761 
sree ss 
there was a decrease in the percentage of that energy manifested in the re- 
bound. About 3-1/2 percent of the input energy was manifested as rebound 
energy at the 1 ft-lb level, whereas at 3) ft-lb the rebound cnergy was but 
1 percent. Cylinders gave about 10 percent greater rebound energy than 
spheres. Nevertheless, a correction for rcbound was omitted from the energy 
versus deformation curves because the calibrating machine operates in a 
manner comparable to the gauges in which the copper crushers are used (momen- 
tum, Hilliar and ball-crusher gauges) and comparable rcbounds probably occur 
in the gauges. 
As in the carlier calibration studies, no definite specd effect was 
noted over the range of strain rates uscd. 
The barreling effect (barreled rather than cylindrical shape of deformed 
cylinders which rough surfaces of anvil and piston will produce by constrain- 
ing the motion of the cylinder faces) noted by Winslow and Bessey (High- 
Spced Compression Testing of Copper Crusher Cylinders and Spheres, II, Final 
Report, NDRC Report A-32), (OSRD-5039), pe 18) was notcd in the present tcsts. 
It was most pronounced with large deformations of 0.1 in. or more. An ex-— 
amination of cylinders deformed by momentum and Hilliar gauges showed the 
same phenomenon, This indicates the need for maintaining smoothly finished 
surfaces on the anvils and pistons of all crusher=—type gauges. 
