1. ONR FNC “Aluminum Corrosion Control and Prevention” Program 3 Area 2: Portable FSW Repair Tool
NSRP Welding Panel Meeting
Appleton, WI
17-18 April 2018
Tim Freidhoff, Dan George, Jay McHenry, Paul Sleppy, Mark Smitherman – CTC
Dr. Anthony Reynolds – USC
Dr. Maria Posada, Dr. Kim Tran – NSWCCD
Dr. Airan Perez – ONR

2. What is “Future Naval Capability (FNC)?”
A significant research and development program by the Office of Naval Research (ONR)
About 30% of ONR’s budget goes to FNC programs
Collaboration of Navy Research, Requirements, Acquisition, and Fleet Forces to determine requirements and gaps
A “gap” is any required capability that is not currently achievable
FNC programs are “near term” or 2-4 years to maturation
Requires a transition agreement between ONR and acquisition
All programs are driven by requirement
Mature solution to TRL 6- ‘Prototype tested in relevant environment’
FNC programs align to 11 functional ‘Pillars’
Meeting exit criteria and a viable transition path are essential

3. Source: www.globalsecurity.org
Background
Due to their combination of good strength, toughness, weldability, and corrosion resistance, the use of 5000 series aluminum alloys are essential for reaching the design performance required for several ship classes.
However, after years of exposure to elevated in-service temperatures, these aluminum alloys can become sensitized.
Sensitized aluminum is highly susceptible to pitting and stress corrosion cracking, and the high levels of sensitization encountered on these ships renders the material unweldable.
Weld repairs of cracks or inserts in sensitized material requires expensive, special treatments and complex welding procedures; in many cases, repair requires complete material replacement with large panel inserts.
Source:

4. Objective
Develop a man-portable, robust, and versatile Friction Stir Welding (FSW) machine to perform in-situ repairs of cracks in sensitized aluminum.
FSW is ideally suited for repair of cracks in sensitized 5000 series aluminum alloys.
The process has been demonstrated to produce high-strength and quality welds even in the most highly sensitized materials.
As a machine-driven, solid-state welding process, this weld quality is highly repeatable and very production friendly.

5. Conventional FSW tools
What is FSW?
Joining process that offers significant advantages over conventional arc welding methods, especially for lower melting temperature materials like aluminum.
FSW utilizes friction between the tool and material to heat (but not melt), soften, and “stir” material across the joint.
Direction of travel
Conventional FSW tools
CTC photo

6. Figure 1. Typical FSW machine
Challenge
Developing a small, light weight, FSW system that can be easily transported shipboard to perform repairs.
Typical FSW machines (Figure 1) are generally large, heavy stationary equipment to handle high forces to stabilize the tool, traverse tool along work-piece, and hold work-piece stationary during the process.
CTC photo
Figure 1. Typical FSW machine

7. Solution
Use of self-reacting, fixed gap bobbin tool (Figure 1) reduces weld forces, minimizing size and weight of machine (Figure 2).
CTC photo
Figure 1. Fixed gap bobbin tool
Illustration courtesy TWI
Figure 2. Portable FSW machine
PATENT PENDING

8. Portable FSW Machine Progress
Developed machine to weld round and obround inserts (Figure 1).
Evaluated machine shipboard to confirm potential to repair cracks (Figure 2).
Performed mechanical testing, macros, and non-destructive tests to confirm acceptable weld quality.
Executing Design of Experiments, which leads to qualification.
Figure 1. Round and obround inserts
Figure 2. Crack repair shipboard
PATENT PENDING

9. Other Potential Applications
The PFSW repair tool was developed for sensitized crack repair on CG 47 class cruisers, but IT HAS POTENTIAL USE FOR OTHER APPLICATIONS.
PATENT PENDING

10. Questions?
Contact:
Mark Smitherman
(c)