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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1970

Improved electron beam welding technique

Energy transferred from the source to the workpiece is maximized by relying on the mobility of the material in its liquid phase. This permits more beam energy to transfer to the weld front.

Schumaker, B. W.↗
NASA NTRS1980

Verifying root fusion in electron-beam welds

Ultrasonic equipment and x-y recorder indicate where back side of joint is properly welded. Wire waveguide placed in groove at root of joint to be welded is fused when joint is adequately penetrated. Ultransonic signal moving down waveguide is reflected where guide is melted. Change in reflected-signal arrival time with change in weld-head position is nearly constant unless joint is incompletely penetrated. Method permits determination of penetration depth in preweld samples without opening vacuum chamber and sectioning weld. Technique is particularly valuable when back side of joint is inaccessible.

Becker, F. L.↗
NASA NTRS1998

An Assessment of Molten Metal Detachment Hazards for Electron Beam Welding in the Space Environment: Analysis and Test Results

Conditions under which molten metal detachments might occur in a space welding environment are analyzed. A weld pool detachment parameter specifying conditions for pool detachment by impact is derived and corroborated by experimental evidence. Impact detachment for the pool is unlikely. Impact detachment for a drop of metal on the end of the weld wire may be possible under extreme conditions. Other potential causes of molten metal detachment considered, vaporization pressure forces and wire flickout from the pool, did not appear to present significant detachment threats.

Nunes, A. C., Jr.↗
NASA NTRS1978

Automated space fabrication of structural elements

A description is presented of an automated space fabrication technique for basic structural elements, taking into account as representative the design loads and requirements of the solar power satellite structure. Roll forming for continuous cap and brace members is applicable for all proposed metallic materials. Spot-welding, electron beam welding, ultrasonic welding, laser welding, cold welding, and various mechanical fastening techniques are applicable for the automated fabrication process. Termination of the formed cap and brace members can be accomplished by sawing, shearing, punching, and laser cutting. The most cost effective materials were found to be the aluminum alloys. Selected for further study were AL20224T3 and AL2219-T62. In the area of fiber composites, thermoplastic matrix materials with graphite fibers were selected for future studies.

Engler, E. E.↗
NASA NTRS1980

Welding multiple plies with an electron beam

Method for electron-beam welding of multi-ply metal sheets eliminates ply separation and minimizes porosity. Method was developed for assembling bellows made of four plies of iron/nickel alloy sheets. Method consists of making successive stitch welds with electron beam until weld seam is completely filled in and all plies have been penetrated.

Kiluk, F. J.↗
NASA NTRS1999

Prediction and Measurement of X-Ray Spectral and Intensity Distributions from Low Energy Electron Impact Sources

In-vacuum electron beam welding is a technology that NASA considered as a joining technique for manufacture of space structures. The interaction of energetic electrons with metal produces x-rays. The radiation exposure to astronauts performing the in-vacuum electron beam welding must be characterized and minimized to insure safe operating conditions. This investigation characterized the x-ray environment due to operation of an in-vacuum electron beam welding tool. NASA, in a joint venture with the Russian Space Agency, was scheduled to perform a series of welding in space experiments on board the United States Space Shuttle. This series of experiments was named the International Space Welding Experiment (ISWE). The hardware associated with the ISWE was leased to NASA, by the Paton Welding Institute (PWI) in Ukraine, for ground based welding experiments in preparation for flight. Two tests were scheduled, using the ISWE electron beam welding tool, to characterize the radiation exposure to an astronaut during the operation of the ISWE. These radiation exposure tests consisted of Thermoluminescence Dosimeters (TLD's) shielded with material currently used by astronauts during Extra Vehicular Activities (EVA) and exposed to x-ray radiation generated by operation of an in-vacuum electron beam welding tool. This investigation was the first known application of TLD's to measure absorbed dose from x-rays of energy less than 10 KeV. The ISWE hardware was returned to Ukraine before the issue of adequate shielding for the astronauts was verified. Therefore, alternate experimental and analytical methods were developed to measure and predict the x-ray spectral and intensity distribution generated by electron impact with metal. These x-ray spectra were used to calculate the absorbed radiation dose to astronauts. These absorbed dose values were compared to TLD measurements obtained during actual operation of the in-vacuum electron beam welding tool. The calculated absorbed dose values were found to be in good agreement with the TLD values.

Edwards, David L.↗
NASA NTRS2001

Absorbed Dose Determination Using Experimental and Analytical Predictions of X-Ray Spectra

Electron beam welding in a vacuum is a technology that NASA is investigating as a joining technique for manufacture of space structures. This investigation characterizes the x-ray environment due to operation of an in-vacuum electron beam welding tool and provides recommendations for adequate shielding for astronauts performing the in-vacuum electron beam welding. NASA, in a joint venture with the Russian Space Agency, was scheduled to perform a series of welding in space experiments on board the U.S. Space Shuttle. This series of experiments was named the international space welding experiment (ISWE). The hardware associated with the ISWE was leased to NASA by the Paton Welding Institute (PWI) in Ukraine for ground-based welding experiments in preparation for flight. Two ground tests were scheduled, using the ISWE electron beam welding tool, to characterize the radiation exposure to an astronaut during the operation of the ISWE. These radiation exposure tests used thermoluminescence dosimeters (TLD's) shielded with material currently used by astronauts during extravehicular activities to measure the radiation dose. The TLD's were exposed to x-ray radiation generated by operation of the ISWE in-vacuum electron beam welding tool. This investigation was the first known application of TLD's to measure absorbed dose from x rays of energy less than 10 keV. The ISWE hardware was returned to Ukraine before the issue of adequate shielding for the astronauts was completely verified. Therefore, alternate experimental and analytical methods were developed to measure and predict the x-ray spectral and intensity distribution generated by ISWE electron beam impact with metal. These x-ray spectra were normalized to an equivalent ISWE exposure, then used to calculate the absorbed radiation dose to astronauts. These absorbed dose values were compared to TLD measurements obtained during actual operation of the ISWE in-vacuum electron beam welding tool. The calculated absorbed dose values were found to be in agreement with the measured TLD values.

Edwards, D. L.↗
NASA NTRS1982

Technique Lowers Weld Power Requirements

Three electron-beam welds and a spacer are used to replace a single deep electron-beam weld. Technique would reduce power required for welding making it possible to use low-power sources.

Pessin, R.↗
NASA NTRS1979

Checking weld penetration

Fused wire in weld root area verifies weld penetration in electron-beam-welded joints. Method could be used in automotive, aircraft, and machinery manufacturing when electron-beam-welds cannot be inspected ultrasonically.

Macfarlane, D. I.↗
NASA NTRSDate not supplied

Laser Beam Welding for in-Space Joining Demonstrated Under Vacuum on the Ground and By Parabolic Flight Experiments

High energy density electron beam welding enabled the first and, to date, only American weld performed in space during the M551 experiment on Skylab in 1973. Though welding is critical to 90% of durable goods manufacturing in America, there is not yet regular and reliable application of welding processes to the In-space Servicing, Assembly, and Manufacturing (ISAM) sector. Fundamental studies are needed to develop basic capabilities and to enhance fundamental process knowledge, which will support follow-on efforts to mature in-space welding for use in commercial, defense, and other aerospace applications. The current work seeks to build on past flights and improve understanding and quantification of materials joining in space conditions using laser beam welding (LBW). LBW offers several advantages over the electron beam welding of Skylab, amongst others: reduced electromagnetic interference, less exposure of operators to ionizing radiation, and flexible delivery through optical fibers supporting unique workpieces and joints. Since there is no orbital laboratory to mature laser beam welding for space, the current effort addresses maturation of laser beam welding through parabolic flights augmented with data collection to enable numerical modeling efforts that capture the physical effects of the space environment. This team has retrofitted an LBW experimental apparatus that can simulate the vacuum and, during a parabolic flight, the reduced gravity & microgravity conditions of in-space welding. A team of Capstone students modified the setup, originally developed by NASA Langley Research Center for electron beam free-form fabrication, to replace its electron gun with a 1 kW, 1070 nm Yb fiber laser. The apparatus was further instrumented with temperature sensing and high-speed welding cameras to monitor and record changes in the thermal state of the workpiece, the melt pool, the laser penetration level, and the development and orientation of spatter & plumes. The system will operate autonomously, demonstrating its utility to uncrewed missions. During upcoming parabolic flight campaigns expected summer 2024, this LBW equipment will weld common aerospace alloys of aluminum, stainless steel, and titanium under conditions representative of the space environment. This data will guide future computational modeling efforts of laser welding in space and help to qualify in-space welding as a viable ISAM technique.

laser beam welding↗
NASA NTRS1978

Fatigue behavior of two alloys for Space Shuttle applications

Two superalloys used extensively in the Space Shuttle main engine are Incoloy 903 and Inconel 718. The fatigue behavior of the two alloys under varying conditions is considered. Three heats of Incoloy 903 and two of Inconel 718 were used in the study. Material was tested in several conditions, including mill polish, longitudinal mill polish, transverse mill polish, chemically milled, chemically milled plus shotpeened on one side and on both sides, gas tungsten arc welded, and electron beam welded. Both round and flat tensile specimens were tested in universal test machines. It was found that surface condition influences test results. Transverse scratches resulting from polishing and rougher surfaces lower the stress at runout in relation to that obtained on longitudinally polished and/or smooth-surfaced specimens.

Adsit, N. R.↗
NASA NTRS1991

Effect of thermal exposure, forming, and welding on high-temperature, dispersion-strengthened aluminum alloy: Al-8Fe-1V-2Si

The feasibility of applying conventional hot forming and welding methods to high temperature aluminum alloy, Al-8Fe-1V-2Si (FVS812), for structural applications and the effect of thermal exposure on mechanical properties were determined. FVS812 (AA8009) sheet exhibited good hot forming and resistance welding characteristics. It was brake formed to 90 deg bends (0.5T bend radius) at temperatures greater than or equal to 390 C (730 F), indicating the feasibility of fabricating basic shapes, such as angles and zees. Hot forming of simple contoured-flanged parts was demonstrated. Resistance spot welds with good static and fatigue strength at room and elevated temperatures were readily produced. Extended vacuum degassing during billet fabrication reduced porosity in fusion and resistance welds. However, electron beam welding was not possible because of extreme degassing during welding, and gas-tungsten-arc welds were not acceptable because of severely degraded mechanical properties. The FVS812 alloy exhibited excellent high temperature strength stability after thermal exposures up to 315 C (600 F) for 1000 h. Extended billet degassing appeared to generally improve tensile ductility, fatigue strength, and notch toughness. But the effects of billet degassing and thermal exposure on properties need to be further clarified. The manufacture of zee-stiffened, riveted, and resistance-spot-welded compression panels was demonstrated.

Kennedy, J. R.↗