Cylindrical Pressure Hull Research Articles

Active control of low-frequency hull-radiated noise

A theoretical analysis of the active control of low-frequency radiated pressure from a finite cylindrical pressure hull is presented. The control action is implemented through a Tee-sectioned circumferential stiffener driven by a pair of PZT stack actuators. The actuators are located under the flange of the stiffener and are driven out of phase to produce a control moment. This paper examines the effects of control actions, both structurally and acoustically, for a control moment applied around the circumference of the hull. The model considered is a water-loaded finite stiffened cylindrical shell with rigid ends caps. One end of the shell is excited by an axial force while the other end is free. Control action is achieved by using the PZT actuators and stiffener to minimize the structural response and radiated pressure. It was found that the control system was capable of reducing by approximately two-thirds of the radiated pressure for the first three axial modes.

Elastic-Plastic Axisymmetric Failure of Swedge-Stiffened Cylindrical Pressure Hull Under External Pressure

An elastoplastic and geometrically nonlinear analysis of two of Ross's swedge-stiffened pressure hulls subjected to hydrostatic pressure loading is presented. Three commonly used swedge forms—trapezoidal, triangular, and sinusoidal-shaped—are considered. Comparisons on the responses of these three swedge-stiffened shapes are included. The load/displacement relations as well as the distribution of stresses with plastic zone spread phenomena are also illustrated.

Development of a New Concept for Cylindrical Pressure Hulls

The prebuckled cylindrical (PC) shell represents a new structural concept suitable for use in the undersea environment. The externally pressurized PC shell has been shown to be more resistant to buckling failure than a comparable “true” cylinder. The technical feasibility of this new concept has now been realized by the design and construction of a large-scale prototype made entirely of transparent acrylic plastic. The success of this initial effort offers encouragement to further pursue applications of this novel structural form to other uses in the ocean.

Weight Comparison of Ring- vs Ring/Stringer-Stiffened Cylindrical Pressure Hulls

Optimum ring-stiffened cylindrical pressure hulls have slightly lower structural efficiency than optimum ring/stringer-stiffened cylindrical pressure hulls for a constant ocean collapse depth. However, efficiency is achieved in ring/stringer-stiffened hulls with thinner walls which result in significantly higher wall stresses. Example steel and titanium hull designs are presented for collapse depths ranging from 2000 to 7000 ft. Titanium is superior in elastically stressed designs but alloys in either steel or titanium with sufficiently high yield strengths after welding are not available to develop the maximum potential structural efficiency of either configuration at deeper depths. A nondimensional structural optimization analysis which considers the several possible modes of instability and recognizes a number of practical design restraints (for example, a maximum ring/stringer height) is used to obtain these results.