Search NASA⌕ Search

SEARCH · Search NASA

Results for “High loading rate”

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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Nacelle Aerodynamic and Inertial Loads (NAIL) project

Inlet airloads were measured by integration of pressures recorded at 252 locations on the right hand inboard (JT9D-7A) nacelle of the Boeing 747 aircraft. Pressures were recorded at 45 locations on the right hand outboard nacelle for comparison. Inertial loads were measured on both nacelles using accelerometers and rate gyros. Flight conditions included takeoffs at several gross weights, high g turns, and a simulated acceptance flight. Airloads at takeoff rotation were found to be larger than at any other normal service condition because of the combined effects of high angle of attack and high engine airflow. Inertial loads were smaller than previous estimates had indicated. A procedure is given for estimating inlet airloads at low speeds and high angles of attack for any underwing high bypass ratio turbofan installation approximately resembling the one tested. Flight procedure modifications are suggested that may result in better fuel economy retention in service. Pressures were recorded on the core cowls and pylons of both engine installations and on adjacent wing surfaces for use in development of computer codes for analysis of installed propulsion system aerodynamic drag interference effects.

Source record↗
NASA NTRS1973

Role of plastic deformation in wear of copper and copper - 10-percent-aluminum alloy in cryogenic fuels

High-purity copper specimens and a copper-aluminum (10%) alloy specimen were subjected to sliding against Type 440 C in cryogenic fuel environments. It was found that virtually all wear occurred by the plastic deformation of a recrystallized layer extending to about 10 micrometers below the wear scar surface of the copper or copper alloy. The wear debris was in the form of a layered structure adhering to the exit region of the wear scar. Measurements on the high purity copper specimens indicated that the wear rate was proportional to the applied load and to the sliding velocity squared. A physical model of the wear process is proposed to account for these observations.

Bill, R. C.↗
NASA NTRS1973

Influence of gaseous hydrogen on metals

Tensile, fracture toughness, threshold stress intensity for sustained-load crack growth, and cyclic and sustained load crack growth rate measurements were performed on a number of alloys in high-pressure hydrogen and helium environments. The results of tensile tests performed in 34.5 MN/m2 (5000 psi) hydrogen indicated that Inconel 625 was considerable embrittled at ambient temperature but was not embrittled at 144 K (-200 F). The tensile properties of AISI 321 stainless steel were slightly reduced at ambient temperature and 144 K (-200 F). The tensile properties of Ti-5Al-2.5 Sn ELI were essentially unaffected by hydrogen at 144 K (-200 F). OFHC copper was not embrittled by hydrogen at ambient temperature or at 144 K (-200 F).

Walter, R. J.↗
NASA NTRS1974

Techniques for aerothermal tests of large, flightweight thermal protection panels in a Mach 7 wind tunnel

Recently developed experimental techniques permit evaluating thermal performance and structural integrity of full-scale panel concepts applicable to reentry and hypersonic vehicles in the Langley 8-foot high-performance structures tunnel. Rate and magnitude of surface heating and differential-pressure loading are independently controlled. Realistic temperature distributions are radiantly preheated into the panel prior to aerodynamic heating, and stream conditions are preselected to sustain the preheat surface heating input during aerodynamic exposure. During tunnel start and shutdown, panels are shielded outside the stream from potentially damaging transient acoustics and buffeting and are then rapidly inserted into the hypersonic flow. Infrared radiometry provides detailed surveys of surface temperatures.

Deveikis, W. D.↗
NASA NTRS1991

The use of carboranes as oxidation inhibitors for carbon-carbon composites

Carbon-carbon composites have many beneficial properties for use in aerospace applications, including their high specific strength and modulus at elevated temperatures. However, they share with all carbon based substances a strong tendency to burn when heated in air. In order to exploit their good qualities, it is necessary to slow or prevent their oxidation during use. Molecular inhibiters offer protection with the advantage of being able to form a homogeneous solution with the resin. Since boron oxides are known to provide the desired kind of protection, molecular compounds based on boron seem reasonable candidates to test as inhibitors. Performance tests indicated that carboranes are excellent materials for obtaining high uniform loadings of boron inhibitors in glassy carbon materials and thus reducing their rates of oxidation. Further, there is evidence that the use of substituted derivatives could provide more complete and thorough forms of protection.

Petty, John T.↗
NASA NTRS2001

Iogenic Plasma and its Rotation-Driven Transport in Jupiter's Magnetosphere

Model calculations are reported for the Iogenic plasma source created by atomic oxygen and sulfur above Io's exobase in the corona and extended clouds (Outer Region). On a circumplanetary scale, two-dimensional distributions produced by integrating the proper three dimensional rate information for electron impact and charge exchange processes along the magnetic field lines are presented for the pickup ion rates, the net-mass and total-mass loading rates, the mass per unit magnetic flux rate, the pickup conductivity, the radial pickup current, and the net-energy loading rate for the plasma torus. All of the two-dimensional distributions are highly peaked at Io's location and hence highly asymmetric about Jupiter. The Iogenic plasma source is also calculated on a much smaller near-Io scale to investigate the structure of the highly peak rates centered about lo's instantaneous location. The Iogenic plasma source for the Inner Region (pickup rates produced below Io's exobase) is, however, expected to be the dominant source near lo for the formation of the plasma torus ribbon and to be a comparable source, if not a larger contributor, to the energy budget of the plasma torus, so as to provide the necessary power to sustain the plasma torus radiative loss rate.

Smyth, William H.↗
NASA NTRS2016

System Level Aerothermal Testing for the Adaptive Deployable Entry and Placement Technology (ADEPT)

The Adaptive Deployable Entry and Placement Technology (ADEPT), a mechanically deployable entry vehicle technology, has been under development at NASA since 2011. As part of the technical maturation of ADEPT, designs capable of delivering small payloads (10 kg) are being considered to rapidly mature sub 1 m deployed diameter designs. The unique capability of ADEPT for small payloads comes from its ability to stow within a slender volume and deploy to achieve a mass efficient drag surface with a high heat rate capability. The low ballistic coefficient results in entry heating and mechanical loads that can be met by a revolutionary three-dimensionally woven carbon fabric supported by a deployable skeleton structure. This carbon fabric has test proven capability as both primary structure and payload thermal protection system. In order to rapidly advance ADEPTs technical maturation, the project is developing test methods that enable thermostructural design requirement verification of ADEPT designs at the system level using ground test facilities. Results from these tests are also relevant to larger class missions and help us define areas of focused component level testing in order to mature material and thermal response design codes. The ability to ground test sub 1 m diameter ADEPT configurations at or near full-scale provides significant value to the rapid maturation of this class of deployable entry vehicles. This paper will summarize arc jet test results, highlight design challenges, provide a summary of lessons learned and discuss future test approaches based upon this methodology.

Hypersonic↗
NASA NTRS1970

Electronically controlled motor drive system has ultra-high reliability and long lifetime

Direct drive electromechanical system is composed of brushless dc torque motor, offset-tooth magnetic sensor that derives position and rate information directly from output shaft, and rotary power transformer that transfers electrical power from external source to proper load. System has high servo loop stiffness and minimum power consumption.

Veillette, L. J.↗
NASA NTRS1989

Prediction of fatigue-crack growth in a high-strength aluminum alloy under variable-amplitude loading

The present paper is concerned with the application of an analytical crack-closure model to study crack growth under various load histories. The model was based on a concept like the Dugdale model, but modified to leave plastically deformed material in the wake of the advancing crack tip. The thickness effect was accounted for by using a 'constraint' factor on tensile yielding at the crack tip. The model was used to correlate crack-growth rates under constant-amplitude loading, and to predict crack growth under variable-amplitude loading on a high-strength aluminum alloy (7475-T7351) sheet material. The experimental data was obtained from Zhang et al. Predicted crack-growth lives agreed well with experimental data. For ten crack-growth tests subjected to various variable-amplitude load histories, the ratio of predicted-to-experimental lives ranged from 0.54 to 1.19. The mean value of predicted-to-experimental lives was 0.95 with a standard error of 0.2 for a constraint factor of 1.9.

Newman, J. C., Jr.↗
NASA NTRS1988

Alterations in crack-tip deformation during variable-amplitude fatigue crack growth

Fatigue crack growth rate changes caused by single overloads and an overload followed by an underload have been studied in the high-strength aluminum alloy 7091. Crack-tip plasticity parameters were measured at each step in the loading sequence using the stereoimaging technique. Effective stress-intensity factor was measured with high resolution immediately at the crack tip both before an overload and during the subsequent growth rate retardation period. Crack-tip opening displacement and strain were altered in the same way as growth rate following the overload/underload events, and similitude with respect to crack-tip plasticity was preserved during the growth retardation period. Effective stress-intensity factor was found to correlate well with crack growth rate. Strains within the plastic zone were converted to stress at each step in load change. These stresses were then summed to determine the zone of residual stress caused by the overload. The region of compressive residual stress ahead of the crack tip was found to increase with overload severity but was limited to yield stress in magnitude. An underload shrank the spatial extent of the residual stresses caused by the overload.

Davidson, David L.↗
NASA NTRS1998

Creep Strain and Strain Rate Response of 2219 Al Alloy at High Stress Levels

As a result of high localized plastic deformation experienced during proof testing in an International Space Station connecting module, a study was undertaken to determine the deformation response of a 2219-T851 roll forging. After prestraining 2219-T851 Al specimens to simulate strains observed during the proof testing, creep tests were conducted in the temperature range from ambient temperature to 107 C (225 F) at stress levels approaching the ultimate tensile strength of 2219-T851 Al. Strain-time histories and strain rate responses were examined. The strain rate response was extremely high initially, but decayed rapidly, spanning as much as five orders of magnitude during primary creep. Select specimens were subjected to incremental step loading and exhibited initial creep rates of similar magnitude for each load step. Although the creep rates decreased quickly at all loads, the creep rates dropped faster and reached lower strain rate levels for lower applied loads. The initial creep rate and creep rate decay associated with primary creep were similar for specimens with and without prestrain; however, prestraining (strain hardening) the specimens, as in the aforementioned proof test, resulted in significantly longer creep life.

Taminger, Karen M. B.↗
NASA NTRS1989

Prediction of fatigue-crack growth in a high-strength aluminum alloy under variable-amplitude loading

The present paper is concerned with the application of an analytical crack-closure model to study crack growth under various load histories. The model was based on a crack-tip plasticity concept like the Dugdale model, but modified to leave plastically deformed material in the wake of the advancing crack tip. The effect of material thickness on plasticity was accounted for by using a constraint factor on tensile yielding at the crack tip. The model was used to correlate crack-growth rates under constant-amplitude loading, and to predict crack growth under variable-amplitude loading on a high-strength aluminum alloy (7475-T7351) sheet material. The experimental data were obtained from Zhang et al. Predicted crack-growth lives agreed well with experimental data. For ten crack-growth tests subjected to various variable-amplitude load histories, the ratio of predicted-to-experimental lives ranged from 0.54 to 1.19. The mean value of the ratio of predicted-to-experimental lives was 0.95 and the standard error was 0.2 using a constraint factor of 1.9 in the model. Crack-opening stresses calculated from the model were significantly different from those determined by Zhang et al. using a striation-based experimental method.

Newman, J. C., Jr.↗
NASA NTRS1994

Hydro-isostatic deflection and tectonic tilting in the central Andes: Initial results of a GPS survey of Lake Minchin shorelines

Sufficiently large lake loads provide a means of probing rheological stratification of the crust and upper mantle. Lake Minchin was the largest of the late Pleistocene pluvial lakes in the central Andes. Prominent shorelines, which formed during temporary still-stands in the climatically driven lake level history, preserve records of lateral variations in subsequent net vertical motions. At its maximum extent the lake was 140 m deep and spanned 400 km N-S and 200 km E-R. The load of surficial water contained in Lake Minchin was sufficient to depress the crust and underlying mantle by 20-40 m, depending on the subjacent rheology. Any other differential vertical motions will also be recorded as departures from horizontality of the shorelines. We recently conducted a survey of shoreline elevations of Lake Minchin with the express intent of monitoring the hydro-isostatic deflection and tectonic tilting. Using real-time differential Global Positioning System (GPS), we measured topographic profiles across suites of shorelines at 15 widely separated locations throughout the basin. Horizontal and vertical accuracies attained are roughly 30 and 70 cm, respectively. Geomorphic evidence suggests that the highest shoreline was occupied only briefly (probably less than 200 years) and radiocarbon dates on gastropod shells found in association with the shore deposits constrain the age to roughly 17 kyr. The basin-side pattern of elevations of the highest shoreline is composed of two distinct signals: (27 +/- 1) m of hydro-isostatic deflection due to the lake load, and a planar tilt with east and north components of (6.8 +/- 0.4) 10(exp -5) and 9-5.3 +/- 0.3) 10(exp -5). This rate of tilting is too high to be plausibly attributed to steady tectonism, and presumably reflects some unresolved combination of tectonism plus the effects of oceanic and lacustrine loads on a laterally heterogeneous substrate. The history of lake level fluctuations is still inadequately known to allow detailed inferences of crust and mantle rheology. However, it is already clear that the effective elastic plate thickness is closer to 40 km than the 60-70 km crustal thickness in the central Andes and the effective viscosity is less than 5 10(exp 20) Pa s.

Bills, Bruce G.↗
NASA NTRS1977

Low cost silicon solar array project silicon materials task: Establishment of the feasibility of a process capable of low-cost, high volume production of silane (step 1) and the pyrolysis of silane to semiconductor-grade silicon (step 2)

Extended operation of a small process-development unit routinely produced high quality silane in 97+% yield from dichlorosilane. The production rate was consistent with design loadings for the fractionating column and for the redistribution reactor. A glass fluid-bed reactor was constructed for room temperature operation. The behavior of a bed of silcon particles was observed as a function of various feedstocks, component configurations, and operating conditions. For operating modes other than spouting, the bed behaved in an erratic and unstable manner. A method was developed for casting molten silicon powder into crack-free solid pellets for process evaluation. The silicon powder was melted and cast into thin walled quartz tubes that sacrificially broke on cooling.

Breneman, W. C.↗
NASA NTRS1984

Positive Electrode Fabrication for Bi-polar Ni-h2 Cells

Bi-Polar nickel hydrogen design studies indicated a potential improvement in energy density and specific energy if positive electrodes could be manufactured in configurations of twice or more of the present normal thickness. Such electrodes would have to achieve similar active material loading, utilization, and cycle life to conventional 0.8mm I.P.U. nickel hydrogen electrodes. A capability for producing 1.0mm dry sinter and 1.5mm slurry sinter structures on production processes and equipment was demonstrated. The EPI/USAF electrochemical impregnation process proved capable of loading thick electrodes to 1.60 g/cubic centimeters void or higher. Sample electrodes incurred 2000 high rate stress cycles without significant structural or performance degradation. Formation regimes developed for thin plaque are not optimal for thick plaque and further investigation into electrode capacity build-up would seem warranted. Thick electrode technology development is continuing under other programs and shows promise of fulfilling the projected energy density and specific energy improvements.

Edgar, T. A.↗
NASA NTRS1988

Materials and structures for hypersonic vehicles

Hypersonic vehicles are envisioned to require, in addition to carbon-carbon and ceramic-matrix composities for leading edges heated to above 2000 F, such 600 to 1800 F operating temperature materials as advanced Ti alloys, nickel aluminides, and metal-matrix composited; These possess the necessary low density and high strength and stiffness. The primary design drivers are maximum vehicle heating rate, total heat load, flight envelope, propulsion system type, mission life requirements and liquid hydrogen containment systems. Attention is presently given to aspects of these materials and structures requiring more intensive development.

Tenney, Darrel R.↗
NASA NTRS2019

Safe, High Power/Voltage Battery Module Design Challenges

NASA seeks to demonstrate a path for achieving safe, high power, and high performing Li-ion battery designs for the purpose of establishing design guidelines for our aeronautic and spacecraft applications. Safe means passively resistant to thermal runaway propagation of any single cell catastrophic thermal runaway. High power means capable of 3C continuous discharge without overheating. High performing means achieving > 160 Wh/kg, 200 Wh/L. The biggest challenge has been balancing a high flux light weight path for cell heat dissipation during the high rate discharge that minimizes thermal gradients between cells and also protects adjacent cells from the heat load of thermal runaway cell. Our solution includes an oscillating heat pipe spine that contacts every 18650 cell in the pack and careful cell design selection to maximize the range of initial temperatures conditions where the battery can safely complete the 3C discharge.

Thermal runaway↗
NASA NTRS1994

Screen test for cadmium and nickel plates

A new procedure is described which was recently developed to quantify loading uniformity of nickel and cadmium plates and to screen finished electrodes prior to cell assembly. The technique utilizes the initial solubility rates of the active material in a standard chemical deloading solution at fixed conditions. The method can provide a reproducible indication of plate loading uniformity in situations where high surface loading limits the free flow of deloading solution into the internal porosity of the sinter plate. A preliminary study indicates that 'good' cell performance is associated with higher deloading rates.

Phan, Angie H.↗