| Length Scale Considerations in the Formation of Attachment Fatigue Cracks |
AUG 2004 |
17 pages |
| Authors:
Richard W. Neu; David L. McDowell; GEORGIA INST OF TECH ATLANTA SCHOOL OFMECHANICAL ENGINEERING
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 | Fretting fatigue is often the root cause of nucleation of high cycle fatigue (HCF) cracks in clamped components. Fretting fatigue damage accumulation occurs within depths of only a few grains at the interface between contacting components. Therefore, more accurate assumptions concerning length scale, damage volume, and material models are needed to establish a more solid physical foundation underlying fretting fatigue life prediction methods. In particular, the influence of crystallographic orientation ... |
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| Elevated Temperature Fretting Facility |
JUL 2004 |
5 pages |
| Authors:
Richard W. Neu; GEORGIA INST OF TECH ATLANTA SCHOOL OFMECHANICAL ENGINEERING
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| 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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| Fluidic Virtual Aerosurfaces for Flow Control Applications |
MAR 2004 |
74 pages |
| Authors:
Ari Glezer; GEORGIA INST OF TECH ATLANTA SCHOOL OFMECHANICAL ENGINEERING
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| This research program has focused on a novel approach to the control of the aerodynamic performance of lifting surfaces by fluidic modification of their apparent aerodynamic shape, or virtual aerosurface shaping, This flow control approach emphasizes fluidic modification of the "apparent" aerodynamic shape of the surface with the objective of altering or prescribing the streamwise pressure gradient. Control is typically effected by the interactions of arrays of synthetic jet actuators ... |
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| Evolving Multiscale Deformation and Damage in Polycrystals |
12 AUG 2003 |
7 pages |
| Authors:
David L. McDowell; GEORGIA INST OF TECH ATLANTA SCHOOL OFMECHANICAL ENGINEERING
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| The goal of this program was to develop incompatibility-based concepts for linking the kinematics of finite plastic deformation and failure modes across multiple length scales in crystalline and polycrystalline metallics. To do so, we consider the variation through the microstructure of thermodynamic driving forces for damage initiation and growth associated with strong lattice rotations and strain energy localization near heterogeneities such as second phase particles or grain boundary triple points. ... |
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| Nanolaminates and Microlaminates: Modeling and Characterization |
06 AUG 2003 |
6 pages |
| Authors:
Iwona Jasiuk; W. J. Lackey; GEORGIA INST OF TECH ATLANTA SCHOOL OFMECHANICAL ENGINEERING
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| The author fabricated C/SiC laminates with layer thicknesses spanning two length scales (micrometer and nanometer) and fabricated particle-reinforced composites consisting of particles (cobalt and SiC) and polymer matrix (polysterene and epoxy) with particle diameters spanning these two scales. The laminates were made using the laser vapor deposition technique, while the particle-reinforced composites were made using either polymer synthesis or a resin transfer molding technique. The author characterized the ultrastructures of ... |
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| State-Switched Absorber/Damper for Structural Control |
17 DEC 2002 |
15 pages |
| Authors:
Kenneth A. Cunefare; GEORGIA INST OF TECH ATLANTA SCHOOL OFMECHANICAL ENGINEERING
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| This project investigated a novel variation on the concept of a tuned vibration absorber or damper: the State-Switched Absorber (SSA). The SSA is capable of altering its stiffness state nearly instantaneously. The change in stiffness causes a change in the resonance frequencies of the system thereby instantaneously retuning the SSA to a new frequency. The state-switching technique increases the effective bandwidth of the absorber can be made to be effective ... |
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| Active Vibration Control of a Flexible Base Manipulator |
JUL 2002 |
280 pages |
| Authors:
Lynnane E. George; GEORGIA INST OF TECH ATLANTA SCHOOL OFMECHANICAL ENGINEERING
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| A rigid (micro) robot mounted serially to the tip of a long, flexible (macro) robot is often used to increase reach capability, but flexibility in the macromanipulator can make it susceptible to vibration. A rigid manipulator attached to a flexible but unactuated base was used to study a scheme to achieve micromanipulator positioning combined with vibration damping of the base. Inertial interaction forces and torques acting at the base of ... |
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| Numerical Models for Condenser and Evaporator Components of Fuel Cells |
19 APR 2002 |
105 pages |
| Authors:
S. M. Ghiaasiaan; J. H. Yan; B. B. McCord; GEORGIA INST OF TECH ATLANTA SCHOOL OFMECHANICAL ENGINEERING
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| The objective of this project was to develop analytical models and computer programs for the design and analysis of evaporator and condenser components of modern fuel cells. Mechanistic models were developed for boiling and two-phase flow phenomena in Microchannel-based boilers. The modeled systems included straight Microchannel with known inlet/exit boundary conditions; helicoidally micro-channels with known inlet/exit boundary conditions; straight, parallel micro-channels connected to common inlet and exit plena; and straight, ... |
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| Design of a Fuel Cell Moisture and Energy Recovery System |
19 APR 2002 |
75 pages |
| Authors:
Sheldon M. Jeter; S. I. Abdel-Khalik; GEORGIA INST OF TECH ATLANTA SCHOOL OFMECHANICAL ENGINEERING
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| The objective of this project was to design and develop a prototype energy and moisture recovery system for air base fuel cell system. The primary tasks in the project were the design, development, and preliminary testing of the prototype energy and moisture recovery system. The deliverable items are a final report and a prototype energy and moisture recovery system. This report is the deliverable document. In the project, both heat ... |
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| Effects of Noise and Time Delay Upon Active Control of Combustion Instabilities |
30 SEP 2001 |
6 pages |
| Authors:
Ben T. Zinn; Y. Neumeier; E. Lubarsky; C. E. Johnson; J. Lee; GEORGIA INST OF TECH ATLANTA SCHOOL OFMECHANICAL ENGINEERING
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| To improve the performance of practical active control system (ACS) for unstable combustors, the effects of system noise and ACS time delay upon combustion instabilities and the ACS performance were studied. Experimental and theoretical studies of an uncontrolled liquid fueled combustor showed that the presence of noise apparently causes the 'beating' phenomenon and 'phase jumps' exhibited by the unstable pressure oscillations. Next, experiments in which the ACS was operated in ... |
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| Investigating the Integration of a Solid Oxide Fuel Cell and a Gas Turbine System with Coal Gasification Technologies |
SEP 2001 |
62 pages |
| Authors:
Dawson A. Plummer; GEORGIA INST OF TECH ATLANTA SCHOOL OFMECHANICAL ENGINEERING
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| Solid oxide fuel cell (SOFC) technology incorporates electrochemical reactions that generate electricity and high quality heat. The coupling of this technology with gas turbine bottoming cycles, to form hybrid power systems, leads to high efficiency levels. The purpose of this study is to conceptually integrate the hybrid power system with existing and imminent coal gasification technologies. The gasification technologies include the Kellogg Brown Root (KBR) Transport Reactor and entrained coal ... |
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| AASERT: Constitutive and Failure Behavior of Granular Materials |
JUN 2000 |
5 pages |
| Authors:
Min Zhou; GEORGIA INST OF TECH ATLANTA SCHOOL OFMECHANICAL ENGINEERING
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| This project provides support for graduate and undergraduate students to conduct research on the dynamic behavior of concrete and mortar over a range of loading rates and under multiaxial states of stress. The objective of this research is to obtain material response data and constitutive characterization for these materials at strain rates of up to 105 S-1, to analyze the evolution of load-carrying and energy absorption capacities, and to understand ... |
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| Modeling and Analysis of Chilled Water Systems |
APR 2000 |
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| Authors:
Shawn E. Klawunder; GEORGIA INST OF TECH ATLANTA SCHOOL OFMECHANICAL ENGINEERING
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 | The most popular large commercial building chilled water system today is the primary-secondary design. This system separates the generation zone (chiller/evaporator) of a chilled water system from the distribution zone (air handlers). The generation (primary) loop maintains a constant chilled water flow rate. The distribution (secondary) loop varies flow rate in response to cooling load fluctuations. This variable flow rate in the secondary loop permits energy ... |
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| Time-Resolved Analysis of the Dynamic Behavior of Granular Materials |
DEC 1999 |
10 pages |
| Authors:
Min Zhou; GEORGIA INST OF TECH ATLANTA SCHOOL OFMECHANICAL ENGINEERING
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| The objective of this research is to obtain response and constitutive characterization for Concrete and mortar at strain rates up to 105/s, to analyze the evolution of load-carrying and energy absorption capacities, and to understand deformation and failure mechanisms under high pressures. The high rate failure mechanisms considered include fragmentation, comminution and granular flow. Our investigation has focused on (1) the dynamic response of the "G"-mix ... |
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| Fatigue Damage Mechanisms of Advanced Hybrid Titanium Composite Laminates |
NOV 1999 |
133 pages |
| Authors:
Donald W. Rhymer; GEORGIA INST OF TECH ATLANTA SCHOOL OFMECHANICAL ENGINEERING
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| The objective of this thesis is to compare the mechanical response of this advanced Hybrid Titanium Composite Laminates (HTCL) to the first generation material. Specifically, the effect of a stronger bondline at the titanium/ Polymer Matrix Composites (PMC) interface in constant amplitude fatigue will be investigated, particularly in the event that titanium ply cracking induces the delamination. Therefore, the focus of this research is to closely monitor ... |
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| Laminated Matrix Composites - A New Class of Materials |
28 OCT 1999 |
51 pages |
| Authors:
W. J. Lackey; Elliot Pickering; Harry King; Stephen Crain; Mark Renier; GEORGIA INST OF TECH ATLANTA SCHOOL OFMECHANICAL ENGINEERING
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| A new type of composite, which consists of a reinforcement phase plus a matrix composed of many alternate thin layers of two different materials, has been prepared. CVI appears to be an appropriate process for the fabrication of this class of materials. We have successfully fabricated such a composite using the forced flow-thermal gradient CVI process. A carbon 2-D cloth preform was infiltrated with alternate layers ... |
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| Shear Flow Control Using Synthetic Jet Fluidic Actuator Technology |
31 JUL 1999 |
138 pages |
| Authors:
Ari Glezer; GEORGIA INST OF TECH ATLANTA SCHOOL OFMECHANICAL ENGINEERING
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| This research outlined in this report focuses on a novel approach to manipulation and control of shear flows using surface fluidic actuators based on synthetic jet technology. Synthetic jets are zero-mass-flux in nature and are synthesized from the working fluid in the flow system in which they are embedded. Although there is no net mass injection, the jets enable momentum transfer into the flow system to be controlled. Thus the ... |
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| A Two-Dimensional Laser Interferometer System for Dynamic Response Characterization |
30 MAY 1999 |
16 pages |
| Authors:
Min Zhou; GEORGIA INST OF TECH ATLANTA SCHOOL OFMECHANICAL ENGINEERING
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| The objective of this AFOSR DURIP (Defense University Research Instrumentation Program) grant was to establish experimental capabilities for quantifying material responses under highly dynamic conditions. The parent grantwith which this grant is associated is entitled "Time-Resolved Analysis of the Dynamic Behavior of Granular Materials". The capabilities have been established and have been used in the research. A state-of-the-art laser interferometer system has been acquired to allow simultaneous measurement of surface ... |
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| Neural Network Determination of Optical Phase Correction in a Plane Shear Layer Using Parallel Optoelectronic Image Processing and Global Optical Flow Diagnostics |
JUL 1998 |
119 pages |
| Authors:
Martin Brooke; Ari Glezer; Nan Marie Jokerst; GEORGIA INST OF TECH ATLANTA SCHOOL OFMECHANICAL ENGINEERING
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| Neural networks that allow aero-optic phase correction to be made using localized measurements without an external probe beam are being developed in an information-rich laboratory environment. The neural networks are trained to relate phase corrections to low-order modal descriptions of a plane shear layer obtained by a proper orthogonal decomposition (POD) applied to index of refraction data. Optical measurements are taken in a plane shear ... |
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| Integrated Diagnostics |
31 MAY 1998 |
284 pages |
| Authors:
Richard S. Cowan; Ward O. Winer; GEORGIA INST OF TECH ATLANTA SCHOOL OFMECHANICAL ENGINEERING
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| This document provides a review of basic research being conducted in the area of Integrated Diagnostics, a term associated with the technologies and methodologies used to determine how mechanical failures occur, and how they can be detected, predicted and diagnosed in real-time. Objectives, set forth through the Department of Defense Multidisciplinary Research Program of the University Research Initiative (M-URI), are being addressed by faculty and staff from the Georgia Institute ... |
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| Modeling Temperature and Strain Rate History Effects in OFHC Cu |
28 MAY 1998 |
427 pages |
| Authors:
Albert B. Tanner; GEORGIA INST OF TECH ATLANTA SCHOOL OFMECHANICAL ENGINEERING
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| Linking macro-scale material behavior with the evolution of microstructure has proven effective in obtaining an appropriate mathematical structure for constitutive relationships. Incorporation of strain rate, temperature, and deformation path history effects are especially critical to accurately predict material responses for arbitrary non isothermal, variable strain rate conditions. Material constitutive equations contain numerous parameters which must be determined experimentally, and often are not fully optimized. The goal of this research was ... |
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| Applications of Fracture Mechanics to the Durability of Bonded CompositeJoints |
MAY 1998 |
60 pages |
| Authors:
W. S. Johnson; Lawrence M. Butkus; Rodolfo V. Valentin; GEORGIA INST OF TECH ATLANTA SCHOOL OFMECHANICAL ENGINEERING
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| The increased numbers of bonded composite components and bonded repairs of cracked structures make knowledge of adhesive bonding crucial to aircraft design and life extension. This report covers an effort which focused on using fracture mechanics to evaluate the Mode I fracture and fatigue properties of several adhesively bonded aerospace material systems. The research concentrated on bond line cracking rather than fatigue crack growth in composite ... |
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| A Technique for Achieving 4000 Microstrain from Hard PZT |
30 MAR 98 |
9 pages |
| Authors:
Christopher S. Lynch; GEORGIA INST OF TECH ATLANTA SCHOOL OFMECHANICAL ENGINEERING
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| The year 2 effort was divided between experimental characterization of the constitutive behavior of ferroelectric ceramics and reliability of actuators constructed from these materials. Key results of the study of the constitutive behavior under combined stress and electric field loading were the ability to obtain over 3000 microstrain from PZT without excessive hysteresis or cracking and the characterization of several compositions of PZT under high ... |
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| Deformation Behavior of Thin Lubricant Films at Elevated Pressure |
JAN 98 |
46 pages |
| Authors:
Scott Bair; GEORGIA INST OF TECH ATLANTA SCHOOL OFMECHANICAL ENGINEERING
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| If care is taken to avoid viscous heating, the results from rheometers may be used to generate empirical rate equations which are useful in modelling EHD traction. However, an analytical treatment of piezo-viscous liquids reveals the Reynolds equation adequately captures the mechanics of the piezo-viscous liquid only when the shear stress is much less than the reciprocal of the pressure viscosity coefficient. Otherwise the cross film pressure gradient cannot be ... |
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| Structural Acoustics and Hydroacoustics Phenomena in Finite Fluid-Filled Pipes |
1998 |
6 pages |
| Authors:
Minami Yoda; GEORGIA INST OF TECH ATLANTA SCHOOL OFMECHANICAL ENGINEERING
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| The scientific objectives of this project are: 1. To describe and characterize the physical mechanisms which determine how most of the noise radiates from a finite fluid-filled pipe with turbulent flow. 2. To determine criteria which estimate the relative importance of these various mechanisms. 3. To develop experimental and analytical techniques for investigating turbulent flow-structure (hydroacoustic) interactions. |
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| Laser Measurements of Elastic Moduli of Voided Polymers |
20 OCT 1997 |
9 pages |
| Authors:
Yves H. Berthelot; GEORGIA INST OF TECH ATLANTA SCHOOL OFMECHANICAL ENGINEERING
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| The two complex elastic moduli (and the corresponding shear and longitudinal sound speeds) of a voided polymer have been measured as a function of frequency between 0.5 and 2.5 kHz by laser Doppler interferometry and finite element modeling. The measurement errors associated with this new technique are discussed. |
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| Analytical and Experimental Investigation of an Efficient Viscous Pump |
JUN 1990 |
150 pages |
| Authors:
Marlene E. Mainland; GEORGIA INST OF TECH ATLANTA SCHOOL OFMECHANICAL ENGINEERING
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| A viscous pump design is developed and investigated which is more efficient than a viscous pump previously introduced (Etsion and Yaier, 1988). The key to the new design is straight lobes (V-lobes) as opposed to the semicircular lobes of the previous design. The straight lobe analysis, unlike the semicircular lobe analysis, does not produce a closed form solution. Approximations are made that are verified using shape factors and finite element ... |
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