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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Preliminary science report on the directional solidification of hypereutectic cast iron during KC-135 low-G maneuvers

An ADSS-P directional solidification furnace was reconfigured for operation on the KC-135 low-g aircraft. The system offers many advantages over quench ingot methods for study of the effects of sedimentation and convection on alloy formation. The directional sodification furnace system was first flown during the September 1982 series of flights. The microstructure of the hypereutectic cast iron sample solidified on one of these flights suggests a low-g effect on graphite morphology. Further experiments are needed to ascertain that this effect is due to low-gravity and to deduce which of the possible mechanisms is responsible for it.

Curreri, P. A.↗
NASA NTRS1982

The thermal fatigue resistance of H-13 Die Steel for aluminum die casting dies

The effects of welding, five selected surface coatings, and stress relieving on the thermal fatigue resistance of H-13 Die Steel for aluminum die casting dies were studied using eleven thermal fatigue specimens. Stress relieving was conducted after each 5,000 cycle interval at 1050 F for three hours. Four thermal fatigue specimens were welded with H-13 or maraging steel welding rods at ambient and elevated temperatures and subsequently, subjected to different post-weld heat treatments. Crack patterns were examined at 5,000, 10,000, and 15,000 cycles. The thermal fatigue resistance is expressed by two crack parameters which are the average maximum crack and the average cracked area. The results indicate that a significant improvement in thermal fatigue resistance over the control was obtained from the stress-relieving treatment. Small improvements were obtained from the H-13 welded specimens and from a salt bath nitrogen and carbon-surface treatment. The other surface treatments and welded specimens either did not affect or had a detrimental influence on the thermal fatigue properties of the H-13 die steel.

Source record↗
NASA NTRS1983

Correlation of solar cell electrical properties with material characteristics of silicon cast by the ubiquitous crystallization process

Solar cells were fabricated using a conservative 'baseline' process on 1-3 Omega-cm p-type silicon from ingots cast by the ubiquitous crystallization process. Conversion efficiencies of the cells were measured, as well as spectral response and minority carrier diffusion length. Adjacent slices from the same ingot were studied for their grain size, dislocation distribution, and impurity distribution. Cell performance was related to the observed structural features, as well as to the chemical structure of the ingot.

Hyland, S.↗
NASA NTRS1984

Tests on a CAST 7 two-dimensional airfoil in a streamlining test section

A unique opportunity has arisen to test one and the same airfoil model of CAST-7 section in two wind tunnels having adaptive walled test sections. The tunnels are very similar in terms of size and the available range of test conditions, but differ principally in their wall setting algorithms. Detailed data from the tests of the model in the Southampton tunnel, are included with comparisons between various sources of data indicating that both adaptive walled test sections provide low interference test conditions.

Goodyear, M. J.↗
NASA NTRS1984

High Reynolds number tests of the cast 10-2/DOA2 transonic airfoil at ambient and cryogenic temperature conditions

The transonic airfoil CAST 10-2/DOA2 was investigated in several major transonic wind tunnels at Reynolds numbers ranging from Re=1 million six hundred thousand to forty five million at ambient and cryogenic temperature conditions. The main objective was to study the degree and extent of the effects of Reynolds on both the airfoil aerodynamic characteristics and the interference effects of various model-wind-tunnel systems. the initial analysis of the 10-2 airfoil results revealed appreciable real Reynolds number effects on this airfoil and, moreover, showed that wall interference, can be significantly affected by changes in Reynolds number thus appearing as true Reynolds number effects.

Stanewsky, E.↗
NASA NTRS1984

Analysis and calculation of macrosegregation in a casting ingot, exhibits C and E

A computer model which describes the solidification of a binary metal alloy in an insulated rectangular mold with a temperature gradient is presented. A numerical technique, applicable to a broad class of moving boundary problems, was implemented therein. The solidification model described is used to calculate the macrosegregation within the solidified casting by coupling the equations for liquid flow in the solid/liquid or mushy zone with the energy equation for heat flow throughout the ingot and thermal convection in the bulk liquid portion. The rate of development of the solid can be automatically calculated by the model. Numerical analysis of such solidification parameters as enthalpy and boundary layer flow is displayed. On-line user interface and software documentation are presented.

Poirier, D. R.↗
NASA NTRS1984

High Reynolds number tests of the cast 10-2/DOA 2 airfoil in the Langley 0.3-meter transonic cryogenic tunnel, phase 2

Wind tunnel tests of an advanced technology airfoil, the CAST 10-2/DOA 2, were conducted in the Langley 0.3-Meter Transonic Cryogenic Tunnel (0.3-m TCT). This was the third of a series of tests conducted in a cooperative airfoil research program between the National Aeronautics and Space Administration and the Deutsche Forschungsund Versuchsanstalt fur Luft- und Raumfahrt e. V. For these tests, temperature was varied from 270 K to 110 K at pressures from 1.5 to 5.75 atmospheres. Mach number was varied from 0.60 to 0.80, and the Reynolds number (based on airfoil chord) was varied from 2 to 20 million. The aerodynamic data for the 7.62 cm chord airfoil model used in these tests is presented without analysis. Descriptions of the 0.3-m TCT, the airfoil model, the test instrumentation, and the testing procedures are included.

Dress, D. A.↗
NASA NTRS1984

Low cycle fatigue behavior of conventionally cast MAR-M 200 AT 1000 deg C

The low cycle fatigue behavior of the nickel-based superalloy MAR-M 200 in conventionally cast form was studied at 1000 C. Continuous cycling tests, without hold times, were conducted with inelastic strain ranges of from 0.04 to 0.33 percent. Tests were also conducted which included a hold time at peak strain in either tension or compression. For the conditions studied, it was determined that imposition of hold times did not significantly affect the fatigue life. Also, for continuous cycling tests, increasing or decreasing the cycle frequency did not affect life. Metallographic analysis revealed that the most significant damage mechanism involved environmentally assisted intergranular crack initiation and propagation, regardless of the cycle type. Changes in the gamma morphology (rafting and rod formation) were observed, but did not significantly affect the failure.

Milligan, W. W.↗
NASA NTRS1982

Interaction between cast silicon properties and solar cell performance

Three types of cast silicon, Silso, HEM (Heat-Exchanger Method) and UCP (Ubiquitous Crystallization Process) were studied for their use as solar cells. Optical microscopy after etching revealed a high density of uniform dislocations (approaching 1,000,000/sq cm), lines of dislocations indicating stress during crystal growth, and precipitates, some of which generate dislocations. Solar cells were fabricated by three processes. Results of solar cell processing revealed that these materials produce cells of lower efficiency than Czochralski control cells, and that the efficiencies of the three materials were quite close. Diffusion length and spectral response data are shown. Certain structural features are correlated with solar cell efficiency, diffusion length, and spectral response. Electron-beam induced current (EBIC) and light spot scanning are used to back up other measurements.

Hyland, S.↗
NASA NTRS1984

Two-region analysis of interface shape in continuous casting with superheated liquid

A slab ingot is being formed as a continuous casting by withdrawal from a mold with parallel walls. The sides of the ingot below the mold are cooled to remove heat of fusion and energy transferred to the solidification interface by superheated liquid metal in the mold. A two-region analysis is made to determine the non-uniform heat conduction from the liquid metal to the interface, and then from the interface to the cooled ingot sides. The solidification interface shape is found that is compatible with the removal of fusion energy and nonuniform heating from the liquid. The solution is obtained by two applications of a Cauchy boundary value method.

Siegel, R.↗
NASA NTRS1986

Cast Iron With High Carbon Content

Method proposed for solidifying high-carbon cast iron without carbon particles segregating at upper surface. Solidification carried out in low gravity, for example on airplane flying free-fall parabolic trajectory. Many different microstructures obtained by proposed technique, and percentage by weight of carbon retained in melt much higher than at present.

Curreri, P. A.↗
NASA NTRS1986

Solidifying Cast Iron in Low Gravity

Report describes study of solidification of cast iron in low and normal gravity. Because flotation, sedimentation, and convection suppressed, alloys that solidify at nearly zero gravity have unusual and potentially useful characteristics. Study conducted in airplane that repeatedly flew along parabolic trajectories. Appears iron/carbon alloys made at low gravity have greater carbon content (as high as 5 to 10 percent) than those made of Earth gravity because carbon particles do not float to top of melt.

Hendrix, J. C.↗
NASA NTRS1984

The effects of Cr, Co, Al, Mo and Ta on the cyclic oxidation behavior of a prototype cast Ni-base superalloy based on a 2(5) composite statistically designed experiment

A series of cast Ni-base superalloys were systematically varied at selected levels of Co, Cr, Mo, Ta, and Al. The elemental levels varied were Mo, 0 to 4 percent; Cr, 6 to 18 percent; Co, 0 to 20 percent, Ta, 0 to 8 percent; and Al, 3.25 to 6.25 percent. The cyclic oxidation resistance was determined from specific weight change data as a function of time for 1 hr cycles in static air at 1100 C. The significant terms in decreasing order of their importance were Al, Ta, Cr2, Al-Cr, Cr-Co, Co2, Al-Mo, Cr-Mo, Al-Al, and Mo-Ta. The Al term alone accounted for close to 82 percent of the explained variability. The estimating equation showed that the Al level was the most important and should be at its 6.25 wt % maximum value. The Mo and Ta levels should also be at their maximum 4 and 8 wt % respectively. The cobalt composition should be as low as possible, i.e., 0 wt%. The Cr level optimum varies depending on the other 4 levels. The X-ray diffaction results indicate the most protective scales are alumina/aluminate spinel stabilizized with a tri-rutile oxide high in Ta and Mo.

Barrett, C. A.↗
NASA NTRS1985

MPS solidification model. Analysis and calculation of macrosegregation in a casting ingot

Work performed on several existing solidification models for which computer codes and documentation were developed is presented. The models describe the solidification of alloys in which there is a time varying zone of coexisting solid and liquid phases; i.e., the S/L zone. The primary purpose of the models is to calculate macrosegregation in a casting or ingot which results from flow of interdendritic liquid in this S/L zone during solidification. The flow, driven by solidification contractions and by gravity acting on density gradients in the interdendritic liquid, is modeled as flow through a porous medium. In Model 1, the steady state model, the heat flow characteristics are those of steady state solidification; i.e., the S/L zone is of constant width and it moves at a constant velocity relative to the mold. In Model 2, the unsteady state model, the width and rate of movement of the S/L zone are allowed to vary with time as it moves through the ingot. Each of these models exists in two versions. Models 1 and 2 are applicable to binary alloys; models 1M and 2M are applicable to multicomponent alloys.

Poirier, D. R.↗
NASA NTRS1985

Response of rat hindlimb muscles to 12 hours recovery from tail-cast suspension

Previous work has shown a number of biochemical changes which accompany atrophy or reduced muscle growth in hindlimb of tail-casted, suspended rats. These results clearly show that altered muscle growth was due to changes in protein turnover. Accordingly, the rise in soleus tyrosine following unloading reflects the more negative protein balance. Other major changes we found included slower synthesis of glutamine as indicated by lower ratios of glutamine/glutamate and reduced levels of aspartate which coincide with slower aspartate and ammonia metabolism in vitro. In conjunction with the study of SL-3 rats, which were subjected to 12 h of post-flight gravity, a study of the effects of 12 h eight bearing on metabolism of 6-day unloaded hindlimb muscles was carried out.

Tischler, M. E.↗
NASA NTRS1984

Backside damage-gettering in cast polycrystalline silicon

The technique of backside-damage gettering improves the performance of short minority-carrier diffusion length, large-grain (grain diameter greater than 1 to 2 mm), cast polycrystalline silicon. On average, increases of nearly 20 percent in short-circuit current, 10 mV in open-circuit voltage, and 15 percent in peak-power were obtained by heat-treating 300 micron thick polycrystalline wafers at 1000 C in flowing nitrogen for 5 hours. Additional measurements of the bulk and space-charge recombination current components indicate that this improvement results from a significant increase in the minority-carrier diffusion length due to gettering of impurities from the bulk.

Culik, J.↗
NASA NTRS1985

Control of solidification boundary in continuous casting by asymmetric cooling and mold offset

A solution, developed to obtain solidification-interface shapes for complex situations in which both the ingot cooling and mold geometry are asymmetric, is analyzed. The effect of mold offsett and of unequal ingot side temperatures on the interface shapes is illustrated in graphs. The results of the analysis show how the solidification interface in continuous casting can be controlled by asymmetries in both mold geometry and cooling of the ingot sides.

Siegel, R.↗
NASA NTRS1984

Solidification interface shape for continuous casting in an offset mold - Two analytical methods

A solution method for finding the unknown solidification interface in manufacturing slab ingots as a continuous casting is presented, which involves a product solution in the potential plane and the use of conjugate harmonic functions. It is argued that the method may be more direct for some geometries than the Cauchy boundary value method. Moreover, the usefulness of the Cauchy boundary value method is demonstrated through the example of a nonsymmetric horizontal mold where the walls are offset to support the lower ingot boundary.

Siegel, R.↗