TENSION TESTING. 



147 



where f t is the stress producing the extension ; L is the 

 original length of the bar ; and I is the extension corre- 

 sponding to f tt 

 Here 



f* = 0-788 

 L = 10 in. 

 I = 0-000985 in. 



Therefore, 



E = 



10 



0788 x 0-000985 

 = 13,880 tons per sq. in. 



Reduced to pounds per square inch, this value becomes 

 28,860,000. 



0.6 



0.5 



0.3 



0.2 



456 

 FIG. 67. 



8 9 10 



These results, both direct and calculated, are typical 

 for specimens of ductile metals. They must not be taken 

 so much as results, but rather as models of the methods of 

 dealing with such tests. 



88. Distribution of the Extension. On Fig. 67 is a 

 diagram showing the extension of each individual inch of 



