STRESS AND PERMANENT STRAIN. 



31 9 



Taking the logarithms of both sides of the above 

 equation, the standard equation is obtained, having the 

 form 



/= C e k 



For the nine bars tested, the slope of the curve gave 

 the value of k as 0'25, and the mean value of C as 39'4. 



Further tests, both on sets of bars as above and on 

 single bars, gave the following results : 



Set of 9 bars of brand K.H., Crown B.B.B. 0'25 



Single bar 



Single bar ,, ,, 



Set of 9 bars brand E.H., Crown B.B. 



Single bar 



Single bar ,, ,, 



Single specimen cut from a bar of mild 

 steel .. 



0-25 .. 

 0-25 .. 

 0-265., 

 0-275.. 

 0-265., 



39-40 



40-30 



40-35 



39-30 



40-416 



39-252 



0-25 ... 50-160 



The actual figures obtained for the first set of bars 

 are the following : 



Proceeding on similar lines, Dr. G. Wilson,t has 

 made corresponding determinations for annealed copper 

 bars in tension. The values of the constants obtained 

 in the equation 



f=Ce* 

 are as follow : 



t Mem. and Proc. Manchester Lit. and Phil. Soc., 1898-9. 



