Stress

Cauchy tetrahedron

“Cauchy tetrahedron” by Sanpaz - Own work.
Licensed under CC BY-SA 3.0 via Wikimedia Commons.

Stress tensor

\[ \mathbf{\sigma} = \begin{bmatrix} \sigma_{11} & \sigma_{12} & \sigma_{13} \\ \sigma_{21} & \sigma_{22} & \sigma_{23} \\ \sigma_{31} & \sigma_{32} & \sigma_{33} \end{bmatrix} \]

Visual definition

“Components stress tensor cartesian” by Sanpaz - Own work.
Licensed under CC BY-SA 3.0 via Wikimedia Commons.

• First subscripted index refers to the index of the unit vector that is normal to the face.
• Second subscripted index refers to the component of traction vector.