Open Access. Powered by Scholars. Published by Universities.®

Mechanical Engineering Commons

Open Access. Powered by Scholars. Published by Universities.®

2002

Materials Science and Engineering

Institution
Keyword
Publication
Publication Type

Articles 1 - 14 of 14

Full-Text Articles in Mechanical Engineering

Modeling, Fabrication, And Optimization Of Niobium Cavities: Phase Ii Quarterly Report, Robert A. Schill Jr., Mohamed Trabia Sep 2002

Modeling, Fabrication, And Optimization Of Niobium Cavities: Phase Ii Quarterly Report, Robert A. Schill Jr., Mohamed Trabia

Transmutation Sciences Materials (TRP)

Multipacting is one of the major loss mechanisms in rf superconductivity cavities for accelerators. This loss mechanism limits the maximum amount of energy/power supported by the cavities. Optimal designs have been identified in others’ studies. In practice, these designs are not easily manufactured. Chemical etching processes used to polish the cavity walls result in a nonuniform surface etch. A nonuniform surface etch will leave some unclean areas with contaminants and micron size particles. These significantly affect mutipacting. Further, a nonuniform etch will leave areas with damaged grain structure, which is not good for superconducting properties. Typically, the depth of ...


Use Of Positron Annihilation Spectroscopy For Stress-Strain Measurements: Quarterly Progress Report (June 1 – August 31, 2002), Ajit K. Roy Aug 2002

Use Of Positron Annihilation Spectroscopy For Stress-Strain Measurements: Quarterly Progress Report (June 1 – August 31, 2002), Ajit K. Roy

Transmutation Sciences Materials (TRP)

The purpose of this collaborative research project involving the University of Nevada Las Vegas (UNLV), the Idaho State University (ISU), and the Los Alamos National Laboratory (LANL) is to evaluate the feasibility of determining residual stresses in cold-worked, plastically-deformed, and welded materials using a nondestructive method based on positron annihilation spectroscopy. This technique uses γ-rays from a small MeV electron Linac to generate positrons inside the sample via pair production. This method is known to have capabilities of characterizing defects in thick specimens, that could not be accomplished by conventional positron technique or other nondestructive methods. The generated data will ...


Correlation Between The Xps Peak Shapes Of Y1bu2cu3o7-X And Film Quality, Paul N. Barnes, Sharmila M. Mukhopadhyay, Timothy J. Haugan, Swaminathan Krishnaswami, Justin C. Tolliver, Iman Maartense Aug 2002

Correlation Between The Xps Peak Shapes Of Y1bu2cu3o7-X And Film Quality, Paul N. Barnes, Sharmila M. Mukhopadhyay, Timothy J. Haugan, Swaminathan Krishnaswami, Justin C. Tolliver, Iman Maartense

Mechanical and Materials Engineering Faculty Publications

X-ray photoelectron spectroscopy (XPS) depth profiling was used to investigate the compositional and chemical profile of a typical YBCO coated conductor architecture. Results of the process revealed that the Y(3d) photoelectronic peak shape in these films is very different from bulk YBCO. To investigate this, several samples of Y i Ba2Cu307_„ thin films were intentionally created of varying quality. The films were deposited on LaA10 3 by pulsed laser deposition with ./c. values ranging from poorly conducting up to several MA/cm2. Initial results indicated a potential correlation between the Y(3d) XPS peak shape (full-width-half-maximum) of the YBCO ...


Modeling And Simulation Of The Chemical Etching Process In Niobium Cavities, Qin Xue Aug 2002

Modeling And Simulation Of The Chemical Etching Process In Niobium Cavities, Qin Xue

UNLV Theses, Dissertations, Professional Papers, and Capstones

Niobium Cavities are important parts of the integrated NC/SC high-power linear accelerator (linac) that can accelerate over 100 mA of protons to several GeV. Surface finish of the niobium cavity plays an important role of achieving the best performance of niobium cavity. The chemical etching techniques have been widely used.

Chemical etching of the inner surface of the cavity is achieved by circulating acid through it. The acid interacts with the surface and eliminates imperfections. During the etching process, a pipe with baffles is inserted within the cavity to direct the flow along the surfaces.

A 2-D, axisymmetric, steady ...


Design And Analysis For Melt Casting Metallic Fuel Pins Incorporating Volatile Actinides, Xiaolong Wu Aug 2002

Design And Analysis For Melt Casting Metallic Fuel Pins Incorporating Volatile Actinides, Xiaolong Wu

UNLV Theses, Dissertations, Professional Papers, and Capstones

Fundamental issues related to the selection of a metallic fuel casting furnace design are presented and discussed including heating mechanisms, casting issues, crucible design, and issues related to the mass transport of americium. The process of evaluating all of these different criteria is undertaken to select a concept that would have the greatest chance of success for casting americium in a metallic fuel rod. Based on this evaluation process, a concept for the casting of metallic fuel pins containing high vapor pressure materials is selected and discussed. The important physics of this concept include mass transport of americium from the ...


Abstracts, Review Of Progress In Quantitative Nondestructive Evaluation (Bellingham, Wa, July 14–19, 2002), Review Of Progress In Quantitative Nondestructive Evaluation Jul 2002

Abstracts, Review Of Progress In Quantitative Nondestructive Evaluation (Bellingham, Wa, July 14–19, 2002), Review Of Progress In Quantitative Nondestructive Evaluation

Review of Progress in Quantitative Nondestructive Evaluation

Abstracts of papers presented at the 2002 Review of Progress in Quantitative Nondestructive Evaluation (QNDE) conference held in Bellingham, Washington from July 14–19, 2002.


Design And Analysis Of A Process For Melt Casting Metallic Fuel Pins Incorporating Volatile Actinides, Yitung Chen, Darrell Pepper, Randy Clarksean Apr 2002

Design And Analysis Of A Process For Melt Casting Metallic Fuel Pins Incorporating Volatile Actinides, Yitung Chen, Darrell Pepper, Randy Clarksean

Fuels Campaign (TRP)

UNLV has developed and will continue to develop process models for the analysis of melt casting processes. This work will continue to be performed under the guidance of Argonne National Laboratory (ANL) engineers to ensure that their knowledge and experience benefits the project. The research to be conducted during the second year will center on performing detailed analyses on a conceptual design of an inductively heated skull-crucible casting furnace. Processing conditions will be analyzed, basic models utilized, and detailed heat and mass transfer models will be developed to analyze the most promising processes. The goal of this second year is ...


Modeling, Fabrication, And Optimization Of Niobium Cavities: Phase Ii, Robert A. Schill Jr., Mohamed Trabia Apr 2002

Modeling, Fabrication, And Optimization Of Niobium Cavities: Phase Ii, Robert A. Schill Jr., Mohamed Trabia

Transmutation Sciences Materials (TRP)

Niobium cavities are important parts of the integrated NC/SC high-power linacs. Over the years, researchers in several countries have tested various cavity shapes. They concluded that elliptically shaped cells are the most appropriate shape for superconducting cavities. The need for very clean surfaces led to the use of a buffered chemical polishing procedure for surface cleaning to get good performance of the cavities. This proposal discusses the second phase of research in the second year of the project.

The first phase (starting Summer 2001) has resulted in improving the basic understanding of multipacting and the process of chemical etching ...


Use Of Positron Annihilation Spectroscopy For Stress-Strain Measurements, Ajit K. Roy Apr 2002

Use Of Positron Annihilation Spectroscopy For Stress-Strain Measurements, Ajit K. Roy

Transmutation Sciences Materials (TRP)

The purpose of this collaborative research project involving the University of Nevada, Las Vegas (UNLV) and Idaho State University (ISU) is to evaluate the feasibility of determining residual stresses of welded (after pre-straining) engineering materials using a new nondestructive technique based on positron annihilation spectroscopy. The proposed technique is to use γ-rays 2 from a small MeV electron Linac to generate positrons inside the sample via pair production. This method can be used for materials characterization and investigation of defects in thick samples that could not be accomplished by conventional positron techniques or other nondestructive methods. The data generated will ...


Modeling, Fabrication, And Optimization Of Niobium Cavities – Phase I: Quarterly Progress Report November 20, 2001 - February 20, 2002, Robert A. Schill Jr., Mohamed Trabia Feb 2002

Modeling, Fabrication, And Optimization Of Niobium Cavities – Phase I: Quarterly Progress Report November 20, 2001 - February 20, 2002, Robert A. Schill Jr., Mohamed Trabia

Transmutation Sciences Materials (TRP)

Multipacting is one of the major loss mechanisms in RF superconductivity cavities for accelerators. This loss mechanism limits the maximum amount of energy/power supported by the cavities. Optimal designs have been identified in others’ studies. In practice, these designs are not easily manufactured. Chemical etching processes used to polish the cavity walls result in a nonuniform surface etch. A nonuniform surface etch will leave some unclean areas with contaminants and micron size particles. These significantly affect multipacting. Further, a nonuniform etch will leave areas with damaged grain structure, which is not good for superconducting properties. Typically, the depth of ...


Heat Transfer In A Thin Liquid Film In The Presence Of Electric Field For Non-Isothermal Interfacial Condition, Rama S.R. Gorla, Jorge E. Gatica, Bahman Ghorashi, Pijarn In-Eure, Larry W. Byrd Jan 2002

Heat Transfer In A Thin Liquid Film In The Presence Of Electric Field For Non-Isothermal Interfacial Condition, Rama S.R. Gorla, Jorge E. Gatica, Bahman Ghorashi, Pijarn In-Eure, Larry W. Byrd

Chemical & Biomedical Engineering Faculty Publications

Heat transfer enhancement in an evaporating thin liquid film using the electric field under non-isothermal interfacial condition is presented. A new mathematical model subjected to van der Waals attractive forces, the capillary pressure and the electric field is developed to describe the heat transfer enhancement in the evaporating thin liquid film. The effect of an electrostatic field on the curvature of the thin film, evaporative flux, pressure gradient distribution, heat flux, and heat transfer coefficient in the thin film is presented. The results show that the electric field can enhance heat transfer in the thin liquid film significantly. In addition ...


Piezoelectric In Situ Transmission Electron Microscopy Technique For Direct Observations Of Fatigue Damage Accumulation In Constrained Metallic Thin Films, Xiaoli Tan, T. Du, J.K. Shang Jan 2002

Piezoelectric In Situ Transmission Electron Microscopy Technique For Direct Observations Of Fatigue Damage Accumulation In Constrained Metallic Thin Films, Xiaoli Tan, T. Du, J.K. Shang

Xiaoli Tan

A piezoelectricin situtransmission electron microscopy(TEM) technique has been developed to observe the damage mechanism in constrained metallic thin films under cyclic loading. The technique was based on the piezoelectric actuation of a multilayered structure in which a metallic thin film was sandwiched between a piezoelectric actuator and a silicon substrate. An alternating electric field with a static offset was applied on the piezoelectric actuator to drive the crack growth in the thin metallic layer while the sample was imaged in TEM. The technique was demonstrated on solder thin films where cavitation was found to be the dominant fatigue damage ...


Modeling, Fabrication, And Optimization Of Niobium Cavities: Phase Ii Second Quarterly Report, Robert A. Schill Jr., Mohamed Trabia Jan 2002

Modeling, Fabrication, And Optimization Of Niobium Cavities: Phase Ii Second Quarterly Report, Robert A. Schill Jr., Mohamed Trabia

Transmutation Sciences Materials (TRP)

Niobium cavities are important parts of the integrated NC/SC high-power linacs. Over the years, researchers in several countries have tested various cavity shapes. They concluded that elliptically shaped cells are the most appropriate shape for superconducting cavities. The need for very clean surfaces lead to the use of a buffered chemical polishing produce for surface cleaning to get good performance of the cavities. Up to this point, the second phase has resulted in the design of an experimental setup for the fluid flow experiment. Other experimental activities include the evaluation of a vacuum system are underway. Little reportable progress ...


Effect Of Polymer-Surface Mobility On Adhesion In Poly(Methyl Methacrylate)-Tape System, Bhavesh C. Gandhi, Frank D. Blum, Lokeswarappa R. Dharani Jan 2002

Effect Of Polymer-Surface Mobility On Adhesion In Poly(Methyl Methacrylate)-Tape System, Bhavesh C. Gandhi, Frank D. Blum, Lokeswarappa R. Dharani

Chemistry Faculty Research & Creative Works

The interaction between two polymer layers, especially adhesion between them, plays an important role in polymer processing and other applications. Detailed knowledge of the molecular structure and dynamics of polymer interfaces, and how they relate to macroscopic mechanical properties, should help designers construct more functional systems. Unfortunately, there have been few studies where both molecular and macroscopic studies have been performed on similar systems. In previous studies from our group, we have probed the dynamics of poly(methyl acrylate) (PMA) and thermal behavior of poly(methyl methacrylate) (PMMA) on silica. These studies helped us paint a picture for strongly bound ...