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Simple circuit modification makes pulse-arc starters more reliable at low currents. Once arc is started, it is maintained at lower voltage level that in previous arrangement due to sufficient concentration of metallic vapor between electrode and working surface as result of improved conduction.
The development of software for a Digital Equipment Corporation MINC-23 Laboratory Computer to provide functions of a workcell host computer for Space Shuttle Main Engine (SSME) robotic welding is documented. Routines were written to transfer robot programs between the MINC and an Advanced Robotic Cyro 750 welding robot. Other routines provide advanced program editing features while additional software allows communicatin with a remote computer aided design system. Access to special robot functions were provided to allow advanced control of weld seam tracking and process control for future development programs.
The fatigue crack growth rate of aluminum-lithium (Al-Li) alloy 2195 plate and weldments was determined at 200-F, ambient temperature and -320-F. The effects of stress ratio (R), welding process, orientation and thickness were studied. Results are compared with plate data from the Space Shuttle Super Lightweight Tank (SLWT) allowables program. Data from the current series of tests, both plate and weldment, falls within the range of data generated during the SLWT allowables program.
Stage 1 for the Carbon Nanotube Project has been completed. This videograph presents the proposal for Stage 2. The goals of this stage are to: (1) produce CNTs under different conditions such as cooling temperature, voltage, current, cathode and anode sizes; (2) use ferrocene to make longer CNTs; (3) characterize CNTs by spectroscopic methods; (4) develop applications of CNTs, i.e., batteries, composites, wires, etc.; and (5) complete the patent application.
Abstract not provided.
Abstract not provided.
Wire arc additive manufacturing (WAAM) via metal inert gas (MIG)/gas metal arc welding (GMAW) is a viable option for fabrication of large-scale titanium parts; however, it introduces new safety hazards associated with both the material and the additional system hardware required for the process. Localized gas shielding of the weld arc via standard GMAW torch is inadequate for titanium due to its affinity for oxygen; thereby requiring the use of an inert enclosure to protect the weld from entraining oxygen. The use of the inert enclosure presents potential safety hazards such as operator asphyxiation and brings up discussion of confined space considerations. In addition, the titanium welding process creates pyrophoric titanium soot residue around the deposit, which can undergo deflagration during part cleaning and part removal. This paper provides an overview of the titanium WAAM process along with safety considerations for the design and operation of the inert enclosure as well as functional solutions for the safe handling of the titanium soot by-product.
A comprehensive evaluation is conducted of candidate processes for metalworking in orbital (vacuum-microgravity) conditions. Attention is given to electron-beam welding, brazing, gas-tungsten arc welding, laser welding, plasma arc welding, and gas-metal arc welding. It is established that several of these processes will be required to cover all foreseeable requirements. Microgravity effects are considered minor, and efforts are being concentrated on problems associated with vacuum conditions and with process-operator safety.
A plasma arc welding torch is discussed. A first plasma gas is directed through the body of the welding torch and out of the body across the tip of a welding electrode disposed at the forward end of the body. A second plasma gas is disposed for flow through a longitudinal bore in the electrode. The second plasma gas enters one end of the electrode and exits the electrode at the tip thereof for co-acting with the electric welding arc to produce the desired weld. A shield gas is directed through the torch body and circulates around the head of the torch adjacent to the electrode tip.
Low-temperature phase transformation (LTPT) welding consumables are a new class of welding wires developed to mitigate hydrogen-induced cracking in the welding of high-strength steels without preheating or postweld heat treatment. LTPT weld metals have a high strength, but their toughness needs further investigation. LTPT weld metals predominately contain a martensite microstructure, which is necessary to achieve high strength; however, martensitic weld metals containing oxide inclusions have relatively poor toughness. For this study, three welding processes — gas metal arc welding (GMAW), gas tungsten arc welding (GTAW), and hot wire GTAW — were investigated. Optical microscopy, scanning electron microscopes, and transmission electron microscopes were employed for characterization. The role of the shielding gas in the formation of oxide inclusions in LTPT weld metals was investigated. The formation of oxide inclusions in the weld metals was related to the CO 2 in the shielding gas. When 100% Ar or a pure inert shielding gas mixture was used for all three welding processes, oxide inclusions were greatly reduced, and the weld metal toughness improved considerably, matching the base metal toughness. The mechanism by which inclusions promote fracture propagation in the weld metal was proposed.
123 Certification Inc., a Montreal based company, has developed an innovative hands-on welding simulator solution to help build the welding workforce in the most simple way. The solution lies in virtual reality technology, which has been fully tested since the early 90's. President and founder of 123 Certification Inc., Mr. Claude Choquet Ing. Msc. IWE. acts as a bridge between the welding and the programming world. Working in these fields for more than 20 years. he has filed 12 patents world-wide for a gesture control platform with leading edge hardware related to simulation. In the summer of 2006. Mr Choquet was proud to be invited to the annual IIW International Weld ing Congress in Quebec City to launch the ARC+ welding simulator. A 100% virtual reality system and web based training center was developed to simulate multi process. multi-materiaL multi-position and multi pass welding. The simulator is intended to train welding students and apprentices in schools or industries. The welding simulator is composed of a real welding e[eetrode holder (SMAW-GTAW) and gun (GMAW-FCAW). a head mounted display (HMD), a 6 degrees of freedom tracking system for interaction between the user's hands and head. as well as external audio speakers. Both guns and HMD are interacting online and simultaneously. The welding simulation is based on the law of physics and empirical results from detailed analysis of a series of welding tests based on industrial applications tested over the last 20 years. The simulation runs in real-time, using a local logic network to determine the quality and shape of the created weld. These results are based on the orientation distance. and speed of the welding torch and depth of penetration. The welding process and resulting weld bc.1d are displayed in a virtual environment with screenplay interactive training modules. For review. weld quality and recorded process values can be displayed and diagnosed after welding. To help in the le.tming process, a learning curve for each student and each Virtual Welding Class'" can be plotted, for an instructor's review or a required third party evaluation.
The mechanical behavior of a cast form of an advanced austenitic stainless steel, CF8C-Plus, is compared with that of its wrought equivalent in terms of both tensile and creep-rupture properties and estimated allowable stress values for pressurized service at temperatures up to about 850°C. A traditional Larson-Miller parametric model is used to analyze the creep-rupture data and to predict long-term lifetimes for comparison of the two alloy types. The cast CF8C-Plus exhibited lower yield and tensile strengths, but higher creep strength compared to its wrought counterpart. Two welding methods, shielded-metal-arc welding (SMAW) and gas-metal-arc welding, met the weld qualification acceptance criteria in ASME BPVC Section IX for the cast CF8C-Plus. However, for the wrought CF8C-Plus, while SMAW and gas-tungsten-arc welding passed the tensile acceptance criteria, they failed the side bend tests due to lack of fusion or weld metal discontinuities.
Arc-light reflector for through-the-torch welding vision system designed expressly for use in welding ducts of small diameter. Cylindrical reflector positioned to reflect light diffusely from welding arc onto nearby surface of workpiece for most advantageous viewing along axis of welding torch.
Proposed welding technique combines best features of metal (other than tungsten)/inert-gas welding, plasma arc welding, and tungsten/inert-gas welding. Advantages include: wire fed to weld joint preheated, therefore fed at high speed without spattering; high-frequency energy does not have to be supplied to workpiece to initiate welding; size of arc gap not critical, power-supply control circuit adjusts voltage across gap to compensate for changes; only low gas-flow rate needed; welding electrode replaced easily as prefabricated assembly; external wire-feeding manipulator not needed; and welding process relatively forgiving of operator error.
The need for automated plasma welding was identified in the early stages of the Space Station Freedom Program (SSFP) because it requires approximately 1.3 miles of welding for assembly. As a result of the Variable Polarity Plasma Arc Welding (VPPAW) process's ability to make virtually defect-free welds in aluminum, it was chosen to fulfill the welding needs. Space Station Freedom will be constructed of 2219 aluminum utilizing the computer controlled VPPAW process. The 'Node Radial Docking Port', with it's saddle shaped weld path, has a constantly changing surface angle over 360 deg of the 282 inch weld. The automated robotic VPPAW process requires eight-axes of motion (six-axes of robot and two-axes of positioner movement). The robot control system is programmed to maintain Torch Center Point (TCP) orientation perpendicular to the part while the part positioner is tilted and rotated to maintain the vertical up orientation as required by the VPPAW process. The combined speed of the robot and the positioner are integrated to maintain a constant speed between the part and the torch. A laser-based vision sensor system has also been integrated to track the seam and map the surface of the profile during welding.
New sensors for both arc welding and resistance spot welding processes were studied. For arc welding, the arc itself is used as the sensor. Minor changes in both composition and geometry of the plasma result in fluctuations in the arc voltage. While the process as currently employed is an off-line system, development of an on-line process controller would be possible once the optimum analysis technique is developed. It has been shown that for resistance spot welding, the dynamic resistance of the weld joint can be correlated to growth of the fusion zone. It is indicated that this technique is not as useful for projection welds as for spot welds.
Proposed optical system integrated into plasma arc welding torch provides image of leading edge of weld pool and welding-arc-initiation point. Welding torch aligned better with joint. System includes coherent bundle of optical fibers and transparent cup.
Joining processes for aerospace systems combine fusion welding and solid state joining during production of metal structures. Detailed characteristics of electron beam welding, plasma arc welding, diffusion welding, inertia welding and weldbond processes are discussed.