General Considerations Regarding the Structural Design of High-Performance Ships

Abstract

Reliability of structures is an overriding consideration in the design of high-performance, weight-critical ships which require design with new materials having high strength-to-weight ratios. These high-strength materials can be susceptible to catastrophic failure in the presence of small flaws, such that the initiation and propagation of cracks by cyclic loading of the structure is of the utmost concern. Techniques for dealing with these problems, as they relate to structural reliability, are discussed, and the close relationship between problems of high-performance ships and aircraft is examined. The current need to rely on large-scale validation testing of vehicle structure and structural details is examined, with particular attention to the requirements for high-performance ship structures."Air Cushion Vehicles have an inherent over-the-beach capability that makes them extremely well suited for amphibious assault or possibly Arctic over-the-ice roles." Rear Admiral N. Sonenshein, former Commander, Naval Ship Systems Command [1].5"Hydrofoils are best suited for high-speed, all-weather missions, such as patrol and interdiction. The demonstrated ability of PCH and the PGH's (Patrol Craft Hydrofoil and Patrol Gunboat Hydrofoil) to maintain speed in extremely high sea states is a proven accomplishment." [1]."To go to the SES (surface effect ship, with rigid sidewalls), the exact mission for these have not been defined because this is new technology" [1]. However, Admiral Elmo R. Zumwalt, former Chief of Naval Operations, has proposed the hard sidewall surface effects vessel that can travel at 80 knots to serve as a small aircraft carrier. A small (2000 ton) SES also offers a platform which could be developed in greater numbers to perform a portion of the ASW surveillance mission [2]. The PURPOSE of this paper is to review the fatigue and fracture aspects of today's ship, submarine, and aircraft structures and, through lessons learned, project the technical needs from these experiences to the design of future high-performance surface ships. The paper synthesizes the overall technical considerations of fatigue and fracture requirements for ships and aircraft structures for the benefit of designers and research managers, and suggests to research scientists areas needing additional research effort. Major attention is given to the application of submarine and aircraft materials and structures technologies to advanced high-performance ships. These structural performance requirements are consolidated in terms of a ‘hull-subsystem’ to (a) relate the structural subsystems to total system program managers, (b) acquaint these system managers with the structural validation tests necessary to assure design of reliable ships for the new types of service called upon by today's commercial and military demands, and (c) make them better aware of available technology and facility resources relevant to validation of structural performance.