568 



The time scale was calibrated against a 25 kc/sec crystal controlled 

 oscillator, and checked by time intervals on the record known in terms of 

 the shock wave velocity. Lot 3 steel diaphragms, .075 "to .080 in. thick, 

 were used as before. 



The data obtained are given in Table XVI euid plotted in Figure 21. 



Table XVT - Time of central deflection for Lot 3 steel diaphragms . 

 250 gm. loose Tetryl at 30 in.; contact method 



The general shape of the curve is qualitatively what one would expect. 

 The time for maximum depression cannot be fixed with great accuracy from 

 such a curve but is about 155 microseconds. Possibly a less ambiguous 

 figure is the time of 82 microseconds for half the final deformation. 

 These figures are comparable with the duration of the incident shock wave 

 (time constant 5I+ microseconds) and show that for the experimental condi- 

 tions in this case the influence of the secondary and later impulses is 

 negligible. - 



