248 \VOUK DUNK ON BARS. 



This is very near the result obtained from the diagram, 

 which was T'.'tt) inch-tons. 



Both this, and the result obtained from the diagram 

 above, give the total work done upon the bar up to the 

 point of 1 fracture as represented by the area A H G F E D. 

 The objection to the use of this method is that it includes 

 the work done beyond the maximum load at F, and, in 

 consequence, is not independent of the proportions of the 

 bar. It would, therefore, seem to be better, and to make 

 it possible to use these figures for comparing bars of 

 various dimensions and ratios of length to diameter, not 

 to include the work I H G F, but simply to measure the area 

 A I F E D. The above formula does not apply to this 

 case, as it depends upon the extension after fracture, ard 

 not on the extension at the maximum load. 



In order to find the work done per cubic inch without 

 taking account of the local extension, when this exists, 

 some means must be adopted by which the local extension 

 may be eliminated. 



The extension on the several inches of length were as 

 follow : 



EXTENSIONS ON EACH INCH. 



1st 019 inch. 



2nd 0-20 



3rd 0-21 



4th 0-24 



5th 0-28 



6th 0-29 



7th 0-30 



8th 0'60 



9th 0-50 



10th 0-25 



Total, neglecting 8 and 9 = T98 



This total of T98 inches is on the 8 inches which do not 

 partake of the local contraction. 



Using Kennedy's formula again, we have : 

 P e (r + 2\ 

 \ 3 J 



w = 



21-9 x V98 



/0-594 + 2\ 

 V 3 ) 



8 x 0788 



= 5 -96 inch-tons per cubic inch, neglecting 

 local extension. 



