The feasibility of the use of doubler plates as a permanent repair under cyclic loads in a highly corrosive environment will be demonstrated during the proposed Phase I effort. The work plan will include a review of literature, review of use of doubler plates, investigation of corrosion issues, investigation of crack initiation and growth, and investigation of ultimate strength issues. The review of the past use of doubler plates will include consultation with shipyards that have installed doubler plates as temporary repairs and with shipyards that have had to remove them to perform permanent repairs. Means will be found to reduce corrosion when doublers are placed over a corroded plate to which seawater may still gain access. Design of doublers will be developed of maintain the original structural integrity, including ultimate strength and fatigue and fracture strength. Chapter 100, Hull Structures, of Naval ShipsÂ’ Technical Manual will be reviewed and a plan developed for updating it to reflect the results of the proposed research as well as other developments in the maintenance, inspection, and repair of ship structure. A plan will be developed for a Phase II effort to experimentally verify the results of the Phase I effort.
Benefits: A significant reduction in the cost of structural repairs to U.S. Navy ships is anticipated if doubler plates are used as permanent repairs. Avoidance of drydocking for structural repairs can save several hundred thousand dollars per repair. If there were only one such instance per year, the U.S. Navy would save several million dollars over a 10 year period, quickly amortizing the investment in this research. Commercial structural design standards such as those contained in the classification societies would benefit as new performance data of doubler plates is incorporated. This would lead to better monitoring & inspection procedures for these repairs as well as provide a more cost-effective strategy for decisions to permanently repair doubler plates.
Keywords: Corrosion, Inspection, Fatigue Strength , Temporary Repair, Maintenance, Inaccessible Areas
