an operational hydrostatic pressure of 10,000 psi, would also withstand 

 the bending moments generated inside the hull by launching from a shipboard- 

 mounted air-operated launcher. One other requirement complicated the 

 design further, the requirement being that the joint be flush with the 

 external hull surface so as not to generate additional hydrodynamic drag 

 for the hull. Of the three designs considered, only one has been found to 

 satisfy all the above-mentioned operational requirements. One of the 

 designs (Figure 8a), an internal expanding wedge joint, was rejected 

 because it imposed tensile stresses on the ceramic flanges when two shell 

 sections were locked together with this joint. In this particular case, 

 the tensile stresses were caused by the upward thrust of the joint wedges 

 used to draw the two adjoining cylinders' flanges together. The other 

 design, an external wedge band joint (Figures 8b and 9), was rejected 

 because the deep grooves cut in the external surface of the cylinder would 

 cause shear stresses to be generated in the ceramic under column loading 

 imposed on the hull by hydrostatic pressure. To determine accurately at 

 what depth the shear failure of the ceramic cylinders would occur if 

 joined by such a joint, two hemisphere capped ceramic cylinders were 

 joined by the external wedge band joint and were tested hydrostatically 

 to destruction. The shear failure, which occurred at 1480 psi, proved 

 that this joint, although simple and fast in its lock operation, causes 

 the cylinder to fail in shear. The only externally flush joint design 

 that was found to meet the design depth requirement and at the same time 

 did not introduce any additional stresses into the cylinder under hydro- 

 static loading was the breech- lock joint (Figure 10), When two ceramic 

 cylinders of identical dimensions as those that were equipped with external 

 wedge band joints were fitted with the breech- lock joint, they success- 

 fully withstood 16,000 psi of hydrostatic pressure without implosion. Thus 

 a workable design was born for hydrodynamically streamlined joining of 

 ceramic shells of cylindrical shape for deep submergence applications. 

 Regardless of diameter, cylindrical sections could be joined now into hulls 

 of any length to carry the desired payload to the ocean's greatest depths. 

 Needless to say, a continuous screw thread could be substituted for the 

 interrupted screw thread if extremely high bending moments were to be 

 carried by the joint and the additional time and effort required to lock 

 a continuous screw joint were of no particular consequence. If the require- 

 ment that the external joint surface be flush with the ceramic surface is 

 waived for applications where extremely smooth hydrodynamic surfaces are 

 not of importance, then another joint design can be added to the already 

 described series of joints. This joint, a modified wedge band design 

 (Figures 8d and 11) , incorporates all that is best in a wedge band concept 

 without having any of the drawbacks that can be associated with this joint 

 concept. It does not require 0- rings for sealing or any threads on the 

 metallic joint surfaces. During locking of ceramic sections, only compres- 

 sive stresses are generated in them, and bending moments applied to the 



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