pressure in an isolated pressure vessel in a 24-hour period during the first 

 pressure cycle was found to be equal to the pressure drop recorded in the 

 same vessel during some later cycle, the decrease in volume of the capsule 

 model was the same in both cases. For example., the pressure drop in 24 

 hours during the first pressure cycle on Model 8 was from 520 psi to 453 psi. 

 Subsequently, the pressure drop was measured again during the 234th cycle 

 and was also found to be from 520 to 453 psi. 























'~~~~~ 









































1. Test specimen NEMO capsule 



2. Location on capsule — pentagc 

 — 3. Pentagon dimensions — 0.472- 



thickness; 7.51 3-in. outside ra 



4. Material — grade G Plexiglas 



_ 5. Temperature — 69 to 71.3 F 



6. Loading cycle — pressurized to 



500 psi at 100-psi/min rate; he 



for 1 66 hr at 500 psi; depressu 



2 



n 6 













dius 













Id 

 rized 













at 100-psi/min rate to psi; hi 

 psi for 166hr 



Id at 



























2 4 6 8 10 12 14 16 18 20 



3 

 Time (minutes x 10 ) 



Figure 98. Typical viscoelastic strain on the interior of a 15-inch-diameter 

 capsule in the equatorial region during a typical pressure cycle 

 to 500 psi with subsequent relaxation period. 



An axial compression test conducted on a single model capsule to 

 simulate tie rod loadings produced only exploratory data. Since the electric 

 resistance strain gages, located both on the exterior and interior of the hull, 

 covered only a small area of the surface, a complete picture of the stress field 

 in the acrylic plastic hull under axial compression was not obtained. The load 

 was applied to the hull by internal tie rods attached to the circumference of 

 the steel end plates. On the basis of this data (Figures 99 and 100), it has 

 been found that: 



1 . The stresses generated by axial tie-rod pretension of 100 pounds 

 are higher at the steel polar plate than at the equator. The meridional stresses 

 at the penetration show compression on the exterior and tension on the interior. 



133 



