brought out in a qualitative way in Figure 22 where the static strength- 

 weight ratios for unstiffened, ring- stiffened, and sandwich-type cylindrical 

 pressure hulls are compared. If this turns out to be the case, and there is 

 some indication to this effect, then the advantages offered by any of the 

 newer multilayered, sandwich, and sheathed constructions will be mainly 

 ease of fabrication and some possibility of improved dynamic and 

 explosion resistance; these latter considerations have not been discussed 

 in the earlier sections on strength analysis, and will not be pursued here 

 either. Therefore, we can state that the main advantages of these new 

 pressure-hull constructions stem from the use of thinner plating materials 

 with their inherently superior ductility, higher yield strength, greater 

 notch toughness, uniformity of physical and mechanical properties, and 



greater ease of fabrication. 



69 

 Krenzke at the Model Basin has conceived the idea of applying the 



bimetallic, and in general, the sheathed construction idea to cylindrical 

 pressure hulls. A major advantage of this technique is that it permits the 

 use of available materials such as the very high strength titanium and alu- 

 minum alloys by eliminating the handicaps of nonweldability and the 

 propensity to corrosion. The basic idea is that forged and/or machined 

 ring segments, not physically joined together, are placed inside a thin, 

 weldable outer jacket made of some compatible material so that upon 

 initial application of pressure, the thin outer jacket is stressed beyond its 

 yield point and thus plastically deforms around the more rigid high-strength 



125 



