4o8 A. A. MICEELSON 



This displacement is represented by the formula 



S 2 =A 2 (i— e~ a Vt), 

 where 



A 2 = C 2 Pe h > p . 



1 c) The viscous displacement. — Here the elastic force is absent 

 or very small in comparison with the viscous resistance. The 

 specimen does not return to zero even after a long time interval. 1 

 The viscous displacement is given by 



s 3 =(Ft+F t y-(F t y, 



in which F^O^Pe 1 '', and F = the corresponding value, when P 

 has the value P during the time t . 



For a specimen which has not been subjected to previous 

 strain the formula reduces to 



S,= {Fty. 



Experiment gives p = \ approximately, until the specimen is near 

 the rupture point, when p approaches the value unity. 



d) The lost motion. — If the stress be applied for a short time 

 (even a small fraction of a second), the specimen does not return 

 to the original zero. The difference between the original and the 

 new zero is the lost motion L. , 



It seems probable that the lost motion may be considered as 

 a function of t such as f, where r is very small (less than 0.02 for 

 zinc) . 



If this be considered as part of the viscous term 



S,=A 3 f(t), 

 then the total viscous yield may be represented by 



S>=AJtf(t)+cr] 

 (if the actual stress is between the limits o and P , c = o). 



1 In some cases it may be made to return to the original position by heating or 

 by alternation (alternate positive and negative diminishing stresses). 



