I :,,s 



REAL STRESS DIAGRAMS. 



towards lamination, such as wrought iron ; and C shows how 

 a hard, brittle metal like cast iron, fails by the sliding nr 

 shearing across a plane inclined to the axis at an angle of 

 about 45 deg. It must, of course, be understood that the 

 fracture is not nearly so clean and regular as that shown, 

 but it approximates to this form. 



96. Real Stress-strain Diagrams. Two diagrams have 

 been shown on Figs. 68 and 74, one being what is gener- 

 ally called the "stress-strain" diagram for a specimen of 

 mild steel tested in tension, and the other a similar curve 



FIG. 75. 



for copper tested in compression. The term " stress-strain " 

 as applied to these diagrams is not the correct one. It 

 would be more appropriate to call them " load-strain " dia- 

 grams. Loads are plotted horizontally and the correspond- 

 ing strains vertically. If the stresses were at all times 

 proportional to the loads, in a constant ratio, the curves 

 would be converted into " stress-strain " diagrams by a 



