---

The stress tensor is a second order tensor named after Augustin-Louis Cauchy. The tensor consists of nine components σ_ij that completely define the state of stress at a point inside a material in the deformed state, placement, or configuration.

The stress tensor σ_ij can be calculated as adding two other stress tensors:

(i). a mean normal stress tensor, πδ_ij, which tends to change the volume of the stressed body;
(ii). a deviatoric component called the stress deviator tensor, s_ij, which tends to distort it.