10 Wilson, Stress and Strain in Copper Bars. 



homogeneous, have the effect of lowering the yield-stress 

 and increasing the value of n, though how far the 

 lowering of the elastic limit would continue with further 

 strainings the author has not determined. 



In this respect, however, the copper wires exhibit a 

 marked difference from the iron and steel bars tested by 

 Professor Unwin, who found that neither the elastic limit 

 nor the second part of the load-strain curve was altered 

 by repeated straining and annealing. 



The tests of bars and wires described above were 

 made on the testing machine and apparatus in the 

 Whitworth Engineering Laboratory, The Owens College. 



APPENDIX. 



Test No. I. 



ANNEALED COPPER SPECIMEN. 



Initial length 6", Initial diameter •625", Area '3068 sq. in. 

 Value of n = "535. 



Load, F 

 tons. 



Strain 

 a 



'-1 



Stress 

 (tons per sq. in. ) 



Value of C 

 (Calculated). 



2*o 



•04 



678 



37'94 



2-5 



•0625 



8-658 



38-16 



3'o 



•0917 



10-675 



38-33 



3-5 



•1342 



12-939 



37-89 



Me 



>an value of C 



--^ 38-08 



