D,13 • DESIGN CRITERION FOR MINIMUM WEIGHT 



For any desired duration time td, however, it is possible to select an infi- 

 nite set of thicknesses {di, d^) large enough to assure that the inequahty 

 in Eq. 13-2 holds up to t^. In the set {di, d^) there is, in general, a particu- 

 lar pair of dimensions which makes the weight w a minimum. The prob- 



0.0500 



g 0.0450 



a 



'cu 

 _o 



to 

 O 



£ 



o 



U 



0.0400 



0.0350 



0.10 



Metal thickness 62, in. 



Fig. D,13. Weight per unit area of composite slabs (zirconia-metal) 

 vs. metal thickness [19]. (Cf. Art. 13.) 



lem of optimum design is to determine, for specified materials and heating 

 parameters, the pair of dimensions (di, ^2) which minimize w and lead to 

 equality in Eq. 13-2 at the time U. 



Fig. D,13 shows curves of w vs. di for combinations of zirconia shield- 

 ing aluminum and molybdenum envelopes with the following data: 



< 279 ) 



