The pole of the Mohr diagram

The pole of a Mohr diagram, for the two-dimensional case, is a unique point on the Mohr circle which permits any point on the Mohr circle to be related to the direction in the physical plane associated with that point. A Mohr diagram can be constructed for any second rank tensor. To illustrate the simplicity of this geometrical construction two examples of the use of the pole are presented, one for the strain tensor and the other for the stress tensor.