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At least 721 records · Page 40

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NASA NTRS1982

Feasibility of SPF/DB titanium sandwich for LFC wings

The feasibility of fabricating SPF/DB titanium structures of sufficient smoothness to be used for laminar flow wing surfaces was demonstrated. Two methods of fabricating panels which meet the surface smoothness criteria were demonstrated. The first consists of superplasticity forming/diffusion bonding a panel using steel dies, then machining the surface to the required flatness and finish after forming. This approach, however, was estimated to be more costly than the second approach, in which the panel is formed against ceramic platens which produce the desired surface smoothness without subsequent finishing. Four panels were fabricated, and their surface quality was evaluated. The specified criteria for waviness compared with actual measured values on the panels is shown. The acceptable surface quality as well as feasibility of the laminar flow control surface design, in which separate strips incorporating the boundary layer bleed provisions are bonded into slots on the surface, was also demonstrated.

Mcquilkin, F. T.↗

NASA NTRS1982

Gas-phase hydrogen permeation through alpha-titanium - Surface film and dimensional effects

The process of hydrogen transport through alpha-Ti involves simultaneous diffusion and phase boundary reactions at both surfaces, with the relative effect on each surface depending on the extent of surface contamination as well as the physical dimensions of the titanium membrane used. It is shown by the present study that hydrogen permeation in commercially pure alpha-Ti increases exponentially with temperature and is dependent on the first power of the input pressure, whether the surface is as-polished, preoxidized or prenitrided. Permeation decreases in the case of the as-polished condition if nitride or oxide films are formed at the surface in contact with source hydrogen, while increasing slightly for the same condition if such films are formed at the hydrogen exit surface.

Shah, K. K.↗

NASA NTRS1982

Service evaluation of Aluminum-Brazed Titanium (ABTi) jet engine tailpipe extensions

Aluminum-brazed titanium (ABTi) jet engine tailpipe extensions were evaluated in commercial service over a 3-year period. The purpose of the evaluation was to determine the corrosion resistance of ABTi in acoustic applications (i.e., honeycomb sandwich incorporating a perforated inner skin). The results showed that ABTi does not have acceptable corrosion resistance in acoustic applications under severe operating conditions, but may be acceptable for acoustic applications in less severe environments.

Elrod, S. D.↗

NASA NTRS1982

A critical study of the role of the surface oxide layer in titanium bonding

The molecular understanding of the role which the surface oxide layer of the adherend plays in titanium bonding is studied. The effects of Ti6-4 adherends pretreatment, bonding conditions, and thermal aging of the lap shear specimens were studied. The use of the SEM/EDAX and ESCA techniques to study surface morphology and surface composition was emphasized. In addition, contact angles and both infrared and visible reflection spectroscopy were used in ancillary studies.

Dias, S.↗

NASA NTRS1983

Cavitation Erosion of Copper, Brass, Aluminum and Titanium Alloys in Mineral Oil

The variations of the mean depth of penetration, the mean depth rate of penetration, MDRP, the pit diameter 2a and depth h due to cavitation attack on Al 6061-T6, Cu, brass of composition Cu-35Zn-3Pb and Ti-5A1-2.5Sn are presented. The experiments are conducted in a mineral oil of viscosity 110 CS using a magnetostrictive oscillator of 20 kHz frequency. Based on MDRP on the materials, it is found that Ti-5Al-2.5Sn exhibits cavitation erosion resistance which is two orders of magnitude higher than the other three materials. The values of h/a are the largest for copper and decreased with brass, titanium, and aluminum. Scanning electron microscope studies show that extensive slip and cross slip occurred on the surface prior to pitting and erosion. Twinning is also observed on copper and brass.

Rao, B. C. S.↗

NASA NTRS1980

Fabrication and evaluation of brazed titanium-clad borsic/aluminum skin-stringer panels

A successful brazing process was developed and evaluated for fabricating full-scale titanium-clad Borsic/aluminum skin-stringer panels. A panel design was developed consisting of a hybrid composite skin reinforced with capped honeycomb-core stringers. Six panels were fabricated for inclusion in the program which included laboratory testing of panels at ambient temperatures and 533 K (500 F) and flight service evaluation on the NASA Mach 3 YF-12 airplane. All panels tested met or exceeded stringent design requirements and no deleterious effects on panel properties were detected followng flight service evaluation on the YF-12 airplane.

Bales, T. T.↗

NASA NTRS1983

Stress-corrosion crack-growth study of titanium alloy Ti-6Al-4V exposed to freon PCA and nitrogen tetroxide MON-1

An experimental fracture mechanics program was performed to determine the stress corrosion crack growth sensitivity of the propellant tank material, titanium alloy Ti-6Al-4V, for aerospace satellite applications involving long term exposure to Freon PCA and nitrogen tetroxide MON-1. Sustained load tests were made at a 49 C (120 F) constant temperature using thin gauge tensile test specimens containing semielliptical surface flaws. Test specimen types included parent metal, center of weld, and weld heat affected zone. It was concluded that Ti-6Al-4V alloy is not adversely affected in a stress environment when exposed to Freon PCA for 1000 hours followed by exposure to nitrogen tetroxide MON-1 for 2000 hours at stress levels up to 80% of the experimental critical plane strain stress intensity factor.

Bjorklund, R. A.↗

NASA NTRS1982

Surface characterization and failure analysis of thermally aged, polyimide bonded titanium

This study of high temperature stable adhesive systems using 6Al-4V titanium adherends found that certain adhesive/adherends exhibit a change from cohesive to adhesive failure mode during long term 450 F thermal aging. Lap-shear specimens which exhibited adhesive failures were subjected to failure analysis using scanning transmission electron microscopy (STEM) and surface analysis techniques. Data is presented which supports the conclusion of interfacial failures for these samples.

Peters, P. D.↗

NASA NTRS1983

Interaction of hydrogen chloride and water with oxide surfaces. III - Titanium dioxide

The adsorption of hydrogen chloride and water vapors on five TiO2 powders in both the anatase and rutile crystalline forms was studied as a function of temperature, pressure, and outgas conditions. The adsorbents were characterized utilizing X-ray powder diffraction, scanning electron microscopy, surface area analysis, indicator method, microelectrophoresis, XPS, and infrared spectroscopy. It was found that both outgas temperature and adsorption temperature influenced the adsorption of water vapor on TiO2, while water vapor adsorption on TiO2 was completely reversible. It is argued that the number of hydroxyl groups present on the surface determines the adsorption capacity of water on the different titanium dioxides. It was found that heats of immersion in water were affected significantly by outgas temperature. Hydrogen chloride adsorption isotherms at 30 C measured on TiO2 after outgassing at 100-400 C showed that a part of the total HCl adsorbed was irreversibly adsorbed. The highest HCl adsorption capacity per unit area was exhibited by anatase, while pure rutile exhibited the lowest adsorption capacity.

Siriwardane, R. V.↗

NASA NTRS1983

Origin of lunar meteorite ALHA 81005 - Clues from the presence of terrae clasts and a very low-titanium mare basalt clast

Attention is given to the endogenous (or primary) lithologies of the lunar crust that can be inferred from the terrae clasts and to the significance of a fragment of very low titanium (VLT) mare basalt in thin section, ALHA 81005,9. Fragments of the norite and harzburgite have mineral compositions similar to that of ferroan anorthosite, and a clast of ferroan anorthosite has pyroxenes with lower molar Mg/(Mg+Fe) than in known pristine rocks. It is inferred that the Mg-suite protoliths for the clasts of intermediate composition are magnesian troctolites, spinel troctolites, and feldspathic lherzolites. Whereas clasts of these lithologies are not present in ALHA 81005,9, mineral fragments from them are. Based on the molar Mg/(Mg+Fe) ratio and Cr content of its pyroxenes, a single basaltic clast is determined to be of mare origin. The composition of its plagioclase and the molar Ti/(Ti+Cr) ratios of its pyroxenes suggest that the clast is a fragment of VLT mare basalt. It is noted that if this basalt is significantly younger than the last basin-forming impact event, which was approximately 3.9 x 10 to the 9th years ago, then its presence probably constrains the source crater for ALHA 81005 to be within a hundred kilometers of a VLT mare basalt flow.

Treiman, A. H.↗

NASA NTRS1985

Sorting Titanium Welding Rods

Three types of titanium welding wires identified by their resistance to current flow. Welding-wire tester quickly identifies unknown titaniumalloy wire by touching wire with test probe, and comparing meter response with standard response. Before touching wire, tip of test probe dipped into an electrolyte.

Ross, W. D., Jr.↗

NASA NTRS1984

Re-design and fabrication of titanium multi-wall Thermal Protection System (TPS) test panels

The Titanium Multi-wall Thermal Protection System (TIPS) panel was re-designed to incorporate Ti-6-2-4-2 outer sheets for the hot surface, ninety degree side closures for ease of construction and through panel fastness for ease of panel removal. Thermal and structural tests were performed to verify the design. Twenty-five panels were fabricated and delivered to NASA for evaluation at Langley Research Center and Johnson Space Center.

Blair, W.↗

NASA NTRS1984

Flight service evaluation of two aluminum-brazed titanium spoilers

The long-term service evaluation of two aluminum-brazed titanium (ABTi) honeycomb flight spoilers was concluded. The two spoilers had about 7.5 years of commercial flight experience on All Nippon Airways Model 737 aircraft. All Nippon Airways was selected because Japan has one of the most severe marine-industrial environments in the world. The results indicated that both flight spoilers still had the same load-carrying capability as when they were originally installed. No direct evidence of any corrosion was observed on either spoiler. Another significant accomplishment of this effort was the development of a braze design for efficiently distributing point loads from the fittings and skin into the honeycomb core.

Boyer, R. R.↗

NASA NTRS1984

Friction behavior of silicon in contact with titanium, nickel, silver and copper

Sliding friction experiments are conducted with the semiconductor silicon in contact with the metals titanium, nickel, copper, and silver. Sliding is on the (111) plane of single-crystal silicon in the 112 crystallographic direction both in dry and lubricated (mineral oil) sliding. The friction coefficient in dry sliding is controlled by adhesion and the surface chemical activity of the metal. The more active the metal the stronger the adhesion and the higher the friction. In lubricated sliding the lubricant absorbs to the surfaces and reduces the importance of metal chemical effects. In lubricated sliding, silicon ceases to behave in a brittle manner and undergoes plastic deformation under load.

Mishina, H.↗

NASA NTRS1983

Apollo 14 very low titanium glasses - Melting experiments in iron-platinum alloy capsules

This paper describes two techniques that have been developed to produce Fe-Pt alloy capsules for hgh-pressure experiments, and reports liquidus-phase relations of the Apollo 14 very low titanium glasses determined using Fe-rich capsules (a/Fe/ approximately 0.6). The liquid is multiply saturated with olivine and clinopyroxene at equal to or greater than 22 kbar. The multiple saturation is at least 3 kbar higher than that determined using pure Fe capsules and corresponds to a source region at least 60 km deeper if olivine and clinopyroxene were the residual phases. However, independent data on iron activity or oxygen fugacity of the glasses are still needed in order to choose a container of optimum composition. Preliminary experiments in Fe-poor alloy capsules suggest that the valence state of iron and the crystallization sequence in the melt have changed, possibly as a result of oxidizing materials entrapped during the iron-plating processes. The FeO content of the charge decreases linearly with increasing run duration in experiments using pure Fe capsules. The observation that iron-rich globules grow with time suggests that the equilibrium Fe (bleb) + Fe2O3 (liq) = 3 FeO (liq) might be established in the liquid at high pressure. If this explanation is correct, an appreciable amount of 'FeO' in the liquid could actually be Fe2O3, and some natural lunar volcanic glasses may contain ferric iron as well.

Chen, H.-K.↗

NASA NTRS1985

Geosynchronous Performance of a Lithium-titanium Disulfide Battery

An ambient temperature rechargeable Lithium-Titanium disulfide (Li-TiS2) five cell battery has completed the first orbital year of accelerated synchronous orbit testing. A novel charge/discharge, state of charge (SOC) control scheme is utilized, together with taper current charge backup to overcome deleterious effects associated with high end of charge and low end of discharge voltages. It is indicated that 10 orbital years of simulated synchronous operation may be achieved. Preliminary findings associated with cell matching and battery performance are identified.

Otzinger, B.↗

NASA NTRS1984

An X-ray diffraction study of titanium oxidation

Titanium specimens of commercial purity were exposed at 1100 to 1400 F to laboratory air for times up to 100 hours. The extent of substrate contamination by interstitial oxygen was was determined by a new X-ray diffraction analysis involving transformation of X-ray diffraction intensity bands. The oxygen solid-solubility at the oxide-metal interfaces and its variation with time at temperature were also determined. Diffusion coefficients are deduced from the oxygen depth profiles.

Wiedemann, K. E.↗

NASA NTRS1985

Explosive Welding of Aluminum, Titanium and Zirconium to Copper Sheet Metal

The main material properties affecting the explosive weldability of a certain metal combination are the yield strength, the ductility, the density and the sonic velocity of the two metals. Successful welding of the metal combination depends mainly on the correct choice of the explosive welding parameters; i.e., the stand off distance, the weight of the explosive charge relative to the weight of the flyer plate and the detonation velocity of the explosive. Based on the measured and the handbook values of the properties of interest, the explosive welding parameters were calculated and the arrangements for the explosive welding of the Al alloy 6061-T6, titanium and zirconium to OFHC copper were determined. The relatively small sheet metal thickness (1/8") and the fact that the thickness of the explosive layer must exceed a certain minimum value were considered during the determination of the explosive welding conditions. The results of the metallographic investigations and the measurements of the shear strength at the interface demonstrate the usefulness of these calculations to minimize the number of experimental trials.

Hegazy, A. A.↗