Explain tangential or shearing stress and shearing strain.

(N/A) Tangential or Shearing Stress: When two equal and opposite deforming forces are applied parallel to the cross-sectional area of a cylinder,causing a relative displacement between the opposite faces,the restoring force per unit area developed is known as tangential or shearing stress.
Shearing Strain: As a result of the applied tangential force,there is a relative displacement $\Delta x$ between the opposite faces of the cylinder,as shown in the figure. The strain produced is known as shearing strain and is defined as the ratio of the relative displacement of the faces to the length of the cylinder $L$:
$\text{Shearing strain } \varepsilon_{\theta} = \frac{\Delta x}{L} = \tan \theta \approx \theta$
Here,$\theta$ is the angular displacement of the cylinder from the vertical. Since $\theta$ is usually very small,$\tan \theta$ is nearly equal to $\theta$.
$A$ common example is when a book is pressed with the hand and pushed horizontally; the vertical side makes a small angle $\theta$ with the vertical.