| Experimental and Numerical Analyses of Dynamic Deformation and Failure in Marine Structures Subjected to Underwater Impulsive Loads |
Aug 2012 |
166 pages |
| Authors:
Siddharth Avachat; GEORGIA INST OF TECH ATLANTA
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 | Marine structures are designed to operate in hostile environments consisting of corrosive sea-water, hot and cold temperature extremes, transient dynamic loads like hull-slamming and complex three-dimensional hydrostatic loads. Additionally, naval structures are required to withstand weapons impacts and blast loads resulting from surface and underwater explosions. Recent assessments of marine structures have demonstrated that sandwich structures and composite materials can provide high strength-to-weight ratios and good blast mitigation. This thesis ... |
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| The Compressive Failure of Aluminum Nitride Considered as a Model Advanced Ceramic |
Jun 2012 |
27 pages |
| Authors:
Guangli Hu; K T Ramesh; Buyang Cao; J W McCauley; JOHNS HOPKINS UNIV BALTIMORE MD DEPT OF MECHANICAL ENGINEERING
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| Uniaxial quasi-static compression, uniaxial dynamic compression and confined dynamic compression experiments were performed to characterize the failure of Aluminum Nitride (AlN) using a servo hydraulic machine and a modified Kolsky bar set-up respectively. High-speed digital cameras are used to visualize the failure processes. A summary of the available experimental results, including that in the literature, shows that the compressive strength of the AlN is sensitive to strain rate in the ... |
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| Evaluation of the Thorax of Manduca sexta for Flapping Wing Micro Air Vehicle Applications |
Mar 2012 |
182 pages |
| Authors:
Alex C Hollenbeck; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH GRADUATE SCHOOL OF ENGINEERING AND MANAGEMENT
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| The tobacco hornworm hawkmoth (Manduca sexta) provides an excellent model from which to garner knowledge pertaining to the development of a Flapping Wing Micro Air Vehicle (FWMAV). Insect-sized FWMAVs will be used by the future warfighter for reconnaissance, nuclear/chemical/biological hazard sensing, and targeting. One of the major challenges facing FWMAV developers is the energetically demanding nature of low Reynolds flapping flight. Investigating the Manduca sexta thorax/wing flapping mechanism as a ... |
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| Air Vehicle Integration and Technology Research (AVIATR). Delivery Order 0013: Nonlinear, Low-Order/Reduced-Order Modeling Applications and Demonstration |
Dec 2011 |
269 pages |
| Authors:
Salvatore L Liguore; Dale M Pitt; Michael J Thomas; Nicholas Gurtowski; BOEING CO ST LOUIS MO
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| Dynamic response analysis tools used by the aerospace industry rely heavily on linear modal frequency response finite element methods. These linear methods are straight forward to use even in the analysis of a complex structural component that require a large number of degrees-of-freedom to model. However, this approach is not suitable for predicting the response of highly loaded thermal/acoustic aircraft structures that may respond in a nonlinear geometric manner. This ... |
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| Expeditionary Basecamp Passive Protection |
03 Nov 2011 |
12 pages |
| Authors:
Nicholas Tino; ARMY NATICK SOLDIER RESEARCH DEVELOPMENT AND ENGINEERING CENTER MA SHELTER TECHNOLOGY ENGINEERING AND FABRICATION DIRECTORATE
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| Warfighters in highly mobile forward units have no inherent ballistic protection in shelters and no time/manpower to install traditional ballistic protection (i.e., sandbags, concrete barriers). Multiple requests for ballistic protection for shelters have been received from the theater. Creating a low-cost ballistic solution requires advancing current material technology, systems integration, and manufacturing processes. The solution is the Modular Ballistic Protection System (MBPS). The MBPS is rapidly deployable ballistic protection; it ... |
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| Dynamic Uniaxial Tensile Loading of Vector Polymers |
Nov 2011 |
66 pages |
| Authors:
Johnathan Niemczura; Joe Lenhart; Randy Mrozek; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE
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| During this analysis, we investigated tensile wave propagation using a strip stretcher with the goal of finding constitutive properties for soft materials of interest to the U.S. Army Research Laboratory. We found the power-law model to be adequate for matching small strain response prior to reflection for the polymers not undergoing localization. After examining the Swanson model, we found that it matched the power-law response |
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| Investigation of an Explicitly Modeled Solid Ocean Floor on a Shallow Water UNDEX Event |
Sep 2011 |
134 pages |
| Authors:
Adam P Walters; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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| Current practices for modeling the ocean floor in underwater explosion simulations call for application of an inviscid fluid with soil properties. A method for modeling the ocean floor as a Lagrangian solid, vice an Eulerian fluid, was developed in order to determine its effects on underwater explosions in shallow water using the DYSMAS solver. The Lagrangian solid bottom model utilized transmitting boundary segments, exterior nodal forces acting as constraints, and ... |
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| Microstructural Modeling and Representation of Simultaneous Failure Modes in Crystalline Aggregates Subjected to Dynamic Loading Conditions |
09 JAN 2011 |
33 pages |
| Authors:
M. A. Zikry; NORTH CAROLINA STATE UNIV AT RALEIGH DEPT OF MECHANICAL AND AEROSPACE ENGINEERING
|
| This provides an integrated framework to simultaneously handle different interrelated physical mechanisms, such as a myriad of representative dislocation-density interactions with high and low angle GB interfaces, the growth and coalescence of a population of voids, and how these interactions can lead to either intergranular or transgranular failure. The formation of pile-ups at GB interfaces, as a function of dislocation-density partial and total blockage and absorption at GB interfaces, will ... |
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| Characterization and Performance Optimization of a Cementitious Composite for Quasi-Static and Dynamic Loads |
2011 |
7 pages |
| Authors:
W. F. Heard; P. K. Basu; T. Slawson; B. Williams; N. A. Nordendale; ARMY CORPS OF ENGINEERS VICKSBURG MS ENGINEER RESEARCH AND DEVELOPMENT CENTER
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| The U.S. Army Engineer Research and Development Center conducted multi-scale material research directed towards enhancing the response of a rapid-set, high-strength geopolymer cement under quasi-static and dynamic loads. Four unique tensile experiments were conducted to characterize and optimize material response of the fiber, matrix, and interface. Single-fiber direct tension and single-fiber pull-out experiments were conducted with quasi-static and dynamic loads. Flexure from third-point loading and direct uniaxial tension of the ... |
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| A Brief Review of Elasticity and Viscoelasticity |
27 May 2010 |
50 pages |
| Authors:
H T Banks; Shuhua Hu; Zackary R Kenz; NORTH CAROLINA STATE UNIV AT RALEIGH CENTER FOR RESEARCH IN SCIENTIFIC COMPUTATION
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| There are a number of interesting applications where modeling elastic and/or viscoelastic materials is fundamental, including uses in civil engineering, the food industry land mine detection and ultrasonic imaging. Here we provide an overview of the subject for both elastic and viscoelastic materials in order to understand the behavior of these materials. We begin with a brief introduction of some basic terminology and relationships in continuum mechanics, and a review ... |
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| High Strain-Rate Testing of Mechanical Couplers |
Sep-2009 |
74 pages |
| Authors:
Stephen P Rowell; Clifford E Grey; Stanley C Woodson; Kevin P Hager; ENGINEER RESEARCH AND DEVELOPMENT CENTER VICKSBURG MS GEOTECHNICAL AND STRUCTURES LAB
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| Criteria for designing structures to resist the effects of accidental explosions are defined by Army Technical Manual (TM) 5-1300. These structures are built using steel-reinforced concrete. The current practice of splicing the flexural reinforcing steel is to lap the steel, which often creates a congestion of the steel in floors, walls, and adjoining corners. In 1971, a limited number of types of splices were tested at the U.S. Army Engineer ... |
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| Analysis and Testing of a Tapered End Connection for Laser Welded Steel Sandwich Panels |
15-Aug-2009 |
181 pages |
| Authors:
Vincent Caccese; Serdar Yourimaz; Lawrence Thompson; Senthil S Vei; MAINE UNIV ORONO OFFICE OF RESEARCH AND SPONSORED PROGRAMS
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| 14. ABSTRACT This report summarize the analysis and cyclic testing of a laser welded steel sandwich panel end connection. Also included are monotonic tests of stake welded lap shear coupons with welds oriented both longitudinally and transverse. Steel sandwich panels offer substantial resistance to static and dynamic loads due to their high stiffness and substantial energy absorbing capacity. Panels of this kind are interest of potential use in ships and ... |
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| Mechanical Response and Shear Initiation of Double-Base Propellants |
Aug-2009 |
16 pages |
| Authors:
Stephan R Bilyk; Michael J Scheidler; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
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| The intense shearing that occurs in propellants during impulsive loading can lead to initiation. In an effort to determine useful shear initiation criteria, the U.S. Army Research Laboratory has developed a dynamic shear punch test using a modified split- Hopkinson bar. Varying the striker bar's velocity and length controls the shear rate and duration. Shear velocities approaching 100 m/s and durations as long as 0.2 ms are possible. Experimental results ... |
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| A Study of the Engraving of the M855 5.56-mm Projectile |
Mar-2009 |
30 pages |
| Authors:
Joseph South; Aristedes Yiournas; Jordan Wagner; JOHN BROWN; Robert Kaste; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE
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| The interaction between a small-caliber projectile and its weapon system cannot be readily measured during the launch event. The forces and resulting deformations on the projectile due to engraving are small and localized compared to the ballistic pressure. Consequently, the interaction is inferred from the condition of the projectile after it has exited the barrel. A direct method of examining the engraving force and the resulting projectile deformation is through ... |
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| Development of a Multi-Scale Methodology for Prediction of the Microscopic Anisotropic Stress-Strain Response of Textured Metals under Dynamic Loading |
21-Jan-2009 |
69 pages |
| Authors:
Oana Cazacu; FLORIDA UNIV SHALIMAR DEPT OF MECHANICAL AND AEROSPACE ENGINEERING
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| This report documents a comprehensive experimental and theoretical investigation of the deformation behavior of high-purity, polycrystalline alpha-titanium. A series of monotonic uniaxial compression and tension tests were carried out at room temperature under quasi-static conditions to quantify the plastic anisotropy and the tension-compression asymmetry of this material. The evolution of microstructure and texture during deformation was studied using optical image microscopy (OIM) and neutron-diffraction techniques to elucidate the role of ... |
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| Structural Analyses & Experimental Activities Supporting the Design of a Lightweight Rigid-Wall Mobile Shelter |
Dec-2008 |
10 pages |
| Authors:
Melvin Jee; Paul V Cavallaro; NAVAL UNDERSEA WARFARE CENTER DIV NEWPORT RI
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| Lightweight rigid-wall shelters used in mobile military operations are constructed of sandwich panels comprised of thin face sheets and thick, ultra light core materials to minimize weight and maximize structural integrity. However, such lightweight construction comes at a cost, often impacting the design and manufacturing of critical joints connecting the sandwich panels in a box-like assembly. Furthermore, joint stiffnesses are often difficult to characterize and their finite values significantly influence ... |
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| Dynamic System Response of Truss Panels under High Dynamic Loading through Experimental & Computation Evaluation |
Dec-2008 |
10 pages |
| Authors:
Rahul Gupta; Tyrone L Jones; Matthew Burkins; Haydn Wadley; Yellapu Murty; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
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| The ability of computer simulations to accurately resolve dynamic responses of systems has significantly improved over the last decade. Simulations can now be a trusted source of parametric evaluation of complex systems. DARPA funded a program to investigate the dynamic performance of truss panel systems. Two configurations were computer simulated and their material responses were characterized. This manuscript documents the validity of computer simulation to correlate experimental system failure limits ... |
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| Biomimetic Micro Air Vehicle Testing Development and Small Scale Flapping-Wing Analysis |
MAR 2008 |
114 pages |
| Authors:
Craig E. Svanberg; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH DEPT OF AERONAUTICS AND ASTRONAUTICS
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| The purpose of this research was to develop testing methods capable of analyzing the performance of a miniature flapping-wing mechanism that can later be adapted for the development a biomimetic flapping-wing micro air vehicle (MAV). Three small scale flapping mechanisms capable of single plane flapping, flapping with active pitch control, and flapping/pitch with out-of-plane movement were designed using SolidWorks. The flapping-only model was fabricated on an Objet 3-dimensional printer and ... |
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| Start-Up Response of Fluid Film Lubricated Cryogenic Turbopumps (Preprint) |
13 JUN 2007 |
38 pages |
| Authors:
Luis San Andres; TEXAS A AND M UNIV COLLEGE STATION DEPT OF MECHANICAL ENGINEERING
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| Reusable primary power cryogenic turbopumps (TPs) implement externally pressurized fluid film bearings to support the expected large thrust and lateral radial loads. Compact - low count part TPs operate super critically at exceedingly high shaft speeds (180 krpm) and with large pressure differentials. Hybrid journal bearings (HJBs) enable smaller and lighter turbopumps through no bearing DN life limitation. The growth of an "all-fluid-film- bearing" technology for reusable and less costly ... |
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| Parametric Dynamic Load Prediction of a Narrow Gauge Rocket Sled |
DEC 2006 |
261 pages |
| Authors:
John S. Furlow; NEW MEXICO STATE UNIV LAS CRUCES
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| Dynamic load prediction of rocket sleds has been of interest to sled designers and analysts since the inception of the Holloman High Speed Test Track, (HHSTT). Dynamic loading along with thrust and aerodynamic loading is a primary contributor to sled design load cases. Dynamic loading comes directly from the rocket sled traversing the gap between the slipper and rail and the resulting sliding impacts. The current study investigates the prediction ... |
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| Introduction to Pump Rotordynamics |
01 NOV 2006 |
|
| Authors:
Luis S. Andres; TEXAS A AND M UNIV COLLEGE STATION TURBOMACHINERY LABS
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 | The lecture introduces the basic problems in the rotordynamics of turbomachinery, excessive vibration and instability. The acceptable performance of a turbomachine depends on the adequate design and operation of the bearing and seal elements supporting a rotor. Descriptions of the basic principles of lubrication follow with details on the operation of hydrodynamic and hydrostatic lubricated bearings and seals. The differences among these elements are highlighted with a brief account on ... |
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| Fundamental Investigation of High-Velocity Impact of Ductile Projectiles on Confined Ceramic Targets |
NOV 2006 |
9 pages |
| Authors:
B. Leavy; C. Krauthauser; J. Houskamp; J. LaSalvia; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
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| To aid the Army's transformation into a more mobile, rapidly deployable, and highly survivable force, researchers at the Army Research Laboratory (ARL) have undertaken a program aimed at supporting the development of lighter weight ceramic armors with greater protection capabilities. One goal of this program is to improve the capabilities of computational tools for the design and analysis of ceramic armors, which offer greatly enhanced protection capabilities at reduced weights. ... |
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| Natural Frequencies and Mode Shapes of a Nonlinear, Uniform Cantilevered Beam |
SEP 2006 |
207 pages |
| Authors:
Daniel J. Marquez-Chisolm; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH DEPT OF AERONAUTICS AND ASTRONAUTICS
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| A series of experiments in 1975, referred to as the Princeton Beam Experiments, were performed to measure natural frequencies and create a nonlinear elastic deformation model to improve helicopter main beam designs. These experiments used a homogeneous 7075 aluminum beam and have been referenced as a baseline for the past thirty years to validate computer models and theories in an effort to build beams capable of withstanding aero-elastic, static, and ... |
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| Scaling of Energy Absorption in Composites to Enhance Survivability |
AUG 2006 |
24 pages |
| Authors:
Zdenek P. Bazant; NORTHWESTERN UNIV EVANSTON IL
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| The objective of this paper is to study the size effect on the nominal strength of imperfect sandwich structures for buckling driven delamination, to quantify this size effect, and to determine its intensity. A secondary objective is to assess the size effect on the postpeak energy absorption, important for judging survival under blast or dynamic impact. Buckling driven delamination is difficult to control in experiments. Thus, the present study relies ... |
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| Multifunctional Carbon Nanotube Damping Films |
06 JUN 2006 |
49 pages |
| Authors:
Nikhil Koratkar; Prabhat Hajela; Pulickel Ajayan; RENSSELAER POLYTECHNIC INST TROY NY
|
| The objective of this project was to quantify the energy dissipation that occurs when the interfacial slip of nanoscale fillers is activated in a host matrix material. We consider both polymer (such as polycarbonate, PEO, PEG) and epoxy matrices. The nanoscale fillers considered are carbon nanotubes (both singlewalled as well as multi-walled) as well as fullerenes. The nano-composites are fabricated by using a solution mixing technique with tetra-hydro-furan as the ... |
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| An Analysis of Nonlinear Elastic Deformations for a Homogeneous Beam at Varying Tip Loads and Pitch Angles |
JUN 2006 |
106 pages |
| Authors:
Robert J. McGraw; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH DEPT OF AERONAUTICS AND ASTRONAUTICS
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| The Princeton beam experiments of 1975 were performed in hopes of producing viable data for beam nonlinear elastic deformation models in hopes of improving helicopter main beam designs. The recorded data, specifically for homogeneous beams of 7075 aluminum, have been referenced as a baseline for the past thirty years to validate numerous computer models and theories in an effort to build beams capable of withstanding aeroelastic, static, and dynamic loading. ... |
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| A 37-mm Ceramic Gun Nozzle Stress Analysis |
MAY 2006 |
28 pages |
| Authors:
Xiaogang Huang; James Garner; Paul Conroy; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
|
| A series of shooting tests was conducted on a 37-mm gun fixture with ceramic nozzles. The primary concern for the design and test of the ceramic nozzle is the combination of the thermal stress and dynamic ballistic stress during the launch. On the basis of previous thermal analysis, a transient sequentially coupled finite-element model is performed to investigate the thermal stresses due to the large temperature gradient and coefficient mismatch ... |
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| Characterization and Model Assessment for Impact Damage Evolution in Functionally Graded Composites Using a Novel Nanosecond Deformation Measurement System |
30 APR 2006 |
48 pages |
| Authors:
Stephen R. McNeill; Michael A. Sutton; Hugh A. Bruck; SOUTH CAROLINA UNIV COLUMBIA OFFICE OF SPONSORED PROGRAMS
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| The principal goal of this research is to experimentally measure the three-dimensional transient deformation processes that occur in armor systems undergoing a range of dynamic loading conditions. The development of a 3-D image correlation system using digital cameras capable of acquiring images every 5 nano-seconds were used. Due to the nature of the cameras. extensive algorithms for the removable of image distortions were required. The image correlation technology was transferred ... |
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| Evaluation of Skin-Spar Joint Resistance to Hydrodynamic RAM |
MAR 2006 |
357 pages |
| Authors:
Greg Czarneck; Michele Maxson; J. Sawdy; M. Miller; R. Hinrichsen; TEST WING (46TH) WRIGHT-PATTERSON AFB OH AEROSPACE SURVIVABILITY AND SAFETY FLIGHT DIVISION
|
| This paper presents the application of a new dynamic joint loading methodology that uses a RamGun device. Projectile-induced hydrodynamic ram can generate fuel-tank pressures in excess of 10,000 psi. This event is potentially catastrophic for aircraft fuel tanks designed to survive sustained pressures of little more than 50 psi. While the magnitude of ram pressure is dictated by a combination of fuel-level and projectile threat, skin-spar joint design is the ... |
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| Assessment of Design Modifications to Final Clothe the Soldier Rucksack |
MAR 2006 |
41 pages |
| Authors:
S. A. Reid; J. M. Stevenson; QUEEN'S UNIV KINGSTON (ONTARIO)
|
| A modification from Velco and strapping to a sewn attachment method for the shoulder straps of the Clothe the Soldier (CTS) Rucksack was evaluated for: load control, dynamic peak loading and pressure distribution to the torso. Quantitative assessment of these functional parameters was undertaken to compare the behaviour of a proposed modification to that of the currently fielded design to ensure no degradation in performance. This modification was proposed to ... |
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| Effect of Strain Rate on Ductile Fracture |
JAN 2006 |
75 pages |
| Authors:
Wojciech K. Nowacki; Stefan P. Gadaj; Jerzy Luckner; Zdzislaw Nowak; Piotr Perzyna; Ryszard B. Pecherski; POLISH ACADEMY OF SCIENCES WARSAW INST OF FUNDAMENTAL TECHNOLOGICAL RESEARCH
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| This report results from a contract tasking Institute for Fundamental Technological Research of the Polish Academy of Sciences as follows: The effect of strain rate on ductile fracture is one of the least understood phenomena in modern fracture mechanics. At the same time, information on ductile fracture under dynamic loading is very important for reliable prediction of fracture and fragmentation of high consequence structures. High-consequence structures are understood here as ... |
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| A Parabolic Theory of Load Balance |
2006 |
19 pages |
| Authors:
Alan Heirich; Stephen Taylor; CALIFORNIA INST OF TECH PASADENA DEPT OF COMPUTER SCIENCE
|
| We derive analytical results for a dynamic load balancing algorithm modeled by the heat equation. The model is appropriate for quickly diffusing disturbances in a local region of a computational domain without affecting other parts of the domain. The algorithm is useful for problems in computational fluid dynamics which involve moving boundaries and adaptive grids implemented on mesh-connected multicomputers. The algorithm preserves task locality and uses only local communication. Resulting ... |
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| Geometry and Grid Modeling for Numerical Simulation |
JUN 2005 |
86 pages |
| Authors:
John P. Steinbrenner; Todd Michal; Pat J. Yagle; J. P. Abelanet; POINTWISE INC FORT WORTH TX
|
| An application programmer's interface known as API V2 was written to facilitate the sharing of unstructured meshing technology among computational analysts developing or requiring meshing methods. API V2's architecture consists of a database and a meshing library. The database library owns all mesh data and contains API functions for the transfer of data between the mesh library and the application. It also contains functions for dynamic loading of meshing libraries, ... |
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| Modeling Approach for Reducing Helmholtz Resonance in Submarine Structures |
2005 |
13 pages |
| Authors:
S. Arunajatesan; N. Sinha; COMBUSTION RESEARCH AND FLOW TECHNOLOGY INC PIPERSVILLE PA
|
| This paper discusses CFD technology capable of predicting the occurrence of Helmholtz resonance in surface openings of underwater vehicles. An examination of the numerical issues involved in the prediction is discussed - numerical dissipation, turbulence modeling and their interplay are analyzed through detailed parametric simulations. Further, control of such resonance through the use of passive devices is analyzed. Interesting parallels are observed between resonant flow field behavior in a compressible ... |
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| Failure of Tungsten Heavy Alloys Subjected to Dynamic Transverse Loading |
DEC 2004 |
9 pages |
| Authors:
K. Tarcza; S. J. Bless; E. Taleff; TEXAS UNIV AT AUSTIN INST FOR ADVANCED TECHNOLOGY
|
| A new type of experiment has been developed to subject rods to dynamic transverse impact similar to that encountered in attack of modern armors. Two tungsten alloys with five different surface finishes were examined. It was found that there were two failure modes: one involved transverse fracture that initiates from surface flaws. The other was a consequence of gouge instability on the sliding surface. Polishing suppressed the first mode and ... |
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| Model Testing and Numerical Simulations of Seakeeping Performance for High-Speed Vessels |
OCT 2004 |
|
| Authors:
Allen H. Engle; NAVAL SURFACE WARFARE CENTER CARDEROCK DIV BETHESDA MD STRUCTURES AND COMPOSITES DIV
|
| Given the need to support the long distance deployment of men and material, the US Navy has been exploring the engineering limits and capabilities of open ocean operation for high-speed ships. Of great concern are the risks associated with: Ship Motions - Human Factors " " " Ship Dynamic Stability and Manoeuvring Ship Dynamic Loads In order to address these risks, an initial assessment of design tools has been be ... |
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| A Fundamental Investigation into the Deformation and Failure Behavior of Heterogeneous Materials with the Aim of Developing Design Guidelines |
29 JUL 2004 |
66 pages |
| Authors:
Krishnaswarmy Ravi-Chandar; TEXAS UNIV AT AUSTIN CENTER FOR MECHANICS OF SOLIDS STRUCTURES AND MATERIALS
|
| Using the biomimetic idea of gradual changes in the orientation of subsequent layers in fiber reinforced materials, we have developed a helicoidal composite material. In this material, the orientation in each subsequent layer is changed only by 10 degrees; this results in a graded composite material, with significantly reduced interlaminar shear stresses that drive delamination. The mechanisms of failure has been investigated; the material is shown to possess superior mechanical ... |
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| Pseudoelastic SMA Spring Elements for Passive Vibration Isolation: Part I - Modeling |
JUN 2004 |
28 pages |
| Authors:
Mughees M. Kilan; Dimitris C. Lagoudas; John J. Mayes; Benjamin K. Henderson; TEXAS A AND M UNIV COLLEGE STATION DEPT OF AEROSPACE ENGINEERING
|
| In this work, the effect of pseudoelastic response of shape memory alloys (SMAs) on passive vibration isolation has been investigated. This study has been conducted by developing, modeling, and experimentally validating a SMA- based vibration isolation device. This device consists of layers of preconstrained SMA tubes undergoing pseudoelastic transformations under transverse dynamic loading. These SMA tubes are referred to as SMA spring elements in this study. To accurately model the ... |
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| Pseudoelastic SMA Spring Elements for Passive Vibration Isolation: Part II - Simulations and Experimental Correlations |
JUN 2004 |
29 pages |
| Authors:
Dimitris C. Lagoudas; Mughees M. Khan; John J. Mayes; Benjamin K. Henderson; TEXAS A AND M UNIV COLLEGE STATION DEPT OF AEROSPACE ENGINEERING
|
| In Part II of this two-part study, system simulations and experimental correlations of a Shape Memory Alloy (SMA) based vibration isolation device (briefly described in Part I) has been presented. This device consists of layers of pre-constrained SMA tubes undergoing pseudoelastic transformations under transverse dynamical loading. In Part II, detailed description of the prototype vibration isolation device, its experimental setup, and actual experimental test results are presented. An extensive parametric ... |
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| A New Approach to Aeroelastic Response, Stability and Loads of Missiles and Projectiles |
2004 |
43 pages |
| Authors:
Dewey H. Hodges; GEORGIA INST OF TECH ATLANTA SCHOOL OFAEROSPACE ENGINEERING
|
| A current trend in the development of missiles is in the direction of more flexibility, higher maneuverability, and higher speeds, all of which require a higher level of fidelity for calculations of stability, loads, control, and guidance. To address these issues, the present interdisciplinary basic research was conducted involving structural analysis, dynamics, dynamic stability, aeroelastic stability, and trajectory analysis of missiles, rockets, and projectiles. A computer code for the dynamic ... |
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| Field Study of Live Load Distribution Factors and Dynamic Load Allowance on Reinforced Concrete T-Beam Bridges |
AUG 2003 |
60 pages |
| Authors:
Matthew D. Trimble; Thomas E. Cousins; Yazmin Seda-Sanabria; ENGINEER RESEARCH AND DEVELOPMENT CENTER VICKSBURG MS GEOTECHNICAL AND STRUCTURES LAB
|
| This study focuses on the evaluation of live load distribution and dynamic load allowance factors for reinforced concrete T-beam bridges subject to heavy military-vehicle loading. Field displacement measurements on actual bridges were incorporated as part of the evaluation procedure. The vehicle under consideration in this study was a U.S. Army Palletized Loading System (PLS) military vehicle. Results from this evaluation were compared to those obtained from a civilian dump truck ... |
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| Stress Waves and Cohesive Failure in a Finite Strip Subjected to Transient Loading |
MAY 2003 |
7 pages |
| Authors:
George A. Gazonas; David H. Allen; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
|
| New solutions are obtained herein for the dynamic mechanical response of a one-dimensional finite elastic strip that is cohesively bonded to a rigid substrate. Analytic solutions are obtained for a variety of cohesive zone constitutive behaviors including linear elastic, viscous, viscoelastic, and cohesive zones with evolving internal damage. Results are compared to numerically obtained predictions using the explicit finite element code DYNA3D 1. It is shown that the analytic and ... |
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| Active Control of Supersonic Impinging Jets Using Supersonic Microjets |
28 APR 2003 |
144 pages |
| Authors:
Anjaneyulu Krothapalli; Farrukh S. Alvi; Chiang Shih; Anu Annaswamy; FLORIDA AGRICULTURAL AND MECHANICAL UNIV TALLAHASSEE DIV OF SPONSORED RESEARCH
|
| Supersonic impinging jet flows, such as those that occur in the next generation of STOVL aircraft, are highly unsteady due to the presence a feedback loop. This results in large dynamic loads on the nearby aircraft structures and surfaces and diminishes aircraft performance. In this study, a unique active control technique that utilizes arrays of supersonic microjets (less than or equal 400 micrometers) around the periphery of the main jet ... |
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| Evaluation of Alternate Driveshaft Configurations for the FMTV Program. Part 3 of 3 |
28 FEB 2003 |
127 pages |
| Authors:
Hayes Hobolth; Hugh Larsen; Tom Johnson; Charlie Parker; MICHIGAN SCIENTIFIC CORP MILFORD MI
|
| Evaluations of candidate driveshafts for the FMTV program from Dana, Arvin Meritor (2 designs), and GKN were conducted. The evaluations included instrumented road testing. A 1000 mile durability test that included high speed driving and submersion, laboratory measurements, and DADS modeling. The driveshafts were (un)balanced to their manufacturers production limits prior to evaluation and then tested on the vehicle using a special transfer case transducer capable of measuring driveshaft dynamic ... |
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| Lightweight Layered Materials/Structures for Damage Tolerant Armor |
FEB 2003 |
36 pages |
| Authors:
C. T. Sun; K. J. Bowman; J. F. Doyle; H. Espinosa; K. P. Trumble; PURDUE UNIV LAFAYETTE IN
|
| The overall objective of this MURI program was to develop a new class of lightweight armor materials in the form of layered ceramics and metal ceramic composites. This entailed developing novel processing techniques, extensive dynamic experimental evaluations and modeling as well as new analysis and experimental methods. The research program consisted of four major areas: manufacture of layered ceramics and ceramic metal composites for armor, constitutive modeling and damage mechanisms, ... |
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| Numerical Investigation of the Meso-Mechanical Behavior of Concrete Under Impact Tensile Loading |
OCT 2002 |
52 pages |
| Authors:
W. Y. Liu; Lambertus J. Sluys; DELFT UNIV OF TECHNOLOGY (NETHERLANDS)
|
| This report results from a contract tasking Delft University of Technology as follows: The contractor will investigate the mechanical behavior of brittle heterogeneous materials such as concrete extreme dynamic loading conditions. The contractor will develop a mathematical model of brittle heterogeneous materials under extreme dynamic loading conditions to accurately predict civil engineering structural responses not well predicted by existing quasi-static models. |
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| Dynamic Behavior and Shock Absorption Properties of Porous Shape Memory Alloys |
08 JUL 2002 |
12 pages |
| Authors:
Dimitris C. Lagoudas; TEXAS ENGINEERING EXPERIMENT STATION COLLEGE STATION
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| Two methods for producing porous NiTi shape memory alloy (SMA) were used in this work: conventional sintering and sintering at elevated pressure using a Hot Isostatic Press. Depending on various parameters such as sintering times and temperatures, as well as initial powder size and compaction, porous specimens have been produced with varying average pore sizes. The phase transformation temperatures of the porous NiTi specimens were determined using a Differential Scanning ... |
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| High-Speed, High-Temperature Finger Seal Test Results. AIAA/ASME/SAE/ ASEE Joint Propulsion Conference and Exhibit (38th) Held in Indianapolis, IN on July 7-10, 2002 |
JUL 2002 |
19 pages |
| Authors:
Margaret P. Proctor; Arun Kumar; Irebert R. Delgado; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH GLENN RESEARCH CENTER
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| Finger seals have significantly lower leakage rates than conventional labyrinth seals used in gas turbine engines and are expected to decrease specific fuel consumption by over 1 percent and to decrease direct operating cost by over 0.5 percent. Their compliant design accommodates shaft growth and motion due to thermal and dynamic loads with minimal wear. The cost to fabricate these finger seals is estimated to be about half the cost ... |
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| Technique of Multibeam Bridge Span Aeroelastic Oscillations Suppressing |
JUL 2002 |
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| Authors:
S. D. Salenko; NOVOSIBIRSK STATE TECHNICAL UNIV (RUSSIA)
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| At the basis of different methods and means of oscillations extinction the aerodynamic, mechanical, combined principles can lie, the active and passive systems for control can be used. At the basis of mechanical methods lies a change in the natural vibration frequency of construction (due to increase in the hardness, change in the design scheme, etc.), increase of the damping properties of construction as a whole, and also the attachment ... |
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| Dynamic Loading of Polycrystalline Shape Memory Alloy Rods |
27 MAY 2002 |
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| Authors:
Dimitris C. Lagoudas; K. Ravi-Chandar; Khalid Sarh; Peter Popov; TEXAS A AND M UNIV COLLEGE STATION DEPT OF AEROSPACE ENGINEERING
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| Shape Memory Alloys (SMAs) have recently been considered for dynamic loading applications for energy absorbing and vibration damping devices. An SMA body subjected to external dynamic loading will experience large inelastic deformations that will propagate through the body as phase transformation and/or detwinning shock waves. The wave propagation problem in a cylindrical polycrystalline SMA rod induced by an impact loading is considered in this paper. Numerical solutions for various boundary ... |
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