SHOCK WAVE MEASUREMENTS 2^ 



explosives. These results are very similar in general form to the re- 

 sults obtained for pentolite, as discussed and illustrated in section 7.3. 

 Experimental values have been obtained for the following conditions, 

 among others: 



(1). Spherical TNT charges, pressures from 500 Ib./in.^ to 20,000 

 lb./in.2 for charge weights of 48 and 76 pounds, density 1.52 gm./cm.^ 



(2). Cylindrical loose tetryl charges, pressures from 4,000 Ib./in.^ to 

 17,000 lb./in.2 for charge weights of 4 and 5 pounds, density 0.93 gm./ 

 cm.^ 



For many years, TNT has been the standard high explosive, more 

 widely used than any other, although other materials are superior to it 

 in effectiveness or for fundamental investigations. Because of its wide- 

 spread use as a standard of reference, similarity curves for TNT are 

 plotted in Figs. 7.8-7.11. These curves are seen to be qualitatively 

 very similar to those for pentolite in section 7.3, and provide a means of 

 estimating shock wave parameters over a rather wide range of charge 

 weight and distance. It should be remembered that these curves apply 

 strictly only to spherical charges of density 1.52 gm./cm.^, and de- 

 partures from spherical shape or differences in loading density will re- 

 sult in changes of the parameters. 



It is generally characteristic of shock wave results for high explosives 

 that peak pressure P^ and the reduced energy flux Ef/W^'^ are ac- 

 curately represented over the range of measurement by power laws of 

 the form: constant X {W^'^/RY, where a is a constant. The reduced 

 impulse I/W^'^ and time constant B/W^'^ are less accurately fitted by 

 such a power law, but the agreement is fair for these over a range of 10 

 to 1 or more in W^'^/R, except very close to the charge (distances less 

 than 10 charge radii). The power law thus gives a compact, reason- 

 ably precise method of representing the data, and is also a reasonably 

 good representation of results from the theory of Kirkwood and Bethe 

 (see section 4.2). Accordingly, it is convenient to write the peak pres- 

 sure, impulse, and energy flux in English units as 



/Wl/3\a 



(7.6) ^"'K^) 



/Wl/3\/3 



In quoting values of the constants, charge weights are taken in pounds, 

 and distance R from the charge in feet. 



Experimental values of the constants (/c, I, m) and exponents 



