joint during launching of the cylindrical buoy generate only modest shear 

 stresses in the ceramic lock flanges as the flanges can be kept extremely 

 short. Wrapping of the cylinders with protective overwraps can restore 

 to the hull its streamlined shape, as then the protruding wedge bands are 

 flush with the overwrap at shallow depths and protrude only moderately at 

 abyssal depths where the overwrap is flattened somewhat by the hydrostatic 

 pressure. 



Q Q 



Although experimental data generated by the author and others^ show 

 that highest bearing stresses are carried only by a ceramic to ceramic 

 joint interface, its application is limited as it requires beveled per- 

 fectly polished hand- lapped surfaces for its successful operation. If 

 ceramic hulls for ASW weapons or oceanographic instrumentation capsules 

 are ever to be mass produced and assembled on an interchangeable basis, 

 tnen hand- lapped and hand- fitted ceramic to ceramic joints cannot be con- 

 sidered a desirable type ^of joint although its bearing stress- carrying 

 ability may be the best among joints. The mechanical shell section joints 

 found workable for deep submergence cylindrical ceramic hulls incorporate 

 the bearing surfaces into a structural ring member of the joint, so that 

 the whole ring material can be considered as a gasket. Since the bearing 

 stresses encountered at the ends of monocoque ceramic cylinders amount at 

 the most to only one half of hoop stresses in the cylinder, the largest 

 bearing stresses that can be expected will be less than 170,000 psi. In 

 the rib- stiffened cylinders- tested ,8 the bearing stresses are further 

 reduced below 170,000 psi by the presence of end flanges, whose bearing 

 area is generally at least two times as large as that of the shell wall 

 between stiffeners. Thus, the maximum bearing stresses that generally 

 have to be contended with at the end flanges of rib- stiffened cylinders 

 are in the vicinity of 60,000 psi. Such a bearing stress is low enough 

 where a variety of metallic joint materials can withstand it. There is, 

 however, one further requirement that must be considered when selecting 

 the material for the structural numbers of the ceramic shell section 

 joint. The additional requirement is the compliance of the joint under 

 hydrostatic loading. 



If the metallic joint behaves as an integral part of the ceramic shell 

 during hydrostatic loading, then it is a good joint and will not cause 

 any additional stresses in the ceramic portions of the shell joint. On 

 the other hand, a severe mismatch between the moduli of elasticity of the 

 metallic and ceramic parts of the joint will invariably cause additional 

 stresses to be generated in the joint which may cause its premature fail- 

 ure. For this reason, the choice of joint materials is very much limited 

 to high- strength aluminum, titanium, and steel alloys. Ideally, the moduli 

 of the metallic parts and the ceramic shell should be matched, but since 

 this is rarely possible or feasible, the ideal match between the moduli 

 remains but a goal. In reality, a decision always must be made whether 



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