STRUCTURAL DESIGN OF CONICAL ACRYLIC VIEWPORTS 



Technical Report R-686 



YF 38.535.005.01.005 



by 



M. R. Snoey and M. G. Katona 



ABSTRACT 



The purpose of this report is to establish a rational engineering 

 approach for the design of conical acrylic viewports. To achieve this goal, 

 a time-dependent, yield-failure criterion was developed and utilized in the 

 analysis of a variety of viewport configurations. Specifically, a range of 

 thickness/minor diameter (t/d) ratios from 0.25 to 1 .75 and included angles 

 from 60° to 120° were analyzed by the finite element technique. Using the 

 viewport structural analysis in conjunction with the yield-failure criterion 

 for acrylic, time-dependent operating depths were determined as a function 

 of viewport configuration. 



Paralleling the above, an experimental investigation was performed to 

 validate the analytical results. Six full-scale viewports were tested for a year 

 under simulated operational conditions that included simultaneous cycling 

 of pressure and temperature, to 4,000 psi and 70 to 35°F, respectively. 



Comparison of analytical and experimental results indicated excellent 

 agreement for the physical location of viewport failure at specified loading 

 histories. 



Design recommendations are presented in the form of design curves 

 which enable the design of a conical acrylic viewport for a specified operating 

 pressure and duration under load. To complete the recommendations, design 

 information is given also on sealing with a conventional 0-ring, as well as 

 guidelines for elevating a viewport in its flange. 



This document has been approved for public release and sale; its distribution is unlimited. 



Copies available at the Clearinghouse for Federal Scientific & Technical 

 Information (CFSTI), Sills Building, 5285 Port Royal Road, Springfield, Va. 22151 



