| Comparing the State Estimates of a Kalman Filter to a Perfect IMM Against a Maneuvering Target |
Jul 2011 |
6 pages |
| Authors:
Mark Silbert; Shahram Sarkani; Thomas Mazzuchi; GEORGE WASHINGTON UNIV WASHINGTON DC SCHOOL OF ENGINEERING AND APPLIED SCIENCE
|
 | Tracking maneuvering targets is an important problem. A study was previously performed to compare the state estimation accuracy of a Kalman filter to an interacting multiple model (IMM) for a maneuvering target. The authors defined a maneuvering index to quantify the degree of maneuvering. Their study then compared the state estimates of the two filters as a function of this index. Their results showed that an IMM provides significant improvement ... |
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| Production of Lunar Oxygen Through Vacuum Pyrolysis |
26 JAN 2006 |
71 pages |
| Authors:
John Matchett; GEORGE WASHINGTON UNIV WASHINGTON DC SCHOOL OF ENGINEERING AND APPLIED SCIENCE
|
| Increasing efficiency of future space exploration will require that missions utilize non-terrestrial resources for propellant manufacture. The vacuum pyrolysis method of oxygen production from lunar regolith presents a viable option for in situ propellant production because of its simple operation involving limited resources from earth. Lunar regolith, the fine layer of pulverized rock across the entire lunar surface, is composed of approximately forty percent oxygen in the form of metal ... |
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| Constellation-X Spectroscopy X-Ray Telescope Segmented Optic Alignment Using Piezoelectric Actuators |
18 NOV 2005 |
165 pages |
| Authors:
Thomas F. Meagher; GEORGE WASHINGTON UNIV WASHINGTON DC SCHOOL OF ENGINEERING AND APPLIED SCIENCE
|
| The main instrument for the NASA Constellation-X x-ray observatory is the Spectroscopy X-Ray Telescope (SXT). The SXT is comprised of many thin foil closely nested segmented mirror segments. The mission design requires precise mirror alignment. The contribution of this research is towards the development of the alignment and assembly methods for the SXT optics. The method of alignment uses piezoelectric bending actuators at ten actuation points along the mirror to ... |
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| Vibration Testing of the Constellation X Spectroscopy X-Ray Telescope Reflector Mounting Design |
24 SEP 2005 |
73 pages |
| Authors:
Joshua Schneider; GEORGE WASHINGTON UNIV WASHINGTON DC SCHOOL OF ENGINEERING AND APPLIED SCIENCE
|
| This paper covers the results of four vibration tests performed on the Constellation X Spectroscopy X-Ray Telescope Mirrors. The testing provided critical understanding of the glass strength when subjected to high level vibration loads and helped determine the resonance frequencies of the mirror when mounted using ten grooves in a titanium strut. The data from this testing indicates that the Schott D-263 glass mirrors meets the requirements for glass set ... |
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| Nayesian Aspects of Material Failure, Engineering Reliability, and Software Integrity |
01 NOV 1998 |
5 pages |
| Authors:
Nozer D. Singpurwalla; GEORGE WASHINGTON UNIV WASHINGTON DC SCHOOL OF ENGINEERING AND APPLIED SCIENCE
|
| Research on using Bayesian statistical methods and on probabilistic modeling of failure processes is described. Emphasis is on developing mathematical models for describing the growth of surface and penny shaped cracks in structural materials and on assessing the integrity of software via a new model for software. Initial work on a paradigm for information fusion is discussed and issues such as sensor reliability, sensor sabotage, adversarial sensors and sensor parleying ... |
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| Creep and Fracture Characteristics of Materials and Structures at Elevated Temperatures |
14 FEB 86 |
|
| Authors:
Harold Liebowitz; GEORGE WASHINGTON UNIV WASHINGTON DC SCHOOL OF ENGINEERING AND APPLIED SCIENCE
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 | A major focus of the first year was on the mixed-mode fracture problem. Theoretical work on the computational methodology for the calculation of mixed-mode stress intensity factors was performed. The convergence properties of several algotithms were delineated and guidelines for the accurate calculation of mixed-mode stress intensity factors were established. This study also investigated the effects and influence of loading holes on the calculations. Appendices contained in this report refer ... |
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| The Effect of Low Velocity Impact on The Strength Characteristics of Composite Materials Laminates, |
JAN 1986 |
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| Authors:
H. Liebowitz; E. T. Moyer; GEORGE WASHINGTON UNIV WASHINGTON DC SCHOOL OF ENGINEERING AND APPLIED SCIENCE
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| Static indentation were performed on 8-ply quasi-isotropic graphite/epoxy composite materials to serve as a basis of comparison to dynamic tests. Low velocity impact tests were conducted with the same materials to provide supporting data for a theoretical analysis. Strain was recorded for several locations on both circular and beam-shaped specimens. Strain versus time graphs were then plotted for impacts of various magnitude. (Author, modified). |
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| Flow Induction by Rotary Jets |
86 |
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| Authors:
Charles A. Garris; Joseph V. Foa; GEORGE WASHINGTON UNIV WASHINGTON DC SCHOOL OF ENGINEERING AND APPLIED SCIENCE
|
| Theoretical analyses of generalized flow induction were carried out which showed that the least dissipative mode of flow induction is the cryptosteady mode. Studies were carried out on the energetics of vortex formation showing that in pulsatile thrust augmentors, considerable energy is carried away as kinetic energy of rotation. Parametric studies were conducted on rotary-jet thrust augmentation yielding a best thrust augmentation of 1.97. Theoretical and experimental studies on the ... |
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| EFFECT OF SPECTRUM THICKNESS ON CRACK FRONT PLASTICITY CHARACTERISTICS IN THREE-DIMENSIONS. |
1986 |
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| Authors:
E. MOYER JR.; H. Liebowitz; GEORGE WASHINGTON UNIV WASHINGTON DC SCHOOL OF ENGINEERING AND APPLIED SCIENCE
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| Stochastic Crack Propagation with Applications to Durability and Damage Tolerance Analyses |
SEP 85 |
263 pages |
| Authors:
J. N. Yang; W. H. Hsi; S. D. Manning; GEORGE WASHINGTON UNIV WASHINGTON DC SCHOOL OF ENGINEERING AND APPLIED SCIENCE
|
| Various stochastic models for fatigue crack propagation under either constant amplitude or spectrum loadings have been investigated. These models are based on the assumption that the crack growth rate is a lognormal random process, including the general lognormal random process, lognormal white noise process, lognormal random variable, and second moment approximations, such as Weibull, gamma, lognormal and Gaussian closure approximations. Extensive experimental data have been used for the correlation study ... |
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| Improvement of Fracture Toughness in High Strength Beta Titanium Alloys |
18 MAR 85 |
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| Authors:
P. K. Poulose; H. Liebowitz; GEORGE WASHINGTON UNIV WASHINGTON DC SCHOOL OF ENGINEERING AND APPLIED SCIENCE
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| Specimens of beta titanium alloy, Ti-15-3, were heat treated to different strength levels by single-stage and multi-stage ageing, and hardness, tensile and fracture properties were determined to identify heat treatments well suited for structural applications. These studies were supplemented by microstructural analysis. Attractive combinations of strength and fracture toughness were obtained at medium to high strength levels. The relationship between microstructure and mechanical properties is discussed. |
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| Prediction of Plasticity Characteristics for Three-Dimensional Fracture Specimens Comparison with Experiment |
85 |
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| Authors:
E. T. Moyer Jr.; P. K. Poulose; H. Liebowitz; GEORGE WASHINGTON UNIV WASHINGTON DC SCHOOL OF ENGINEERING AND APPLIED SCIENCE
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| A center-cracked panel of 7075-Aluminum alloy which has overaged from the T651 condition was loaded in tension and subsequently unloaded to zero applied load. The permanent surface deformation was measured close to the intersections of the crack front with the free surfaces. The permanent deformation (being a good indicator of the extent of plastic deformation) was used to measure the accuracy of finite element analyses. The same specimen was modeled ... |
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| Life Prediction for a Structural Material under Cyclic Loads with Hold Times Using a Viscoplastic Constitutive Model |
31 DEC 84 |
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| Authors:
J. Eftis; D. L. Jones; GEORGE WASHINGTON UNIV WASHINGTON DC SCHOOL OF ENGINEERING AND APPLIED SCIENCE
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| This investigation demonstrates the ability of the Chaboche viscoplastic constitutive theory to model the behavior of Ti-6Al-4V alloy at non-elevated temperature. The range of material behavior considered includes uniaxial monotonic stress-strain primary creep, stress relaxation, kinematic and isotropic hardening (and softening) under cyclic loading with and without hold times. The six materials parameters of the viscoplastic theory were evaluated from a series of strain-controlled stabilized cyclic loading tests, and room ... |
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| Picosecond Lidar Techniques in Laboratory and Field Diagnostics |
17 DEC 84 |
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| Authors:
R. Goulard; GEORGE WASHINGTON UNIV WASHINGTON DC SCHOOL OF ENGINEERING AND APPLIED SCIENCE
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| The availability of picosecond laser systems opens a new potential in the field of diagnostics. It is now possible to observe chemical events over time intervals as short as 10 to the minus 9th power sec (e.g., fluorescence, bond-selective chemistry,...) without overlap with the much shorter 10 to the minus 12th power sec triggering signal. In addition, two specific effects are of special interest to real industrial flame diagnostics. One ... |
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| Determination of Failure Characteristics of Materials and Structures |
14 DEC 84 |
|
| Authors:
H. Liebowitz; GEORGE WASHINGTON UNIV WASHINGTON DC SCHOOL OF ENGINEERING AND APPLIED SCIENCE
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| The formulation for general three-dimensional small strain plasticity is presented. A finite element computer code has been developed to carry out the analysis. General hardening characteristics are included as an input option to the program allowing for the study of a wide class of materials. An example through crack problem is solved employing three different hardening assumptions (isotropic, kinematic and mixed). The plastic deformation in the region of the crack ... |
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| Fatigue Crack Propagation in Metastable Titanium Alloys |
JUL 1984 |
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| Authors:
S. H. Yang; A. Raith; C. M. Gilmore; M. A. Imam; GEORGE WASHINGTON UNIV WASHINGTON DC SCHOOL OF ENGINEERING AND APPLIED SCIENCE
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| The fatigue crack growth rate tests of water quenched Corona-5 (Ti-4. 5Al-1.5Cr-5Mo) and Ti-6Al-4V alloy were conducted in air at room temperature. The effect of the presence of the metastable retained beta phase on the fatigue crack growth rate was examined in this research. The specimens were heat treated and water quenched to have unstable beta phase that could be transformed to martensite during the fatigue crack growth testing. As ... |
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| Determination of Failure Characteristics of Materials and Structures |
30 NOV 1983 |
|
| Authors:
H. Liebowitz; GEORGE WASHINGTON UNIV WASHINGTON DC SCHOOL OF ENGINEERING AND APPLIED SCIENCE
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| A research program has been pursued with the objective of examining failure characteristics of materials and structures analytically and experimentally. The expression for the nonlinear energy toughness was rederived for a generalized instability condition and new expressions were derived for biaxial loading situations. The geometry dependence of the nonlinear energy toughness was studied experimentally using center-cracked thin sheet specimens and thicker compact tension specimens of several alloys and compared with ... |
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| Research in Some Applied and the Modelling Aspects of Reliability Theory |
12 SEP 1983 |
|
| Authors:
Nozer D. Singpurwalla; GEORGE WASHINGTON UNIV WASHINGTON DC SCHOOL OF ENGINEERING AND APPLIED SCIENCE
|
| This is a final report which summarizes the research conducted on a large class of topics motivated by reliability and life testing problems. The topics covered include, in alphabetical order, accelerated life tests, Bayesian bioassay, failure rate estimation, goodness of fit testing, Kalman filtering, life testing, quantile estimation, reliability growth monitoring, software reliability, sequential life testing, simulation of Gaussian processed, and time series analysis of reliability data. Most of the ... |
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| Research on Nonsteady Flow Induction |
14 JUL 1983 |
|
| Authors:
Charles A. Garris; Joseph V. Foa; GEORGE WASHINGTON UNIV WASHINGTON DC SCHOOL OF ENGINEERING AND APPLIED SCIENCE
|
| A Flow Induction laboratory has been set up at The George Washington University for use in this project. Experimental work on the rotary jet and on the generation of rotary-jet pseudoblades through the utilization of propagating stall has produced encouraging performance results and useful new information. Additional observations have been made on the energetics of eddy formation. Improvements have been made in the design of rotary jets, and studies of ... |
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| The Mechanical and Microstructural Properties of Quenched and Aged Ti-4. 5Al-5Mo-1.5Cr |
JUL 83 |
|
| Authors:
C. M. Gilmore; S. Yang; M. A. Imam; A. Fraker; A. Van Orden; GEORGE WASHINGTON UNIV WASHINGTON DC SCHOOL OF ENGINEERING AND APPLIED SCIENCE
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| The alloy CORONA-5 (Ti-4.5Al-5Mo-1.5Cr) has been developed as a high fracture toughness alloy with an alpha-beta microstructure. The CORONA-5 alloy was heat treated at temperatures above and below the beta transus and water quenched. Tensile and fatigue properties of the as quenched alloys were determined along with microstructural properties determined by optical and transmission electron microscopy. Low cycle fatigue lives in the as quenched condition were increased significantly whenever retained ... |
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| The Effect of Low Velocity Impact in the Strength Characteristics of Composite Materials Laminates, |
1983 |
|
| Authors:
H. Liebowitz; GEORGE WASHINGTON UNIV WASHINGTON DC SCHOOL OF ENGINEERING AND APPLIED SCIENCE
|
| The nonlinear vibration response of a graphite fiber/epoxy double cantilevered beam subjected to pulse loading over a central sector was studied. The initial response is generated in detail to ascertain the energetics of the reponse. The total energy is used as a gauge of the stability and accuracy of the solution. It is shown that to obtain accurate and stable initial solutions an extremely high spatial and time resolution is ... |
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| Multiangular Scanning Absorption Techniques for Three Dimensional Combustion Diagnostics |
AUG 1982 |
|
| Authors:
Robert Goulard; GEORGE WASHINGTON UNIV WASHINGTON DC SCHOOL OF ENGINEERING AND APPLIED SCIENCE
|
| This program explored the potential of absorption techniques for low ppm, real time three-dimensional combustion diagnostics. Convolution, Fourier transforms and iterative algorithms have already been proven in x-ray absorption tomography and interferometric applications. They have been tested and compared for their ability to determine typical pollutant and radical concentrations as they appear in flames or exhausts. The effect of the number of scans has been analyzed for parallel beams. A ... |
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| Fatigue Failure in Annealed Ti-6Al-4V Microstructures |
82 |
|
| Authors:
C. M. Gilmore; M. A. Imam; GEORGE WASHINGTON UNIV WASHINGTON DC SCHOOL OF ENGINEERING AND APPLIED SCIENCE
|
| Ti-6Al-4V tubing was received in a cold reduced, vacuum annealed condition. Some samples were further vacuum annealed to an alpha-beta anneal, a recrystallization anneal and a beta anneal. High and low cycle fatigue tests were conducted to determine the effect of the type of annealing treatment on fatigue crack initiation. Knoop microhardness values are given for each type of annealing treatment. |
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| Multiangular Scanning Absorption-Emission Techniques for Three Dimensional Combustion Diagnostics |
01 DEC 1981 |
14 pages |
| Authors:
Robert Goulard; GEORGE WASHINGTON UNIV WASHINGTON DC SCHOOL OF ENGINEERING AND APPLIED SCIENCE
|
| This program explores the potential of absorption techniques for low ppm, real time 3-dimensional combustion diagnostics. IN the current phase of activity, a laser beam has been transformed into a sheet of light and made to converge on a 126-element array, with electronics suitable for repeatable 1.5 KHz scanning and data processing. Available memory modules (4K) allow for 34 successive slicings of a passing target within 20 milliseconds. In this ... |
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| Development of Fracture Mechanics Concepts Applicable to Aircraft Structures |
05 NOV 1981 |
|
| Authors:
H. Liebowitz; GEORGE WASHINGTON UNIV WASHINGTON DC SCHOOL OF ENGINEERING AND APPLIED SCIENCE
|
| In Part A of this report, the feasibility of using an accelerated fatigue test program to predict constant amplitude fatigue lives of precracked specimens was examined. An analytical basis for the fracture mechanics approach was developed. The predicted curves from the accelerated test data were found to provide a good fit for the constant amplitude results in 2024-T3 and 7075-T6 aluminum alloys. These results indicate that the accelerated test data ... |
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| Biaxial Tests of Flat Graphite/Epoxy Laminates, |
OCT 1981 |
|
| Authors:
H. Liebowitz; D. L. Jones; GEORGE WASHINGTON UNIV WASHINGTON DC SCHOOL OF ENGINEERING AND APPLIED SCIENCE
|
| The influence of biaxially applied loads on the strength of graphite/epoxy composite materials containing holes examined analytically and experimentally. The analysis was performed through the development of a three-dimensional, finite-element computer program that is capable of considering three types of damage: fiber breakage, delamination, and matrix failure. Realistic failure criteria were established for each of the failure modes and the influence of biaxial loading on damage accumulation under monotonically increasing ... |
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| Feasibility and Benefits of Lateral Placement to Meet the Technical Personnel Shortfall of the U.S. Navy. |
30 JUN 1981 |
|
| Authors:
Walter E. Muller; GEORGE WASHINGTON UNIV WASHINGTON DC SCHOOL OF ENGINEERING AND APPLIED SCIENCE
|
| The United States has reached the point where the technological superiority it has enjoyed in the past may be eliminated by an inability on the part of governmental and industrial personnel (both quantitatively and qualitatively) to implement new scientific advances. One possible solution to the problem is lateral placement--the placement of qualified personnel from academic/vocational sources directly into advanced technical positions. This research postulates opportunities and consequences with respect to ... |
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| Determination of Load Sequence Effects on the Degradation and Failure of Composite Materials |
81 |
|
| Authors:
J. N. Yang; D. L. Jones; GEORGE WASHINGTON UNIV WASHINGTON DC SCHOOL OF ENGINEERING AND APPLIED SCIENCE
|
| A theoretical model was established to predict the fatigue behavior of composite materials, with emphasis placed on predictions of the degradation of residual strength and residual stiffness during fatigue cycling. The model parameters were evaluated from three test series including static strength fatigue life and residual strength tests. The tests were applied to two graphite/epoxy laminates, (+/-35)(sub 2s) and (0,90,+/-45)(sub s). Load sequence effects were emphasized for both laminates and ... |
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| Statistical Crack Growth in Durability and Damage Tolerant Analyses |
81 |
|
| Authors:
J. N. Yang; GEORGE WASHINGTON UNIV WASHINGTON DC SCHOOL OF ENGINEERING AND APPLIED SCIENCE
|
| Under well-controlled laboratory conditions, test results of the fatigue crack growth rate exhibit considerable statistical scatter when specimens are subjected to design loading spectra. Test results of the crack growth rate for 7475-T7351 aluminum specimens under fighter loading spectra have been analyzed statistically and presented. It is shown that two crack growth rate parameters are highly correlated statistical variables, and they can be fitted reasonably well by the log-normal distribution. ... |
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