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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Delocalization and stretch-bend mixing of the HOH bend in liquid water

Liquid water’s rich sub-picosecond vibrational dynamics arise from the interplay of different high- and low-frequency modes evolving in a strong yet fluctuating hydrogen bond network. Recent studies of the OH stretching excitations of H 2 O indicate that they are delocalized over several molecules, raising questions about whether the bending vibrations are similarly delocalized. In this paper, we take advantage of an improved 50 fs time-resolution and broadband infrared (IR) spectroscopy to interrogate the 2D IR lineshape and spectral dynamics of the HOH bending vibration of liquid H2O. Indications of strong bend-stretch coupling are observed in early time 2D IR spectra through a broad excited state absorption that extends from 1500 cm -1 to beyond 1900 cm -1 , which corresponds to transitions from the bend to the bend overtone and OH stretching band between 3150 and 3550 cm -1 . Pump-probe measurements reveal a fast 180 fs vibrational relaxation time, which results in a hot-ground state spectrum that is the same as observed for water IR excitation at any other frequency. The fastest dynamical time scale is 80 fs for the polarization anisotropy decay, providing evidence for the delocalized or excitonic character of the bend. Finally, normal mode analysis conducted on water clusters extracted from molecular dynamics simulations corroborate significant stretch-bend mixing and indicate delocalization of δ HOH on 2-7 water molecules.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1995

Bend Properties of Sapphire Fibers at Elevated Temperatures: Bend Survivability - 1

The effect of temperature on the bend radius that a c-axis-oriented sapphire fiber can withstand was determined for fibers of various diameter. Bend stress rupture tests were performed for times of 1-100 h and temperatures of 300-1700 C. Fibers would survive the bend test undeformed, would fracture or would deform. The bend survival radius was determined to be the radius above which no fibers fractured or deformed for a given time-temperature treatment. It was found that the ability of fibers to withstand curvature decreases substantially with time and increasing temperature and that fibers of smaller diameter (46-83 micron) withstood smaller bend radii than would be expected from just a difference in fiber diameter when compared with the bend results of the fibers of large diameter (144 micron). This was probably due to different flaw populations, causing high temperature bend failure for the tested sapphire fibers of different diameters.

Morscher, Gregory N.↗
DOE OSTI2016

Conceptual design of front ends for the advanced photon source multi-bend achromats upgrade

The proposed Advanced Photon Source (APS) upgrade from a double-bend achromats (DBA) to multi-bend achromats (MBA) lattice with ring energy change from 7 GeV to 6 GeV and beam current from 100 mA to 200 mA poses new challenges for front ends. All front ends must be upgraded to fulfill the following requirements: 1) handle the high heat load from two insertion devices in either inline or canted configuration, 2) include a clearing magnet in the front end to deflect and dump any electrons in case the electrons escape from the storage ring during swap-out injection with the safety shutters open, 3) incorporate the next generation x-ray beam position monitors (XBPMs) into the front end to meet the new stringent beam stability requirements. This paper presents the evaluation of the existing APS front ends and standardizes the insertion device (ID) front ends into two types: one for the single beam and one for the canted beams. The conceptual design of high heat load front end (HHLFE) and canted undulator front end (CUFE) for APS MBA upgrade is presented.

43 PARTICLE ACCELERATORS↗
DOE OSTI2018

Upper limit for the effect of elastic bending stress on the saturation magnetization of L a 0.8 S r 0.2 Mn O 3

In this study, using polarized neutron reflectometry, we measured the influence of elastic bending stress on the magnetization depth profile of a La 0.8 Sr 0.2 MnO 3 (LSMO) epitaxial film grown on a SrTiO 3 substrate. The elastic bending strain of ±0.03% has no obvious effect on the magnetization depth profile at saturation. This result is in stark contrast to that of (La 1-x Pr x )1-yCayMnO 3 (LPCMO) films for which strain of ±0.01% produced dramatic changes in the magnetization profile and Curie temperature. We attribute the difference between the influence of strain on the saturation magnetization in LSMO (weak or none) and LPCMO (strong) to a difference in the ability of LSMO (weak or none) and LPCMO (strong) to phase separate. Our observation provides an upper limit of tuning LSMO saturation magnetization via elastic strain effect.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Electrical bending actuation of gold-films with nanotextured surfaces

An actuating material system comprising a gold-film with nanotextured surface was fabricated. Using electroless gold plating onto a substrate of porous anodized aluminum oxide, a thin film of gold with a high density of short gold nanofibers on its surface was made. When one end of such a film was connected to an ion generator, bending was achieved upon electrical charging in air. Experiments showed that the free end of an 8 mm film could be displaced by more than 1.6 mm with a bending strain of 0.08%. In contrast with other types of thin-film artificial muscle materials, the present Au-film did not require any electrolyte to function. With the relatively easy fabrication method, this nanotextured film shows promising actuation behavior in air. Actuation systems based on a number of mechanisms have been developed in the last few decades, including electric, ionic, photonic, pneumatic, and thermal. As discussed in detail in Madden et al. and Brochu and Pei,11 the weaknesses of these materials include bulkiness, low stress or strain generation, low strain rate, long response time, short cycle life, and low energy efficiency. Recent developments have involved the possibilities to use the unique properties of nanostructures to produce actuation, such as in nanostructured carbon, nanoporous gold or platinum, V 2 O 5 nanofibre sheet, electroactive nanostructured polymers, hybrid carbon nanotube yarn, niobium nanowire yarn, and anodized aluminum oxide (AAO). Here, we introduce a nanostructured material system comprising a gold film with a high density of short gold-nanofibers attached to one side, which can bend to produce a large displacement (~1.6 mm) upon electrical charging through an ion generator. In addition to the displacement, the functionality without the need of an electrolyte is another advantage for using this material system as actuators. We discuss the fabrication and characterization methods, the morphology, and the actuating properties of this system here. To achieve a metal film with a nanotextured surface, electroless gold-plating was performed on substrates of AAO with a characteristic nano-honeycomb structure consisting of >10 10 pores per cm 2 . The fabrication of the AAO substrates followed the procedures described in Cheng and Ngan. The anodization condition for the AAO was 40 V against graphite electrode in saturated oxalic acid at 18 °C for 2 h. The pore diameter observed was 50 ± 5 nm. By using an electroless gold-plating method described by Kohli et al.,22 gold in short nanofiber form was deposited into the pores of the AAO template. As shown in Figs. 1(a) and 1(b), in addition to partially filling the pores with gold, the top surface of the AAO template was coated with a thin gold film (~100 nm) of Au. A ~30 μm layer of lacquer was then painted on the top of the thin gold film to serve as a supporting layer.

42 ENGINEERING↗
NASA NTRS1942

Strength tests of thin-walled elliptic duralumin cylinders in pure bending and in combined pure bending and torsion

An analysis is presented of the results of tests made by the Massachusetts Institute of Technology and by the National Advisory Committee for Aeronautics on an investigation of the strength of thin-walled circular and elliptic cylinders in pure bending and in combined torsion and bending. In each of the loading conditions, the bending moments were applied in the plane of the major axis of the ellipse.

Lundquist, Eugene E↗
DOE OSTI2014

Theoretical investigation of the relaxation of the bending mode of CH{sub 2}(X{sup ~}) by collisions with helium

We have earlier determined the dependence on the bending angle of the interaction of the methylene radical (CH{sub 2}) in its X{sup ~3}B{sub 1} state with He [L. Ma, P. J. Dagdigian, and M. H. Alexander, J. Chem. Phys. 136, 224306 (2012)]. By integration over products of the bending vibrational wave function, in a quantum close-coupled treatment we have calculated cross sections for the ro-vibrational relaxation of CH{sub 2}(X{sup ~}). Specifically, we find that cross sections for a loss of one vibrational quantum (v{sub b} = 2 → 1 and 1 → 0) are roughly two orders of magnitude smaller, and those for a loss of two vibrational quanta (v{sub b} = 2 → 0) four orders of magnitude smaller, than those for pure rotational relaxation. In addition, no clear cut dependence on the energy gap is seen.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

A surface with stress, extensional elasticity, and bending stiffness

We demonstrate that the surface of a commonly used polydimethylsiloxane formulation (PDMS, Sylgard 184) treated by ultraviolet ozonolysis (UVO) has significant surface stress, considerable extensional elasticity (the “Shuttleworth Effect”), and surface bending elasticity.

Lapinski, Nicole↗
NASA NTRS2024

Big Bend Ecological Forecasting: Integrating Earth Observations Into Invasive Species Management Decisions in Big Bend National Park in Texas

Located in Brewster County Texas, U.S., along the Texas-Mexico border, Big Bend National Park is 3,243 square kilometers of desert, mountains, and rivers. NASA’s MSFC Spring 2024 DEVELOP Team partnered with the National Park Service (NPS), to address the environmental concern of perineal invasive grasses in Big Bend National Park. Buffelgrass (Cenchrus ciliaris), introduced to the park in the 1940’s, poses an ongoing threat, and causes habitat destruction for many of the park’s native ecosystems. Buffelgrass amplifies fire risk in the park, aids in the destruction of historic structures, and alters stream channels. To address the rising concern of Buffelgrass presence, unique advanced spatial technique applications were necessary to construct a habitat suitability model and perform a comprehensive fire risk assessment. A habitat suitability model was developed considering climate, vegetation, and phenological variables, in addition to physical and topographical variables. Subsequently, a fire risk model was developed, taking into account fire history data, accessibility factors, climate trends and predictions, along with developed areas. Multi-Source Land Surface Phenology (LSP) Sentinel-2 and Landsat 8 Operational Land Imager (OLI) imagery were used to predict Buffelgrass hotspot locations throughout the park. These analyses allowed the identification of optimal Buffelgrass habitat and hotspot locations, as well as park zones that reflect the greatest risk for future Buffelgrass invasion and fire risk. The collective results of the habitat suitability model, fire risk assessment, and Buffelgrass hot spot identification will allow the NPS to facilitate efficient mitigation measures and management strategies, and improved resource allocation where it’s most needed.

remote sensing↗
NASA NTRSDate not supplied

A Novel Ultrasonic Fully Reversible Bending Fatigue Test Specimen for Simulated Gear Tooth Bending Fatigue

Gears in vertical lift applications will typically experience greater than 107bending fatigue cycles over their design lifetime. Currently, fatigue life prediction of gears exceeding 107cycles are based on empirical correlations, since collection of fatigue data beyond 107 cycles is impractical with traditional fatigue testing methods. Ultrasonic fatigue testing enables fatigue testing in excess of 109cycles in as few as 14 hours. In this paper, a novel specimen design for ultrasonic fatigue testing to accurately represent the geometry, stress profile, and residual stress of gear teeth in reversible bending fatigue is presented. The specimen design is discussed in detail, testing is performed to validate operating principles, and an initial fatigue data set of 8 specimens is presented.

Single Tooth Bending Fatigue↗
NASA NTRSDate not supplied

A Novel Ultrasonic Fully Reversible Bending Fatigue Test Specimen for Simulated Gear Tooth Bending Fatigue

Gears in vertical lift applications will typically experience greater than 107bending fatigue cycles over their design lifetime. Currently, fatigue life prediction of gears exceeding 107cycles are based on empirical correlations, since collection of fatigue data beyond 107 cycles is impractical with traditional fatigue testing methods. Ultrasonic fatigue testing enables fatigue testing in excess of 109cycles in as few as 14 hours. In this paper, a novel specimen design for ultrasonic fatigue testing to accurately represent the geometry, stress profile, and residual stress of gear teeth in reversible bending fatigue is presented. The specimen design is discussed in detail, testing is performed to validate operating principles, and an initial fatigue data set of 8 specimens is presented.

Single Tooth Bending Fatigue↗
NASA NTRS1976

Nonlinear Curvature Expressions for Combined Flapwise Bending, Chordwise Bending, Torsion and Extension of Twisted Rotor Blades

The nonlinear curvature expressions for a twisted rotor blade or a beam undergoing transverse bending in two planes, torsion, and extension were developed. The curvature expressions were obtained using simple geometric considerations. The expressions were first developed in a general manner using the geometrical nonlinear theory of elasticity. These general nonlinear expressions were then systematically reduced to four levels of approximation by imposing various simplifying assumptions, and in each of these levels the second degree nonlinear expressions were given. The assumptions were carefully stated and their implications with respect to the nonlinear theory of elasticity as applied to beams were pointed out. The transformation matrices between the deformed and undeformed blade-fixed coordinates, which were needed in the development of the curvature expressions, were also given for three of the levels of approximation. The present curvature expressions and transformation matrices were compared with corresponding expressions existing in the literature.

Kvaternik, R. G.↗
NASA NTRS1982

Coupled bending-bending-torsion flutter of a mistuned cascade with nonuniform blades

A set of aeroelastic equations describing the motion of an arbitrarily mistuned cascade with flexible, pretwisted, nonuniform blades is developed using an extended Hamilton's principle. The derivation of the equations has its basis in the geometric nonlinear theory of elasticity in which the elongations and shears are negligible compared to unity. A general expression for foreshortening of a blade is derived and is explicity used in the formulation. The blade aerodynamic loading in the subsonic and supersonic flow regimes is obtained from two dimensional, unsteady, cascade theories. The aerodynamic, inertial and structural coupling between the bending (in two planes) and torsional motions of the blade is included. The equations are used to investigate the aeroelastic stability and to quantify the effect of frequency mistuning on flutter in turbofans. Results indicate that a moderate amount of intentional mistuning has enough potential to alleviate flutter problems in unshrouded, high aspect ratio turbofans.

Kaza, K. R. V.↗
NASA NTRS1982

Coupled bending-bending-torsion flutter of a mistuned cascade with nonuniform blades

A set of aeroelastic equations describing the motion of an arbitrarily mistuned cascade with flexible, pretwisted, nonuniform blades is developed using an extended Hamilton's principle. The derivation of the equations has its basis in the geometric nonlinear theory of elasticity in which the elongations and shears are negligible compared to unity. A general expression for foreshortening of a blade is derived and is explicitly used in the formulation. The blade aerodynamic loading in the subsonic and supersonic flow regimes is obtained from two-dimensional, unsteady, cascade theories. The aerodynamic, inertial and structural coupling between the bending (in two planes) and torsional motions of the blade is included. The equations are used to investigate the aeroelastic stability and to quantify the effect of frequency mistuning on flutter in turbofans. Results indicate that a moderate amount of intentional mistuning has enough potential to alleviate flutter problems in unshrouded, high-aspect-ratio turbofans.

Kaza, K. R. V.↗