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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Test and Analysis Correlation of Standard and Hybrid Standard/Thin-ply Composite Notched Test Specimens

Hybrid composite laminates, a combination of standard-and thin-ply layers, are structurally efficient and can offer opportunities for weight savings over composite laminates composed of only standard-thickness plies. Three hybrid laminates and three standard laminates were tested and analyzed to provide a baseline comparison for not only weight savings and strength benefits of the hybrid stacking sequences, but also to provide fidelity for progressive failure modeling techniques using the two different laminate designs. The standard and hybrid composite specimens were designed to have the same thickness and in-plane stiffness properties, as closely as possible, and were loaded with axial tension and axial compression. Small notched specimens were tested under compression and tension loading, and larger intermediate specimens were tested under tension loading, only. The finite element modeling represented the as-designed panel dimensions as well as the real-life testing conditions through various boundary conditions. The progressive failure modeling and analysis technique described, exhibited very good correlation with the hybrid test specimens, and therefore is appropriate for use in future investigations into more appealing stacking sequences. The progressive failure modeling can also be used to determine the proper usage of thin-ply materials in order to determine the most ideal strength benefits over their standard-ply counterparts.

Alana Zahn↗
NASA NTRS1974

On correlation analysis of the Explorer 12 substorm protons with some geophysical parameters

The intensity of Explorer-12 substorm protons with energies above 140 keV observed in the far outer belt are compared with several commonly used geomagnetic indices. The parameters considered in the correlation include Davis and Sugiura's (1966) AE index that provides a measure of the magnitude of substorm intensity, the asymmetric ring-current index R(DS) that is obtained from nine low-latitude stations, Sugiura and Hendricks' (1967) Dst index representing the symmetric component of the ring current, and the planetary magnetic index Kp.

Su, S.-Y.↗
NASA NTRS1976

Closure and ratio correlation analysis of lunar chemical and grain size data

Major element and major element plus trace element analyses were selected from the lunar data base for Apollo 11, 12 and 15 basalt and regolith samples. Summary statistics for each of the six data sets were compiled, and the effects of closure on the Pearson product moment correlation coefficient were investigated using the Chayes and Kruskal approximation procedure. In general, there are two types of closure effects evident in these data sets: negative correlations of intermediate size which are solely the result of closure, and correlations of small absolute value which depart significantly from their expected closure correlations which are of intermediate size. It is shown that a positive closure correlation will arise only when the product of the coefficients of variation is very small (less than 0.01 for most data sets) and, in general, trace elements in the lunar data sets exhibit relatively large coefficients of variation.

Butler, J. C.↗
NASA NTRS2006

SRG110 Stirling Generator Dynamic Simulator Vibration Test Results and Analysis Correlation

The U.S. Department of Energy (DOE), Lockheed Martin (LM), and NASA Glenn Research Center (GRC) have been developing the Stirling Radioisotope Generator (SRG110) for use as a power system for space science missions. The launch environment enveloping potential missions results in a random input spectrum that is significantly higher than historical RPS launch levels and is a challenge for designers. Analysis presented in prior work predicted that tailoring the compliance at the generator-spacecraft interface reduced the dynamic response of the system thereby allowing higher launch load input levels and expanding the range of potential generator missions. To confirm analytical predictions, a dynamic simulator representing the generator structure, Stirling convertors and heat sources was designed and built for testing with and without a compliant interface. Finite element analysis was performed to guide the generator simulator and compliant interface design so that test modes and frequencies were representative of the SRG110 generator. This paper presents the dynamic simulator design, the test setup and methodology, test article modes and frequencies and dynamic responses, and post-test analysis results. With the compliant interface, component responses to an input environment exceeding the SRG110 qualification level spectrum were all within design allowables. Post-test analysis included finite element model tuning to match test frequencies and random response analysis using the test input spectrum. Analytical results were in good overall agreement with the test results and confirmed previous predictions that the SRG110 power system may be considered for a broad range of potential missions, including those with demanding launch environments.

Suarez, Vicente J.↗
NASA NTRS2007

SRG110 Stirling Generator Dynamic Simulator Vibration Test Results and Analysis Correlation

The U.S. Department of Energy (DOE), Lockheed Martin (LM), and NASA Glenn Research Center (GRC) have been developing the Stirling Radioisotope Generator (SRG110) for use as a power system for space science missions. The launch environment enveloping potential missions results in a random input spectrum that is significantly higher than historical radioisotope power system (RPS) launch levels and is a challenge for designers. Analysis presented in prior work predicted that tailoring the compliance at the generator-spacecraft interface reduced the dynamic response of the system thereby allowing higher launch load input levels and expanding the range of potential generator missions. To confirm analytical predictions, a dynamic simulator representing the generator structure, Stirling convertors and heat sources were designed and built for testing with and without a compliant interface. Finite element analysis was performed to guide the generator simulator and compliant interface design so that test modes and frequencies were representative of the SRG110 generator. This paper presents the dynamic simulator design, the test setup and methodology, test article modes and frequencies and dynamic responses, and post-test analysis results. With the compliant interface, component responses to an input environment exceeding the SRG110 qualification level spectrum were all within design allowables. Post-test analysis included finite element model tuning to match test frequencies and random response analysis using the test input spectrum. Analytical results were in good overall agreement with the test results and confirmed previous predictions that the SRG110 power system may be considered for a broad range of potential missions, including those with demanding launch environments.

Lewandowski, Edward J.↗
NASA NTRS1976

Thematic mapper studies band correlation analysis

Spectral data representative of thematic mapper candidate bands 1 and 3 to 7 were obtained by selecting appropriate combinations of bands from the JSC 24 channel multispectral scanner. Of all the bands assigned, only candidate bands 4 (.74 mu to .80 mu) and 5 (.80 mu to .91 mu) showed consistently high intercorrelation from region to region and time to time. This extremely high correlation persisted when looking at the composite data set in a multitemporal, multilocation domain. The GISS investigations lend positive confirmation to the hypothesis, that TM bands 4 and 5 are redundant.

Ungar, S. G.↗
NASA NTRS2008

Test-Analysis Correlation for Space Shuttle External Tank Foam Impacting RCC Wing Leading Edge Component Panels

The Space Shuttle Columbia Accident Investigation Board recommended that NASA develop, validate, and maintain a modeling tool capable of predicting the damage threshold for debris impacts on the Space Shuttle Reinforced Carbon-Carbon (RCC) wing leading edge and nosecap assembly. The results presented in this paper are one part of a multi-level approach that supported the development of the predictive tool used to recertify the shuttle for flight following the Columbia Accident. The assessment of predictive capability was largely based on test analysis comparisons for simpler component structures. This paper provides comparisons of finite element simulations with test data for external tank foam debris impacts onto 6-in. square RCC flat panels. Both quantitative displacement and qualitative damage assessment correlations are provided. The comparisons show good agreement and provided the Space Shuttle Program with confidence in the predictive tool.

Lyle, Karen H.↗
NASA NTRS2002

Correlative Analysis of Behavioral and Physiological Concomitants of Labor in Pregnant Rats

During parturition, rats exhibit characteristic behavioral expressions of labor. Lordosis contractions, consisting of an elongation of the dams body, are observed beginning several hours prior to neonate births, whereas vertical contractions, repeated rapid lifts of the abdomen, occur immediately preceding the birth of each neonate. We analyzed underlying changes in intrauterine pressure (IUP) using a telemetric sensor that we modified for use in freely-moving rats. This technique enabled us to correlate behavioral expressions of labor contractions with IUP. A small telemetric blood pressure sensor was fitted within a fluid-filled balloon, similar in size to a full term rat fetus. On Gestational day 19 of the rats' 22-day pregnancy, a unit was surgically implanted within the uterus. The dams were simultaneously videotaped, enabling us to directly correlate IUP signals with behavioral expressions of labor contractions. Earlier phases of labor, consisting predominantly of lordosis contractions were characterized by lower pressures relative to later phases during which higher pressures and vertical contractions were frequently observed.

Baer, L. A.↗
NASA NTRS1986

Statistical correlation analysis for comparing vibration data from test and analysis

A theory was developed to compare vibration modes obtained by NASTRAN analysis with those obtained experimentally. Because many more analytical modes can be obtained than experimental modes, the analytical set was treated as expansion functions for putting both sources in comparative form. The dimensional symmetry was developed for three general cases: nonsymmetric whole model compared with a nonsymmetric whole structural test, symmetric analytical portion compared with a symmetric experimental portion, and analytical symmetric portion with a whole experimental test. The theory was coded and a statistical correlation program was installed as a utility. The theory is established with small classical structures.

Butler, T. G.↗
NASA NTRS1986

Comparison of medium frequency pulsed radar interferometer and correlation analysis winds, part 1

In principle, the interferometer analysis determines the radial velocity and direction of single scatterers provided that each has a sufficiently different Doppler frequency to permit separation by spectral analysis. In fact, scatterers will not have constant radial velocity, and their Doppler frequencies as well as their directions will be modulated by their horizontal motion. Thus, there is a tradeoff between the poorer resolution but less smeared scatterers on shorter records and the higher resolution (longer) records. Three or more non-collinear scatterers are sufficient to determine the wind. It appears that the velocity found from the combined interferometer peaks agrees well with the apparent velocity from correlation methods, but the true velocity is a factor of 2 smaller. This difference might be resolved by searching for scatters showing regular movement between adjacent records.

Meek, C. E.↗
NASA NTRS2001

Cross-Correlation Analysis of UV Profile Variations and Nonradial Pulsations in Be Stars

This study is an investigation of the role of photospheric nonradial pulsations in the mass loss processes of Be stars. Some 18 Be stars were the focus of intensive, multi-wavelength campaigns between 1985 and 1996 with the NASA/ESA International Ultraviolet Explorer Satellite (IUE) . The campaigns were designed to monitor variations in the UV flux and stellar wind lines with near simultaneous, high signal-to-noise, optical spectroscopy of photospheric lines. The high quality, ground-based spectra were required to record the subtle, blue-to-red moving bump patterns in spectral line profiles that result from nonradial pulsations. We found that the same fine variations in the UV photospheric lines can be extracted from noisy IUE spectra by cross-correlating each target spectrum with a narrow-lined standard spectrum. Time series analyses of the cross-correlation functions then reveal the periodic signals, amplitudes, phases, and modal identifications of the pulsations. Our goals are to compare such results from UV and optical time series in order to model the stellar photospheric temperature and velocity fluctuations, and to search for correlated UV wind line variations to determine whether there is a connection between pulsation and mass loss.

Gies, Douglas R.↗
NASA NTRS2017

Buckling Test Results and Preliminary Test and Analysis Correlation from the 8-Foot-Diameter Orthogrid-Stiffened Cylinder Test Article TA02

Results from the testing of cylinder test article SBKF-P2-CYL-TA02 (referred to herein as TA02) are presented. TA02 is an 8-foot-diameter (96-inches), 78.0-inch-long, aluminum-lithium (Al-Li), orthogrid-stiffened cylindrical shell similar to those used in current state-of-the-art launch-vehicle structures and was designed to exhibit global buckling when subjected to combined compression and bending loads. The testing was conducted at the Marshall Space Flight Center (MSFC), February 3-6, 2009, in support of the Shell Buckling Knockdown Factor Project (SBKF). The test was used to verify the performance of a newly constructed buckling test facility at MSFC and to verify the test article design and analysis approach used by the SBKF researchers.

Hilburger, Mark W.↗
NASA NTRS2009

Correlative Analysis of GRBs Detected by Swift and Suzaku- WAM

It is now well known that a complete understanding of the energetics of the prompt phase of gamma-ray bursts (GRBs) requires full knowledge of the spectrum, extending at least as high as the peak energy (Epeak) of the vF(v) spectrum. Since most gamma-ray bursts (GRBs) have Epeak above the energy range (15-150 keV) of the Burst Alert Telescope (BAT) on Swift, a full understanding of the prompt emission from Swift GRBs requires spectral fits over as broad an energy range as possible. This can be completed for bursts which are simultaneously detected by Swift BAT and the Suzaku Wide-band All-Sky Monitor (WAM), which covers the energy range from 50-5000 keV. Between the launch of Suzaku in July 2005 and the end of 2008, there were 44 gamma-ray bursts (GRBs) which triggered both Swift and WAM and an additional 41 bursts which triggered Swift and were detected by WAM, but did not trigger. A joint BAT-WAM team has cross-calibrated the two instruments using GRBs, and we are now able to perform joint fits on these bursts to determine spectral parameters including Epeak. The results of broad spectral fits allows us to understand the distribution of Epeak for Swift bursts and to calibrate Epeak estimators when Epeak is within the BAT energy range. For those bursts with spectroscopic redshifts, we can calculate the isotropic energy and study various correlations between Epeak and other global burst parameters. Here we present the results of joint Swift/BAT-Suzaku/WAM spectral fits for 77 of the bursts jointly detected by the two instruments. We show that the distribution of spectral fit parameters is consistent with distributions from earlier missions and confirm that Swift bursts are consistent with earlier reported relationships between Epeak and isotropic energy. We show through time-resolved spectroscopy that individual burst pulses are also consistent with this relationship.

Krimm, H.A.↗
NASA NTRS1975

Cross-correlative analysis of S-193 data for terrain characteristics

The author has identified the following significant results. The impulse response technique, when coupled with fine resolution altimeter data, is capable of yielding: (1) very fine mean ground elevation resolution; (2) slopes and slope variation along the altimeter path; (3) the absorption or the ground vegetation cover density for a given weather condition; and (4) an eventual classification of ground cover and/or moisture content of the ground.

Hayre, H. S.↗
NASA NTRS1985

Test and analysis correlation for structural dynamic systems

Activities in modifying a structural mathematical model to correlate with its modal test results are summarized. Results from the Viking and Galileo spacecraft, and developments in the parameter estimation of structural mathematical models of large flexible structures using multiple boundary condition tests are presented.

Wada, B. K.↗