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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 955 records · Page 53
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Weld Repair of Thin Aluminum Sheet

Weld repairing of thin aluminum sheets now possible, using niobium shield and copper heat sinks. Refractory niobium shield protects aluminum adjacent to hole, while copper heat sinks help conduct heat away from repair site. Technique limits tungsten/inert-gas (TIG) welding bombardment zone to melt area, leaving surrounding areas around weld unaffected. Used successfully to repair aluminum cold plates on Space Shuttle, Commercial applications, especially in sealing fractures, dents, and holes in thin aluminum face sheets or clad brazing sheet in cold plates, heat exchangers, coolers, and Solar panels. While particularly suited to thin aluminum sheet, this process also used in thicker aluminum material to prevent surface damage near weld area.

Beuyukian, C. S.↗
NASA NTRS1986

Theoretical Foundation for Weld Modeling

Differential equations describe physics of tungsten/inert-gas and plasma-arc welding in aluminum. Report collects and describes necessary theoretical foundation upon which numerical welding model is constructed for tungsten/inert gas or plasma-arc welding in aluminum without keyhole. Governing partial differential equations for flow of heat, metal, and current given, together with boundary conditions relevant to welding process. Numerical estimates for relative importance of various phenomena and required properties of 2219 aluminum included

Traugott, S.↗
NASA NTRS1986

Welding and Brazing Silicon Carbide

Hot isostatic pressing and conventional furnace brazing effective under right conditions. Study performed showed feasibility of welding SiC using several welding and brazing techniques. Use of SiC improves engine efficiency by allowing increase in operating temperature. SiC successfully hot-pressure-welded at 3,550 degrees F (1,950 degrees C) in argon. Refinements of solid-state welding and brazing procedures used sufficient for some specific industrial applications.

Moore, T. J.↗
NASA NTRS1986

Physics of Fusion Welding

Applicabilities and limitations of three techniques analyzed. NASA technical memorandum discusses physics of electron-beam, gas/ tungsten-arc, and laser-beam welding. From comparison of capabilities and limitations of each technique with regard to various welding conditions and materials, possible to develop criteria for selecting best welding technique in specific application. All three techniques classified as fusion welding; small volume of workpiece melted by intense heat source. Heat source moved along seam, leaving in wake solid metal that joins seam edges together.

Nunes, A. C., Jr.↗
NASA NTRS1986

Properties of VPPA-Welded 2219-T87 Aluminum

Metallurgical properties and effects of welding described. Report describes investigation of welding of 2219-T87 aluminum alloy by variable-polarity plasma-arc (VPPA) process. Research was to determine highest strength attainable with this alloy and process and to estimate changes in weld properties caused by variations of process controls. Alloy 2219 strong and heat treatable and retains structural integrity up to 600 degrees F (316 degress C). Is principal structural alloy of Space Shuttle external tank. VPPA process offers many advantages and replaces tungsten/inert-gas process used. In over 24,000 in. (610 m) of welds on tank, there has been no internal defect requiring manual repair.

Wilson, W.↗
NASA NTRS1985

Feasibility of remotely manipulated welding in space: A step in the development of novel joining technologies

A six month research program entitled Feasibility of Remotely Manipulated Welding in Space - A Step in the Development of Novel Joining Technologies is performed at the Massachusetts Institute of Technology for the Office of Space Science and Applications, NASA, under Contract No. NASW-3740. The work is performed as a part of the Innovative Utilization of the Space Station Program. The final report from M.I.T. was issued in September 1983. This paper presents a summary of the work performed under this contract. The objective of this research program is to initiate research for the development of packaged, remotely controlled welding systems for space construction and repair. The research effort includes the following tasks: (1) identification of probable joining tasks in space; (2) identification of required levels of automation in space welding tasks; (3) development of novel space welding concepts; (4) development of recommended future studies; and (5) preparation of the final report.

Masubuchi, K.↗
NASA NTRS1985

Influence of control parameters on the joint tracking performance of a coaxial weld vision system

The first phase of a series of evaluations of a vision-based welding control sensor for the Space Shuttle Main Engine Robotic Welding System is described. The robotic welding system is presently under development at the Marshall Space Flight Center. This evaluation determines the standard control response parameters necessary for proper trajectory of the welding torch along the joint.

Gangl, K. J.↗
NASA NTRS1987

Alternating-Polarity Arc Welding

Brief reversing polarity of welding current greatly improves quality of welds. NASA technical memorandum recounts progress in art of variable-polarity plasma-arc (VPPA) welding, with emphasis on welding of aluminum-alloy tanks. VPPA welders offer important advantages over conventional single-polarity gas/tungsten arc welders.

Schwinghamer, R. J.↗
NASA NTRS1986

The effect of electron beam welding on the creep rupture properties of a Nb-Zr-C alloy

Creep rupture tests of electron beam welded PWC-11 sheet were conducted at 1350 K. Full penetration, single pass welds were oriented transverse to the testing direction in 1 mm thick sheet. With this orientation, stress was imposed equally on the base metal, weld metal, and heat-affected zone. Tests were conducted in both the postweld annealed and aged conditions. Unwelded specimens with similar heat treatments were tested for comparative purposes. It was found that the weld region is stronger than the base metal for both the annealed and aged conditions and that the PWC-11 material is stronger in the annealed condition than in the aged condition.

Moore, T. J.↗
NASA NTRS1987

Off-line programming motion and process commands for robotic welding of Space Shuttle main engines

The off-line-programming software and hardware being developed for robotic welding of the Space Shuttle main engine are described and illustrated with diagrams, drawings, graphs, and photographs. The menu-driven workstation-based interactive programming system is designed to permit generation of both motion and process commands for the robotic workcell by weld engineers (with only limited knowledge of programming or CAD systems) on the production floor. Consideration is given to the user interface, geometric-sources interfaces, overall menu structure, weld-parameter data base, and displays of run time and archived data. Ongoing efforts to address limitations related to automatic-downhand-configuration coordinated motion, a lack of source codes for the motion-control software, CAD data incompatibility, interfacing with the robotic workcell, and definition of the welding data base are discussed.

Ruokangas, C. C.↗
NASA NTRS1988

Image Control In Automatic Welding Vision System

Orientation and brightness varied to suit welding conditions. Commands from vision-system computer drive servomotors on iris and Dove prism, providing proper light level and image orientation. Optical-fiber bundle carries view of weld area as viewed along axis of welding electrode. Image processing described in companion article, "Processing Welding Images for Robot Control" (MFS-26036).

Richardson, Richard W.↗
NASA NTRS1988

Processing Welding Images For Robot Control

Image data from two distinct windows used to locate weld features. Analyzer part of vision system described in companion article, "Image Control in Automatic Welding Vision System" (MFS-26035). Horizontal video lines define windows for viewing unwelded joint and weld pool. Data from picture elements outside windows not processed. Widely-separated local features carry no significance, but closely spaced features indicate welding feature. Image processor assigns confidence level to group of local features according to spacing and pattern.

Richardson, Richard W.↗
NASA NTRS1988

Argon Welding Inside A Workpiece

Canopies convert large hollow workpiece into inert-gas welding chamber. Large manifold serves welding chamber for attachment of liner parts in argon atmosphere. Every crevice, opening and passageway provided with argon-rich environment. Weld defects and oxidation dramatically reduced; also welding time reduced.

Morgan, Gene E.↗
NASA NTRS1988

Redundant Grounding Circuit For Arc Welding

Arc burns at loose ground connections prevented. Protective grounding scheme for arc-welding power supply includes four ground leads to workpiece and circuit that automatically turns off welding current if one or two ground leads becomes disconnected. Prevents burns and inadvertent welding occuring where full welding current passes through single loose ground contact.

Burley, Richard K.↗
NASA NTRS1988

A Generalized Method for Automatic Downhand and Wirefeed Control of a Welding Robot and Positioner

A generalized method for controlling a six degree-of-freedom (DOF) robot and a two DOF positioner used for arc welding operations is described. The welding path is defined in the part reference frame, and robot/positioner joint angles of the equivalent eight DOF serial linkage are determined via an iterative solution. Three algorithms are presented: the first solution controls motion of the eight DOF mechanism such that proper torch motion is achieved while minimizing the sum-of-squares of joint displacements; the second algorithm adds two constraint equations to achieve torch control while maintaining part orientation so that welding occurs in the downhand position; and the third algorithm adds the ability to control the proper orientation of a wire feed mechanism used in gas tungsten arc (GTA) welding operations. A verification of these algorithms is given using ROBOSIM, a NASA developed computer graphic simulation software package design for robot systems development.

Fernandez, Ken↗
NASA NTRS1988

Welding torch gas cup extension

The invention relates to a gas shielded electric arc welding torch having a detachable gas cup extension which may be of any desired configuration or length. The gas cup extension assembly is mounted on a standard electric welding torch gas cup to enable welding in areas with limited access. The gas cup assembly has an upper tubular insert that fits within the gas cup such that its lower portion protrudes thereform and has a lower tubular extension that is screwed into the lower portion. The extension has a rim to define the outer perimeter of the seat edge about its entrance opening so a gasket may be placed to effect an airtight seal between the gas cup and extension. The tubular extension may be made of metal or cermaic material that can be machined. The novelty lies in the use of an extension assembly for a standard gas cup of an electric arc welding torch which extension assembly is detachable permitting the use of a number of extensions which may be of different configurations and materials and yet fit the standard gas cup.

Gordon, Stephen S.↗
NASA NTRS1989

Gray-Scale Processing For Tracking Of Welds

Digital analysis of video-image-processing system contributes to automation of weld-seam tracking. Makes no contact with seam. Small television camera views seam just ahead of point currently being welded. Arc provides illumination. Periodically frame grabber digitizes video image and stores in computer memory as gray-scale values. Seam located by analyzing Hough-transform arrays of derivatives of digitally-filtered image data. Information on location and orientation of seam used as feedback by welding robot to correct deviations of electrode from seam as welding continues.

Gutow, David A.↗
NASA NTRS1989

Identification Of Anomalies In Welds

Advanced techniques combined with conventional analytical methods. Combination of real-time radiography, scanning electron microscopy, and energy-dispersive spectrometry identify enigmatic features in radiographs of welds where standard tensile, hardness, and electrical-conductivity tests and visible-light microscopic and macroscopic examinations insufficient. New combination of techniques applied successfully to variable-polarity-plasma-arc welds of 2219 aluminum alloy. Joints subjected to penetration, fill, and weld-repair passes with 2319 aluminum weld wire.

Knichen, David G.↗