| Microstructural Design & Optimization of Highly Filled Epoxy Based Composites |
Nov-2009 |
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| Authors:
Bradley White; Jennifer L Jordan; D W Richards; Jonathan E Spowart; Naresh N Thadhani; AIR FORCE RESEARCH LAB EGLIN AFB FL MUNITIONS DIRECTORATE
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 | The dynamic mechanical properties of multi-constituent particulate composites, consisting of individual Ni and Al particles dispersed in an epoxy matrix are investigated in this study. Properties of such composites depend on the mechanical and physical properties of the individual components; their loading density; the shape and size of the particles; the interfacial adhesion; residual stresses; and matrix porosity. These multi-phase particulate composites systems, particularly those with high fill densities, have ... |
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| Penetration Physics at the Meso-Scale |
06-Oct-2009 |
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| Authors:
Conrad W Felice; Y M Gupta; WASHINGTON STATE UNIV PULLMAN INST FOR SHOCK PHYSICS AND PHYSICS DEPT
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| This effort focused on understanding the underlying physics through a multi-scale computational approach to quantify penetrator performance into particulate geologic materials at impact velocities up to 1,500 m/sec. The computational approach employed an explicit, updated Lagrangian finite element formulation that performed 2-D plain strain and axisymmetric analyses of multi-body systems subjected to shock wave loading. To capture the particulate response, a simple elastic-plastic constitutive model was used to represent the ... |
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| Stress Field Evolution in a Ball Bearing Raceway Fatigue Spall (PREPRINT) |
Oct-2009 |
40 pages |
| Authors:
Nagaraj K Arakere; Nathan Branch; Vaughn Svendsen; Nelson H Forster; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH PROPULSION DIRECTORATE
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 | The governing mechanisms of fatigue spall propagation in ball bearing inner raceways are investigated through the use of elastic-plastic finite element modeling, X-Ray Diffraction, and the visual inspection of fatigue spall cracks. The model simulates multiple ball impacts with a fatigue spall's edge in a 208 size ball bearing operating at 10,000 rpm. Ball impacts are shown to cause severe plastic deformation within the spall edge and induce tensile residual ... |
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| Rolling Contact Fatigue Life and Spall Propagation Characteristics of AISI M50, M50 NiL, and AISI 52100. Part 2. Stress Modeling (Preprint) |
Oct-2009 |
31 pages |
| Authors:
Nagaraj K Arakere; Nathan Branch; Vaughn Svendsen; Nelson H Forster; George Levesque; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH PROPULSION DIRECTORATE
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| This is the second part of three-part series that investigates the rolling contact fatigue initiation and spall propagation characteristics of three bearing materials, namely AISI 52100, VIM-VAR M50, and VIM-VAR M50NiL steels. A systematic investigation of effects of rolling contact fatigue (RCF) on evolution of material properties and micro-structural changes resulting in spall propagation rate has not been conducted. As a first step toward understanding spall propagation, we present stress ... |
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| Rolling Contact Fatigue Life and Spall Propagation Characteristics of AISI M50, M50 NiL, and AISI 52100. Part 3. Metallurgical Examination (Preprint) |
Oct-2009 |
30 pages |
| Authors:
Nelson H Forster; Lewis Rosado; William P Ogden; Hitesh K Trivedi; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH PROPULSION DIRECTORATE
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| This is the third part of a three-part series which investigates the rolling contact fatigue initiation and spall propagation characteristics of three bearing materials, namely AISI 52100, VIM-VAR M50, and VIM-VAR M50 NiL steels. While there is substantial prior work published on the rolling contact fatigue initiation of these materials, little is known about their spall propagation characteristics after spall initiation. In Part III, 208 size, 40 mm bore bearings ... |
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| An Investigation of Network Enterprise Risk Management Techniques to Support Military Net-Centric Operations |
Sep-2009 |
186 pages |
| Authors:
John F Teply; NAVAL POSTGRADUATE SCHOOL MONTEREY CA DEPT OF SYSTEMS ENGINEERING
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| System security and information assurance requirements and specifications incorporated into the architectural design of a network enterprise must be driven by an adaptable and evolving network enterprise risk management plan. Network Risk Management must start at concept design and relate to the network's Concept of Operations. The purpose of this thesis is to examine some of the essential elements necessary in a network enterprise risk management plan for a complex ... |
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| Modeling Effects of Crystalline Microstructure, Energy Storage Mechanisms, and Residual Volume Changes on Penetration Resistance of Precipitate-Hardened Aluminum Alloys |
Aug-2009 |
14 pages |
| Authors:
John D Clayton; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
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| An anisotropic nonlinear crystal mechanics model is developed for a class of ductile aluminum alloys, with the intent of relating microscopic features and properties to performance of the alloys deformed at high strain rates that may arise during impact and blast events. A direct numerical simulation of dynamic tensile deformation of an aluminum polycrystal demonstrates a tendency for shear localization to occur in regions of the microstructure where the ratio ... |
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| Aluminum Alloy 7068 Mechanical Characterization |
Aug-2009 |
18 pages |
| Authors:
Michael Minnicino; David Gray; Paul Moy; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE
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| A relatively new alloy of aluminum is being marketed as ordnance aluminum by its developer, Kasier Aluminum (Foothill Ranch, CA), owing its history to the development of ordnance applications. The aluminum alloy designation, 7068, is the strongest aluminum commercially produced. This alloy is aluminum zinc, with an advertised minimum yield strength of 99 ksi. This report characterizes extruded 7068 aluminum in terms of its elastic properties and mechanical strength, in ... |
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| Quantum Enhanced Imaging by Entangled States |
Jul-2009 |
123 pages |
| Authors:
Doyle Nichols; NORTHROP GRUMMAN SYSTEMS CORP LINTHICUM HEIGHTS MD
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| The use of entangled states in a prospective standoff imaging sensor has been explored. Specifically, the question of whether enhanced performance (in terms of achievable resolution, in particular) may be obtained through the use of entangled states in a ghost imaging configuration has been investigated. The resiliency of such a system in the presence of transmission impairments that necessarily accompany sensors in a tactical environment, such as large optical loss, ... |
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| A Three-Dimensional Foil Bearing Performance Map Applied to Oil-Free Turbomachinery |
Apr-2009 |
22 pages |
| Authors:
Christopher Dellacorte; Kevin C Radil; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH GLENN RESEARCH CENTER
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| To effectively apply compliant foil gas bearings to increasingly larger and more challenging turbomachinery, a comprehensive method that compares a foil bearing's capabilities with the application's operating requirements is needed. Extensive laboratory and field experience suggests foil bearing failure is generally due to thermal stress brought on by excessive viscous power loss; therefore a map that graphically relates component and system-level parameters (bearing size, applied loads, and shaft rotational speeds) ... |
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| In Vivo Determination of the Complex Elastic Moduli of Cetacean Head Tissue |
Mar-2009 |
38 pages |
| Authors:
Peter H Rogers; James S Martin; Michael D Gray; GEORGIA INST OF TECH ATLANTA SCHOOL OF MECHANICAL ENGINEERING
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| A confocal ultrasonic elastography system was designed, developed, and tested with discrete scatterers and tissue phantoms. The former experiments demonstrated the ability to use ultrasound for remote generation and detection of vibrations in the audio frequency range. The latter experiments demonstrated the ability to remotely detect shear wave motion amplitude and phase as a function of depth along the ultrasonic beam and determine the wave propagation speed. Results from these ... |
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| Recursive Dispersion Relations in One-Dimensional Periodic Elastic Media |
Feb-2009 |
30 pages |
| Authors:
Ani P Velo; George A Gazonas; Erwin Bruder; Nancy Rodriquez; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE
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| A frequency bandgap is a range of wave frequencies that are prohibited from passing through a medium. The dispersion relation, which links the frequency to the wave number, enables us to illustrate the bandgaps. In [E. H. Lee, A survey of variational methods for elastic wave propagation analysis in composites with periodic structures, in Dynamics of Composite Materials, E. H. Lee, ed., ASME, New York, 1972, pp. 122-138] and [E. ... |
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| Energy Regulation Effects on Critical Infrastructure Protection |
Dec-2008 |
95 pages |
| Authors:
Matthew E McQuinn; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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| U.S. critical infrastructure includes those assets that are vital to maintaining the nation's security, economy, and public health and safety. A reliable supply of electric power provides an essential foundation for the daily operation of all national critical infrastructure as well as most aspects of modern society. A sustained loss of electricity would be significantly detrimental to the economy and the health and security of the nation. Since 1935, the ... |
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| Gestural Communication With Accelerometer-Based Input Devices and Tactile Displays |
Dec-2008 |
8 pages |
| Authors:
Paul D Varcholik; James L Merlo; UNIVERSITY OF CENTRAL FLORIDA ORLANDO INST FOR SIMULATION AND TRAINING
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| In this work, we introduce a communication system for common military hand and arm gestures which does not require a visual connection between the transmitter and receivers. Specifically, we present a computer mediated gesture recognition system that employs a wireless, accelerometer-based input device for collecting and classifying one- and two-hand and arm gestures. This system delivers message output through an audible channel and through a tactile display. The tactile display ... |
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| Dynamic Failure Processes Under Confining Stress in AlON, a Transparent Polycrystalline Ceramic |
Dec-2008 |
9 pages |
| Authors:
James W McCauley; B Paliwal; K T Ramesh; Mingwei Chen; SANDIA NATIONAL LABS ALBUQUERQUE NM
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| An experimental technique is developed to impose a planar lateral confinement in a prismatic specimen (with rectangular cross-section); the setup enabled a controlled and homogeneous stress state with high lateral compressive stresses. A transparent polycrystalline aluminum oxynitride (AlON) specimen was used for the study. The statically pre-compressed specimen was then subjected to axial dynamic compressive loading using a modified compression Kolsky bar setup. Experimental design was performed using 3D computational ... |
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| Microstructure and Properties of WC Spheres |
Nov-2008 |
32 pages |
| Authors:
Jeffrey J Swab; Justin Pritchett; Andrew A Wereszczak; Osama M Jadaan; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
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| Tungsten carbide (WC) spheres are used as projectiles to study the ballistic performance of armor materials and systems. In order to properly understand and model the interaction between the projectile and the armor, it is necessary to have properties of both. In this study, the physical and mechanical properties of two commercially available WC spheres (nominally 0.25 inch in diameter) used in some ballistic impact studies were determined. One WC ... |
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| Extension of Viscoplasticity Based on Overstress to Capture the Effects of Prior Aging on the Time Dependent Deformation Behavior of a High-Temperature Polymer: Experiments and Modeling |
Oct-2008 |
217 pages |
| Authors:
Amber J McClung; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING AND MANAGEMENT
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| The inelastic deformation behavior of PMR-15 neat resin, a high-temperature thermoset polymer, was investigated at 288 degrees C. The experimental program was designed to explore the influence of strain rate on tensile loading, unloading, and strain recovery behaviors. In addition, the effect of the prior strain rate on the relaxation response of the material, as well as on the creep behavior following strain controlled loading were examined. The experimental data ... |
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| Investigations of a Coherently Driven Semiconductor Optical Cavity QED System |
30-Sep-2008 |
19 pages |
| Authors:
Kartik Srinivasan; Christopher P Michael; Raviv Perahia; Oskar Painter; NATIONAL INST OF STANDARDS AND TECHNOLOGY GAITHERSBURG MD
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| Chip-based cavity quantum electrodynamics QED devices consisting of a self-assembled InAs quantum dot QD coupled to a high quality factor GaAs microdisk cavity are coherently probed through their optical channel using a fiber taper waveguide. We highlight one particularly important aspect of this all-fiber measurement setup, which is the accuracy to which the optical coupling level and optical losses are known relative to typical free-space excitation techniques. This allows for ... |
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| Experimental and Theoretical Investigation of the High-Pressure Behavior of Concrete |
01-Sep-2008 |
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| Authors:
Oana Cazacu; Martin J Schmidt; Mark L Green; AIR FORCE RESEARCH LAB EGLIN AFB FL MUNITIONS DIRECTORATE
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| The results of an experimental study aimed at characterizing the behavior of concrete for high confining pressures (up to 500MPa) are reported. The main characteristics of the response under deviatoric conditions are quasi-linearity in the elastic regime, stress-path dependency, and gradual change from compressibility to dilatancy under increasing deviatoric stress. By performing the cyclic triaxial compression tests with several load-creep-unload and reload cycles, the time influence on the overall behavior ... |
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| Continuum Modeling of Elastic Dielectric Solids with Defects, with Application to Barium Strontium Titanate Thin Films |
01-Sep-2008 |
8 pages |
| Authors:
ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE
|
| A model is developed for the electromechanical behaviour of dielectric crystals with defects: dislocations, vacancies, and misoriented boundaries. A geometric framework describes the deformation of the lattice in the presence of such defects. Thermodynamic and kinetic relations are formulated, the latter enabling description of diffusion of charged vacancies and mass rearrangement at free surfaces. Analytical and numerical solutions of specific problems offer insight into performance of barium strontium titanate (BST) ... |
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| Response of an Acoustic Coating on a Rib-Stiffened Plate |
06-Jun-2008 |
45 pages |
| Authors:
Andrew J Hull; John R Welch; NAVAL UNDERSEA WARFARE CENTER DIV NEWPORT RI
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| This report develops an analytical model of a fluid-loaded acoustic coating affixed to a rib-stiffened plate. The model is three-dimensional and has fully-elastic behavior. The system is loaded by a plane wave that is harmonic both spatially and temporally. The model begins with Naviers' equations of motion of an elastic solid, which produces unknown displacement fields that are inserted in to stress equations at the boundaries of the plate and ... |
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| Metapopulation Dynamics of the Softshell Clam, Mya arenaria |
01-Jun-2008 |
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| Authors:
Carly A Strasser; MASSACHUSETTS INST OF TECH CAMBRIDGE
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| I explored metapopulation dynamics and population connectivity, with a focus on the softshell clam, Mya arenaria. I first worked towards developing a method for using elemental signatures retained in the larval shell as a tag of natal habitat. Using a laboratory experiment, I showed that current instrumentation is not able to measure the first larval shell. In concert with developing this method, I reared larval M. arenaria in the laboratory ... |
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| Response of a Beam on a Highly Elastic Foundation |
24 FEB 2008 |
26 pages |
| Authors:
Andrew J. Hull; NAVAL UNDERSEA WARFARE CENTER DIV NEWPORT RI
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| This report develops and analyzes the equations of motion of an infinite Euler-Bernoulli beam that is in contact with a set of periodic support beams. The support beams are modeled as Euler-Bernoulli beams in their transverse directions and modeled using the wave equation in their axial directions. This new formulation allows the support beam models to admit wave propagation so that the dynamic effects of a long foundation can be ... |
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| Accelerated Metals Development by Computation |
FEB 2008 |
212 pages |
| Authors:
Hamish L. Fraser; Michael J. Mills; Rudolph G. Buchheit; Yunzhi Wang; Somnath Ghosh; James C. Williams; Gerald S. Frankel; Anthony D. Rollett; Alten F. Grandt; OHIO STATE UNIV COLUMBUS DEPT OF MATERIALS SCIENCE AND ENGINEERING
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| This program was centered upon the formation of the Collaborative Center for Materials Design (CCMD), an entity coupled with Ohio State University's (OSU) Center for the Accelerated Maturation of Materials (CAMM). There are two foci upon which CCMD, established by the Cooperative Agreement F33615-01-2-5225, is based, the first promoting and developing a strong interaction between scientists and technologists at AFRL and faculty, post-doctoral fellows and research students comprising the team ... |
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| Quantifying the Effects of the Influence of a Tungsten Long-rod Projectile into Confined Ceramics at High-velocity Impact |
29 JAN 2008 |
9 pages |
| Authors:
Tara J. Gorsich; Douglas W. Templeton; ARMY RESEARCH DEVELOPMENT AND ENGINEERING COMMAND WARREN MI
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| High performance modeling of brittle materials is an efficient, inexpensive, time-saving solution for optimal design of armor systems. Quantifying the effects of high-velocity projectiles into brittle materials provides an armor resolution for the critical need of ballistic protection against lethal threats. The analysis modeled a cylindrical, tungsten carbide blunt projectile into four confined, ceramic materials at a high velocity impact. The finite element simulations were performed using Elastic Plastic Impact ... |
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| Bio-Gyros: Tunable Compliant Gryscopic Sensors |
10 JAN 2008 |
7 pages |
| Authors:
Thomas Daniel; WASHINGTON UNIV SEATTLE
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| We examined the motion encoding characteristics of gyroscopic sensors implicated in the flight control systems of insects. These included antennae of moths and the halteres of large craneflies, two structures that encode the Coriolis forces associated with body rotations during aerial maneuvers in insects. Importantly, no prior research program has explored how the structural dynamics of such gyroscopes interact with motions to provide tunable encoding characteristics. Through both neurobiological and ... |
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| Corrosion Protection of Al Alloys for Aircraft by Coatings With Advanced Properties and Enhanced Performance |
20 DEC 2007 |
10 pages |
| Authors:
GORDON BIERWAGEN; Stuart Croll; Dean Webster; Dennis Tallman; Qun Huo; Brian Allahar; Quan Su; Verena Bonitz; Dilhan Fernando; Duhua Wang; NORTH DAKOTA STATE UNIV FARGO DEPT OF CHEMISTRY
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| The report presents research that addresses research performed at NDSU for environmentally compliant corrosion protection in coatings systems of greatly extended lifetimes for present and future aircraft. For present coatings system, this work included modeling degradation in the bulk of a coating by the Monte Carlo methods developed in this laboratory for coating surface degradation, to test its applicability to the prediction of the lifetime of corrosion protection in coatings. ... |
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| Joint Biological Standoff Detection System increment II: Field Demonstration - SINBAHD Performances |
DEC 2007 |
|
| Authors:
Sylvie Buteau; Jean-Robert Simard; Pierre Lahaie; GILLES ROY; Pierre Mathieu; John McFee; Jim Ho; DEFENCE RESEARCH AND DEVELOPMENT CANADA VALCARTIER (QUEBEC)
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| By the end of the 90s, Defence Research and Development Canada (DRDC) initiated the investigation of a novel LIDAR concept which open the possibility of collecting all at once the detailed spectral information contained in the return signals. This 3-year project called SINBAHD (Stand-off INtegrated Bioaerosol Active Hyperspectral Detection) aimed at evaluating the capability of using UV LIF with intensified range-gated spectrometry to detect and characterize bioaerosol from stand-off position. ... |
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| Computer Simulation of Mechanical and Physical Properties of Carbon Foam Materials |
Dec-2007 |
5 pages |
| Authors:
Serguei Kanaoun; INSTITUTO TECNOLOGICO Y DE ESTUDIOS SUPERIORES DE MONTERREY (MEXICO)
|
| The project is devoted to the problem of the numerical simulation of the effective elastic, thermo and electro conductive properties of open-cell foam materials. The Laguerre tessellation procedure is applied for the construction of skeletons of random foam microstructures with prescribed distributions of the cell diameters. A four-parametric approximation of the ligament shapes in the open-cell foams is proposed. For simulation of the elastic properties of open -cell foams, a ... |
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| Stigma: "What Is It and Why Does the Operational Commander Need To Be Concerned?" |
06 NOV 2007 |
26 pages |
| Authors:
Lori A. Laraway; NAVAL WAR COLL NEWPORT RI JOINT MILITARY OPERATIONS DEPT
|
| Mental health disorders are the most significant source of medical and occupational morbidity among active duty military members1 and multiple deployments increase the risk of developing a disorder. Stigma and fear of negative career impact are major reasons attributed to military members not seeking timely mental health services. To date, over one million Active and Reserve military troops have been deployed in Operation Enduring Freedom (OEF) and Operation Iraqi Freedom ... |
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| New Materials Based on Spider Silk |
06 NOV 2007 |
14 pages |
| Authors:
C. Vendrely; T. Scheibel; TECHNISCHE UNIV MUENCHEN (GERMANY)
|
| In this project, we investigated the dragline silk proteins ADF-3 and ADF-4 of the spider Araneus diadematus. Adf-3 and Adf-4 cDNA can each be expressed directly in insect cells using the Baculovirus-expression-System. Recombinant ADF-4 is insolubly produced in the cytoplasm of insect cells and soluble produced upon secretion into the media. Further, parameters influencing stability and solubility of recombinantly produced ADF analogues have been investigated. We detected that intermolecular disulfide ... |
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| Estimating the Strength of Single-Ended Dislocation Sources in Micron-Sized Single Crystals (Postprint) |
OCT 2007 |
20 pages |
| Authors:
S. I. Rao; D. M. Dimiduk; M. Tang; T. A. Parthasarathy; M. D. Uchic; C. Woodward; UES INC DAYTON OH
|
| Three-dimensional (3D) discrete dislocation dynamics simulations were used to calculate the effects of anisotropy of dislocation line tension (increasing Poisson's volumes with free surfaces) and to compare them with the strength of double-ended sources of equal length. Their plastic response was directly modeled within a 1um3 volume composed of a single crystal fcc metal. In general, double-ended sources are stronger than single-ended sources of an equal length and exhibit no ... |
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| Topics in the Analysis of Shear-Wave Propagation in Oblique-Plate Impact Tests |
SEP 2007 |
26 pages |
| Authors:
Mike Scheidler; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE
|
| This report addresses several topics in the theoretical analysis of shock waves, acceleration waves, and centered simple waves, with emphasis on the propagation of shear waves generated in oblique-plate impact tests. The first report, "Formulas for the Pressure and Bulk Modulus in Uniaxial Strain," demonstrates that for a general, nonlinear, isotropic elastic solid, the shear stress in the uniaxially strained region ahead of the shear wave may be inferred from ... |
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| Analytical and Experimental Studies of the Quantification and Propagation of Uncertainties in Nonlinear System Modeling and Simulation |
22 MAR 2007 |
11 pages |
| Authors:
Sami F. Masri; CALIFORNIA UNIV LOS ANGELES DEPT OF CIVIL ENGINEERING
|
| The research objectives of this project were focused on developing methods and procedures suitable for use with dynamic response measurements from flexible structural components and assemblages that may incorporate elements undergoing significant multi-dimensional nonlinear deformations. By using a powerful model-free approach to obtain computationally efficient reduced-order models, a general framework was developed for the probabilistic representation and propagation of measured uncertainties in the stochastic nonlinear test articles, their related nonparametric ... |
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| A Study of Pre-Stress Effect on Dynamic Failure of Transparent Brittle Materials |
MAR 2007 |
19 pages |
| Authors:
G. I. Kanel; S. V. Razorenov; A. S. Savinykh; G. S. Bezruchko; G. V. Garkushin; G. E. Ivanchikhina; RUSSIAN ACADEMY OF SCIENCES MOSCOW INST FOR HIGH ENERGY DENSITIES
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| The report presents results of studying the pre-stress effect on dynamic failure of K8 crown glass, K14 crown glass, fused quartz and sapphire crystals. A technology of radial pre-compression of glass samples has been worked out. Controlled confinement pressure on the specimen in a range of 150 MPa to 550 MPa was provided by installing a shrink-fit metal sleeve on the lateral surface of the glass specimen disk. Results of ... |
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| Ultrasound Activated Contrast Imaging for Prostate Cancer Detection |
MAR 2007 |
28 pages |
| Authors:
Flemming Forsberg; THOMAS JEFFERSON UNIV PHILADELPHIA PA
|
| The current project proposes to develop a novel ultrasound contrast imaging technique (called EEI) for better visualization of the microvessels, which are characteristic of the neovasculature associated with prostate cancer. In vitro, Sonazoid produced 10dB of enhancement at 22 deg C, which reduced to 5dB at 37 deg C. Conversely, Optison created 1dB of enhancement at 22 deg C, which increased to 9dB at 37 degC. This enhancement reduced to ... |
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| Dynamic Response of an Insonified Sonar Window Interacting with a Tonpilz Transducer Array |
03 JAN 2007 |
38 pages |
| Authors:
Andrew J. Hull; NAVAL UNDERSEA WARFARE CENTER DIV NEWPORT RI
|
| This report derives and evaluates an analytical model of a sonar window in contact with an array of Tonpilz transducers. The window is fully elastic so that all wave components are present in the analysis. The system is insonified with a plane acoustic wave so that the sonar system is operating in an acoustic receive mode. The output of the model is a transfer function of a transducer element output ... |
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| Nematic Liquids in Weak Capillary Poiseuille Flow: Structure Scaling Laws and Effective Conductivity Implications |
01-Jan-2007 |
19 pages |
| Authors:
Hong Zhou; M G Forest; NAVAL POSTGRADUATE SCHOOL MONTEREY CA DEPT OF MATHEMATICS
|
| We study the scaling properties of heterogeneities in nematic (liquid crystal) polymers that are generated by pressure-driven, capillary Poiseuille flow. These studies complement our earlier drag-driven structure simulations and analyses. We use the mesoscopic Doi-Marrucci-Greco model, which incorporates excluded-volume interactions of the rod-like particle ensemble, distortional elasticity of the dispersion, and hydrodynamic feedback through orientation dependent viscoelastic stresses. The geometry likewise introduces anchoring conditions on the nano-rods which touch the ... |
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| Leg Muscle Usage Effects on Tibial Elasticity during Running |
JAN 2007 |
8 pages |
| Authors:
Peter P. Antich; TEXAS UNIV AT DALLAS SOUTHWESTERN MEDICAL CENTER
|
| Tibial stress fractures (TSFs) are a substantial problem in military training, but a means of predicting their occurrence remains elusive. Bone strength is key to the resistance of TSF, but bone density, a determinant of strength, is known not to predict TSF. Elasticity is nearly as important as density in determining bone strength but has not been tested in TSF, or even studied in runners. However, clinical studies of osteoporotic ... |
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| Mechanical Properties for an Arbitrary Arrangement of Rigid Spherical Particles Embedded in an Elastic Matrix (Preprint) |
13 DEC 2006 |
69 pages |
| Authors:
Robert L. Hatch; I. L. Davis; ATK LAUNCH SYSTEMS BRIGHAM CITY UT
|
| A computer code has been written which calculates the small deformation stress and strain fields of a medium consisting of a pack of rigid spherical particles embedded in an elastic Hookean matrix. The stress and strain tensors can be calculated at any point in the medium to within a user-specified accuracy. Average mechanical properties of the medium are also output by the code. The code has been used to simulate ... |
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| Software Communications Architecture (SCA) Compliant Software Defined Radio Design for IEEE 802.16 Wirelessman-OFDMTM Transceiver |
DEC 2006 |
98 pages |
| Authors:
Low W. Kian; NAVAL POSTGRADUATE SCHOOL MONTEREY CA DEPT OF ELECTRICAL AND COMPUTER ENGINEERING
|
| Demands for seamless mobile communications are driving the research and development of software defined radio (SDR), which enables a single terminal to transmit and receive in distinct wireless systems through a simple change in software to reconfigure the terminal's functions. Its application areas include military use, home networks, intelligent transport systems and cellular communications. Several SDR software architectures have been developed during the last few years. One implementation of the ... |
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| Processing and Characterization of NiTi Shape Memory Alloy Particle Reinforced Sn-In Solders |
DEC 2006 |
73 pages |
| Authors:
Kohn C. Chung; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| In the typical packaging of a printed circuit board, the tiny-yet-critical solder joints provide both electrical connection and mechanical support for the silicon chips and their substrate. These solders are subjected to serve thermo-mechanical strains during usage and the most common failure arise from thermo-mechanical fatigue (thermal cycling). This is due to the mismatch in the coefficient of thermal expansion between the chip and the packaging substrate. In previous work, ... |
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| Strength and Contact Damage Responses in a Soda-Lime-Silicate and a Borosilicate Glass |
NOV 2006 |
9 pages |
| Authors:
A. A. Wereszczak; K. E. Johanns; T. P. Kirkland; Jr. Anderson C. E.; T. Behner; P. Patel; D. W. Templeton; OAK RIDGE NATIONAL LAB TN
|
| Although soda-lime-silicate glass is typically used as windows in ground vehicles, borosilicate glass is an interesting alternative because its density is about 10% less and therefore its use could reduce vehicle weight. The US Army RDECOM is characterizing both glasses in a variety of ways to compare their performances and judge if the use of borosilicate glass is a worthy substitute. This study supported that through a series of quasi-static ... |
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| MICROMECHANICS AND MICROSTRUCTURE EVOLUTION: Modeling, Simulation and Experiments. Held in Madrid, Spain on 12-16 September 2005 |
30 OCT 2006 |
|
| Authors:
UNIVERSIDAD POLITECNICA DE MADRID (SPAIN)
|
| The aim of this conference is to bring together scientists who are working on the modeling and simulation of the deformation behavior of materials, and on material microstructural evolution. The focus will be on the interplay between behaviors at different length scales, in particular the atomistic, nano/mesoscales, and continuum aspects necessary to describe the processes that lead to changes in microstructure. Of particular interest are investigations that discuss the bridging ... |
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| High-Order Accurate Particle-In-Cell (PIC) Methods on Unstructured Grids with Applications to Microwave Generation and Accelerator Modeling |
01 SEP 2006 |
8 pages |
| Authors:
Jan S. Hesthaven; BROWN UNIV PROVIDENCE RI DIV OF APPLIED MATHEMATICS
|
| A thoroughly validated, robust, and efficiently solver for the electromagnetics problem continues to be extended to provide a basic field solver for the EM-PIC problem. This has resulted in a first generation of a DG-FEM based PIC method on unstructured grids. The particle mover relies on high-order interpolation, efficient local search algorithms to locate the particles, and a level set approach to implement elastic/inelastic interactions with boundaries. Charge and current, ... |
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| Advanced Stimulated Scattering Measurements in Supercritical Fluids |
SEP 2006 |
47 pages |
| Authors:
Gregory W. Faris; SRI INTERNATIONAL MENLO PARK CA MOLECULAR PHYSICS LAB
|
| Work was performed on development of stimulated Brillouin and Rayleigh scattering for measurements in supercritical fluids. Improvements were made to our instrumentation to fully resolve the stimulated Rayleigh scattering peak in the supercritical regime, a capability that is important for measurement of the thermal properties of supercritical fuels. To provide narrower linewidths, the injection-seeded laser has been modified to operate as a pulse-amplified system. A new electronic modulation technique has ... |
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| Natural Frequencies and Mode Shapes of a Nonlinear, Uniform Cantilevered Beam |
SEP 2006 |
207 pages |
| Authors:
Daniel J. Marquez-Chisolm; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH DEPT OF AERONAUTICS AND ASTRONAUTICS
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| A series of experiments in 1975, referred to as the Princeton Beam Experiments, were performed to measure natural frequencies and create a nonlinear elastic deformation model to improve helicopter main beam designs. These experiments used a homogeneous 7075 aluminum beam and have been referenced as a baseline for the past thirty years to validate computer models and theories in an effort to build beams capable of withstanding aero-elastic, static, and ... |
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| Ceramic External Pressure Housings For Deep Sea Vehicles |
Sep-2006 |
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| Authors:
J D Stachiw; Donald Peters; Glenn McDonald; WOODS HOLE OCEANOGRAPHIC INSTITUTION MA
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| Only glasses, ceramic and carbon fiber reinforced plastic can provide the necessary weight to strength ratio to make the external pressure housings for undersea vehicles positively buoyant at the abyssal design depth. This group of materials poses unique challenges to the designer and fabricator of pressure housings. This paper summarizes the findings of the R & D program aimed at developing the technology for the design, fabrication, and testing of ... |
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| Dynamic Response of an Alternative Tissue Simulant, Physically Associating Gels (PAG) |
SEP 2006 |
14 pages |
| Authors:
Paul Moy; Tusit Weerasooriya; Thomas F. Juliano; Mark R. VanLandingham; Wayne Chen; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
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| Recent work on formulating alternatives to ballistic gelatin, a soft tissue simulant, has lead to the development of physically associating gels (PAG). Ballistic gelatin impact response has been traditionally used to test and evaluate firearms and bullets but it does have some drawbacks, such as lacking consistency in its viscoelastic properties due to variability during the fabrication process, short shelf-life, and deterioration under prolonged usage at room temperature. PAG offers ... |
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| An Internal Variable Theory of Deformation, Damage, and Fragmentation of Solids |
SEP 2006 |
10 pages |
| Authors:
John D. Clayton; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
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| A unified framework of continuum elasticity, inelasticity, damage mechanics, and fragmentation in solid materials is presented. A free energy functional accounts for thermodynamics of elastic deformation and damage, with kinetic relations for inelastic rates adapted from prior literature. Average fragment velocities follow from momentum conservation, average fragment sizes are deduced from an energy balance, and size and velocity distributions are constructed following entropy maximization. The model is further developed to ... |
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Reports by Keyword(s)
ELASTIC PROPERTIES
