Search NASA⌕ Search

SEARCH · Search NASA

Results for “substructuring”

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 1,153 records · Page 64
All sourcesNASA NTRSDOE OSTI
DOE OSTI2010

Contact Versus Non-Contact Measurement of a Helicopter Main Rotor Composite Blade

The dynamic characterization of lightweight structures is particularly complex as the impact of the weight of sensors and instrumentation (cables, mounting of exciters...) can distort the results. Varying mass loading or constraint effects between partial measurements may determine several errors on the final conclusions. Frequency shifts can lead to erroneous interpretations of the dynamics parameters. Typically these errors remain limited to a few percent. Inconsistent data sets however can result in major processing errors, with all related consequences towards applications based on the consistency assumption, such as global modal parameter identification, model-based damage detection and FRF-based matrix inversion in substructuring, load identification and transfer path analysis [1]. This paper addresses the subject of accuracy in the context of the measurement of the dynamic properties of a particular lightweight structure. It presents a comprehensive comparative study between the use of accelerometer, laser vibrometer (scanning LDV) and PU-probe (acoustic particle velocity and pressure) measurements to measure the structural responses, with as final aim the comparison of modal model quality assessment. The object of the investigation is a composite material blade from the main rotor of a helicopter. The presented results are part of an extensive test campaign performed with application of SIMO, MIMO, random and harmonic excitation, and the use of the mentioned contact and non-contact measurement techniques. The advantages and disadvantages of the applied instrumentation are discussed. Presented are real-life measurement problems related to the different set up conditions. Finally an analysis of estimated models is made in view of assessing the applicability of the various measurement approaches for successful fault detection based on modal parameters observation as well as in uncertain non-deterministic numerical model updating.

36 MATERIALS SCIENCE↗
DOE OSTI2010

Radio Signal Constraints on Galactic Dark Matter Annihilation

Annihilation of Dark Matter usually produces together with gamma rays comparable amounts of electrons and positrons. The e{sup +}e{sup -} gyrating in the galactic magnetic field then produce secondary synchrotron radiation which thus provides an indirect mean to constrain the DM signal itself. To this purpose, we calculate the radio emission from the galactic halo as well as from its expected substructures and we then compare it with the measured diffuse radio background. We employ a multi-frequency approach using data in the relevant frequency range 100 MHz-100 GHz, as well as the WMAP Haze data at 23 GHz. The derived constraints are of the order <{sigma}{sub A}{sup v}> = 10{sup -24} cm{sup 3}s{sup -1} for a DM mass m{sub {kappa}}= 100 GeV even though sensibly depending on the astrophysical uncertainties.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Spiral-like structure in the core of nearby galaxy clusters

Not surprisingly, with the very high angular resolution of the Chandra telescope, results revealed fairly complex structures in cluster cores to be more common than expected. In particular, understanding the nature of spiral-like features at the center of some clusters is the major motivation of this work. We present results from Chandra deep observations of 15 nearby galaxy clusters (0.01<z<0.06). Using X-ray temperature and substructure maps, we detect a plume-like feature in the core of 7 clusters: A85, A426, A496, Hydra A, Centaurus, A1644 and Ophiuchus. Comparing our results to numerical simulations, our investigation lends support to the fact that these patterns are due to nonzero impact parameter mergers.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2010

Scalar response of the nucleon, chiral symmetry and nuclear matter properties

In this talk we present a description of nuclear binding in a chiral approach based on the existence of a chiral invariant scalar field associated with the generation of the masses through spontaneous chiral symmetry breaking. We discuss the emergence of such a field on the example of the NJL model. We also incorporate the effect of confinement at the level of the nucleon substructure to stabilize nuclear matter. In a particular quark-diquark model we illustrate the simutaneous influences of spontaneous chiral symmetry breaking and confinement on the nucleon mass and on the nuclear matter description.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

The dislocation density and twin-boundary frequency determined by X-ray peak profile analysis in cold rolled magnetron-sputter deposited nanotwinned copper

The dislocation density and the average twin boundary frequency is determined quantitatively in as-deposited and cold-rolled nanotwinned Cu thin films by high-resolution X-ray line profile analysis. After cold-rolling the dislocation density increases considerably, whereas the twin boundary frequency decreases only slightly. The physical parameters of the substructure provided by the quantitative X-ray analysis are in agreement with earlier transmission electron microscopy observations. The flow stress of the as-deposited and the cold-rolled films is directly correlated with the average thickness of twin lamellae and the dislocation density by taking into account the Hall-Petch and Taylor type strengthening mechanisms.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Renormalization of one meson exchange potentials and their currents

The Nucleon-Nucleon One Meson Exchange Potential, its wave functions and related Meson Exchange Currents are analyzed for point-like nucleons. The leading N{sub c} contributions generate a local and energy independent potential which presents 1/r{sup 3} singularities, requiring renormalization. We show how invoking suitable boundary conditions, neutron-proton phase shifts and deuteron properties become largely insensitive to the nucleon substructure and to the vector mesons. Actually, reasonable agreement with low energy data for realistic values of the coupling constants (e.g. SU(3) values) is found. The analysis along similar lines for the Meson Exchange Currents suggests that this renormalization scheme implies tremendous simplifications while complying with exact gauge invariance at any stage of the calculation.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Test of QCD in multijet final states at the Tevatron

In this contribution, some of the recent QCD results on jet production from the CDF and D0 experiments in Run II of the Tevatron are discussed. In particular, results include cross section measurements for dijet and trijet production, study of jet substructure and measurements of W/Z+jets cross sections. The measurements are compared with the theoretical predictions.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2012

Searching for particle physics beyond the standard model at the LHC and elsewhere

Following a general introduction to open questions beyond the Standard Model, the prospects for addressing them in the new era opened up by the LHC are reviewed. Sample highlights are given of ways in which the LHC is already probing beyond previous experiments, including the searches for supersymmetry, quark and gluon substructure and microscopic black holes.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

The ethyl radical in superfluid helium nanodroplets: Rovibrational spectroscopy and ab initio computations

The ethyl radical has been isolated and spectroscopically characterized in 4He nanodroplets. The band origins of the five CH stretch fundamentals are shifted by < 2 cm –1 from those reported for the gas phase species. The symmetric CH 2 stretching band (v 1 ) is rotationally resolved, revealing nuclear spin statistical weights predicted by G 12 permutation-inversion group theory. A permanent electric dipole moment of 0.28 (2) D is obtained via the Stark spectrum of the v 1 band. The four other CH stretch fundamental bands are significantly broadened in He droplets and lack rotational fine structure. This broadening is attributed to symmetry dependent vibration-to-vibration relaxation facilitated by the He droplet environment. In addition to the five fundamentals, three a 1 ' overtone/combination bands are observed, and each of these have resolved rotational substructure. As a result, these are assigned to the 2v 12 , v 4 + v 6 , and 2v 6 bands through comparisons to anharmonic frequency computations at the CCSD(T)/cc-pVTZ level of theory.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Infrared laser spectroscopy of the helium-solvated allyl and allyl peroxy radicals

Infrared spectra in the C–H stretch region are reported for the allyl (CH 2 CHCH 2 ) and allyl peroxy (CH 2 =CH–CH 2 OO·) radicals solvated in superfluid helium nanodroplets. Nine bands in the spectrum of the allyl radical have resolved rotational substructure. We have assigned three of these to the ν 1 (a 1 ), ν 3 (a 1 ), and ν 13 (b 2 ) C–H stretch bands and four others to the ν 14 /(ν 15 +2ν 11 ) (b 2 ) and ν 2 /(ν 4 +2ν 11 ) (a 1 ) Fermi dyads, and an unassigned resonant polyad is observed in the vicinity of the ν 1 band. Experimental coupling constants associated with Fermi dyads are consistent with quartic force constants obtained from density functional theory computations. The peroxy radical was formed within the He droplet via the reaction between allyl and O 2 following the sequential pick-up of the reactants. Five stable conformers are predicted for the allyl peroxy radical, and a computed two-dimensional potential surface for rotation about the CC–OO and CC–CO bonds reveals multiple isomerization barriers greater than ≈300 cm –1 . Furthermore, the C–H stretch infrared spectrum is consistent with the presence of a single conformer following the allyl + O 2 reaction within helium droplets.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Generation and structure of extremely large clusters in pulsed jets

Extremely large xenon clusters with sizes exceeding the predictions of the Hagena scaling law by several orders of magnitude are shown to be produced in pulsed gas jets. The cluster sizes are determined using single-shot single-particle imaging experiments with short-wavelength light pulses from the free-electron laser in Hamburg (FLASH). Scanning the time delay between the pulsed cluster source and the intense femtosecond x-ray pulses first shows a main plateau with size distributions in line with the scaling laws, which is followed by an after-pulse of giant clusters. For the extremely large clusters with radii of several hundred nanometers the x-ray scattering patterns indicate a grainy substructure of the particles, suggesting that they grow by cluster coagulation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Investigation of features of plastic deformation and fracture of fine-crystalline V-4Ti-4Cr alloy

With the use of transmission electron microscopy the investigation of defect substructure was carried out in the V-4Ti-4Cr-(C, N, O) alloy with disperse strengthening (by nanoparticles of oxy-carbo-nitride phase) after deformation by active tension at temperatures of 20 and 800 °C. It has been shown that an important feature of plastic deformation is deformation localization with crystal lattice reorientation.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Analysis of structure and phase composition of rails subjected to differential hardening at different regimes

Differential hardening of rails by compressed air in different regimes is accompanied by formation of morphologically different structure, being formed according to the diffusion mechanism of γ↔α transformation and consisting of grains of lamellar pearlite, free ferrite and grains of ferrite-carbide mixture. By methods of transmission electron microscopy the layer by layer analysis of differentially hardened rails has been carried out, the quantitative parameters of the structure, phase composition and dislocation substructure have been established and their comparison has been made for different regimes of hardening. It has been found that the structure-phase states being formed have gradient character, defined by the hardening regime, direction of study from the surface of rolling and by depth of location of layer under study.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Braids as a representation space of SU(5)

The standard model of particle physics provides very accurate predictions of phenomena occurring at the sub-atomic level, but the reason for the choice of symmetry group and the large number of particles considered elementary is still unknown. Along the lines of previous preon models positing a substructure to explain these aspects, Bilson-Thompson showed how the first family of elementary particles is realized as the crossings of braids made of three strands, with charges resulting from twists of those strands with certain conditions; in this topological model, there are only two distinct neutrino states. Modeling the particles as braids implies these braids must be the representation space of a Lie algebra, giving the symmetries of the standard model. In this paper, this representation is made explicit, obtaining the raising operators associated with the Lie algebra of SU(5), one of the earliest grand unified theories. Because the braids form a group, the action of these operators are braids themselves, leading to their identification as gauge bosons. Possible choices for the other two families are also given. Although this realization of particles as braids is lacking a dynamical framework, it is very suggestive, especially when considered as a natural method of adding matter to loop quantum gravity.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Structure-phase states evolution in Al-Si alloy under electron-beam treatment and high-cycle fatigue

By methods of scanning and transmission electron diffraction microscopy the analysis of structure-phase states and defect substructure of silumin subjected to high-intensity electron beam irradiation in various regimes and subsequent fatigue loading up to failure was carried out. It is revealed that the sources of fatigue microcracks are silicon plates of micron and submicron size are not soluble in electron beam processing. The possible reasons of the silumin fatigue life increase under electron-beam treatment are discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Structure-phase states evolution in rails during a long operation

By methods of scanning and transmission electron microscopy the transformation regularities of structure-phase states, defect substructure, fracture surface of rail surface layer up to 10 mm deep in process of long-term operation (passed tonnage of gross weight 1000 mln tons) were revealed. It has been shown that the surface layer ∼20 μm in thickness has a multiphase, submicro- and nanocrystalline structure and it contains micropores and microcracks. The increased density of bend extinction contours at 2 mm depth from the tread contact surface was noted. The analysis of structure morphological constituents and internal stress fields, created by intra- and interphase boundaries after long operation was carried out. It was shown that the maximum amplitude of stress fields was formed on the interphase boundary the globular cementite particle–matrix. The evaluation of stress fields was done.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Electron microscopic investigation of crystal lattice bending-torsion and internal stresses in deformed polycrystalline alloys

Generalization of the results of electron microscopy investigations of the crystal lattice bending-torsion (χ) and the internal stresses (IS) was conducted. The deformed polycrystalline alloys and steels were investigated. The sources of χ and IS origin were established. The regularities of their change with the distance from the sources and the evolution with deformation were revealed. The contribution of IS into the deformation resistance was determined. The nature of formation of two sequences of dislocation substructure transformations during deformation of alloys was established.

36 MATERIALS SCIENCE↗