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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 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS1963

On the use of dynamic models for studying launch vehicle buffet and ground-wind loads

The complex nature of the random aerodynamic input forces associated with transonic buffet and ground winds leads to difficulty in analytical treatment of the response of launch vehicles to these important loading conditions. The application of aeroelastically scaled models in the wind tunnel as a mechanical analog of the matharnatically complex problem requiring solution is described. Scaling relationships involved in this approach are developed and some checks on their validity are presented. Model design and support techniques are discussed, and some typical results given. Some problems arising from the increased size of launch vehicles are discussed.

Perry W. Hanson↗
DOE OSTI2020

The effect of loading direction on the fracture behaviors of cortical bone at a dynamic loading rate

Here, the dynamic cracking processes in porcine cortical bone were visualized in real-time using the high-speed synchrotron X-ray phase-contrast imaging (PCI) technique in three osteon orientations: in-plane transverse, out-of-plane transverse and in-plane longitudinal. The dynamic flexural loading applied on the pre-notched bone specimens was introduced by a modified Kolsky compression bar. High-speed X-ray images of the entire loading events were documented with a high-speed camera. Three-dimensional X-ray micro-computed tomography was conducted to examine the intact microstructures and obtain the basic material properties of the bone material used for mechanical characterizations. The onset location, where crack initiated, and the subsequent direction, along which the incipient crack propagated, were measured quantitatively using the high-speed X-ray images and the latter was found dependent on the osteon direction significantly. The crack propagation velocities were dependent on crack extension over the entire crack path significantly for all the three directions while the initial velocity for in-plane longitudinal direction was lower than the other two directions. Straight-through crack paths were observed for in-plane longitudinal specimens while the cracks were deflected and twisted in the in-plane transverse direction. For out-of-plane transverse direction, the cracks follow paths with tortuosity fall in between the other two directions, showing a mixed mode of fractures of the former two extreme cases. The toughening mechanisms, visualized by the high-speed X-ray images, and the corresponding fracture toughness, evaluated in terms of fracture initiation toughness and crack growth resistance curve (R-curve), were also found significantly different among the three osteon directions, suggesting an overall transition from brittle to ductile-like fracture behaviors at the dynamic displacement rate (5.4 m/s) as the osteon orientation varies from in-plane longitudinal to out-of-plane transverse, and to in-plane transverse eventually.

42 ENGINEERING↗
DOE OSTI2024

UMap: An application-oriented user level memory mapping library

Exploiting the prominent role of complex memories in exascale node architecture, the UMap page fault handler offers new capabilities to access large memory-mapped data sets directly. UMap provides flexible configuration options to customize page handling to each application, including analysis of massive observational and simulation data sets. The high-performance design features I/O decoupling, dynamic load balancing, and application-level controls. Page faults triggered by application threads and processes accessing data mapped to a UMapp’ed region are handled via the Linux userfaultfd protocol, an asynchronous message-oriented kernel-user communication mechanism that avoids the context switch penalty of traditional signal fault handlers. UMap is fully open source. In this paper, we give an overview of the UMap library architecture, its extensible plugin architecture, and the use/performance of UMap in emerging heterogeneous memory hierarchies such as near-node Non-volatile Memory (NVM) and network attached memories. We highlight new capabilities in two pagefault management plugins, the NetworkStore and SparseStore. We demonstrate the integration between UMap and multiple ECP products including Caliper, Metall, ZFP, Mochi, and Ripples.

97 MATHEMATICS AND COMPUTING↗
NASA NTRS1982

Evolution of the Tharsis province of Mars - The importance of heterogeneous lithospheric thickness and volcanic construction

A new model for the origin and evolution of the Tharsis province that emphasizes that the topography of Tharsis may be produced largely by construction, rather than uplift, is proposed. Underlying the model is the premise that the elastic lithosphere of Mars was laterally heterogeneous early in Martian history; such heterogeneity is discernible later in Martian history from the variable tectonic response of the lithosphere to local surface loads. It is contended that the mechanism for the evolution of Tharsis described here led to permanent topographic and gravity highs and a greatly thickened crust in the Tharsis region. An important advantage of the model is that no anomalous dynamical or chemical properties need be sustained in the Martian mantle beneath Tharsis for billions of years. The mantle beneath Tharsis is thus seen as playing a passive rather than an active role in the regional volcanic and tectonic activity, much like the role of the mantle beneath major midocean ridges on earth.

Solomon, S. C.↗
NASA NTRS1988

The nonlinear behavior of a passive zero-spring-rate suspension system

Various concepts for advanced syspension systems have been proposed for counteracting gravity loads in ground vibration testing of large space structures. Approximating the flight modes of a low-frequency flexible structure in a ground test requires a very soft suspension system. The dynamic behavior of a passive zero-spring-rate mechanism, sometimes used for such ground testing, is analyzed. This mechanism reduces the stiffness inherent in suspending a test specimen by cables. However, the mechanism is shown to be sensitive to imperfections. Imperfections can initiate nonlinear behavior which becomes more pronounced at lower operating frequencies. Furthermore, large pendular motion of the suspension system couples with the vertical motion, producing additional nonlinearity.

Woodard, Stanley E.↗
NASA NTRS2005

Strain Rate Sensitivity of Epoxy Resin in Tensile and Shear Loading

The mechanical response of E-862 and PR-520 resins is investigated in tensile and shear loadings. At both types of loading the resins are tested at strain rates of about 5x10(exp 5), 2, and 450 to 700 /s. In addition, dynamic shear modulus tests are carried out at various frequencies and temperatures, and tensile stress relaxation tests are conducted at room temperature. The results show that the toughened PR-520 resin can carry higher stresses than the untoughened E-862 resin. Strain rate has a significant effect on the response of both resins. In shear both resins show a ductile response with maximum stress that is increasing with strain rate. In tension a ductile response is observed at low strain rate (approx. 5x10(exp 5) /s), and brittle response is observed at the medium and high strain rates (2, and 700 /s). The hydrostatic component of the stress in the tensile tests causes premature failure in the E-862 resin. Localized deformation develops in the PR-520 resin when loaded in shear. An internal state variable constitutive model is proposed for modeling the response of the resins. The model includes a state variable that accounts for the effect of the hydrostatic component of the stress on the deformation.

Gilat, Amos↗
DOE OSTI2022

Hexagonal Distributed Embedded Energy Converters (HexDEECs)

The HexDEEC is a small, characteristic length approximating a centimeter, energy transducer that converts the dynamic deformations of its elastomer housing into electricity through a variable capacitance charging-discharging cycle. This device is a type of Distributed Embedded Energy Converter Technology (DEEC-Tec), a new domain for marine renewable energy research that utilizes a conglomeration of small distributed embedded energy converters (DEECs) that, in aggregate, form larger metamaterial frameworks. These resulting DEEC-Tec metamaterials can then, in turn, be used to construct flexible ocean wave energy converters called flexWECs, which can utilize a broad band of ocean wave frequencies and lack highly loaded rigid bodies. These systems also provide new avenues of wave energy harvesting such as actively transforming topologies (e.g., shape and form) and morphologies (e.g., stiffness and damping throughout its entire structure) in real time. Presented, is one specific type of DEEC: the HexDEEC, which is currently being developed by the United States National Renewable Energy Laboratory. This transducer shows promise in aiding the adoption and further development of the DEEC-Tec domain. The following presentation focuses on the promise of this technology and current work being done to analyze the performance of an individual HexDEEC design. The HexDEEC is composed of a hyperelastic hexagonal housing, nominally silicon rubber, with six electrodes on its inner faces. The upper three electrodes share the same charge while the lower three electrodes oppose the upper electrode charges. Externally, the HexDEEC has two arms extending away from the middle vertices of the hexagon. Via principles governing the relationship between electrical capacitance and electrical potential (voltage and charge), electricity is generated when the HexDEEC's arms are dynamically pulled or released under tensile loading, as doing so causes the distance between the upper and lower sets of electrodes to change - varying the energy converter's overall capacitance. Analytical and numerical modeling is being used to evaluate the mechanics and electrical energy generated by the HexDEEC. Equations to describe the capacitance and electrostatic forces acting on this unique system have been developed and implemented into the numerical modeling software STAR-CCM+, along with models to describe its hyperelastic material, such as the Mooney-Rivlin 3-parameter model. So far, an initial design has been analyzed and we plan to further optimize it to increase power production. Individual HexDEECs have been fabricated by drawing uncured liquid silicon rubber into molds via vacuum pressure. To simplify manufacturing, HexDEEC sub-components - e.g., electrodes, wires - can be placed within those molds such that they are directly embedded into the hexagonal housing during the curing process. Furthermore, DEEC-Tec metamaterials can be created by interweaving or sequentially layering multiple HexDEEC strands together. The HexDEEC based metamaterial could then generate electricity through its gross deformations. Ultimately, HexDEECs represent a specific type of energy transducer that can be leveraged, by the DEEC-Tec domain, to create metamaterials used to construct novel flexWECs.

DEEC-Tec↗
NASA NTRS1975

A simulation study of active feedback supression of dynamic response in helicopter rotor blades

A parameter study is presented for active feedback control applied to a helicopter rotor blade during forward flight. The study was performed on an electromechanical apparatus which included a mechanical model rotor blade and electronic analog simulation of interaction between blade deflections and aerodynamic loading. Blade response parameters were obtained for simulated vortex impinging at the blade tip at one pulse per revolution, and for a pulse which traveled from the blade tip toward its root. Results show that the response in a 1 - 10-per-rev frequency band is diminished by the feedback action, but at the same time responses at frequencies above 10-per-rev become increasingly more prominent with increased feedback amplitude, and can even lead to instability at certain levels. It appears that the latter behavior results from limitations of the laboratory simulation apparatus, rather than genuine potential behavior for a prototype helicopter.

Kana, D. D.↗
NASA NTRS1988

Design, fabrication, and dynamic testing of a V-groove radiator mechanical development unit

This paper describes the design, fabrication, and dynamic testing of a V-groove radiator development unit. The intended goal was to survive the dynamic environment of the Mars Observer mission. The development unit was designed to achieve a temperature of 80 K with a heat load of about 80 milliwatts. An analysis was performed to predict the thermal performance of the development unit. The radiator with a mass mockup of a Gamma Ray Spectrometer detector, the most massive of the candidate Mars Observer instrument detectors (1.7 Kg), passed vibration and acoustic testing to the Mars Observer requirements in effect at that time.

Petrick, S. Walter↗
NASA NTRS2014

Implementation of Statistical Process Control: Evaluating the Mechanical Performance of a Candidate Silicone Elastomer Docking Seal

The National Aeronautics and Space Administration has been developing a novel docking system to meet the requirements of future exploration missions to low-Earth orbit and beyond. A dynamic gas pressure seal is located at the main interface between the active and passive mating components of the new docking system. This seal is designed to operate in the harsh space environment, but is also to perform within strict loading requirements while maintaining an acceptable level of leak rate. In this study, a candidate silicone elastomer seal was designed, and multiple subscale test articles were manufactured for evaluation purposes. The force required to fully compress each test article at room temperature was quantified and found to be below the maximum allowable load for the docking system. However, a significant amount of scatter was observed in the test results. Due to the stochastic nature of the mechanical performance of this candidate docking seal, a statistical process control technique was implemented to isolate unusual compression behavior from typical mechanical performance. The results of this statistical analysis indicated a lack of process control, suggesting a variation in the manufacturing phase of the process. Further investigation revealed that changes in the manufacturing molding process had occurred which may have influenced the mechanical performance of the seal. This knowledge improves the chance of this and future space seals to satisfy or exceed design specifications.

docking seal↗
DOE OSTI2022

Mechanical properties, failure mechanisms, and scaling laws of bicontinuous nanoporous metallic glasses

Molecular dynamics simulations are employed to study the mechanical properties of nanoporous Cu x Zr 1-x metallic glasses (MGs) with five different compositions, x = 0.28, 0.36, 0.50, 0.64, and 0.72, and porosity in the range 0.1 < Φ < 0.7. Results from tensile loading simulations indicate a strong dependence of Young's modulus, E, and Ultimate Tensile Strength (UTS) on porosity and composition. By increasing the porosity from Φ = 0.1 to Φ = 0.7, the topology of the nanoporous MG shifts from closed cell to open-cell bicontinuous. The change in nanoporous topology enables a brittle-to-ductile transition in deformation and failure mechanisms from a single critical shear band to necking and rupture of ligaments. Genetic Programming (GP) is employed to find scaling laws for E and UTS as a function of porosity and composition. Here, a comparison of the GP-derived scaling laws against existing relationships shows that the GP method is able to uncover expressions that can predict accurately both the values of E and UTS in the whole range of porosity and compositions considered.

36 MATERIALS SCIENCE↗
DOE OSTI2022

A concurrent irradiation-mechanics multiscale coupling model

The vast majority of our current knowledge regarding the basic mechanisms controlling irradiation effect on mechanical properties is based almost entirely on the results of post-irradiation experiments or theoretical models. However, the concurrent effects of irradiation, mechanical stress, and thermal damage on the failure phenomena of materials and components remain largely unexplored due to its internal multiscale-multiphysics coupling nature. Here, we present here a concurrent irradiation-mechanics multiscale coupling model. The concurrent evolutions of nanoscale irradiation defect clusters, microscale dislocation configurations, and mechanical responses are well captured based on coupling cluster dynamics, discrete dislocation dynamics, and the finite element methods using an effective time marching scheme. Model predictions of defect densities and size are in general agreement with experimental observations. Irradiation hardening is shown to take place also in samples undergoing concurrent irradiation-mechanical loading, similar to samples tested post-irradiation. However, the occurrence of plastic flow localization and dislocation channel formation is not accompanied with apparent yield drop (softening) under concurrent irradiation-mechanical loading conditions, which is different from the post-irradiation case.

42 ENGINEERING↗
DOE OSTI2022

Dynamic characterization and performance evaluation of a 10-kW power take-off with mechanical motion rectifier for wave energy conversion

The power take-off (PTO) is a key component for wave energy converters. In this paper, a compact PTO with mechanical motion rectification rated at 10 kW is designed and prototyped, and characterized. A piecewise nonlinear dynamic model is established to describe its unique dynamic property. A linear hydraulic actuator is adopted in lab testing to drive the prototype and the unknown parameters of the dynamic model are identified. Further verification shows that the model can predict the dynamic performance of the PTO well. The test results show that the mechanical motion rectifier-based PTO can achieve overall energy transfer efficiency as high as 65% in regular waves even when the generator is working below the rated electric load and speed. In the irregular wave test, the PTO achieved the overall energy transfer efficiency of 54%, and the peak-to-average ratio acquired during the test is 12.5.

16 TIDAL AND WAVE POWER↗
DOE OSTI2021

A Hybrid Heavy-Duty Diesel Power System for Off-Road Applications - Concept Definition

A multi-year Power System R&D project was initiated with the objective of developing an off-road hybrid heavy-duty concept diesel engine with front end accessory drive-integrated energy storage. This off-road hybrid engine system is expected to deliver 15-20% reduction in fuel consumption over current Tier 4 Final-based diesel engines and consists of a downsized heavy-duty diesel engine containing advanced combustion technologies, capable of elevated peak cylinder pressures and thermal efficiencies, exhaust waste heat recovery via SuperTurbo™ turbocompounding, and hybrid energy recovery through both mechanical (high speed flywheel) and electrical systems. The first year of this project focused on the definition of the hybrid elements using extensive dynamic system simulation over transient work cycles, with hybrid supervisory controls development focusing on energy recovery and transient load assist, in Caterpillar’s DYNASTY™ software environment. Three key off-road applications were the focus of the hybrid concept definition with an aim of understanding the system’s modular capability for the diverse off-road heavy-duty market. Core engine performance 1D and 3D simulations isolated the efficiency contributions from the downsized engine, turbocompounding, and in-cylinder thermal barrier coatings. A fuel consumption improvement range of 14 to 24% was predicted, resulting in successful project progression to the design and experimental validation phase. Furthermore, an overview of the experimental engine and hybrid system status concludes the discussion along with the multi-year project’s next steps.

33 ADVANCED PROPULSION SYSTEMS↗
NASA NTRS1972

Lunar soil properties and soil mechanics

The study to identify and define recognizable fabrics in lunar soil in order to determine the history of the lunar regolith in different locations is reported. The fabric of simulated lunar soil, and lunar soil samples are discussed along with the behavior of simulated lunar soil under dynamic and static loading. The planned research is also included.

Mitchell, J. K.↗
NASA NTRS1971

Electric contact phenomena in ultra clean and specifically contaminated systems.

Contact resistance has been used to characterize the processes of physical contact in metallic systems with ultraclean surfaces. The contact resistance versus load curves of iron and two cobalt alloys were used to demonstrate the existence of surface work hardening and interfacial creep during contact as well as the fracture characteristics of an interfacial junction as the load is removed. The presence of an adsorbed film of hydrogen or hydrogen ions on iron completely changes the contact process. A comparison of the contact resistance versus load data for ultrapure iron, and iron-cobalt alloy, and a cobalt molybdenum-chromium was used to illustrate the effect of substrate mechanical properties on static adhesion and the ability to convert these data for the estimation of the dynamic coefficient of friction under the particular experimental conditions.

Keller, D. V., Jr.↗
NASA NTRS2010

Comparisons Between Stability Prediction and Measurements for the Reusable Solid Rocket Motor

The Space Transportation System has used the solid rocket boosters for lift-off and ascent propulsion over the history of the program. Part of the structural loads assessment of the assembled vehicle is the contribution due to solid rocket booster thrust oscillations. These thrust oscillations are a consequence of internal motor pressure oscillations active during operation. Understanding of these pressure oscillations is key to predicting the subsequent thrust oscillations and vehicle loading. The pressure oscillation characteristics of the Reusable Solid Rocket Motor (RSRM) design are reviewed in this work. Dynamic pressure data from the static test and flight history are shown, with emphasis on amplitude, frequency, and timing of the oscillations. Physical mechanisms that cause these oscillations are described by comparing data observations to predictions made by the Solid Stability Prediction (SSP) code.

Fischbach, Sean R.↗
DOE OSTI2025

Multi-scale Interaction Mechanism for Edge-Localized-Mode Suppression in the Tokamak Edge

A central challenge in fusion energy is reconciling the high-confinement mode required for reactor performance with the intense intermittent relaxation events it produces, known as edge-localized modes. These instabilities arise in the steep pressure pedestal at the plasma edge when magnetohydrodynamic thresholds are crossed, inflicting damaging heat loads on reactor components. Here, we show that multiscale interactions between microscopic turbulence and macroscopic magnetohydrodynamic modes provide encouraging prospects for self-organized edge-localized modes regulation. Using direct quantitative measurements of multiscale modes, eddy dynamics, and turbulent flux, we show that small-scale electron drift wave turbulence actively scatters the large-scale peeling-ballooning modes. This scattering decorrelates the pressure and velocity fields of the instability, so arresting its growth. Our modeling and theoretical analysis confirm this suppression mechanism is effective even when conventional linear stability thresholds are exceeded. This work establishes a nonlinear principle for edge-localized modes stability, revealing how ambient micro-turbulence can be leveraged to maintain a macro-stable, high-performance pedestal for future fusion reactors.

experimental nuclear physics↗