Mohr's Circle

A geometric construction that represents a two‑dimensional state of stress on a plane by plotting normal stress (σ) versus shear stress (τ) so that rotation of the material plane corresponds to motion on the circle; principal stresses appear at the circle’s extrema and maximum shear is given by the circle radius.

A planar stress-transformation diagram that represents the normal and shear stress components acting on every possible oriented plane through a material point in two-dimensional (plane stress) conditions, and that allows direct determination of the principal stresses, principal plane orientations, and maximum shear stress by geometric construction.