﻿Plastic Bending of Metals. 



189 



form as that obtained by P. Phillips *, connecting the ex- 

 tension with the time a metal wire is subject to a constant 

 pull, and by C. E. Larard f , connecting the torque and time 

 when a metal is twisted to destruction at contant angular 

 velocity. 



In the light of their experiments, we may assume that the 

 particular length of the specimen over which equation (A) is 

 true coincides roughly with that in which plastic deforma- 

 tion is taking place, the remaining portion of the rod not 

 being stressed beyond its elastic limit and acting merely as 

 a load. 



Fig. 5 shows that n is a parabolic function of the time 



Fio\ 5. 



■sc 



•78 



-75 







o 



oV 













o 



log. n & Log. t 





^ 



X 



s 











Nl 



i 



.Log.t 









after an initial stage — taking about 15 minutes in present 

 case — is passed. 



For all the specimens on which the writer has experimented 

 the value of n is in the neighbourhood of one half. This is 

 rather suggestive of the well known Parabolic Catenary, 

 in which the load on any element is proportional to the 



* P. Phillips, " On the Slow Stretch in Rubber. Glass, and Mfetala 

 when subject to a Constant Pull," Phil. Mag*, ix. (1905). 



t C. E. Larard, " On the Law of Plastic Flow," Proc. Plivs. Soc. 

 1913. 



