~\ — I — I I I 1 1 1 



-[ 1 1 I I I I l | 1 1 1 I I I I I I 1 1 ! I I I 



15-in. OD x 13-in. ID capsules 

 15-in. OD x 14-in. ID capsules 



Notes: 



1. Time was measured from the instant pressurization at a 100-psi/min rate 

 was completed and the hull was under constant sustained pressure 



2. Temperature — 65 to 70°F 



3. Material — grade G Plexiglas 



10 1CT 



Time (hours) 



10 J 



Figure E-2. Comparison of time-dependent implosion pressures for 15-inch-outside- 

 diameter capsules with different wall thicknesses. 



FINDINGS 



When the four capsules with t/D = 0.066 were tested to implosion 

 under long-term hydrostatic loading, it was found that the implosion pressures 

 were, as expected, a function of time (Table E-1 ) similar to the capsules with 

 t/D = 0.033. When the time-versus-implosion-pressure relationship was plotted 

 on the same log-log scale, as was used for the t/D = 0.033 capsules (Figure 87) , 

 it was found that the slope of the linear graph is the same as that for the thin 

 capsule. The only difference in the results for the thick- and thin-walled cap- 

 sules was the magnitude of the sustained pressure for a given duration of 

 loading (Figure E-2). From a comparison of these results, the short-term 

 implosion pressure of the capsules with nominal t/D = 0.066 was extrapolated 

 to occur at 5,000 psi, while the design proof depth (cyclic and long-term) was 

 predicted to be 2,400 feet (certifiable for at least 1,200-foot manned operations 

 when the same stress level and time dependent failure criteria are used as for 

 the t/D = 0.033 capsules). 



197 



