Fatigue Design Guidance for Surface Ships

This is a NAVAL SURFACE WARFARE CENTER CARDEROCK DIV BETHESDA MD report procured by the Pentagon and made available for public release. It has been reproduced in the best form available to the Pentagon. It is not spiral-bound, but rather assembled with Velobinding in a soft, white linen cover. The Storming Media report number is A137193. The abstract provided by the Pentagon follows: This document contains guidance to design surface ship structures against fatigue failure. In engineering terms, fatigue describes the initiation and growth of cracks and associated damage accumulation which may occur under cyclic loads and their effect on the service life of a structural member. Ships are subjected to fatigue cycles primarily by the action of seawater waves. The guidance provided in this report applies to naval monohull ships of conventional hull form, construction and material. For conventional hull forms, the procedure provides maximum permissible primary design stresses as a function of ship type and structural detail. General guidance is provided for other non- conventional ships. The permissible stresses are based on benchmark analyses of different types of U.S. Navy surface combatants that have successfully completed their service lives without experiencing fatigue crack initiation. A "design" operating scenario in the North Atlantic was chosen for the analyses. For the fatigue damage calculations, a limited number of days is determined to be equivalent to the actual lifetime operating conditions which result in a fatigue life equal to the service life. Results are presented in terms of permissible stress levels and stress concentration factors.