Polyhedrally stiffened shells for undersea pressure hulls

The polyhedrally-stiffened cylindrical (PC) shell is a structural concept that offers a design alternative to the conventional ring-stiffened cylindrical shell for undersea pressure hulls. Both the defense and commercial ocean industries have a continuing requirement for pressure hulls in underwater systems. A significant percentage of these systems operate in water depths from near surface to 1,500 m, depths well suited to PC pressure hulls. Examples of marine applications include pressure housings for autonomous underwater vehicles, remotely operated vehicles, submersibles, buoys and sonabuoys. In this paper, previous research on PC shells is expanded to include a broader range of materials suitable for undersea pressure hulls. Findings similar to those obtained for composite materials reported earlier have been obtained for aluminum, titanium and steel alloys. Parametric design studies using finite element analysis show that the PC shell can be advantageously used with any of these materials. The undulated polyhedral geometry is shown to provide a substantially greater operating depth than a comparably sized circular cylinder with less control of fabrication tolerances needed. Thus, the PC hull behaves as a stiffened cylinder with the advantage of potentially lower fabrication costs.