Search NASA⌕ Search

SEARCH · Search NASA

Results for “structures testing”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 973 records · Page 54
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Two Point Exponential Approximation Method for structural optimization of problems with frequency constraints

The point exponential approximation method was introduced by Fadel et al. (Fadel, 1990), and tested on structural optimization problems with stress and displacement constraints. The reports in earlier papers were promising, and the method, which consists of correcting Taylor series approximations using previous design history, is tested in this paper on optimization problems with frequency constraints. The aim of the research is to verify the robustness and speed of convergence of the two point exponential approximation method when highly non-linear constraints are used.

Fadel, G. M.↗
NASA NTRS1991

YBa2Cu3O(7-x)/Au/Nb device structures

Fabrication and testing of planar and edge geometry YBaCuO/Au/Nb superconductor/normal-metal/superconductor (SNS) device structures is described. Weak-link devices of this type serve as sensitive probes of the electrical quality of the YBaCuO/Au interface. The devices are fabricated using laser-ablated, in situ, c-axis-oriented YBaCuO thin films, with both annealed and unannealed YBaCuO/Au interfaces. The planar SNS structures are formed by sequential, in situ deposition of YBaCuO, Au, and Nb, followed by etching, planarization, and wiring electrode definition to produce junctions ranging from 5 to 20 micron on a side. Resulting RnA products are 1-10 x 10 to the -8th ohm-sq cm with critical current densities up to 5 kA/sq cm. For the edge geometry devices, the YBaCuO film edges are patterned using Ar ion milling, followed by a low energy ion cleaning step and in situ deposition of Au and Nb. Devices with areas in the 10 to the -7th to 10 to the -8th sq cm range have been fabricated with RnA products lower than 10 to the -8th ohm-sq cm and critical current densities up to 3kA/sq cm. Both types of devices show ac Josephson steps under microwave irradiation. The best results have been obtained with annealed YBaCuO/Au interfaces.

Hunt, B. D.↗
NASA NTRS1994

Fabrication and Testing of a Large Primary Reflector Structure

This paper discusses the fabrication considerations and proposed testing concepts related to a large twelve meter, graphite-epoxy space truss that is being developed to provide support of the primary mirror system for the Beam Transmission Optical System (BTOS).

space truss primary reflector free electron laser ↗
NASA NTRS1989

Remote Attitude Measurement Sensor (RAMS)

Remote attitude measurement sensor (RAMS) offers a low-cost, low-risk, proven design concept that is based on mature, demonstrated space sensor technology. The electronic design concepts and interpolation algorithms were tested and proven in space hardware like th Retroreflector Field Tracker and various star trackers. The RAMS concept is versatile and has broad applicability to both ground testing and spacecraft needs. It is ideal for use as a precision laboratory sensor for structural dynamics testing. It requires very little set-up or preparation time and the output data is immediately usable without integration or extensive analysis efforts. For on-orbit use, RAMS rivals any other type of dynamic structural sensor (accelerometer, lidar, photogrammetric techniques, etc.) for overall performance, reliability, suitability, and cost. Widespread acceptance and extensive usage of RAMS will occur only after some interested agency, such as OAST, adopts the RAMS concept and provides the funding support necessary for further development and implementation of RAMS for a specific program.

Davis, H. W.↗
NASA NTRS1991

Using adaptive structures to enable future missions by relaxing ground test requirements

Future NASA missions will require large space structures that must maintain accurate surface tolerances for up to 20 years; most flight programs require a ground test verification of the hardware. Because of the influence of gravity, the current state-of-the-art ground test technology cannot accurately determine whether the hardware complies with the requirements. The incorporation of adaptive structures into the spacecraft will enable a relaxation of the ground test requirements necessary to validate the hardware for flight. This paper describes the challenges in testing large precision structures, adaptive structures, the data establishing the current state of the art in ground testing, and the utilization of adaptive structures to alleviate the ground test requirements.

Wada, Ben K.↗
NASA NTRS1985

Simulation studies for surfaces and materials strength

From intermolecular force studies, it is now known that the overall non-additive contribution to the lattice enegy is positive so that analysis based on only pairwise additivity suggests a shallower intermolecular potential than the true value. Two body contributions alone are also known to be categorically unable to even qualitatively describe some configurations of molecular clusters in the gas phase or the general relaxation and reconstruction of fcc crystal surfaces. In addition, the many-body contribution was shown to play a key role in the stability of certain crystal structures. In these recent analyses, a relatively simple potential energy function (PEF), comprising only a two-body Mie-type potential plus a three-body Axilrod-Teller-type potential, was found to be extremely effective. This same parametric PEF is applied to describe the bulk stability and surface energy for the diamond cubic structure. To test the stability condition, the FCC, BCC, diamond cubic, graphite and beta-tin structures were considered.

Halicioglu, T.↗
NASA NTRS1989

Space Station Freedom - Accommodation for technology R&D

The paper examines the features of the accommodation equipment designed for the candidate technology payloads of the Space Station, which include magnetic plasma thruster systems and a hypothetical advanced electromagnetic propulsion system utilizing high-temperature superconductivity materials. The review of the accommodation-equipment concepts supports the assumption that some propulsion technologies can be tested on the Space Station while being attached externally to the station's truss structure. For testing technologies with inherent operation or performance hazards, space platforms and smaller free-flyers coordinated with the Space Station can be used. Diagrams illustrating typical accommodation equipment configurations are included.

Holt, Alan C.↗
NASA NTRS1993

(abstract) Overview of NASA's Adaptive Structures Program

NASA's research program in Adaptive Structures was initiated seven years ago to provide the technology required for large (20-50 meters in dimension) precision (submicron) structures for observations from space. The current approach of designing thermally stable passive structures cannot meet the requirements and moreover the systems cannot be validated by ground tests. Adaptive Structures provides the capability to adjust the quasistatic dimensions of the structures, preload joints, add active damping, and provide the actuation forces necessary to attenuate the undesired dynamic motions. The technology is applicable to space platforms with various pointing instruments as well as for microspacecraft. This technology has been incorporated as part of a small Active Fold Mirror on the Wide Field Planetary Camera to be flown within the year to correct the optical errors in the Hubble Telescope. Highlights of NASA's Adaptive Structures research and applications will be presented along with future technology and research requirements for both small inexpensive spacecraft and large precision systems.

adaptive↗
NASA NTRS2011

Temperature Effects on Adhesive Bond Strengths and Modulus for Commonly Used Spacecraft Structural Adhesives

A study was performed to observe how changes in temperature and substrate material affected the strength and modulus of an adhesive bondline. Seven different adhesives commonly used in aerospace bonded structures were tested. Aluminum, titanium and Invar adherends were cleaned and primed, then bonded using the manufacturer's recommendations. Following surface preparation, the coupons were bonded with the adhesives. The single lap shear coupons were then pull tested per ASTM D 1002 Standard Test Method for Apparent Shear Strength of Single- Lap-Joint over a temperature range from -150 deg C up to +150 deg C. The ultimate strength was calculated and the resulting data were converted into B-basis design allowables. Average and Bbasis results were compared. Results obtained using aluminum adherends are reported. The effects of using different adherend materials and temperature were also studied and will be reported in a subsequent paper. Dynamic Mechanical Analysis (DMA) was used to study variations in adhesive modulus with temperature. This work resulted in a highly useful database for comparing adhesive performance over a wide range of temperatures, and has facilitated selection of the appropriate adhesive for spacecraft structure applications.

structural adhesives testing↗
NASA NTRS1983

Dynamic assessment of B-52B-008 carrier aircraft for the revised Space Shuttle solid rocket booster decelerator subsystem drop test vehicle

The structural integrity of B-52B-008, pylon, and hooks for the drop test missions was determined by theoretical analysis. The results of the analysis and conclusions are presented in this document. The major modification to the drop test vehicle was shortening it about 54 inches, which resulted in the forward hook attach structure being located at the base of the nosecone. The shims that are located in the aft hook structures are increased from two inches to three inches. Airspeed, aerodynamic configuration, and load charts are included.

Doty, L. J.↗
NASA NTRS2015

Approach for Structurally Clearing an Adaptive Compliant Trailing Edge Flap for Flight

The Adaptive Compliant Trailing Edge (ACTE) flap was flown on the National Aeronautics and Space Administration (NASA) Gulfstream GIII testbed at the NASA Armstrong Flight Research Center. This smoothly curving flap replaced the existing Fowler flaps creating a seamless control surface. This compliant structure, developed by FlexSys Inc. in partnership with the Air Force Research Laboratory, supported NASA objectives for airframe structural noise reduction, aerodynamic efficiency, and wing weight reduction through gust load alleviation. A thorough structures airworthiness approach was developed to move this project safely to flight. A combination of industry and NASA standard practice require various structural analyses, ground testing, and health monitoring techniques for showing an airworthy structure. This paper provides an overview of compliant structures design, the structural ground testing leading up to flight, and the flight envelope expansion and monitoring strategy. Flight data will be presented, and lessons learned along the way will be highlighted.

flight test↗
NASA NTRS1967

Ballpoint probe gives optimum results in ultrasonic testing

Ballpoint-type ultrasonic probe assembly focuses its beam precisely on the bond lines of a composite thin face sheet structure when testing for bond integrity. It can scan in any direction, and eliminate external couplant spray.

Melton, R. E.↗
NASA NTRS1984

Electro-impulse deicing - Structural dynamic studies, icing tunnel tests and applications

This paper contains a discussion of the comparison of analytical and experimental results of the dynamic response of a flat rectangular plate subjected to electro-impulse type deicing forces. Early attempts in this correlation have been hampered by the complex leading edge geometries of the airfoils tested to date. The lack of a suitable analytical model for a typical leading edge structure has prompted these preliminary investigations of simple geometries, beginning with a flat plate and to be followed by a semi-cylindrical leading edge representation. The comparisons reported herein are thus limited to rectangular plate models. Project plans and icing tunnel results are given.

Bernhart, W. D.↗
NASA NTRS2011

Test-Anchored Vibration Response Predictions for an Acoustically Energized Curved Orthogrid Panel with Mounted Components

rich body of vibroacoustic test data was recently generated at Marshall Space Flight Center for component-loaded curved orthogrid panels typical of launch vehicle skin structures. The test data were used to anchor computational predictions of a variety of spatially distributed responses including acceleration, strain and component interface force. Transfer functions relating the responses to the input pressure field were generated from finite element based modal solutions and test-derived damping estimates. A diffuse acoustic field model was applied to correlate the measured input sound pressures across the energized panel. This application quantifies the ability to quickly and accurately predict a variety of responses to acoustically energized skin panels with mounted components. Favorable comparisons between the measured and predicted responses were established. The validated models were used to examine vibration response sensitivities to relevant modeling parameters such as pressure patch density, mesh density, weight of the mounted component and model form. Convergence metrics include spectral densities and cumulative root-mean squared (RMS) functions for acceleration, velocity, displacement, strain and interface force. Minimum frequencies for response convergence were established as well as recommendations for modeling techniques, particularly in the early stages of a component design when accurate structural vibration requirements are needed relatively quickly. The results were compared with long-established guidelines for modeling accuracy of component-loaded panels. A theoretical basis for the Response/Pressure Transfer Function (RPTF) approach provides insight into trends observed in the response predictions and confirmed in the test data. The software developed for the RPTF method allows easy replacement of the diffuse acoustic field with other pressure fields such as a turbulent boundary layer (TBL) model suitable for vehicle ascent. Structural responses using a TBL model were demonstrated, and wind tunnel tests have been proposed to anchor the predictions and provide new insight into modeling approaches for this environment. Finally, design load factors were developed from the measured and predicted responses and compared with those derived from traditional techniques such as historical Mass Acceleration Curves and Barrett scaling methods for acreage and component-loaded panels.

Frady, Gregory P.↗
NASA NTRS1983

Static and damage tolerance tests of an advanced composite vertical fin for L-1011 aircraft

This paper recounts the significant events which took place during the structural verification testing of two graphite/epoxy material, full-size vertical stabilizers. The ground test articles were tested to a high bending dynamic lateral gust condition. The first unit failed during static testing at 98 percent Design Ultimate Load. Failure began within the front spar cap. A detailed review of the failure was performed to identify all possible modes. This review resulted in a 'production line' type fix being designed for incorporation in the second ground test article prior to installation in the test fixture. The modified second unit sustained 106 percent of Design Ultimate Load without incident. One lifetime (36,000 flights) of damage tolerance testing was accomplished with the specimen purposely damaged at five locations. A fail-safe loading was performed successfully after simulating lightning strike damage to the fin box cover. A large area repair was substantiated by completing a second lifetime of spectrum loadings. The residual static strength was determined to be 119.7 percent of Design Ultimate Load.

Dorward, F.↗
NASA NTRS2014

Mechanism Design and Testing of a Self-Deploying Structure Using Flexible Composite Tape Springs

The detailed mechanical design of a novel deployable support structure that positions and tensions a membrane optic for space imagining applications is presented. This is a complex three-dimensional deployment using freely deploying rollable composite tape spring booms that become load bearing structural members at full deployment. The deployment tests successfully demonstrate a new architecture based on rolled and freely deployed composite tape spring members that achieve simultaneous deployment without mechanical synchronization. Proper design of the flexible component mounting interface and constraint systems, which were critical in achieving a functioning unit, are described. These flexible composite components have much potential for advancing the state of the art in deployable structures, but have yet to be widely adopted. This paper demonstrates the feasibility and advantages of implementing flexible composite components, including the design details on how to integrate with required traditional mechanisms.

Footdale, Joseph N.↗