Structural fatigue of the 66-inch hull was evaluated visually by noting 

 the condition of bearing surfaces on the beveled edges of the acrylic plastic 

 hull at the polar penetrations and the condition of the bonded joints between 

 individual spherical pentagons at the conclusion of 107 pressure cycles. The 

 maximum pressure in the individual pressure cycles varied from 100 to 1,070 

 psi and its duration from 1 minute to 24 hours. 



1 . Bonded joints did not have any indications of fatigue damage, 

 although the joints had a large number of potential stress raisers in the form 

 of cavities, separation spaces, and hairline cracks introduced during fabrica- 

 tion. 



2. The bearing surface on the beveled edge of the polar penetrations 

 had no indications of fatigue in the form of crazing, even though during the 

 preceding 107 pressure cycles the hydrostatic pressure loading was in some 

 cycles 2.4 times higher than pressure at the design depth of 1,000 feet (4 

 times higher than pressure at the operational depth of 600 feet). 



note plastic buckling of steel pol 

 urfaces are nt 



/ 



split hatch Staining rings A and A, for bottom plat' 

 are severely twisted, while rings B and B, for the top 

 hatch havy not been damaged 



/ 



Figure 1 18. Steel polar closure components from the imploded 

 66-inch-diameter capsule. 



151 



