403 



to solve this hydro dynainical problem in conjunction vdth the results 

 of the present section. Hence the accuracy of the structural part 

 of the final results in the next section is somewhat masked by the 

 uncertainties in the hydro dynamical part, perhaps thereby causing the 

 results of the present section to seem overly elaborate. However, it 

 is hoped that the results of the present section may be more fully 

 utilized when a more successful attack is made upon the associated 

 hydrodynamical problem. 

 U . Application to damage by underwater explosions 



In this section the foregoing theory is applied to the case 

 of an infinite thin plate loaded by an underwater explosion wave. It 

 is assumed that the plate is backed by air, and, further, that the 

 underwater pressure wave impinging upon the front surface is of suffi- 

 ciently short duration to cause well-developed cavitation within a 

 relatively short period of time, that is, short compared with the time 

 of deformation. Under these assiimptions the plate may be treated ap- 

 proximately as moving freely with an initial velocity distribution 

 related to the properties of the explosive. 



The problem of determining the loading from the properties 

 of the explosion wave — that is, determining the actual pressure acting 

 on the plate from the free field pressure in the incident wave — has not 

 been solved. The problem is complicc^.ted by cavitation and in some cases 

 by nonacoustical effects due to finite aimplitude. In the absence of any 

 solution, the procedure will be based on certsdn ad hoc semi-empirical 

 assumptions. It is assumed that the, energy delivered to a plate element 



84 



