were acceptable. In addition to proof-testing capsules 1, 2, and 3, capsule 3 

 was subjected to extensive cyclic tests to establish the ability of SS-6217 

 adhesive to withstand without failure cyclic stresses and long-term immersion 

 under compressive loading. Detailed inspection of the bonded joints failed to 

 detect any incipient cracks after 815 cycles of 1 hour duration at 1,200-foot, 

 178 cycles at 1,500-foot, and 1 17 cycles at 2,000- foot depths. Fatigue cracks 

 were observed in the acrylic bearing surfaces in contact with steel polar clo- 

 sures only after completion of cycling tests to 1,500-foot depth. The cyclic 

 tests on NEMO capsule 3 concluded the series of quality control tests. 



CONCLUSIONS 



The successful production run of three 66-inch acrylic plastic capsules 

 by a contractor according to NCEL specifications has shown that almost all 

 of the fabrication processes developed under laboratory conditions were 

 directly applicable with no, or only minor modifications for mass production 

 requirements typical to industry. The only improvement was in bonding. 

 Substitution of a different adhesive and joint spacer system permitted simul- 

 taneous bonding of six pentagons into a hemisphere rather than bonding of 

 only a single edge at a time between adjoining pentagons. 



The ability of the plastics fabricator and the material supplier to 

 produce by industrial fabrication techniques a series of capsules with the 

 same, or better structural properties than those found in capsule 0, indicates 

 that both the material properties and dimensional tolerances achieved in the 

 prototype capsule are within the range of industrial capability. Thus, it 

 appears that there will be no problems encountered by the industry in pro- 

 ducing as many NEMO 66-inch acrylic plastic capsules in the future as may 

 be required by the national undersea program. 



The ability of mass-produced capsule 3 to withstand the extensive 

 cyclic pressure testing at 100% overload without generation of fatigue cracks 

 confirms again ( 1 ) the validity of cyclic test data generated previously by 

 testing of models and NEMO capsule 0, (2) the presence of 100% overload 

 safety margin for recommended fatigue life (Figure 121) in manned operations 

 to 600-foot depth, and (3) the ability of NEMO capsules to withstand safely 

 brief manned proof-test dives to 1,200 feet. 



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