Ul 459 



The radial displacement-time curves of the particles in the dia- 

 phragm have not yet been studied This experimental Investigation will be 

 made as soon as the requisite apparatus becomes available. It should furnish 

 Information about the thinning of the diaphragm during the deformation and 

 therefore about the all-Important question of rupture by underwater attack. 

 Incidental to this study, considerable light may be shed on the Interesting 

 Jerking motion of the material in the center of the diaphragm. 



CONCLUSIONS 



The observations described in this report bear out in detail the 

 hypothesis put forth in Reference (10) that the C-phase pressures are effec- 

 tive in producing damage when the charge distance is less than a certain 

 critical one. Moreover, quantitative evidence supports the contentions of 

 (10) that (a) the pressures between the closing up of cavitation and the 

 second blow do little damage, and (b) the Initial Impulsive velocities of 

 parts of the diaphragm are proportional to the Inverse first power of their 

 distances from the charge. That Is, the Initial kinetic energy of the dia- 

 phragm at the larger charge distances Is roughly proportional to the solid 

 angle subtended by the diaphragm at the charge. 



hEFERENCES: 



(lOJ "Early and Ultinate Damage due to Underwater Explosions 

 against 10-inch Diaphragms," by G. E. Hudson, Ph.D., TIvIB Report 

 509, August 1943. 



(11) "Effects of Underwater Explosions, General Considerations," 

 by Professor E.H. Kennard, TilB Report 489, September 1942. 



(12) "Progress Report on Underwater Explosion Research - Bureau of 

 Ships Symbol E139 - Part 2 - The Pressure-Time Curve for Underwater 

 Explosions of Very Small Charges of Tetryl," by tvI.M. Shapiro and E.T. 

 Habib, TMB Report R-202, February 1944. 



