SEARCH · Engineering Papers

Results for “slip”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 973 records · Page 54

All sources NASA NTRS DOE OSTI

NASA NTRS1985

Structure of ducted particle-laden turbulent jets

New and existing measurements have been used to develop and evaluate models of particle-laden jets and sprays, yielding encouraging results for a stochastic separated flow (SSF) model which treats effects of interphase slip and turbulence on the basis of random walk computations of particle or drop motion. An evaluation of the SSF model using the measurements of Modarress et al. (1982, 1983) yielded results comparable to earlier work, suggesting that data from coflowing jets in ducts should be accompanied by static pressure measurements, since even small pressure gradients appreciably influence jet properties.

Zhang, Q.-F.↗

NASA NTRS1985

Numerical simulation of transient inviscid gas flows in a shock tube

Time-dependent upwind high resolution schemes for solving the Euler equations were developed and applied to simulate 1-D and 2-D transient inviscid gas flows in a shock tube. Using obstacles of different geometries, a series of calculations were carried out to investigate the transient complex shock-wave diffraction phenomena. Shock-wave and objects interactions with shock Mach-number Ms ranging from 2 to 20 were considered. Comparison with analytical and available experimental results indicate good agreement. Display of detailed flow structures including multiple Mach shocks, slip surfaces, and vortex are also given.

Yang, J. Y.↗

NASA NTRS1985

A diffuse plate boundary model for Indian Ocean tectonics

It is suggested that motion along the virtually aseismic Owen fracture zone is negligible, so that Arabia and India are contained within a single Indo-Arabian plate divided from the Australian plate by a diffuse boundary. The boundary is a zone of concentrated seismicity and deformation commonly characterized as 'intraplate'. The rotation vector of Australia relative to Indo-Arabia is consistent with the seismologically observed 2 cm/yr of left-lateral strike-slip along the Ninetyeast Ridge, north-south compression in the Central Indian Ocean, and the north-south extension near Chagos.

Wiens, D. A.↗

NASA NTRS1985

Fracture of yttria-doped, sintered reaction-bonded silicon nitride

Flexural strength of an yttria-doped, slip-cast, sintered reaction-bonded silicon nitride was evaluated as a function of temperature (20 to 1400 C in air), applied stress, and time. Static oxidation at 700 to 1400 C was investigated in detail; in tests at 1000 C in air, the material showed anomalous weight gain. Flexural stress-rupture testing at 800 to 1200 C in air indicated that the material is susceptible to stress-enhanced oxidation and early failure. Fractographic evidence for time-dependent and -independent failures is presented.

Govila, R. K.↗

NASA NTRS1985

Is the Ventersdorp rift system of southern Africa related to a continental collision between the Kaapvaal and Zimbabwe Cratons at 2.64 Ga AGO?

Rocks of the Ventersdorp Supergroup were deposited in a system of northeast trending grabens on the Kaapvaal Craton approximately 2.64 Ga ago contemporary with a continental collision between the Kaapvaal and Zimbabwe Cratons. It is suggested that it was this collision that initiated the Ventersdorp rifting. Individual grabens strike at high angles toward the continental collision zone now exposed in the Limpopo Province where late orogenic left-lateral strike-slip faulting and anatectic granites are recognized. The Ventersdorp rift province is related to extension in the Kaapvaal Craton associated with the collision, and some analogy is seen with such rifts as the Shansi and Baikal Systems associated with the current India-Asia continental collision.

Burke, K.↗

NASA NTRS1984

Recombination-active defects in silicon ribbon and polycrystalline solar cells

This paper reports results from a study of recombination-active structural defects in silicon ribbon and polycrystalline solar cells using the electron beam induced current (EBIC) technique in a scanning electron microscope. It is demonstrated that low temperature EBIC measurements can reveal a range of defects that are not observable at room temperature, including slip dislocations in silicon dendritic web ribbons as well as decorated twin boundaries and dislocation complexes in cast polycrystalline silicon solar cell materials.

Cheng, L. J.↗

NASA NTRS1985

Hgi2 Sub 2 Crystal Growth for Nuclear Detectors

The objectives of this program are to obtain a benchmark quality sample grown at low-g conditions and to study vapor growth phenomena under space conditions. Ground-based crystals show a defect structure which impairs their performance as nuclear radiation detectors. These defects may be caused by the gravitational force acting on the crystal in its weakended state at the elevated growth temperature and by irregular convection patterns in the vapor during growth. Mechanical strength measurements have been performed (uniaxial compression tests) which show that the crystals exhibit slip parallel to the c-planes at stresses as low as 1/2 psi. Preliminary calculations using a simple linearized model indicate the oscillating instabilities in the convection part of the vapor transport system are unlikely, even at 1-g, provided that the utmost care is taken in the preparation of the crystal growth source material.

Schnepple, W. F.↗

NASA NTRS1985

Langley Research Center Standard for the Evaluation of Socket Welds

A specification utilized for the nondestructive evaluation of socket type pipe joints at Langley Research Center (LaRC) is discussed. The scope of hardware shall include, but is not limited to, all common pipe fittings: tees, elbows, couplings, caps, and so forth, socket type flanges, unions, and valves. In addition, the exterior weld of slip on flanges shall be inspected using this specification. At the discretion of the design engineer, standard practice engineer, Fracture Mechanics Engineering Section, Pressure Systems Committee, or other authority, four nondestructive evaluation techniques may be utilized exclusively, or in combination, to inspect socket type welds. These techniques are visual, radiographic, magnetic particle, and dye penetrant. Under special circumstances, other techniques (such as eddy current or ultrasonics) may be required and their application shall be guided by the appropriate sections of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (B&PVC).

Berry, R. F., Jr.↗

NASA NTRS1985

Calculation of particle dynamics effects on laser velocimeter data

In order to analytically assess the effects of particle dynamics on laser velocimeter measurements, the particle response to the fluid in which it is entrained must be modeled. The equation of particle motion derived at Arnold Engineering and Development Center (AEDC), is used to model the motion of the particle. The equation is derived from the Navier-Stokes equation under the assumption of unsteady Stokes flow. It should be noted that the Stokes flow eliminates the need for a far field boundary condition, and hence eliminates any normal (lift) forces. To extend the equation to higher particle slip velocities, the Stokes drag is replaced with the particle drag law, modified to include heat transfer effects. The drag coefficient accounts for inertial, rarefaction, compressibility, shape, and heat transfer effects.

Nichols, R. H.↗

NASA NTRS1985

Laser velocimetry measurement in a transonic tunnel

Some preliminary velocity measurements were carried out inside the transonic tunnel using the laser velocimeter (LV) system in association with the smoke generator. Pressure measurements were also performed using a pressure tap located on the side wall of the test section slightly upstream of the windows. Though the pressure measurements and the LV measurements were not taken at exactly the same location, extrapolation of the pressure data into the location of the LV measurements indicated a very close agreement between the velocity values obtained using the two different methods. Thus it is believed that the smoke particle is following the air flow with little or no velocity slip. Velocity measurements with airfoil at various angles of attack are now being carried out in conjuction with schlieren flow visualization. In the near future pressure distribution around and on the airfoil will be obtained by putting pressure taps on the side windows and using a pressure tap model (currently under construction) of the airfoil.

Ng, T. T.↗

NASA NTRS1983

Creep fatigue life prediction for engine hot section materials (isotropic)

The activities performed during the first year of the NASA HOST Program, Creep Fatigue Life Prediction for Engine Hot Section Materials (Isotropic), being conducted by Pratt & Whitney Aircraft are summarized. The program is a 5 year, two part effort aimed at improving the high temperature crack initiation prediction technology for gas turbine hot section components. Significant results of the program produced thus far are discussed. Cast B1900 + Hf and wrought IN 718 were selected as the base and alternate materials, respectively. A single heat of B1900 + Hf was obtained and test specimens fabricated. The material was characterized with respect to grain size, gamma prime size, carbide distribution, and dislocation density. Monotonic tensile and creep testing has shown engineering properties within anticipated scatter for this material. Examination of the tensile tests has shown a transition from inhomogeneous planar slip within the grains at lower temperatures to more homogeneous matrix deformation. Examination of the creep tests has shown a transgranular failure mode at 1400 F and an intergranular failure mode at 1600 F and 1800 F.

Moreno, V.↗

NASA NTRS1984

Mod-5A Wind Turbine Generator Program Design Report. Volume 4: Drawings and Specifications, Book 1

The design, development and analysis of the 7.3 MW MOD-5A wind turbine generator is documented. Volume 4 contains the drawings and specifications that were developed in preparation for building the MOD-5A wind turbine generator. This is the first of five books of volume four. It contains structural design criteria, generator step-up transformer specs, specs for design, fabrication and testing of the system, specs for the ground control enclosure, systems specs, slip ring specs, and control system specs.

Source record↗

NASA NTRS1986

Pressure distributions obtained on a 0.10-scale model of the space shuttle Orbiter's forebody in the AEDC 16T propulsion wind tunnel

Pressure distribution test data obtained on a 0.10-scale model of the forward fuselage of the Space Shuttle Orbiter are presented without analysis. The tests were completed in the AEDC 16T Propulsion Wind Tunnel. The 0.10-scale model was tested at angles of attack from -2 deg to 18 deg and angles of side slip from -6 to 6 deg at Mach numbers from 0.25 to 1/5 deg. The tests were conducted in support of the development of the Shuttle Entry Air Data System (SEADS). In addition to modeling the 20 SEADS orifices, the wind-tunnel model was also instrumented with orifices to match Development Flight Instrumentation (DFI) port locations that existed on the Space Shuttle Orbiter Columbia (OV-102) during the Orbiter Flight Test program. This DFI simulation has provided a means of comparisons between reentry flight pressure data and wind-tunnel and computational data.

Siemers, P. M., III↗

NASA NTRS1985

High purith low defect FZ silicon

The most common intrinsic defects in dislocation-free float zone (FZ) silicon crystals are the A- and B-type swirl defects. The mechanisms of their formation and annihilation have been extensively studied. Another type of defect in dislocation-free FZ crystals is referred to as a D-type defect. Concentrations of these defects can be minimized by optimizing the growth conditions, and the residual swirls can be reduced by the post-growth extrinsic gettering process. Czochralski (Cz) silicon wafers are known to exhibit higher resistance to slip and warpage due to thermal stress than do FZ wafers. The Cz crystals containing dislocations are more resistant to dislocation movement than dislocated FZ crystals because of the locking of dislocations by oxygen atoms present in the Cz crystals. Recently a transverse magnetic field was applied during the FZ growth of extrinsic silicon. Resultant flow patterns, as revealed by striation etching and spreading resistance in Ga-doped silicon crystals, indicate strong effects of the transverse magnetic field on the circulation within the melt. At fields of 5500 gauss, the fluid flow in the melt volume is so altered as to affect the morphology of the growing crystal.

Kimura, H.↗

NASA NTRS1986

Effect of additional heat treatment of 2024-T3 on the growth of fatigue crack in air and in vacuum

In order to determine the influence of ductility on the fatigue crack growth rate of aluminum alloys, fatigue tests were carried out on central notched specimens of 2024-T3 and 2024-T8 sheet material. The 2024-T8 material was obtained by an additional heat treatment applied on 2024-T3 (18 hours at 192 C), which increased the static yield strength from 43.6 to 48.9 kgf/sq mm. A change in the ultimate strength was not observed. Fatigue tests were carried out on both materials in humid air and in high vacuum. According to a new crack propagation model, crack extension is supported to be caused by a slip-related process and debonding triggered by the environment. This model predicts an effect of the ductility on the crack growth rate which should be smaller in vacuum than in humid air; however, this was not confirmed. In humid air the crack-growth rate in 2024-T8 was about 2 times faster than in 2024-T3, while in vacuum the ratio was about 2.5. Crack closure measurements gave no indications that crack closure played a significant role in both materials. Some speculative explanations are briefly discussed.

Louwaard, E. P.↗

NASA NTRS1986

Transpression as the main deformational event in an Archaean greenstone belt, northeastern Minnesota

Deformed and metamorphosed sedimentary and volcanic rocks of the Vermilion district constitute an Archean greenstone belt trending east-west between higher grade rocks of the Vermilion Granitic Complex to the north and the Giants Range batholith to the south. Metamorphic grade is low throughout, being lowest in the center of the belt (chlorite zone of the greenschist facies). All the measured strain, a cleavage or schistosity, and a mineral lineation in this belt are attributed to the main phase of deformation D sub 2 that followed an earlier nappe-forming event D sub 1, which left little evidence of penetrative fabric. Previous work assumed that the D sub 2 deformation resulted from north-south compression across the district. It is now believed that a significant component of this deformation resulted from dextral shear across the whole region. Thus the Vermilion fault, a late-state largely strike-slip structure that bounds the Vermilion district to the north, may simply be the latest, most brittle expression of a shear regime that was much more widespread in space and time. Features that are indicative of shear include ductile shear zones with sigmoidal foliation patterns, highly schistose zones with the development of shear bands, feldspar clasts or pyrite cubes with asymmetric pressure shadows, and the fact that the asymmetry of the F sub 2 folds is predominantly Z for at least 15 km south of the Vermilion fault.

Hudleston, P. J.↗

NASA NTRS1986

Commentary on the 1985 NASA/Vanderbilt Symposium on Future Hypervelocity Flight Requirements

The discussion, started in Semiannual Status Report Number 1, on aerothermal problems of hypervelocity flight and experiments that may lead to significant improvements in analytical/computational predictive methods, continues. The commentary is based on presentations made by speakers at a symposium on this subject held in December 1985. Symposium participants focused on the serious deficiencies that exist in knowledge of real-gas, nonequilibrium thermochemical-kinetic processes, catalytic processes, surface and shock slip, gas/surface interaction, boundary layer transition, and vortical leeside flows under hypervelocity conditions. Programs of laboratory research and computations leading toward in-flight experiments were recommended. Feasibility of appropriate measurement techniques for the flight environment was assessed and problems for study in that area identified. A synopsis of the oral presentations is given.

Potter, J. L.↗

NASA NTRS1985

Discussion of flight experiments with an entry research vehicle

The focus of interest is the maneuvering flight of advanced entry vehicles operating at altitudes above 50 km and at velocities of 5 to 8 km/s. Information resulting in more accurate aerodynamic analysis is sought and measurement techniques that appear to be applicable are identified. Measurements discussed include: shock layer or boundary layer profiles of velocity, temperature, species mass fractions, and other gas properties associated with aerodynamic heating; surface energy transfer process; nonequilibrium flow processes and pressure distribution; separated, vortic leeside flow of nonequilibrium fluid; boundary layer transition on highly swept configurations; and shock and surface slip and gas/surface interaction. Further study should focus on evolving measurement techniques, installation requirements, and on identification of the portions of flights where successful results seem probable.

Potter, J. L.↗