Post-Test Observations. Failure results on the six viewports are 

 contained in Table 2. From Table 2, it is shown that as the t/d ratio 

 decreased, the frequency of stress crazing and cracks increased. Figures 4, 5, 

 and 6 provide a visual supplement to Table 2. The least conservative design 

 or the lowest t/d ratio (0.45) is shown in Figure 4. The resulting cracks and 

 deformation at the low-pressure face corner are clearly shown. There was 

 no visible damage anywhere else on the viewport. Collection of condensate 

 around the low-pressure face resulted in an accumulation of rust on the 

 flange which caused the ragged surface on the rounded corner of the view- 

 port. 



Table 2. Results of Test on Full-Scale Viewports 



t/d Ratio 



Maximum Width 



of Crack Pattern 



(in.) 



Creep Displacement ,„^ 

 -r . 1 ^-^■ , X 100 

 1 otal Displacement 



(%) 











0.92 







14 





1/16 





0.61 







20 





3/32 





0.45 



1/16 



26 



11 



