TEST FINDINGS 



Model Capsules 



Short-term tests performed on 1 1 model capsules generated data on 

 which several important findings are based: 



1. The short-term implosion pressure of model capsules of same 

 dimensions, construction, and dimensional tolerances tested at constant 

 ambient temperature is repeatable from one sphere to another with only 

 small deviations from the average (Table 4). For example, four NEMO 

 capsules tested in the 59 to 68°F temperature range failed in the 1,520- 

 to-1 ,645-psi pressure range, indicating less than a ±5% deviation from the 

 group's average of 1,578 psi. 



2. The presence of metal end plates in the acrylic plastic sphere 

 does not significantly alter its short-term implosion pressure, as can be 

 seen by comparing the 1,360-psi implosion pressure of a capsule at 70°F 

 without metal inserts (Model 0) with the 1,578-psi average implosion 

 pressure at 64°F of the NEMO capsules with metal end plates (Table 4). 



3. Ambient temperature has a significant effect on the short-term 

 implosion pressure (Figure 78): the short term implosion pressure was 

 found to be an inverse linear function of the ambient temperature in the 

 32 to 1 14°F range used for testing of models. 



4. A severe temperature differential across the thickness of the hull 

 has no significant effect on the short-term implosion pressure. The implosion 

 pressure of an acrylic plastic sphere under temperature differential test con- 

 ditions appears to be related to the average temperature of the acrylic plastic 

 hull. The acrylic plastic sphere with 104°F interior and 32°F exterior 

 temperatures (average temperature of 68°F) failed at 1,660 psi which 

 corresponds approximately to the implosion pressure of a sphere having 

 interior and exterior temperatures in the 60 to 68°F range (Figure 78). 



5. Ultimate failure in all short-term tests was catastrophic and 

 accompanied by a loud noise. The speed of the implosion was rather slow, 

 the duration of the implosion being on the order of 1 second. The failure 

 mechanism was of a general, rather than a local nature. The fragments were 

 small and the fracture surfaces ran across bond lines indicating that the 

 bonded surfaces were not the planes of weakness along which the failure 

 took place. No cracks were observed on the acrylic plastic bearing surface 

 in contact with the metal end plate. 



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