Evaluation of Scale-Model Ceramic Pressure Housing for Deep Submergence Service: Fifth Generation Housings

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The scale model of a 26-inch OD pressure housing assembly for service to a 20,000-foot (6,096-meter) depth was designed, subjected to structural analysis, fabricated from 94-percent alumina ceramic, instrumented with strain gages, and tested to destruction. The scale model consisted of two 12.047-inch OD by 15.375-inch L by 0.434-inch t (30.59-centimeter OD by 39-centimeter L by 1.1-centimeter t) monocoque cylinders of 94-percent alumina ceramic, joined by a titanium coupling with an integral T-ring stiffener, and closed off with two ceramic hemispherical bulkheads. The hemispherical bulkheads incorporated a short cylindrical skirt the thickness of which matched the wall thickness of the cylinders. The ends of both the cylinders and hemispheres were enclosed in Naval Ocean Systems Center (NOSC) Type Mod 1 titanium end caps bonded to the ceramic surfaces with epoxy adhesive. The scale model housing assembly successfully withstood a proof test to 10,000 psi (69 MPa) and 100 pressure cycles to 9,000 psi (62 MPa). In a separate test, one of the ceramic hemispheres from the housing was pressure cycled by itself 500 times to 9,000 psi (62 MPa) without appearance of surface spalling. When pressurized to destruction, the scale-model housing imploded at 11,933 psi (82.3 MPa). The scale-model housing assembly is capable of supporting in seawater a payload of 69 pounds. The structural design, selection of materials, fabrication process, and assembly procedure resulted in a ceramic pressure housing with a 0.61 weight/displacement ratio, acceptable for service to 20,000 feet (6,096 meters). The cyclic fatigue life of the ceramic components exceeded 500 pressure cycles to design depth.