ADVANCED MATERIALS & PROCESSES | MAY/JUNE 2023 26 to shipbuilding for a wide variety of applications and vessels: • Freezer panels on fishing boats for storing fresh fish • Honeycomb panels for ship cabin walls • Decks and walls on high-speed ferries • Joining 5xxx and 6xxx sheet and extruded parts • Prefabricated panels on boats ranging from cruise ships to military vessels NAVAL VESSELS Navies around the world have used aluminum for patrol vessels with single hull designs adapted from steel ship construction. In 1954, a Japanese Coast Guard all-aluminum patrol boat named the Arakaze was commissioned. The Japanese Maritime Self-Defense Force (JMSDF) built additional and larger vessels based on their positive experience with the Arakaze[10]. In 2000, the U.S. Navy decided to build a series of vessels intended for service near the U.S. coastline. These vessels were designed in large part along the lines of the “fast ferry” catamarans introduced by the Australian shipyards, Austal and and Incat[5]. These littoral combat ships (LCSs) were designed to be fast and nimble, capable of minesweeping, interception, and antisubmarine activity. The 1030-m2 flight deck could handle vertical take-off and landing (VTOL) aircraft. The LCS program evaluated two concepts: a single V-shaped monohull design and a catamaran trihull design based on fast ferries. Austal’s shipyard in Mobile, Alabama, built several LCSs including the USS Independence (Fig. 5), which had a top speed of 44 knots (51 mph), powered by two gas turbine-powered water jets. The Independence launched in April 2008 and remained in service for 10 years. There were significant operational difficulties, in part due to inexperience with aluminum ship structures and galvanic corrosion. By 2020, the program was deemed to have met its goal of evaluating the littoral ship technologies. All the LCS vessels were placed on inactive reserve status in early 2021 and marked for disposal in 2022[11]. In 2017, Austal USA delivered the USNS Yuma, the eighth expeditionary fast transport (EPF) vessel, to the U.S. Navy[11]. The 338-ft-long catamaran can transport a 600-ton payload 1200 nautical miles at an average speed of 35 knots. The design allows for a shallow draft compared with traditional V hulls. The ship’s flight deck can also accommodate a variety of aircraft (Fig. 6). Approximately 700 tons of wrought aluminum products (plate, extrusions, and forgings) were used in the construction of the Yuma. FSW panels and custom extrusions were used, and final assembly involved a combination of TIG and gas metal arc welding. Bare aluminum is used above the waterline, but the hull is painted below. SUMMARY Aluminum was recognized as a promising material for marine construction from the early days of the industry. But the development of 5xxx alloys and large production capacity made aluminum use more technically and economically possible beginning in the 1950s. The variety of aluminum vessels ranges from small fishing boats and fast ferry catamarans to cruise ships and military vessels. All benefit from the lightweight alloys, low maintenance costs, and easy repairability. Other benefits of using aluminum in marine applications include formability, corrosion resistance, and availability in various product forms. Although aluminum can be conventionally welded to form a watertight structure, friction stir welding has been used during the past 25 years to reduce fabrication costs and construction time. Corrosion issues with higher magnesium (>3%) alloys have been addressed with the development of a new temper and related testing requirements. ~AM&P For more information: Robert Sanders, Sanders Aluminum Consulting LLC, Chapin, SC, +1 803.580.1487, sandere52 @gmail.com. References 1. M.B.W. Graham and B.H. Pruitt, R&D For Industry: A Century of Technical Innovation at Alcoa, p 56, Cambridge University Press, U.K., 1990. Fig. 5 — Littoral combat ship USS Independence on patrol. Courtesy of N. Kontodiakos/U.S. Navy. Fig. 6 — USNS Yuma launched in 2017. Courtesy of N. Kontodiakos/ U.S. Navy.
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