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  • Other Sources  (4,075)
  • PROPULSION SYSTEMS  (2,058)
  • STRUCTURAL MECHANICS  (2,017)
  • Cell & Developmental Biology
  • Chemical Engineering
  • Chemistry
  • General Chemistry
  • Organic Chemistry
  • 2005-2009
  • 1970-1974  (2,966)
  • 1960-1964  (1,109)
Collection
Source
Keywords
Years
Year
  • 1
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    Noise and vibration level reduction by covering metal structures with layers of damping materials (1974)
    In:  CASI
    Details
    Publication Date: 2006-01-11
    Description: One of the most important methods of reducing the noise and vibration level is the damping of the secondary sources, such as metal plates, often used in vehicle structures, by means of covering materials with high internal viscosity. Damping layers are chosen at an optimum thickness corresponding to the frequency and temperature range in which a certain structure works. The structure's response corresponding to various real situations is analyzed by means of a measuring chain including electroacoustical or electromechanical transducers. The experimental results provide the dependence of the loss factor and damping transmission coefficient as a function of the damping layer thickness or of the frequency for various viscoelastic covering materials.
    Keywords: STRUCTURAL MECHANICS
    Type: The 4th Natl. Conf. on Acoustics, Vol. 1A (NASA-TT-F-15375); p 246-253
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  • 2
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    Reduction of diesel engine exhaust noise in the petroleum mining industry (1974)
    In:  CASI
    Details
    Publication Date: 2006-01-11
    Description: An important noise source in a drilling plant is Diesel engine exhaust. In order to reduce this noise, a reactive silencer of the derivative resonator type was proposed, calculated from the acoustic and design point of view and applied. As a result of applying such a silencer on the exhaust conduit of a Diesel engine the noise level dropped down to 18 db.
    Keywords: PROPULSION SYSTEMS
    Type: The 4th Natl. Conf. on Acoustics, Vol. 1A (NASA-TT-F-15375); p 156-162
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  • 3
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    Vibration and recoil control of pneumatic hammers (1974)
    In:  CASI
    Details
    Publication Date: 2006-01-11
    Description: Vibration sources are described for pneumatic hammers used in the mining industry (pick hammers), in boiler shops (riveting hammers), etc., bringing to light the fact that the principal vibration source is the variation in air pressure inside the cylinder. The present state of the art of vibration control of pneumatic hammers as it is practiced abroad, and the solutions adopted for this purpose, are discussed. A new type of pneumatic hammer with a low noise and vibration level is presented.
    Keywords: STRUCTURAL MECHANICS
    Type: The 4th Natl. Conf. on Acoustics, Vol. 1A (NASA-TT-F-15375); p 79-84
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  • 4
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    Vibration control in forge hammers (1974)
    In:  CASI
    Details
    Publication Date: 2006-01-11
    Description: Special measures are discussed for calculating, designing and executing a forge hammer foundation, so that the vibrations that occur during its working will not be transmitted to neighboring machinery, workrooms and offices. These vibrations are harmful to the workers near the forge hammer.
    Keywords: STRUCTURAL MECHANICS
    Type: The 4th Natl. Conf. on Acoustics, Vol. 1A (NASA-TT-F-15375); p 73-78
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  • 5
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    Experimental determination of the vibration level in 5,100 kW electric locomotive assemblies (1974)
    In:  CASI
    Details
    Publication Date: 2006-01-11
    Description: Because of the high vibration level occurring during the running of electric locomotives, mechanical defects occur in the control mechanisms of auxiliary services. This fact has given rise to the necessity of determining the values of these vibrations in electric locomotives during their running. Measurements were conducted on the Craiova-Drobeta-Turnu Severin line, and measures to reduce the vibration level in electric locomotives were instituted.
    Keywords: STRUCTURAL MECHANICS
    Type: The 4th Natl. Conf. on Acoustics, Vol. 1A (NASA-TT-F-15375); p 50-54
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  • 6
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    Random vibrations of linear viscoelastic beams with lumped masses (1974)
    In:  CASI
    Details
    Publication Date: 2006-01-11
    Description: A method is presented of determining the mean square transversal deflection of an isotropic and homogeneous linear viscoelastic beam having a certain number of lengthwise distributed lumped masses. It is assumed that the beam is acted upon by a stationary random process uniformly distributed along the beam. The method is useful in vibration level control by means of additional lumped masses.
    Keywords: STRUCTURAL MECHANICS
    Type: The 4th Natl. Conf. on Acoustics, Vol. 1A (NASA-TT-F-15375); p 36-42
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  • 7
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    Random vibrations of quadratic damping systems (1974)
    In:  CASI
    Details
    Publication Date: 2006-01-11
    Description: An oscillating system with quadratic damping subjected to white noise excitation is replaced by a nonlinear, statistically equivalent system for which the associated Fokker-Planck equation can be exactly solved. The mean square responses are calculated and the optimum damping coefficient is determined with respect to the minimum mean square acceleration criteria. An application of these results to the optimization of automobile suspension damping is given.
    Keywords: STRUCTURAL MECHANICS
    Type: The 4th Natl. Conf. on Acoustics, Vol. 1A (NASA-TT-F-15375); p 29-35
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  • 8
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    The response of many-storied structures under seismic actions (1974)
    In:  CASI
    Details
    Publication Date: 2006-01-11
    Description: A seismic action which is characterized by the acceleration function of the seismic motion is analyzed. The equations of motion in the direction of the seismic action are determined for a completely rigid ground and for a ground with linear deformability characteristics (rotation deformability). The equation for the rotation motion is derived by considering elastic and viscoelastic properties of the foundation ground. The differential equations are written by treating the mechanical model of a many-storied structure as a fixed vertical beam with a uniformly distributed mass as well as with concentrated masses on each floor.
    Keywords: STRUCTURAL MECHANICS
    Type: The 4th Natl. Conf. on Acoustics, Vol. 1A (NASA-TT-F-15375); p 43-49
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  • 9
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    Insulation of nonlinear and random vibrations in the mining industry (1974)
    In:  CASI
    Details
    Publication Date: 2006-01-11
    Description: The insulation of nonlinear and random vibrations is considered for some ore preparing and sorting implements: rotary crushers, resonance screens, hammer mills, etc. The appearance of subharmonic vibrations is analyzed, and the conditions for their appearance are determined. A method is given for calculating the insulation of these vibrations by means of elastic elements made of rubber. The insulation of the random vibrations produced by Symons crushers is calculated by determining the transmissability and deformation of the insulation system for a narrow band random response.
    Keywords: STRUCTURAL MECHANICS
    Type: The 4th Natl. Conf. on Acoustics, Vol. 1A (NASA-TT-F-15375); p 22-28
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  • 10
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    A mathematical model for storied buildings subjected to automatic loom stresses (1974)
    In:  CASI
    Details
    Publication Date: 2006-01-11
    Description: Expressions are derived for the displacements of a many storied building subjected to the action of classical weaving looms located at different levels of the building. The building is regarded as a vertical fixed beam with a uniformly distributed mass as well as concentrated masses at each level. The calculation relations are obtained on the assumption of harmonic variation of the forces acting at each level as well as the assumption of narrow band stationary random excitatory forces.
    Keywords: STRUCTURAL MECHANICS
    Type: The 4th Natl. Conf. on Acoustics, Vol. 1A (NASA-TT-F-15375); p 15-21
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  • 11
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    Study of vibrations produced by a vibrating beam used for vibrating concretes (1974)
    In:  CASI
    Details
    Publication Date: 2006-01-11
    Description: For compacting concretes in building, vibrating beams are used. The vibrations are generated by inertial vibrators, and the beam is normally displaced by the operator by means of a handle that is elastically fastened to the beam by means of rubber pads. Considered are vibrations transmitted to the operator, taking into account the beam's shock vibration motions. The steady state motion of a dynamic beam pattern is studied, and results of experimental tests with existing equipment are presented.
    Keywords: STRUCTURAL MECHANICS
    Type: The 4th Natl. Conf. on Acoustics, Vol. 1A (NASA-TT-F-15375); p 9-14
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  • 12
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    Stresses in dome-shaped shells of revolution with discontinuities at the apex (1974)
    In:  CASI
    Details
    Publication Date: 2006-04-02
    Description: Asymptotic solutions of Novozhilov's equations of shells of revolution are derived for axisymmetric and first harmonic loadings. The solutions obtained are valid throughout the shallow and nonshallow regions. Stresses in dome shaped shells of revolution with a discontinuity in the form of a circular hole, a circular rigid insert, or a nozzle at the apex have been investigated. Numerical results are obtained for spheres, ellipsoids, and paraboloids, containing a discontinuity under a internal pressure and moment. Curves depicting stress distributions are given. The influence of three types of discontinuity on the stresses of the shells is also given.
    Keywords: STRUCTURAL MECHANICS
    Type: Multivariant Function Model Generation; 118 p
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  • 13
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    Current structural vibration problems associated with noise (1974)
    In:  CASI
    Details
    Publication Date: 2011-10-14
    Description: As the performance of aerospace vehicles has increased, the noise generated by the propulsion system and by the passage of the vehicle through the air has also increased. Further increases in performance are now underway for space vehicles such as the space shuttle vehicle and for short distance takeoff and landing (STOL) aircraft, and are being planned for supersonic aircraft. The flight profiles and design features of these high-performance vehicles are reviewed and an estimate made of selected noise-induced structural vibration problems. Considerations for the prevention of acoustic fatigue, noise transmission, and electronic instrument malfunction are discussed.
    Keywords: STRUCTURAL MECHANICS
    Type: AGARD Noise Mech.; 16 p
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  • 14
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    Inclusion of transverse shear deformation in finite element displacement formulations (1974)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: A stiffness matrix is derived for a beam element with transverse shear deformation. It is shown that straightforward energy minimization yields the correct stiffness matrix in displacement formulations when transverse shear effects are considered. Since the TIM4 beam element does not represent the geometric boundary conditions for a cantilever beam the rotation of the normal must be retained as a grid point degree of freedom.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal; 12; Nov. 197
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  • 15
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    Microcraters formed in glass by projectiles of various densities (1974)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: An experiment was conducted investigating the effect of projectile density on the structure and size of craters in soda lime glass and fused quartz. The projectiles were spheres of polystyrene-divinylbenzene (PS-DVB), aluminum, and iron with velocities between 0.5 and 15 km/sec and diameters between 0.4 and 5 microns. The projectile densities spanned the range expected for primary and secondary particles of micrometer size at the lunar surface, and the velocities spanned the lower range of micrometeoroid velocities and the upper range of secondary projectile velocities. There are changes in crater morphology as the impact velocity increases, and the transitions occur at lower velocities for the projectiles of higher density. The sequence of morphological features of the craters found for PS-DVB impacting soda lime glass for increasing impact velocity, described in a previous work (Mandeville and Vedder, 1971), also occurs in fused quartz and in both targets with the more dense aluminum and iron projectiles. Each transition in morphology occurs at impact velocities generating a certain pressure in the target. High density projectiles require a lower velocity than low-density projectiles to generate a given shock pressure.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Geophysical Research; 79; Aug. 10
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  • 16
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    Electric propulsion - Now (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The state of the art of electric propulsion technology is discussed with a review of the many difficult engineering problems which must be resolved before the incorporation of electric propulsion in space missions. Interferences with the spacecraft and its scientific instrumentation, conducted and radiated electromagnetic interferences during the switching and processing of large electrical loads, and mercury and other eroded materials deposition on the spacecraft are indicated among the engineering and design challenges to be overcome and resolved.
    Keywords: PROPULSION SYSTEMS
    Type: AIAA Student Journal; 12; Apr. 197
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  • 17
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    Approximate techniques of structural reanalysis (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: A study is made of two approximate techniques for structural reanalysis. These include Taylor series expansions for response variables in terms of design variables and the reduced-basis method. In addition, modifications to these techniques are proposed to overcome some of their major drawbacks. The modifications include a rational approach to the selection of the reduced-basis vectors and the use of Taylor series approximation in an iterative process. For the reduced basis a normalized set of vectors is chosen which consists of the original analyzed design and the first-order sensitivity analysis vectors. The use of the Taylor series approximation as a first (initial) estimate in an iterative process, can lead to significant improvements in accuracy, even with one iteration cycle. Therefore, the range of applicability of the reanalysis technique can be extended. Numerical examples are presented which demonstrate the gain in accuracy obtained by using the proposed modification techniques, for a wide range of variations in the design variables.
    Keywords: STRUCTURAL MECHANICS
    Type: Computers and Structures; 4; Aug. 197
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  • 18
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    Quiet engine from NASA (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Engine designs resulting from the NASA sponsored quiet engine program are described in terms of their possible use on the DC-8. These engines have high bypass ratios for low jet noise and low-speed, low-noise fans. Experiments were carried out on various fan designs with different tip speeds. The advantage of low tip speeds and high lift coefficients has been demonstrated. The engines are equipped with flight-standard nacelles with acoustic suppression. It is estimated that these improvements will reduce DC-8 noise by about 26EPNdB-29EPNdB.
    Keywords: PROPULSION SYSTEMS
    Type: Flight International; 106; July 25
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  • 19
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    Static, stability, and dynamic analysis of shells of revolution by numerical integration - A comparison (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Recent innovations in digital computer technology have enabled engineers to analyze shell structures of complex configurations without unduly restrictive approximations. An attempt is made to compare the various programs now generally available from the point of view of the advantages of the relative technique utilized, as well as the programmed state of the art. Many of the comparisons are based on the sample problems solved by the STARS-2 system of programs. These examples indicate both the structural detail which can be analyzed by, and the analytical capabilities available in, the numerical shell-of-revolution programs. All advantages and differences are demonstrated by use of solutions for realistic shell problems in the areas of statics, stability, vibrations, and dynamic response of shells subjected to time-dependent loadings.
    Keywords: STRUCTURAL MECHANICS
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  • 20
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    Forced vibrations of multi-component compliant tanks and feedlines (1974)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: An analytical and experimental research program was performed to investigate the effects of flexible tanks and lines and the total system dynamic response of a simple physical system which had some of the essential features of a liquid-fueled launch vehicle. Several vessel-wall materials were used to obtain a range of elastic moduli. Water was used to simulate the fuel and an electromagnetic shaker provided external excitation such as might originate from a rocket-propulsion system. Experimental data were compared to values obtained from mathematical models for the many degree-of-freedom lumped-mass representation.
    Keywords: STRUCTURAL MECHANICS
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  • 21
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    Nonproportional loading limit for structures (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The design of most structures involves ensuring integrity for several independent loading conditions. Often, it is rational to design these, exploiting the ductility of the materials to reduce structural costs. Then, ensuring integrity evokes the need for nonmonotonic limit analyses. A groundwork is laid for implementing these analyses. An alternate limit load characterization to that of Greenberg is provided, a mathematical statement of the problem leading to both monotonic (proportional) and nonmonotonic limit loads values is formulated, a direct limit load analysis procedure for analysis within a finite-element framework is described, and limit loads for sets of simple structures are evaluated. A direct limit analysis process is described, and monotonic limit loads are characterized. The process furnishes 'exact' values of limit loads with increasing efficiency as the number of structural elements and force redundancy decreases. Tests show that the accuracy of predicting nonmonotonic limit loads is very sensitive to the number of degrees of freedom in the analysis compared with the total number in the model.
    Keywords: STRUCTURAL MECHANICS
    Type: Computers and Structures; 4; Mar. 197
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  • 22
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    Putting all our noise technology to work (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: An assessment of the present state of the art in noise reduction technology indicates that this technology has the potential for effectively attaining this goal - a conclusion that is in apparent conflict with the frequently voiced complaints on intolerable noise levels near airports. Measures are suggested for a more vigorous implementation of available technology in practice to combat the aircraft noise problem.
    Keywords: PROPULSION SYSTEMS
    Type: Astronautics and Aeronautics; 12; Jan. 197
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  • 23
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    Adhesive fracture mechanics (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: In studies of fracture mechanics the adhesive fracture energy is regarded as a fundamental property of the adhesive system. It is pointed out that the value of the adhesive fracture energy depends on surface preparation, curing conditions, and absorbed monolayers. A test method reported makes use of a disk whose peripheral part is bonded to a substrate material. Pressure is injected into the unbonded central part of the disk. At a certain critical pressure value adhesive failure can be observed. A numerical stress analysis involving arbitrary geometries is conducted.
    Keywords: STRUCTURAL MECHANICS
    Type: International Journal of Fracture; 10; Mar. 197
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  • 24
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    New triangular plate-bending finite element with transverse shear flexibility (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal; 12; Dec. 197
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  • 25
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    Interactive design of large end rings on stiffened conical shells using composites (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Design study methods and results for a composite reinforced base ring for the conical aeroshell structure of the planetary lander vehicle for Project Viking, an unmanned mission to Mars, are presented. The aeroshell is a ring and stringer-stiffened conical shell structure having a half angle of 70 degrees with a large base ring mounted at the outer edge of the cone and a large pay-load ring in the interior with many smaller rings spaced along the inside shell surface. The purpose of the structure is to develop the aerodynamic drag required to decelerate the lander in the Mars atmosphere to facilitiate a soft landing. The design of a shell structure of this complexity requires the use of the latest technology available in a large general-purpose shell buckling program. The large general-purpose non-linear shell buckling program (BOSOR 2) which was used for this purpose is described.
    Keywords: STRUCTURAL MECHANICS
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    NASA TECHNICAL REPORTS
  • 26
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    Erosion and the gas turbine engine, part 2 (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Procedures for protecting aircraft engines from impact damage due to sand and dust particles are discussed. One system is to develop a filtration system to remove most of the solid particles. Another method is to design blade materials and blade protection coatings. The concepts of erosion within aircraft engines are explained. Curves are presented to show the effect of impingement angle on ductile and elastic modes of erosion. Engine sand and dust ingestion tests were conducted on T63-A-5A engines and the results are produced in graph form. The results of tests conducted in a dynamic erosion facility are analyzed.
    Keywords: PROPULSION SYSTEMS
    Type: NBS The Role of Cavitation in Mech. Failures; p 129-145
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  • 27
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    Boundary value problems with incremental plasticity in granular media (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Discussion of the critical state concept in terms of an incremental theory of plasticity in granular (soil) media, and formulation of the governing equations which are convenient for a computational scheme using the finite element method. It is shown that the critical state concept with its representation by the classical incremental theory of plasticity can provide a powerful means for solving a wide variety of boundary value problems in soil media.
    Keywords: STRUCTURAL MECHANICS
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  • 28
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    A solution to the contact of two rough spherical surfaces (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The influence of roughness on the interfacial pressure distribution in the contact of two spherical surfaces is considered. An approximate general solution is presented and it is shown that the pressure for all radii can be determined solely from a reference pressure which is, in turn, a function of two parameters - a dimensionless roughness and a dimensionless hardness. Values for the radius of contact are also presented.
    Keywords: STRUCTURAL MECHANICS
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  • 29
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    Mixed mode stress field effect in adhesive fracture (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Numerical or analytical analyses were performed on seven different test specimens including blister test, 90-degree peel test, torsion test, and various cone tests. These specimens are in general subjected to complex stress fields having various amounts of Mode I, Mode II, and Mode III loads. The specimens were then constructed using polymethyl methacrylate for the adherends and a transparent polyurethane elastomer (Solithane 113) for the adhesive. This combination permitted direct observation of the bondline as load was applied. Although initial debonds as well as bond end termination singularities were present in all specimens, in some cases the debond did not initiate at the singularity points as would normally have been expected. An explanation for this behavior is presented, as well as a comparison of loading mode effect on those specimens for which the debond did propagate from a bond terminus singular point.
    Keywords: STRUCTURAL MECHANICS
    Type: International Journal of Fracture; 10; Dec. 197
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  • 30
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    Dependence of plate-bending finite element deflections and eigenvalues on Poisson's ratio (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal; 12; Oct. 197
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  • 31
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    Fracture initiation and propagation in a cylindrical shell containing an initial surface flaw (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: An attempt is made to provide the necessary analytical tools for the application of two different types of fracture criteria to shell structures. Of particular interest is the problem of fracture propagation and arrest in a cylindrical pressure vessel containing an initial surface flaw. It is assumed that the flaw has the most unfavorable geometry and orientation, namely, it is a crack lying on a meridional plane. Stress intensity factor for a part-through crack, and a surface or internal crack with a fully yielded net ligament are considered. Attention is given to constant delta curves for depressurization studies and to depressurization and crack arrest in pressure vessels.
    Keywords: STRUCTURAL MECHANICS
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  • 32
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    An overview of high temperature metal fatigue: Aspects covered by the 1973 International Conference on Creep and Fatigue (1974)
    In:  CASI
    Details
    Publication Date: 2012-05-22
    Description: A summary of papers is presented which covers the following broad aspects of high temperature metal fatigue: (1) materials development and characterization; (2) environmental factors, including air, vacuum, helium, iodine, sodium, and radiation environments; (3) general fatigue life relationships; (4) crack growth laws; (5) design code activities; and (6) design and service experience. Illustrative tables accompany the summary.
    Keywords: STRUCTURAL MECHANICS
    Type: AGARD Low Cycle High Temp. Fatigue; 47 p
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  • 33
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    Influence of noise requirements on STOL propulsion system designs (1974)
    In:  CASI
    Details
    Publication Date: 2012-05-22
    Description: The severity of proposed noise goals for STOL systems has resulted in a new design approach for aircraft propulsion systems. It has become necessary to consider the influence of the noise goal on the design of engine components, engine systems, and the integrated nacelle, separately and collectively, from the onset of the design effort. This integrated system design approach is required in order to effect an optimization of the propulsion and aircraft system. Results from extensive design studies and pertinent test programs are presented which show the effect of noise specifications on component and system design, and the trade-offs possible of noise versus configuration and performance. The design optimization process of propulsion systems for powered lift systems is presented beginning with the component level and proceeding through to the final integrated propulsion system. Designs are presented which are capable of meeting future STOL noise regulations and the performance, installation and economic penalties are assessed as a function of noise level.
    Keywords: PROPULSION SYSTEMS
    Type: AGARD V(STOL Propulsion Systems; 17 p
    Format: text
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    Identification of structural parameters from helicopter dynamic test data (1974)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A method is presented for obtaining the mass, stiffness, and damping parameters of a linear mathematical model, having fewer degrees of freedom than the structure it represents, directly from dynamic response measurements on the actual helicopter without a priori knowledge of the physical characteristics of the fuselage. The only input information required in the formulation is the approximate natural frequency of each mode and mobility data measured proximate to these frequencies with sinusoidal force excitation applied at only one point on the vehicle. The practicality and numerical soundness of the theoretical development was demonstrated through a computer simulation of an experimental program.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Ames Res. Center Rotorcraft Dyn.; p 239-248
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  • 35
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    Application of antiresonance theory to helicopters (1974)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Antiresonance theory is the principle underlying nonresonant nodes in a structure, and covers both nonresonant nodes occurring naturally and those introduced by devices such as dynamic absorbers and antiresonant isolators. The dynamic antiresonant vibration isolator (DAVI) and the nodale module are examples of the applications of transfer antiresonances. It is shown that antiresonances are eigenvalues, and that they can be determined by matrix iteration. Applications of antiresonance theory to helicopter engineering problems, using the antiresonant eigenvalue equation are suggested.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Ames Res. Center Rotorcraft Dyn.; p 101-106
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  • 36
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    Correlation of finite-element structural dynamic analysis with measured free vibration characteristics for a full-scale helicopter fuselage (1974)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The correlation achieved with each program provides the material for a discussion of modeling techniques developed for general application to finite-element dynamic analyses of helicopter airframes. Included are the selection of static and dynamic degrees of freedom, cockpit structural modeling, and the extent of flexible-frame modeling in the transmission support region and in the vicinity of large cut-outs. The sensitivity of predicted results to these modeling assumptions are discussed. Both the Sikorsky Finite-Element Airframe Vibration analysis Program (FRAN/Vibration Analysis) and the NASA Structural Analysis Program (NASTRAN) have been correlated with data taken in full-scale vibration tests of a modified CH-53A helicopter.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Ames Res. Center Rotorcraft Dyn.; p 67-80
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  • 37
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    Flight velocity effects on jet noise of several variations of a twelve-chute suppressor installed on a plug nozzle (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Because of the relatively high takeoff speeds of supersonic transport aircraft, it is important to know whether the flight velocity effects the noise level of suppressor nozzles. To investigate this, a modified F-106B aircraft was used to conduct a series of flyover and static tests on a 12-chute suppressor installed on an uncooled plug nozzle. Comparison of flyover and static spectra indicated that flight velocity adversely affected noise suppressions of the 12-chute configurations.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-TM-X-2918 , E-7449
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  • 38
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    FORTRAN program to generate engine inlet flow contour maps and distortion parameters (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A computer program is presented and described that generates jet engine inlet flow contour maps and inlet flow distortion parameters. The program input consists of an array of measurements describing the flow conditions at the engine inlet. User-defined distortion parameters may be calculated.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-TM-X-2967 , E-7572
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  • 39
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    Thrust performance of isolated plug nozzles with two types of 40-spoke noise suppressor at Mach numbers from 0 to 0.45 (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Plug nozzles with two types of 40-spoke noise suppressor were tested at free-stream Mach numbers from 0 to 0.45 and over a range of nozzle pressure ratios from 1.5 to 4.0. In additon, an unsuppressed plug nozzle and a Supersonic Tunnel Association nozzle were also tested to provide baseline levels of thrust performance. The unsuppressed plug nozzle had an efficiency of 98 percent at an assumed takeoff pressure ratio of 3.0 and at Mach 0.36. At the same condition the suppressor nozzles had efficiencies of approximately 83.5 percent.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-TM-X-2951 , E-7541
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  • 40
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    Flight velocity effects on jet noise of several variations of a 48-tube suppressor installed on a plug nozzle (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Because of the relatively high takeoff speeds of supersonic transport aircraft, it is important to know if the flight velocity affects the noise level of suppressor nozzles. To investigate this, a modified F-106B aircraft was used to conduct a series of flyover and static tests on a 48-tube suppressor installed on an uncooled plug nozzle. Comparison of flyover and static spectra indicated that flight velocity had little effect on the noise suppression of the 48-tube suppressor configuration. However, flight velocity adversely affected noise suppression of the 48-tube suppressor with an acoustic shroud and plug installed.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-TM-X-2919 , E-7513
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  • 41
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    SERT C project study (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The SERT C (Space Electric Rocket Test - C) project study defines a spacecraft mission that would demonstrate the technology readiness of ion thruster systems for primary propulsion and station keeping applications. As a low cost precursor, SERT C develops the components and systems required for subsequent Solar Electric Propulsion (SEP) applications. The SERT C mission requirements and preliminary spacecraft and subsystem design are described.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-TM-X-71508
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  • 42
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    Transonic single-mode flutter and buffet of a low aspect ratio wing having a subsonic airfoil shape (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Transonic flutter and buffet results obtained from wind-tunnel tests of a low aspect ratio semispan wing model are presented. The tests were conducted to investigate potential transonic aeroelastic problems of vehicles having subsonic airfoil sections. The model employed NACA 00XX-64 airfoil sections in the streamwise direction and had a 14 deg leading edge sweep angle. Aspect ratio, and average thickness were 4.0, 0.35, and 8 percent, respectively. The model was tested at Mach numbers from 0.6 to 0.95 at angles of attack from 0 deg to 15 deg. Two zero lift flutter conditions were found that involved essentially single normal mode vibrations. With boundary layer trips on the model, flutter occurred in a narrow Mach number range centered at about Mach 0.90. The frequency and motion of this flutter were like that of the first normal mode vibration. With the trips removed flutter occurred at a slightly high Mach number but in a mode strongly resembling that of the second normal mode.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TN-D-7346 , A-4966
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  • 43
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    Transverse vibrations of non-uniform beams (1974)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The free vibrations of elastic beams with nonuniform characteristics are investigated theoretically by a new method. The new method is seen to combine the advantages of a finite element approach and of a Rayleigh-Ritz analysis. Comparison with the known analytical results for uniform beams shows good convergence of the method for natural frequencies and modes. For internal shear forces and bending moments, the rate of convergence is less rapid. Results from experiments conducted with a cantilevered helicopter blade with strong nonuniformities and also from alternative theoretical methods, indicate that the theory adequately predicts natural frequencies and mode shapes. General guidelines for efficient use of the method are presented.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Sound and Vibration; 37; Dec. 22
    Format: text
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  • 44
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    Two-dimensional cold-air cascade study of a film-cooled turbine stator blade. 1: Experimental results of pressure-surface film cooling tests (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The effect of film coolant ejection from the pressure side of a stator blade was determined in a two-dimensional cascade. Stator exit surveys were made for each of six rows of coolant holes. Successive multirow tests were made with two, three, four, five, and six rows of coolant holes open. The results of the multirow tests are compared with the predicted multirow performance obtained by adding the single-row data. Results are presented in terms of stator primary-air efficiency as a function of coolant fraction.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-TM-X-3045 , E-7817
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  • 45
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    Non-linear behavior of fiber composite laminates (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The non-linear behavior of fiber composite laminates which results from lamina non-linear characteristics was examined. The analysis uses a Ramberg-Osgood representation of the lamina transverse and shear stress strain curves in conjunction with deformation theory to describe the resultant laminate non-linear behavior. A laminate having an arbitrary number of oriented layers and subjected to a general state of membrane stress was treated. Parametric results and comparison with experimental data and prior theoretical results are presented.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-2313 , TFR/7309
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  • 46
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    Failure criteria for viscoelastic materials (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Research projects concerned with developing a theory of fracture of materials are discussed. The effects of the geometry of the structure and the loads acting on the structure as they influence the failure process are analyzed. The effects of the viscoelastic deformation characteristics of the bulk elastomer on failure behavior are examined. Additional material parameters which control the fracture process are identified.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-138125 , GALCIT-120
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  • 47
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    Advance development of a technique for characterizing the thermomechanical properties of thermally stable polymers (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The torsional braid experiment has been interfaced with a centralized hierarchical computing system for data acquisition and data processing. Such a system, when matched by the appropriate upgrading of the monitoring techniques, provides high resolution thermomechanical spectra of rigidity and damping, and their derivatives with respect to temperature.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-138123
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  • 48
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    Basic performance of a multilayer insulation system containing 20 to 160 layers (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An experimental investigation was conducted to determine the thermal effectiveness of an aluminized Mylar-silk net insulation system containing up to 160 layers. The experimentally measured heat flux was compared with results predicted by using (1) a previously developed semi-empirical equation and (2) an effective-thermal-conductivity value. All tests were conducted at a nominal hot-boundary temperature of 294 K (530 R) with liquid hydrogen as the heat sink. The experimental results show that the insulation performed as expected and that both the semi-empirical equation and effective thermal conductivity of a small number of layers were adequate in predicting the thermal performance of a large number of layers of insulation.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-TN-D-7659 , E-7815
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  • 49
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    Analysis of laminated, composite, circular cylindrical shells with general boundary conditions (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: This report develops: (1) a refined approximate theory for the static and dynamic analyses of finite, laminated, composite, circular cylindrical shells with general boundary conditions; (2) an exact three-dimensional analysis of simply supported, laminated, composite, circular cylindrical shells, and (3) a thin-shell theory for laminated, composite, circular cylindrical shells. In the refined approximate theory the displacements are assumed piecewise linear across the thickness and the effects of transverse shear deformations and transverse normal stress are included. A variational approach is followed to obtain the governing differential equations and boundary conditions. A general solution of the governing differential equations is also presented. The results obtained by using the refined approximate theory and the thin-shell theory are compared with the exact results for the case of free vibrations of simply supported, laminated, composite, circular cylindrical shells. The refined approximate theory is very accurate, even for thick shells with short nodal distances, whereas thin-shell theory is reasonably accurate only for thin shells at moderate nodal distances and wave number less than 2.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TR-R-412 , L-8828
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  • 50
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    Holographic nondestructive tests performed on composite samples of ceramic-epoxy-fiberglass sandwich structure (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: When a hologram storing more than one wave is illuminated with coherent light, the reconstructed wave fronts interfere with each other or with any other phase-related wave front derived from the illuminating source. This multiple wave front comparison is called holographic interferometry, and its application is called holographic nondestructive testing (HNDT). The theoretical aspects of HNDT techniques and the sensitivity of the holographic system to the geometrical placement of the optical components are briefly discussed. A unique HNDT system which is mobile and possesses variable sensitivity to stress amplitude is discribed, the experimental evidence of the application of this system to the testing of the hidden debonds in a ceramic-epoxy-fiberglass structure used for sample testing of the radome of the Pershing missile system is presented.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TR-R-430 , M-461
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    Procedures for experimental measurement and theoretical analysis of large plastic deformations (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Theoretical equations are derived and analytical procedures are presented for the interpretation of experimental measurements of large plastic strains in the surface of a plate. Orthogonal gage lengths established on the metal surface are measured before and after deformation. The change in orthogonality after deformation is also measured. Equations yield the principal strains, deviatoric stresses in the absence of surface friction forces, true stresses if the stress normal to the surface is known, and the orientation angle between the deformed gage line and the principal stress-strain axes. Errors in the measurement of nominal strains greater than 3 percent are within engineering accuracy. Applications suggested for this strain measurement system include the large-strain-stress analysis of impact test models, burst tests of spherical or cylindrical pressure vessels, and to augment small-strain instrumentation tests where large strains are anticipated.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-X-3027 , E-7661
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  • 52
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    Analysis of three-point-bend test for materials with unequal tension and compression properties (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An analysis capability is described for the three-point-bend test applicable to materials of linear but unequal tensile and compressive stress-strain relations. The capability consists of numerous equations of simple form and their graphical representation. Procedures are described to examine the local stress concentrations and failure modes initiation. Examples are given to illustrate the usefulness and ease of application of the capability. Comparisons are made with materials which have equal tensile and compressive properties. The results indicate possible underestimates for flexural modulus or strength ranging from 25 to 50 percent greater than values predicted when accounting for unequal properties. The capability can also be used to reduce test data from three-point-bending tests, extract material properties useful in design from these test data, select test specimen dimensions, and size structural members.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TN-D-7572 , E-7544
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  • 53
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    FORTRAN 4 programs for summarization and analysis of fracture trace and lineament patterns (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Systematic and detailed analysis of lineament and fracture trace patterns has long been neglected because of the large number of observations involved in such an analysis. Three FORTRAN 4 programs were written to facilitate this manipulation. TRANSFORM converts the initial fracture map data into a format compatible with AZMAP, whose options allow repetitive manipulation of the data for optimization of the analysis. ROSE creates rose diagrams of the fracture patterns suitable for map overlays and tectonic interpretation. Examples are given and further analysis techniques using output from these programs are discussed.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-X-70596 , X-644-74-3
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    Sensitivity analysis of torsional vibration characteristics of helicopter rotor blades. Part 2: Aerodynamics and sensitivity analysis (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A theoretical investigation of dynamic response characteristics of rotor blades was carried out with special emphasis on torsional degrees-of-freedom. Coupled equations of motion for flapwise bending and torsion were formulated at varying azimuth positions for rotor blades with noncollinear aerodynamic, elastic and mass axes. Both structural and aerodynamic mass, damping and stiffness coefficients were included. The variations of a sample blade at different flight conditions were investigated from these equations. The obtained numerical results were illustrated. The sensitivity of overall blade vibration characteristics to torsional oscillations was also investigated from the equations of motion for the sample blade. The illustrated results show the importance of torsional degrees-of-freedom in rotor blade analysis. Various possibilities of improving the overall response by tuning blade geometric, structural and aerodynamic characteristics are discussed.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-2380
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  • 55
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    Solar array study for solar electric propulsion spacecraft for the Encke rendezvous mission (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The work is described which was performed on the design, analysis and performance of a 20 kW rollup solar array capable of meeting the design requirements of a solar electric spacecraft for the 1980 Encke rendezvous mission. To meet the high power requirements of the proposed electric propulsion mission, solar arrays on the order of 186.6 sq m were defined. Because of the large weights involved with arrays of this size, consideration of array configurations is limited to lightweight, large area concepts with maximum power-to-weight ratios. Items covered include solar array requirements and constraints, array concept selection and rationale, structural and electrical design considerations, and reliability considerations.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-136860 , JPL-TM-33-668
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  • 56
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    Performance of a hydrogen burner to simulate air entering scramjet combustors (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Tests were conducted to determine the performance of a hydrogen burner used to produce a test gas that simulates air entering a scramjet combustor at various flight conditions. The test gas simulates air in that it duplicates the total temperature, total pressure, and the volume fraction of oxygen of air at flight conditions. The main objective of the tests was to determine the performance of the burner as a function of the effective exhaust port area. The conclusions were: (1) pressure oscillations of the chugging type were reduced in amplitude to plus or minus 2 percent of the mean pressure level by proper sizing of hydrogen, oxygen, and air injector flow areas; (2) combustion efficiency remained essentially constant as the exhaust port area was increased by a factor of 3.4; (3) the mean total temperature determined from integrating the exit radial gas property profiles was within plus or minus 5 percent of the theoretical bulk total temperature; (4) the measured exit total temperature profile had a local peak temperature more than 30 percent greater than the theoretical bulk total temperature; and (5) measured heat transfer to the burner liner was 75 percent of that predicted by theory based on a flat radial temperature profile.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-TN-D-7567 , L-9363
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    Experimental investigation of a 4 and 1/2 stage turbine with very high stage loading factor. 2: Turbine performance (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The experimental test program results of a 4 1/2-stage turbine with a very high stage loading factor are presented. A four-stage turbine was tested with and without outlet turning vanes. The 4 1/2-stage turbine achieved a design point total-to-total efficiency of 0.853. The outlet turning vane design point performance was 0.4 percent of the overall 4 1/2-stage turbine efficiency. Tests were conducted at various levels of Reynolds number and indicated decreases in turbine efficiency and equivalent weight flow with decreasing Reynolds number.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-2363 , R73AEG163
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  • 58
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    Single-stage experimental evaluation of tandem-airfoil rotor and stator blading for compressors. Part 7: Data and performance for stage E (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An axial flow compressor stage, having tandem airfoil blading, was designed for zero rotor prewhirl, constant rotor work across the span, and axial discharge flow. The stage was designed to produce a pressure ratio of 1.265 at a rotor tip velocity of 757 ft/sec. The rotor has an inlet hub/tip ratio of 0.8. The design procedure accounted for the rotor inlet boundary layer and included the effects of axial velocity ratio and secondary flow on blade row performance. The objectives of this experimental program were (1) to obtain performance with uniform and distorted inlet flow for comparison with the performance of a stage consisting of single-airfoil blading designed for the same vector diagrams and (2) to evaluate the effectiveness of accounting for the inlet boundary layer, axial velocity ratio, and secondary flows in the stage design.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-134529 , FR-5955
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  • 59
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    Exploratory tests of two strut fuel injectors for supersonic combustion (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Results of supersonic mixing and combustion tests performed with two simple strut injector configurations, one with parallel injectors and one with perpendicular injectors, are presented and analyzed. Good agreement is obtained between static pressure measured on the duct wall downstream of the strut injectors and distributions obtained from one-dimensional calculations. Measured duct heat load agrees with results of the one-dimensional calculations for moderate amounts of reaction, but is underestimated when large separated regions occur near the injection location. For the parallel injection strut, good agreement is obtained between the shape of the injected fuel distribution inferred from gas sample measurements at the duct exit and the distribution calculated with a multiple-jet mixing theory. The overall fraction of injected fuel reacted in the multiple-jet calculation closely matches the amount of fuel reaction necessary to match static pressure with the one-dimensional calculation. Gas sample measurements with the perpendicular injection strut also give results consistent with the amount of fuel reaction in the one-dimensional calculation.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-TN-D-7581 , L-9428
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  • 60
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    Assembly and analysis of fragmentation data for liquid propellant vessels (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Fragmentation data was assembled and analyzed for exploding liquid propellant vessels. These data were to be retrieved from reports of tests and accidents, including measurements or estimates of blast yield, etc. A significant amount of data was retrieved from a series of tests conducted for measurement of blast and fireball effects of liquid propellant explosions (Project PYRO), a few well-documented accident reports, and a series of tests to determine auto-ignition properties of mixing liquid propellants. The data were reduced and fitted to various statistical functions. Comparisons were made with methods of prediction for blast yield, initial fragment velocities, and fragment range. Reasonably good correlation was achieved. Methods presented in the report allow prediction of fragment patterns, given type and quantity of propellant, type of accident, and time of propellant mixing.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-134538
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    Stress anisotropy and concentration effects in high pressure measurements (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Sodium chloride is used as an internal pressure standard in high pressure research. Possible corrections are discussed which are needed in the calibration of this standard due to the independent effects of stress anisotropy and stress concentration in pressure vessels. The first is due to the lack of a truly hydrostatic state of stress in solid state pressure vessels. The second is due to the difference in the compressibilities between the pressure transmitting substances (sodium chloride) and a stiffer test specimen. These two corrections are then combined and a total correction, as a function of measured pressure, is discussed for two systems presently in use. The predicted value of the combined effect is about 5-10% of the pressure at 30 GPa.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-142600 , REPT-2345
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    Elastic moduli of precompressed pyrophyllite used in ultrahigh pressure research (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The propagation of ultrasonic pulses in pyrophyllite specimens was studied to determine the effect of specimen precompression on the measured elastic moduli. Measurements were made at room pressure and, for the precompressed specimens, to pressures of 3 kbar. Pyrophyllite was found to be elastically anisotropic, apparently the result of the fabric present in our material. The room pressure adiabatic bulk modulus as measured on specimens made of isostatically compacted powered pyrophyllite was determined to be 96.1 kbar. The wave speeds of ultrasonic pulses in pyrophyllite were found to decrease with increasing specimen precompression. A limiting value of precompression was found, above which no further decrease in wave speed was observed. For the shear wave speeds this occurs at 10 kbar while for the longitudinal wave at 25 kbar. In the limit, the shear waves propagate 20% slower than in the unprecompressed samples; for the longitudinal wave the difference is 30%.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-142598 , REPT-2366
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  • 63
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    Contact and crack problems for an elastic wedge (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The contact and the crack problems for an elastic wedge of arbitrary angle are considered. The problem is reduced to a singular integral equation which, in the general case, may have a generalized Cauchy kernel. The singularities under the stamp as well as at the wedge apex were studied, and the relevant stress intensity factors are defined. The problem was solved for various wedge geometries and loading conditions. The results may be applicable to certain foundation problems and to crack problems in symmetrically loaded wedges in which cracks initiate from the apex.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-132640
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  • 64
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    Jet engine exhaust noise due to rough combustion and nonsteady aerodynamic sources (1974)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Keywords: PROPULSION SYSTEMS
    Type: Acoustical Society of America; vol. 56
    Format: text
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  • 65
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    Derivatives of eigenvalues and eigenvectors for a general matrix (1974)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Expressions are obtained for the derivatives of the eigenvalues and eigenvectors which are expressions of only one left-hand and one right-hand eigenvector. The approach described makes use of a Choleski decomposition or some other decomposition method. The method may be extended to find any order of derivative of the eigenvalue and eigenvector. The expressions obtained for finding the derivatives of eigenvalues and eigenvectors for nonself-adjoint systems may be applied to self-adjoint systems.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal; 12; May 1974
    Format: text
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  • 66
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    An experimental-theoretical study of free vibrations of plates on elastic point supports (1974)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: A theoretical and experimental study is made to investigate the effect on plate vibrations of varying the stiffness of corner elastic point supports. An experiment is conducted in which the bending stiffness of horizontal beams is used to support a square plate at its four corners. The stiffness of these supports can be varied over such a range that the plate fundamental frequency is lowered to 40% of the rigid support frequency. The variation with support stiffness of the frequencies of the first eight plate modes is measured and is compared with results from a theoretical model in which a Rayleigh-Ritz analysis is used which approximates the plate mode shapes as products of free-free beam modes. The elastic point supports are modeled both as massless translational springs and springs with tip masses, which are included to better represent the experimental supports.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Sound and Vibration; 32; Feb. 22
    Format: text
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  • 67
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    Design manual: Oxygen Thermal Test Article (OTTA) (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The characteristics of a cryogenic tank for storing liquid hydrogen, nitrogen, oxygen, methane, or helium for an extended period of time with minimum losses are discussed. A description of the tank and control module, assembly drawings and details of major subassemblies, specific requirements controlling development of the system, thermal concept considerations, thermal analysis methods, and a record of test results are provided. The oxygen thermal test article thermal protection system has proven that the insulation system for cryogenic vessels is effective.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-140209 , ER15961
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  • 68
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    Research on the elastic stability of large shells (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Tests were conducted to determine the elastic stability of large shell structures. The configuration of the shells and the instrumentation used in the measurements are described. The testing procedures are explained. Results of the stress analysis are plotted in polar graph form to show the areas of strain in micro inches at the outer surface of the skin and the inner lip of the stringer.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-139665 , SAPR-6
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  • 69
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    Eight cm technology thruster development (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A structural integrated ion thruster with 8-cm beam diameter (SIT-8) was developed for attitude control and stationkeeping of synchronous satellites. As optimized, the system demonstrates a thrust T=1.14 mlb (not corrected for beam V sub B = 1200 V (I sub sp = 2200 sec) total propellant utilization efficiency nu sub u = 59.8% (is approximately 72% without auxiliary pulse-igniter electrode), and electrical efficiency n sub E 61.9%. The thruster incorporates a wire-mesh anode and tantalum cover surfaces to control discharge chamber flake formation and employs an auxiliary pulse-igniter electrode for hollow-cathode ignition. When the SIT-8 is integrated with the compatible SIT-5 propellant tankage, the system envelope is 35 cm long by 13 cm flange bolt circle with a mass of 9.8 kg including 6.8 kg of mercury propellant. Two thrust vectoring systems which generate beam deflections in two orthogonal directions were also developed under the program and tested with the 8-cm thruster. One system vectors the beam over + or - 10 degrees by gimbaling of the entire thruster (not including tankage), while the other system vectors the beam over + or - 7 degrees by translating the accel electrode relative to the screen electrode.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-134685
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  • 70
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    Overall and blade-element performance of a 1.20-pressure-ratio fan stage at design blade setting angle (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A 51-cm-diam. model of a short-haul fan stage was tested. Surveys of the air flow conditions ahead of the rotor, between the rotor and stator, and behind the stator were made over the stable operating range of the stage. At the design speed of 213.3 m/sec and weight flow of 26.7 kg/sec, the stage pressure ratio and efficiency are 1.18 and 0.87, respectively. The rotor peak efficiency of 0.92 occurred at flow rate of 30.5 kg/sec. Peak stage efficiency of 0.09 was obtained at 110 percent speed at a pressure ratio of 1.218 and a weight flow of 30.2 kg/sec. Maximum stage pressure ratio is 1.269 at 120 percent speed.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-TM-X-3101 , E-7791
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  • 71
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    Task 12 data dump (phase 2) OME integrated thrust chamber test report (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The characteristics and performance of the orbit maneuvering engine for the space shuttle are discussed. Emphasis is placed on the regeneratively cooled thrust chamber of the engine. Tests were conducted to determine engine operating parameters during the start, shutdown, and restart. Characteristics of the integrated thrust chamber and the performance and thermal conditions for blowdown operation without supplementary boundary layer cooling were investigated. The results of the test program are presented.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-140250 , ASR74-229
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  • 72
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    Preparing oxidizer coated metal fuel particles (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A solid propellant composition of improved efficiency is described which includes an oxidizer containing ammonium perchlorate, and a powered metal fuel, preferably aluminum or beryllium, in the form of a composite. The metal fuel is contained in the crystalline lattice framework of the oxidizer, as well as within the oxidizer particles, and is disposed in the interstices between the oxidizer particles of the composition. The propellant composition is produced by a process comprising the crystallization of ammonium perchlorate in water, in the presence of finely divided aluminum or beryllium. A suitable binder is incorporated in the propellant composition to bind the individual particles of metal with the particles of oxidizer containing occluded metal.
    Keywords: PROPULSION SYSTEMS
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  • 73
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    Method and apparatus for decoding compatible convolutional codes (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: This invention relates to learning decoders for decoding compatible convolutional codes. The decoder decodes signals which have been encoded by a convolutional coder and allows performance near the theoretical limit of performance for coded data systems. The decoder includes a sub-bit shift register wherein the received sub-bits are entered after regeneration and shifted in synchronization with a clock signal recovered from the received sub-bit stream. The received sub-bits are processed by a sub-bit decision circuit, entered into a sub-bit shift register, decoded by a decision circuit, entered into a data shift register, and updated to reduce data errors. The bit decision circuit utilizes stored sub-bits and stored data bits to determine subsequent data-bits. Data errors are reduced by using at least one up-date circuit.
    Keywords: STRUCTURAL MECHANICS
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  • 74
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    Ultrasonic measurement of stress in railroad wheels and in long lengths of welded rail (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The failure of high speed emergency braking is discussed for railroad wheels and track. It is shown that high compressive residual stresses exist in the rims of new wheels which generate excessive heat, reducing the stress levels. Thermal stresses that build up in continuous lengths of welded track are reported and nondestructive methods of measuring stresses in thick steel are presented for identification, replacement, or adjustment before hazardous failures occur.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-X-64863
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  • 75
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    Evaluation of a metal shear web selectively reinforced with filamentary composites for space shuttle application (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A final program summary is reported for test and evaluation activities that were conducted for space shuttle web selection. Large scale advanced composite shear web components were tested and analyzed to evaluate application of advanced composite shear web construction to a space shuttle orbiter thrust structure. The shear web design concept consisted of a titanium-clad + or - 45 deg boron/epoxy web laminate stiffened with vertical boron-epoxy reinforced aluminum stiffeners and logitudinal aluminum stiffening. The design concept was evaluated to be efficient and practical for the application that was studied. Because of the effects of buckling deflections, a requirement is identified for shear buckling resistant design to maximize the efficiency of highly-loaded advanced composite shear webs.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-2409 , D180-17969-1
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  • 76
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    Extended temperature range ACPS thruster investigation (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The successful hot fire demonstration of a pulsing liquid hydrogen/liquid oxygen and gaseous hydrogen/liquid oxygen attitude control propulsion system thruster is described. The test was the result of research to develop a simple, lightweight, and high performance reaction control system without the traditional requirements for extensive periods of engine thermal conditioning, or the use of complex equipment to convert both liquid propellants to gas prior to delivery to the engine. Significant departures from conventional injector design practice were employed to achieve an operable design. The work discussed includes thermal and injector manifold priming analyses, subscale injector chilldown tests, and 168 full scale and 550 N (1250 lbF) rocket engine tests. Ignition experiments, at propellant temperatures ranging from cryogenic to ambient, led to the generation of a universal spark ignition system which can reliably ignite an engine when supplied with liquid, two phase, or gaseous propellants. Electrical power requirements for spark igniter are very low.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-134655
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  • 77
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    Space shuttle maneuvering engine reusable thrust chamber program. Task 11: Low Epsilon stability test plan (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The performance and heat transfer characteristics of a doublet element type injector for the space shuttle orbiter maneuvering engine thrust chamber were investigated. Ths stability characteristics were evaluated over a range of chamber pressures and mixture ratios. The specific objectives of the test were: (1) to determine whether stability has been influenced by injection of boundary layer coolant across the cavity entrance, (2) if the injector is stable, to determine the minimum cavity area required to maintain stability, and (3) if the injector is unstable, to determine the effects of entrance geometry and increased area on stability.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-134359 , ASR74-204
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  • 78
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    Advanced supersonic technology propulsion system study (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: This study had the objectives of determining the most promising conventional and variable cycle engine types; the effect of design cruise Mach number (2.2, 2.7 and 3.2) on a commercial supersonic transport; effect of advanced engine technology on the choice of engine cycle; and effect of utilizing hydrogen as the engine fuel. The technology required for the engines was defined, and the levels of development to ensure availability of this technology in advanced aircraft propulsion systems were assessed. No clearcut best conventional or variable cycle engine was identified. The dry bypass turbojet and the duct burning turbofans were initially selected as the best conventional engines, but later results, utilizing augmentation at takeoff, added the mixed-flow augmented turbofan as a promising contender. The modulating air flow, three-rotor variable cycle engine identified the performance features desired from VCE concepts (elimination of inlet drag and reduction in afterbody drag), but was a very heavy and complex engine.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-143634 , R74AEG330
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  • 79
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    Terminal-shock and restart control of a Mach 2.5, mixed compression inlet coupled to a turbofan engine (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Results of an experimental program conducted on a mixed-compression inlet coupled to a turbofan engine are presented. Open-loop frequency response data are presented that show the response of shock position (as measured by an average inlet static pressure) to sinusoidal airflow disturbances produced at the compressor face station. Also presented are results showing the effect of different passive terminations (a choke plate or a long duct) on the characteristics of the inlet. Transfer functions obtained by using experimental data are presented and compared to the experimental data. Closed-loop frequency response of shock position (with a proportional-plus-integral controller) is presented. In addition, transient data are presented that show the unstart-restart characteristics of the inlet.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-TM-X-3104 , E-7924
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  • 80
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    Digital communication system (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A digital communication system is reported for parallel operation of 16 or more transceiver units with the use of only four interconnecting wires. A remote synchronization circuit produces unit address control words sequentially in data frames of 16 words. Means are provided in each transceiver unit to decode calling signals and to transmit calling and data signals. The transceivers communicate with each other over one data line. The synchronization unit communicates the address control information to the transceiver units over an address line and further provides the timing information over a clock line. A reference voltage level or ground line completes the interconnecting four wire hookup.
    Keywords: STRUCTURAL MECHANICS
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  • 81
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    Coherent receiver employing nonlinear coherence detection for carrier tracking (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The concept of nonlinear coherence employed in carrier tracking to improve telecommunications efficiency is disclosed. A generic tracking loop for a coherent receiver is shown having seven principle feedback signals which may be selectively added and applied to a voltage controlled oscillator to produce a reference signal that is phase coherent with a received carrier. An eighth feedback signal whose nonrandom components are coherent with the phase detected and filtered carrier may also be added to exploit the sideband power of the received signal. A ninth feedback signal whose nonrandom components are also coherent with the quadrature phase detected and filtered carrier could be additionally or alternatively included in the composite feedback signal to the voltage controlled oscillator.
    Keywords: STRUCTURAL MECHANICS
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  • 82
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    On thermal stress failure of the SNAP-19A RTG heat shield (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Results of a study on thermal stress problems in an amorphous graphite heat shield that is part of the launch-abort protect system for the SNAP-19A radio-isotope thermoelectric generators (RTG) that will be used on the Viking Mars Lander are presended. The first result is from a thermal stress analysis of a full-scale RTG heat source that failed to survive a suborbital entry flight test, possibly due to thermal stress failure. It was calculated that the maximum stress in the heat shield was only 50 percent of the ultimate strength of the material. To provide information on the stress failure criterion used for this calculation, some heat shield specimens were fractured under abort entry conditions in a plasma arc facility. It was found that in regions free of stress concentrations the POCO graphite heat shield material did fracture when the local stress reached the ultimate uniaxial stress of the material.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-X-3097 , A-5516
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  • 83
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    Stress intensity factors for deep cracks emanating from the corner formed by a hole intersecting a plate surface (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A technique consisting of freezing photo-elasticity and a numerical method was used to obtain stress intensity factors for natural cracks emanating from the corner at which a hole intersects a plate surface. Geometries studied were: (1) crack depth to thickness ratios of approximately 0.2, (2) 0.5 and 0.75; (3) crack depth to crack length ratios of approximately 1.0 to 2.0; and (4) crack length to hole radius ratios of about 0.5 to 2.0. All final crack geometries were grown under monotonic loading and growth was not self similar, with most of the growth occuring through the thickness under remote extension. Stress intensity factors were determined at the intersection of the flaw border.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-132484 , VPI-E-74-1-REV
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  • 84
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    Application of a substructuring technique to the problem of crack extension and closure (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A substructuring technique, originally developed for the efficient reanalysis of structures, is incorporated into the methodology associated with the plastic analysis of structures. An existing finite-element computer program that accounts for elastic-plastic material behavior under cyclic loading was modified to account for changing kinematic constraint conditions - crack growth and intermittent contact of crack surfaces in two dimensional regions. Application of the analysis is presented for a problem of a centercrack panel to demonstrate the efficiency and accuracy of the technique.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-132458 , RE-480
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  • 85
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    Deformation characteristics and time-dependent notch sensitivity of Udimet 700 at intermediate temperatures (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Time dependent notch sensitivity was observed in Udimet 700 sheet, bar, and investment castings between 1000 and 1400 F (538 -760 C), but not at 1600 F (871 C). As was the case for modified Waspaloy, Waspaloy and Inconel 718, it occurred in notched specimens loaded below the yield strength when the creep deformation was localized. For each alloy and notched specimen geometry, a stress-average particle size zone can be defined that characterizes the notch sensitive behavior.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-134613 , REPT-043680-20-F
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  • 86
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    Analysis of wing-body interaction flutter for a preliminary space shuttle design (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Subsonic flutter analyses for a preliminary space shuttle design were performed to determine the effect of wing-body aerodynamic interaction on the vehicle flutter speed. It was found that the proximity of the large bodies of the shuttle to the wing reduces critical flutter speed by 11%. Aerodynamic reflection off the bodies is the dominant interaction effect while aerodynamic forces caused by body motion are of secondary importance in most cases. The analyses employed a doublet-lattice representation of the space shuttle, where in the wing and body surfaces were modeled by a lattice of nonplanar lifting surface elements. Axial singularities were introduced to account for body incidence, volume, and camber (slender body) effects. A series of studies on the placement and number of these elements was performed to ensure convergence of the results.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-2429
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  • 87
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    Analysis of complex elastic structures by a Rayleigh-Ritz component modes method using Lagrange multipliers (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The free vibrations of elastic structures of arbitrary complexity were analyzed in terms of their component modes. The method was based upon the use of the normal unconstrained modes of the components in a Rayleigh-Ritz analysis. The continuity conditions were enforced by means of Lagrange Multipliers. Examples of the structures considered are: (1) beams with nonuniform properties; (2) airplane structures with high or low aspect ratio lifting surface components; (3) the oblique wing airplane; and (4) plate structures. The method was also applied to the analysis of modal damping of linear elastic structures. Convergence of the method versus the number of modes per component and/or the number of components is discussed and compared to more conventional approaches, ad-hoc methods, and experimental results.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-138942 , AMS-1159
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  • 88
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    Analytic models of ducted turbomachinery tone noise sources. Volume 3: Program test case results (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Computer programs for analyzing the acoustic properties of turbomachinery with ducted flow were developed. The models include component interactions and rotor alone. Test case results determined from the computer programs are presented.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-132445 , D6-43296-3
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  • 89
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    Development of a short pulsed solid propellant plasma thruster (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The experimental results are summarized that were obtained in the development of a Teflon solid propellant pulsed plasma thruster. The feasibility was established of storing and feeding solid propellant in the form of an open circular loop into an operational thruster. This technique was verified to be practical by feeding over 20 inches of Teflon into a micro-thruster over an accumulated life test of 1858 hours. High energy density capacitors were evaluated under vacuum conditions when the capacitor is coupled directly to a plasma thruster. Numerous early capacitor failures were encountered. It was concluded that essentially all of the failures encountered in a vacuum environment are due to an internal electrical breakdown that will occur inside a capacitor that is not truly hermetically sealed. A steady input power significantly in excess of 130 watts can safely be tolerated if heat conduction can be provided to a sink whose temperature is about 16 C. A vacuum life test of the capacitor bank was carried out while discharging into a milli-lb. (milli-Newton) type pulsed plasma thruster. More than 1500 hours of vacuum testing of this milli-Newton type system has been accumulated without any capacitor problems. Recommendations are made for future capacitor designs.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-139272 , MS172R0001
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  • 90
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    Analytic models of ducted turbomachinery tone noise sources. Volume 2: Subprogram documentation (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Analytical models were developed for computing the periodic sound pressures of subsonic fans in an infinite hardwall annular duct with uniform flow. The computer programs are described which are used for numerical computations of sound pressure mode amplitudes. The data are applied to the acoustic properties of turbomachinery.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-132444 , D6-43296-2
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  • 91
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    Analytic models of ducted turbomachinery tone noise sources. Volume 1: Analysis (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The analytic models developed for computing the periodic sound pressure of subsonic fans and compressors in an infinite, hardwall annular duct with uniform flow are described. The basic sound-generating mechanism is the scattering into sound waves of velocity disturbances appearing to the rotor or stator blades as a series of harmonic gusts. The models include component interactions and rotor alone.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-132443 , D6-43296-1
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  • 92
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    Noise generated by quiet engine fans. 2: Fan A (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A significant effort within the NASA Quiet Engine Program has been devoted to acoustical evaluation at the Lewis Research Center noise test facility of a family of full-scale fans. This report, documents the noise results obtained with fan A - a 1.5-pressure-ratio, 1160-ft/sec-tip-speed fan. The fan is described and some aerodynamic operating data are given. Far-field noise around the fan was measured for a variety of configurations pertaining to acoustical treatment and over a range of operating conditions. Complete results of 1/3-octave band analysis of the data are presented in tabular form. Included also are power spectra and sideline perceived noise levels. Some representative 1/3-octave band data are presented graphically, and sample graphs of continuous narrow-band spectra are also provided.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-TM-X-3066 , E-7857
    Format: application/pdf
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  • 93
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    Instantaneous distortion in a Mach 2.5, 40-percent-internal-contraction inlet and its effect on turbojet stall margin (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An experimental wind tunnel investigation was conducted to determine the effects of time-variant distortions produced in a supersonic inlet on a J85-GE-13 turbojet engine. Results are presented principally in terms of instantaneous distortion amplitudes and total-pressure contours measured through compressor stall. They indicate that, although a time-averaged distortion may be far from a stall-inducing value, corresponding instantaneous distortion amplitudes can approach or exceed this value. Seven engine stall events were studied. In six of these events instantaneous distortion peaks of sufficient magnitude to cause stall were observed in the time period shortly before stall was detected.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-TM-X-3002 , E-6294
    Format: application/pdf
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  • 94
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    Erosion in radial inflow turbines. Volume 2: Balance of centrifugal and radial drag forces on erosive particles (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The particle motion in two-dimensional free and forced inward flowing vortices is considered. A particle in such a flow field experiences a balance between the aerodynamic drag forces that tend to drive erosive particles toward the axis, and centrifugal forces that prevent these particles from traveling toward the axis. Results predict that certain sizes of particles will achieve a stable orbit about the turbine axis in the inward flowing free vortex. In this condition, the radial drag force is equal to the centrifugal force. The sizes of particles that will achieve a stable orbit is shown to be related to the gas flow velocity diagram at a particular radius. A second analysis yields a description of particle sizes that will experience a centrifugal force that is greater than the radial component of the aerodynamic drag force for a more general type of particle motion.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-134616
    Format: application/pdf
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  • 95
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    Conceptual design studies of lift/cruise fans for military transports (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A study program for conceptual design studies of remote lift and lift/cruise fan systems to meet the requirements of military V/STOL aircraft was conducted. Parametric performance and design data are presented for fans covering a range of pressure ratios, including both single and two stage fan concepts. The gas generator selected for these fan systems was the J101-GE-100 engine. Noise generation and transient response were determined for selected fan systems.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-134636 , R74AEG283
    Format: application/pdf
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  • 96
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    Heat conduction controlled combustion for scramjet applications (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The use of heat conduction flame generated in a premixed supersonic stream is discussed. It is shown that the flame is controlled initially by heat conduction and then by chemical reaction. Such a flame is shorter than the diffusion type of flame and therefore it requires a much shorter burner. The mixing is obtained by injecting the hydrogen in the inlet. Then the inlet can be cooled by film cooling.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-132446
    Format: application/pdf
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  • 97
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    Rotation in vibration, optimization, and aeroelastic stability problems (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The effects of rotation in the areas of vibrations, dynamic stability, optimization, and aeroelasticity were studied. The governing equations of motion for the study of vibration and dynamic stability of a rapidly rotating deformable body were developed starting from the nonlinear theory of elasticity. Some common features such as the limitations of the classical theory of elasticity, the choice of axis system, the property of self-adjointness, the phenomenon of frequency splitting, shortcomings of stability methods as applied to gyroscopic systems, and the effect of internal and external damping on stability in gyroscopic systems are identified and discussed, and are then applied to three specific problems.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-138805
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  • 98
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    Computer programs for pressurization (RAMP) and pressurized expulsion from a cryogenic liquid propellant tank (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An analysis to predict the pressurant gas requirements for the discharge of cryogenic liquid propellants from storage tanks is presented, along with an algorithm and two computer programs. One program deals with the pressurization (ramp) phase of bringing the propellant tank up to its operating pressure. The method of analysis involves a numerical solution of the temperature and velocity functions for the tank ullage at a discrete set of points in time and space. The input requirements of the program are the initial ullage conditions, the initial temperature and pressure of the pressurant gas, and the time for the expulsion or the ramp. Computations are performed which determine the heat transfer between the ullage gas and the tank wall. Heat transfer to the liquid interface and to the hardware components may be included in the analysis. The program output includes predictions of mass of pressurant required, total energy transfer, and wall and ullage temperatures. The analysis, the algorithm, a complete description of input and output, and the FORTRAN 4 program listings are presented. Sample cases are included to illustrate use of the programs.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-TN-D-7504 , E-7654
    Format: application/pdf
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  • 99
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    The hard start phenomena in hypergolic engines. Volume 2: Combustion characteristics of propellants and propellant combinations (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The combustion characteristics of hypergolic propellants are described. A research project was conducted to determine if the reaction control system engine propellants on Apollo spacecraft undergo explosive reaction when subjected to conditions present in the engine at the time of ignition. Combustion characteristics pertinent to the hard-start phenomenon are considered. The thermal stability of frozen mixtures of hydrazine-based fuels with nitrogen tetroxide was analyzed. Results of the tests are presented in the form of tables and graphs.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-134314 , BM-IR-1646-VOL-2
    Format: application/pdf
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  • 100
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    Economic effects of propulsion system technology on existing and future transport aircraft (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The results of an airline study of the economic effects of propulsion system technology on current and future transport aircraft are presented. This report represents the results of a detailed study of propulsion system operating economics. The study has four major parts: (1) a detailed analysis of current propulsion system maintenance with respect to the material and labor costs encountered versus years in service and the design characteristics of the major elements of the propulsion system of the B707, b727, and B747. (2) an analysis of the economic impact of a future representative 1979 propulsion system is presented with emphasis on depreciation of investment, fuel costs and maintenance costs developed on the basis of the analysis of the historical trends observed. (3) recommendations concerning improved methods of forecasting the maintenance cost of future propulsion systems are presented. A detailed method based on the summation of the projected labor and material repair costs for each major engine module and its installation along with a shorter form suitable for quick, less detailed analysis are presented, and (4) recommendations concerning areas where additional technology is needed to improve the economics of future commercial propulsion systems are presented along with the suggested economic benefits available from such advanced technology efforts.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-134645
    Format: application/pdf
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