| CFD Prediction of Magnus Effect in Subsonic to Supersonic Flight |
Sep-2009 |
46 pages |
| Authors:
James DeSpirito; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
|
 | The aerodynamic coefficients of the 7-cal. U.S. Army-Navy Spinner Rocket were characterized using computational fluid dynamic (CFD) calculations and validated using archival experimental data. The static aerodynamic coefficients, roll-damping, and pitch-damping moments were accurately predicted by steady-state Reynolds-averaged Navier-Stokes (RANS) as well as unsteady hybrid RANS/large-eddy simulation (LES) CFD. The Magnus moment was overpredicted in the subsonic and transonic regime. Unsteady RANS/LES computations did not improve the prediction of Magnus ... |
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| Characterization of MEMS a Directional Microphone with Solid and Perforated Wings |
01-Jun-2009 |
57 pages |
| Authors:
Norbahrin Muamad; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| This goal of this research is to characterize two microelectromechanical system (MEMS) based directional sound sensors with solid and perforated wings. The design of the sensors was based on the structure of Ormia ochracea fly's hearing system that has highly directional hearing through mechanical coupling of the eardrums. The sensors are made of 10 micron thick single crystal silicon layer with dimensions 1 x 2 mm2. The sensors were fabricated ... |
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| Stability of Large-Scale Oceanic Flows and the Importance of Non-Local Effects |
Jun-2009 |
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| Authors:
Hristina G Hristova; WOODS HOLE OCEANOGRAPHIC INSTITUTION MA
|
 | My thesis covers two general circulation problems that involve the stability of large scale oceanic flows and the importance of non-local effects. The first problem examines the stability of meridional boundary currents, which are found on both sides of most ocean basins because of the presence of continents. A linear stability analysis of a meridional boundary current on the beta-plane is performed using a quasi-geostrophic model in order to determine ... |
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| Generic Design Procedures for the Repair of Acoustically Damaged Panels |
Dec-2008 |
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| Authors:
R J Callinan; C H Wang; S Sanderson; S C Galea; DEFENCE SCIENCE AND TECHNOLOGY ORGANISATION VICTORIA (AUSTRALIA) AIR VEHICLES DIV
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| Acoustic fatigue is the result of high frequency lateral vibration of an aircraft panel due to time varying pressure waves caused by engine and/or aerodynamic effects. For example, acoustically induced cracks have been recorded in the lower external surface of the nacelle skin of the F/A-18 aircraft and aft fuselage. In the case of the inlet nacelle overall sound pressure levels of the order of 172 dB have been recorded. ... |
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| Durability Testing of Polymer D Material |
16-Sep-2008 |
23 pages |
| Authors:
Matthew Tillman; William Koegel; Michael Bosak; David J Barrett; NAVAL AIR WARFARE CENTER AIRCRAFT DIV PATUXENT RIVER MD
|
| Viscoelastic damping materials are used to control resonant vibrations in mechanical and structural systems. Before these materials can be applied to a naval air application, they must demonstrate an ability to survive the aggressive marine environment. This report documents the results of a laboratory investigation into the durability of the Polymer D damping material. In general, Polymer D was found to have adequate durability as long as it is shielded ... |
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| Optically Defined Chemical Functionalization of Silicon Nanomechanical Resonators for Mass Sensing |
Aug-2008 |
5 pages |
| Authors:
Jeffrey W Baldwin; Maxim K Zalalutdinov; Bradford B Pate; Michael J Martin; Brian H Houston; NAVAL RESEARCH LAB WASHINGTON DC
|
| Nanomechanical resonators with their extremely small mass and high surface/volume ratio present a unique opportunity for mass sensing[1-4]. However, functionalization with selective vapor adsorptive functional groups has been an impediment to the realization of nanomechanical systems for mass sensing. Functional groups that adsorb analytes of interest should be patterned only on the nanoresonator itself, and should not be located on structural elements or micro-channel walls, which would greatly limit the ... |
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| Damping MEMS Devices in Harsh Environments Using Active Thin Films |
17-Jun-2008 |
26 pages |
| Authors:
Greg P Carman; Catherine A Kerrigan; CALIFORNIA UNIV LOS ANGELES DEPT OF MECHANICAL AND AEROSPACE ENGINEERING
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| We report on fabrication and damping measurement of NiTi and Terfenol-D thin films. A model for prediction of the damping properties (tan delta) of a laminate using the material properties of the layers was developed. Damping properties in Nitinol thin film due only to residual stresses was measured to be as high as tan delta = 0.17 for large strain (0.9%). At lower strain levels a Nitinol/Silicon laminate was tested ... |
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| Finite Element Analysis of Fluid-Structure Interaction in a Blast-Resistant Window System (PREPRINT) |
MAR 2008 |
51 pages |
| Authors:
Jae H. Chung; Gary R. Consolazio; Robert J. Dinan; Stephen A. Rinehart; FLORIDA UNIV GAINESVILLE DEPT OF CIVIL AND COASTAL ENGINEERING
|
| This paper describes the development of a finite element model capable of representing a blast-resistant flexible window (flex-window) system developed by the Air Force Research Laboratory, Airbase Technologies Division (AFRL/RXQ). Computational fluid-structure interaction finite element simulations are used to develop an improved understanding of the manner in which fluid phenomena, such as air compression and flow, affect the behavior of the flex-window system under blast loading. Compressible air flow interacting ... |
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| Investigation of the Transmission of Sound Through Isotropic, Damped Material Layer(s) Bounded by Seawater |
MAR 2008 |
69 pages |
| Authors:
Gerald J. Roche; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| Acoustic 'windows' are used in SONAR applications to absorb structural loads associated with the platform operation while allowing the passage of acoustic signals. The performance metric commonly used to gauge the acoustic window quality is insertion loss. This thesis provides a derivation of insertion loss for multi-layered materials as a function of frequency and angle of incidence. Derivations are modified to include attenuation of the signals in the material and ... |
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| The 2009 Version of the Aeroprediction Code: The AP09 |
JAN 2008 |
135 pages |
| Authors:
Frank G. Moore; Linda Y. Moore; AEROPREDICTION INC KING GEORGE VA
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| The AP05 code was evaluated when applied to configurations with boattails. Results of the evaluation indicated the AP05 predictions for normal force, center of pressure, pitch and roll damping moments needed improvement. As a result new and improved methods were developed and incorporated into the AP05 to be released as the AP09. Improvements include body alone lift characteristics for Mach numbers less than 2, low angle of attack improvements for ... |
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| Dynamic Response and Simulations of Nanoparticle-Enhanced Composites |
15 NOV 2007 |
246 pages |
| Authors:
P. R. Mantena; Ahmed Al-Ostaz; Alexander H. Cheng; MISSISSIPPI UNIV UNIVERSITY MS COMPOSITE STRUCTURES AND NANO ENGINEERING RESEARCH GROUP
|
| Objectives of this research are to characterize the: (a) vibration and acoustic response; (b) low-velocity impact and high-strain energy absorption; (c) effects of freeze-thaw cycling; and (d) molecular dynamics simulations of nanoparticle-enhanced composites and fly- ash based foams that are being considered for the future generation naval structures or retrofitting of existing ones. In this study, the flexural/extensional dynamic modulus, damping, low-velocity impact and high-strain (Hopkinson bar) response of nylon ... |
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| Vortex-Induced Vibration: Universal Phenomena in Diverse Systems |
OCT 2007 |
14 pages |
| Authors:
Charles H. Williamson; CORNELL UNIV ITHACA NY OFFICE OF SPONSORED PROGRAMS
|
| The long-term goals of the research under this award have been to discover and understand generic phenomena in a whole class of vortex-induced vibration systems. We discover, using novel controlled damping, that the immense scatter in the classical Griffin plot (peak amplitude versus mass-damping) over 3 decades, can now be collapsed beautifully if one renormalises the axes, taking into account the effect of Reynolds number, which was previously not considered. ... |
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| Finite Element Based Structural Damage Detection Using Artificial Boundary Conditions |
SEP 2007 |
183 pages |
| Authors:
Rafael A. Lagunes Arteaga; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| Finite element models can be used to discern the location and severity of damage in structures. This is frequently pursued by using the differences in measured and computed natural frequencies, in conjunction with the sensitivities calculated using the FE model. Given that a modal test produced a limited number of natural frequencies for a structure, the concept of Artificial Boundary Conditions (ABC) was developed, which yields additional natural frequency information ... |
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| Experimental Verification of a Systematic Method for Identifying Contact-Dynamics Model Parameters |
31-Jul-2007 |
39 pages |
| Authors:
Ou Ma; Jong Kim; Lucas Martinez; NEW MEXICO STATE UNIV LAS CRUCES
|
| This project is aimed at conducting an experimental test of a new and systematic method for identifying the key parameters of a general multiple-point contact dynamics model using a robotics-based experimental testbed. The hypothesis verified in this project is that the identification method is capable of identifying the stiffness, damping, and friction parameters all together from a same hardware test. Such an identification capability is very appealing to physical simulation ... |
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| A Model for the Propagation of Nonlinear Surface Waves over Viscous Muds |
05 JUL 2007 |
14 pages |
| Authors:
James M. Kaihatu; Alexandru Sheremet; K. T. Holland; TEXAS A AND M UNIV COLLEGE STATION DEPT OF CIVIL ENGINEERING
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| The effect of a thin viscous fluid -mud layer on nearshore nonlinear wave -wave interactions is studied using a parabolic frequency-domain nonlinear wave model, modified to incorporate a bottom dissipation mechanism based on a viscous boundary layer approach. The boundary-layer formulation allows for explicit calculation of the mud-induced wave damping rate. The model performed well in tests based on laboratory data. Numerical tests show that damping of high frequency waves ... |
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| Design of Gages for Direct Skin Friction Measurements in Complex Turbulent Flows with Shock Impingement Compensation |
07 JUN 2007 |
133 pages |
| Authors:
August J. Rolling; VIRGINIA POLYTECHNIC INST AND STATE UNIV BLACKSBURG DEPT OF AEROSPACE AND OCEAN ENGINEERING
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| This research produced a new class of skin friction gages that measures wall shear even in shock environments. One test specimen separately measured wall shear and variable-pressure induced moment. Through the investigation of available computational modeling methods, techniques for accurately predicting gage physical responses were developed. The culmination of these model combinations was a design optimization procedure. This procedure was applied to three disparate test conditions: 1) short duration, high-enthalpy ... |
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| Calculating Required Substructure Damping to Meet Prescribed System Damping Levels |
JUN 2007 |
93 pages |
| Authors:
Wendel D. Penetrante; NAVAL POSTGRADUATE SCHOOL MONTEREY CA DEPT OF MECHANICAL AND ASTRONAUTICAL ENGINEERING
|
| Structural synthesis is a method of calculating the transient dynamic response of an assemblage of substructures without explicitly assembling and solving a combined system model. While significant computational advantages are provided by this method, the modal parameters of the combined system are not explicitly calculated. Hence, a method is needed to allow the a priori determination of the substructure damping levels such that the synthesized system damping is within user-prescribed ... |
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| Symposium Q: Magnetic Thin Films, Heterostructures, and Device Materials |
22 MAY 2007 |
25 pages |
| Authors:
William Bailey; MATERIALS RESEARCH SOCIETY WARRENDALE PA
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| In Symposium Q on Magnetic Thin Films, Heterostructures, and Device Materials, spin-dependent tunneling junctions were presented, with a particular focus on Fe/MgO/Fe junctions. Tunneling magnetoresistance values in this system have recently attained up to 350% at room temperature, several times higher than those seen in any other materials system. High magnetoresistance values were presented experimentally, treated through ab initio models, and correlated with MgO barrier structure by in situ STM ... |
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| Analytical Assessment of the Blast Resistance of Precast, Prestressed Concrete Components (PREPRINT) |
APR 2007 |
28 pages |
| Authors:
Nicholas Cramsey; Clay Natio; LEHIGH UNIV BETHLEHEM PA
|
| Four blast tests were performed on 30-ft (9.1 m) tall precast, prestressed concrete wall panels. Two conventional sandwich panels and a control panel were examined and shown to perform adequately under the blast demands. An approximate dynamic analysis technique for finding the blast resistance of the wall panels was developed and validated using the experimental results. For the wall panels in this study, it was found that an undamped analytical ... |
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| Studies and Experiments in Structural Dynamics and Control |
30 DEC 2006 |
32 pages |
| Authors:
Khanh D. Pham; AIR FORCE RESEARCH LAB KIRTLAND AFB NM SPACE VEHICLES DIRECTORATE
|
| The objective of this task is to develop enabling structural technologies for future Air Force systems. Four areas of research are currently under investigation: thermal/mechanical to electrical energy conversion utilizing piezoelectrics that explore power augmentation schemes to maximize power available for DoD satellites and the use of piezoelectric power generation produced by thermal expansion proves 5% satellite power augmentations possible; lightweight, low frequency acoustic barrier using particle embedded foil that ... |
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| Boussinesq Modeling of Alongshore Swash Zone Currents |
DEC 2006 |
20 pages |
| Authors:
Q. J. Chen; LOUISIANA STATE UNIV BATON ROUGE DEPT OF CIVIL AND ENVIRONMENTAL ENGINEERING
|
| The report documents the theoretical and numerical investigations on wave propagation over porous beds as well as on alongshore surf and swash currents. The study has been carried out in the framework of wave-resolving Boussinesq-type models. First, we have derived a new set of Boussinesq-type equations for nonlinear waves and surf-zone currents over a permeable beach (Chen 2006). A Stokes-type analysis and rational expansions were carried out to examine the ... |
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| Piezoelectric Tailoring with Enhanced Electromechanical Coupling for Concurrent Vibration Control of Mistuned Periodic Structures |
DEC 2006 |
33 pages |
| Authors:
Kon-Well Wang; PENNSYLVANIA STATE UNIV UNIVERSITY PARK
|
| The objective of this research is to advance the state of the art of vibration control of mistuned periodic structures utilizing the electromechanical coupling and damping characteristics of piezoelectric networking. in this investigation, an active coupling enhancement approach through negative capacitance has been developed to increase the piezolectric electromechanical coupling. Experiments were carried out to validate the delocalization concept of the piezoelectric network. it was verified that the vibration localization ... |
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| Advanced Materials and Multifunctional Structures for Aerospace Vehicles |
01 OCT 2006 |
29 pages |
| Authors:
P. C. Patnaik; W. R. Chen; NATIONAL RESEARCH COUNCIL OF CANADA OTTAWA (ONTARIO) INST FOR AEROSPACE RESEARCH
|
| This paper presents a critical review of the work on Advanced Materials for Multi-Functional Structures in Aerospace Vehicles. The advanced synthesis, processing and the characterization techniques that facilitate the design of multifunctional aerospace materials leading to their reliable and high performance in extreme environments will be reviewed. The focus areas of this paper will be materials for sensing, actuation and damping, damage tolerant and adaptive structures, anti-icing and multifunctional coatings. ... |
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| Dynamic Testing of In-Situ Composite Floors and Evaluation of Vibration Serviceability Using the Finite Element Method |
21 AUG 2006 |
452 pages |
| Authors:
Anthony R. Barrett; VIRGINIA POLYTECHNIC INST AND STATE UNIV BLACKSBURG
|
| The presented research examined three areas: best practices in high quality dynamic testing of in-situ floor systems, extensive dynamic testing of three bare (non-fit out) in-situ multi-bay steel composite floors to estimate their dynamic parameters/response and to identify trends in dynamic behavior, and development of a set of fundamental finite element (FE) modeling techniques to adequately represent the dynamic response of steel composite floors for the purpose of evaluating vibration ... |
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| Investigation of Passive Control Devices for Potential Application to a Launch Vehicle Structure to Reduce the Interior Noise Levels During Launch |
25 MAY 2006 |
87 pages |
| Authors:
Carl Q. Howard; Colin Hansen; ADELAIDE UNIV (AUSTRALIA) DEPT OF MECHANICAL ENGINEERING
|
| This series of reports document a multi-year research project into the reduction of acoustic vibrations in space launch vehicles using passive mass damping devices. The purpose of this report is to collate all the knowledge that has been gained during all four stages, into a single concise document. |
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| Development of Composite Materials with High Passive Damping Properties |
15 MAY 2006 |
129 pages |
| Authors:
Malcolm J. Crocker; AUBURN UNIV AL DEPT OF MECHANICAL ENGINEERING
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| In applications where the use of lightweight structures is important, the introduction of a viscoelastic core layer, which has high inherent damping, between two face sheets, can produce a sandwich structure with high damping. Composite sandwich structures have several advantages, such as their high strength-to-weight ratio, excellent thermal insulation, and good performance as water and vapor barriers. So in recent years, such structures have become used increasingly in transportation vehicles. ... |
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| Evaluation of Factors Contributing to Damping of Coated and Uncoated Titanium Plates |
23 MAR 2006 |
260 pages |
| Authors:
Dustin W. Lee; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH DEPT OF AERONAUTICS AND ASTRONAUTICS
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| High Cycle Fatigue (HCF) is the leading cause of component failure in gas turbine engines today, which poses great risk to aircraft, engines, and their crews. Mitigation of HCF effects has become a priority topic, and the damping benefits of hard coatings are being reevaluated for this purpose. Research was conducted to further understanding of damping measurements on these coatings. This study continues work to characterize the damping effects of ... |
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| Structural Piezoelectric Single Crystal Array Networks (Structural P-SCAN) |
MAR 2006 |
7 pages |
| Authors:
S. L. Kampe; VIRGINIA POLYTECHNIC INST AND STATE UNIV BLACKSBURG DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| Experimental verification of enhanced passive mechanical damping as derived from ferroelectric-embedded particulates within a metal matrix composite has been demonstrated. Specifically, experimental results indicate relatively high damping is exhibited by composites containing a discontinuous dispersion of ferroelectric (tetragonal) BaTiO(sub 3) particulate; damping capability is reduced as temperature increases and a transformation to a cubic form occurs. Experiments performed at the Los Alamos Neutron Science Center (LANSCe) indicate that the mechanism ... |
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| Inducing Apoptosis in Bcr/Abl-Expressing Cells |
MAR 2006 |
6 pages |
| Authors:
Sally Kornbluth; DUKE UNIV DURHAM NC
|
| With the emergence of CMLs that are resistant to Bcr-Abl tyrosine kinase inhibitors it becomes imperative that we identify other effective agents to eliminate these cells. In recent years it has become evident that most successful chemotherapeutics work by inducing apoptosis. Unfortunately high levels of Bcr-Abl can preclude the successful use of many agents by dampening the apoptotic response. In this proposal we developed a strategy that relies on indeed ... |
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| Biomimetic Design of an Under-Actuated Leg Exoskeleton for Load-Carrying Augmentation |
01-Feb-2006 |
97 pages |
| Authors:
Conor J Walsh; MASSACHUSETTS INST OF TECH CAMBRIDGE MEDIA LAB
|
| Metabolic studies have shown that there is a metabolic cost associated with carrying a load. Previous work on exoskeleton design has not considered the passive dynamics of walking and has focused on fully actuated systems that are inefficient and heavy. In this thesis, an underactuated exoskeleton is presented that runs parallel to the human leg. The exoskeleton component design is based on the kinematics and kinetics of human walking. The ... |
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| Alleviation of Buffet-Induced Vibration Using Piezoelectric Actuators |
FEB 2006 |
118 pages |
| Authors:
Shawn D. Morgenstern; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING AND MANAGEMENT
|
| Buffet-induced vibration has been problematic for aircraft structures for many years. The F-16 ventral fin, while prone to these effects, lends itself well to the evaluation of modern active structural and flow control technologies. The objective of this research was to determine the most critical natural modes of vibration for the F-16 ventral fin and design piezoelectric actuators capable of reducing buffet-induced ventral fin vibration. A finite element model (FEM) ... |
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| High-Voltage Power Switching for a Conducting Tether |
2006 |
11 pages |
| Authors:
Sriram Harkare; Roger Dougal; Joseph A. Carroll; Shengyi Liu; SOUTH CAROLINA UNIV COLUMBIA
|
| The ElectroDynamic Delivery Express (EDDE) is an autonomous space vehicle that can maneuver throughout low earth orbit without using fuel. EDDE uses solar power to drive multi-ampere currents through a kilometers-long aluminum conductor, creating a force normal to both the conductor and the local magnetic field that drives the space vehicle. The tether spins at about 8 times/orbit. This stabilizes its dynamics and also allows a wider range of electrodynamic ... |
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| Highly Damping Hard Coatings for Protection of Titanium Blades |
01 OCT 2005 |
17 pages |
| Authors:
Boris A. Movchan; Anatolii I. Ustinov; UKRAINIAN ACADEMY OF SCIENCES KIEV E O PATON INST OF ELECTRICAL WELDING
|
| Sn-Cr-MgO system is used as an example to show the basic capability to produce by EBPVD protective metal-ceramic coatings with a high adhesion strength, high values of hardness and damping capacity on the surface of titanium alloys at substrate temperatures not higher than 400 degrees C. After deposition of such coatings on the surface of titanium samples their endurance limit is preserved. It allows these coatings to be regarded as ... |
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| Adaptive Damping and Positioning Using Intelligent Composite Active Structures (ADPICAS) |
OCT 2005 |
172 pages |
| Authors:
Mehrdad G. Nejhad; HAWAII UNIV HONOLULU DEPT OF MECHANICAL ENGINEERING
|
| The main objectives of this research are to design, analyze, fabricate, and test intelligent composite active structures and systems to provide simultaneous precision position and vibration suppression control capabilities for military and space structures to enhance their structural performance and reduce their fuel consumption. These simultaneous vibration suppression and precision positioning capabilities, for mission performance enhancement, are achieved by using well-integrated sensors/actuators/controllers where the host structures will be constructed mainly ... |
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| Quantum Lattice-Gas Model for Computational Fluid Dynamics |
28 SEP 2005 |
19 pages |
| Authors:
Jeffrey Yepez; AIR FORCE RESEARCH LAB HANSCOM AFB MA
|
| Quantum-computing ideas are applied to the practical and ubiquitous problem of fluid dynamics simulation. Hence, this paper addresses two separate areas of physics: quantum mechanics and fluid dynamics (or specifically, the computational simulation of fluid dynamics). The quantum algorithm is called a quantum lattice gas. An analytical treatment of the microscopic quantum lattice-gas system is carried out to predict its behavior at the mesoscopic scale. At the mesoscopic scale, a ... |
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| Analysis of Aerosol Aging in the Rotating Drum Chamber |
AUG 2005 |
76 pages |
| Authors:
Janon F. Embury; Tiffany A. Sutton; EDGEWOOD CHEMICAL BIOLOGICAL CENTER ABERDEEN PROVING GROUND MD
|
| Two of the most recent theories describing aero-sol mechanics in the rotating drum chamber were compared with experimental measurements. Both theories predicted nearly the same results but did not match out measurements. Possible causes for the discrepancies were investigated, and it was found that convective diffusion accounts for the difference with the stirred settling model predicting measurements reasonably in the limit where rotation rate becomes zero. Once rotation begins, transport ... |
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| Nanoscale Characterization of Failure Processes in Polymer Nanocomposites |
AUG 2005 |
52 pages |
| Authors:
Raman P. Singh; STATE UNIV OF NEW YORK AT STONY BROOK
|
| This project was focused on two areas of investigation: application of novel displacement modulation techniques for nanoindentation based viscoelastic characterization; and the use of acoustic emission characterize nanoindentation induced fracture in brittle materials and advanced. A new displacement modulation technique has been developed and employed for determining the storage and loss moduli of viscoelastic polymers, as a function of frequency. This new technique represents a highly superior approach in comparison ... |
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| Fairing Noise Control Using Tube-Shaped Resonators |
AUG 2005 |
8 pages |
| Authors:
Steven A. Lane; Robert E. Richard; Scott J. Kennedy; AIR FORCE RESEARCH LAB KIRTLAND AFB NM
|
| The potential for noise mitigation in composite Chamber Core fairings is investigated by using the walls of the fairing structure itself as acoustic resonators. This is the first documented application of long cylindrical tube-shaped resonators for fairing noise control. The theory and modeling of tube-shaped resonators for controlling fairing acoustic resonances is presented. The potential for noise mitigation in composite Chamber Core fairing using the walls of the fairing structure ... |
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| Investigating the Effect of Displacement Rate on Deformation and Failure Mechanism in Bonded Elastomers |
JUL 2005 |
7 pages |
| Authors:
Fu-Pen Chiang; STATE UNIV OF NEW YORK AT STONY BROOK DEPT OF MECHANICAL ENGINEERING
|
| Bonded sandwich laminates are being used widely in various industries. They have been successfully used in aircraft and space structures, pipes, chemical tanks, ship hulls, and in other structural applications in which a high strength-to-weight ratio is a desirable feature. Joining structural components with adhesives provides a number of advantages. Bonding does not require rivet holes, which are stress raisers and may cause premature failure either under static or fatigue ... |
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| Investigations of Parametric Excitation in Physical Systems |
JUN 2005 |
79 pages |
| Authors:
Michael T. Janssen; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| Parametric excitation can occur when the value of a parameter of an oscillator is modulated at twice the natural frequency of the oscillator. The response grows exponentially and is only limited by a nonlinearity of the system, so large response amplitudes typically occur. However, there is no response unless the parametric drive amplitude is above a threshold value that is dictated by the damping. We investigate parametric excitation in three ... |
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| Analysis and Support Initiative for Structural Technology (ASIST). Delivery Order 0018: Active Vibration Control of Buffet-Induced Vibrations in the Vertical Tail of F/A-18 |
JUN 2005 |
53 pages |
| Authors:
Saythia Hanagud; Patrick Roberts; GEORGIA INST OF TECH ATLANTA SCHOOL OF AEROSPACE ENGINEERING
|
| Active controllers are designed and validated to control buffet-induced vibrations in the vertical tails of F/A-18 aircraft during high angle of attack (AOA) maneuvers. First, a procedure is developed to design the offset piezoceramic actuator assemblies, the number of actuators needed, the location of actuators, and the operational power to achieve the needed control authority. The design is limited by the specification of the worst buffet scenario that has been ... |
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| Synthetic Multi-Functional Materials for Structural + Ballistic and Blast Protection |
MAR 2005 |
128 pages |
| Authors:
Kenneth S. Vecchio; CALIFORNIA UNIV REGENTS SAN DIEGO LA JOLLA CA
|
| This program was part of the DARPA program on Synthetic Multi- Functional Materials focused on structural plus ballistic and blast protection. During the first period of this program we have been focusing on developing both intrinsic and embedded functionality into a class of metal-intermetallic laminate (MIL) composites based on the Ti-Al system. These layered composites were initially developed as part of an Army MURI program at the University of CA, ... |
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| Station Calibration and Regionalization in China and Surrounding Areas |
JAN 2005 |
72 pages |
| Authors:
Thomas Hearn; James Ni; NEW MEXICO STATE UNIV LAS CRUCES DEPT OF PHYSICS
|
| NMSU seismologists, in conjunction with seismologists from the Institute of Geophysics of the China Seismological Bureau (IG/CSB), have collected seismic data to calibrate International Monitoring System stations in China and document propagation characteristics of regional phases in China. Much of the work is focused on the Annual Bulletin of Chinese Earthquakes. We obtained copies of these bulletins for 1983-1995. A tomographic image of Pn velocity beneath China was made and ... |
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| Excitation of the Magnetospheric Cavity by Space-Based ELF/VLF Transmitters |
06 DEC 2004 |
11 pages |
| Authors:
Timothy F. Bell; Umran Inan; P. Kulkarni; STANFORD UNIV CA
|
| During the period of performance Stanford University: 1. Developed an analytical model describing the distribution of current along a dipole antenna radiating ELF/VLF waves in the magnetospheric cavity. It was found that the antenna orientation had an important effect upon the radiation characteristics of the dipole antenna. 2. Mapped out the power distribution of ELF/VLF waves radiated by space-based transmitters throughout the magnetospheric cavity for a range of wave normal ... |
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| Aeroelasticity, Aerothermoelasticity and Aeroelastic Scaling of Hypersonic Vehicles |
DEC 2004 |
21 pages |
| Authors:
Peretz P. Freidmann; Kenneth G. Powell; MICHIGAN UNIV ANN ARBOR DEPT OF AEROSPACE ENGINEERING
|
| This final report describes the work during the period of the grant. Three separate hypersonic aeroelastic stability problems were considered: (a) a typical cross section having a double wedge airfoil, (b) the stability of a low aspect ratio wing, also with a double wedge airfoil, and (c) the behavior of a complete generic hypersonic vehicle. For problems (a) the unsteady airloads were computed using third order piston theory, as well ... |
|
| Advanced Technologies for Chemical Weapons Detection and Analysis |
17 NOV 2004 |
27 pages |
| Authors:
Alex Robinson; Doug Adkins; Patrick Lewis; David Wheeler; Ron Manginell; Shawn Dirk; Steve Howell; R. J. Simonson; SANDIA NATIONAL LABS ALBUQUERQUE NM
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| Uncertainties and Relaxation of Boundary Conditions of Aeroelastic Panels |
08 NOV 2004 |
34 pages |
| Authors:
Raouf A. Ibrahim; WAYNE STATE UNIV DETROIT MI DEPT OF MECHANICAL ENGINEERING SCIENCES
|
| The influence of boundary condition relaxation on two-dimensional panel flutter is studied in the presence of in-plane loading. The boundary value problem of the panel involves time-dependent boundary conditions that are converted into autonomous form using a special coordinate transformation. Galerkin's method is used to discretize the panel partial differential equation into six nonlinear ordinary differential equations representing the first six modes. The influence of boundary condition relaxation on the ... |
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| A Complete Rotor Wake Model in State Space |
01 SEP 2004 |
25 pages |
| Authors:
David A. Peters; WASHINGTON UNIV ST LOUIS MO
|
| This research deals with the development of a finite-state inflow theory that will be able to predict all three components of flow both on and off of the rotor disk. The theory will be of a velocity potential expanded in hierarchical degrees of freedom. |
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| Appendage and Viscous Forces for Ship Motions in Waves |
SEP 2004 |
|
| Authors:
Kevin A. McTaggart; DEFENCE RESEARCH AND DEVELOPMENT ATLANTIC DARTMOUTH (CANADA)
|
| This report describes the prediction of appendage and viscous forces in Defence Research and Development Canada (DRDC) Atlantic's ShipMo3D library for ship motions in waves. Previously, the ShipMo3D library considered only hull forces due to potential flow. Inclusion of appendage and viscous forces is essential for accurate prediction of ship sway, roll, and yaw motions. Appendage forces are caused by added mass, lift, and viscous effects. Hull viscous forces are ... |
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| Acoustics in New Materials |
15 AUG 2004 |
11 pages |
| Authors:
Julian D. Maynard; PENNSYLVANIA STATE UNIV UNIVERSITY PARK DEPT OF PHYSICS
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| The technical objectives of this research are to determine the physical properties of new materials with emphasis on thin films deposited on substrates. For the most part, experiments will involve the measurement of elastic constants and damping. As derivatives of the free energy with respect to atomic positions, elastic constants are a sensitive probe of the environment in which all physical processes take place within a solid; they are a ... |
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Reports by Keyword(s)
DAMPING
