2,000 





^•. 













• ^ 



*v 



^^ • 















Notes: 



1. Pressurization rate— 100 psi/min 



2. Dimensions of the spheres — 15-in. OD x 



3. Material — grade G Plexiglas 



I I 



14-in. ID 



40 



100 



60 80 



Ambient Temperature (°F) 

 Figure 78. Implosion pressure of acrylic plastic capsule models as a function 

 of ambient water temperature under short-term loading. 



6. The magnitude of the volume decrease that the acrylic plastic 

 spheres undergo with increase in short-term external hydrostatic pressure 

 varies with ambient temperatures (Figure 79). The relationship between 

 pressure and volume decrease is linear to pressures beyond 1,000 psi, except 

 that (1) the volume decrease rate varies directly with temperature and (2) the 

 linear-pressure-versus-volume-decrease relationship becomes nonlinear at 

 lower pressure for high ambient temperature. Although the acrylic plastic 

 spheres fail at different pressures, depending on the ambient temperature, 

 the total decrease in volume at the moment of implosion is about the same 

 for all of them: approximately 5% of the original sphere's displacement in 

 water (equivalent to approximately 16,900 to 17,100 juin./in. average strain 

 in the acrylic plastic). 



7. Failure of the simple steel end plates of type 316 stainless steel 

 used in some of the NEMO models takes place at approximately 1,800 psi 

 (Figure 80). The failure takes place in the form of plastic buckling. 



118 



