MEASUREMENT OF PRESSURES 



157 



constitutes an impulse or momentum gauge which gives a measure of 

 the area under the pressure-time curve. 



5.3. Diaphragm Gauges 



Several types of gauges have been developed in which the plastic 

 deformation of an air-backed plate or diaphragm is taken as a measure 

 of explosive effectiveness. One such gauge, developed by the Italian 

 Modugno about 1919,^ consists of a 3^ inch copper disk with an exposed 

 surface 1 inch in diameter mounted on the lip of a cuplike gauge body, 



.080' 



puxte\ 



FRONT SIDE 



Fig. 5.5 Construction of UERL diaphragm gauge. 



and fastened down by a screw cap which crimps the edge of the disk to 

 constrain it. This device functions somewhat as does a ball crusher 

 gauge, and the final deformation gives a measure of peak pressure from 

 reasonably large charges. Any very realistic description of its oper- 

 ation is a sufficiently complicated function of the pressure and laws of 

 plastic deformation that its utility, either as a tool of measurement or 

 for investigation of mechanisms of damage, is somewhat limited. 



Another type of diaphragm gauge is the British "pot" gauge and a 

 modified form of this gauge used for explosive comparisons in this coun- 

 try. This latter gauge, developed at the Explosives Research Lab- 

 oratory at Bruceton and the Underwater Explosives Research Labora- 



^ For a detailed description of this gauge, Reference (14) should be consulted (the 

 original report by Dr. Francesco Modugno of the Royal ItaUan Navy is not acces- 

 sible) . 



