but how high the dynamic stresses in the vessel actually are is only a calculated 

 guess. The fact that those dynamic stresses also fatigue the vessel material 

 only further complicates the matter. This fatigue effect, when added to the 

 fatigue caused by static pressure cycling, makes it necessary to reduce consid- 

 erably the safe stress level that can be tolerated by the vessel material during 

 a projected 20-year lifetime. 



Conclusion 



A safety factor of 2 based on yield of the material is considered 

 inadequate. A safety factor of at least 3, and preferably 4, should be used. 

 The safety factor should be based on yield of the vessel's material under static 

 pressure loading to insure not only a statically safe vessel but also a long cyclic 

 life at pressures equal to static pressure. 



Recommendation 



A minimum safety factor of 3, and preferably 4, based on the yield 

 strength of the material, should be applied in the design of the proposed pres- 

 sure vessel. 



OVERALL CONCLUSIONS AND RECOMMENDATIONS 

 Conclusions 



1. The group concurs that at the present time the stacked-ring or multilayer 

 construction concepts are the most feasible concepts for the construction of 

 a 10-foot-diameter deep-ocean simulation vessel with a 10,000-psi operating 

 pressure. Of the two, the stacked-ring concept possesses the added advantages 

 of in-situ assembly, interchangeability and replaceability of individual con- 

 struction modules, and absence of welds. 



2. The most promising closure system for the stacked-ring concept from the 

 viewpoint of accessibility to penetrations, speed of operation, ease of manu- 

 facture, and cost, appears to be composed of tie rods and hemispherical end 

 closures. Although it is a promising system, very little design experience is 

 available for its design. 



3. The projected types of tests that will take place in the vessel and the impact 

 on the national deep-submergence effort that the loss of such a vessel would 

 create, make a safety factor of 2 inadequate. A minimum safety factor of 3, 

 or preferably 4, based on yield of material, should be utilized. 



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