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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 1,297 records · Page 72
All sourcesNASA NTRSDOE OSTI
NASA NTRS1967

Dynamical friction.

Chandrasekhar dynamical friction theory for star in cluster adapted to Fokker-Plank electron in two-component plasma theory and including multiple encounters

STAR CLUSTER↗
NASA NTRS1952

Experimental Investigation of Eccentricity Ratio, Friction, and Oil Flow of Short Journal Bearings

An experimental investigation was conducted to obtain performance data on bearings of length-diameter ratios of 1, 1/2, and 1/4 for comparison with theoretical curves. A 1.375-inch-diameter bearing was tested at speeds up to 6000 rpm and with unit loads from 0 to 900 pounds per square inch. Experimental data for eccentricity ratio and friction followed single lines when plotted against a theoretically derived capacity number, which is equal to Sommerfeld number times the square of the length-diameter ratio. The form of the capacity number indicates that under certain conditions the eccentricity ratio is theoretically independent of bearing diameter. A method of plotting oil flow data as a single line is shown. Methods are also discussed for approximating a maximum bearing temperature and evaluating the effect of deflection or misalignment on the eccentricity ratio at the ends of the bearings.

BEARINGS, SLEEVE↗
NASA NTRS2006

Reaction force of percussive corer, rotary-friction corer, and rotary-percussive corer

Future NASA exploration missions will increasingly require sampling, in-situ analysis and possibly the return of material to Earth for laboratory analysis. To address these objective, effective and optimized drilling techniques are needed. This requires developing comprehensive tools to be able to determine analytically what takes place during the operation and what are the control parameters that can be enhanced. In this study, three types of coring techniques were studied and were identified as potential candidates for operation from a possible future Mars Sample Return (MSR) mission rover. These techniques include percussive, rotary-friction, and rotary-percussive coring. Theoretical models were developed to predict the dynamic reaction forces transmitted from these three types of corers to the robotic arms that hold them. The predicted reaction forces will then be used in a dynamic simulation environment to simulate a representative corer tool to obtain a best estimate of a tool that can be operated from a small rover. The predicted dynamic reaction forces will be presented in this paper.

Ultrasonic Percussive corer↗
NASA NTRS2022

Friction Stir Welded Aluminum-Lithium (Al-Li) 2050 Blanks for Spin Forming

Spin forming is a metalworking process used to produce axially-symmetric parts by the application of lateral pressure from a forming tool to a circular blank mounted on a revolving, heated mandrel. This process enables production of cones, domes, or caps that can incorporate features such as flat bulkheads. Friction stir welded (FSW) Al-Li 2195 blanks have been spin formed for single-piece, launch vehicle domes up to 5 m in diameter. Al-Li 2050 plate has the advantage of availability up to 165 mm thick,whereas 2195 plate is traditionally only available up to 57 mm thick. Increased plate thickness enables greater design flexibility for machining of taller structural elements, such as stiffeners. However, 2050 is only available in plate widths up to ~3.9 m. This study demonstrated the capability of making custom 2050 blanks for spin forming large (>7.8 m in diameter), single-piece, light-weight flight articles (e.g., lunar habitats and landers) by FSW two (or more) plates together. Spin forming of welded 2050 blanks has not been attempted before this investigation. The objective was to evaluate the mechanical properties of 2050 parent material and FSW regions after spin forming and subsequent T6 heat treatment. A 3 m diameter x 38 mm thick 2050 blank was fabricated from two 1.5 m wide pieces by FSW and subsequently spin formed into a cone article. Additionally, three 1.2 m diameter x 8.1 mm thick 2050 blanks were produced by FSW and spin formed into subscale cone articles with varying strain input. Mechanical properties are reported for spin formed 2050-T6 parent material and FSW regions on the articles. Abnormal grain growth (AGG) in the FSW during heat treatment was expected based on prior experience with 2195. Implementation of an AGG suppression strategy during heat treatment reduced AGG in the FSW regions and improved ductility.

Spin forming↗