Stress-Strain Curves for a Metal Wire and Rubber:

The experimentally observed variation of strain of a material with the applied deforming force gives valuable information about its practical utility. In fact, on the basis of such observations, some laws have also been formulated that holds true for solids in general under certain conditions. Let us discuss a few such experimental curves and, in the procedure, describe a few important parameters of solids.

Metal Wire

Refer to Figure which shows the variation of stress with the variation of strain in a metallic wire of uniform cross-sectional area subjected to an increasing load (deforming force).

Figure: Stress-Strain Curve for Steel Wire

Note from the figure that there are certain distinct regions and special points on this curve. Now Let us briefly know their significance:

Region of Proportionality (OA)

Note that the region OA of the curve is a straight line which implies that in this region, stress is proportional to strain. This linear relation between stress and strain is a characteristic of a perfectly elastic body.