Mohr’s circle is a graphical representation of a general state of stress at a point. It is a graphical method used for evaluation of principal stresses, maximum shear stress; normal and tangential stresses on any given plane.
Following important points must be noted for graphical analysis by Mohr’s circle-
The normal stresses are plotted along the abscissa. The tensile stresses are considered positive and compressive stresses are considered negative.
The shear stress is plotted as ordinate. Shear stress which causes clockwise rotation of element is considered positive while other one which causes anticlockwise rotation is considered negative.
Coordinates of various points on Mohr’s circle represent the state of stress at different planes.
The radius of circle to any point on it’s circumference represents the axis directed normal to the plane whose stress components are given by the coordinates of that point.
The angle between radii to points on Mohr’s circle is twice the angle between the normals to the actual planes represented by these points. The rotational sense of this angle is same as that of rotational sense of the actual angle between the normals to the plane.
Watch the video below to understand the derivation –