are presently underway at the Model Basin to obtain some verification of 

 Equation (177). 



The method for determining the secant and tangent modulii E and E., 

 respectively, from the uniaxial stress-strain curve of a given material 

 comprising the shell structure and for a given state of stress defined by 

 c5- (see Equation (107)) has already been outlined in connection with the 

 axisymmetric and asymmetric panel-instability modes. The same tech- 

 niques are also used here, and the procedure for finding the buckling 

 pressure in the plastic range follows the method shown on Figure 14. 



SOME REMARKS ON NEW PRESSURE HULL 

 STRUCTURES FOR DEEP DEPTH 



In the preceding sections, consideration was given to the more im- 

 portant physical concepts and mathematical analyses, and the equations 

 and formulas resulting therefrom, which today form the basis for rational 

 design of cylindrical pressure hull structures. The question as to how 

 these formulations can be used collectively in an optimum design pro- 

 cedure is left to the discretion of the reader. However, it goes without 

 saying that the most obvious approach would be to program the various 

 equations and formulas for high-speed digital computation. It is then 

 possible that for specified mechanical properties of a hull material, the 

 pressure and stresses associated with each of the primary modes of 

 failure can be determined for a broad range of the geometric parameters 

 of interest. It then remains to optimize, by some semigraphical technique 

 for instance, the best possible configurations for a given weight-displace- 



115 



