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Underwater Repair Procedures for Ship Hulls (Fatigue and Ductility of Underwater Wet Welds)

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Commercial ships may experience damage below the waterline from a variety of causes. Due to the significant costs and the time-consuming nature of unscheduled or emergency drydocking of a ship for repair, there is a clear need for the development of alternate repair methods which preclude having to drydock the ship. An area of ship repair which has the potential to accomplish this objective involves the use of underwater wet welding. A large amount of testing has been performed in recent years to characterize the properties of underwater wet welds, and indicates that this repair method has promise. This project addresses two significant technical areas relating to wet welds 1 Fatigue performance and 2 Low tensile elongation properties of wet welds. Fatigue performance was evaluated by testing underwater wet butt welds fabricated in 3 8-inch ASTM A 36 steel, using E7014 Type electrodes. The underwater wet welds were fabricated in fresh water at a depth of 30 feet, using a wet welding procedure qualified to the standards of ANSIAWS D3.6-89, for Type B welds. Fatigue testing was performed on transverse weld specimens, with and without backing bars, subjected to cyclic axial tensile loading. Findings indicated that 1 The S-N data for the underwater wet welds without backing bars have fatigue strength levels comparable to dry surface welds, and 2 the mean fatigue life of underwater wet weld specimens with backing bars was found to be about 50 lower than the mean fatique life of specimens without backing bars.

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Approved for public release; distribution is unlimited. Document partially illegible.

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