TORSION TEST. 



219 



121. Diagram Plotted from the Torsion Test. A 



fraphical representation of the results of this test is given on 

 ig. 105. Here the twisting moments are plotted horizontally 

 as abscissae, and the corresponding angular deflections 



DEGREES. 



.3500F 



3000 



25001- 



2000 



1500 



1000 



500 



1000 1200 1400 l600piuSiD8. 



FIG. 105. Diagram of Torsional Test of Mild Steel Bar 0-472 in, 

 diameter and 8 in. long, showing twisting moments and corres- 

 ponding angles of twist. 



vertically upwards as ordinates. The general form of the 

 curve obtained is not unlike the tension curve for the 

 same metal. It will be seen that there is an elastic portion 

 which nearly coincides with the base line for the scale 

 used, a distinct step at the elastic limit, and an upward 

 curve from this point. The curve for wrought-iron is very 

 similar, while that for cast-iron is like the one for tension, 



to begin with, and 

 curve. 



oii_i_ij.c*i , T AIIIO UIMU i\Ji \jao\j-i LULL 10 iirvc iii 



being approximately a straight line t< 

 gradually merging into slightly upward 



122. Fractures for Torsion Specimens. The fractures 

 for the more ductile materials, when tested to destruction in 

 torsion, take place roughly on planes at right-angles to the 

 axes of the specimens. Actual fracture occurs without 

 any violence, and there is nothing very characteristic about 

 the broken surfaces. 



