STRENGTH OF \VHnn;ilT li;n\. 



strength from the second formula, which assumes a 

 uniformity of stress over the section. (See par. 16, p. 41.) 

 The results are shown in the fifth column of the following 

 table; they agree very well with the direct shearing 

 strengths : 



\YIMHGHT IRON IN SHEAR AND TORSION. 



On Fig. 171 is a load-strain diagram from a wrought- 

 iron shaft tested by the author. 



183. Effect of Temperature on the Strength of 

 Wrought Iron. Variations of temperature affect the 

 strength properties to a considerable extent. 



As the temperature to which the test bar is exposed 

 during a tension test increases, the ultimate strength of 

 wrought iron increases steadily up to about 450 to 

 500 Fah., when it begins to diminish again, which it 

 continues to do up to the highest temperatures which 

 have been tried, viz., about 1,600 Fah. The rate of 

 increase and decrease is shown graphically on Fig. 172. 



