Arc stability and melting characteristics of welding wire for use with 2219 aluminum alloy plate
Arc stability and melting characteristics of welding wire for arc welding of 2219 aluminum alloy plate
ALUMINUM ALLOY↗
SEARCH · Search NASA
Results for “WELDING”
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
A study of inert-gas welding process transferability of set-up parameters
Feasibility of transferring TIG weld settings and obtaining similar weld characteristics
TUNGSTEN INERT GAS /TIG/ WELDING↗
Weld-alloy
Weld-alloy technique for overlaid weld of specific metal to produce predictable alloy with predictable mechanical properties
MECHANICAL PROPERTY↗
Welding in airplane construction
The present article attempts to explain the principles for the production of a perfect weld and to throw light on the unexplained problems. Moreover, it is intended to elucidate the possibilities of testing the strength and reliability of welded parts.
WELDING↗
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↗
90/95 POD Radiography Concern for COPVs and Metal Tank Welds
Radiographic inspections of welds in all-metal tanks and composite overwrapped pressure vessel (COPV) liners that are used to establish initial crack size in damage tolerance assessments are not as rigorous as previously understood. As a result, the 90/95 percent probability of detection (POD) requirements in S-080 1 and S-081 2 are not met when this inspection method is used. Development of new inspection methods will require about three years. During that time, additional review and assessment of the fracture margin may be needed to support waivers and provide a better understanding of weld cracking risk associated with an individual tank design.
90/95 POD Radiography Concern↗
Physics-Based Modeling and Simulation of Self-Reacting Friction Stir Welding Using Computational Fluid Dynamics
A physics-based model was developed to simulate the behavior of material in a self-reacting friction stir welding (SR-FSW) process for the joining of metals. This steady-state model builds upon fundamental computational fluid dynamic (CFD) principles within Ansys Fluent to solve the discretized equations. The effective viscosity is calculated using a viscoplastic model using a Sheppard-Wright formulation of flow stress. Numerous advancements have been made in the incorporated physics including (1) temperature-dependent material properties; (2) locally adaptable flow and thermal boundary conditions; and (3) adapting material properties in nugget in response to microstructural changes. Simulation strategies to accelerate computation and improve numerical stability include adapting the mesh refinement and solver relaxation factors during simulation. The result is a highly robust and computationally efficient model capable of providing the material flow and temperature history across the domain. As material history determines the local microstructure and ultimately weld strength, an accurate and detailed physics-based model has the potential to accelerate SR-FSW process development. The model is highly adaptable to changes in process parameters, tool design, or alloy.
Process Modeling↗
Quarterly Management Document - FY18, 4th Quarter, Physics-based Creep Simulations of Thick Section Welds in High Temperature and Pressure Applications
During the 4th Quarter of FY18, work on this project focused on determination of the growth behavior of gamma prime precipitates with the intent of determining the growth rate constant as a function of temperature. The derived constitutive equation will be incorporated into the modeling and simulation effort for creep behavior of thick section welds in Alloy 740H for fossil energy power generation applications. Additionally, progress has been made on representing the weld and base metal microstructure using Dream3D which will be used by the modeling and simulation effort to incorporate microstructural effects into the creep behavior.
36 MATERIALS SCIENCE↗
Laser-Welded Seals for Polymer-Free Glass/Glass Modules
This project explored the use of femtosecond laser welding to form strong, hermetic seals for glass/glass modules. The results showed that glass/glass fs laser welds, when coupled to a new module design, are strong enough to enable a polymer-free module, potentially extending warrantees and forming an easily-recycled product.
DuraMAT↗
Microstructural Characteristics, Mechanical Properties, and Corrosion Behavior of Field-Assisted Diffusion Welded Alloy 617
This study investigated the microstructural characteristics, mechanical response, and corrosion resistance of Alloy 617 diffusion welded by electric field-assisted sintering (EFAS). The microstructure exhibited good grain boundary (GB) migration across the interface and flat interface in the samples bonded at different conditions. Graded grain size was observed, with grain coarsening being more significant near sample surface due to EFAS-induced temperature gradient. Tensile testing revealed that the specimens fractured in the matrix away from the interface. The peak strength of 807 MPa was obtained in the samples welded at 1000°C. The materials obtained at 1100°C exhibited reduced tensile strength but improved ductility. Strain maps revealed by digital image correlation showed the flat interfaces were less ductile compared to the matrix. The hardness reduced near sample surfaces due to enlarged grains induced by temperature gradient. The interfaces with GB migration exhibited improved corrosion resistance in molten salt compared to the flat interfaces.
36 - MATERIALS SCIENCE↗
Welding of Stainless Materials
It would appear that welds in some stainless steels, heat-treated in some practicable way, will probably be found to have all the resistance to corrosion that is required for aircraft. Certainly these structures are not subjected to the severe conditions that are found in chemical plants.
WELDING↗
Comparative Study of Oxides Formed on Fusion Zone and Base Metal of Laser Welded Zr-1.0Sn-1.0Nb-0.1Fe Alloy
Numerous studies have primarily focused on the corrosion mechanism of zirconium alloy base metal. However, the corrosion resistance of weld beads or seams is of vital importance in the degradation of structural components in the reactor. In the present work, the corrosion resistance of the fusion zone and base metal of laser welded zirconium alloy joints was comparatively investigated. The microstructure morphologies, phase structures and strain fields of oxide films formed on fusion zone and base metal were observed and analyzed. The oxide thickness of the fusion zone was thicker than that of the base metal with prolonged corrosion. Compared to the base metal, the lower density of dislocations and level of strain values in the oxide film of the fusion zone indicated that the stress in the oxide film was lower. The phase transition from the tetragonal ZrO{sub 2} to the monoclinic ZrO{sub 2} could be suppressed due to the high level of stress, resulting in the better corrosion resistance of the base metal. Moreover, the second phase particles and non-βZr phase in the base metal contributed to the better corrosion resistance.
36 MATERIALS SCIENCE↗
Effect of laser welding on deformation mechanisms in irradiated austenitic stainless steel
In this work, deformation mechanism of a laser weld on neutron irradiated AISI 304L stainless steel was studied by in-situ microcompression test at room temperature. The deformation-induced austenite-to-martensite phase transformation occurs in {101}-oriented grains in the irradiated base metal, while deformation twinning prevails in {101}-oriented grains in the weld heat affected zone (HAZ). A high number density of irradiation-induced voids in the base metal provide sufficient nucleation sites for the austenite-to-martensite phase transformation under compression at room temperature. A deformation map is established to predict critical twinning stress for face-centered cubic (fcc) metals and alloys. Our study suggests that irradiation can tailor the deformation-induced phase transformation in austenitic stainless steels.
36 MATERIALS SCIENCE↗
Force reduction of friction stir welding and processing of steel
Friction stir welding and processing (FSW&P) is considered as a new fabrication method for canisters and repair of existing dry cask storage system canisters (generally made of austenitic stainless steel). Low heat input compared to fusion joining processes and grain refinement associated with low-temperature FSW&P result in a material with improved mechanical properties and equivalent generalized corrosion performance relative to the base metal. But FSW&P of austenitic stainless steel requires significant tool forge axis force to produce a weld (or a run). Exploratory runs utilizing forge axis force control were conducted to investigate the minimum force required to achieve defect-free runs. The correlation between forge axis force and resultant plunge depth was also investigated. Furthermore, detailed microstructural characterization was conducted to display the microstructural variation within the nugget zone.
36 MATERIALS SCIENCE↗
MaterialsMap: A CALPHAD-based tool to design composition pathways through feasibility map for desired dissimilar materials, demonstrated with resistance spot welding joining of Ag-Al-Cu
Assembly of dissimilar metals can be achieved by different methods, for example, casting, welding, and additive manufacturing (AM). However, undesired phases formed in liquid-phase assembling processes due to solute segregation during solidification diminish mechanical and other properties of the processed parts. In the present work, an open-source software named MaterialsMap, has been developed based on the CALculation of Phase Diagrams (CALPHAD) approach. The primary objective of MaterialsMap is to facilitate the design of an optimal composition pathway for assembling dissimilar alloys with liquid-phases based on the formation of desired and undesired phases along the pathway. In MaterialsMap, equilibrium thermodynamic calculations are used to predict equilibrium phases formed at slow cooling rate, while Scheil-Gulliver simulations are employed to predict non-equilibrium phases formed during rapid cooling. Additionally, by combining these two simulations, MaterialsMap offers a thorough guide for understanding phase formation in various manufacturing processes, assisting users in making informed decisions during material selection and production. As a demonstration of this approach, a compositional pathway was designed from pure Al to pure Cu through Ag using MaterialsMap. The design was experimentally verified using resistance spot welding (RSW).
36 MATERIALS SCIENCE↗
Effect of hook characteristics on the fracture behaviour of dissimilar friction stir welded aluminium alloy and mild steel sheets
Under tensile shear loading, fracture modes of dissimilar lap welds produced by friction stir scribe technology were studied. Three fracture modes were observed. For zone A fracture, the initial crack was restrained, and the joint ultimately fractured in the base mild steel. For zone B fracture, the initial crack progressed through the aluminium sheet just above the Al/steel interface. For zone C fracture, the initial crack proceeded along the steel hook to the aluminium sheet surface. Fracture mode and joint strength were greatly influenced by steel hook size, and the steel hook size was affected by welding parameters and tool scribe height. In this study, the experimental joint strength achieved the calculated joint load limit.
Wang, Tianhao↗
Torch End-Effector and TIG Electrode Changeout Design for a TIG Welding Robot Used in Metal Big Area Additive Manufacturing
Metal Big Area Additive Manufacturing (mBAAM) is a promising approach to large-scale metal additive manufacturing (AM) or 3D printing. The mBAAM system uses an arc-based wire-fed welding robot to build metal parts. A multi-degree-of-freedom robotic arm is known for its extensive range of motion and reliable tool handling. Attaching a torch end-effector to a robotic arm gives it welding capabilities; however, this decreases the motion range and dynamics of the robot. As a result, build volume and printing accuracy are decreased. Additionally, only a portion of time is spent printing in an arc-based process. Maintenance leads to downtime on the system. In a tungsten inert gas (TIG)-based process, the torch electrode wears out over time and must be changed to avoid defective deposition. This paper proposes an approach for a compact torch end-effector to improve the robot’s build volume. This paper also proposes an approach to reducing non-printing process time by designing and implementing a semi-automated electrode changing system.
Masuo, Chris↗