SEARCH · Engineering Papers

Results for “GaGe”

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.

SourceResearch connectionFrom yearThrough year

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

At least 1,261 records · Page 70

All sources NASA NTRS DOE OSTI

NASA NTRS1986

Short fatigue cracks in notched aluminum specimens

The short-crack fatigue behavior in notched specimens of Al 2024-T3 was studied at values of the stress ratio, R, equal to 0.5, 0.0, -1.0, and -2.0. Crack growth was monitored using a replica technique for cracks ranging in length from a few tens of a micron to the specimen's thickness (2.3 mm). Crack opening displacement was measured for surface cracks as short as 0.035 mm using the interferometric strain/displacement gage, a laser-based optical technique described by Sharpe (1982). It was found that the growth rates of short cracks were faster than the rates of long cracks for R values of -1.0 and -2.0. No significant difference was observed for R = 0.0, and at R = 0.5, the short cracks actually grew more slowly that the long ones. At all R values, the closure stresses measured for short cracks were smaller than those predicted for large cracks.

Lee, J. J.↗

NASA NTRS1986

Crash response data system for the controlled impact demonstration (CID) of a full scale transport aircraft

NASA Langley's Crash Response Data System (CRDS) which is designed to acquire aircraft structural and anthropomorphic dummy responses during the full-scale transport CID test is described. Included in the discussion are the system design approach, details on key instrumentation subsystems and operations, overall instrumentation crash performance, and data recovery results. Two autonomous high-environment digital flight instrumentation systems, DAS 1 and DAS 2, were employed to obtain research data from various strain gage, accelerometer, and tensiometric sensors installed in the B-720 test aircraft. The CRDS successfully acquired 343 out of 352 measurements of dynamic crash data.

Calloway, Raymond S.↗

NASA NTRS1987

Rate effects on delamiantion fracture toughness of a toughened graphite/epoxy

The objective of this study was to determine the effects of loading rate on interlaminar fracture toughness of T300/F-185 graphite/epoxy composite, having an elastomer-modified epoxy resin matrix. Mode I interlaminar fracture was investigated by means of uniform width and width-tapered double cantilever beam (DCB) specimens. Hinged tabs were used to insure unrestrained rotation at the free ends. Specimens were loaded at quasi-static deflection rates of up to 8.5 mm/s corresponding to crack extension rates of up to 21 mm/s. Crack extension was monitored by means of strain gages mounted on the surface of the specimen. Continuous records were obtained of load, deflection, and crack extension for determination of the strain energy release rate. The latter was calculated by means of the area method and beam analysis method, and expressed as a power law of the crack extension velocity. Results indicate that the strain energy release rate decreases with crack velocity by over 20 percent over three decades of crack velocity.

Daniel, Isaac M.↗

NASA NTRS1987

Impact response of composite fuselage frames

Graphite-epoxy frames were drop tested onto a concrete floor to simulate crash loadings. The frames have Z-shaped cross sections typical of designs often proposed for fuselage structure of advanced composite transports. A diameter of six feet for the frames was chosen to reduce specimen fabrication costs and to facilitate testing. Accelerometer, strain gage, and photographic measurements are presented which characterize the impact behavior of frames with differing masses to represent structural or seat/occupant masses. Failures of the graphite-epoxy frames involved complete separations through the cross section. All damage to the lightly loaded composite frames was confined to an area close to the impact point. Subsequent failures left and right of the impact point occurred for the more heavily loaded specimens.

Boitnott, Richard L.↗

NASA NTRS1987

Determination of calibration constants for the hole-drilling residual stress measurement technique applied to orthotropic composites. I - Theoretical considerations

The hole-drilling technique for the measurement of residual stresses using electrical resistance strain gages has been widely used for isotropic materials and has been adopted by the ASTM as a standard method. For thin isotropic plates, with a hole drilled through the thickness, the idealized hole-drilling calibration constants are obtained by making use of the well-known Kirsch's solution. In this paper, an analogous attempt is made to theoretically determine the three idealized hole-drilling calibration constants for thin orthotropic materials by employing Savin's (1961) complex stress function approach.

Prasad, C. B.↗

NASA NTRS1987

Results of an interlaboratory fatigue test program conducted on alloy 800H at room and elevated temperatures

The experimental approach adopted for low cycle fatigue tests of alloy 800H involved the use of electrohydraulic test systems, hour glass geometry specimens, diametral extensometers, and axial strain computers. Attempts to identify possible problem areas were complicated by the lack of reliable data for the heat of Alloy 800H under investigation. The method adopted was to generate definitive test data in an Interlaboratory Fatigue Test Program. The laboratories participating in the program were Argonne National Laboratory, Battelle Columbus, Mar-Test, and NASA Lewis. Fatigue tests were conducted on both solid and turbular specimens at temperatures of 20, 593, and 760 C and strain ranges of 2.0, 1.0, and 0.5 percent. The subject test method can, under certain circumstances, produce fatigue data which are serious in error. This approach subsequently was abandoned at General Atomic Company in favor of parallel gage length specimens and axial extensometers.

Ellis, J. R.↗

NASA NTRS1986

Mechanical properties characterization of composite sandwich materials intended for space antenna applications

The composite materials proposed for use in the Advanced Communications Technology Satellite (ACTS) Program contains a new, high modulus graphite fiber as the reinforcement. A study was conducted to measure certain mechanical properties of the new fiber-reinforced material as well as of a composite-faced aluminum honeycomb sandwich structure. Properties were measured at -157, 22, and 121 C. Complete characterization of this material was not intended. Longitudinal tensile, picture-frame shear, short-beam shear, and flexural tests were performed on specimens of the composite face-sheet materials. Unidirectional, cross-plied, and quasi-isotropic fiber composite ply layup designs were fabricated and tested. These designs had been studied by using NASA's Integrated Composite Analyzer (ICAN) computer program. Flexural tests were conducted on (+/- 60/0 deg) sub s composite-faced sandwich structure material. Resistance strain gages were used to measure strains in the tensile, picture-frame, and sandwich flexural tests. The sandwich flexural strength was limited by the core strength at -157 and 22 C. The adhesive bond strength was the limiting factor at 121 C. Adhesive mechanical properties are reflected in sandwich structure flexural properties when the span-to-depth ratio is great enough to allow a significant shear effect on the load-deflection behavior of the sandwich beam. Most measured properties agreed satisfactorily with the properties predicted by ICAN.

Bowles, Kenneth J.↗

NASA NTRS1987

Ultrasonic characterization of the nonlinear elastic properties of unidirectional graphite/epoxy composites

The theoretical treatment of linear and nonlinear elasticity in a unidirectionally fiber reinforced composite as well as measurements for a unidirectional graphite/epoxy composite (T300/5208) are presented. Linear elastic properties were measured by both ultrasonic and strain gage measurements. The nonlinear properties were determined by measuring changes in ultrasonic natural phase velocity with a pulsed phase locked loop interferometer as a function of stress and temperature. These measurements provide the basis for further investigations into the relationship between nonlinear elastic properties and other important properties such as strength and fiber-matrix interfacial stength in graphite/epoxy composites.

Prosser, William H.↗

NASA NTRS1987

Structural frequency functions for an impulsive, distributed forcing function

The response of a penetrator structure to a spatially distributed mechanical impulse with a magnitude approaching field test force levels (1-2 Mlb) were measured. The frequency response function calculated from the response to this unique forcing function is compared to frequency response functions calculated from response to point forces of about 2000 pounds. The results show that the strain gages installed on the penetrator case respond similiarly to a point, axial force and to a spatially distributed, axial force. This result suggests that the distributed axial force generated in a penetration event may be reconstructed as a point axial force when the penetrator behaves in linear manner.

Bateman, Vesta I.↗

NASA NTRS1988

Design of the primary pre-TRMM and TRMM ground truth site

The primary objective of the Tropical Rain Measuring Mission (TRMM) were to: integrate the rain gage measurements with radar measurements of rainfall using the KSFC/Patrick digitized radar and associated rainfall network; delineate the major rain bearing systems over Florida using the Weather Service reported radar/rainfall distributions; combine the integrated measurements with the delineated rain bearing systems; use the results of the combined measurements and delineated rain bearing systems to represent patterns of rainfall which actually exist and contribute significantly to the rainfall to test sampling strategies and based on the results of these analyses decide upon the ground truth network; and complete the design begun in Phase 1 of a multi-scale (space and time) surface observing precipitation network centered upon KSFC. Work accomplished and in progress is discussed.

Garstang, Michael↗

NASA NTRS1988

Quick actuating closure and handling system

A quick activating closure and handling system, which utilizes conical sections for locking, was developed to allow quick access to the combustor internal components of the 8 ft High Temperature Tunnel. These critical components include the existing methane spraybar, a transpiration cooled nozzle and the new liquid oxygen (LOX) injection system housed within the combustor. A substantial cost savings will be realized once the mechanism is installed since it will substantially reduce the access time and increase the time available for conducting wind tunnel tests. A need exists for more frequent inspections when the wind tunnel operates at the more severe conditions generated by using LOX in the combustor. A loads analysis and a structural (finite element) analysis were conducted to verify that the new closure system is compatible with the existing pressure shell. In addition, strain gages were placed on the pressure vessel to verify how the pressure shell reacts to transient pressure loads. A scale model of the new closure system was built to verify the operation of the conical sections in the locking mechanisms.

Allred, Johnny W.↗

NASA NTRS1988

Experimental Vibration Damping Characteristics of the Third-stage Rotor of a Three-stage Transonic Axial-flow Compressor

Rotor blade aerodynamic damping is experimentally determined in a three-stage transonic axial flow compressor having design aerodynamic performance goals of 4.5:1 pressure ratio and 65.5 lbm/sec weight flow. The combined damping associated with each mode is determined by a least squares fit of a single degree of freedom system transfer function to the nonsynchronous portion of the rotor blade strain gage output power spectra. The combined damping consists of the aerodynamic damping and the structural and mechanical damping. The aerodynamic damping varies linearly with the inlet total pressure for a given corrected speed, weight flow, and pressure ratio while the structural and mechanical damping is assumed to remain constant. The combined damping is determined at three inlet total pressure levels to obtain the aerodynamic damping. The third-stage rotor blade aerodynamic damping is presented and discussed for the design equivalent speed with the stator blades reset for maximum efficiency. The compressor overall preformance and experimental Campbell diagrams for the third-stage rotor blade row are also presented.

Newman, Frederick A.↗

NASA NTRS1988

An Experimental and Analytical Evaluation of a Biaxial Test for Determining Shear Properties of Composite Materials

The results of an experimental and analytical investigation of a biaxial tension/compression test for determining shear properties of composite materials are reported. Using finite element models of isotropic and orthotropic laminates, a specimen geometry was optimized. A kinematic fixture was designed to introduce an equal and opposite pair of forces into a specimen with a one inch square test section. Aluminum and several composite laminates with the optimized geometry and a configuration with large stress gradients were tested in the fixture. The specimens were instrumented with strain gages in the center of the test section for shear stiffness measurements. Pure shear strain was measured. The results from the experiments correlated well with finite element results. Failure of the specimens occurred through the center of the test section and appeared to have initiated at the high stress points. The results lead to the conclusion that the optimized specimen is suitable for determining shear modulus for composite materials. Further revisions to the specimen geometry are necessary if the method is to give shear strength data.

Kennedy, John M.↗

NASA NTRS1986

Optimal output fast feedback in two-time scale control of flexible arms

Control of lightweight flexible arms moving along predefined paths can be successfully synthesized on the basis of a two-time scale approach. A model following control can be designed for the reduced order slow subsystem. The fast subsystem is a linear system in which the slow variables act as parameters. The flexible fast variables which model the deflections of the arm along the trajectory can be sensed through strain gage measurements. For full state feedback design the derivatives of the deflections need to be estimated. The main contribution of this work is the design of an output feedback controller which includes a fixed order dynamic compensator, based on a recent convergent numerical algorithm for calculating LQ optimal gains. The design procedure is tested by means of simulation results for the one link flexible arm prototype in the laboratory.

Siciliano, B.↗

NASA NTRS1987

Lift distributions for a 3-dimensional steady blade-vortex interaction

The interaction of a horizontally mounted V23010-1.58 semispan airfoil (simulating a helicopter rotor blade) with a tip vortex shed by a vertically mounted upstream vortex-generating wing (VGW) is investigated experimentally at 60 m/s (dynamic pressure 2.2 kPa, Reynolds number 850,000, and Mach number 0.17) in the NASA Ames 7 x 10-ft wind tunnel. The velocity field near the blade is determined using a three-dimensional zoom LDV; the spanwise lift distribution is measured by strain gages; and the results are compared with the predictions of the panel computer code VSAERO (Maskew, 1982) in graphs. Features noted include localized loss of lift due to the presence of residual VGW wake, loss of lift far inboard on the blade (indicating the large domain of VGW vorticity), little change in total lift with variations in vortex strength, and good agreement between VSAERO and experiment in overall lift distribution but not in all geometric variations).

Dunagan, Stephen E.↗

NASA NTRS1987

Atmospheric trends in methylchloroform and the global average for the hydroxyl radical

ALE-GAGE (Atmospheric Lifetime Experiment-Global Atmospheric Gases Experiment) data obtained over the seven-year period from July 1978 to June 1985 are presented and interpreted. The data, combined with knowledge of industrial emissions, are used in an optimal estimation inversion scheme to deduce a globally average methylchloroform atmospheric lifetime of 6.3(+ 1.2, - 0.9) years (1 sigma uncertainty) and a globally averaged tropospheric hydroxyl radical concentration of (7.7 + or - 1.4) x 10 to the 5th radicals/cu cm (1 sigma uncertainty). These results provide the most accurate estimates yet of the trends and lifetime of methylchloroform and of the global average for tropospheric hydroxyl radical levels.

Prinn, R.↗

NASA NTRS1987

The applicability of satellite altimetry data to tidal models

The characteristics of satellite altimetry data are reviewed, and techniques for incorporating them into numerical tide models are discussed. The relationship between the geocentric tides observed by satellites and the ocean tides measured by gages or predicted by models is explored, and particular attention is given to the differences between deep-water, shelf, and estuarine tidal regimes. It is concluded that a separate tidal solution should always be performed before assimilating satellite data, including calculation of the tides along a single repeated ground track in the case of shelf and estuarine regions. The potential value of the altimetry to be provided by Topex/Poseidon (scheduled launch in 1991) is indicated.

Parke, Michael E.↗

NASA NTRS1988

Application of intelligent systems to wind tunnel test facilities

An approach to the application of intelligent-systems technology to the wind tunnel facilities at NASA Ames Research Center is outlined. To help fulfill the long-range goals of improving data quality and increasing personnel efficiency and management effectiveness, three major areas of intelligent systems application are recommended. The available state-of-the-art technology for developing the proposed systems is reviewed including the application of commercial software packages. The initial tasks and effort to develop these systems are recommended. A prototype expert system for selection of internal strain-gage balances has been built and is presented herein as an example model for the future systems.

Lo, Ching F.↗