558 



The ratio predicted from Equation (l) and Equation (2) in Section III 

 for these conditions was 2.22. For this calculation the following constants 

 were used: 



(thin) 



a^ (medium) 



cTq (thin) 

 o'q (medium) 



0.038 in. 



0.085 in. 

 1*2,600 lbs/in^ 

 50,100 lbs/in^ 



0.368 X 10"3 s 



ec 



(bb) Copper diaphragms . In studying the effect of thickness of 

 diaphragms on damage for copper diaphragms, two thicknesses, .O32 in. 

 and .06k in. were used. All the copper diaphragms were annealed at the 

 same time until dead soft so that the properties other than thickness 

 might be held constant. Eight shots were fired in each of which thin 

 diaphragms were placed in two opposite gauges and thick diaphragms in 

 the other two gauges, all supported by a steel ring. The results are 

 tabulated below: 



Table XIII. Damages of thick and thin copper diaphragms 



a/ Average of two diaphragms 



b/ Based on damages corrected for small variations of distance 

 from 1*8. in. and 81* in. 



It is evident from these data that the ratio of thin to thick damage 

 was not constant. It may be shown that this ratio is a function of damage 

 and that the function is approximately the same for the two distances. 



