|
Friction Stir Welding
Definition
Friction Stir Welding is a solid-state metal joining process producing high-strength, defect-free joints in metallic materials. The process employs a pin tool (see photo) with a low rotational speed and applied pressure that "mechanically stirs" two parent materials together to produce a uniform weld.
NCAM Experience
Between June 2002 and October 2003, NCAM was involved in a program that advanced the technology of Friction Stir Welding and which used NCAM's resources to demonstrate an advanced metallic manufacturing technology. As a result of that program, NCAM operates a Universal Weld System (UWS) for the production of complex contour hardware.
Image right: UWS with full-scale demonstration weld fixture mounted on the turntable. Image Credit: LMSSC-MO.
The Program
In June 2002, NASA's Marshall Space Flight Center awarded a Next Generation Launch Technology (NGLT) contract to the University of New Orleans Research and Technology Foundation (UNOR&TF) to advance the Technology Readiness Level of Self-Reacting Friction Stir Welding (SRFSW), specifically the advancement of this technology as applied to welding large-scale, complex contour hardware.
Subsequently, UNOR&TF issued subcontract "Space Launch Initiative/Friction Stir Welding Risk Reduction Program" to Lockheed Martin Space Systems Company-Michoud Operations (LMSSC-MO). (Read the Abstract for this research program.)
Since the goal of this 17-month program was to advance the Technology Readiness Level of this technology, the program included the installation and activation of the Universal Weld System at NASA's Michoud Assembly Facility in New Orleans, where NCAM is located. The program was designed to also include:
- weld process development,
- an intermediate scale hardware demonstration,
- a full scale hardware demonstration.
The Universal Weld System was required to complete the full scale hardware demonstration. Funding for the UWS was supplied by the Louisiana Department of Economic Development and NASA through the NGLT Self Reaction Friction Stir Welding complex curvature risk reduction program.
Program Demonstrations
The intermediate scale demonstration took place in April 2003. This demonstration joined three gore panels, part of a liquid oxygen tank dome for a commercial reusable launch vehicle program. Three gore panels comprise a quarter panel, or one quarter of a full dome.
Image top right: Completed Intermediate Scale Quarter Panel. Image Credit: LMSSC-MO.
Image bottom right: Completed Full-Scale ET Quarter Panel. Image Credit: LMSSC-MO.
The full scale demonstration took place in September 2003, and involved welding together three Space Shuttle External Tank (ET) elliptical dome gore panels, forming one quarter dome.
Program Results
By the conclusion of the 17-month program, over 230 different welds were performed on two different alloys currently used in the design of launch vehicles, one of which is a prime candidate for the next generation launch vehicle. The completion of this program not only advanced the technology of Self Reacting Friction Stir Welding, it established and activated the Universal Weld System at Michoud Assembly Facility that can be used in future technology advancement programs and for production of future hardware that requires Friction Stir Welding of complex contour hardware.
| |
 |
| |
Image above: Universal Weld System. Image Credit: LMSSC-MO. |
Universal Weld System Specifications
Machine Type
- MTS 6 axis of motion weld head
Capacity
- 16 ft. x 21.5 ft. x 10 ft. of linear motion
- 2 axis of gimbal motion of the weld head
- 30 ft. rotary table with one rotational degree of freedom
Features
- Self reacting pin tool technology
- Combined axis of motion allows for complex curvature
welding
- Latest controlled/programming system
- One of the largest, most advanced FSW machine in the world
|
