Effect of Loading Conditions 



Preliminary results from other studies in progress indicate that the critical 

 pressures and deflections of acrylic windows are adversely affected by higher 

 temperatures, and sustained or cyclical pressure loading. The designer is therefore 

 cautioned that the data presented in this report pertains only to short-term pressure 

 loading as defined for this study. If the short-term critical pressure data is used as 

 a design basis for windows subjected to long term or cyclical loading, a safety factor 

 of at least four, based on the short-term critical pressure, is recommended for the 

 preliminary selection of window thickness. Subsequently a full-scale window with 

 dimensions selected on the basis previously described should be tested under the full 

 loading expectancy of the design. When experimental data for long-term and 

 cyclical pressure loading become available the presently recommended approximate 

 safety factor will be replaced by precise critical -pressure design curves plotted as 

 a function of loading duration or number of pressure cycles. 



Effect of Variations in Flange Design 



Effects of flange designs different from DOL type III have not yet been 

 investigated. Variations of direct influence on deflection and critical pressure 

 would be (1) the use of a retaining ring against the high-pressure face, (2) the use 

 of gaskets with or without a retaining ring, (3) using a radial clearance less than 

 0.005 inch between the window and flange, and (4) using a different flange shoulder 

 thickness at D;. 



It is postulated that use of a retaining ring incorporated in a flange design 

 would increase the critical pressure capabilities and decrease deflections of windows 

 whose t/D] ratio Is less than about 0.4 to 0.5. This size window, failing predominantly 

 by flexure would be more drastically influenced than would be the windows of t/D; 

 ratios greater than about 0.5, which fail predominantly by shear. 



Flat bearing gaskets employed in a flange design are postulated to have varying 

 effects, depending on the gasket's thickness and hardness and whether a retaining 

 ring is also employed. Again the smaller t/D| ratio windows would probably be more 

 affected than would be the larger t/D| ratio windows. 



The magnitude of the flange thickness should not affect the window's short-term 

 critical pressure so long as It is sufficiently thick to restrain radially the extruding 

 portion of the window's low-pressure face prior to its failure. Also, the flange 

 shoulder must be sufficiently thick to be rigid In comparison to the flexural rigidity 

 of the flat acrylic window supported by the shoulder. 



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