Just as we can calculate the mean stress, we can break the stress tensor down into two components. The first part or isotropic component is the mean stress, and is responsible for the type of deformation mechanism, as well as dilation. The second component is the Deviatoric stress and is what actually causes distortion of the body. When considering the deviatoric stress, the maximum is always positive, representing compression, and the minimum is alway negative, representing tensional.