FINDINGS 
The window evaluation study has conclusively shown that (1) the 
performance of windows is predictable, and that (2) the window system 
chosen is more than adequate for the 450 psi 120°F operational service 
in EDU chambers. 
Both the large (t/D; = 0.330) and the small (t/D; = 0.346) windows 
chosen for the EDU chambers imploded (Table 3) under short-term hydro- 
static loading at room temperature (70-75°F) in approximately the same 
pressure range (6900-7200 psi) as Plexiglas G windows tested in previous 
study (7000-8500 psi). This proved that Swedlow 350 acrylic plastic 
windows performed as well as Plexiglas G acrylic plastic on which the 
NCEL specifications for acrylic plastic windows were based. 
The mode of failure for the windows tested at 120°F ambient pressure 
was found to be the same (Figures 5 and 6) as that for windows tested at 
70°F ambient pressure (see NCEL Technical Report R-527 Appendix B). 
First there formed a star shaped system of cracks propagating radially 
outward from the center of the window's low pressure face. The cracks 
were the deepest in the center of the window face. The depth of these 
cracks even at the center of the window face was less than the thickness 
of the window. Second, the leading edges of the cracks inside the body 
of the window curved towards the horizontal plane of the window coalescing 
in a single conical fracture plane. The apex of the cone was centered just 
below the center of the window's high pressure face. Third, a small hole 
was punched through the center of the window relieving the hydrostatic 
pressure inside the vessel. 
Comparisons between the 7200 psi implosion pressure of small EDU 
windows at 76°F and 7000 psi implosion pressure at 120°F has shown that 
the effect of 120°F temperature on the short-term strength of EDU windows 
is insignificant. It was found, however, that the temperature appears to 
have some effect on crack initiation (Figure 7a). There appears to be 
some difference between the failure pressure of large and small EDU windows 
as could be predicted from the small difference in their t/D. ratios. 
The EDU windows can withstand with confidence a momentary pressure loading 
of approximately 3600 psi without initiation of major cracks giving the 
windows a proven safety factor of about 8 under short-term overload (less 
than 1 minute duration). The displacements of the large EDU windows were 
larger than those of the small windows, but almost in direct proportion 
to the ratio of their t/D; diameters (Figure 7b). 
Long-Term Loading 
The catastrophic failure of EDU windows has been found to be very 
predictable (Table 4). The relationship between implosion pressure and 
duration of a single sustained loading was found to be graphically 
expressable as a straight line on log-log coordinates (Figure 8) and thus 
easily to extrapolate into the future. The windows were found capable of 
withstanding a long-term pressure loading of at least 2250 psi without 
