| A Study of Topic and Topic Change in Conversational Threads |
Sep-2009 |
95 pages |
| Authors:
Jessy Cowan-Sharp; NAVAL POSTGRADUATE SCHOOL MONTEREY CA DEPT OF COMPUTER SCIENCE
|
 | This thesis applies Latent Dirichlet Allocation (LDA) to the problem of topic and topic change in conversational threads using e-mail. We demonstrate that LDA can be used to successfully classify raw e-mail messages with threads to which they belong, and compare the results with those for processed threads, where quoted and reply text have been removed. Raw thread classification performs better, but processed threads show promise. We then present two ... |
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| Numerical Simulation of Wear in a C/C Composite Multidisk Clutch (Preprint) |
Apr-2009 |
26 pages |
| Authors:
Gregory E Hilmas; Shuangmei Zhao; Lokeswarappa R Dharani; MISSOURI UNIV-ROLLA
|
| Friction and wear of engineering components are critical factors influencing the product life. In this study a wear simulation method is presented to investigate the wear behavior of a C/C composite multidisk clutch under simulated operation conditions. A modified Archard's wear model is implemented into a user subroutine which works in association with an axisymmetric finite element model to predict the progress of wear on friction surfaces. An element removal ... |
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| Rotational Response of Toe-Restrained Retaining Walls to Earthquake Ground Motions |
DEC 2006 |
343 pages |
| Authors:
Robert M. Ebeling; Barry C. White; ENGINEER RESEARCH AND DEVELOPMENT CENTER VICKSBURG MS INFORMATION TECHNOLOGY LAB
|
| This research report describes the engineering formulation and corresponding software developed for the rotational response of rock-founded, toe-restrained Corps retaining walls to earthquake ground motions. The PC software CorpsWallRotate (sometimes referred to as CWRotate) was developed to perform an analysis of permanent wall rotation for each proposed retaining wall section to a user-specified earthquake acceleration time-history. A particular formulation of the permanent sliding (i.e., translational) displacement response of retaining walls ... |
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| Structural Design of Wing Twist for Pitch Control of Joined Wing Sensor Craft |
MAR 2006 |
117 pages |
| Authors:
III Kimler Fred A.; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING AND MANAGEMENT
|
| This research investigated two aspects of the aft wing structure of a joined wing SensorCraft. First, the efficacy of a novel approach for incorporating wing twist for pitch control was analyzed. This design involved adding a spanwise sliding joint into the wing structure at the lower aft spar of the vehicle's aft wing. Second, the joint section where the forward and aft wings connect and form the outboard wing was ... |
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| Vertical Plane Obstacle Avoidance and Control of the REMUS Autonomous Underwater Vehicle Using Forward Look Sonar |
JUN 2005 |
97 pages |
| Authors:
Daniel L. Hemminger; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| Current rates of technological advancement continue to translate into changes on our battlefields. Aerial robots capable of gathering reconnaissance along with unmanned underwater vehicles capable of defusing enemy minefields provide evidence that machines are playing key roles once played by humans within our military. This thesis explores one of the major problems facing both commercial and military UUVs to date. Successfully navigating in unfamiliar environments and maneuvering autonomously to avoid ... |
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| Simplex Sliding Mode Control for Nonlinear Uncertain Systems Via Chaos Optimization |
01 DEC 2004 |
10 pages |
| Authors:
Zhao Lu; Leang-SAN Shieh; Guanrong Chen; Norman P. Coleman; HOUSTON UNIV TX DEPT OF ELECTRICAL ANDCOMPUTER ENGINEERING
|
| As an emerging effective approach to nonlinear robust control simplex sliding mode control demonstrates some attractive features not possessed by the conventional sliding mode control method from both theoretical and practical points of view. However no systematic approach is currently available for computing the simplex control vectors in nonlinear sliding mode control. In this paper, chaos-based optimization is exploited so as to develop a systematic approach to seeking the simplex ... |
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| Friction & Wear Under Very High Electromagnetic Stress |
OCT 2004 |
18 pages |
| Authors:
Richard S. Cowan; Steven Danyluk; Francis Moon; J. C. Ford; Donald W. Brenner; GEORGIA INST OF TECH ATLANTA
|
| This document summarizes initial progress toward advancing the fundamental understanding of the friction, wear and mechanics of interfaces subjected to extreme electromagnetic stress, high relative velocities and elevated temperatures. During this reporting period, faculty and staff from Georgia Tech, Cornell, N.C. State and Rensselaer Polytechnic performed tasks in two thrust areas of basic research: Modeling and Experiment. With respect to the former, investigators are looking at mixed lubrication and its ... |
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| An Experimental Approach for Studying the Creep Behavior of Thin Film/ Substrate Interfaces |
SEP 2004 |
59 pages |
| Authors:
Carl L. Parks; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| Large shear stresses often develop at the interface between dissimilar materials in microelectronic devices, when they are subjected to thermo-mechanical excursions. These stresses, which typically occur due to thermal expansion mismatch between the adjoining materials, are usually confined near the edges of films. However, for narrow thin film lines, these stresses may exist over a large fraction of the film-substrate interface. When the substrate is subjected to relatively high homologous ... |
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| Elevated Temperature Fretting Facility |
JUL 2004 |
5 pages |
| Authors:
Richard W. Neu; GEORGIA INST OF TECH ATLANTA SCHOOL OFMECHANICAL ENGINEERING
|
| The primary equipment purchased is a Phoenix Tribology Ltd. DN55 High Temperature Sliding and Fretting Machine. The machine was designed from the ground up specifically for high temperature (up to 8OOoC) fretting experiments. The system has lower mass actuator system which is ideal for fretting and reciprocal sliding experiments to enable cycling at higher frequencies (up to 500 Hz) while minimizing dynamic effects. The system can also perform reciprocating sliding ... |
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| Identification of Deformation Mechanisms During Bi-Axial Straining of Superplastic AA5083 Material |
JUN 2004 |
69 pages |
| Authors:
Rebecca M. Fowler; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| This study evaluated dome test samples of a superplastic AA5083 aluminum alloy deformed at nominally constant strain rates under biaxial strain conditions. Dome test samples resulted from gas-pressure forming of sheet material; for this study, samples were deformed at strain rates corresponding either to grain boundary sliding or dislocation creep control of deformation. Orientation Imaging Microscopy was utilized to determine texture development, grain size and grain-to-grain misorientation angle distributions for ... |
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| Bearing Friction Torque in Bolted Joints |
12 FEB 2004 |
|
| Authors:
Sayed A. Nassar; G. C. Barber; Dajun Zuo; OAKLAND UNIV ROCHESTER MI DEPT OF MECHANICAL ENGINEERING
|
 | In this paper, formulas are developed for the calculation of the effective radius of the bearing friction forces on the rotating contact surface in threaded fasteners. These formulas provide a more accurate estimation of the underhead bearing friction torque component in threaded fastener applications. This enhances the reliability, safety, and the quality of bolted assemblies, especially in critical applications. It is well known that the torque-tension correlation in threaded fasteners, ... |
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| Dynamic Cracking and Energy Absorption in Laminates Containing Through- Thickness Reinforcement |
FEB 2004 |
177 pages |
| Authors:
Brian N. Cox; Sridhar Narayanaswamy; ROCKWELL SCIENTIFIC CO THOUSAND OAKS CA
|
| Inertial effects in the mechanism of fiber pullout were examined, with emphasis on how the rate of propagation of stress waves along the fiber, and thence the pullout dynamics, are governed by friction and the propagation of companion waves excited in the matrix. The frictional sliding between the fiber and the matrix is described by a constant interfacial friction stress, the sign of which depends on the relative particle velocity ... |
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| Study of Cavitation and Failure Mechanisms of a Superplastic 5083 Aluminum Alloy |
SEP 2003 |
87 pages |
| Authors:
Juanito F. Boydon Jr; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| Superplastic forming of AA5083 is an economical way to create components of complex shape while retaining the high strength and stiffness-to- weight ratios associated with aluminum alloys. However, failure of the material due to formation and linkage of cavities during superplastic deformation poses a major obstacle in effective industrial employment of this technology. Deformed samples of AA5083 were analyzed by various techniques after superplastic deformation under uniaxial tension, biaxial tension, ... |
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| Acquisition of a Nanoindenter for Research on Small-Scale Materials and Structures |
AUG 2003 |
6 pages |
| Authors:
Frank W. Zok; D. R. Clarke; N. C. MacDonald; Kimberly L. Turner; CALIFORNIA UNIV SANTA BARBARA DEPT OF MECHANICAL AND ENVIRONMENTAL ENGINEERING
|
| The first project is "Matrix Enabled Damage Tolerance in Oxide Continuous Fiber Reinforced Ceramic Composites", PIs: Frank Zok, Carlos Levi and Robert McMeeking, funded by AFOSR. Here, the nanoindenter is being used for measuring the mechanical properties of fiber-matrix interfaces, through the so- called "fiber push-in" test. In essence, the test involves pushing an individual fiber past the surrounding matrix while simultaneously measuring the sliding displacement at the fiber/matrix interface. ... |
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| Sliding Mode Control of a Shape Memory Alloy Actuated Manipulator |
JUN 2003 |
8 pages |
| Authors:
Mohammad H. Elahinia; T. M. Siegler; Donald J. Leo; Mehdi Ahmadian; VIRGINIA POLYTECHNIC INST AND STATE UNIV BLACKSBURG DEPT OF MECHANICAL ENGINEERING
|
| This paper presents a two-pan controller that uses a state variable estimator for control of a single degree of freedom rotary manipulator acutated by Shape Memory Alloy (SMA) wire. A model for the SMA actuated manipulator is presented. The model includes nonlinear dynamics of the manipulation a constitutive model of the Shape Memory Alloy. and the electrical and heat transfer behavior of SMA wire. The estimator predicts the state vector ... |
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| Interfacial Control of Creep Deformation in Ultrafine Lamellar TiA1 |
2003 |
7 pages |
| Authors:
L. M. Hsiung; LAWRENCE LIVERMORE NATIONAL LAB CA CHEMISTRY AND MATERIALS SCIENCE DEPT
|
| Solute effect on the creep resistance of two-phase lamellar TiAl with an ultrafine microstructure creep- deformed in a low-stress (LS) creep regime WHERE A NEARLY LINEAR CREEP BEHAVIOR WAS OBSERVED has been investigated. The resulted deformation substructure and in-situ TEM experiment reveals that interface sliding by the motion of preexisting interfacial dislocations is the predominant deformation mechanism in LS creep regime. Solute segregation at interfaces and interfacial precipitation caused by ... |
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| Simulation of Carbon Nanotube Pull-out When Bonded to a Polymer Matrix |
2003 |
6 pages |
| Authors:
S. J. Frankland; V. M. Harik; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION HAMPTON VA LANGLEY RESEARCH CENTER
|
| A carbon nanotube pulling through a polyethylene matrix was simulated using molecular dynamics. The interfacial sliding was characterized in terms of a nanoscale friction model, which is parametrized from the molecular dynamics simulation, and involves determining the critical pull-out force on the nanotube and the effective viscosity at the nanotube/polymer interface. Comparison was made of the pull-out behavior of non-bonded and functionalized nanotube composites. Chemical bonds between the polymer and ... |
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| Nash Solution by Extremum Seeking Control Approach |
DEC 2002 |
|
| Authors:
Yaodong Pan; Tankut Acarman; Umit Ozguner; OHIO STATE UNIV COLUMBUS DEPT OF ELECTRICAL ENGINEERING
|
| In this paper, we propose an algorithm to solve the Nash equilibrium solution for an n-person noncooperative dynamic game by the extremum seeking control approach with sliding mode. For each player, a switching function is defined as the difference between the player's cost function and a reference signal. The extremum seeking controller for each player is designed so that the system converges to a sliding boundary layer defined in the ... |
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| Effects of Counterface Roughness and Conformity on the Tribological Performance of Crosslinked and Non-crosslinked Medical-Grade Ultra-High Molecular Weight Polyethylene |
APR 2002 |
|
| Authors:
A. D. Chawan; A. M. Chakravartula; J. Zhou; L. A. Pruitt; M. Reis; CALIFORNIA UNIV BERKELEY DEPT OF MECHANICAL ENGINEERING
|
| The tribological behavior of crosslinked ultra-high molecular weight polyethylene (UHMWPE) was compared to that of non-crosslinked UHMWPE used as control sample. A reciprocating pin-on-disk tribometer was used to determine the effects of countersurface roughness and conformity on wear mechanisms occurring during the initial stage of sliding. Pin samples of two different radii of curvature were slid against medical-grade Co-Cr alloy disks with surface roughness ranging from 0.005 to 0.04 micrometers ... |
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| Stable Neural Control of Uncertain Multivariable Systems |
DEC 2001 |
26 pages |
| Authors:
Mark J. Mears; Marios M. Polycarpou; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH AIR VEHICLES DIRECTORATE
|
| Tracking control of a class of nonlinear, uncertain, multi-input, multiple-output systems is addressed in this paper. The control system architecture uses neural networks for function approximation, certainty equivalent control inputs to cancel plant dynamics and smoothed sliding mode control to insure that the trajectories remain bonded. Lyapunov analysis is used to derive equations for the sliding mode control, neural network training, and to show uniform ultimate boundedness of the closed ... |
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| Sliding Mode Observers Versus Kalman Filter in the Homing Loop |
23 JUL 2001 |
8 pages |
| Authors:
I. A. Schkolnikov; Y. B. Shtessel; P. Zarchan; D. P. Lianos; ALABAMA UNIV IN HUNTSVILLE DEPT OF ELECTRICAL AND COMPUTER ENGINEERING
|
| A comparison via Monte-Carlo simulations is made of Sliding Mode Observers versus Kalman Filter in the homing missile guidance system using different guidance laws. It's shown that the sliding mode observer contributes to less miss distance due to noise than Kalman filter. Application of sliding mode estimators in the homing loop with Proportional Navigation guidance and with a phase-lead compensation based on sliding mode estimators for the flight control system ... |
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| A Hot-Stage Atomic Force Microscope for the Measurement of Plastic Deformation in Metallic Thin Films During Thermal Cycling |
JUN 2001 |
86 pages |
| Authors:
Thomas E. Shultz; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| An Atomic Force Microscope is equipped with a hot-stage and a vacuum system in order to enable in-situ studies of plastic deformation and interfacial sliding of thin metallic films on Si substrates during thermal cycling. The apparatus can reach sample temperatures of lOO deg C while maintaining optimum resolution. The system will allow future in-situ thermal cycling experiments on microelectronic devices in a protected environment to provide insight into the ... |
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| Mechanical and Microstructural Analysis on the High Temperature Deformation of Gamma TiAl Alloy |
04 JAN 2001 |
77 pages |
| Authors:
Jeonung H. Kim; Chong S. Lee; POHANG UNIV OF SCIENCE AND TECHNOLOGY (KOREA) CENTER FOR ADVANCED AEROSPACE MATERIALS
|
| It is aimed in this study to investigate the high temperature deformation mechanisms of two-phase gamma titanium-aluminum alloy in view of the inelastic deformation theory and to quantify the relative contribution of each mechanism to the overall deformation. The influence of y/a2 volume fraction on high temperature deformation behavior and the preferable cavity initiation sites have also been studied. For this purpose, a series of load relaxation tests and tensile ... |
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| Enhancing TCP Performance Over Satellite Channels |
NOV 2000 |
|
| Authors:
Maik Kammermann; Hugues Latour; DEFENCE RESEARCH ESTABLISHMENT OTTAWA (ONTARIO)
|
| In general the Transmission Control Protocol (TCP) works well while establishing end-to-end connections for common Internet services. However, there are two problem areas associated with performance over satellite channels: propagation delay and channel noise effects. Noise is a common problem in wireless technologies and consequently the bit-error-rate (BER) is significantly higher than in wired networks. TCP is particularly vulnerable to BER because it is a reliable protocol. TCP will retransmit ... |
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| Frictional Characteristics of Cracks and Failure of Brittle Materials under Dynamic Compression |
17 JUL 2000 |
10 pages |
| Authors:
Guruswami Ravichandran; CALIFORNIA INST OF TECH PASADENA
|
| A newly developed specimen has been used to investigate the compressive failure due to the presence of flaws in brittle materials. Experiments were conducted under both static and dynamic loading conditions to delineate the role of friction on sliding induced crack initiation. Specimens with different coefficients of friction and crack inclination were prepared and a systematic understanding of crack initiation under compressive loading has ... |
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| Reliability and Stability Assessment of Concrete Gravity Structures (RCSLIDE): User's Guide |
JUL 2000 |
350 pages |
| Authors:
Mary Ann Leggett; Michael E. Pace; Fredrick Lyles; Kevin Abraham; ENGINEER RESEARCH AND DEVELOPMENT CENTER VICKSBURG MS INFORMATION TECHNOLOGY LAB
|
| This report is a documentation of RCSLIDE, the reliability version of CSLIDE, a computer program for assessing the sliding stability of concrete gravity structures using the limit equilibrium method described in EC 1110-2- 291, "Stability Analysis of Concrete Structures." CSLIDE can compute the factor of safety against sliding considering the effects of numerous and varied conditions. The report is organized to present an overview of the ... |
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| Reliability and Stability Assessment of Concrete Gravity Structures (RCSLIDE): User's Guide |
JUL 2000 |
350 pages |
| Authors:
Mary Ann Leggett; Michael E. Pace; Fredrick Lyles; Kevin Abraham; ENGINEER RESEARCH AND DEVELOPMENT CENTER VICKSBURG MS INFORMATION TECHNOLOGY LAB
|
| This report is a documentation of RCSLIDE, the reliability version of CSLIDE, a computer program for assessing the sliding stability of concrete gravity structures using the limit equilibrium method described in EC 110-2-291, "Stability Analysis of Concrete Structures." CSLIDE can compute the factor of safety against sliding considering the effects of numerous and varied conditions. The report is organized to present an overview of the sliding ... |
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| A Large Deformation Finite Element Analysis of Soil-Tire Interaction Based on the Contact Mechanics Theory of Rolling and/or Sliding Bodies |
30 JUN 2000 |
10 pages |
| Authors:
Antoinette Tordesillas; MELBOURNE UNIV PARKVILLE (AUSTRALIA)
|
| This research program is aimed at the development of a soil-tire interaction model based on Contact Mechanics Theory. The model developed obviates the need for a priori knowledge of soil-tire contact properties and instead relies on directly and accurately measurable quantities. Other major research outcomes of this program include: 1) the first complete solution to the frictional contact problem between a granular material and a deformable ... |
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| Ruhedruck und Entspannungsbewegungen Ueberkonsolidierter Boeden. Zum Einfluss Negativer Porenwasserspannungen auf die Standsicherheit von Einschnittsboeschungen in Ueberkonsolidierten Boeden (Pressure and Tension- Reducing Movements of Over-Consolidated S |
2000 |
134 pages |
| Authors:
Hartmut Schulz; Peter Schick; UNIVERSITAET DER BUNDESWEHR MUENCHEN NEUBIBERG (GERMANY) INST FUER BODENMECHANIK UND GRUNDBAU
|
| In the first section one finds the results of tests to measure horizontal stresses in over-consolidated soils. The measurements have shown that the theorem for in situ effective horizontal stress based on the friction angle may not always be valid for plastic soils. The second section deals with calculating the factor of safety of cutting slopes in over-consolidated, fine- grained soils: earth pressure at rest, the swelling and reduction of ... |
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| New Statistical Textural Transforms for Non-Stationary Signals; Application to Generalized Multifractal Analysis |
2000 |
12 pages |
| Authors:
Antoine Saucier; Jiri Muller; CENTRE DE RECHERCHE EN CALCUL APPLIQUE MONTREAL (QUEBEC)
|
| We introduce a method to generate statistical textural transforms that improves the treatment of non-stationarity and leads to a sharper detection of the boundaries between distinct textures (texture segmentation). This method is based on a sliding window processing with fixed size. The basic idea proposed by the authors is to readjust the measuring window around each pixel so as to maximize homogeneity. We use this method with the dimensions D ... |
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| An Approach for Studying the Creep/Sliding Behavior of Planar Metal- Silicon Interface |
DEC 1999 |
65 pages |
| Authors:
Ioannis Farsaris; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| There has been considerable recent interest in interfacial sliding during creep of multi-phase materials. The effect of interfacial creep is crucial for the deformation of metal-matrix composites and thin film systems, where the isostrain condition between the constituent components is often violated. An experimental approach has been developed to investigate the deformation kinetics of planar interfaces, using a double-shear specimen geometry where the interfaces ... |
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| Micromechanical Modeling of Superplastic Materials |
21 SEP 1999 |
127 pages |
| Authors:
Namas Chandra; FLORIDA AGRICULTURAL AND MECHANICAL UNIV TALLAHASSEE
|
| In this work, superplastic deformation were studied at atomistic, mesoscopic and macroscopic levels with a special focus on the former two. At the atomistic level, we studied the energy and structure of symmetric tilt boundaries and examined the energy barriers during grain boundary sliding of Aluminum bicrystal. We also studied the effect of temperature and impurity atoms on the structure, energy and deformation of grain boundary sliding. ... |
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| Anti Tip-Off Device |
11 MAY 1999 |
|
| Authors:
Thomas A. DelGuidice; Fred W. Watson Jr; DEPARTMENT OF THE NAVY WASHINGTON DC
|
| An anti tip off device for rocket rockets adapted for collapsible tube-in-tube launchers is provided. The dual- diameter launch tube requires stabilization of the rocket within the larger diameter tube. The anti tip-off device has two segments which together form a hollow cylinder which fits over the nose section of a standard high explosive anti-armor rocket. A sliding surface is located around the circumference of the cylinder to provide support ... |
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| Influence of Loading Frequency on the Elevated Temperature Fatigue Behavior of Fiber-Reinforced Ceramic Composites |
15 JAN 1999 |
33 pages |
| Authors:
John W. Holmes; MICHIGAN UNIV ANN ARBOR CERAMIC COMPOSITES RESEARCH LAB
|
| Cyclic tension-tension experiments were conducted on a ceramic matrix composite of continuous Nicalon SiC-fibers in a calcium-aluminosilicate matrix. Two different stress ratios (R = sigma(min)/sigma(max)) were studied (R = 0.5 and R = 0.05) at a loading frequency of 200 Hz. Specimens tested at R = 0.05 were found to have a shorter fatigue life than specimens tested at R = 0.5. The fatigue limit (defined ... |
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| Recoilless and Gas-Free Projectile Propulsion |
23 APR 1998 |
12 pages |
| Authors:
Matthew J. Sanford; Larry E. Crabtree; Roger L. Ellis; James F. Cahill; OFFICE OF NAVAL RESEARCH ARLINGTON VA
|
| A recoilless and gas-free projectile propulsion device is provided. A hollow pressure vessel is sealed on a first end to an AFT end of a projectile in a launch tube. The pressure vessel is further open on a second end. A propellant charge filled pressure chamber, defined in a forward portion of the pressure vessel, has holes venting to the pressure vessel AFT thereof. A piston, sealed within the pressure ... |
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| Construction Productivity Advancement Research (CPAR) Program |
APR 1998 |
198 pages |
| Authors:
Kimberlie Staheli; David Bennett; Hugh W. O'Donnell; Timothy J. Hurley; ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS GEOTECHNICAL LAB
|
| Early methods of installing pipelines and utilities across rivers and streams involved excavation of trenches. After the placement of the pipeline, the trenches were backfilled to protect the pipeline from hazards. These early dredged crossings were generally sited at the channel crossing of the thalweg between bends of the river. Here the river is generally a wide, shallow rectangle. This location is chosen due to its hydraulic stability and the ... |
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| Evaluating the State Probabilities of M out of N Sliding Window Detectors |
FEB 1998 |
|
| Authors:
Peter Williams; DEFENCE SCIENCE AND TECHNOLOGY ORGANISATION CANBERRA (AUSTRALIA)
|
| The term M out of N sliding window detectors refers to processes that determine whether there have been M successes in a sequence of N binary trials, where the window (of N trials under examination) slides along a possibly infinite sequence stopping when the criterion (of M successes in N successive trials) is met. They are frequently used to model the operators of naval surveillance systems such as radar and ... |
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| Human Factors in Tele-Inspection and Tele-Surgery (ARPA) |
JAN 1998 |
|
| Authors:
Thomas B. Sheridan; Juanjuen Hu; James M. Thompson; MASSACHUSETTS INST OF TECH CAMBRIDGE
|
| Closed loop control of a telemanipulator such as is used for telesurgery is intolerant to loop time delay of more than 0.05 second. Such a system goes unstable, especially when force feedback is employed. The time delay inherent in modem high-bandwidth communication channels such as satellite or ISDN telephone systems is mostly attributable to required modulation/ demodulation time, and can easily exceed 0.5 second. (I) ... |
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| Sliding Mode Controller Design for Kinetic Energy Kill Vehicle in a Hostile Environment |
1998 |
10 pages |
| Authors:
Yuri Shtessel; Mark Brown; Kevin Moore; Richard Toomey; Koy Cook; ARMY SPACE AND MISSILE DEFENSE COMMAND HUNTSVILLE AL
|
| Current guidance and control systems for interceptor missiles use algorithins that require knowledge of the target. These systems are not robust to target maneuvers and disturbances. In this paper, we investigate the use of a novel controller named a Sliding Mode Controller (SMC). We consider two types of interceptors or kinetic energy kill vehicles (KEKVs): a ballistic missile and a cruise missile. Sliding mode controllers are robust, ... |
|
| Anti Tip-Off Device |
30 SEP 97 |
20 pages |
| Authors:
DEPARTMENT OF THE NAVY WASHINGTON DC
|
| An anti tip-off device for rocket rockets adapted for collapsible tube-in-tube launchers is provided. The dual-diameter launch tube requires stabilization of the rocket within the larger diameter tube. The anti tip-off device has two segments which together form a hollow cylinder which fits over the nose section of a standard high explosive anti-armor rocket. A sliding surface is located around the circumference of the cylinder to provide support for the ... |
|
| Joint U.S./ROK R&D Program for New Underground Ammunition Storage Technologies. Explosion Effects Modeling of Self-Sealing Underground Explosive Storage Chamber Designs |
FEB 97 |
60 pages |
| Authors:
Ali Amini; Eugene L. Foster; Colin J. Shellum; UTD INC NEWINGTON VA
|
| This study investigates the potential performance of self sealing chambers in rock as a means of containing the blast effects from an accidental explosion in an underground ammunition storage complex. The work was performed as part of the Joint U.S./ROK R&D Program for New Underground Ammunition Storage Technologies. A coherent method for modeling of self sealing systems is presented. This method illustrated that observations made during field investigations can be ... |
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| Superplasticity at High Strain Rates in Aluminum Alloys |
10 OCT 96 |
16 pages |
| Authors:
Kenji Higashi; OSAKA PREFECTURE UNIV SAKAI (JAPAN)
|
| The detailed experimental data of microstructural developments during the optimum thermomechanical treatments and superplastic properties in the wide deformation range have been investigated on fourteen P/M aluminum alloys with various chemical matrix compositions and different typed precipitate particles. It was revealed that the differences in both size and volume among the second phase particles, which increase with content of Zr, Cr, Mn or Y, affect on the recrystallization behavior, grain ... |
|
| Autonomous Control of Underwater Vehicles and Local Area Maneuvering |
SEP 96 |
359 pages |
| Authors:
David B. Marco; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| The major thrust of this work is the development and demonstration of new capabilities for the use of small autonomous vehicles in mine countermeasure applications. Key to the new capabilities lies in an open architecture tri-level software structure for hybrid control, of which this work is the first validated implementation. The two upper levels run asynchronously in computing logical operations based on numerical decision making, while the lowest, the Execution ... |
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| Split Gasket Attachment Method. |
23 JUL 1996 |
|
| Authors:
Paul E. Moody; DEPARTMENT OF THE NAVY WASHINGTON DC
|
| The present invention relates to a method and hardware for bonding together ends of a sealing strip. The method of the present invention comprises the steps of cutting a slot in both a first end and a second end of a sealing strip, inserting an attachment strip having a plurality of engaging members into the slot cut into the first end, applying adhesive to the second end of the sealing ... |
|
| Removable One-Piece Truck Bed Divider. |
MAY 1996 |
|
| Authors:
Peter R. Tkachuk; DEPARTMENT OF THE NAVY WASHINGTON DC
|
| A truck bed divider having a unitary, one-piece structure which may be easily positioned in and instantly removed from a truck bed includes a dividing portion having a plurality of bars for preventing articles in the truck bed from moving or sliding in the truck bed. The divider further includes top and bottom frame portions which are joined to the divider portion and which support the divider portion in the ... |
|
| Palletized Loading System (PLS) Flatrack Sideboard Kit Evaluation |
APR 96 |
11 pages |
| Authors:
A. C. McIntosh Jr; ARMY DEFENSE AMMUNITION CENTER AND SCHOOL SAVANNA IL
|
| The U.S. Army Defense Ammunition Center and School (USADACS), Validation Engineering Division (SMCAC-DEV), was tasked by USADACS, Supply Engineering Division (SMCAC-DES), to perform a sliding pallet test on the Palletized Loading System (PLS) flatrack sideboard kit (rear panel). One of the requirements of the PLS M1077 flatrack contract was for the fabrication of sideboards. The strength required of the sideboards could not be clearly defined as to the amount of ... |
|
| In Situ Analysis of the Tribochemical Films Formed by SiC Sliding Against Mo in Partial Pressures of SO2, O2, and H2S Gases |
FEB 1996 |
9 pages |
| Authors:
I. L. Singer; T. Le Mogne; C. Donnet; J. M. Martin; NAVAL RESEARCH LAB WASHINGTON DC
|
| X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) were used to identify gas reaction layers and tribochemical films formed during reciprocating sliding tests in an ultrahigh vacuum (UHV) tribometer. Tests were performed on UHV cleaned SiC pins and Mo flats during or after exposure to SO2, O2, or H2S gas at pressures around 40 Pa. XPS identified the gas reaction layers on Mo to be chemisorbed MoS2 and/or MoO2 ... |
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| Assessment of Grain Refinement by Microtexture Analysis in Thermomechanically Processed Al 2519 Alloy |
DEC 95 |
67 pages |
| Authors:
Steven L. Stancy; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| The first part of this study involved determining the mechanism by which elevated-temperature deformation occurred for selected tensile specimens from previous research on thermomechanically processed Al2519 alloy. Microtexture information in the form of discrete pole figures indicated that the most highly superplastic material had completely recrystallized and deformed via grain boundary sliding, whereas material that did not display superplastic behavior deformed via slip. The second part of the study was ... |
|
| The Gouging Phenomenon at Low Relative Sliding Velocities |
DEC 95 |
143 pages |
| Authors:
Kenneth R. Tarcza; TEXAS UNIV AT AUSTIN
|
| Surface gouging by metals in high-velocity sliding contact has been observed for more than thirty years in engineering applications involving rocket sleds, two-stage gas guns, and electromagnetic railguns. The onset of gouging is usually observed to occur at sliding velocities in excess of 100%) mIs (3821 ft/s). Previous investigations of the phenomenon have indicated that the gouging onset velocity is proportional to the yield strength and hardness of the materials ... |
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| Human Factors in Tele-Inspection and Tele-Surgery |
09 OCT 95 |
|
| Authors:
Thomas B. Sheridan; James Thompson; Jianjuen Hu; Mark Ottensmeyer; Jie Ren; MASSACHUSETTS INST OF TECH CAMBRIDGE
|
| In telesurgery a physician operates on a remote patient through a two-way communication and telerobot link. This first-year progress report describes development of a telesurgical simulator with force reflection and time delay, simulating what occurs with satellite communication. Also developed was a remotely controlled endoscopic tool. Using the simulator, preliminary experiments have been conducted with human subjects to evaluate alternative means to stabilize control movements under time delay, including a ... |
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| Shutter Door Assembly. |
19 SEP 1995 |
|
| Authors:
Paul E. Moody; DEPARTMENT OF THE NAVY WASHINGTON DC
|
| A torpedo tube shutter door assembly includes a series of segmented, abutting panels constituting a shutter door for selectively blocking an elongate opening formed in an outer hull of a submarine. The panels are movable between a closed position in which the panels fair to the outer hull and block the opening, and an open position in which the panels slid ably move away from the opening along a longitudinal ... |
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| Static and Fatigue Damage in High Temperature Composites |
14 SEP 95 |
95 pages |
| Authors:
G. J. Dvorak; Y. A. Bahei-el-Din; RENSSELAER POLYTECHNIC INST TROY NY
|
| This final report presents the experimental and theoretical work performed in our research program on static and fatigue damage in high temperature composites. The theoretical part focused on development and implementation of a new Transformation Field Analysis (TFA) for inelastic laminates, which employs unit-call, periodic array models, as well as averaging micromechanical models together with any constitutive law for thermo- viscoplastic and other inelastic deformation. Moreover, we have initiated modeling ... |
|
| Nonlinear Control of Missiles |
SEP 95 |
189 pages |
| Authors:
Kevin A. Wise; Jack L. Sedwick; Rowena L. Eberhardt; MCDONNELL DOUGLAS CORP ST LOUIS MO
|
| The problem of designing flight control system for high performance anti-air missiles is discussed in this report. The research addresses three areas of missile autopilot design. The first area investigates the application of nonlinear H-infinity optimal control for an integrated aerodynamic/thrust vector controlled missile. The second area investigates the design of autopilots for missiles using on-off reaction control valve actuators. A sliding mode control law is developed using H-infinity design ... |
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| The Use of Analog Track Angle Error Display for Improving Simulated GPS Approach Performance |
AUG 95 |
49 pages |
| Authors:
C. M. Oman; M. S. Huntley Jr.; S. A. Rasmussen; S. K. Robinson; JOHN A VOLPE NATIONAL TRANSPORTATION SYSTEMS CENTER CAMBRIDGE MA
|
| The effect of adding track angle error (TAE) information to general aviation aircraft cockpit displays used for GPS nonprecision instrument approaches was studied experimentally. Six pilots flew 120 approaches in a Frasca 242 light twin aircraft simulator using crosswind and turbulence. Twenty- five-mile-long approach geometries were used, with and without 45 degree dogleg turns on final approach. Performance and workload using three TAE display formats were compared against results with ... |
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| Eaton Throat-Valve Element Modifications Preliminary Report |
JUL 95 |
244 pages |
| Authors:
Marcela R. Stacey; James G. Arendts; Ray A. Berry; Gary E. Korth; Paul R. Schwieder; IDAHO NATIONAL ENGINEERING LAB IDAHO FALLS
|
| This report documents the development and findings of a computer model that simulates the behavior of the Eaton-Throat Valve Element (ETVE) prototype, and describes a proposed modification concept for the ETVE. This high speed valve was designed for the U.S. Army Research Laboratory, Aberdeen Proving Ground, MD, to control the simulation of the dynamic effects of a nuclear blast. The computer model reveals three main findings: (1) the ETVE chatters ... |
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| Split Gasket Attachment Strip. |
30 MAY 1995 |
|
| Authors:
Paul E. Moody; DEPARTMENT OF THE NAVY WASHINGTON DC
|
| The present invention relates to a method and hardware for bonding together ends of a sealing strip. The method of the present invention comprises the steps of cutting a slot in both a first end and a second end of a sealing strip, inserting an attachment strip having a plurality of engaging members into the slot cut into the first end, applying adhesive to the second end of the sealing ... |
|
| CTWALL - A Microcomputer Program for the Analysis of Retaining and Flood Walls . Computer-Aided Structural Engineering (CASE) Project. (User's Guide) |
DEC 94 |
156 pages |
| Authors:
Michael E. Pace; ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS INFORMATION TECHNOLOG Y LAB
|
| CTWALL is a computer program that assesses the stability of T-type retaining and flood walls. The purpose of the program is to assess these structures in accordance with EM 1110-2-2502 and ETL 1110.2-322. CTWALL will evaluate the overturning and sliding stability of a retaining or flood wall in accordance with the aforementioned criteria documents. This instruction report is organized to present CTWALL by describing the installation and equipment requirements, giving ... |
|
| Rock Foundations |
30 NOV 1994 |
232 pages |
| Authors:
CORPS OF ENGINEERS WASHINGTON DC
|
| This manual provides technical criteria and guidance for design of rock foundations for civil works or similar large military structures. This manual applies to HQUSACE elements, major subordinate commands, districts, laboratories, and field operating activities. The manual provides a minimum standard to be used for planning a satisfactory rock foundation design for the usual situation. Chapter 2 provides a discussion on design considerations and factor of safety. Chapter 3 provides ... |
|
| Advanced Solid Lubricant Films by Ion-Beam Assisted Deposition |
28 NOV 94 |
12 pages |
| Authors:
Irwin L. Singer; Robert N. Bolster; Larry E. Seitzman; Kathryn J. Wahl; Marshall B. Peterson; NAVAL RESEARCH LAB WASHINGTON DC
|
| NRL is developing advanced solid lubricating films for bearing assemblies. The films are deposited by ion-beam assisted deposition (IBAD) to thickness that can be controlled from 0.02 micrometers (1 micron inch) to greater than or equal to 1 micrometer (40 microns inch). Unlike evaporated or sputter-deposited films, IBAD films are dense and adhere well to virtually all solid surfaces. Durable films have been deposited on bearing steels, Ti alloys and ... |
|
| Ramp Junction. |
01 NOV 1994 |
|
| Authors:
Patrick R. Kane; Billie R. Karrh; Kit Mack; Samuel J. Oppedisano; DEPARTMENT OF THE NAVY WASHINGTON DC
|
| An apparatus for spanning the distance between a fixed first platform and a movable second platform includes a ramp; a first pivoting junction located between one end of the ramp and the fixed first platform, and a second sliding junction located between the other end of the ramp and the movable second platform. The first pivoting junction accommodates pitch, roll and heave motion between the fixed platform and the ramp ... |
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| Friction and Energy Dissipation at the Atomic Scale: A Review |
OCT 1994 |
13 pages |
| Authors:
I. L. Singer; NAVAL RESEARCH LAB WASHINGTON DC SURFACE CHEMISTRY BRANCH
|
| Discussions of energy dissipation during friction processes have captured the attention of engineers and scientists for over 300 years. Why then do we know so little about either dissipation or friction processes? A simple answer is that we cannot see what is taking place at the interface during sliding. Recently, however, devices such as the atomic force microscope have been used to perform friction measurements, characterize contact conditions, and even ... |
|
| Video Transmission for Quantized Variable Bandwidth Networks |
08 SEP 94 |
19 pages |
| Authors:
Christopher C. Yu; NAVAL RESEARCH LAB WASHINGTON DC
|
| Transmission of variable bit-rate sources, such as video, over channels with quantized rates is discussed. An optimal scheme for transmission, based on the Viterbi algorithm, is described. A sliding window sub-optimal algorithm is introduced which significantly reduces algorithmic complexity while maintaining near-optimum performance. Simulation of the performances of the optimal and sub-optimal algorithms, as well as comparisons to a constant bit rate channel is completed. Video compression, Asynchronous transfer mode ... |
|
| Superplastic Ceramics |
01 SEP 94 |
10 pages |
| Authors:
Oleg D. Sherby; Woo-Jin Kim; STANFORD UNIV CA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| Superplasticity is a newly observed phenomenon in ceramics, with the first publication appearing in 1986. The current program has centered on an experimental study of superplasticity in polycrystalline iron carbide. This material has been made superplastic by utilization of two processing methods: powder processing and ingot-processing. In both cases the end microstructure is a continuous phase of ultra-fine grained iron carbide. The ultra-fine grained powder processed material was successfully gas-pressure ... |
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| Superstrength Metal Composite Material and Process for Making the Same. |
02 AUG 1994 |
|
| Authors:
Norman P. Louat; Virgil Provenzano; M. A. Imam; Kuntimaddi Sadananda; DEPARTMENT OF THE NAVY WASHINGTON DC
|
| A metal composite material provides improved strength at all temperatures, in particular at those temperatures greater half the melting point of its matrix. The metal composite material is at least 50 volume percent hard particulate material in a matrix which is significantly more ductile than the hard particulate material. At or above 50 volume percent hard particulate material, each particle is surrounded by a thin film of the matrix material. ... |
|
| Twin Disc Gear Tooth Simulator |
MAY 94 |
125 pages |
| Authors:
Martin W. Eusepi; James F. Dill; MECHANICAL TECHNOLOGY INC LATHAM NY
|
| This report describes the results of an effort to develop a disc on disc test rig for evaluating lubricant load capacity. The goal of the program has been to develop a reliable disc on disc (or Twin Disc) test rig capable of providing more reliable and lower cost evaluation of lubricant load capacity than the Ryder gear test which is currently used. Disc rigs have been evaluated for this application ... |
|
| Lubricant Evaluation and Performance II |
FEB 94 |
475 pages |
| Authors:
Costandy S. Saba; Michael A. Keller; Kenneth K. Chao; Douglas K. Toth; Mary F. Borchers; DAYTON UNIV OH RESEARCH INST
|
| Thermal and oxidative stability, deposition and foaming techniques were developed for predicting the performance of candidate 4 cSt lubricants, polyphenyl ether (PPE), C-ether and other experimental fluids for use in advanced aircraft turbine engines. A novel sealed tube test was developed to study the rate of reaction in both liquid and vapor phase using only microliter quantities of the lubricants. Blending agents and/or diluents were used to improve the low ... |
|
| Remote Control of Transcranial Doppler (TCD) Probe During Centrifuge Exposures up to 9 +Gz |
JAN 94 |
6 pages |
| Authors:
Ulf I. Baldwin; Paul Werchan; Travis Eddy; SOUTHEASTERN CENTER FOR ELECTRICAL ENGINEERING EDUCATION INC ST CLOUD FL
|
| TCD systems have been successfully used in clinical practice for estimating cerebral perfusion by registering blood flow velocity in the middle cerebral artery. However, when used in centrifuges, probe movement during high +Gz have resulted in the loss of Doppler signal making interpretations of data very difficult. To solve this problem, the Doppler probe and three electrical motors were mounted on a tightly fitted helmet. Remote control of these motors ... |
|
| Mechanics of Failure of High Temperature Metal Matrix Composites |
22 DEC 93 |
248 pages |
| Authors:
Demitris A. Kouris; ARIZONA STATE UNIV TEMPE DEPT OF MECHANICAL AND AEROSPACE ENGINEERING
|
| Results of a three-year research effort aimed at developing an understanding of the factors controlling transverse strength and failure of intermetallic composites are presented. Experiments were conducted involving several aluminide matrix composites; two types of fibers were used in order to allow for large as well as small residual stresses. On the basis of the in situ observations and with the aid of high resolution strain mapping, the relevant damage ... |
|
| Wear Reduction in Ceramic Bearings by Surface Generated Pyrolytic Carbon Continuously Replenished by Ethylene Gas |
13 DEC 93 |
46 pages |
| Authors:
J. L. Lauer; L. C. Davis; RENSSELAER POLYTECHNIC INST TROY NY
|
| Sliding tests with a pin-on-disc tribometer and both sliding and rolling tests with a modified four-ball tester at bulk temperatures of about 500 deg C and contact pressures of about 2.2 GPa have demonstrated up to 80% reductions of friction and wear with silicon nitride surfaces when a stream of ethylene is directed into the conjunction region. The effects are even more pronounced when the ethylene is prenucleated by a ... |
|
| New Micro- and Macroscopic Models of Contact and Friction |
29 NOV 93 |
185 pages |
| Authors:
W. W. Tworzydlo; W. Cecot; J. T. Oden; C. H. Yew; COMPUTATIONAL MECHANICS CO INC AUSTIN TX
|
| This is the final report for the three year research project dedicated to the development of new asperity-based models of frictional interfaces. The main concept is to combine statistical homogenization methods with a realistic nonlinear finite element analysis of surface micro-asperities, and thus produce new asperity-based models of contact and friction. Research in the project started with the development of a complete theory and software for the statistical homogenization of ... |
|
| The Nanometer-Scale Mechanics of Gold Films |
23 NOV 93 |
30 pages |
| Authors:
P. Tangyunyong; R. C. Thomas; J. E. Houston; T. A. Michalske; R. M. Crooks; NEW MEXICO UNIV ALBUQUERQUE DEPT OF CHEMISTRY
|
| We have used interfacial force microscopy (IFM) to monitor the mechanical deformation of single nanometer-sized grains in Au thin films. Our results show that protruding grains, which represent early-stage delamination, display multiple deformation mechanisms including grain-boundary sliding and intragranular plasticity. The unprecedented load displacement control capability of the IFM provides data that is used for the first time to quantitatively distinguish and evaluate individual deformation processes. |
|
| Tribological Studies of Silicon for Magnetic Recording Applications (Invited) |
05 OCT 93 |
24 pages |
| Authors:
Bharat Bhushan; Vilas N. Koinkar; OHIO STATE UNIV COLUMBUS COMPUTER MICROTRIBOLOGY AND CONTAMINATION LAB
|
| Read-write sliders made of silicon using integrated-circuit technology offer advantages of low-cost and high volume production. In the present study our objective is to investigate whether the friction and wear performance of bare silicon is adequate for disk drive application or whether certain coatings/treatments are necessary for low friction and wear. Macrotribological experiments have been performed with various pin/slider materials and magnetic disks in a modified disk drive. Microtribological studies ... |
|
| Interface Phenomena in Metal-Ceramic Composites |
27 SEP 93 |
52 pages |
| Authors:
Rishi Raj; CORNELL UNIV ITHACA NY DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| This report describes theoretical and experimental results that link the properties of the heterointerface to the macroscopic mechanical behavior of metallic composites where the continuous phase is a metal and the hard phase is a ceramic (MMCs) or an intermetallic (IMCs). The results emphasize that the properties of the composites depend on the interaction between cohesive strength of the M/C or M/I interface and the physical microstructural scale of the ... |
|
| Numerical and Analytical Solutions to Benchmark Problems Related to Tunnel Mechanics |
01 SEP 93 |
122 pages |
| Authors:
Donald A. Simons; LOGICON R AND D ASSOCIATES LOS ANGELES CA
|
| In this report, five numerical approaches to problems of tunnel dynamics are compared with each other and--wherever possible--with exact analytic solutions. The medium is an idealization of a jointed rock mass. The intact rock is linear elastic-plastic with a pressure-dependent failure surface and associated plastic flow law. There are two orthogonal sets of equally spaced joints. Each joint is nonlinear elastic in the normal direction and linear elastic with Coulomb ... |
|
| Mine Avoidance and Localization for Underwater Vehicles Using Continuous Curvature Path Generation and Non-Linear Tracking Control |
SEP 93 |
74 pages |
| Authors:
Dean J. Cottle; NAVAL POSTGRADUATE SCHOOL MONTEREY CA DEPT OF MECHANICAL ENGINEERING
|
| Many underwater vehicles have been designed to follow a straight path using linear approximations about that path. Tracking a dynamic path of arbitrary but continuous curvature may often be desired. This will require a nonlinear controller with enhanced robustness properties. One point of this thesis is to show how nonlinear control using sliding modes may be applied to follow a dynamic path. In a mine warfare setting using Autonomous Underwater ... |
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| Microscopic Modeling of Tribological and Interfacial Phenomena |
31 JUL 93 |
|
| Authors:
Uzi Landman; GEORGIA INST OF TECH ATLANTA SCHOOL OF PHYSICS
|
| Atomic-scale energetics, structure and dynamical mechanisms underlying interfacial processes, in particular for systems when two materials are brought together, separated or slide against each other, are of fundamental importance for basic science and technology in areas such as interfaces, confined fluids, adhesion, tribology, junctions, lubrication, wear, surface modifications, and nano technology. Our research is focused on the development and implementation of methods of atomistic molecular dynamics simulations and applications to ... |
|
| Lock Operator for Inactive Magazine Door Locking Bolt System. |
27 JUL 1993 |
|
| Authors:
Craig Horton; DEPARTMENT OF THE NAVY WASHINGTON DC
|
| A lock operator located between a backing plate and sliding cover includes a pivot plate for activating and deactivating the main boltworks and a relocker, an overtravel stop assembly for sequestering the pivot plate to prevent relock, a spring braised knob for locking the pivot plate in the locked or unlocked position, a pin for locking the sliding cover, pivot plate and locking plate in the locked position and means ... |
|
| Solid Lubricants for Space Structures. Phase 2 |
14 JUN 93 |
97 pages |
| Authors:
T. S. Sudarshan; MATERIALS MODIFICATION INC FAIRFAX VA
|
| In this Phase 11 effort, copper-lead alloys of three different compositions (90-10, 75/25, and 50/50 copper-lead) were processed by swirl die continuous casting in the form of ingots and further processed into powders using the gas atomization method. The powders were compacted using shock campaction and hot isostatic pressing. Friction and wear studies revealed that the 75/25 alloys had the best friction and wear rates under a range of sliding ... |
|
| Properties of Interfacial Tribo-Films |
JUN 93 |
239 pages |
| Authors:
D. D. Makel; D. Kuhlmann-Wilsdorf; VIRGINIA UNIV CHARLOTTESVILLE SCHOOL OF ENGINEERING AND APPLIED SCIENCE
|
| Research has been conducted on the properties of interfacial films of the kind formed in the course of sliding wear, named 'tribo-films.' Using specialized instrumentation, in particular the so-called Hoop Apparatus and a Bridgman-Anvil Device, we have found many new insights into the fundamental mechanisms responsible for the phenomena observed during sliding. In particular, advances have been made in, (1) the understanding of lubrication through adsorbed films, (2) the fundamental ... |
|
| Integrated Fundamental Research on Current Collection |
JUN 93 |
53 pages |
| Authors:
Doris Kuhlmann-Wilsdorf; Leo Tran; VIRGINIA UNIV CHARLOTTESVILLE SCHOOL OF ENGINEERING AND APPLIED SCIENCE
|
| The aim of our research was to add to the basic understanding in the area of current collection with particular emphasis on topics likely to benefit practical objectives. Under sponsorship of this contract, 23 papers were published in the international literature. Additionally, 13 invited lectures and 11 contributed lectures on various aspects of this research were delivered at universities, research laboratories, and international conferences by the principal investigator and coworkers. ... |
|
| Inexpensive Capillary Discharge X-Ray Laser Driver |
28 MAY 93 |
35 pages |
| Authors:
Alexander M. Panin; MOXTEK INC OREM UT
|
| In Phase I of the research we computationally modelled a capillary discharge device capable of producing the necessary plasma conditions to demonstrate ASE in argon at a wavelength of about 700 angstroms. Phase 11 of the research will involve the development and diagnosis of the experimental apparatus necessary to demonstrate ASE in argon. The scaling and modification of that apparatus to demonstrate ASE at shorter wavelengths using higher-Z materials will ... |
|
| Diagnostics and Methods for Real-Time Laser Microchemistry |
31 MAR 93 |
7 pages |
| Authors:
Daniel Ehrlich; EHRLICH ASSOCIATES LEXINGTON MA
|
| Among the of the main goals of the program have been the development of digital real-time microchemical processes and diagnostics. Further objectives have been the design of a stable platform, and the mechanical subsystems and electronic circuits to provide real-time machine control. These will be the basis for the study of control and stabilization methods. Specific subassemblies designed were the massive 1.5- inch-thick steel plate, the mechanical frame support, the ... |
|
| The Processing and Mechanical Properties of High Temperature/High Performance Composites. Book 1. Constituent Properties of Composites |
28 FEB 93 |
336 pages |
| Authors:
Anthony G. Evans; Frederick A. Leckie; CALIFORNIA UNIV SANTA BARBARA DEPT OF MATERIALS
|
| Partial Contents: A Microcomposite Test Procedure for Evaluating the Constituent Properties of Ceramic Matrix Composites; Design, Analysis and Application of an Improved Push-Through Test for the Measurement of Interface Properties in Composites; Fiber Bundle Push-Out: A Technique for the Measurement of Interfacial Sliding Properties; Mechanics of the Fiber Pushout Test; Effects of Fiber Roughness on Interface Sliding in Composites; Fiber Coating Concepts for Brittle Matrix Composites; Preliminary Assessment of Mica ... |
|
| Macro- and Micro-Mechanics of Mixed-Mode Dynamic Fracture of Concrete. Part 1. Micro-Mechanic Analysis |
14 FEB 93 |
92 pages |
| Authors:
Chang-Te Yu; Zhikai Guo; A. S. Kobayashi; Neil M. Hawkins; UNIV OF WASHINGTON SEATTLE DEPT OF MECHANICAL ENGINEERING
|
| A hybrid experimental-numerical procedure was used to analyze the micro-mechanics of the mixed-mode, static and dynamic fracture of a concrete three-point bend specimen with an offset precrack. Four/two beam moire interferometry was usedto record simultaneously separating horizontal and vertical displacements associated with stable/rapid growth. An elasto-static/ elasto-dynamic finite element code was execute in its propagation mode with assumed crack closure stress (CCS) versus crack opening displacement (COD) and crack shearing ... |
|
| Newtonian Viscous Flow and Superplasticity in Fine Grained Metallic Alloys |
31 JAN 93 |
15 pages |
| Authors:
Oleg D. Sherby; Eric Taleff; Shih-Chung Cheng; STANFORD UNIV CA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| Superplasticity in crystalline solids is an area of expanding scientific and technical interest Superplastic materials are characterized by a high value of the strain-rate-sensitivity exponent, m. kinds of superplasticity have been identified: fine structure superplasticity (FSS) and internal stress superplasticity (ISS). In the case of FSS materials, a strain-rate-sensitivity exponent equal to about 0.5 is usually found and these materials deform principally by a grain-boundary-sliding (g.b.s.) mechanisms accommodated by slip, ... |
|
| Simulation-Based Performance Analysis of Several Types of Normalizers Under Correlated Stationary Noise Conditions |
21 JAN 93 |
|
| Authors:
Fyzodeen Khan; NAVAL UNDERSEA WARFARE CENTER NEWPORT DIV NEW LONDON CT NEW LONDON DETACHMENT
|
| The results of a simulation-based performance analysis of several types of normalization algorithms commonly considered for use in active sonar applications are presented. The techniques investigated are the mean value (MV), two pass peak shear (2PP), greater-of (GO) mean values and the ordered statistic (OS). Each algorithm incorporates a sliding, split window which encompasses the data to be used to compute the normalizing parameter and is centered on the data ... |
|
| Discrete Sliding Mode Control for Nonlinear Sampled Data Systems |
93 |
|
| Authors:
Jean M. Fernand; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH
|
| Nonlinear control theory has been successfully applied to continuous, nonlinear, autonomous plant models. Implementation of these continuous control laws, using digital computers, has relied upon high sample frequencies to approximate the performance of continuous control. This thesis extends the design of continuous sliding mode control to discrete and to sampled data systems. Continuous, nonlinear, autonomous, second order dynamic plant models are discretized using an approximation to a Taylor series expansion. ... |
|
| Integrated Fundamental Research On Current Collection |
OCT 92 |
|
| Authors:
Doris Kuhlmann-Wilsdorf; VIRGINIA UNIV CHARLOTTESVILLE DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| The aim of our research has been to add to basic understanding in the area of current collection with particular emphasis on topics likely to benefit practical objectives. Under sponsorship off this contract twenty three papers were published in the international literature as listed in the last section. Additionally, thirteen invited lectures and eleven contributed lectures on various aspects of this research were delivered at Universities, Research Laboratories and International ... |
|
| Tactile Sensing and Control in Humans and Robotic/Teleoperated Systems |
04 AUG 92 |
7 pages |
| Authors:
Mark R. Cutkosky; Robert Howe; Roland Johansson; Goran Westling; Benoni Edin; STANFORD UNIV CA DEPT OF MECHANICAL ENGINEERING
|
| The most significant result of the Stanford/Harvard/Umea collaboration is a promising new approach to grasp force control in manipulation with robots and teleoperators. Experiments at Umea showed that human subjects control grasp forces and apply manipulation strategies using information from fast-acting (FAI and FAII) tactile afferents which signal events such as the onset of slipping between the fingers and a grasped object. An information exchange between Umea and Stanford led ... |
|
| The Deformation Characteristics and Microstructural Dynamics of an AL- 10MG-0.1ZR Alloy |
JUN 92 |
|
| Authors:
James F. Buckley II; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| An investigation into microstructural evolution during processing and superplastic deformation of an Al-10Mg-0.1Zr alloy was conducted. Processing schedules were modified to enhance particle-stimulated nucleation of recrystallization and refine subsequent gain size. Strain rates varying over three orders of magnitude were utilized in subsequent testing of processed material. At lower strain rates of about 10-4 sec-1 coarsening of the microstructure was apparent and elongations of 277% were obtained. A strain rate ... |
|
| Tests for Determining Failure Criteria of Ceramics under Ballistic Impact |
JUN 92 |
137 pages |
| Authors:
Richard W. Klopp; Donald A. Shockey; SRI INTERNATIONAL MENLO PARK CA
|
| A three-year Balanced Technology Initiative (BTI) program to develop tests for determining the failure criteria of ceramics under ballistic impact is described. The phenomenology of the penetration of a confined ceramic block by a long rod penetrator was established by examining the fracture damage in targets after ballistic testing. The material properties that govern the penetration resistance of ceramics were deduced. Two plate impact tests-the high-strain-rate pressure/shear test and the ... |
|
| Micromechanics of Interfaces in High Temperature Composites |
30 MAY 92 |
131 pages |
| Authors:
Toshio Mura; Katherine T. Faber; NORTHWESTERN UNIV EVANSTON IL CENTER FOR QUALITY ENGINEERING AND FAILURE PREV ENTION
|
| Both theoretical and experimental approaches have been used to examine the micromechanics of interfaces in ceramic-matrix, fiber-reinforced composites. In order to examine variables which allow for the optimization of fracture, toughness, analytical solutions first were developed to describe the stress displacement fields for a cylindrical inclusion adjoining a surface of an elastic half-space (equivalent to a single fiber intercepting a matrix crack). This same equivalent inclusion model was used to ... |
|
| The Synthesis and Characterization of Tribophysical Layers on Diamond and Silicon Carbide Surfaces |
MAY 92 |
44 pages |
| Authors:
John T. Yates Jr; PITTSBURGH UNIV PA DEPT OF CHEMISTRY
|
| A new ultrahigh vacuum apparatus, dedicated to the study of the surface chemistry of diamond single crystals, has been completed and the first scientific experiments have been done. This apparatus incorporates XPS, LEED, ESDIAD, HREELS, and TPD facilities for the study of the fluorination and hydrogenation of diamond single crystals. The apparatus is being employed for studies of atomic hydrogen/deuterium adsorption on diamond(100) in initial experiments prior to the use ... |
|
| Comparison of Synchronization Techniques for the AFIT Direct Sequence Spread Spectrum System |
21 APR 92 |
82 pages |
| Authors:
Edward A. Bednar; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING
|
| The purpose of this study is to analyze and evaluate the performance of several code synchronization methods that could be used in the Air Force Institute of Technology's (AFIT) Direct-Sequence Spread Spectrum (DSSS) communication system. These methods include the sliding correlator, transmitted reference, sequential estimation, and three types of matched filters. The matched filters are the baseband matched filter, delay line matched filter, and the convolver. The criteria used for ... |
|
| A Review of the Processes that Control Snow Friction |
APR 92 |
47 pages |
| Authors:
Samuel C. Colbeck; COLD REGIONS RESEARCH AND ENGINEERING LAB HANOVER NH
|
| There is a long history of interest in snow friction, but it is still necessary to speculate about the details of the processes. Roughness elements and contact areas must be characterized before the basic processes can be well understood. These parameters change with movement over snow and, in fresh snow, probably change along the length of the slider. Friction results from a mixture of processes: dry, lubricated, and possibly capillary. ... |
|
| SHIPMO5: An Updated User's Manual Incorporating New Wave Spectra and Ship-Referenced Forces |
APR 92 |
|
| Authors:
Kevin A. McTaggart; Ross Graham; DEFENCE RESEARCH ESTABLISHMENT ATLANTIC DARTMOUTH (NOVA SCOTIA)
|
| The ship motion computer program SHIPMO has been revised to increase its capabilities in several different areas. The new version of the program can compute forces relative to local ship axes and the resulting incidence of motion-induced interruptions or sliding events. Seakeeping positions may now be offset from the ship center-line. The program now includes expanded wave spectra capabilities, including multi-directional spectra. Motion computations may include hydrodynamic end effect terms, ... |
|
| On-Line Identification of the Speed, Steering and Diving Response Parameters of an Autonomous Underwater Vehicle from Experimental Data |
MAR 92 |
179 pages |
| Authors:
Fredric G. Bahrke; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| The experimental response data from autonomous maneuvering using the NPS AUV II vehicle has been analyzed with a view to defining Kalman filters to provide on-line estimates of system parameters and their variability. Kalman filters, designed for parameter estimation are expected to be the first step in the development of autonomous fault detection systems for underwater vehicles. Secondly, extraction of vehicle hydrodynamic coefficients from these parameters can help to develop ... |
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| Constitutive Modelling for Granular Material under Finite Strains with Particle Slidings and Fabric Changes |
04 FEB 92 |
|
| Authors:
Ching S. Chang; MASSACHUSETTS UNIV AMHERST DEPT OF CIVIL ENGINEERING
|
| The overall objective of this research is to develop a constitutive model for granular material under finite strains with explicit consideration of particle sliding and the consequent fabric change. The specific objective of this research is focused on the development of a stress strain theory that accounts for the microstructure and the non-uniform strain field of the particle assembly. The developed theoretical model is evaluated by results obtained from computer ... |
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| Modelling of Heavily Loaded Lubricated Contacts |
FEB 92 |
|
| Authors:
Farshid Sadeghi; William D. McClug Jr.; Kyung-Hoon Kim; Kevin Osborn; Brian Lance; PURDUE RESEARCH FOUNDATION LAFAYETTE IN
|
| Thermal elastohydrodynamic (EHD) lubrication of rolling/sliding line contacts is investigated to develop an interactive computer program for prediction of lubrication system performance. The user inputs lubricant and mechanical system physical properties as well as operating conditions of load and speed for calculation of contact zone pressure, temperature, traction, and stresses. This program is one of the first to include thermal effects in calculations and, therefore, can more accurately assess the ... |
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| Superstrength Metal Composite Material and Process for Making the Same. |
31 JAN 1992 |
|
| Authors:
N. P. Louat; V. Provenzano; M. A. Imam; K. Sadananda; DEPARTMENT OF THE NAVY WASHINGTON DC
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| A metal composite material provides improved strength at all temperatures, in particular at those temperatures greater half the melting point of its matrix. The metal composite material is at least 50 volume percent hard particulate material in a matrix which is significantly more ductile than the hard particulate material. At or above 50 volume percent hard particulate material, each particle is surrounded by a thin film of the matrix material. ... |
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| Performance of Selected Fabrics on the Decontaminable Litter and Litter Mattress to Correct a Problem of Unexpected Sliding during Patient Loading on a C-9 (Nightingale) Aircraft |
30 JAN 92 |
35 pages |
| Authors:
William H. Reams; David L. Danley; ARMY BIOMEDICAL RESEARCH AND DEVELOPMENT LAB FORT DETRICK MD
|
| During evaluation of the decontaminable litter, Air Force personnel noted that a patient laying on a vinyl litter mattress slid unexpectedly while being carried up a 19 degree loading ramp of the C-9 (Nightingale) aircraft. To address this problem, a number of selected materials were fabricated into litter and mattress covers. The slipperiness of each product was measured by placing a subject on the test litter with or without a ... |
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| Laser Coating of Composites for Enhanced Wear and Corrosion Resistance |
28 JAN 92 |
|
| Authors:
Madhav R. Govindaraju; Arul Molian; P. Molian; LASER SCIENCE CO AMES IA
|
| A new technique has been developed to produce glassy surface coatings on Metal Matrix Composites (MMCs) based on laser induced chemical reduction of metal salts. The substrate is first coated with a paste containing concentrated salts of the elements to be coated (ex. nickel formate, cobalt acetate, phosphorous, etc.) along with a thickening agent. The rise in the surface temperatures during laser irradiation will lead to the decomposition of salts ... |
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| Solid Lubrication of Laser Grown Fluorinated Diamond Thin Films |
21 JAN 92 |
|
| Authors:
Bruce Janvrin; Madhav Rao; Deli Gong; Arul Molian; P. Molian; LASER SCIENCE CO AMES IA
|
| A laser chemical vapor deposition process has been developed to grow fluorinated diamond thin films on bearing material substrates including SiC and 440C stainless steel. The type of laser, carbon feedstock, laser-precursor gas interactions, and deposition conditions have been established. Analysis of laser grown films revealed that the films deposited on SiC consisted of a mixture of diamond and graphite while the films on 440C steel were composed of diamond, ... |
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| Downdating of Szego Polynomials and Data Fitting Applications |
02 JAN 92 |
20 pages |
| Authors:
William Gragg; Greg Ammar; Lother Reichel; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| Many algorithms for polynomial least squares approximation of real- valued function on a real interval determine polynomials that are orthogonal with respect to a suitable inner product defined on this interval. Analogously, it is convenient to computer Szego polynomials, i.e., polynomials that are orthogonal with respect to an inner product on the unit circle, when approximating a complex-valued function on the unit circle in the least squares sense. It may ... |
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| Lubricant Evaluation and Performance 2 |
JAN 92 |
|
| Authors:
Costandy S. Saba; M. A. Keller; H. A. Smith; R. E. Kauffman; D. K. Toth; DAYTON UNIV OH RESEARCH INST
|
| The development of improved methods is described for defining, measuring and assessing high temperature (500-750 F) lubricants for use in advanced aircraft turbine engines and the development of improved techniques for lubricant monitoring and lubricant condition monitoring for advanced lubricating fluids. Arrhenius plots were developed for describing the effective life of candidate 4 cSt lubricants, polyphenyl ethers and other experimental fluids as it function of time and temperature for selected ... |
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| Structural and Tribological Studies of MoS sub 2 Solid Lubricant Films Having Tailored Metal-Multilayer Nanostructures |
15 DEC 91 |
|
| Authors:
M. R. Hilton; R. Bauer; S. V. Didziulis; M. T. Dugger; J. M. Keem; AEROSPACE CORP EL SEGUNDO CA MECHANICS AND MATERIALS TECHNOLOGY CENTER
|
| Molybdenum disulfide (MoS2) solid lubricant films were prepared by rf magnetron sputtering on 440C steel, 52100 steel, and Si substrates. This study concentrated on films that were multilayer coatings of MoS2 with either Ni or Au-Pd(20%) metal interlayers. Multilayer thickness ranged from 0.2 nm to 1.0 run while the multilayer periodic spacing ranged from 3 to 10 nm. Scanning electron microscopy and X-ray diffraction revealed that the multilayer films had ... |
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| Thermomechanical Fatigue Characterization of an Angle Ply Metal Matrix Composite |
DEC 91 |
|
| Authors:
Wade H. Vaught; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING
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| An investigation was conducted to study the thermomechanical fatigue (TMF) response of a + OR - 45(2s) angle ply SCS-6/titanium-15-3 metal matrix composite (MMC). Load controlled in-phase TMF experiments were performed over the temperature range 149-427 C, with a cycle frequency of 0.02 Hz. Test equipment included a high temperature extensometer, quartz lamp radiative heaters controlled by a Micricon thermal control unit and TMF test control software, MATE263. Stress and ... |
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| Optimal Stochastic Sliding Mode Control of Underway Replenishment in a Random Sea |
DEC 91 |
|
| Authors:
Hsu-Sheng Fu; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| Motion control of underway replenishment operations is achieved through the use of sliding mode control with a Linear Quadratic Gaussian compensator design. External disturbances include first-order wave force and moment as well as slowly varying interaction forces and moments between the two ships. Feedback control is used to provide adequate stability of motions while feedforward control with disturbance estimation and compensation achieves the desired steady state accuracy. The results demonstrate ... |
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| Titanium Carbide-Graphite Composites |
08 NOV 91 |
75 pages |
| Authors:
Delwyn Cummings; ADVANCED TECHNOLOGY MATERIALS INC DANBURY CT
|
| Pure titanium carbide, titanium carbide with free graphite, titanium carbide/vanadium carbide alloy with free graphite, and titanium carbide with boron and free graphite were tested for friction and wear at 22,600, and 900 C. Test pins of the four compositions were machined from ignots prepared from melts. The test pins were drawn across hot pressed titanium carbide wear plates with 5 newtons of normal force. The lowest friction coefficient at ... |
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| Dynamic Model and Control of an Artificial Muscle Based on Contractile Polymers |
NOV 91 |
24 pages |
| Authors:
David L. Brock; MASSACHUSETTS INST OF TECH CAMBRIDGE ARTIFICIAL INTELLIGENCE LAB
|
| A dynamic model and control system of an artificial muscle is presented. The artificial muscle is based on a contractile polymer gel which undergoes abrupt volume changes in response to variations in external conditions. The device uses an acid-base reaction to directly convert chemical to mechanical energy. A nonlinear sliding mode control system is proposed to track desired joint trajectories of a single link controlled by two antagonist muscles. Both ... |
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| Techniques in Linear and Nonlinear Partial Differential Equations |
21 OCT 91 |
7 pages |
| Authors:
Louis Nirenberg; NEW YORK UNIV NY COURANT INST OF MATHEMATICAL SCIENCES
|
| The sliding method has been introduced, and the method of moving planes has been greatly extended and improved. These methods have been applied to a number of problems for fully nonlinear second order elliptic equations: (1) to treat symmetry and monotonicity of solutions in domains - even with nonsmooth boundaries; (2) prove existence, uniqueness, monotonicity of traveling waves in a cylinder, for problems arising in combustion theory and in biology, ... |
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| Selection and Specification of a Data Link Protocol for VSAT Based Inter-LAN Communications |
SEP 91 |
78 pages |
| Authors:
Eugene S. Benvenutti Jr; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| This thesis proposes an architecture for the development of inter- Local Area Network communication across a VSAT network. The architecture of a VSAT node consists of the entities node, bridge, buffer, transmitter, receiver, and frame assembler/disassembler. Each of these entitles contains a finite state machine, predicate/action tables, and local variables. A selective repeat, sliding window data link protocol for the Very Small Aperture Terminal architecture, the transmitter and receiver, is ... |
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| Determination of the Tribological Fundamentals of Solid Lubricated Ceramics. Volume 3. Appendices P through II |
SEP 91 |
|
| Authors:
Michael N. Gardos; HUGHES AIRCRAFT CO EL SEGUNDO CA ELECTRO-OPTICAL AND DATA SYSTEMS GROUP
|
| The fundamental nature of the research was exemplified by ab-initio predictions of the friction coefficient of single crystal diamond sliding against its mating diamond plane, and molecular dynamics calculations on single crystal calcium fluoride and barium fluoride interface shear forces. The test equipment developed for completing the model experiments included an Auger/ESCA tribometer capable of unidirectional and oscillatory sliding at room temperature, a scanning electron microscope tribometer designed for oscillatory ... |
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| Sliding Mode Control of Motions of Towed Ships |
SEP 91 |
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| Authors:
Arthur K. Samora; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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| A control system based on sliding mode control and the linear quadratic regulator is designed to stabilize the straight line motions of towed vessels. The control technique is through athwartship movement of the towline attachment point on the towed vessel. Control design is based on the linearized sway and yaw equations of motion. Numerical simulations for both the linearized and the nonlinear system are performed and demonstrate the added robustness ... |
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| A Frequency-Domain Method for Estimating the Incidence and Severity of Sliding |
30 AUG 91 |
|
| Authors:
Ross Graham; A. E. Baitis; William G. Meyres; DAVID TAYLOR RESEARCH CENTER BETHESDA MD SHIP HYDROMECHANICS DEPT
|
| A frequency-domain method of predicting the incidence of personnel or equipment sliding is presented which includes the (linearized) forces due to roll, pitch, longitudinal, lateral and vertical accelerations, and also the effects of non-zero mean heel. The predictions of the method are compared with the results of observations of at-sea sliding incidents, and good correspondence is obtained. A simple approximation for the duration of threshold exceedance probability density is described, ... |
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| Numerical Simulation of Fluid Flow in a Simple Rotor/Stator Pair |
JUN 91 |
|
| Authors:
Joseph J. McVeigh Jr; ARMY MILITARY PERSONNEL CENTER ALEXANDRIA VA
|
| This thesis describes a series of numerical experiments dealing with rotor/stator interactions in hydroturbines. The means of analysis was a nonconforming sliding spectral element method for the unsteady, incompressible Navier-Stokes equations in two-dimensional geometry. The variable parameter in the simulation was the rotor advance coefficient. A comparison of lifting forces, flow rate, dissipation and kinetic energy was conducted for the various test cases. Robustness of the numerical discretizations was demonstrated ... |
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| A Composite Discrete/Continuous Control of Robot Manipulators |
APR 91 |
|
| Authors:
Ju-Jang Lee; Yangsheng Xu; CARNEGIE-MELLON UNIV PITTSBURGH PA ROBOTICS INST
|
| In this report, a composite control scheme for the control of robot manipulators is proposed. Due to the modeling error or environmental uncertainties, robot motion may present a significant positioning error by using a conventional Computer-Torque Method. To improve tracking capability of robot manipulators, sliding mode control and nonlinear control algorithms have been introduced, but computation is costly, and thus a fast motion execution using simple computer sources is impossible. ... |
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| Historical Overview of Data Communication With Analysis of a Selective Repeat Protocol |
MAR 91 |
83 pages |
| Authors:
Patricia B. Jensen; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| This thesis is primarily divided into two parts. The first part provides an overview of the historical milestones in the development of the telecommunications industry; the computer industry, primarily the hardware technology, and the merging of the two industries. The milestones chosen and the details given were motivated by the current trends regarding the consolidation of the two fields of telecommunications and computers into the area which is referred to ... |
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| Investigation of Interfacial Shear Strength in SiC/Si3N4 Composites |
91 |
|
| Authors:
J. I. Eldridge; Ramakrishna T. Bhatt; J. D. Kiser; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CEN TER
|
| A fiber push-out technique was used to determine fiber/matrix interfacial shear strength (ISS) for silicon carbide fiber reinforced reaction- bonded silicon nitride (SiC/RBSN) composites in the as-fabricated condition and after consolidation by hot isostatic pressing (HIPing). In situ video microscopy and acoustic emission detection greatly aided the interpretation of push-out load/displacement curves. The as-fabricated and HIPed SiC/RBSN composites showed very different fiber push-out behavior as reflected by differently shaped load/ ... |
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| Bonding at Metal-Ceramic Interfaces in Hybrid Materials |
31 DEC 90 |
|
| Authors:
Rishi Raj; CORNELL UNIV ITHACA NY DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| Mechanical properties of metal-ceramic interfaces were measured at high temperatures. New methods were developed to measure the time and strain rate dependent properties of metal-ceramic interfaces under shear loading and under tensile loading. The shear experiment consisted of depositing a film of the ceramic on the metal and stretching the metal until periodic cracks developed in the ceramic film. Experiments on the copper/silica system demonstrated that these interfaces slide at ... |
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| Tribological Performance and Deformation of Sputter-Deposited MoS2 Solid Lubricant Films During Sliding Wear and Indentation Contact |
15 DEC 90 |
|
| Authors:
M. R. Hilton; R. Bauer; P. D. Fleischauer; AEROSPACE CORP EL SEGUNDO CA LAB OPERATIONS
|
| Microstructural aspects of the plastic deformation of sputter- deposited MoS2 solid lubricant films on 440C bearing steel are presented. The films were produced in three different laboratories using radio frequency, direct current, and radio frequency magnetron sources. Two-types of contacts were investigated: (1) sliding wear contact in a thrust-washer apparatus used to evaluate film tribological performance, and (2) brale indentation contact used to investigate cross-sectional morphology and adhesion. Scanning electron ... |
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| Robust Path Tracking of Autonomous Underwater Vehicles Using Sliding Modes |
DEC 90 |
|
| Authors:
Steven R. Chism; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| Accurate track keeping of autonomous underwater vehicles is necessary for the autonomous navigation of a vehicle through confined spaces, and in the presence of obstacles and cross-current environments. Uncertainties in the force coefficients and environmental disturbances, as well as the required accuracy lead to the need for a robust sliding mode control for successful vehicle operations. This thesis investigates the use of a cross track error guidance law with a ... |
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| Sliding Control Design and Implementation on a Single-Link Flexible Arm |
DEC 90 |
129 pages |
| Authors:
Chieh-Chuan Feng; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| The sliding model control is known as a robust control that is able to work under the uncertainties of modeling error and the environmental disturbances. The objective of this research is to design the simple control (sliding control) algorithms for a single-link flexible arm and to study the robustness due to varying payload. A general form of physical plant in state space is formulated. To achieve a continuous control, a ... |
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| Multiple Input Sliding Mode Control for Autonomous Diving and Steering of Underwater Vehicles |
DEC 90 |
214 pages |
| Authors:
Todd D. Hawkinson; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| Design and analysis of multiple input autopilots using sliding modes in order to achieve accurate horizontal and vertical plane control of an autonomous underwater vehicle over a wide variation of speeds is presented. The simulated vehicle is equipped with two (fore and aft) sets of dive planes and two sets of rudders. In addition, two vertical and two horizontal thrusters are provided for control during low speed or hovering operations. ... |
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| Seawater Hydraulic Vane Type Pump. |
29 NOV 1990 |
|
| Authors:
John P. Kunsemiller; Robert R. Young; DEPARTMENT OF THE NAVY WASHINGTON DC
|
| A vane type hydraulic energy translating device for pumping filtered seawater and which uses seawater as a lubricating fluid. The pump is a compact, light weight design in which the bearings and certain other critical components are fabricated from corrosion resistant, low friction, high strength materials. The vanes as well as flexible side plate members are formed of these corrosion resistant materials. The pump body is formed of high corrosion ... |
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| Determination of the Tribological Fundamentals of Solid Lubricated Ceramics. Volume 1. Summary |
NOV 90 |
|
| Authors:
Michael N. Gardos; HUGHES AIRCRAFT CO EL SEGUNDO CA ELECTRO-OPTICAL AND DATA SYSTEMS GROUP
|
| The goals, structure and highlights of a recently completed multiyear/multinational research program are described. The main driving force behind this effort was the aim to advance the technology base so engineers can successfully and confidentially design, build and operate solid lubricated ceramic tribocomponents in extreme environments. Specially designed friction and wear testers were employed to perform well-defined model experiment on single crystal and polycrystalline ceramics and solid lubricants. The research ... |
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| Nonlinear Dynamics and Control of Flexible Structures |
10 OCT 90 |
|
| Authors:
W. H. Bennett; H. G. Kwatny; G. L. Blankenship; O. Akhrif; C. LaVigna; TECHNO-SCIENCES INC GREENBELT MD
|
| Basic system requirements for space-based directed energy weapons will require unprecendented levels of control system performance to achieve slewing maneuvers for rapid retargeting and precision alignment of structural components supporting optical system components. Rapid, multiaxis slewing maneuvers will excite multibody dynamics involving nonlinear interactions with structural flexure. Advanced methods of modeling multibody systems with structural flexure are described and several issues in modeling slewing and pointing maneuvers for multibody systems ... |
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| TEM Lattice Imaging of the Nanostructure of Early-Growth Sputter- Deposited MoS2 Solid Lubricant Films |
30 SEP 90 |
|
| Authors:
Michael R. Hilton; Paul D. Fleischauer; AEROSPACE CORP EL SEGUNDO CA LAB OPERATIONS
|
| Transmission electron microscopy (TEM) was used to investigate the nanostructure of sputter-deposited molybdenum disulfide (MoS2) films. These films represent the early stages of growth under deposition conditions that produce a zone 2 columnar morphology. Analysis reveals that the early-growth film morphology consists of anisotropic (platelike) islands in which the (001) basal planes are generally perpendicular to the substrate (forming 'edge islands') or parallel to the substrate (forming 'basal islands'). Within ... |
|
| Proceedings of the Ship Control Systems Symposium (9th) Held in Bethesda, Maryland on 10-14 September 1990. Theme: Automation in Surface Ship Control Systems, Today's Applications and Future Trends. Volume 2 |
14 SEP 90 |
|
| Authors:
NAVAL SEA SYSTEMS COMMAND WASHINGTON DC
|
| Partial contents: Development of an expert system for navigation at sea; Knowledge based systems--the practical reality; Fault identification and restructurable control of Marine systems; Portable automatic control system for a ship with a controllable pitch propeller, a rudder and a bow thruster; Automatic navigator-included simulation for narrow, congested waterways; The maneuvering design workbook--an approach to controllability design; Technical considerations in ships control system procurement; Automation of warship power systems; Failure ... |
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| Autopilot Design for Autonomous Underwater Vehicles Based on Sliding Mode Control |
JUN 90 |
|
| Authors:
David E. Lienard; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| An autopilot is designed using Sliding Mode Control Theory that can control the speed and heading of a full six degree of freedom, nonlinear model that allows speed and heading to be treated as separate systems. Once control of heading and speed is established, depth control is achieved by a third control law. Although they are developed separately, the three individual control laws act simultaneously to provide robust control of ... |
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| An Investigation of the Mechanics of Discontinuities in Rock |
29 MAR 90 |
|
| Authors:
Michael E. Plesha; Bezalel C. Haimson; WISCONSIN UNIV-MADISON DEPT OF ENGINEERING MECHANICS
|
| We undertook a systematic investigation of the mechanics of discontinuities consisting of joints and fractures in rock. The specific objective was the development of a physically motivated constitutive law for discontinuity behavior which includes effects such as asperity wear and rubbliization. The approach was to idealize a discontinuity as consisting of a macroscopic slip surface with microstructural features consisting of interlocking asperity surfaces. An experimental program was concurrently conducted in ... |
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| Nozzle Assembly for Army Mass Delousing Outfit. Phase 1 |
15 FEB 90 |
|
| Authors:
John W. Burke; CARDINAL SCIENTIFIC INC WALDORF MD
|
| Studied a pediculicide meter and nozzle for use with the Kioritz DM-9 backpack sprayer as a mass human delousing system. The project was reduced to 3 interdependent design areas: metering method, meter actuation, nozzle design (site access). Five initial metering designs (sliding gate, vertical membrane, inclined membrane, rotary membrane, and piston plunger), located in the lower tank area, were tested. Testing of the units focused on consistency. Although the prototypes ... |
|
| Waco Lake, Bosque River, Texas, Brazos River and Tributaries, Texas. Embankment Criteria, Performance and Foundation Report |
JAN 90 |
|
| Authors:
ARMY ENGINEER DISTRICT FORT WORTH TX
|
| This report covers design, construction, and operational information on geotechnical features of the major elements of Waco Dam consisting of the embankment, spillway, and outlet works as well as operational performance of the project since its completion in 1965. Further, it presents information on the slide of a portion of the embankment during construction and information on redesign and reconstruction required for successful completion of the project. The report evaluates ... |
|
| Nonlinear Dynamics and Control of Flexible Structures |
12 DEC 89 |
|
| Authors:
W. H. Bennett; H. G. Kwatny; G. L. Blakenship; O. Akhrif; TECHNO-SCIENCES INC GREENBELT MD
|
| Basic performance requirements for space-based directed energy weapons involve unprecedented requirements for integrated control of rapid retargeting and precision pointing of space structures. Multibody interactions excite nonlinear couplings which complicate the dynamic response. Attempts to reduce flexure response for such weapon platforms by passive techniques alone may be inadequate due to stringent pointing requirements. The principal objective of the research program is the validation and testing of high precision, nonlinear ... |
|
| High Temperature Surface Interactions |
NOV 89 |
|
| Authors:
ADVISORY GROUP FOR AEROSPACE RESEARCH AND DEVELOPMENT NEUILLY-SUR-SEINE (FRAN CE)
|
| In today's climate of life extension for military aircraft, the topic of corrosion control assumes a role of greater importance. At its sixty-eighth meeting, the Structures and Materials Panel conference of specialists focussed on controlling the degradative effects of flight environments on aircraft engine materials. The meeting reviewed the chemical and mechanical mechanisms involved in degradative process and considered some state-of-the-art solutions. Emphasis in discussions centred on hot salt corrosion ... |
|
| Improved Electrical Cable for Vehicles. |
12 OCT 1989 |
|
| Authors:
John W. Monroe; DEPARTMENT OF THE ARMY WASHINGTON DC
|
| This patent application discloses an improved cable for connecting electrical components inside a combat vehicle, the cable being comprised of a plurality of tubes surrounding individual wire bundles inside the cable. The tubes are resistant to diametrical crushing and have low-friction outer diametrical surfaces to facilitate relative axial sliding between the tubes. When the combat vehicle is being electrically repaired or updated, damaged or obsolete wire bundles can be slid ... |
|
| Design and Investigation of a Dive Plane Sliding Mode Compensator for an Autonomous Underwater Vehicle |
SEP 89 |
|
| Authors:
Joo-No Sur; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| A sliding mode compensator for depth control of an autonomous underwater vehicle (AUV) using depth feedback only is designed. The controller is evaluated for a nominal linear model and optimized by a series of numerical experiments for a number of depth changing maneuvers. A state observer is used in order to estimate the unmeasurable states together with the sliding mode controller. The effects of varying control parameters are discussed. Compensator ... |
|
| Real Time Adaptive Control of an Autonomous Underwater Vehicle (AUV) |
SEP 89 |
|
| Authors:
Michael H. Davis; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| In this research the problem of designing a controller for the dive maneuver of an Autonomous Underwater Vehicle (AUV) is addressed. The highly nonlinear nature of the vehicle dynamics and the requirement for the fast maneuvering call for robust control techniques. In particular Variable Structure Control (VSC) combined with Adaptive Control (AC) techniques seem to yield satisfactory performance in terms of robustness, capability to adjust to different operating conditions, and ... |
|
| Re-Evaluation of the Lower San Fernando Dam. Report 3. The Behavior of Undrained Contractive Sand and Its Effect on Seismic Liquefaction Flow Failures of Earth Structures |
SEP 89 |
|
| Authors:
Andres Vasquez-Herrera; Ricardo Dobry; ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS GEOTECHNICAL LAB
|
| Soil test results are analyzed from 2 complementary viewpoints: the shear strength behavior of the soil (including steady-state lines, effective stress conditions at triggering of flow failure, and the pore water pressure needed for triggering) for both monotonic and cyclic loading; and the pore water pressure buildup and number of straining cycles needed for triggering during cyclic loading. The influence of several parameters is investigated, including: void ratio, minor effective ... |
|
| Re-Evaluation of the Lower San Fernando Dam. Report 1. An Investigation of the February 9, 1971 Slide. Volume 1. Text |
SEP 89 |
|
| Authors:
Gonzalo Castro; Thomas O. Keller; Stephen S. Boynton; GEI CONSULTANTS INC WINCHESTER MA
|
| The lower San Fernando Dam in California developed a major slide in the upstream slope and crest as a result of the 1971 San Fernando earthquake. The purpose of the investigation presented in this report was to test the validity of using steady state concepts and methodology to perform liquefaction analyses of the dam and to further investigate some aspects of the physical mechanism of the slide. The results of ... |
|
| User' Guide: A Three-Dimensional Stability Analysis/Design Program (3DSAD) Report 6, Free-Body Module |
SEP 89 |
|
| Authors:
Fred T. Tracy; Mary A. Leggett; ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS INFORMATION TECHNOLOG Y LAB
|
| 3DSAD (Three Dimensional Stability Analysis Design) performs an overturning and sliding stability analysis for complex three-dimensional structures. Specific structure types and general shapes can be handled. General modules are: geometry--to define, display, and compute mass properties; loads-- to define, display, and compute loads; analysis--to perform a base analysis assuming a rigid body on an elastic foundation; and free-body--to use clipping capability for a free-body analysis. The Free-Body Module is a ... |
|
| Re-Evaluation of the Lower San Fernando Dam. Report 2. Examination of the Post-Earthquake Slide of February 9, 1971 |
SEP 89 |
|
| Authors:
H. B. Seed; Raymond B. Seed; Leslie F. Harder; Hsing- Lian Jong; SEED (H BOLTON) INC ORINDA CA
|
| Data from seismoscopes located on the crest and an abutment indicated that the main slide movements occurred about 20 to 30 sec after the strong earthquake shaking had stopped. It can thus be inferred that the earthquake shaking triggered a loss of strength in the soils comprising the embankment, and that it was this loss of strength, rather than the inertial forces induced by the earthquake shaking, which led to ... |
|
| Computer-Aided Structural Engineering (CASE) Project. A Three- Dimensional Stability Analysis/Design Program (3DSAD). Report 2. General Loads Module |
SEP 89 |
|
| Authors:
Fred T. Tracy; Mary A. Leggett; ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS INFORMATION TECHNOLOG Y LAB
|
| Computer program 3DSAD does an overturning and sliding stability analysis for complex three-dimensional structures. Specific structure types and general shapes can be handled. General modules are: geometry--to define, display, and compute mass properties; loads--to define, display, and compute loads; analysis--to perform a base analysis assuming a rigid body on an elastic foundation; and free-body--to use clipping capability for a free-body analysis. Geometry is defined by two-dimensional cross sections swept or ... |
|
| Re-Evaluation of the Lower San Fernando Dam; Report 2: Examination of the Post-Earthquake Slide of February 9, 1971 |
SEP 89 |
|
| Authors:
H. B. Seed; Raymond B. Seed; Leslie F. Harder; Hsing- Lian Jong; SEED (H BOLTON) INC ORINDA CA
|
| Data from seismoscopes indicated that the main slide movements occurred about 20-30 sec after the strong earthquake shaking had stopped. It can thus be inferred that the earthquake shaking triggered a loss of strength in the soils comprising the embankment, and that it was this loss of strength in the soils comprising the embankment, rather than the inertial forces induced by the earthquake shaking, which led to the sliding of ... |
|
| Computations for Truck Sliding with TRUCK 3.1 Code |
AUG 89 |
|
| Authors:
Romesh C. Batra; MISSOURI UNIV-ROLLA DEPT OF ENGINEERING MECHANICS
|
| The vehicle and its primary components response can be studied by using the TRUCK computer code. Each component is characterized by its mass, center of gravity position, inertias and products of inertias. One might think that the mechanical properties of the springs will affect the motion of axles, racks etc. relative to the vehicle body but will not affect the overall motions of the assembly. But in the TRUCK computer ... |
|
| Kinetics and Mechanisms of Primary and Steady State Creep in B- and Al- Containing Alpha Silicon Carbide |
JUL 89 |
|
| Authors:
Robert F. Davis; Calvin H. Carter Jr; NORTH CAROLINA STATE UNIV AT RALEIGH DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| The steady state creep behavior of a number of high temperature structural ceramics have been measured and the results analyzed to determine the controlling mechanism. Pure polycrystalline silicon carbide, devoid of sintering aids, creeps by dislocation motion and climb. Silicon carbide containing B- and AL- sintering aids, creeps by grain boundary sliding controlled by diffusion mechanisms (grain boundary diffusion - Coble creep - below 1920K; lattice diffusion - Nabarro-Herring creep-above ... |
|
| Analyses of Power Consumption for Two Sliding Vane Type Compressors |
JUL 89 |
|
| Authors:
A. A. Mabanta; AERONAUTICAL RESEARCH LABS MELBOURNE (AUSTRALIA)
|
| An outline is given of the theoretical analyses carried out for estimating the power requirements of two sliding vane compressor designs, adapted for high speed operation, to determine if advantages exist over a trailing vane compressor, previously used for air scavenging in an experimental two stroke piston engine. Keywords: Two stroke cycle engines; Power consumption; Australia. (JHD) |
|
| Photodissociation of XeF2 (Xenon Difluoride) at 193 nm |
30 JUN 89 |
|
| Authors:
Jerry F. Bott; Raymond F. Heidner; John S. Holloway; John B. Koffend; AEROSPACE CORP EL SEGUNDO CA AEROPHYSICS LAB
|
| Interest in the spectroscopy of xenon difluoride (XeF2) has been stimulated by the xenon fluoride (XeF) laser, which operates on the B-X transitions at 351 and 353 nm and the C-A transitions at 483 nm. The vacuum ultraviolet (VUV) photolysis of XeF2 can be used either to obtain laser action on these transitions or to produce the several electronic states of XeF for kinetic studies. The XeF2 photodissociation laser has ... |
|
| Dynamic Friction of a Metal Runner on Ice. 1. Model Sled Test |
JUN 89 |
|
| Authors:
Kazuhiko Itagaki; Niklaus P. Huber; George E. Lemieux; COLD REGIONS RESEARCH AND ENGINEERING LAB HANOVER NH
|
| The effects of runner material and surface conditions on the friction between runners and ice were studied. A model sled was pushed over a 6-m-longice sheet and the reduction of speed of the sliding sled was measured. The friction calculated by the reduction of speed between two gates indicated that smooth runners showed lower friction at around -1 degree C than at around -10 degrees C, as expected, but the ... |
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| Development of Fuel Wear Tests Using the Cameron-Plint High-Frequency Reciprocating Machine |
MAY 89 |
|
| Authors:
Mahendra D. Kanakia; John P. Cuellar Jr.; Sidney J. Lestz; SOUTHWEST RESEARCH INST SAN ANTONIO TX BELVOIR FUELS AND LUBRICANTS RESEARCH FACILITY
|
| The objectives of this program were to develop laboratory bench fuel- wear test methodology using JP-8 and to evaluate the effects of additives to improve load-carrying capacity of JP-8 for use in diesel-powered ground equipment. A laboratory test using the Cameron-Plint High-Frequency Reciprocating machine evaluated the effects of various chemical and physical parameters influencing the lubricity of the distillate fuels. The test conditions were determined sufficient to eliminate the effect ... |
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| Planning Systems for Autonomous Legged Vehicles |
MAY 89 |
67 pages |
| Authors:
ENVIRONMENTAL RESEARCH INST OF MICHIGAN ANN ARBOR
|
| This report describes efforts to integrate the areas of mobility research and autonomous navigation in support of the Adaptive Suspension Vehicle program. Experimental research on the locomotion of Nubian goats is summarized. A decision model of terrain navigation based upon the experimental results is reported. The Computer Simulation of Animal based upon the experimental results is reported. The Computer Simulation of Animal Navigation, which implements the decision model, is presented. ... |
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| Convergence Rate of a Gram-Schmidt Canceller. Revision |
20 APR 89 |
|
| Authors:
Karl Gerlach; Frank F. Kretschmer Jr; NAVAL RESEARCH LAB WASHINGTON DC
|
| The open-loop Gram-Schmidt (GS) canceller is shown to be numerically identical with the Sampled Matrix Inversion (SMI) algorithm in the transient state if infinite numerical accuracy is assumed. Three forms of the GS canceller are discussed and analyzed-concurrent, non-concurrent, and sliding window processing. Convergence results for concurrent and non-concurrent SMI cancellers have been obtained in the past by Reed, Mallet, and Brennan under the assumption that the inputs are Gaussian. ... |
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| U. S. Army Workshop on Low Heat Rejection Engines (4th) |
31 MAR 89 |
|
| Authors:
LEEDS UNIV (UNITED KINGDOM)
|
| There are a number of characteristics exhibited by ceramic materials which may provide potential benefits for the reciprocating internal combustion engine. However, the brittle nature of these materials together with a variability in strength has created difficulties in applying ceramic materials to the engine environment. Although a wide range of physical properties is available from contemporary ceramic materials, a material offering consistently high strength has yet to be developed. For ... |
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| Evaluation of New Thermomechanical Constitutive Theory for Snow |
FEB 89 |
|
| Authors:
R. L. Brown; MONTANA STATE UNIV BOZEMAN
|
| The thermomechanical properties of snow have been described in terms of microstructural processes. The constitutive theory was formulated in a form consistent with the second law of thermodynamics. Deformation was described in terms of such microstructural processes as pressure sintering, shearing deformations within the necks connecting the ice grains, and intergranular glide. The matrix material (ice) was modeled as an elastic-viscoplastic material such that transient response as well as steady ... |
|
| Wear and Friction Characteristics of Self-Lubricating Copper- Intercalated Graphite Composites |
89 |
11 pages |
| Authors:
A. W. Ruff; M. B. Peterson; A. Gangopadhyay; E. Whitenton; WRIGHT LAB WRIGHT-PATTERSON AFB OH
|
| Composite materials consisting of copper metal-matrices with a solid lubricant phase of intercalated (NiCl2) graphite have been prepared and studied in sliding wear against type 440C stainless steel at normal temperatures in air. Results on the controlling wear and friction mechanisms in these materials are presented. Beneficial effects were found up to about 15 volume percent intercalated graphite. An analytical model has been developed that relates composite wear to mechanical ... |
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| Studies of Liquid Metal Flows and Power Losses in Ducts with Moving Conducting Wall, Slanted Magnetic Field, and Applied External Electric Potential |
NOV 88 |
|
| Authors:
John S. Walker; Samuel H. Brown; Neal A. Sondergaard; DAVID TAYLOR RESEARCH CENTER BETHESDA MD
|
| Advanced homopolar electrical machinery is being considered for many new applications. This applied research requires the development of mechanisms for transporting high current at low voltages between rotating and stationary members of the machines with minimal losses and maximal operational stability. Thus, liquid metals rather than more conventional brush technology are often used in the sliding electric contact region. Generally, these machines have large external magnetic fields in the region ... |
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| A Mathematical Model of the On-Deck Helicopter/Ship Dynamic Interface |
SEP 88 |
|
| Authors:
J. Blackwell; R. A. Feik; AERONAUTICAL RESEARCH LABS MELBOURNE (AUSTRALIA)
|
| A mathematical model of the on-deck helicopter/ship dynamic interface has been developed and implemented on an ELXSI 6400 computer. This work provides a capability for investigating helicopter/ship dynamic interactions, such as deck clearances on landing, swaying, toppling and sliding criteria, and tie-down loads. Different helicopter types can be readily examined, given their undercarriage representation. The model takes account of arbitrary ship motion, and includes features such as brakes on or ... |
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| Sliding and Debonding Inclusions |
15 AUG 88 |
|
| Authors:
T. Mura; NORTHWESTERN UNIV EVANSTON IL DEPT OF CIVIL ENGINEERING
|
| It was found by Mura and Furuhashi, J. App. Mech. 51 (1984) 308-310, when an ellipsoidal inclusion undergoes a uniform shear eigenstrain in the principal axis directions and the inclusion is free to slip along the interface, the stress field vanishes everywhere in the inclusion and the matrix. The main objective of the present grant DAAG29-85-K-0134 is to give more theoretical investigation on this amazing finding and to find applications ... |
|
| The Role of Thermoelastic Effects in the Scuffing Failure of Rolling/ Sliding EHD Contacts |
15 AUG 88 |
|
| Authors:
R. R. Johnson; T. A. Dow; NORTH CAROLINA STATE UNIV AT RALEIGH DEPT OF MECHANICAL AND AEROSPACE ENGINEER ING
|
| A two-dimensional numerical solution of the thermal Reynolds', elasticity, and energy equations resulted in predictions of the flow velocities and temperatures within the lubricant film between a crown roller and a rotating shaft. The results showed a good agreement with previously measured experimental data on the surface temperatures in an EHD contact and on the resulting frictional torques for both rolling and sliding. A pressure and temperature dependent viscosity was ... |
|
| Bellman Continuum (3rd) International Workshop (13-14 June 1988) |
JUN 88 |
|
| Authors:
PARIS UNIV (FRANCE)
|
| Partial Contents: Controlling Singularly Perturbed Uncertain Dynamical Systems; Singularly Perturbed Uncertain Systems and Dynamic Output Feedback Control; Asymptotic Linearization of Uncertain Multivariable Systems by Sliding Modes; Output Feedback Control of Uncertain Systems in the Presence of Unmodeled Actuator and Sensor Dynamics; Robust Model Tracking for a Class of Singularly Perturbed Nonlinear Systems via Composite Control; Collusive Equilibria in Stochastic Sequential Games with Limit of Average Payoffs; Optimal Bayesian Control of ... |
|
| Three-Dimensional Viscous Flow Analysis for Moving Bodies Past Fixed Structures |
13 MAY 88 |
44 pages |
| Authors:
Kelton T. Peery; Scott T. Imlay; AMTEC ENGINEERING INC BELLEVUE WA
|
| A prototype computer program has been written to calculate three dimensional viscous compressible flow past bodies in relative motion. The program solves the Navier-Stokes equations using multiple zones of mesh. During the Phase I research and development effort, routines were written to allow the meshes to move and to couple the solutions in adjacent zones along sliding boundaries. The importance of a well planned software structure was demonstrated. The code ... |
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| Earthquake Resistant Submarine Drydock Block System Design |
MAY 88 |
|
| Authors:
James K. Luchs Jr; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| This thesis develops a 3-degree of freedom submarine drydock blocking system computer aided design package. Differential equations of motion are developed to take into account high blocking systems, wale shores, and side block cap angles. The computer program is verified by a case study involving the earthquake sliding failure of the USS Leahy (CG-16). A parametric study is conducted to determine the effects of wale shores, isolators, and block stiffness ... |
|
| Re-Evaluation of the Stability of Large Concrete Structures on Rock with Emphasis on European Experience |
APR 88 |
|
| Authors:
K. Kovari; P. Fritz; EIDGENOESSISCHE TECHNISCHE HOCHSCHULE LAUSANNE (SWITZERLAND)
|
| The sliding stability of a rock mass forming th e foundation or the abutments of concrete dams, of a natural slope, or of a cut cannot be measured directly but merely conjectured. One knows, however, conversely, remedial measures which may enhance the existing stability. Attention must be paid to sliding hazard if the presence of adversely oriented discontinuities with considerable persistence is evident, if movements take place in the rock ... |
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| Thermomechanical Contact Phenomena and Wear of Sliding Seal Components |
30 MAR 88 |
|
| Authors:
Francis E. Kennedy Jr.; Beda M. Espinoza; Susanne M. Pepper; THAYER SCHOOL OF ENGINEERING HANOVER N H
|
| The objectives of this investigation were to better understand the tribological behavior of ceramic-coated rings sliding against carbon graphite and the thermocracking that occurs with some of the ceramic coatings. Sliding wear tests were conducted on Inconel 625 substrates coated with four different hard materials: chromium oxide, chromium carbide, titanium nitride, and tungsten carbide. Tests were also run to determine the corrosion behavior of the ceramic- coated rings in seawater. ... |
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| The Tensile Strength of Ice Containing Cracks |
08 MAR 88 |
|
| Authors:
Erland M. Schulson; THAYER SCHOOL OF ENGINEERING HANOVER N H
|
| Experiments have established that long, sharp cracks reduce the uniaxial tensile strength of equiaxed and randomly oriented aggregates of fresh- water ice strained at 0.001/s at -10 C, and that this reduction is in keeping with the dictates of linear elastic fracture mechanics. On the other hand, short cracks or long cracks that have been blunted by creep deformation have no effect on strength. In the latter cases, the tensile ... |
|
| Articulated Total Body Model Enhancements. Volue 3. Programmer's Guide |
FEB 88 |
|
| Authors:
Louise A. Obergefell; Ints Kaleps; Thomas R. Gardner; John T. Fleck; HARRY G ARMSTRONG AEROSPACE MEDICAL RESEARCH LAB WRIGHT- PATTERSON AFB OH
|
| The ATB Model is used at the Armstrong Aerospace Medical Research Lab. to study human body biomechanics in various dynamic environments, especially aircraft ejection with windblast exposure. To improve the model's predicted results and capabilities, a number of modifications have been made, including the capability to have segment contact ellipsoids block the wind from other segments, an option to prescribe velocity dependent wind forces, a correction to prevent angular drift ... |
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| Instantaneous Robot Motion with Contact Between Surfaces |
JAN 88 |
|
| Authors:
Chunsheng Cai; STANFORD UNIV CA DEPT OF COMPUTER SCIENCE
|
| This research analyzes, the motion constraints needed to maintain direct contact between two rigid bodies, when one or both bodies are being moved under computer control. The author first studies the time-based instantaneous contact kinematics, then develops a control formulation and specifications within the AL robot language for moving so as to maintain the desired contact. Also studied is the impact which results when bodies are moved into direct contact. ... |
|
| Steel Hardness Effects in Boundary Lubricated Sliding: An In-Situ SEM (Scanning Electron Microscope) Study |
88 |
|
| Authors:
W. Holzhauer; S. J. Calabrese; RENSSELAER POLYTECHNIC INST TROY N Y DEPT OF MECHANICAL ENGINEERING
|
| A pin-on cylinder test apparatus was used to perform low speed, steel-on-steel sliding experiments in-situ in a scanning electron microscope (SEM). Through modifications to the SEM, these experiments could be run with a thin film of hydrocarbon oil applied to the sliding surface. Studies have been performed using AISI 4340 steel, both annealed and through hardened, for the pin and cylinder in combinations of soft (annealed)-versus-soft, hard-versus-soft and hard-versus-hard. All ... |
|
| Sliding Duct Seal. |
15 DEC 1987 |
|
| Authors:
Andrew MacGee; DEPARTMENT OF THE AIR FORCE WASHINGTON DC
|
| A seal assembly for forming an air seal around conduits or accessories crosses aircraft engine bypass ducts. The seal assembly comprises a seal retainer plate, a seal plate and a seal ring. The seal ring has two opposingly sprung legs which seat and form air seals at the duct wall and the seal plate. |
|
| Fatigue '87. Papers presented at the International Conference on Fatigue and Fatigue Threshold (3rd) Held in Charlottesville, Virginia on June 28-July 3, 1987. Volume 3 |
15 OCT 87 |
|
| Authors:
R. O. Ritchie; E. A. Starke Jr; VIRGINIA UNIV CHARLOTTESVILLE SCHOOL OF ENGINEERING AND APPLIED SCIENCE
|
| Fracture by the progressive growth of incipient flaws under cyclically varying loads, i.e., by fatigue, must now be considered as the principal cause of in-service failures of engineering structures and components, whether associated with mechanical sliding and friction (fretting fatigue), rolling contact, aggressive environments (corrosion fatigue), or elevated temperatures (creep-fatigue). Of particular importance are the early stages of fatigue damage, involving the initial extension of microcracks and their subsequent growth ... |
|
| Computer-Aided Structural Engineering (CASE) Project. Sliding Stability of Concrete Structures (CSLIDE) |
OCT 87 |
|
| Authors:
Michael E. Pace; Virginia R. Noddin; ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS INFORMATION TECHNOLOG Y LAB
|
| This report is a documentation of the computer program (CSLIDE) which was developed to assess the sliding stability of concrete structures using the limit equilibrium method described in ETL 1110-2-256, Sliding Stability for Concrete Structures. CSLIDE can compute the factor of safety against sliding considering the effects of numerous and varied conditions. The report is organized to present an overview of the sliding analysis and the capabilities of the program, ... |
|
| Tactile Sensing and Inverse Problems |
OCT 87 |
|
| Authors:
R. Yang; P. S. Krishnaprasad; MARYLAND UNIV COLLEGE PARK
|
| In recognizing a grasped object or grasp an object stably with a multifingered robotic hand, tactile sensors mounted on robot fingers have been identified as essential detecting tool. In general, grasp stability has two requirements: sliding avoidance and excess force avoidance. Hence, it is required that a tactile sensor be able to detect the nature of the force distribution which exists between the surface of the grasped object and the ... |
|
| Engineering/Cost Evaluation of Options for Removal/Disposal of NC (nitrocellulose) Fines |
30 SEP 87 |
|
| Authors:
A. A. Balasco; J. M. Nystrom; J. J. Stahr; L. L. Smith; LITTLE (ARTHUR D) INC CAMBRIDGE MA
|
| An evaluation of the various options for recovering and treating/ disposing of the nitrocellulose (NC) present in the manufacturing wash streams at the Radford Army Ammunition Plant (RAAP) was undertaken by Arthur D. Little, Inc., for the U.S. Army Toxic and Hazardous Materials Agency (USATHAMA). The technologies evaluated included: Sliding bowl centrifugation for preconcentration; Cross-flow microfiltration for final concentration; Solid bowl centrifugation for final concentration; Incineration for disposal of NC ... |
|
| Interface Effects on the Mechanical Properties of Ceramic Composites |
SEP 87 |
|
| Authors:
D. B. Marshall; ROCKWELL INTERNATIONAL THOUSAND OAKS CA SCIENCE CENTER
|
| Macroscopic and microscopic mechanical properties of ceramic composites have been investigated. A fracture mechanics analysis was developed to evaluate the influence of residual microstructural stresses on the fracture toughness of composites that are reinforced by crack bridging mechanisms. The magnitude and sign of the toughening were found to be very sensitive to the details of the bridging mechanism and the criterion for ligament rupture. These results highlight the need for ... |
|
| Far Infrared and Dielectric Relaxation Spectra in Supercooled Water and Water + Propylene Glycol Solutions |
AUG 87 |
|
| Authors:
L. Boehm; D. L. Smith; C. A. Angell; PURDUE UNIV LAFAYETTE IN DEPT OF CHEMISTRY
|
| We report the first measurements of the far IR absorption in supercooled water, the extend the temperature range of study of the most interesting feature, and H bond stretching mode at approx. 200/cm, to 85 C by incorporation of propylene glycol, PG, as solute. Low frequency dielectric relaxation measurements on a series of glass-forming PG + water solutions spanning the ra ge 30-100% PG when fitted to the Vogel-Tammann-Fulcher equation ... |
|
| The WAFTER (Wear and Friction Tester): A Versatile Wear and Friction Tester |
JUN 87 |
|
| Authors:
P. Jewsbury; MATERIALS RESEARCH LABS ASCOT VALE (AUSTRALIA)
|
| This report describes the design and use of a pins-on-disc wear and friction testing machine which has been constructed for use by the Wear Technology Group. The tester is capable of assessing sliding wear at speeds up to 4 m/sec and loads up to 40 N. During a wear run the friction and contact resistance are constantly monitored giving a clear picture of the condition of the surfaces. |
|
| Safe/Arm Explosive Transfer Mechanism. |
26 MAY 1987 |
|
| Authors:
Norman E. Jensen; Bennett W. Kelley; DEPARTMENT OF THE AIR FORCE WASHINGTON DC
|
| A safe/arm mechanism for an air-delivered explosive device uses a slider containing explosive leads as the means of interrupting the explosive train. The slider is locked in the safe position such that the explosive leads are out-of-line with respect to the detonator. The slider is attached directly to the main parachute such that when two locks are removed the parachute deployment forces can overcome a shear pin lock and move ... |
|
| Theoretical Manual for Design of Cellular Sheet Pile Structures (Cofferdams and Retaining Structures) |
MAY 87 |
|
| Authors:
Mark Rossow; Edward Demsky; Reed Mosher; ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS INFORMATION TECHNOLOGY LAB
|
| This theoretical manual contains derivations and discussions of procedures for cellular sheet pile cofferdam design. As a companion volume to the planned Engineer Manual, 'Design of Cellular Sheet Pile Structures', it is intended to provide theoretical background for that Engineer Manual as well as to the user of the computer program for cellular-cofferdam design, CCELL. Numerical examples illustrating the design methods' use, along with a broad list of references, are ... |
|
| Study of High Temperature Failure Mechanisms in Ceramics |
APR 87 |
|
| Authors:
Richard A. Page; James Lankford; SOUTHWEST RESEARCH INST SAN ANTONIO TEX DEPT OF MATERIALS SCIENCES
|
| This report summarizes the results of a fundamental study involving experimental characterization and analytical modeling of grain boundary cavitation and creep crack growth in ceramics exposed to pure tensile loading. The major experimental techniques employed in the program are the use of small- angle neutron scattering to characterize cavity nucleation and growth and stereoimaging analysis to characterize the stress and strain fields associated with growing creep cracks. The major accomplishments ... |
|
| Nonlinear Response of Concrete Gravity Dams to Strong Earthquake- Induced Ground Motion |
MAR 87 |
|
| Authors:
Paul F. Mlakar; JAYCOR VICKSBURG MS
|
| This report documents an investigation of the behavior of concrete gravity dams subjected to earthquake motions of sufficient strength to induce cracking. Nonlinear, dynamic, finite element analyses of three dams subjected to the Parkfield earthquake motion are conducted with the ADINA84 code. In the analyses the essential characteristics of static preloading, bidirectional seismic motion, dynamic concrete cracking, and hydrodynamic interaction are modeled. The results show that cracked zones can propagate ... |
|
| Superplasticity: A Fundamental Investigation on Deformation Mechanism and Cavitation Phenomena |
28 FEB 87 |
|
| Authors:
A. Chokshi; T. Bieler; A. K. Mukherjee; CALIFORNIA UNIV DAVIS DIV OF MATERIALS SCIENCE AND ENGINEERING
|
| Al-Li alloy, and the mechanically alloyed IN91211 were investigated for superplasticity and enhanced plasticity. The optimum test condition for superplastic deformation, the associated grain boundary sliding and flow localization at non-optimum condition were investigated for Al-Li alloy. The enhanced plasticity at comparatively high strain rates was investigated in IN91211. The mechanical data were analyzed using the concept of threshold stress. The nature and temperature dependence of this threshold stress are ... |
|
| Fine-Scale Mechanical Properties of Sliding Solids |
28 FEB 87 |
|
| Authors:
J. D. Ross; H. M. Pollock; LANCASTER UNIV (ENGLAND) DEPT OF PHYSICS
|
| This report describes fine-scale contact experiments specifically designed to investigate the mechanical properties of materials at the submicroscopic level. The first part deals with experiments carried out using an ultra-high vacuum (UHV) mechanical microprobem in which adhesion and friction are measured between a sharply-pointed metal tip and a flat surface at very light loads. The results show that, for a metal-metal or metal-ceramic interface, the adhesion and frictional resistance to ... |
|
| Anchoring System for Concrete Floating Pier. |
10 FEB 1987 |
|
| Authors:
Tung Y. Lin; DEPARTMENT OF THE NAVY WASHINGTON DC
|
| The device is a floating pier with a sliding pile anchoring system arrangement that avoids rigid connections to the pier and allows the pier to rise and lower with the tides and to remain level during lateral displacement while avoiding substantial tilt or rotation of the pier during seismic and maximum static loading. Preferably, piles that are arranged in pairs and are spaced along the centerline of the floating pier ... |
|
| The Shock Vibration Bulletin. Part 3. Isolation and Damping, Vibration Test Criteria, and Vibration Analysis and Test |
JAN 1987 |
210 pages |
| Authors:
NAVAL RESEARCH LAB WASHINGTON DC SHOCKAND VIBRATION INFORMATION CENTER
|
| Partial contents: Free decay damping tests; Response of a sequential damper to shock inputs; Liquid spring design method for shock isolation system applications; Design and test of a spacecraft instrument shock isolator; Dynamic analysis of a structure with sliding base; Modal control based limiting performance formulation for shock excited systems; Analysis of the effect of early warning on optimal shock isolation; TECOM's research in the dynamic environments; Development of laboratory ... |
|
| Multitechnique Studies on Fretting Fatigue: Influence of Surface Treatment |
NOV 86 |
|
| Authors:
Harro Sander; BUNDESANSTALT FUER MATERIALPRUEFUNG BERLIN (GERMANY F R)
|
| In the experimental program a specially constructed apparatus was used to simulate conditions at the faying surfaces in a structural joint. Fretting fatigue tests were carried out on 34 Chromium Nickel Molybdenum 6/ 100Cr6 steels using stress ratios from the range of finite endurance. Two methods of surface treatments are used: polishing and shaping. Two directions of each surface treatment are considered: parallel and perpendicular to the sliding direction. The ... |
|
| The Influence of Surface Chemistry on MoS2 Transfer Film Formation |
25 JUL 86 |
|
| Authors:
Paul D. Fleishchauer; Reinhold Bauer; AEROSPACE CORP EL SEGUNDO CA LAB OPERATIONS
|
| A variety of MoS2 films having different initial surface compositions and different degrees of reaction in oxidizing atmospheres have been prepared by sputter deposition onto 440 C steel substrates. The compositions of these films, including their degree of oxidation and their molybdenum-sulfur stoichiometry, have been determined by x-ray photoelectron and Auger electron spectroscopy immediately before the films were subjected to sliding wear tests. These tests, which used an in-house, ring-on-disk ... |
|
| Variable Cycle Engine for High Altitude Aircraft. |
08 JUL 1986 |
|
| Authors:
G. D. Brewer; DEPARTMENT OF THE AIR FORCE WASHINGTON DC
|
| In this patent, a turboshaft engine is modified to be able to operate as a turbojet or a turboprop by the movement of an annular slide valve that directs gas flow between a high pressure turbine and a low pressure turbine. |
|
| Task Force on Emergency Evacuation of Transport Airplanes. Volume 2. Supporting Documentation |
JUL 86 |
|
| Authors:
FEDERAL AVIATION ADMINISTRATION WASHINGTON DC OFFICE OF FLIGHT OPERATIONS
|
| This is volume II of two volumes that report on the study of the emergency evacuation of transport airplanes that was sponsored by the Federal Aviation Administration (FAA). The study included the Public Technical Conference held by the FAA in September 1985 and the public meetings of the three technical working groups that were formed during the conference as part of a task force effort to coordinate the program. The ... |
|
| Metal Powders (Metall Pulver) |
JUN 86 |
|
| Authors:
NORDDEUTSCHE AFFINERIE AKTIENGESELLSCHAFT HAMBURG (GERMANY F R)
|
| This book discusses metal powders for powder metallurgy, specific topics include Electrolytic copper powder, Copper alloy powders, Lead powders, tin powders, Partially prealloyed powders, Premixes, Mixed powders to customers' specifications, Quality control, Packaging, storage, guarantee, Manufacture, Properties, Processing, Filters of sintered bronze, Bearings and parts of sintered bronze, Parts of sintered brass and German silver, Parts of sintered copper, Carbon brushes, Friction and sliding materials, Diamond tools, Metal powders and ... |
|
| Field Developmental Test of the Dual Barrel Automatic Injector, MARK II |
APR 86 |
|
| Authors:
K. E. Friedl; MADIGAN ARMY MEDICAL CENTER TACOMA WA
|
| This autoinjector is a two barrel, nose-activated automatic injector system that delivers the contents of both barrels intramuscularly with a single action by user. Field tests were conducted on 1920 prototype injectors randomly drawn from production. 1800 injectors were distributed to 600 soldiers of an Infantry brigade. Each soldier was instructed to carry three injectors in a small arms ammunition pouch on their load bearing suspenders for 18-21 days of ... |
|
| Study of High Temperature Failure Mechanisms in Ceramics |
APR 86 |
|
| Authors:
Richard A. Page; James Lankford; SOUTHWEST RESEARCH INST SAN ANTONIO TEX DEPT OF MATERIALS SCIENCES
|
| This report summarizes the results of a fundamental study involving experimental characterization and analytical modeling of grain boundary cavitation and creep crack growth in structural ceramics exposed to pure tensile loading. The major experimental techniques employed in the program are the use of small-angle neutron scattering to characterize cavity nucleation and growth and stereoimaging analysis to characterize the stress and strain fields associated with growing creep cracks. In the first ... |
|
| Reexamination of Jumps Across Quasistatically Propagating Surfaces under Generalized Plane Stress in Anisotropically Hardening Elastic-Plastic Solids |
MAR 86 |
|
| Authors:
R. Narasimhan; Ares J. Rosakis; CALIFORNIA INST OF TECH PASADENA DIV OF ENGINEERING AND APPLIED SCIENCE
|
| Strong discontinuities across quasistatically propagating surfaces in anisotropic elastic plastic solids under generalized plane stress have been reexamined allowing for some generality in constitutive response and taking into account the phenomenon of necking. Jumps in stresses have been ruled out on the basis of material stabiltiy postulates and a previous approach has been discussed. It has been noted that for elastic-perfectly plastic solids, sliding velocity discontinuities occur under restrictive and ... |
|
| Wear Improvement in Titanium Alloys by Ion Implantation. |
04 FEB 1986 |
|
| Authors:
Ronald G. Vardiman; DEPARTMENT OF THE NAVY WASHINGTON DC
|
| This invention relates to a method of making titanium alloy more resistant to sliding wear and fretting fatigue comprising the steps of: implanting carbon ions with at least one energy onto titantium alloy until at least 1 x 10 to the 17th power carbon ions/ sq. cm have fallen onto the titanium alloy, said energy level of carbon ions being implanted being greater than 10 KeV. A second method comprises ... |
|
| The Lubrication of Dynamically Loaded Concentrated Hard Line Contacts: Temperature and Pressure Measurements, |
FEB 1986 |
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| Authors:
M. J. Schouten; H. J. van Leeuwen; H. A. Meijer; TECHNISCHE HOGESCHOOL EINDHOVEN (NETHERLANDS) INST FOR POWER TRANSMISSIONS AND TRIBOLOGY
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| During more than 40 years, research into concentrated contacts with full film lubrication has been mainly restricted to stationary behaviour. It is not until recently, that dynamically loaded concentrated contacts have received attention from some investigators. With the advent of more sophisticated hardware and software, the interest from theorists into dynamically loaded concentrated contacts is growing. But, the literature of experimental results is even more scarce. In this paper some ... |
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| Nonlinear Analysis and Optimal Design of Dynamic Mechanical Systems for Spacecraft Application |
FEB 86 |
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| Authors:
K. D. Wilmert; M. Sathyamoorthy; CLARKSON UNIV POTSDAM NY DEPT OF MECHANICAL AND INDUSTRIAL ENGINEERING
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| A nonlinear finite element analysis procedure already developed for planar mechanisms is being modified to handle complex mechanisms with sliding masses and mechanisms operating at relatively high speeds. Progress is also being made in developing a suitable nonlinear finite element analysis procedure for three-dimensional mechanisms. In both cases the analysis takes into account the effects of geometric and material nonlinearities, vibrational effects and coupling of deformations. In the optimal design ... |
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| Contact Surface Erosion for Hypervelocity Problems |
FEB 86 |
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| Authors:
Kent D. Kimsey; Jonas A. Zukas; ARMY BALLISTIC RESEARCH LAB ABERDEEN PROVING GROUND MD
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| This paper presents a technique for extending the capability of Lagrangian wave propagation codes to treatment of deep penetration and spaced plate perforation problems. Lagrangian codes as originally developed required that the sliding interfaces specified at the beginning of a problem remain unchanged throughout the computation. This requirement was imposed not from physical considerations but to simplify the programming of the interface logic. Its effect was to prohibit total failure ... |
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| Computer Programs for the Determination of Stresses and Displacements in Four Layered Systems with Fixed Bottom |
FEB 86 |
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| Authors:
F. van Cauwelaert; M. Lequeux; F. Delaunois; CENTRE DE RECHERCHES DE L'INST SUPERIEUR INDUSTRIEL CATHOLIQUE DU HAINAUT (BELGUIM)
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| This report deals with the mathematical aspects required for the establishment of a computer program able to calculate all stresses and displacements in a four layered system. The materials of the different layers may be isotropic or coross anisotropic. The interface conditions cover all the cases from full friction to full slip included partial friction. The bottom of the fourth layer is considered to be fixed (no vertical deflections). The ... |
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| Nonskid Coating Formulations. |
22 JAN 1986 |
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| Authors:
Larry W. Kraft; Robert F. Brady; DEPARTMENT OF THE NAVY WASHINGTON DC
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| It is an object of the present invention to provide improved nonskid coating formulations having enhanced impact resistance and resistance to sliding movement thereon by aircraft or other equipment. It is a further object of the invention to provide nonskid coatings which will maintain their adhesion to primed steel after severe impact and thus eliminate the hazards caused by dislodged fragments. Yet another object of the invention is to provide ... |
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| United States Navy- Canadian Forces Solid State Flight Data Recorder/ Crash Position Locator Experiment on the B-720 Controlled Impact Demonstration |
11 NOV 85 |
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| Authors:
D. M. Watters; NAVAL AIR TEST CENTER PATUXENT RIVER MD
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| A prototype Solid State Flight Data Recorder/Crash Position Locator (SSFDR/CPL) developed jointly by the United States Navy/Canadian Forces was installed, tested, and evaluated aboard the Federal Aviation Administration/ National Aeronautics and Space Administration B-720 Controlled Impact Demonstration (CID) on 1 December 1984. The SSFDR contained eight Electronically Erasable Programmable Read Only Memory silicon nitride oxide semiconductors with prerecorded (alternating ones and zeros) data. The CPL Radio Beacon Airfoil (RBA) contained ... |
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| A Lagrange Multiplier/Segment Procedure for Solution of Three- Dimensional Contact Problems |
OCT 85 |
76 pages |
| Authors:
A. B. Chaudhary; K. J. Bathe; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF MECHANICAL ENGINEERING
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| A solution procedure for finite element analysis of three-dimensional contact conditions is presented. The area of contact can vary, frictional conditions are included using Coulomb's law of friction and static or dynamic conditions can be considered. Various sample solutions are presented to demonstrate the applicability of the solution algorithm. Keywords include: Contact Problem Algorithm, Finite Element Structural Analysis, Lagrange Multiplier Contact Forces, Multiplier/Segment Procedure, ADINA Finite Element Program, Frictional Sliding ... |
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Reports by Keyword(s)
SLIDING
