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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 811 records · Page 45
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Global function approach in structural analysis: Basic approach, numerical results

The structural response to a given environment is described by the differential equations of motion of deformable bodies. Analytic solutions of such problems for a reasonably large class of structural configurations are not within the realm of the possible. Consequently, the mathematical problem is recast into a numerical problem for solution on the computer. New technology in the space and energy fields led to a growing demand for accurate analysis which at times cannot be met due to the limits set by available budgets for computer time. In response to this need for more efficient numerical analysis, the possibilities of reducing the number of freedoms in the system through a revival of the global function approach were explored.

Almroth, B. O.↗
NASA NTRS1984

Coefficient of restitution for low velocity transverse impact of thin graphite-epoxy laminates

A simple model is presented for the low velocity impact behavior of thin plates composed of T300/5208 graphite/epoxy. The model, which is constructed on the assumption that the plate is inextensible in the fiber direction and that the material is incompressible in the z direction, is able to predict the energy absorbed by the target during an impact event, or the 'coefficient of restitution'. The plate essentially deforms by shear, allowing the model to neglect bending deformations. The coefficient of restitution is predicted to increase with large interlaminar shear strength and low transverse shear modulus of the laminate. The coefficient's experimentally measured values agree with model-predicted values within a reasonable error.

Lal, K. M.↗
NASA NTRS1991

Superplastic forming of Al-Li alloys for lightweight, low-cost structures

Superplastic forming of advanced aluminum alloys is being evaluated as an approach for fabricating low-cost, light-weight, cryogenic propellant tanks. Built-up structure concepts (with inherent reduced scrap rate) are under investigation to offset the additional raw material expenses incurred by using aluminum lithium alloys. This approach to fabrication offers the potential for significant improvements in both structural efficiency and overall manufacturing costs. Superplasticity is the ability of specially processed material to sustain very large forming strains without failure at elevated temperatures under controlled deformation conditions. It was demonstrated that superplastic forming technology can be used to fabricate complex structural components in a single operation and increase structural efficiency by as much as 60 percent compared to conventional configurations in skin-stiffened structures. Details involved in the application of this technology to commercial grade superplastic aluminum lithium material are presented. Included are identification of optimum forming parameters, development of forming procedures, and assessment of final part quality in terms of cavitation volume and thickness variation.

Hales, Stephen J.↗
NASA NTRS1993

Stochastic forcing of perturbation variance in unbounded shear and deformation flows

An alternative mechanism for growth and maintenance of perturbation variance - amplification in a straining flow of stochastically forced perturbations in the absence of exponential instabilities - is explored, using as examples unbounded constant shear and pure deformation flow for which closed-form solutions are available and neither of which support a nonsingular mode. With diffusive dissipation, amplification of isotropic band-limited stochastic driving is found to be unbounded for the case of pure deformation and to be bounded by a threefold increase at large shear for the case of a linear velocity profile. It is concluded that amplification of stochastic forcing in a straining field can maintain a variance field substantially more energetic than that resulting from the same forcing in the absence of a background straining flow.

Farrell, Brian F.↗
NASA NTRS2001

Structural Analysis of a 50 cm Diameter Open-Back Triangular Cell Beryllium Mirror in a Cryogenic Environment

This paper discusses NASTRAN structural analysis of the Sub-Scale Beryllium Mirror Demonstrator (SBMD), which has been developed by Ball Aerospace as an experimental design concept for the Next Generation Space Telescope (NGST). The mirror was repeatedly subjected to 35K environment in the large cryogenic test chamber at Marshall Space Flight Center (MSFC). Deformations on the mirror surface were measured optically. The surface distortions predicted by NASTRAN are analyzed optically for comparison with the measured values. Model results compare favorably with measured results for an ambient temperature validation case. For the cryogenic environment case the influence of geometry and material property variations is being investigated to obtain closer correlation.

Craig, Larry↗
NASA NTRS2009

Geological Map of the Fredegonde (V-57) Quadrangle, Venus

The area of V-57, the Fredegonde quadrangle (50-75degS, 60-120degE, Fig.1), is located within the eastern portion of Lada Terra within the topographic province of midlands (0-2 km above MPR [1,2]). Midlands form the most abundant portion of the surface of Venus and are characterized by diverse sets of units and structures [3-11]. The area of the Fredegonde quadrangle is in contact with the elevated portion of Lada Terra to the W and with the lowland of Aino Planitia to the NE. The transitions of the mid-lands to the lowlands and highlands are, thus, one of the main themes of the geology within the V-57 quadrangle. The character of the transitions and distribution and sequence of units/structures in the midlands are crucially important in understanding the time and modes of formation of this topographic province. The most prominent features in the map area are linear deformational zones consisting of swarms of grooves and graben and large coronae. The zones characterize the central and NW portions of the map area and represent regionally important, broad (up to 100s km wide) ridges that are 100s m high. Relatively small (100s km across, 100s m deep) equidimensional basins occur between the corona-groove-chains in the west and border the central chain from the east. Here we describe units that make up the surface within the V-57 quadrangle and present a summary of our geological map that shows the areal distribution of the major groups of units.

Ivanov, M. A.↗
NASA NTRS2013

Validation of Forested Inundation Extent Revealed by L-Band Polarimetric and Interferometric SAR Data

UAVSAR, NASA's airborne Synthetic Aperture Radar (SAR), conducted an extended observational campaign in Central and South America in March 2013, primarily related to volcanic deformations along the Andean Mountain Range but also including a large number of flights studying other scientific phenomena. During this campaign, the L-Band SAR collected data over the Napo River in Ecuador. The objectives of this experiment were to acquire polarimetric and interferometric L-Band SAR data over an inundated tropical forest in Ecuador simultaneously with on-the-ground field work ascertaining the extent of inundation, and to then derive from this data a quantitative estimate for the error in the SAR-derived inundation extent. In this paper, we will first describe the processing and preliminary analysis of the SAR data. The polarimetric SAR data will be classified by land cover and inundation state. The interferometric SAR data will be used to identify those areas where change in inundation extent occurred, and to measure the change in water level between two observations separated by a week. Second, we will describe the collection of the field estimates of inundation, and have preliminary comparisons of inundation extent measured in the field field versus that estimated from the SAR data.

Synthetic Aperture Radar (SAR),↗
DOE OSTI2024

Bayesian blacksmithing: discovering thermomechanical properties and deformation mechanisms in high-entropy refractory alloys

Finding alloys with specific design properties is challenging due to the large number of possible compositions and the complex interactions between elements. This study introduces a multi-objective Bayesian optimization approach guiding molecular dynamics simulations for discovering high-performance refractory alloys with both targeted intrinsic static thermomechanical properties and also deformation mechanisms occurring during dynamic loading. The objective functions are aiming for excellent thermomechanical stability via a high bulk modulus, a low thermal expansion, a high heat capacity, and for a resilient deformation mechanism maximizing the retention of the BCC phase after shock loading. Contrasting two optimization procedures, we show that the Pareto-optimal solutions are confined to a small performance space when the property objectives display a cooperative relationship. Conversely, the Pareto front is much broader in the performance space when these properties have antagonistic relationships. Density functional theory simulations validate these findings and unveil underlying atomic-bond changes driving property improvements.

36 MATERIALS SCIENCE↗
DOE OSTI2021

First observation of collective rotational bands in neutron-rich 142 La and the study of octupole/triaxial deformations in 142,143 La

Collective rotational bands were observed for the first time in neutron-rich odd–odd 142 La by means of γ-γ-γ and γ-γ-γ-γ coincidence measurements of prompt fission γ rays from 252 Cf using multi-detector array Gammasphere. Similarity between the yrast band of 142 La and those of neighboring 144 La, 144 Ce was found and interpreted as quasiparticle excitations. Here, PES calculations suggested triaxial deformation for the ground state of 142La. Considerable triaxial and near zero octupole deformations were deduced for the yrast band of 142 La by the TRS model calculations. The band-crossing observed in the yrast band of 142 La was interpreted to be caused by alignment of the (h 11/2 ) 2 proton pair, and the crossing frequency was best reproduced by the TRS calculations taking into account triaxial deformations. In contrast to the interpretations for the band crossing of 142 La, alignments of the (i 13/2 ) 2 neutron pair were found to be responsible for the band-crossing of the yrast band in the neighboring even-N 143 La, and triaxial degree of freedom was found to play a more significant role than octupole deformations in the nucleus, although its β 3 values deduced are large.

142La↗
DOE OSTI2023

Uniaxial stress increases layer stacking disorder in calcium silicate hydrates with low calcium content

The long-term stress response of concrete is controlled by the intergrain and intragrain interactions of calcium-silicate-hydrates (C-S-H), nanocrystalline forms of tobermorites. To investigate both types of interactions, we examined the deviatoric stress response of 11 Å tobermorite powder with X-ray diffraction, finding that its layer stacking (i.e., sliding) disorder significantly increases. A similar experiment was performed on nanocrystalline C-S-H powders before and after applying a 360 MPa uniaxial stress. Layer stacking disorder (in the form of intragrain deformation) increases when there is low water content and when the basal spacing is large. We also find that grains with a smaller thickness-to-diameter aspect ratio are first to develop preferred orientation (in the form of intergrain sliding), facilitated by gel water. Furthermore, these findings show that intragrain deformations in C-S-H can occur at relatively low stresses and provide insights into the creep mechanism of C-S-H.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Naturally Self-Tuned Low Mass Composite Scalars

Scalar bosons composed of a pair of chiral fermions in a non-confining potential have an effective Yukawa coupling, $g$, to free external chiral fermions. At large distance a Feynman loop of external fermions generates a scale invariant potential, $V_{loop}\propto -g^2/{\rho^{2}}$, for separation $\rho$, which acts on valence fermions. This generally forces the $s$-wave ground state to deform to a static, zero mass, configuration, and for slowly running, perturbative $g$, a large external "shroud" wave function forms. This is related to old results of Landau and Lifshitz in quantum mechanics. The massless composite scalar boson ground state is then an extended object. Infra-red effects can generate a small mass for the system. This points to a perturbative BEH-boson composed of top and anti-top quarks and a novel dynamical mechanism for spontaneous electroweak symmetry breaking.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1992

Crustal deformation along the San Andreas, California

The goal is to achieve a better understanding of the regional and local deformation and crustal straining processes in western North America, particularly the effects of the San Andreas and nearby faults on the spatial and temporal crustal deformation behavior. Construction of theoretical models based on the mechanics of coupled elastic plate, viscoelastic foundation and large scale crack mechanics provide a rational basis for the interpretation of seismic and aseismic anomalies and expedite efforts in forecasting the stability of plate boundary deformation. Special focus is placed on the three dimensional time dependent surface deformation due to localized slippage in a elastic layer coupled to a visco-elastic substrate. The numerical analysis is based on a 3-D boundary element technique. Extension to visco-elastic coupling demands the derivation of 3-D time dependent Green's function. This method was applied to analyze the viscoelastic surface displacements due to a dislocated embedded patch. Surface uplift as a function of time and position are obtained. Comparisons between surface uplift for long and short dislocated patches are made.

Li, Victor C.↗
DOE OSTI2022

Shape memory in self-adapting colloidal crystals

We report reconfigurable, mechanically responsive crystalline materials are central components in many sensing, soft robotic, and energy conversion and storage devices1,2,3,4. Crystalline materials can readily deform under various stimuli and the extent of recoverable deformation is highly dependent upon bond type1,2,5,6,7,8,9,10. Indeed, for structures held together via simple electrostatic interactions, minimal deformations are tolerated. By contrast, structures held together by molecular bonds can, in principle, sustain much larger deformations and more easily recover their original configurations. In this report we study the deformation properties of well-faceted colloidal crystals engineered with DNA. These crystals are large in size (greater than 100 µm) and have a body-centred cubic (bcc) structure with a high viscoelastic volume fraction (of more than 97%). Therefore, they can be compressed into irregular shapes with wrinkles and creases, and, notably, these deformed crystals, upon rehydration, assume their initial well-formed crystalline morphology and internal nanoscale order within seconds. For most crystals, such compression and deformation would lead to permanent, irreversible damage. The substantial structural changes to the colloidal crystals are accompanied by notable and reversible optical property changes. For example, whereas the original and structurally recovered crystals exhibit near-perfect (over 98%) broadband absorption in the ultraviolet–visible region, the deformed crystals exhibit significantly increased reflection (up to 50% of incident light at certain wavelengths), mainly because of increases in their refractive index and inhomogeneity.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Quality concerns caused by quality control — deformation of silicon strip detector modules in thermal cycling tests

The ATLAS experiment at the Large Hadron Collider (LHC) is currently preparing to replace its present Inner Detector (ID) with the upgraded, all-silicon Inner Tracker (ITk) for its High-Luminosity upgrade (HL-LHC). The ITk will consist of a central pixel tracker and the outer strip tracker, consisting of about 19,000 strip detector modules. Each strip module is assembled from up to two sensors, and up to five flexes (depending on its geometry) in a series of gluing, wirebonding and quality control steps. During detector operation, modules will be cooled down to temperatures of about -35 °C (corresponding to the temperature of the support structures on which they will be mounted) after being initially assembled and stored at room temperature. In order to ensure compatibility with the detector's operating temperature range, modules are subjected to thermal cycling as part of their quality control process. Ten cycles between -35 °C and +40 °C are performed for each module, with full electrical characterisation tests at each high and low temperature point. As part of an investigation into the stress experienced by modules during cooling, it was observed that modules generally showed a change in module shape before and after thermal cycling. This paper presents a summary of the discovery and understanding of the observed changes, connecting them with excess module stress, as well as the resulting modifications to the module thermal cycling procedure.

47 OTHER INSTRUMENTATION↗
NASA NTRS1971

Tracking antenna deformation program

Computer program provides capability for analyzing accelerometer data obtained from impulsive testing of large antennas, and of determining from that data pertinent characteristics /amplitude, frequency, damping/ of the structural modes excited by the impulse.

Galef, A. E.↗
NASA NTRS1991

Prediction of unsteady aerodynamic loads in cascades using the linearized Euler equations on deforming grids

A linearized Euler solver for calculating unsteady flows in turbomachinery blade rows due to both incident gusts and blade motion is presented. Using the linearized Euler technique, one decomposes the flow into a mean (or steady) flow plus an unsteady, harmonically varying, small disturbance flow. Linear variable coefficient equations describe the small disturbance behavior of the flow, and are solved using a pseudo-time marching Lax-Wendroff scheme. For the blade motion problem, a harmonically deforming computational rid that conforms to the motion of vibrating blades eliminates large error producing mean flow gradient terms that would otherwise appear in the unsteady flow tangency boundary condition. The paper also presents a new, numerically exact, nonreflecting far-field boundary condition based on an eigenanalysis of the discretized equations. Computed flow solutions demonstrate the computational accuracy and efficiency of the present method. The solution of the linearized Euler equations requires one to two orders of magnitude less computer time than solution of the nonlinear Euler equations using traditional time-accurate time-marching techniques. In addition, the deformable grid significantly improves the accuracy of the solution.

Hall, Kenneth C.↗
NASA NTRS1993

Models of thermal/chemical boundary layer convection: Potential application to Venus

The upper boundary layer of Venus is comprised of at least two distinct chemical components, mantle and crust. Fluid dynamical models of convection within Venus' mantle were primarily of the thermal boundary layer type. Models assessing the ability of convective mantle flows to deform the crust were undertaken, but models exploring the effects of a variable thickness crust on mantle convection were largely lacking. A Venusian crust of variable thickness could couple back into, and alter, the mantle flow patterns that helped create it, leading to deformation mechanisms not predicted by purely thermal boundary layer convection models. This possibility is explored through a finite element model of thermal/chemical boundary layer convection. Model results suggest that a crust of variable thickness can serve as a mantle flow driver by perturbing lateral temperature gradients in the upper mantle. Resulting mantle flow is driven by the combination of free convective and nonuniform crustal distribution. This combination can lead to a flow instability manifest in the occurrence of episodic mantle lithosphere subduction initiated at the periphery of a crustal plateau. The ability of a light, near surface, chemical layer to potentially alter mantle flow patterns suggest that mantle convection and the creation and/or deformation of such a chemical layer may be highly nonseparable problems on time scales of 10(exp 8) years.

Lenardic, A.↗
NASA NTRS2004

Analytical and Experimental Characterization of Gravity Induced Deformations In Subscale Gossamer Structures

The development of gossamer space structures such as solar sails and sunshields presents many challenges due to their large size and extreme flexibility. The post-deployment structural geometry exhibited during ground testing may significantly depart from the in-space configuration due to the presence of gravity-induced deformations (gravity sag) of lightly preloaded membranes. This paper describes a study carried out to characterize gravity sag in two subscale gossamer structures: a single quadrant from a 2 m, 4 quadrant square solar sail and a 1.7 m membrane layer from a multi-layer sunshield The behavior of the test articles was studied over a range of preloads and in several orientations with respect to gravity. An experimental study was carried out to measure the global surface profiles using photogrammetry, and nonlinear finite element analysis was used to predict the behavior of the test articles. Comparison of measured and predicted surface profiles shows that the finite dement analysis qualitatively predicts deformed shapes comparable to those observed in the laboratory. Quantitatively, finite element analysis predictions for peak gravity-induced deformations in both test articles were within 10% of measured values. Results from this study provide increased insight into gravity sag behavior in gossamer structures, and demonstrates the potential to analytically predict gravity-induced deformations to within reasonable accuracy.

Johnston, John D.↗