74 



60 



example, the wave from 1 pound of TNT at 7.5 feet, corresponding to that from 

 300 pounds at 50 feet, should have a peak pressure of about 2100 pounds per 

 square inch, but it produces only the same deflection as a static pressure of 

 1650 pounds. The occurrence of dynamical overshoot should make the wave 

 equivalent perhaps to 2100 x 1.22 = 256O pounds. An increase of 55 per cent 

 in the yield stress of the copper diaphragm above the static value, due to 

 high strain rate, would remove the discrepancy, but such an increase seems 

 excessive. 



Other features of the data cannot be interpreted with certainty. 



21 -INCH DIAPHRAGMS 



Data pertaining to tests on 21 -inch steel diaphragms have recently 

 been reported by Lt, Comdr. R.W. Goranson, USNR, for the Bureau of Ships (22). 

 The diaphragms were securely fastened to the equivalent of a heavy steel ring 

 1 foot wide mounted on the front of a heavy caisson and were attacked by 

 charges of 1 pound of TNT. Perhaps the ring can be regarded as roughly 

 equivalent to an infinite baffle. 



In Table 2 there are shown, for seven shots, the kind of steel, the 

 thickness h, the distance R of the charge, the average dynamic yield stress a 

 as estimated in the original report, the observed final set deflections z, 

 and several computed values of 2. 



TABLE 2 



21 -Inch Steel Diaphragms of Special Treatment Steel, High Tensile Steel, 



Medium Steel and Furniture Steel 



