Table 1. Flat Disk Window Test Specimens 

 (* represents a test group of five window specimens) 



Nominal 



Thickness 



(m.) 



D| = 1.50 in. 



D; =3.33 in. 



D; = 4.00 in. 



Dq = 2.25 in. 



Do=5.00 in. 



Do = 6.00 in. 



1/8 



* 



* 





1/4 



* 





* 



3/8 



* 



* 





1/2 



* 





* 



5/8 



* 



* 





3/4 



* 







7/8 



* 



* 





1 



* 





* 



1-1/8 





* 





1-1/2 





* 





2 





* 



* 



In order to simulate the loads encountered by flat acrylic windows in 

 underwater structures, window specimens were subjected to hydrostatic pressure 

 loading in a hydrospace simulation chamber. The pressurization of the windows 

 was conducted in a 16-inch naval gun shell converted into a pressure vessel with 

 water at room temperature serving as the pressurization medium. The water was 

 pressurized by two air-driven, positive-displacement pumps whose pumping rate was 

 controlled within ±50 psi/minute. Since previous studies' have shown that critical 

 pressure of windows depends on water temperature as well as on pressurization rate, 

 an effort was made to hold these variables constant for all the window tests. The 

 standard pressurization rate was 650 psi/minute, and water temperature was held 

 between 65°F and 75°F. 



The window test specimens for this study (Table 1) were fabricated by lathe 

 turning Plexiglas grade G sheet stock. The circular disks (Figure 1) thus formed 

 had an overall diameter (D^) of 0.010 inch to 0.020 inch less than the flange's high- 

 pressure opening diameter (Dq), permitting the window to seat in its flange cavity 

 with 0.005 to 0.010 inch radial clearance. The manufacturer's tolerances for varia- 

 tion in the nominal thickness of commercial sheets were accepted for the thickness 

 tolerance of the finished circular flat windows. The finish of the disk edges was 

 held to 32 rms. Dimensions recorded were the average of micrometer measurements 

 taken at three different locations for the window's diameter and for its thickness. 



