280 - 12 - 



(b) If conditions are reasonably far removed from the critical region, one can probably 

 reyard the plate as infinite and apply the theory of I. It is proposed to investigate 

 how far away conditions must be for this to be possible. 



(c) It happens that this cavitation criterion is not very different from the criterion for 

 the validity of incompressible theory, though this result could not have been predicted 

 in advance. 



(d) The only type of diaphragm gauge in coomon use that is in this critical region appears 

 to be the 5 inches type. It is likely to be difficult to use this gauge as an 

 absolute instrument, though it should be quite satisfactory for comparison purposes. 

 The design of the smaller types of gauge might well be reconsidered, in order to remove 

 them further from the critical region. 



(e) The assumption of "proportional motion", while probably satisfactory for predicting 

 final deflections, is likely to give misleading results for cavitation times, and for 

 the early motion. It is proposed to look for a better model. 



(f) The pressure-time history of the central point of a plate cannot be taken as typical 

 of the whole plate. 



References. 

 1. Temperley: 



"Theoretical Investigation of Cavitation Phenomena occurring when an 

 Underwater Pressure Pulse is incident on a Yielding Surface - I.' 

 (Referred to as l). 



"The Pressure and Impulse of Subtrarine Explosion waves on Plates." 



"Damage to Ships' Plates by Underwater Explosions." 



Theory of Sound: Volume II: paragraph 302. 



"The Effect of a Pressure Wave on a Plate or Diaphragm." 



O.S.R.D. Report 1115: "The Plastic Deformation of Marine Structures 

 by an Underwater Explosion Wave: II to 15.11.U2. 



Series of O.S.R.D. Interim Reports on Underwater Explosions and 

 Explosives: No. lu onwards. 



Friendlandtr; "The Effect of an Underwater Explosion Pulse on a Framework Composed 

 of Rectangular Panels." 



Appendix 



