| Cyanate Ester Graphene Composites |
29 Mar 2012 |
20 pages |
| Authors:
Josiah T Reams; Andrew Guenthner; Kevin R Lamison; Joseph M Mabry; AIR FORCE RESEARCH LAB EDWARDS AFB CA PROPULSION DIR/SPACE AND MISSILE PROPULSION DIV/PROPUL MATERIALS APPLICATIONS BR
|
 | Graphene oxide produced by chemical oxidation formed stable dispersions in LECy cyanate ester matrix and edge functionalized graphite does not. High shear mixing followed by sonication was the best method for graphene oxide dispersion in LECy. Addition of 1 wt% edge-functionalized graphite of LECy did not increase storage modulus but addition of 1 and 2 wt% GO increased storage modulus below the Tg. Diffusion of water in LECy 1 wt% ... |
|
| Analytical Yield Criterion for an Anisotropic Material Containing Spherical Voids and Exhibiting Tension-Compression Asymmetry |
Nov 2011 |
20 pages |
| Authors:
Joel B Stewart; Oana Cazacu; AIR FORCE RESEARCH LAB EGLIN AFB FL MUNITIONS DIRECTORATE
|
| This paper is devoted to the development of a macroscopic anisotropic yield criterion for a porous material when the matrix material is incompressible, anisotropic and displays tension - compression asymmetry. The analytical yield criterion is obtained based on micromechanical considerations and non-linear homogenization. The matrix plastic behavior is described by the Cazacu et al. (2006) anisotropic yield criterion that is pressure-insensitive and accounts for strength-differential effects. Comparison between finite element ... |
|
| General, Unified, Multiscale Modeling to Predict the Sensitivity of Energetic Materials |
05 Oct 2011 |
269 pages |
| Authors:
Donald L Thompson; Thomas D Sewell; Donald Brenner; Steven J Stuart; Tahir Cagin; MISSOURI UNIV-COLUMBIA DEPT OF CHEMISTRY
|
| This report describes the accomplishments for the MURI grant General, Unified, Multiscale Modeling to Predict the Sensitivity of Energetic Materials (Grant No. 48101-EG-MUR). This was a comprehensive theoretical/computational research program to develop, validate, benchmark, and apply methods and models to provide predictive capabilities for energetic materials. The thrust of the work was the development of atomic-level models and ab initio quantum chemistry methods that are generally applicable to the chemical ... |
|
| Investigation of Elastocil M4370 Silicone Rubber Release Agent for Use on M1130 Projectile |
Oct 2011 |
15 pages |
| Authors:
John F Osterndorf; Richard Wu; Daniel Murphy; ARMY ARMAMENT RESEARCH DEVELOPMENT AND ENGINEERING CENTER PICATINNY ARSENAL NJ ENERGETICS WARHEADS AND MANUFACTURING TECHNOLOGY DIRECTORATE
|
| An investigation of two release agents Miller Stevenson's MS-143DF Polytetrafluoroethylene (PTFE) Release Agent- Dry Lubricant and Vaseline 100% Pure Petroleum Jelly] to create a separation in the room temperature vulcanizing (RTV) above the interface of the explosive and RTV to prevent the cracking of the explosive below the interface with the RTV. Test specimens were fabricated and subjected to various environmental conditions to determine if the RTV will remain separate ... |
|
| A Three-Dimensional Eulerian Code for Simulation of High-Speed Multimaterial Interactions |
Aug 2011 |
105 pages |
| Authors:
H S Udaykumar; IOWA UNIV CEDAR FALLS
|
| High speed material interactions may lead to large deformations followed by fragmentation. To simulate such problems in the Eulerian framework on a fixed Cartesian mesh, all interfaces (free surfaces as well as interacting material interfaces) are tracked as levelsets; to resolve shocks and interfaces, a quad-tree adaptive mesh is employed. Collisions between embedded objects are resolved using an efficient collision detection algorithm and appropriate ineterfacial conditions are supplied. This paper ... |
|
| Development of Geomaterial Parameters for Numerical Simulations Using the Holmquist-Johnson-Cook Constitutive Model for Concrete |
JUN 2011 |
24 pages |
| Authors:
Christopher S. Meyer; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE
|
| Numerical simulation of brick and mortar masonry in the literature has been performed using homogenized material properties; however, heterogeneous material properties for brick and mortar for a constitutive model built into hydrocodes have been unavailable. The Holmquist-Johnson-Cook (HJC) constitutive model for concrete captures pressure and strain-rate-dependent strength behavior and void crushing damage behavior of porous materials reasonably well, is readily available in many hydrocodes, and is commonly used to simulate ... |
|
| Microstructural Modeling and Representation of Simultaneous Failure Modes in Crystalline Aggregates Subjected to Dynamic Loading Conditions |
09 JAN 2011 |
33 pages |
| Authors:
M. A. Zikry; NORTH CAROLINA STATE UNIV AT RALEIGH DEPT OF MECHANICAL AND AEROSPACE ENGINEERING
|
| This provides an integrated framework to simultaneously handle different interrelated physical mechanisms, such as a myriad of representative dislocation-density interactions with high and low angle GB interfaces, the growth and coalescence of a population of voids, and how these interactions can lead to either intergranular or transgranular failure. The formation of pile-ups at GB interfaces, as a function of dislocation-density partial and total blockage and absorption at GB interfaces, will ... |
|
| Dislocation Dynamic Modeling in High Temperature Single Crystal Viscoplasticity (Preprint) |
Mar-2009 |
5 pages |
| Authors:
Brice N Cassenti; Alexander Staroselsky; PRATT AND WHITNEY EAST HARTFORD CT
|
| We have developed a crystallographic-based viscoplastic model for nonisothermal high temperature deformation and coupled it with damage kinetics. Several damage mechanisms, namely the multiplication of mobile dislocations, void growth and including scale effects, caused by dislocation extrusions/intrusions, have been considered. We applied two body interaction concepts from chemical kinetics to include in our constitutive relations the generation and interaction of pinned and mobile dislocations. The relative importance of each of ... |
|
| Benchtop Insensitivity: First Steps with Shocked PETN |
JAN 2008 |
22 pages |
| Authors:
William K. Lewis; Mario E. Fajardo; AIR FORCE RESEARCH LAB EGLIN AFB FL MUNITIONS DIRECTORATE
|
| "Insensitive Munitions (IM) are conventional weapons and ordnance that fulfill their performance objectives while minimizing collateral damage if exposed to stimuli including fires, impact and shock threats." "The statutory requirement for IM is set forth in U.S. Code, Title 10, Subtitle A, Part IV, chapter 141, Section 2389..." ... Department of Defense Acquisition Manager's Handbook for Insensitive Munitions, Jan 2004, Rev 1. |
|
| Nanoparticle Control of Void Formation and Expansion in Polymeric and Composite Systems |
FEB 2007 |
9 pages |
| Authors:
James C. Seferis; DELAWARE UNIV NEWARK CENTER FOR COMPOSITE MATERIALS
|
| This research focused on a nanoscale modification of traditional polymeric matrix morphology through particle introduction and subsequent void formation. The main areas of research have been a study of interlayer modification and analyses of continued carbon fiber reinforced polymeric matrix composites at the nanoscale. The results showed improvements in toughness up to a critical threshold, after which, an increase in the concentration and size of nanoparticulate matter and corresponding foams ... |
|
| Nano-Particle Control of Void Formation and Expansion in Polymeric and Composite Systems |
JUL 2006 |
11 pages |
| Authors:
James C. Seferis; WASHINGTON UNIV SEATTLE DEPT OF CHEMICAL ENGINEERING
|
| The research focused on carbon fiber reinforced epoxy composites with varying dispersions of montmorillonite and nanoprosity, processed with either prepreg or Vacuum Resin Transfer Mold (VARTM) technologies. The most significant advancements and conclusions in this final report include interlayer modification of composites at the nanoscale and characterization of the interlayer behaviour of nanoparticles and nanoporous composites, as well as VARTM processing of nanoclay filled composites. |
|
| Ballistic Imaging in the Primary Breakup Region of Diesel Injector Sprays |
31 JAN 2006 |
16 pages |
| Authors:
M. A. Linne; T. E. Parker; COLORADO SCHOOL OF MINES GOLDEN
|
| The Colorado School of Mines (CSM) has developed a technique (called ballistic imaging) for single-shot imaging of the near-field primary breakup region of a diesel spray. Ballistic imaging is a non-intrusive optical measurement technique that produces line-of-sight integrated images. These images represent the underlying spray structure in spite of the droplet cloud which surrounds the interior of the spray. Single shot ballistic imaging relies on an ultra-fast optical switch; the ... |
|
| Liner Design Guidance for Confined Disposal Facility Leachate Control |
DEC 2004 |
25 pages |
| Authors:
E. J. LeBoeuf; E. L. Thackston; Paul R. Schroeder; M. R. Palermo; ENGINEER RESEARCH AND DEVELOPMENT CENTER VICKSBURG MS
|
| This technical note provides design guidance for liners used to reduce the release of contaminants from confined disposal facilities (CDFs) containing contaminated dredged materials. Design requirements, geotechnical considerations, material selection, required thickness, construction, quality control, and monitoring are included. References to detailed design procedures are also given. This technical note is intended for use by USACE personnel and federal and state regulatory agency personnel, as well as dredging permit applicants ... |
|
| Large Area, Real-Time Inspection of Rocket Motors Using a Novel Handheld Ultrasound Camera |
12 MAR 2004 |
20 pages |
| Authors:
J. W. Gurney; M. E. Lasser; R. S. Lasser; J. P. Kula; D. C. Rich; IMPERIUM INC SILVER SPRING MD
|
| Phase I of this SBIR program sought to demonstrate the applicability of the Imperium ultrasound camera to the inspection of solid rocket motors (SRMs). Phase II of the program aimed at developing a prototype camera that could be used in either handheld or production settings. The prototype camera was tested to determine its level of performance, ability to detect typical flaws, and the potential time savings with its use. Results ... |
|
| Nonlinear Characterizing of the Crack Growth Behavior in a Filled Elastomer |
2004 |
9 pages |
| Authors:
C. T. Liu; M. Yen; AIR FORCE RESEARCH LAB EDWARDS AFB CA SPACE AND MISSILE PROPULSION DIV
|
| In this study, the crack growth behavior in a filled elastomer containing hard particles embedded in a rubbery matrix was investigated. The specimen was tested at a constant strain rate of 0.067 cm/cm/min at room temperature. Two initial crack lengths, 2.54 mm and 12.7 mm, were considered. A hybrid experimental-numerical method was used to calculate the J-integral value. The results show that the initial crack length had a significant effect ... |
|
| Failure Analysis of Three Si3N4 Balls Used in Hybrid Bearings |
15 FEB 2003 |
29 pages |
| Authors:
M. J. O'Brien; N. Presser; E. Y. Robinson; AEROSPACE CORP EL SEGUNDO CA LAB OPERATIONS
|
| The rolling-element fatigue life of advanced hybrid material bearings consisting of silicon-nitride balls, REX20 tool-steel inner races, and CRU20 tool-steel outer races was measured under well-qualified laboratory testing. Multiple sets of four bearings (207H size) were tested using the least-of-four technique and sudden-death statistics to obtain a Weibull distribution based upon a bivariate model that accounted for load, time, and sample size. The Weibull distribution model shows that the advanced ... |
|
| Homogenization Modeling for Mechanical Properties of Composite Conductor With Cooling Channel |
NOV 2002 |
30 pages |
| Authors:
We Sun; Jerome T. Tzeng; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
|
| An electrical composite conductor may consist of a metallic core with a cooling channel and a multilayered insulating material. A model was developed to predict the mechanical properties of the composite conductor based on two- level homogenization hierarchies. A composite cylinder assembly model was developed in the level 1 homogenization for metallic core with a cooling channel, in which the cooling channel was analogized as a fiber void with null ... |
|
| Measurements of the Early Development of Trailing Vorticity from a Rotor |
JUL 2002 |
67 pages |
| Authors:
Kenneth W. McAlister; James T. Heineck; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION MOFFETT FIELD CA AMES RESEARCHCENTER
|
| The wake behind a two-bladed model rotor in light climb was measured using particle image velocimetry, with particular emphasis on the development of the trailing vortex during the first revolution of the rotor. The distribution of vorticity was distinguished from the slightly elliptical swirl pattern. Peculiar dynamics within the "void" region may explain why the peak vorticity appeared to shift away from the center as the vortex aged, suggesting the ... |
|
| An Investigation on High Temperature Behavior of Laminate and Nanostructured Composite Materials |
SEP 2001 |
15 pages |
| Authors:
Horacio D. Espinosa; NORTHWESTERN UNIV EVANSTON IL DEPT OF MECHANICAL ENGINEERING
|
| A novel high-strain-rate and high temperature experimental set-up was developed to investigate failure of advanced materials. Experiments were performed on preheated Ti-6Al-4V specimens, at temperatures in the range 25-550 deg C, to determine the role of thermal activation on dynamic stress induced inelasticity and damage. Interferometric techniques were employed to record the free surface velocity of the target plates. The experimental results show that thermal activation overcomes the role of ... |
|
| Adapters: A Domain-Specific Programming and Development Technology for Run-Time Reconfiguration at the System Level |
JUL 2001 |
31 pages |
| Authors:
John Shackleton; HONEYWELL INC MINNEAPOLIS MN
|
| The ADAPTERS project in general is an attempt to fill the current void in system design and integration technology for systems, which include ACS based processing nodes. The approach taken was to develop and integrate ACS tools within existing system level tools. The resulting technology is a more integrated co-design environment, which focuses on three primary technology areas: programming environments, partitioning, mapping, and trade-off analysis, and dynamic run-time environments. |
|
| Pressure Effects and Surface Cracks in a Rubbery Particulate Composite |
04 JUN 2001 |
20 pages |
| Authors:
T. C. Miller; AIR FORCE RESEARCH LAB EDWARDS AFB CA SPACE AND MISSILE PROPULSION DIV
|
| Cracks developed during manufacturing, handling and storage of rubbery particulate composites. Previous tests used single edge notched tension (SENT) specimens. In this work, surface cracked specimens are compared with the previous results. Results for ambient and pressurized test conditions are also compared. Pressure affects fracture behavior by suppressing void nucleation, growth, and coalescence. Both initiation of growth and subsequent growth rates are affected. Applying ambient test data can result in ... |
|
| Investigating Cumulative Damage in a Highly Filled Polymeric Material |
29 MAY 2001 |
14 pages |
| Authors:
C. T. Liu; AIR FORCE RESEARCH LAB EDWARDS AFB CA PROPULSION DIRECTORATE WEST
|
| Objectives: 1) Investigate the effects of strain rate and cyclic loading on cumulative damage in a highly filled polymeric material. 2) Determine the relationship between the NDE damage parameter and material properties. |
|
| China's Energy Equation: A Strategic Opportunity |
10 APR 2001 |
31 pages |
| Authors:
James R. Burke; ARMY WAR COLL CARLISLE BARRACKS PA
|
| China's astounding economic growth of the past two decades has placed enormous strains on available energy supplies. Continued economic growth, which is the key to China's future, is constrained by a skewed energy equation in which domestic and foreign energy supplies are far removed from China's burgeoning population. The energy barriers are a combination of economic, natural, and political factors that afford the U.S. a unique opportunity to initiate bilateral ... |
|
| Investigating Near-Tip Damage and Crack Growth Behavior in a Solid Propellant |
01 MAR 2001 |
10 pages |
| Authors:
C. T. Liu; AIR FORCE RESEARCH LAB EDWARDS AFB CA
|
| When cracks occur, whether resulting from the manufacturing process or from service loads, the stresses near the crack tip will be redistributed according to nonlinear material behavior. Depending on the magnitude of the local stresses and the local strength, various defects, microvoids or microcracks, can develop in the crack tip region. And, depending on the severity of these defects, crack growth behavior can be significantly affected. Therefore, to obtain a ... |
|
| Fabrication and Characterization of Photoconductive AlGaN Detectors/ Structural Characterization of SiC Wafers |
22 FEB 2001 |
23 pages |
| Authors:
Marek Skowronski; CARNEGIE-MELLON UNIV PITTSBURGH PA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| Structure of silicon carbide wafers have been evaluated by x-ray topography, high resolution x-ray diffraction, etching, Atomic Force Microscopy, and related techniques. The low angle grain boundaries were imaged by White Beam Synchrotron X-Ray Topography and mis-orientations quantitatively mapped out by x-ray diffraction. The dominant component of mis-orientation was basal plane tilt. The formation mechanism is most likely due to buckling of the rigidly mounted SiC seed during initial stages ... |
|
| Crack Growth Data Collection and Reduction Methodology Survey |
30 JAN 2001 |
13 pages |
| Authors:
Tim Miller; AIR FORCE RESEARCH LAB EDWARDS AFB CA SPACE AND MISSILE PROPULSION DIV
|
| This methodology survey discusses crack growth data collection and reduction. Complications in the measurement process include inhomogeneity of microstructure, large deformations, and material nonuniformity complicate the analysis of cracks in propellant. Microstructure - void nucleation, growth, and coalescence at the crack tip causes sporadic crack growth. Large deformations - blunting at crack tip and large dimensional changes make measuring crack size somewhat subjective. Variation of specimen properties due to trouble ... |
|
| Investigating Cumulative Damage in a Highly Filled Polymeric Material |
22 JAN 2001 |
3 pages |
| Authors:
C. T. Liu; AIR FORCE RESEARCH LAB EDWARDS AFB CA
|
| When a highly filled polymeric material consisting of many fine particles is stretched, the sizes and distribution of the filler particles, the crosslinking density of the polymer chains, and the variation of the bond strength between the particles and binder can produce highly nonhomogeneous local stress and strength fields. Because of the particle's high rigidity relative to the binder, the local stress is significantly higher than the applied stress, especially ... |
|
| Constitutive-Microdamage Modeling of Target-Missile Damage Caused by Hypervelocity Impact |
AUG 2000 |
|
| Authors:
Eftis; Ceasar J. Trejo; TEXAS UNIV AT EL PASO FAST CENTER FOR STRUCTURAL INTEGRITY OF AEROSPACE SYSTEMS
|
 | A constitutive microdamage model is developed capable of simulating high shock compression, release, dilatation (tension), and microdamage evolution leading possibly to fracture and penetration of targets after hypervelocity impact. The microdamage constitutive model is applicable to polycrystalline metals and is appropriate in the lower range of hypervelocity impact velocity, i.e. approximately 2-7 Km/s, over which the projectile and target materials remain in the solid state. The model implements the Mie-Omneisen ... |
|
| The Effects of Pressure on Fracture of a Rubbery Particulate Composite |
JUN 2000 |
18 pages |
| Authors:
T. C. Miller; C. T. Liu; AIR FORCE RESEARCH LAB EDWARDS AFB CA SPACE AND MISSILE PROPULSION DIV
|
| There is a need for studying the effects of pressure on fractures. Recommendations for future work: examination of short crack fracture phenomena (why do short cracks behave differently?) Surface crack growth analysis: find a way to measure crack depth and width in pressurized environment. Links between microstructure and pressure effect (establish a connection between pressure effect and microstructural phenomena such as void nucleation, growth, and coalescence). |
|
| Joint Vision 2010 Operational Concepts and Issues in Military OperationsOther Than War (MOOTW) |
10 APR 2000 |
28 pages |
| Authors:
Rick A. Dorsey; ARMY WAR COLL CARLISLE BARRACKS PA
|
| The premise behind Joint Vision 2010 is that its operational concepts apply across the full spectrum of military operations. Yet very little, if anything, is written regarding "operationalizing" its concepts to Military Operations Other Than War (MOOTW). Specifically, much is written on how Joint Vision 2010 Operational Concepts, Dominant Maneuver and Precision Engagement, can be applied in a Major Theater of War (MTW), but doctrinal application ... |
|
| Vulnerability and Lethality Assessment: The Role of Full-Up System-LevelLive-Fire Testing and Evaluation |
APR 2000 |
115 pages |
| Authors:
Martha K. Nelson; FRANKLIN AND MARSHALL COLLEGE LANCASTERPA DEPT OF BUSINESS ADMINISTRATION
|
| In this era of decreased defense budgets and limited resources, it is important for decision-makers to determine the optimal strategy for assessing the vulnerability or lethality (V/L) of a weapon system and the role of Full-Up System-Level Live-Fire Test and Evaluation (FU SL LFT&E) in that strategy. This report presents a foundation for a methodology to: (1) identify, measure, and categorize the costs and benefits of ... |
|
| Development and Implementation of a Shell Element With Pressure Variation Through the thickness and Void Growth and Nucleation Effects |
SEP 1999 |
124 pages |
| Authors:
Patrick M. McDermott; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| A shell formulation was developed from a three-dimensional solid. The shell element has four corner nodes at which there are three displacements and three rotations as nodal degrees of freedom, and includes both transverse sheer and transverse normal deformations. |
|
| Cure Shrinkage Measurement |
27 JUL 1999 |
|
| Authors:
Stanley G. Byrd; Herbert M. Swett; DEPARTMENT OF THE NAVY WASHINGTON DC
|
| The apparatus and method measures the shrinkage of rocket motor propellant that is caused during curing and may control this shrinkage by thermally expanding it to prevent creation of voids and cracks. The apparatus heats the propellant compound during curing. A laser emits radiation onto the compound and a detector receives reflected radiation from the compound and provides signals representative of the size of the volume of the compound. An ... |
|
| Analytical Transmission Electron Microscopy Studies on Copper-Alumina Interfaces |
JUN 1999 |
100 pages |
| Authors:
Richard Y. Hashimoto; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| A diffusion bonded copper-alumina interface had been studied using energy dispersive x-ray spectroscopy (EDX) and electron energy loss spectroscopy (EELS). Investigations of polycrystalline alumina showed that silica, a common commercial impurity, was present at the triple junctions in the form of fine mullite crystals in a glassy, silicon rich phase. Silicon was also detected along the alumina grain boundaries near triple junctions. There was no observed diffusion of Cu into ... |
|
| Electromigration and Local Field Effects in Mesoscopic Interconnects |
14 MAY 1999 |
11 pages |
| Authors:
Gary Bernstein; NOTRE DAME UNIV IN
|
| Samples were fabricated by the same processes as the previous ones, but with triangular e-beam pads. Validity of the test structure was first examined. After stressing groups of 40 nm and 50 nm wide lines, samples were checked in the FESEM. In the tested samples, most of the lines failed inside the lines and their pads were intact, and a small portion failed in the pads, as shown in Figure ... |
|
| An Investigation Into the Noninvasive Assessment of Bone Density Using Multiplexed Compton Scattered Tomography |
08 MAR 1999 |
94 pages |
| Authors:
Marc J. Sands; AIR FORCE INST OF TECH WRIGHT-PATTERSONAFB OH SCHOOL OF ENGINEERING
|
| The purpose of this research is to investigate the application of a Compton scatter imaging technique to measure bone density. A demonstration Multiplexed Compton Scatter Tomograph (MCST) was assembled to demonstrate the feasibility of detecting osteoporosis by modifying a system originally designed to detect hidden corrosion in aluminum aircraft wings. Measurements were performed on an aluminum phantom representing a wrist bone containing varying densities in the center and varying thickness ... |
|
| Experimental Demonstration of Underground Structure Characterization Using Sensitive Magnetic Sensors |
29 JAN 1999 |
36 pages |
| Authors:
Suman Ganguly; CENTER FOR REMOTE SENSING INC FAIRFAX VA
|
| The practical feasibility of detection and characterization of underground structures using electromagnetic sources in the ELF/VLF range is being investigated. For this, we investigate issues associated with sensors. One important objective is to examine the feasibility of using magnetic field measurements alone. We have developed unique 3-D e.m. models which can adequately cover arbitrary geometries, inhomogeneous ground, various excitation schemes and most importantly can handle a wide range of frequencies. ... |
|
| Repair of Damage to Marine Sandwich Structures: Part 1 - Static Testing |
OCT 1998 |
|
| Authors:
Rodney Thomson; Raoul Luescher; Ivan Grabovac; AERONAUTICAL AND MARITIME RESEARCH LAB MELBOURNE (AUSTRALIA)
|
| Marine vessels constructed from sandwich panels with glass reinforced polymer (GRP) composite skins and PVC foam core are now common. Such structures will inevitably be subjected to damage and any repair technique needs to ensure that the strength and stiffness of the structure are restored. The current recommended Royal Australian Navy (RAN) techniques for the repair of sandwich structures have been evaluated and deficiencies identified. Static ... |
|
| Omnidirectional Ultrasonic Microprobe Hydrophone |
03 MAR 1998 |
|
| Authors:
Mark B. Moffett; James M. Powers; Dmitry Chizhik; Timothy B. Straw; DEPARTMENT OF THE NAVY WASHINGTON DC
|
| An omnidirectional ultrasonic microprobe hydrophone is disclosed. Applications include underwater mine detection, explosive shock testing, high wave number measurements, medical imaging, and therapeutic systems. The apparatus includes at least two lead zirconate titanate (PZT) pressure sensing elements having a plurality of columnar voids formed therein. The pressure sensing elements are deposited on a metallic or nonmetallic substrate which provides mechanical support for the microprobe hydrophone. Electrical connection to the pressure ... |
|
| Silicon-Based Oxide/Silicon/Oxide Resonant Tunneling |
MAR 1998 |
67 pages |
| Authors:
Alan Seabaugh; Robert M. Wallace; TEXAS INSTRUMENTS INC MCKINNEY DEFENSESYSTEMS AND ELECTRONICS GROUP
|
| We explored two methods for forming SiO2/Si/SiO2 resonant tunneling diodes with crystalline silicon quantum wells. The first method, growth through voided oxide, was successful in demonstrating for the first time that crystalline Si can be grown through voids in the oxide. However conditions for forming the small void size needed to block electron transport, while allowing nucleation of silicon through the oxide, were not found. A systematic search of the ... |
|
| Material Failure Mechanisms in Nonlinear Solids and Structures |
FEB 1998 |
19 pages |
| Authors:
Cornelius O. Horgan; Wills Johnson; VIRGINIA UNIV CHARLOTTESVILLE SCHOOL OF ENGINEERING AND APPLIED SCIENCE
|
| This work was concerned with research on the fundamental mechanics and mathematics of material failure mechanisms in nonlinear solids and structures. The specific areas investigated were those of void nucleation and growth due to large deformations in nonlinear solids and end effects in anisotropic and laminated structures. Research on cavitation phenomena, which serve as a precursor to fracture, is crucial to the understanding of failure mechanisms in rubber-like solids (e.g. ... |
|
| Rapid Placement Technology for Affordable Composites Manufacturing |
29 JAN 1998 |
19 pages |
| Authors:
J. W. Gillespie; D. S. Kukich; DELAWARE UNIV NEWARK CENTER FOR COMPOSITE MATERIALS
|
| The RAPTECH-ACM program yielded the following research accomplishments: (1) Development of process models governing heat transfer, consolidation, crystallization, intimate contact, healing, and residual stress and warpage. These models have been incorporated into a real-time neural- network-based simulation. (2) Incorporation of advanced model-based control on line and optimization to establish setpoints for heat input, velocity, and pressure to achieve the desired quality (i.e., bonding, void content). (3) Integration of infrared sensors ... |
|
| Quantification of Shape, Angularity, and Surface Texture of Base Course Materials |
JAN 98 |
29 pages |
| Authors:
Vincent Janoo; COLD REGIONS RESEARCH AND ENGINEERING LAB HANOVER NH
|
| A state-of-the-art review was conducted to determine existing test methods for characterizing the shape, angularity, and surface texture of coarse aggregates. The review found direct methods used by geologists to determine these characteristics. These methods involve physical measurements of individual aggregates and are very laborious and time consuming. Engineers have developed index tests (indirect methods) to quantify the combined effect of the shape, angularity, and surface texture of coarse aggregates ... |
|
| Use of Ultrasonic Tape Lamination for In-Process Debulking of Thick Composite Structures |
1998 |
10 pages |
| Authors:
Margaret E. Roylance; David K. Roylance; Kathryn L. Nasmith; NAVAL AIR WARFARE CENTER AIRCRAFT DIV PATUXENT RIVER MD
|
| Foster-Miller has developed an advanced processing technique for organic matrix composites called ultrasonic Tape Lamination (UTL). This technique employs ultrasonic energy to insonify composite tape (either thermoplastic or B-staged thermoset) to induce controlled and virtually instantaneous viscoelastic and frictional heating in the composite. UTL can be used for in-process debulking and controlled staging of thick filament wound or fiber placed composite structures. During UTL ... |
|
| Development of a Shell Element with Pressure Variation Through the Thickness |
30 SEP 1997 |
18 pages |
| Authors:
Young K. Kwon; NAVAL POSTGRADUATE SCHOOL MONTEREY CA DEPT OF MECHANICAL ENGINEERING
|
| A shell formulation was developed from a three-dimensional solid. The shell element is an isoparametric element, and has four corner nodes at which there are three displacements and three rotations, independently. Therefore, the element formulation includes the transverse shear deformation and the transverse normal deformation. In addition, the formulation consists of separate components of the mean stress and deviatoric stresses because the Gurson constitutive model for void growth is based ... |
|
| Influence of Chemical, Physical, Biological and Geochemical Processes of Early Diagenesis and Material Exchange Across the Sediment/Seawater Interface in Margin Sediments |
22 SEP 97 |
14 pages |
| Authors:
Miriam Kastner; SCRIPPS INSTITUTION OF OCEANOGRAPHY LA JOLLA CA
|
| Long-Term Goals and Summary of Accomplishments: The goals of this project were to determine links between sediment chemistry, physical properties, and microfabric during the early diagenesis of surface and near-surface, organic-rich sediments. To this end, we provided high resolution characterizations of sediment microfabric, physical properties, chemistry, mineralogy, and organic matter content as well as theoretical work on smectite interlayer hydration. The data collected were used to permit observation of organic ... |
|
| Theory and Simulation of the Structure and Dynamical Properties of Electronic Materials |
27 MAY 97 |
65 pages |
| Authors:
Sokrates T. Pantelides; VANDERBILT UNIV NASHVILLE TN DEPT OF PHYSICS AND ASTRONOMY
|
| During the course of this grant, research focused on using available theoretical tools to explore and elucidate complex dynamics of impurities in Si. In particular, we studied clustering of As in heavily doped Si, segregation of As in Si grain boundaries and the migration of oxygen in Si. In addition we carried out atomic scale nonequilibruim heat flow simulations and mesoscopic calculations of void growth in polycrystalline metal lines. ... |
|
| An Adaptive Inspection Sampling Program for Determining Coating Failure of Nimitz Class Aircraft Carrier Tanks and Voids |
MAR 97 |
164 pages |
| Authors:
Mark E. Thornell; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| This thesis addresses Nimitz class aircraft carrier tank and void maintenance. It contributes to the solution of current maintenance problems in four ways. First, it stratifies Nimitz class aircraft carrier tanks and voids into ten groups and assigns a criticality factor to each group. These groups and criticality factors can be extended to other classes of ships. Second, it demonstrates methods to estimate the survival function of tank and void ... |
|
| Marginal Aggregates in Flexible Pavements: Laboratory Evaluation |
MAR 97 |
142 pages |
| Authors:
Randy C. Ahlrich; ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS GEOTECHNICAL LAB
|
| The purpose of this project was to evaluate the utilization of substandard or marginal aggregates in flexible airport pavement construction. This investigation was undertaken to evaluate the effects of using lower quality aggregates such as rounded uncrushed gravels and sands on the rutting of flexible pavements. The scope of this research project included a review of available literature and existing data (Part I), a laboratory evaluation organized to determine the ... |
|
| System for Determining Size and Location of Defects in Material by use of Microwave Radiation |
12 FEB 1997 |
15 pages |
| Authors:
John M. Liu; DEPARTMENT OF THE NAVY WASHINGTON DC
|
| Microwave radiation emitted from a single antenna is focused on a targeted material from which back-scattering of reflected radiation is received by the same antenna to provide signal measurement data from which detected material defects are evaluated by determination of void location and size. Antenna position and orientation is adjusted to obtain the signal measurement data from back-scattering of the microwave radiation along at least two target incidence paths from ... |
|
Reports by Keyword(s)
VOIDS
