Electric welding torch Patent
Development of electric weeding torch with casing on one end to form inert gas shield
Allen, G. V.↗
SEARCH · Engineering Papers
Results for “WELDING, GAS”
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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Results of Uranium Dioxide-Tungsten Irradiation Test and Post-Test Examination
A uranium dioxide (UO2) fueled capsule was fabricated and irradiated in the NASA Plum Brook Reactor Facility. The capsule consisted of two bulk UO2 specimens clad with chemically vapor deposited tungsten (CVD W) 0.762 and 0.1016 cm (0.030-and 0.040-in.) thick, respectively. The second specimen with 0.1016-cm (0.040-in.) thick cladding was irradiated at temperature for 2607 hours, corresponding to an average burnup of 1.516 x 10 to the 20th power fissions/cu cm. Postirradiation examination showed distortion in the bottom end cap, failure of the weld joint, and fracture of the central vent tube. Diametral growth was 1.3 percent. No evidence of gross interaction between CVD tungsten or arc-cast tungsten cladding and the UO2 fuel was observed. Some of the fission gases passed from the fuel cavity to the gas surrounding the fuel specimen via the vent tube and possibly the end-cap weld failure. Whether the UO2 loss rates through the vent tube were within acceptable limits could not be determined in view of the end-cap weld failure.
Collins, J. F.↗
Self-welding of Inconel 617 under high-pressure-high-temperature conditions for nuclear reactors
In response to continuously declining availability of fossil fuels, nuclear power has become an important alternative source of power generation. Growing application of nuclear power has relieved the shortage of electricity. However, it is also accompanied with new drawbacks, such as radioactive waste, and potential catastrophic consequences in case of major accidents. For nuclear power plants, severe accidents mostly originate from the reactor, making the reliability of the reactor of paramount importance to the overall safety of a nuclear power plant. Massive heat generation through nuclear fission/fusion and heat exchange render the whole reactor operating at extremely high temperatures (i.e., 900–1000 °C), which, in conjunction with large load from subsystems/ components made of special heavy alloys, renders the reactor under the risk of self-welding, a phenomenon that could lead to strong bonding between components and paralyze the operability of the nuclear reactor. This paper investigates the self-welding behavior of Inconel 617, a primary candidate nickel alloy for key components of the next generation gas cooled nuclear plant, inside a controlled atmospheric furnace with preset static load, simulating the high-pressure high-temperature conditions inside nuclear reactors. Therefore, test results show that Inconel 617 experiences self-welding through common oxide zone at the interface, and it has remarkable bonding strength, requiring 4114 N (57.15 MPa) and 4338 N (60.25 MPa) to break apart a mated sample pair, under an apparent contact pressure of 0.341 MPa after 50-h aging, in helium and air atmospheres, respectively. The higher oxygen presence in air results in slightly stronger oxide bond at the interface, compared to helium, and the bond strength increases with dwell time.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Altering the Supply of Shielding Gases to Fabricate Distinct Geometry in GMA Additive Manufacturing
Wire arc additive manufacturing (WAAM) is the process by which large, metallic structures are built, layer-by-layer, using a welding arc to melt wire feedstock. In this process, the proper selection of the shielding gas plays a vital role in the achievement of structurally acceptable part geometries and quality surface finishes. In this study, the authors used either a ternary mix (He, Ar and CO 2 ) or a binary mix (Ar and CO 2 ) of shielding gases to deposit wall geometries using an open loop-controlled WAAM system developed at Oak Ridge National Laboratory’s Manufacturing Demonstration Facility. The binary blend produced a wider and shorter geometry, while the ternary blend resulted in a narrower build that was more equivalent to the CAD geometry. The data indicated that the binary blend provided a higher oxygen concentration in the weld as compared to that of the ternary blend. The results imply that the arc characteristics and heat input had a significantly higher impact on the weld penetration than the surface tension effect of surface active elements. This was further verified by developing and applying a high-fidelity computational fluid dynamics (CFD) model of the thermophysical properties of gas mixtures. The results from the model showed that, while the influence of increased oxygen concentration on the surface tension for the binary blend led to a deeper penetration, the ternary blend gave rise to heat flux to the workpiece.
36 MATERIALS SCIENCE↗
Initial Testing of an In Situ Load Retention Aging Vessel
A thermal aging vessel instrumented with load cells was fabricated. The primary function of the vessel is to continuously monitor the in situ load retention of up to three compressed polymer coupons undergoing thermally accelerated aging under nitrogen. A secondary function is to enable gas sampling of the vessel headspace during thermal aging. Heating of the vessel is achieved using a custom heater jacket. To improve upon our conventional aging study methods which require periodic interruption of aging to perform load testing in an Instron machine at room temperature, this technology aims to automate/facilitate data acquisition/analysis, improve data quality, and enable uninterrupted compression of the polymer which represents the service condition. As an example case to assess functionality of the in situ vessel, the load retention of a siloxane elastomer material additively manufactured by direct-ink-writing (DIW) was measured at three different isothermal aging temperatures for ~1 month. Initial compression of the coupons while near the aging temperature was achieved by temporarily opening the heated vessel to access the interior chamber and manually tightening four nuts to drive the heated compression plate down onto the heated coupons. Initial testing demonstrated achievement of the primary load retention monitoring function. Unfortunately, the vessel leaked which prevented gas sampling; an active purge was used to maintain a nitrogen atmosphere. Welded or otherwise sealed joints, which could be implemented in a future design, would likely eliminate leak paths. To apply time-temperature superposition (TTS), a technique used to provide long-term prediction of the load retention from short-term isothermal data, the load retention needed to be calculated relative to the load at an estimated “equilibrium” time, after most of the transient viscoelastic physical relaxation occurred. The peak load immediately after compression could not be used as the load retention basis for two reasons: (1) age-related changes must be isolated from non-age-related physical relaxation before applying TTS and (2) the manual mechanism used to compress the specimens at the aging temperature was neither smooth nor repeatable which affected the peak load value. To better understand the effect of the mode of initial compression on the measured load, and possibly better estimate “equilibrium” physical relaxation times, systematic stress relaxation experiments were performed using an Instron machine with a thermal chamber. At a given temperature, the DIW polymer was compressed to a fixed strain in either a stepped or continuous manner at two different rates, then held at that strain for 24 hrs. The results indicated that, at a given temperature, the different stress relaxation curves appeared to converge to the same curve at some “equilibrium” time when the non-age-related physical relaxation was mostly complete. Though this observation suggests that the discontinuous manual compression employed by the vessel is feasible, a compression mechanism that is rapid, smooth, and repeatable would enhance its use.
36 MATERIALS SCIENCE↗
Investigation of the vapour-plasma plume in the welding of titanium by high-power ytterbium fibre laser radiation
The vapour-plasma plume produced in the welding of 6-mm thick VT-23 titanium alloy plates by ytterbium fibre laser radiation of up to 10 kW power is studied in the protective Ar gas medium. High-speed video filming of the vapour-plasma plume is used to visualise the processes occurring during laser welding. The coefficient of inverse bremsstrahlung by the welding plasma plume is calculated from the data of the spectrometric study. (interaction of laser radiation with matter)
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Method of cold welding using ion beam technology
A method for cold welding metal joints is described. In order to remove the contamination layer on the surface of the metal, an ion beam generator is used in a vacuum environment. A gas, such as xenon or argon, is ionized and accelerated toward the metal surface. The beam of gas effectively sputters away the surface oxides and contamination layer so that clean underlying metal is exposed in the area to be welded. The use of this method allows cold welding with minimal deformation. Both similar and dissimilar metals can be cold welded with this method.
Sater, B. L.↗
Better welds for launch vehicles
The use and benefits of automated variable polarity plasma arc (VPPA) welding of Al joints are described. The entire welding system, including welding head manipulator, weld-wire feed, torch, and power supply are computer controlled. The importance of proper torch dynamics and the control of argon gas flow through the plasma orifice are discussed. The use of arc-voltage control, the improvements in system monitoring, and the reduction or elimination of electromagnetic interferences are examined. VPPA welding is applicable to joining Space Shuttle components, and an example of its use on an External Tank of the Shuttle is presented.
Schwinghamer, Robert J.↗
Experimental performance of an internal resistance heater for Langley 6-inch expansion tube driver
An experimental investigation of the heating characteristics of an internal resistance heating element was conducted in the driver of the Langley 6-inch expansion tube to obtain actual operating conditions, to compare these results to theory, and to determine whether any modification need be made to the heater element. The heater was operated in pressurized helium from 138. MN/sq m to 62.1 MN/sq m. This investigation revealed large temperature variations within the heater element caused primarily by area reductions at insulator locations. These large temperature variations were reduced by welding small tabs over all grooves. Previous predictions of heater element and driver gas temperature were unacceptable so new equations were derived. These equations predict element and gas temperature within 10 percent of the test data when either the constant power cycle or the interrupted power cycle is used. Visual observation of the heater element, when exposed to the atmosphere with power on, resulted in a decision to limit the heater element to 815 K. Experimental shock Mach numbers are in good agreement with theory.
Creel, T. R., Jr.↗
The effect of impurity gasses on variable polarity plasma arc welded 2219 aluminum
Variable polarity plasma arc (VPPA) welding has been used with considerable success by NASA for the welds on the Space Shuttle External Tank as well as by others concerned with high quality welded structures. The effects of gaseous contaminants on the appearance of VPPA welds on 2219 aluminum are examined so that a welder can recognize that such contamination is present and take corrective measures. There are many possible sources of such contamination including, contaminated gas bottles, leaks in the gas plumbing, inadequate shield gas flow, condensed moisture in the gas lines or torch body, or excessive contaminants on the workpiece. The gasses chosen for study in the program were nitrogen, oxygen, methane, and hydrogen. Welds were made in a carefully controlled environment and comparisons were made between welds with various levels of these contaminants and welds made with research purity (99.9999 percent) gasses. Photographs of the weld front and backside as well as polished and etched cross sections are presented.
Mcclure, John C.↗
Switchbox for welding torches
Switchbox can be used to change from one welding torch setup to another without stopping production line. Simple flip of switch connects gas, water, and power to selected torch. In conventional systems, production must be stopped so that maintenance people can disconnect and reconnect another torch.
Burley, R. K.↗
Carbon molecular sieve membranes on porous composite tubular supports for high performance gas separations
Thin carbon molecular sieve membranes (<500 nm) were fabricated inside of long geometry (9 inch) of stainless steel tubes with all welded construction. Alumina intermediate layer on porous stainless steel tube support was used to reduce effective support pore size and to provide a more uniform surface roughness. Novolac phenolic resin solution was then coated on the inside of porous stainless steel tube by slip casting while their viscosities were controlled from 5 centipoises to 30 centipoises. Carbonization was carried out at 700 °C in which thermal stress was minimized and high quality carbon films were prepared. The highest separation performance characteristics were obtained using 20 cP phenolic resin solutions. The fabricated CMSM showed good separation factor for He/N 2 462, CO 2 /N 2 97, and O 2 /N 2 15.4. As the viscosity of polymer precursor solution was reduced from 20 cP to 15 cP, gas permeance values almost doubled with somewhat lower separation factor He/N 2 156, CO 2 /N 2 88, and O 2 /N 2 7.7.
36 MATERIALS SCIENCE↗
Mount assembly for porous transition panel at annular combustor outlet
A gas turbine engine combustor assembly of annular configuration has outer and inner walls made up of a plurality of axially extending multi-layered porous metal panels joined together at butt joints therebetween and each outer and inner wall including a transition panel of porous metal defining a combustor assembly outlet supported by a combustor mount assembly including a stiffener ring having a side undercut thereon fit over a transition panel end face; and wherein an annular weld joins the ring to the end face to transmit exhaust heat from the end face to the stiffener ring for dissipation from the combustor; a combustor pilot member is located in axially spaced, surrounding relationship to the end face and connector means support the stiffener ring in free floating relationship with the pilot member to compensate for both radial and axial thermal expansion of the transition panel; and said connector means includes a radial gap for maintaining a controlled flow of coolant from outside of the transition panel into cooling relationship with the stiffener ring and said weld to further cool the end face against excessive heat build-up therein during flow of hot gas exhaust through said outlet.
Sweeney, Ralph B.↗
Analysis of Arc Welding Process in Space
This work is motivated by NASA plans to conduct welding experiments on the ISS. It is expected that deployment of welding and additive manufacturing technologies in the space environment has the potential to revolutionise how orbiting platforms are designed, manufactured, and assembled. However, the structure, composition and quality of a weld is extremely dependent on the environment and can be difficult to control in space. Shielding gases would also be tough to manage as gases behave differently in zero gravity and airless environments. Additional points of concern are related to the spatter and sparks dynamics in space. Therefore, there is a need for a more basic understanding of welding processes by computational modelling. To provide such an insight we developed state of art models of the ARC torch, droplet detachment and transfer, and the melt pool build up using magnetohydrodynamics approximation and level set method for two-phase liquid metal/-gas flow modelling. Two finite element models were built using 2D axisymmetric geometry in COMSOL Multiphysics®: (i) stationary model of the ARC torch and (ii) dynamical model of droplet detachment and transfer. Both models demonstrate reasonable agreement with earlier experimental observations and high sensitivity to the temperature dependence of the thermophysical parameters on the system materials. The models were used to provide physical insight into ARC welding in various environments and geometries. It was shown, in particular, that there is a significant probability of gas bubbles trapping in the meltpool and a possibility of unbounded wondering of sparks in the welding chamber in zero gravity. In addition, we estimated metal evaporation rate that may be hazardous in the confined environment of the ISS. These issues raise concern of quality of the weld and safety for ISS applications.
ARC welding↗
Metal vapor micro-jet controls material redistribution in laser powder bed fusion additive manufacturing
Abstract not provided
36 MATERIALS SCIENCE↗
Polymeric Bladder for Storing Liquid Oxygen
A proposed system for storing oxygen in liquid form and dispensing it in gaseous form is based on (1) initial subcooling of the liquid oxygen; (2) containing the liquid oxygen in a flexible vessel; (3) applying a gas spring to the flexible vessel to keep the oxygen compressed above the saturation pressure and, thus, in the liquid state; and (4) using heat leakage into the system for vaporizing the oxygen to be dispensed. In a typical prior system based on these principles, the flexible vessel is a metal bellows housed in a rigid tank, and the gas spring consists of pressurized helium in the tank volume surrounding the bellows. Unfortunately, the welds in the bellows corrugations are subject to fatigue, and, because bellows have large ullage, a correspondingly large fraction of the oxygen content cannot be expelled. In the proposed system, the flexible vessel would be a bladder made of a liquid- crystal polymer (LCP). (LCPs are strong and compatible with liquid oxygen.) In comparison with a metal bellows, a polymeric bladder would have less ullage and would weigh less. In experiments involving fatigue cycling at liquid-nitrogen temperatures, two LCPs were found to be suitable for this application.
Walker, David H.↗
NASA Tech Briefs, March 2006
Topics covered include: Medical Signal-Conditioning and Data-Interface System; Instruments for Reading Direct-Marked Data-Matrix Symbols; Processing EOS MLS Level-2 Data; Ground Processing of Data From the Mars Exploration Rovers; Estimating Total Electron Content Using 1,000+ GPS Receivers; NASA Solar Array Demonstrates Commercial Potential; Improved Control of Charging Voltage for Li-Ion Battery; Programmable Pulse-Position-Modulation Encoder; Wavelength-Agile External-Cavity Diode Laser for DWDM; Pattern-Recognition Processor Using Holographic Photopolymer; Submicrosecond Power-Switching Test Circuit; Three-Function Logic Gate Controlled by Analog Voltage; Integrated System for Autonomous Science; Montage Version 3.0; Utilizing AI in Temporal, Spatial, and Resource Scheduling; Satellite Image Mosaic Engine; Architecture for Control of the K9 Rover; HFGMC Enhancement of MAC/GMC; Automated Activation and Deactivation of a System Under Test; Cleaning Carbon Nanotubes by Use of Mild Oxygen Plasmas; Generating Aromatics From CO2 on Mars or Natural Gas on Earth; Attaching Thermocouples by Peening or Crimping; Heat Treatment of Friction-Stir-Welded 7050 Aluminum Plates; Generating Breathable Air Through Dissociation of N2O; High-Performance Scanning Acousto-Ultrasonic System; Correction for Thermal EMFs in Thermocouple Feedthroughs; Using Quasiparticle Poisoning To Detect Photons; Estimating Resolution Lengths of Hybrid Turbulence Models; Education and Training Module in Alertness Management; Cargo-Positioning System for Next-Generation Spacecraft; Micro-Imagers for Spaceborne Cell-Growth Experiments; Holographic Solar Photon Thrusters; Plasma-Based Detector of Outer-Space Dust Particles; and Generation of Data-Rate Profiles of Ka-Band Deep-Space Links.
Source record↗
Fluid modeling of low-temperature plasmas
Fluid models are essential for understanding and predicting low-temperature plasma (LTP) behavior in various scientific and industrial settings. This paper provides an introductory tutorial on fluid modeling of LTPs, covering model formulation, implementation, and computational simulations. The tutorial focuses on five main components of the formulation of LTP fluid models: fluid flow, energy, chemistry, electromagnetism, and material properties, as well as in essential aspects of model implementations, including multiscale phenomena, multiphysics coupling, and numerical convergence. Designed for students and early-career researchers, this work offers a practical foundation for developing and using fluid models, from in-house computational codes to commercial software, bridging fundamental theory with real-world applications.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗