rocky Mountain Conference on Magnetic Resonance

Program, abstracts, and information about the 36th annual meeting of the Rocky Mountain Conference on Analytical Chemistry, co-sponsored by the Colorado Section of the American Chemical Society and the Rocky Mountain Section of the Society for Applied Spectroscopy. Held in Denver, Colorado, July 31 - August 5, 1994.

Transient Simulations And Modelling Of Semi-Insulating Gaas Photoconductive Switches, Prasun Kumar Raha

Electrical & Computer Engineering Theses & Dissertations

The primary objective of this thesis is to develop a one-dimensional transient simulator for Photoconductive Semiconductor Switches (PCSS) taking into consideration the material characteristics, the internal physical effects, and the external circuit. Simulations have been performed to study the device behavior at different voltage levels for copper-doped silicon-compensated GaAs material, though other materials could easily be simulated by changing the parameters. The model includes hole transport, and the results demonstrate the effect of hole injection, with and without recombination centers. In addition to developing a one-dimensional transient simulator, the role of various physical effects, such as the field-dependence of trapping …

Effect Of Magnetic-Field On The Microstructure And Macrosegregation In Directionally Solidified Pb-Sn Alloys, Surendra N. Tewari, Rajesh Shah, Hui Song

Chemical & Biomedical Engineering Faculty Publications

An investigation into the influence of a transverse magnetic field (0.45 T) on the mushy zone morphology and macrosegregation in directionally solidified hypoeutectic Pb-Sn alloy shows that the field has no influence on the morphology of dendritic arrays. The field does, however, cause severe distortion in the cellular array morphology. Cellular arrayed growth with the magnetic field results in an extensive channel formation in the mushy zone, as opposed to the well-aligned and uniformly distributed cells formed in the absence of the field. The channels are produced due to the anisotropy in the thermosolutal convection caused by the magnetic field. …

Simple Apparatus For Producing Single Liquid Drops, Dhiren Panda, D. G. C. Robertson

Materials Science and Engineering Faculty Research & Creative Works

A simple experimental apparatus has been used to produce individual mercury and sodium amalgam drops in the size range of 0.3-2.5 mm diam. A high resistance to the flow of liquid was provided by a capillary tube. The cross section consisted of a 0.20 mm o.d. tungsten wire placed in a 0.25 mm capillary bore. By this method, flow rates of 1 μl/s and lower were obtained, which enabled the formation of drops as small as 1 mm diam in a time interval of 20 s. The drops were formed at a plastic tip, and on reaching the desired size, …

Stress Fields In Composites With A Variable Interphase Under Thermo-Mechanical Loadings, Nianfeng Chen

Mechanical & Aerospace Engineering Theses & Dissertations

An interphase in a composite material has a important role for the composite performance. It influences directly or indirectly the strength, fatigue performance and effective properties of the composite. Recently, interphase has drawn increasing attention in composite mechanics. To the best of our knowledge, however, no one seems to have considered the effect of the variable material prope1ty in the interphase on the stress field in the composite material. In this research, the stress fields are determined in the continuous fiber composite and the particulate composite by using the four concentric circular cylinders model and the four phase spheres model, …

An Experimental And Analytical Investigation Of The Iosipescu Shear Test For Composite Materials, Barry Stuart Spigel

Mechanical & Aerospace Engineering Theses & Dissertations

Mechanical properties of composite materials under shear loading are difficult to determine. The Iosipescu Shear test, originally proposed for metals, has in recent years been applied to composites. It has the advantages of small specimen size, simple loading and a reasonably uniform shear stress in the test section.

The purpose of this work is to study the validity of the Iosipescu test method for measuring the shear modulus and shear strength of composites. Finite element analyses indicate that optimum specimen geometry and load locations depend upon the degree of orthotropy of the composite. Test results for a quasi-isotropic graphite/epoxy laminate …

The Development Of A Method To Extract High Purity Oxygen From The Martian Atmosphere, Dongchuan Wu

Mechanical & Aerospace Engineering Theses & Dissertations

A glow-discharge in an ambient Mars atmosphere (total pressure of 5 torr, composed of 95% carbon dioxide) results in the dissociation of carbon dioxide molecules into carbon monoxide and oxygen. If the glow-discharge zone is maintained adjacent and close to a silver membrane, operated at temperatures above 400°C, atomic and molecular oxygen, produced by the glow-discharge, can be separated from the other species by atomic diffusion through the membrane to an ultrahigh vacuum region where the desorbed O₂ is then collected. Experiments have been conducted to study the behavior of the glow discharge in both molecular oxygen and carbon …

The Response Of Dispersion-Strengthened Copper Alloys To High Fluence Neutron Irradiation At 415⁰C, Danny J. Edwards, Joseph William Newkirk, Frank A. Garner, Margaret L. Hamilton, A. Nadkarni, P. Samal

Materials Science and Engineering Faculty Research & Creative Works

Various oxide-dispersion-strengthened copper alloys have been irradiated to 150 dpa at 415°C in the Fast Flux Test Facility (FFTF). The Al₂O₃-strengthened GlidCop™ alloys, followed closely by a HfO₂-strengthened alloy, displayed the best swelling resistance, electrical conductivity, and tensile properties. The conductivity of the HfO₂-strengthened alloy reached a plateau at the higher levels of irradiation, instead of exhibiting the steady decrease in conductivity observed in the other alloys. A high initial oxygen content resulted in significantly higher swelling for a series of castable oxide-dispersion-strengthened alloys, while a Cr₂O₃ -strengthened alloys …

The Excitation Mechanism Of Praseodymium-Doped Semiconductors, Paul L. Thee

Theses and Dissertations

This study on praseodymium Pr luminescence in Al_xGa_1-xAs was conducted to enhance the understanding of the excitation mechanism. Pr was implanted at 390 keV with doses from 5 x 10¹² to 5 x 10¹³ sq cm into Al_xGa_1-xAs x0.0 to 0.50 wafers which were annealed using the rapid thermal annealing RTA method. Low temperature photoluminescence PL was conducted using an Ar-ion laser and Ge detector. PL emissions of Pr from all hosts include peaks near 1.3 and 1.6 µm which are assigned to the intra-4f transitions of 1G4 yielding 3H5 …

Processing, Structural And Electrical Properties Of Sic, Mark Farhad-Garousi

Theses

Cubic silicon carbide films grown by chemical vapor deposition (CVD) on silicon substrates typically have n-type conductivity at 300 °K dominated by a heavily compensated donor with a binding energy in the < 20 meV range. Binding energies <20 meV are not expected in SiC for isolated donors because the shallowest expected binding energy for an electron bound to an isolated donor is approximately 47 meV. The work done on this topic by a few group of scientists has been studied.

The Reduction Of Dielectric Constant By Shaped Porosity, Weiping Cai

Opportunities for Undergraduate Research Experience Program (OURE)

In multi-layer circuits, the reduction of the dielectric constant in substrate materials is becoming increasingly important, as the heat emission of the circuits increases with an increasing number of layers. One way to achieve a lower dielectric constant is to create porosity in the material. In this project, two types of substrate samples were made with coin-shaped porosity. One had holes of 8.0mm in diameter, and the other had holes of 2.5mm in diameter. The total vacuum area was 250mm², or 7.7% of the total area, in either case. It was hoped to discover a relationship between aspect …

Solubility Of Red Phosphorous In Lead, Sean E. Walker

Opportunities for Undergraduate Research Experience Program (OURE)

The determination of the solubility of red phosphorus in lead can be used to produce a plot of the solubility with respect to temperature and pressure. The plot is produced with experimental data, activity determination from present thermodynamic data, and compilation of the two sets of data into the semi-regular solution format. A lead-phosphorus solubility diagram is necessary to determine the amount phosphorus that will be absorbed by lead and will remain unreacted in a given process.

A Three Dimensional Finite Element Thermo-Mechanical Analysis Of Intermittent Cutting, Mariam El Gallab

Archived Theses and Dissertations

No abstract provided.

Experimental Investigation On The Dynamics Of Orthogonal Metal Cutting, Yasser Mohamed Ali

Archived Theses and Dissertations

No abstract provided.

Study Of The Compressive Strength Of Multidirectional Layered Glass Polyester Laminates, Hend Ahmed Amer

Archived Theses and Dissertations

No abstract provided.

Long-Term Effects Of Neutron Absorber And Fuel Matrix Corrosion On Criticality, William Culbreth, P. Zielinski

Mechanical Engineering Faculty Research

Proposed waste package designs will require the addition of neutron absorbing material to prevent the possibility of a sustained chain reaction occurring in the fuel in the event of water intrusion. Due to the low corrosion rates of the fuel matrix and the Zircaloy cladding, there is a possibility that the neutron absorbing material will corrode and leak from the waste container long before the subsequent release of fuel matrix material. An analysis of the release of fuel matrix and neutron absorber material based on a probabilistic model was conducted and the results were used to prepare input to KENO-V, …

Microspheres For Radiation Therapy, D. E. Day, Gary J. Ehrhardt

Materials Science and Engineering Faculty Research & Creative Works

Microspheres for radiation therapy of a mammal which have a non-radioactive isotope which emits beta or gamma radiation of therapeutic intensity upon being irradiated. The microspheres also contain elements which do not become radioactive upon irradiation. The chemical durability of the microspheres is such that they do not release a significant amount of radiation emitting radioisotope into the mammal’s system upon administration. Microspheres containing phosphorus or yttrium; and carbon, nitrogen, fluorine, sodium, magnesium, aluminum, silicon, potassium, vanadium, manganese, gallium, niobium, iodine and/or lead.

Diamond Thin Film Sensors For Hypersonic Flow Studies, Bhaskar Kumar Bulusu

Electrical & Computer Engineering Theses & Dissertations

Conventional metal film sensors can measure flow instabilities of the order of 60 kHz. The turbulence fluctuations in the hypersonic regime are of the order of 200- 400 kHz. To measure these fluctuations, sensors with an enhanced frequency response are required. Therefore, it is required to identify the parameters to enhance the frequency response. These include parameters such as the temperature sensitivity, the resistivity, the thermal conductivity, the diffusivity, specific heat capacity and the geometric size and shape of the film and the substrate. A selection of materials was then carried out to maximize the frequency response. Diamond was identified …

Rapid And Accurate Timing Simulation Of Radiation-Hardened Digital Microelectronics Using Vhdl, Charles P. Brothers Jr.

Theses and Dissertations

This dissertation presents the development of a fast, accurate, timing simulation capability based on VHSIC Hardware Description Language VHDL without the use of back annotation of timing delay information. This VHDL-based timing simulator is intended for use with radiation-hardened microelectronics in simulating timing of circuit operation in pre-radiation, post-radiation 1 MradSi total dose, and ionizing dose radiation environments. Development of the timing models are presented. The implementation of the timing models are incorporated into a VHDL library composed of basic logic gates and flip-flops. Simulations of complex circuits were run in SPICE and VHDL to assess the timing accuracy and …