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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1998

Friction Stir Welding Development

The research of this summer was a continuation of work started during the previous summer faculty fellowship period. The Friction Stir Welding process (FSW) patented by The Welding Institute (TWI), in Great Britain, has become a popular topic at the Marshall Space Flight Center over the past year. Last year it was considered a novel approach to welding but few people took it very seriously as a near term solution. However, due to continued problems with cracks in the new aluminum-lithium space shuttle external tank (ET), the friction stir process is being mobilized at full speed in an effort to mature this process for the potential manufacture of flight hardware. It is now the goal of NASA and Lockheed-Martin Corporation (LMC) to demonstrate a full-scale friction stir welding system capable of welding ET size barrel sections. The objectives this summer were: (1) Implementation and validation of the rotating dynamometer on the MSFC FSW system; (2) Collection of data for FSW process modeling efforts; (3) Specification development for FSW implementation on the vertical weld tool; (4) Controls and user interface development for the adjustable pin tool; and (5) Development of an instrumentation system for the planishing process. The projects started this summer will lead to a full scale friction stir welding system that is expected to produce a friction stir welded shuttle external tank type barrel section. The success of this could lead to the implementation of the friction stir process for manufacturing future shuttle external tanks.

Romine, Peter L.↗
DOE OSTI2023

Microstructural, Corrosion, and Mechanical Characterization of Friction Stir Welded Al 6022-to-ZEK100 Mg Joints

Friction stir welded (FSW) aluminum–magnesium lightweight vehicle joints have gained significant interest due to their high strength-to-weight ratio. In this work, the corrosion resistance of this material is analyzed through electrochemical tests, which include open circuit potential (OCP) inspection and potentiodynamic polarization (PD) scanning. Weight loss measurements tested the corrosion rate of the FSW weld through cyclic corrosion testing (CCT) according to the standard SAEJ 2334. Mechanical properties were also investigated, including lap-shear strength, micro- and nano-hardness mapping, and true stress–strain curves as a function of local processing history. The electrochemical results indicate that the center weld zone’s corrosion property stays between the two base alloys. Indentation-based testing demonstrated that the weld zone behaves differently from base alloys. Lap shear strength surprisingly did not drop much even after eight weeks of cyclic corrosion tests, indicating that the joint did not allow any ingress of the electrolyte.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Corrosion Testing of Friction Stir Welded 304L Stainless Steel

A preliminary study on the microstructural characteristics and stress corrosion cracking susceptibility of a friction stir welded (FSW) 304L stainless steel plate was carried out. The weld examined was characterized by several typical microstructural features of friction stir welds including a gradient of dynamically recrystallized microstructure with distinct material flow patterns reflective of the complex distribution of thermomechanical histories. Evidence of process-induced microstructural sensitization was lacking Immersion testing of the friction stir welded plate in boiling magnesium chloride solution indicated the FSW region was more susceptible to SCC than the base 304L material, especially along the weld toes. The microstructural origins of this SCC susceptibility are not clear, but it is likely driven by residual stress imparted by the welding process. Future work will focus on direct examination of the SCC damaged microstructure and residual stress of the weld zone to further clarify the operative characteristics controlling SCC susceptibility.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS2002

Friction-Stir Welding of Aluminum For the Space Program

The Marshall Space Flight Center is developing and characterizing the friction stir welding process for the Space Shuttle and other space programs. This revolutionary process, invented and patented by The Weld Institute in England, offers tremendous advantages for joining aluminum for high performance applications. It is particularly suited for advanced aluminum-lithium alloys, such as 2195, the primary structural alloy used in the External Tank. The friction stir welding process joins metals with minimal heat input, resulting in high-strength joints with high ductility. It is a simple process to demonstrate using a common milling machine for sample parts, but relatively expensive to implement on large-scale hardware, due to the high cost of tooling needed to handle the high forging pressures characteristic of the process. Recent developments at the Marshall Space Flight Center have demonstrated friction stir welding on linear joints up to 5 meters (15 ft.), with material thickness ranging between 2.5 mm and 16.5 mm (0.100" to 0.650"). High efficiency weld joints have been produced in aluminum from the 2000, 5000, and 6000 series alloy systems. A "retractable pin tool" system was patented by MSFC that allows use of friction stir welding for joints with changing material thickness, and with less rigid tooling than previously considered. This presentation will describe the details of alloys welded to-date and technical advances under development at MSFC. These developments could have substantial benefit to industrial applications for welding aluminum.

Jones, Clyde S.↗
DOE OSTI2016

Fabrication of thick multilayered steel structure using A516 Grade 70 by multipass friction stir welding

In the present work, a thick-sectioned multilayered steel structure was fabricated by multipass friction stir welding on A516 Grade 70 steel. Tensile strength of the multilayered samples was comparable to that of the base metal. Failure was located in the base metal when a defect-free sample was tested. Charpy impact toughness was higher in the stir zone and heat affected zone than in the base metal. Higher microhardness values were found in the stir zone and heat affected zone than the base metal due to grain refinement and modification of the microstructures. Consequently, improved mechanical properties compared to the base metal were found in the weld zones of friction stir welded A516 Grade 70 steel.

36 MATERIALS SCIENCE↗
NASA NTRS2003

Friction Stir Welding of Tapered Thickness Welds Using an Adjustable Pin Tool

Friction stir welding (FSW) can be used for joining weld lands that vary in thickness along the length of the weld. An adjustable pin tool mechanism can be used to accomplish this in a single-pass, full-penetration weld by providing for precise changes in the pin length relative to the shoulder face during the weld process. The difficulty with this approach is in accurately adjusting the pin length to provide a consistent penetration ligament throughout the weld. The weld technique, control system, and instrumentation must account for mechanical and thermal compliances of the tooling system to conduct tapered welds successfully. In this study, a combination of static and in-situ measurements, as well as active control, is used to locate the pin accurately and maintain the desired penetration ligament. Frictional forces at the pin/shoulder interface were a source of error that affected accurate pin position. A traditional FSW pin tool design that requires a lead angle was used to join butt weld configurations that included both constant thickness and tapered sections. The pitch axis of the tooling was fixed throughout the weld; therefore, the effective lead angle in the tapered sections was restricted to within the tolerances allowed by the pin tool design. The sensitivity of the FSW process to factors such as thickness offset, joint gap, centerline offset, and taper transition offset were also studied. The joint gap and the thickness offset demonstrated the most adverse affects on the weld quality. Two separate tooling configurations were used to conduct tapered thickness welds successfully. The weld configurations included sections in which the thickness decreased along the weld, as well as sections in which the thickness increased along the weld. The data presented here include weld metallography, strength data, and process load data.

Adams, Glynn↗
NASA NTRS2012

Development of Inspection for Friction Stir Welds for Rocket Fuel Tanks

During development of the Ares I weld processes nondestructive and destructive testing were used to identify and characterize defects that occurred. These defects were named and character noted. This catalogue of defects and characteristics was then used to develop inspection methods for Self Reacting Friction Stir Welds (SR ]FSW) and Conventional Friction Stir Welds (C ]FSW). Dye penetrant, eddy current, x ]radiography, single element ultrasonic, and phased array ultrasonic (PAUT) inspection procedures were developed to target the expected defects. Once the method procedure was developed a comparison was performed to allow for selection of the best inspection method. Tests of the effectiveness of the inspection were performed on purposely fabricated flawed specimens and electrodischarge machined notches. The initial test results prompted a revisit of the PAUT procedure and a redesign of the inspection. Subsequent testing showed that a multi ]angle PAUT inspection resulted in better detection capability. A discussion of the most effective orientations of the PAUT transducer will be presented. Also, the implementation of the inspection on production hardware will be presented. In some cases the weld tool is used as the transducer manipulator and in some cases a portable scanner is used

Russell, Samuel S.↗
DOE OSTI2018

Microstructure Evolution and Mechanical Properties of High-Speed Friction Stir Welded Aluminum Alloy Thin Plate Joints

Sound friction stir welded (FSW) joints of 6061-T6 aluminum alloy sheets with an 0.8 mm thickness were obtained at conventional speed (2000 rpm, 300 mm/min) and high speed (11,000 rpm, 1500 mm/min). The recrystallization mechanism, precipitate evolution, mechanical properties and fracture behavior were investigated in detail. Microstructure analyses revealed that the grain structure evolution in the nugget zone (NZ) was dominated by continuous dynamic recrystallization. In the process of FSW, high speed facilitates the formation of finer equiaxed recrystallized grains, higher density of dislocations and substructures, and a larger number of precipitates in the NZ compared to the conventional speed, which further significantly improves the hardness and tensile strength of the joints. The maximum tensile strength was obtained with 292.6 MPa, 83.2% for the 6061-T6 aluminum alloy and 122.6% for the conventional-speed FSW joints. This work provides an effective method for preparing FSW aluminum alloy thin plate joints with excellent mechanical properties.

36 MATERIALS SCIENCE↗
NASA NTRS2003

Characterization of Plastic flow and Resulting Micro-Textures in a Friction Stir Weld

The mechanically affected zone of a friction stir weld (FSW) cross section exhibits two distinct microstructural regions, possibly the residues of two distinct currents of metal in the FSW flow process. In this study the respective textures of these microstructural regions are investigated using orientation image mapping (OIM).

Schneider, J. A.↗
NASA NTRS2000

Demonstration of a Large-Scale Tank Assembly via Circumferential Friction Stir Welds

A collaborative effort between NASA/Marshall Space Flight Center and the Michoud Unit of Lockheed Martin Space Systems Company was undertaken to demonstrate assembly of a large-scale aluminum tank using circumferential friction stir welds. The hardware used to complete this demonstration was fabricated as a study of near-net- shape technologies. The tooling used to complete this demonstration was originally designed for assembly of a tank using fusion weld processes. This presentation describes the modifications and additions that were made to the existing fusion welding tools required to accommodate circumferential friction stir welding, as well as the process used to assemble the tank. The tooling modifications include design, fabrication and installation of several components. The most significant components include a friction stir weld unit with adjustable pin length capabilities, a continuous internal anvil for 'open' circumferential welds, a continuous closeout anvil, clamping systems, an external reaction system and the control system required to conduct the friction stir welds and integrate the operation of the tool. The demonstration was intended as a development task. The experience gained during each circumferential weld was applied to improve subsequent welds. Both constant and tapered thickness 14-foot diameter circumferential welds were successfully demonstrated.

Jones, Clyde S.↗
DOE OSTI2015

Characterization of Residual Stress as a Function of Friction Stir Welding Parameters in Oxide Dispersion Strengthened (ODS) Steel MA956

This article characterizes the residual stresses generated by friction stir welding of oxide dispersion strengthened steel MA956 over a series of welding conditions. A plate of MA956 steel was friction stir welded at three conditions: 500 rpm/25 millimeters per minute (mmpm), 400 rpm/50 mmpm and 400 rpm/100 mmpm. The residual stresses across these welds were measured using both x-ray and neutron diffraction techniques. Longitudinal residual stresses up to eighty percent of the yield strength were observed for the 400 rpm/100 mmpm condition. Increasing the traverse rate while holding the rotational speed fixed increased the residual stress levels in the stir zone and at the stir zone-thermomechanically affected zone interface. The stress profiles displayed the characteristic M shape, and the asymmetry between advancing and retreating stress peaks was limited, occurring mainly on the root side of the weld. The large magnitude of the stresses was maintained throughout the thickness of the plates.

36 MATERIALS SCIENCE↗
DOE OSTI2016

An Alternative Frictional Boundary Condition for Computational Fluid Dynamics Simulation of Friction Stir Welding

For better application of numerical simulation in optimization and design of friction stir welding (FSW), this paper presents a new frictional boundary condition at the tool/workpiece interface for computational fluid dynamics (CFD) modeling of FSW. The proposed boundary condition is based on an implementation of the Coulomb friction model. Using the new boundary condition, the CFD simulation yields non-uniform distribution of contact state over the tool/workpiece interface, as validated by the experimental weld macrostructure. It is found that interfacial sticking state is present over large area at the tool-workpiece interface, while significant interfacial sliding occurs at the shoulder periphery, the lower part of pin side, and the periphery of pin bottom. Due to the interfacial sticking, a rotating flow zone is found under the shoulder, in which fast circular motion occurs. The diameter of the rotating flow zone is smaller than the shoulder diameter, which is attributed to the presence of the interfacial sliding at the shoulder periphery. For the simulated welding condition, the heat generation due to friction and plastic deformation makes up 54.4 and 45.6% of the total heat generation rate, respectively. In conclusion, the simulated temperature field is validated by the good agreement to the experimental measurements.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Friction stir welding and processing of oxide dispersion strengthened (ODS) alloys

A method of welding including forming a filler material of a first oxide dispersoid metal, the first oxide dispersoid material having first strengthening particles that compensate for decreases in weld strength of friction stir welded oxide dispersoid metals; positioning the filler material between a first metal structure and a second metal structure each being comprised of at least a second oxide dispersoid metal; and friction welding the filler material, the first metal structure and the second metal structure to provide a weld.

36 MATERIALS SCIENCE↗
NASA NTRS2013

Friction Stir Weld Application and Tooling Design for the Multi-purpose Crew Vehicle Stage Adapter

The Multi-Purpose Crew Vehicle (MPCV), commonly known as the Orion capsule, is planned to be the United States' next manned spacecraft for missions beyond low earth orbit. Following the cancellation of the Constellation program and creation of SLS (Space Launch System), the need arose for the MPCV to utilize the Delta IV Heavy rocket for a test launch scheduled for 2014 instead of the previously planned Ares I rocket. As a result, an adapter (MSA) must be used in conjunction with the MPCV to account for the variation in diameter of the launch vehicles; 5.5 meters down to 5.0 meters. Prior to ight article fabrication, a path nder (test article) will be fabricated to ne tune the associated manufacturing processes. The adapter will be comprised of an aluminum frustum (partial cone) that employs isogrid technology and circumferential rings on each end. The frustum will be fabricated by friction stir welding (FSW) three individual panels together on a Vertical Weld Tool (VWT) at NASA Marshall Space Flight Center. Subsequently, each circumferential ring will be friction stir welded to the frustum using a Robotic Weld Tool (RWT). The irregular geometry and large mass of the MSA require that extensive tooling preparation be put into support structures for the friction stir weld. The tooling on the VWT will be comprised of a set of conveyors mounted on pre-existing stanchions so that the MSA will have the ability to be rotated after each of the three friction stir welds. The tooling requirements to friction stir weld the rings with the RWT are somewhat more demanding. To support the mass of the MSA and resist the load of the weld tool, a system of mandrels will be mounted to stanchions and assembled in a circle. The goal of the paper will be to explain the design, fabrication, and assembly of the tooling, to explain the use of friction stir welding on the MSA path nder, and also to discuss the lessons learned and modi cations made in preparation for ight article fabrication in support of the 2014 launch of the Orion MPCV.

Alcorn, John↗
DOE OSTI2019

Microstructural Development and Mechanical Properties of Friction Stir Welded Ferritic Stainless Steel AISI 409

This work investigates the effect of friction stir welding process parameters (rotation rate and traverse speed) on the microstructural evolution of friction stir welded (FSWed) ferritic stainless steel (FSS) AISI 409. Optical microscope, scanning electron microscope and electron backscattering diffraction are used to quantitatively assess the development in grain structure and texture. The microstructural development suggested that thermo-mechanical deformation occurs in the stir zone within the austenite/ferrite phase region, ultimately transforming upon cooling into bainitic/ferritic microstructure. The fraction and size of the bainitic/ferritic grains are found to vary through the thickness of the joints. High fractions of coarse ferritic grains are found near the top of the stir zone, and low fraction of fine ferritic grains is found near the bottom of the stir zone. This bainitic/ferritic grain structure resulted in an increase in the hardness of the stir zone by about 74% relative to the base material. The tensile strength of the FSWed FSS joints is almost at the same level of the base material with reduction in the ductility as a result of the increased hardness of the weld zone.

36 MATERIALS SCIENCE↗
NASA NTRS2005

The Plunge Phase of Friction Stir Welding

Torque and plunge force during the initial plunge phase in Friction Stir Welding were measured for a 0.5 inch diameter pin entering a 2219 aluminum alloy plate. Weld structures were preserved for metallographic observation by making emergency stops at various plunge depths. The plunging pin tool is seen to be surrounded by a very fine grained layer of recrystallized metal extending substantially below the bottom of the pin, implying a shear interface in the metal below and not at the tool-metal interface. Torque and plunge force during the initial plunge phase in Friction Stir Welding are calculated from a straight forward model based on a concept to plastic flow in the vicinity of the plunging tool compatible with structural observations. The concept: a disk of weld metal seized to and rotating with the bottom of the pin is squeezed out laterally by the plunge force and extruded upwards in a hollow cylinder around the tool. As the shear surface separating rotating disk from stationary weld metal engulfs fresh metal, the fresh metal is subjected to severe shear deformation, which results in its recrystallization. Encouraging agreement between computations and measured torque and plunge force is obtained.

Nunes, Arthur↗
NASA NTRS2001

Friction Stir Welding of the Space Shuttle External Tank Longitudinal Barrel Welds

Through the implementation of friction stir welding, the safety, reliability, and producibility of the external tank is enhanced. Such fusion procedures are accomplished with the use of a short barrel weld tool or a long barrel weld tool. Forecasted developments in the fusion tooling field include the advent of a universal tool which is capable to fusing all barrel configurations. A wide array of mechanical and electrical controls are described for such a device.

Adams, Glynn↗
NASA NTRS2004

Heat Treatment of Friction Stir Welded 7X50 Aluminum

A method for treating alloy before and after friction stir welding, the method comprising the following steps. First solution heat treating a multiplicity of aluminum-zinc alloy engineered components for a first time period at a first temperature. First air cooling the components in ambient air at room temperatwe until the components are cooled to room temperature. Friction stir welding the components to form an assembly. Second solution heat treating the assembly for a second time period at a second temperature. Additional steps and embodiments are considered.

George E Petter↗