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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Dynamic load capacities of graphite fiber: Polyimide composites in oscillating plain bearings to 340 C (650 F)

Load capacities were determined for plain spherical bearings with self-lubricating spherical elements of graphite-fiber-reinforced-polyimide, and for plain cylindrical bearings with thin-wall liners of the composite in the bearing bores. Composites consisted of a 1-to-1 weight ratio of graphite fibers and polyimide. Oscillation was at an amplitude of + or - 15 deg at a frequency of 1 hertz. Bearings with composite ball material had a load capacity of approximately 69 MN/sq m (10 000 psi) at room temperature 25 MN/sq m (3600 psi) at 340 C (650 F). Bearings with thin-wall composite liners had much higher load capacities of 280 MN/sq m (40 000 psi) at room temperature amd 240 MN/sq m (35 000 psi) at 320 C (600 F). Friction coefficients were in the range of 0.12 to 0.19. The addition of 10 wt.% graphite fluoride solid lubricant to the composition of the thin-wall liners reduced friction coefficients into the range of 0.10 to 0.12.

Sliney, H. E.↗
NASA NTRS1977

Dynamic load attenuator

Instrument consists of special bolt head that cuts material from splined washer. Required shear and tensile forces absorb kinetic energy. Cut-away material is retained by shearing action, making device useful where production of loose metal particles is not acceptable.

Crum, P. N.↗
NASA NTRS1975

SSME-HAS dynamic load simulators

The space shuttle main engine propellant valve actuators (SSME) were designed to simulate the loads reflected into the SSME by the chamber coolant valve, the fuel preburner, and the oxidizer. The design, and functional description are included along with a list of the drawings. The load fixture control transform, friction torque, and flow calculations are reported.

Source record↗
NASA NTRS1976

Digital data processing system dynamic loading analysis

Simulation and analysis of the Space Shuttle Orbiter Digital Data Processing System (DDPS) are reported. The mated flight and postseparation flight phases of the space shuttle's approach and landing test configuration were modeled utilizing the Information Management System Interpretative Model (IMSIM) in a computerized simulation modeling of the ALT hardware, software, and workload. System requirements simulated for the ALT configuration were defined. Sensitivity analyses determined areas of potential data flow problems in DDPS operation. Based on the defined system requirements and the sensitivity analyses, a test design is described for adapting, parameterizing, and executing the IMSIM. Varying load and stress conditions for the model execution are given. The analyses of the computer simulation runs were documented as results, conclusions, and recommendations for DDPS improvements.

Lagas, J. J.↗
NASA NTRS1977

Comparison of computer codes for calculating dynamic loads in wind turbines

Seven computer codes for analyzing performance and loads in large, horizontal axis wind turbines were used to calculate blade bending moment loads for two operational conditions of the 100 kW Mod-0 wind turbine. Results were compared with test data on the basis of cyclic loads, peak loads, and harmonic contents. Four of the seven codes include rotor-tower interaction and three were limited to rotor analysis. With a few exceptions, all calculated loads were within 25 percent of nominal test data.

Spera, D. A.↗
NASA NTRS1977

Comparison of computer codes for calculating dynamic loads in wind turbines

Seven computer codes for analyzing performance and loads in large, horizontal-axis wind turbines were used to calculate blade bending moment loads for two operational conditions of the 100 kW Mod-O wind turbine. Results are compared with test data on the basis of cyclic loads, peak loads, and harmonic contents. Four of the seven codes include rotor-tower interaction and three are limited to rotor analysis. With a few exceptions, all calculated loads were within 25% of nominal test data.

Spera, D. A.↗
NASA NTRS1982

Dynamic load measurements with delta wings undergoing self-induced roll-oscillations

The aerodynamic forces acting on a delta wing, mounted on a free-to-roll sting-balance apparatus, were measured. Two wing planforms having leading edge sweeps of 76 and 80 deg were tested, but only the wing with the 80 deg sweep would undergo periodic self-induced roll oscillation. The time dependent forces and roll angles for this wing were then recorded for various test conditions. In these tests a considerable drop in the average normal force of the free-to-roll wing was measured, relative to the normal force obtained in the static tests. Also, the helium-bubble flow visualization technique was used to gain some insight into the periodic motion of the separated leading edge vortices.

Levin, D.↗
NASA NTRS1984

Effect of vortex generators on the power conversion performance and structural dynamic loads of the Mod-2 wind turbine

Applying vortex generators from 20 to 100 percent span of the Mod-2 rotor resulted in a projected increase in annual energy capture of 20 percent and reduced the wind speed at which rated power is reached by nearly 3 m/sec. Application of vortex generators from 20 to 70 percent span, the fixed portion of the Mod-2 rotor, resulted in a projected increase in annual energy capture of about half this. This improved performance came at the cost of a small increase in cyclic blade loads in below rated power conditions. Cyclic blade loads were found to correlate well with the change in wind speed during one rotor revolution.

Sullivan, T. L.↗
NASA NTRS1986

Efficient identification of critical stresses in structures subject to dynamic loads

Optimum structural design problems generally employ constraints which are parametric in terms of space and time variables. A parametric constraint may be replaced by equivalent critical point constraints at its local minima for optimization applications. In complex structures, accurate identification of such critical points is computationally expensive due to the cost of finite element analyses. Three techniques are described for efficiently and accurately identifying critical points for space- and time-dependent parametric constraints. An adaptive search technique and a spline interpolation technique are developed for exactly known response. A least squares spline approximation is suggested for noisy behavior. A helicopter tail-boom structure subjected to transient loading is used as an example to demonstrate the techniques described. All three techniques are shown to be computationally efficient for critical point identification and the least squares approximation also removes noise from the data. The case of multiple constraints per element is shown to be particularly suited to the use of spline techniques.

Haftka, R. T.↗
NASA NTRS1987

An Application of Retroduction to Analyzing and Testing the Backing off of Nuts and Bolts During Dynamic Loading

The method of retroduction, adapted from the doctoral thesis of Dr. A. Croce, relies on a process of dialectic questioning that begins with the information sought, proceeds to Given items (either in the form of dimensions or limits of research). and to Known mathematical forms of analysis in design or to principles of study in research. Finally, analysis and synthesis are used to abstract the dielectic questions and to arrive at the information desired. This method is used to solve the engineering design problem of a beam and to determine why bolts and nuts vibrate apart. Both mathematical analysis and dialectic logical analysis are utilized. Results are provided of tests conducted to check the retroductive study of why and how nuts back off.

Kerley, James J.↗
NASA NTRS1986

Dynamic loads on twin jet exhaust nozzles due to shock noise

Acoustic near field data were collected with model single and twin jet nozzles to determine if closely spaced nozzles produce higher acoustic loading than do single nozzles. The tests were spurred by structural failure of the B-1 exhaust nozzle external flaps and similar damage on the F-15. The test was performed using two 5/8 in. ID pipes machined and placed side-by-side to mimic B-1 nozzles. A microphone mounted on the internozzle fairing measured acoustic levels near the nozzle exit plane. The nozzles oscillated significantly more than did a single nozzle over a wide range of nozzle pressure ratios. Acoustic levels in the dual jets exceeded single jet noise by as much as 20 dB, making acoustic resonance a definite candidate for structural damage in the twin jet configuration.

Norum, T. D.↗
NASA NTRS1987

Initial dynamic load estimates during configuration design

This analysis includes the structural response to shock and vibration and evaluates the maximum deflections and material stresses and the potential for the occurrence of elastic instability, fatigue and fracture. The required computations are often performed by means of finite element analysis (FEA) computer programs in which the structure is simulated by a finite element model which may contain thousands of elements. The formulation of a finite element model can be time consuming, and substantial additional modeling effort may be necessary if the structure requires significant changes after initial analysis. Rapid methods for obtaining rough estimates of the structural response to shock and vibration are presented for the purpose of providing guidance during the initial mechanical design configuration stage.

Schiff, Daniel↗