TORSION TEST. 



215 



the diameter of the bar with a vernier calliper, it was placed 

 in the machine and the beam balanced with the poise 

 weight set to zero. The instrument used for measuring 

 the angular deflections was next fixed in its place on the 

 bar, the distance between the two halves being 8 in., this 

 constituting the portion of the bar whose strains were 

 measured. When the test was begun, the pointer of the 

 measuring instrument was set to zero, and the twisting 

 moment on the bar varied by increments of 25 inch-pounds 

 up to the elastic limit, and increments of 50 inch-pounds 

 beyond this point. The position of a known point on a hand 

 wheel was also noted at the start, so that, by counting its 

 revolutions and parts of a revolution, it was possible to 

 measure the angles of twist beyond the elastic limit. 

 Below is a table of the actual readings taken : 



RECORD OF TORSION TEST ON MILD STEEL BAR. 

 Diameter of Bar, 0-472 in. ; Length of Measured Portion, 8 in. 



* At this point fracture occurred. 



Taking the readings up to 450 inch-pounds, the dif- 

 ferences per 225 inch-pounds are 



3-50 3-30 3-12 2'93 275 2'57 2'38 2-16 

 1-74 1-55 1-33 1-13 0'91 0'73 0'52 0'30 



176 



175 



1-79 



1-80 



1-84 



1-84 



