236 



STRENGTH OF MATERIALS 



ductile materials, the fracture extends down one side for some dis- 

 tance. The material fails by the outer fiber failing first in tension. 

 A similar fracture can be seen by twisting a stick of chalk or other 

 brittle material with the fingers until fracture occurs. 



187. Cast-iron columns. Some tests have been made upon full-sized 

 cast-iron columns both at the Watertown Arsenal and by the Phoenix 

 Iron Company of Phoenixville, Pennsylvania. The results of the>e 

 tests show that the total strength of these columns is much less 

 than the compressive strength of the metal would lead <>ne t<> expert. 

 Tin's was probably due to the presence of blowholes or other imper- 

 fections in the column, such as are likely to occur when lar^c j 

 are cast. The ultimate strength of the Watertown columns varied 

 from 21,0001b./in. 2 to 40,000 lb./in. 2 . 



The following table gives the result of a compn'ssinn test of a cast- 

 iron column made by the Watertown Arsenal, the ultimate strength 

 in this case being 33,340 lb./in.*. 



COMPRESSION TEST 01 CAST [ROB < OL! MN 



Gauge length, 100 in. s ti.>nal area, 17 in. 2 



\V v M i:i..\\ \ AI:-I v \ i. Ki I-.IKI. 1898 



Problem 173. The data in tin- inv-lin: table were obtained from a round, 

 hollow, c-ast-iron column 120 in. in Irn-th. :>.<". in. in external diameter, and 

 1.97 in. in internal diameter. Draw the load -compression and load -deflection 



