WorldCat Identities

NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER

Overview
Works: 492 works in 532 publications in 1 language and 567 library holdings
Classifications: TL521.3, 372.3
Publication Timeline
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Most widely held works by NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
Study of Lubricant Jet Flow Phenomena in Spur Gears-Out of Mesh Condition( Book )

1 edition published in 1983 in English and held by 2 WorldCat member libraries worldwide

The objective of the work reported herein was to analytically and experimentally determine the penetration depth onto the tooth flank of a jet oil at different velocities pointed at the pitch line on the outgoing side of mesh. The analysis determines the impingement depth for both the gear and the pinion. It includes the cases for speed increasers and decreasers as well as for one to one gear ratio
Using art to teach science by Ralph A Winrich( Book )

1 edition published in 1984 in English and held by 2 WorldCat member libraries worldwide

This booklet describes 14 student art projects to be used in science classes. Creative skills involved in the process of artistic expression seem to translate very well into the problem solving world of technology. Even in the elementary level it can help build confidence, as well as the development of abstract skills that so often lead to concepts and conclusions. The first project consists of building dioramas in which the third dimension plus imagination and a few facts are combined in a box to make parts of the universe more immediate and real. Another allows students to construct globes of planets in the solar system. A mural project is described in which each grade is assigned a place in the solar system. Other projects suggest that students attempt to draw what various events like the ice age, comets, and asteroid collisions might have looked like from space or earth, design space habitats, or how their classroom could function without gravity. Patches from six space flights are pictured with suggestions for events that students could design patches for. Imagination exercises are included dealing with scientific subjects. Instructions are given for making a book in which the students fill in the pages. Ideas for creative writing, observations with instruments such as a telescope or binoculars, and photography are suggested. Descriptions of planets and moons are the basis for creating landscapes. All of the projects listed are complete with instructions, and suggestions. Many projects include lists of necessary materials and supplies. (DK)
Cold-Air Performance of Compressor-Drive Turbine of Department of Energy Upgraded Automobile Gas Turbine Engine. II. Stage Performance( Book )

2 editions published in 1982 in English and held by 2 WorldCat member libraries worldwide

The aerodynamic performance of the compressor-drive turbine of the DOE Upgraded Gas Turbine (UGT) engine was determined in low-temperature air. The nominal turbine-inlet temperature was 320 K. Inlet pressures were varied between 0.4 and 2.4 bars absolute. The turbine blading used in these tests consisted of duplicates of the stator and rotor castings used in development engine tests. The as-received cast rotor blades had a significantly thicker profile than design and a fairly rough surface finish. Because of these blade profile imperfections three turbine rotor configurations were evaluated. These were the as-cast rotor, a reduced-roughness rotor, and a rotor with the blade profiles thinned to near the design profile. Tests to determine the effect of Reynolds number on the turbine performance were also made. (Author)
Experimental and analytical study of ceramic-coated turbine-tip shroud seals for small turbine engines( Book )

2 editions published in 1985 in English and held by 2 WorldCat member libraries worldwide

An experimental investigation was conducted to validate component rig results and the analytical model of the behavior of a ceramic material in the operating environment of a small turbine engine. The ceramic shroud has the potential of increasing small turbine-engine efficiency through use of higher gas-path temperatures or less shroud cooling air, of extending component life through reduced metal temperatures, or of reducing component weight. The ceramic shrouds were subjected to 1001 cycles between idle and high power and steady-state conditions for a total of 57.8 engine hr. Posttest engine inspection revealed mud-flat surface cracking, which the authors attributed to microcracking under tension with crack penetration to the ceramic-and bond-coat interface. Sections and micrographs tend to corroborate the thesis. The engine test data provided input to a thermomechanical analysis to predict temperature and stress profiles throughtout the ceramic gas-path seal. The analysis predicts cyclic thermal stresses large enough to cause the seal to fail. These stresses are, however, mitigated by inelastic behavior of the shroud materials and by microfracturing that tensile stresses produce. Microfracturing enhances shroud longevity during early life but provides the failure mechanism during extended life when coupled with time-dependent inelastic materials effects. Keywords: Turboshaft engines, Ground tests, and Ceramic bond
Effects of high temperature argon heat treatment on tensile strength and microstructure of BN/SiC coated SiC fiber preforms by Ramakrishna T Bhatt( Book )

3 editions published in 1999 in English and held by 1 WorldCat member library worldwide

Preforms of BN/SiC coated Hi-Nicalon and Sylramic SiC fibers were heat treated under 0.1 MPa argon pressure between 1000 deg to 1800 deg C for 1 and 100h. The effects of high temperature exposure on physical dimensions, weight, room temperature tensile strength, and microstructure of preforms have been studied. Both preforms showed shrinkage and weight loss, and microstructural changes beyond 1000 deg C. After 100 hr exposure, the Hi-Nicalon preforms showed strength degradation beyond 1200 deg C. The mechanisms of the strength degradation appear to be grain growth of the SiC fibers and crystallization of the BN coating. After 100 hr, the Sylramic preforms heat treated to 1000 deg C retained their as-produced strength while some of those heat-treated between 1000 deg and 1800 deg C showed strength degradation and others did not. At 1800 deg C, the ultimate tensile strength decreased with increasing time of exposure. Reasons for strength degradation of Sylramic preforms are being investigated
Experimental performance of a micromachined heat flux sensor by Ștefan Ștefănescu( Book )

3 editions published in 1998 in English and held by 1 WorldCat member library worldwide

Steady-state and frequency response calibration of a microfabricated heat-flux sensor have been completed. This sensor is batch fabricated using standard, micromachining techniques, allowing both miniaturization and the ability to create arrays of sensors and their corresponding interconnects. Both high-frequency and spatial response is desired, so the sensors are both thin and of small cross-sectional area. Thin-film, temperature-sensitive resistors are used as the active gauge elements. Two sensor configurations are investigated: (1) a Wheatstone-bridge using four resistors; and (2) a simple, two-resistor design. In each design, one resistor (or pair) is covered by a thin layer (5000 A) thermal barrier; the other resistor (or pair) is covered by a thick (5 microns) thermal barrier. The active area of a single resistor is 360 microns by 360 microns; the total gauge area is 1.5 mm square. The resistors are made of 2000 A-thick metal; and the entire gauge is fabricated on a 25 microns-thick flexible, polyimide substrate. Heat flux through the surface changes the temperature of the resistors and produces a corresponding change in resistance. Sensors were calibrated using two radiation heat sources: (1) a furnace for steady-state, and (2) a light and chopper for frequency response
Thermodynamic properties of some metal oxide-zirconia systems by Nathan S Jacobson( Book )

3 editions published in 1989 in English and held by 1 WorldCat member library worldwide

Metal oxide-zirconia systems are a potential class of materials for use as structural materials at temperatures above 1900 K. These materials must have no destructive phase changes and low vapor pressures. Both alkaline earth oxide (MgO, CaO, SrO, and BaO)-zirconia and some rare earth oxide (Y2O3, Sc2O3, La2O3, CeO2, Sm2O3, Gd2O3, Yb2O3, Dy2O3, Ho2O3, and Er2O3)-zirconia system are examined. For each system, the phase diagram is discussed and the vapor pressure for each vapor specie is calculated via a free energy minimization procedure. The available thermodynamic literature on each system is also surveyed. Some of the systems look promising for high temperature structural materials
Phenomenological study of the behavior of some silica formers in a high velocity jet fuel burner by James D Cawley( Book )

2 editions published in 1985 in English and held by 1 WorldCat member library worldwide

Silicon based materials are under consideration of a number of applications in aircraft and automative gas turbine engines. The majority of these are monolithic components which benefit from the excellent high temperature strength of some of these materials, eg. sintered alpha silicon carbide and reaction bonded silicon nitride. Another possible application is employing these materials in turbine tip gas path seals. The structural requirement of this application is minimal, however dimensional stability is crucial. The silicon based material are unstable in the presence of oxygen at the high temperatures experienced in the engine. Protection from gross reaction is afforded when an adherent film of Si02 forms on the surface during oxidation. This film serves as a barrier across which mass transport must occur for further oxidation, leading to parabolic scale growth kinetics. The class of materials which displays this behavior is termed silica formers. Samplers of four silica formers: single crystal SiC, sintered alpha-SiC, reaction sintered Si3N4 and polycrystalline MoSi2, were subjected to a Mach 1 jet fuel burner for 1 hr, at a sample temperature of 1375 C (2500 F). Two phenomena were identified which may be deleterious to a gas turbine application of these materials
Steady-state wear and friction in boundary lubrication studies by William R Loomis( Book )

2 editions published in 1980 in English and held by 1 WorldCat member library worldwide

A friction and wear study was made at 20 deg C to obtain improved reproducibility and reliability in boundary lubrication testing. Ester-base and C-ether-base fluids were used to lubricate a pure iron rider in sliding contact with a rotating M-50 steel disk in a friction and wear apparatus. Conditions included loads of 1/2 and 1 kg and sliding velocities of 3.6 to 18.2 m/min in a dry air atmosphere and stepwise time intervals from 1 to 250 min for wear measurements. The wear rate results were compared with those from previous studies where a single 25-min test period was used. Satisfactory test conditions for studying friction and wear in boundary lubrication for this apparatus were found to be 1 kg load; sliding velocities of 7.1 to 9.1 m/min (50 rpm disk speed); and use of a time stepwise test procedure. Highly reproducible "steady-state wear rates" and "steady-state friction coefficients" were determined under boundary conditions. Wear rates and coefficients of friction were constant following initially high values during run-in periods
A framework for a supervisory expert system for robotic manipulators with joint-position limits and joint-rate limits by Arthur G. O Mutambara( Book )

3 editions published in 1998 in English and held by 1 WorldCat member library worldwide

This report addresses the problem of path planning and control of robotic manipulators which have joint-position limits and joint-rate limits. The manipulators move autonomously and carry out variable tasks in a dynamic, unstructured and cluttered environment. The issue considered is whether the robotic manipulator can achieve all its tasks, and if it cannot, the objective is to identify the closest achievable goal. This problem is formalized and systematically solved for generic manipulators by using inverse kinematics and forward kinematics. Inverse kinematics are employed to define the subspace, workspace and constrained workspace, which are then used to identify when a task is not achievable. The closest achievable goal is obtained by determining weights for an optimal control redistribution scheme. These weights are quantified by using forward kinematics. Conditions leading to joint rate limits are identified, in particular it is established that all generic manipulators have singularities at the boundary of their workspace, while some have loci of singularities inside their workspace. Once the manipulator singularity is identified the command redistribution scheme is used to compute the closest achievable Cartesian velocities. Two examples are used to illustrate the use of the algorithm: A three link planar manipulator and the Unimation Puma 560. Implementation of the derived algorithm is effected by using a supervisory expert system to check whether the desired goal lies in the constrained workspace and if not, to evoke the redistribution scheme which determines the constraint relaxation between end effector position and orientation, and then computes optimal gains
Summary and evaluation of the Strategic Defense Initiative Space Power Architecture Study( Book )

3 editions published in 1989 in English and held by 1 WorldCat member library worldwide

The Space Power Architecture Study (SPAS) identified and evaluated power subsystem options for multimegawatt electric (MMWE) space based weapons and surveillance platforms for SDI applications. Steady state requirements of <1 MMWE are adequately covered by the SP-100 nuclear space power program and hence were not addressed in the SPAS. Four steady state power systems <1 MMWE were investigated with little difference between them on a mass basis. The majority of the burst power systems utilized H2 from the weapons and were either closed (no effluent), open (effluent release) or steady state with storage (no effluent). Closed systems used nuclear or combustion heat source with thermionic, Rankine, Turbo alternator, fuel cell and battery conversion devices. Open systems included nuclear or combustion heat sources using turbo alternator, magnetohydrodynamic, fuel cell or battery power conversion devices. The steady state systems with storage used the SP-100 or Star-M reactors as energy sources and flywheels, fuel cells or batteries to store energy for burst applications. As with other studies the open systems are by far the lightest, most compact and simplist (most reliable) systems. However, unlike other studies the SPAS studied potential platform operational problems caused by effluents, vibration, etc
Reasons for low aerodynamic performance of 13.5-centimeter-tip-diameter aircraft engine starter turbine by Jeffrey E Haas( Book )

2 editions published in 1981 in English and held by 1 WorldCat member library worldwide

An experimental investigation was made at the NASA Lewis Research Center to determine the reasons for the low aerodynamic performance of a 13.5-centimeter-tip-diameter aircraft engine starter turbine. The investigation consisted of an evaluation of both the stator and the stage. An approximate 10-percent improvement in turbine efficiency was obtained when the honeycomb shroud over the rotor blade tips was filled to obtain a solid shroud surface. (Author)
Neural network-based sensor validation for turboshaft engines by James C Moller( Book )

2 editions published in 1998 in English and held by 1 WorldCat member library worldwide

Sensor failure detection, isolation, and accommodation using a neural network approach is described. An autoassociative neural network is configured to perform dimensionality reduction on the sensor measurement vector and provide estimated sensor values. The sensor validation scheme is applied in a simulation of the T700 turboshaft engine in closed loop operation. Performance is evaluated based on the ability to detect faults correctly and maintain stable and responsive engine operation. The set of sensor outputs used for engine control forms the network input vector. Analytical redundancy is verified by training networks of successively smaller bottleneck layer sizes. Training data generation and strategy are discussed. The engine maintained stable behavior in the presence of sensor hard failures. With proper selection of fault determination thresholds, stability was maintained in the presence of sensor soft failures
A preliminary study on the vapor/mist phase lubrication of a spur gearbox by Wilfredo Morales( Book )

3 editions published in 1999 in English and held by 1 WorldCat member library worldwide

Organophosphates have been the primary compounds used in vapor/mist phase lubrication studies involving ferrous bearing material. Experimental results have indicated that the initial formation of an iron phosphate film on a rubbing ferrous surface, followed by the growth (by cationic diffusion) of a lubricious pyrophosphate-type coating over the iron phosphate, is the reason organophosphates work well as vapor/mist phase lubricants. Recent work, however, has shown that this mechanism leads to the depletion of surface iron atoms and to eventual lubrication failure. A new organophosphate formulation was developed which circumvents surface iron depletion. This formulation was tested by generating an iron phosphate coating on an aluminum surface. The new formulation was then used to vapor/mist phase lubricate a spur gearbox in a preliminary study
Using dynamic analysis for compact gear design( Book )

3 editions published in 1998 in English and held by 1 WorldCat member library worldwide

This paper presents procedures for designing compact spur gear sets with the objective of minimizing the gear size. The allowable tooth stress and dynamic response are incorporated in the process to obtain a feasible design region. Various dynamic rating factors were investigated and evaluated. The constraints of contact stress limits and involute interference combined with the tooth bending strength provide the main criteria for this investigation. A three-dimensional design space involving the gear size, diametral pitch, and operating speed was developed to illustrate the optimal design of spur gear pairs. The study performed here indicates that as gears operate over a range of speeds, variations in the dynamic response change the required gear size in a trend that parallels the dynamic factor. The dynamic factors are strongly affected by the system natural frequencies. The peak values of the dynamic factor within the operating speed range significantly influence the optimal gear designs. The refined dynamic factor introduced in this study yields more compact designs than AGMA dynamic factors
Low-density, high-strength intermetallic matrix composites by XD synthesis( Book )

2 editions published in 1991 in English and held by 1 WorldCat member library worldwide

There is an increasing need for lightweight high performance materials in today's aerospace arena. High temperature engine designs, for example, require engine materials with elevated temperature strength, creep resistance, damage tolerance, oxidation resistance, and low density. Ordered intermetallics are considered potential alternatives to superalloys because they exhibit many of these properties. A major problem with most ordered alloys is their tendency toward inherently low ductility. The reasons can be quite varied depending on the alloy system, and include poor grain-boundary cohesion, an insufficient number of available slip systems (primarily in non-cubic alloys), limited cross slip, and impurity locking of dislocations. However, intermetallics of high symmetry, such as the L12 structure, have a number of slip systems, which can provide some plasticity, at least at intermediate temperatures, thus enabling the matrix to accommodate some of the strain associated with the thermal stresses
Wave Turbine Analysis Tool Development( Book )

3 editions published in 1998 in English and held by 1 WorldCat member library worldwide

A quasi-one-dimensional (Q-1-D) computational fluid dynamic solver, previously developed and validated for pressure-exchanger wave rotors, is extended in the present work to include the blade forces of power producing wave rotors (i.e., wave turbines). The accuracy of the single-passage Q-1-D solver is assessed relative to two two-dimensional solvers: a single-passage code and a multi-block stator/rotor/stator code. Comparisons of computed results for inviscid, steady and unsteady flows in passage geometries typical of wave rotors reveal that the blade force model is accurate and that the correlation (effective stress and heat flux) terms of the Q-1-D passage-averaged formulation can be neglected. The ends of the rotor passages pose particular challenges to Q-1-D formulations because the flow there must at times deviate significantly from the mean camber line angle to match the port flow fields. This problem is most acute during the opening and closing of the rotor passages. An example sub-model is developed to account for the deviation between the flow departure angle and the mean camber line exit angle that occurs as an inviscid flow decelerates to meet a uniform pressure boundary. Comparisons of results from four-port wave turbine simulations reveal that the Q-1-D solver currently overpredicts wave turbine performance levels and highlight the need to devote future effort to the boundary conditions and sub-models of the Q-1-D solver
Analysis of heat-transfer effects in rocket nozzles operating with very high-temperature hydrogen by John R Howell( )

1 edition published in 1965 in English and held by 0 WorldCat member libraries worldwide

An analytical technique suitable for & the solution of complex energy transfer problems involving coupled radiant and convective energy transfer is developed. Solutions for the coupled axial wall energy flax distribution in rocket nozzles using hydrogen as a propellant are presented. Flow rates and temperatures studied are near those forecast for gaseous-core nuclear-propulsion systems. Parameters varied are nozzle shape, inlet propellant temperature, mean reactor cavity temperature, and nozzle wall temperature level. The effects of variation of the propellant radiation absorption coefficient with pressure, temperature, and wavelength are presented, and real property variations are used where they appear to be significant. Comparison is made to a simplified, coupled solution using a modified second-order one-dimensional diffusion equation for the radiative transfer. At the temperature levels assumed, radiative transfer may account for a greater portion of the total energy transfer over important portions of the nozzle, and its effects cannot, therefore, be neglected. Extreme energy flaxes (near 3XlO to the 8 Btu/(hr)(sq ft)) are observed for certain cases, and this implies that new nozzle cooling techniques must be developed
Effect of component differential hardnesses on residual stress and rolling-contact fatigue by Erwin V Zaretsky( )

1 edition published in 1965 in English and held by 0 WorldCat member libraries worldwide

Residual stress measurements were made in the zone of resolved shearing stress on five SAE 52100 upper test ball specimens with an average Rockwell C hardness of 63.2. These upper test ball specimens were run against lower test balls of nominal Rockwell C hardnesses of 60, 62, 63, 65, and 66 until either ft conditions included an or both components failed because of fatigue. Test conditions included an average race temperature of 150 F, a maximum (Hertz) compressive stress of 800,000 psi, and a highly purified naphthenic mineral oil lubricant. Fatigue lives of the upper test balls were compared with measured residual stresses in the subsurface zone of resolved shearing stress. The compressive residual stress induced in the upper test ball during running is a function of delta H, the hardness of the lower test balls minus the upper test ball hardness An interrelation is indicated among differences in com- ponent hardness, induced compressive residual stress, and fatigue life. Measured values of compressive residual stress within the zone of resolved maximum shearing stress ranged from 178,000 and 294,000 psi. The apparent maximum residual stress occurs above where delta H = 0
Proceedings of the NASA-AEC Liquid-Metals Corrosion Meeting. Volume 1( )

1 edition published in 1964 in English and held by 0 WorldCat member libraries worldwide

The fourth in a series of NASA-AEC Liquid-Metals Corrosion Meeting held October 2-3, 1963, was devoted to discussion of the mechanisms of liquid-metal corrosion, the results of compatibility tests with alkali metals, and the problems related to compatibility testing with alkali metals. Previous meetings in this series dealt with a broader range of topics that include mercury corrosion, liquid-metal analytical chemistry, and liquid-metal properties. In the interest of comprehensive coverage, this meeting was restricted in scope. It was felt that topics not covered could be deferred to meetings under other auspices planned for the near future
 
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English (43)