STRESS AKD BEFOKMATIOK 3 



shear, these may arise in various ways. In general, five different 

 cases of strain may be distinguished, each of which must be con- 

 sidered separately. These are as follows : 



1. If the forces act along the same line, toward or away from 

 one another, the strain is called compression or tension (Fig. 1, a). 



2. If the forces tend to slice off a portion of the body by sepa- 

 rating it along a surface, the strain is called shear (Fig. 1, ft). 



10 12 14 16 

 EXTENSION, PER CENT 



FIG. 2 



18 20 22 24 



3. If the forces act transverse to the length of the body (usually 

 perpendicular to the long axis of the piece), so as to produce lateral 

 deflection, the strain is called bending, or flexure (Fig. 1, c). 



4. If one dimension of the body is large as compared with the 

 other two, and the forces act in the direction of the long dimension 

 and toward one another, the strain is called buckling, or column 

 flexure (Fig. 1, d). 



5. If the forces exert a twist on the body, the strain is called 

 torsion (Fig. 1, e). 



Two or more of these simple strains may occur in combination, 

 as illustrated in Fig. I,/. 



