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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Tribological properties of structural ceramics

The tribological and lubricated behavior of both oxide and nonoxide ceramics are reviewed in this chapter. Ceramics are examined in contact with themselves, other harder materials and metals. Elastic, plastic and fracture behavior of ceramics in solid state contact is discussed. The contact load necessary to initiate fracture in ceramics is shown to be appreciably reduced with tangential motion. Both friction and wear of ceramics are anisotropic and relate to crystal structure as has been observed with metals. Grit size effects in two and three body abrasive wear are observed for ceramics. Both free energy of oxide formation and the d valence bond character of metals are related to the friction and wear characteristics for metals in contact with ceramics. Surface contaminants affect friction and adhesive wear. For example, carbon on silicon carbide and chlorine on aluminum oxide reduce friction while oxygen on metal surfaces in contact with ceramics increases friction. Lubrication increases the critical load necessary to initiate fracture of ceramics both in indentation and with sliding or rubbing. Ceramics compositions both as coatings and in composites are described for the high temperature lubrication of both alloys and ceramics.

Buckley, Donald H.↗
NASA NTRS1985

Elastic-plastic deformation of a metal-matrix composite coupon with a center slot

A comprehensive experimental analysis of deformations of the surface of a metal-matrix specimen is reported. The specimen is a 6-ply 0 + or - 45 sub s boron-aluminum tensile coupon with a central slot. Moire interferometry is used for high-sensitivity whole-field measurements of in-plane displacements. Normal and shear strains are calculated from displacement gradients. Displacement fields are analyzed at various load levels from 15% to 95% of the failure load. Deformations of the boron fibers could be distinguished from those of the matrix. Highly localized plastic slip zones occur tangent to the ends of the slot. Shear strains and concurrent transverse compressive strains in the slip zones reach approximately 10% and 1%, respectively. Upon unloading, elastic recovery in surrounding regions causes a reverse plastic shear strain in the slip zone of about 4%. Longitudinal normal strains on the unslotted ligament peak at the slot boundary at about 1% strain. The strain concentration factor at the end of the slot decreases with load level and the advance of plasticity.

Post, D.↗
NASA NTRS1966

Nonspace technology resulting from the NASA FLUID connector programs

Leakage at static seals is a problem common to both NASA and industry. The subject of an intensive investigation has been the establishing of design criteria for reliable, low-weight, leak-tight fluid connectors. The problem has been broken into areas of investigation: the structure which supports the actual seal and the seal itself. A Separable Connector Design Handbook has been written to direct designers' efforts toward the optimum connector design for a given purpose. Included in this paper is a brief discussion of the topics covered in the Handbook, notable flanged connector design, threaded connector design, pressure energized seal design, leakage measurement techniques, and a catalog of current satisfactory seal configurations. Also included in this paper is a discussion of the principles of sealing, including the uses and characteristics of elastomers, plastics, and metals. The load-leakage characteristics of seals, the effect of internal pressure, the effect of surface finish on the leakage rate, the mode of material deformation under load, and the advantages of various seal configurations are discussed.

Sealing↗
NASA NTRS1969

Generation of sonic power during welding

Generation of intense sonic and ultrasonic power in the weld zone, close to the puddle, reduces the porosity and refinement of the grain. The ac induction brazing power supply is modified with long cables for deliberate addition of resistance to that circuit. The concept is extensible to the molding of metals and plastics.

Mc Campbell, W. M.↗
NASA NTRS1969

High-pressure seals for rotary shafts

High pressure seals for rotating shafts are machined from a polyimide resin. It is more durable and cheaper than the older seals of plastic coated metal and works at temperatures between - 400 degrees and plus 900 degrees f.

Holden, C. P.↗
NASA NTRS1971

Experiment S012: Micrometeorite collection

The micrometeorite activity in a near-earth environment and the effect of the environment on microorganisms were studied by exposure of polished metal and plastic surfaces to the environment outside the Gemini spacecraft. Preliminary results are summarized as follows: (1) The cumulative influx rate in the size ranges from 10 to the minus 15th power to 10 to the minus 14th power gram was approximately 2 particles/ sq m/sec, as determined on the Gemini 12 mission; (2) The cumulative influx rate in the same mass range, as determined by the data from the Gemini 9 mission was almost 200 particles/ sq m/sec; and (3) The large particle cumulative influx rate was about 3 x 0.00001 particle/ sq m/sec, with a mass of the order of 10 to the minus 7th power gram. No living organisms could be found on the sterile collecting surfaces after recovery and handling.

Hemenway, C. L.↗
NASA NTRS1972

Life prediction of expulsion bladders through fatigue test and fold strain analysis.

Consideration of the problem of reducing the probability of mechanical failure of bladder systems used for the expulsion of propellants into liquid rocket engines. It is shown that individual local folds in collapsing bladders can be classified into single and double folds, specifiable by nondimensional geometrical parameters which directly define the maximum strains at these folds. From these maximum strains the number of collapse/inflation cycles to failure can be obtained from low-cycle fatigue data experimentally determined for the bladder material of interest. Cycle life data are presented in terms of true maximum strain for four metals, two plastics, and two elastomers. It is found that double folds give rise to much more severe folding strains than do simple folds.

Chu, H. N.↗
NASA NTRS1974

Detection of cracks in surface insulation

Volatile organic liquid surface penetrants used with appropriate detector paper leave tested surfaces uncontaminated. Method can be used to detect minute cracks in materials such as metal, glass, plastics, ceramics, etc.

Leger, L. J.↗
NASA NTRS1973

Measurements of heavy solar wind and higher energy solar particles during the Apollo 17 mission

The lunar surface cosmic ray experiment, consisting of sets of mica, glass, plastic, and metal foil detectors, was successfully deployed on the Apollo 17 mission. One set of detectors was exposed directly to sunlight and another set was placed in shade. Preliminary scanning of the mica detectors shows the expected registration of heavy solar wind ions in the sample exposed directly to the sun. The initial results indicate a depletion of very-heavy solar wind ions. The effect is probably not real but is caused by scanning inefficiencies. Despite the lack of any pronounced solar activity, energetic heavy particles with energies extending to 1 MeV/nucleon were observed. Equal track densities of approximately 6000 tracks/cm sq 0.5 microns in length were measured in mica samples exposed in both sunlight and shade.

Walker, R. M.↗
NASA NTRS1974

Method of laminating structural members

A laminate is obtained by providing a lightweight core material, such as a honeycombed plastic or metal, within the cavity defined by an annular mold cavity frame. Face sheets, which are to be bonded to the core material, are provided on opposite sides of the frame and extend over the frame, thus sealing the core material in the cavity. An adhesive is provided between the core material and the face sheets and the combined thickness of the core material and adhesive is a close fit within the opposed face sheets. A gas tight seal, such as an O-ring gasket, is provided between the frame and the face sheet members to form a gas tight cavity between the face sheet members and the frame. External heat and pressure are used to bond the face sheets to the core material. Gas pressure is introduced into the sealed cavity to minimize out-gasing of the adhesive.

Heier, W. C.↗
NASA NTRS1975

Quick-change absorption column

Column has end caps held in place by springs; prefilled packs of absorbent can be exchanged quickly. Both ends of metal or plastic body tube of size which can hold adequate amount of absorbent are machined to provide seat for perforated plate and groove for its spring retainer ring.

Mcewen, G. N., Jr.↗
NASA NTRS1979

Preparing thin aluminum films for adhesive bonding

Carbonate pretreatment produces highly bondable surface without harming film. Treatment is useful in developing low-cost mirrors and solar concentrators fabricated from metal-coated plastic films. Treatment should cost no more than standard degreasing and rinsing procedures.

Smith, T.↗