1,000 



1 — I I II 1 1 



Notes: 



1. T versus N relationship is based on appearance 

 of fatigue cracks in 4 NEMO models pressure- 

 cycled to 1,000-1,200-foot depth range 

 Implosion occurs at a number of dives at least 

 twice as large as shown 



No fatigue cracks are expected in capsules for 

 the TN relationship shown at 600-foot opera- 

 tional depth 



100 1,000 



Number of Dives, N 



10,000 



Figure 121. Crack-free fatigue life of 66-inch-OD NEMO capsule at 600-foot depth. 



3. The fatigue life depends not only on the number of dives, but also on 

 their maximum depth and duration. When the fatigue value of individual 

 dive is calculated after each dive, both the duration and the maximum depth 

 reached must be noted. The fatigue value of a dive to a lesser depth than 

 600 feet is calculated on the conservative linear basis (e.g., a dive to 300 feet 

 of 1-hour duration is considered as 1/2 of a dive to 600 feet of Thour dura- 

 tion). When the fatigue values for dives of different durations and depths 

 are added up, the procedure is to consider each dive as a fraction of the 

 available fatigue life at 600 feet and specified dive duration. Thus, the 

 fatigue values of a 1-hour dive to 300 feet, a 6-hour dive to 400 feet, and 

 a 100-hour dive to 600 feet are added up as: 



157 



