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

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

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: www.globalsecurity.org

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.

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

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

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

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

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

Questions? Contact: Mark Smitherman smitherm@ctc.com (c) 814-248-1569