91 



Area at point of fracture — 



Per cent, of original area 



Elongation in S inches, per cent. 



(U.6 



27.:; 



Finally one end of the test specimen was exposed to the action of acids, and 

 the etching thus produced used in printing Fig. 5. This figure, therefore, shows 

 the disposition and relative density of the various layers of iron composing the 

 specimen. The symmetrical arrangement of curved lines, which is so noticeable, 

 is due evidently to the hammering of the round section of the axle to a square 

 section in the process of forging the end of the axle down to the size of the test 

 specimen. 



While the tests show the iron of the axle to have been of excellent cjuality, 

 the most significant fact developed is that concerning the amount of distortion 

 which such an axle will \vithstand without taking a permanent set. 



It would at first sight appear impossible that by loads applied at the journals 

 a common car axle could be deflected at its center as much as a third of an inch 

 without exceeding its elastic limit, but an analysis of the data given will fully 

 justify such a conclusion. The results show al:;o that a deflection of the axle 

 well within the elastic limit of the material may be sufficient to produce a tem- 

 porary change of gauge in the wheels mounted upon it of (juite three-tenths (0.3) 

 of an inch. 



Fig. 1. Test-i of ;i Wrought Iron ('sir .\xle. 



