196 



FLAT CENTRAL REGION 



BENDING WAVE 



RIGID MATERIA L 



RGID RESTRAINING RING 



FIGURE 2 



Cut-away Sketch of the Diaphragm at Some Instant After the 

 Motion Has Begiin, 



The flat central plastic flow region ahead of the 

 bending wave, the wave itself, and the deformed region 

 behind the bending wave, in which the material is supposed 

 to be rigid and at rest, are clearly shown. 



