deviatorische

Deviatorische, in the context of physics and engineering, refers to the deviatoric part of a tensor—the portion that relates to distortion or shape change rather than to volume change. In continuum mechanics, any second-order tensor T can be decomposed into an isotropic (hydrostatic) part and a deviatoric part: T = T_iso + T_dev, where T_iso = (1/3) tr(T) I and T_dev = T − (1/3) tr(T) I. The isotropic part is the mean or hydrostatic component, while the deviatoric part is traceless (tr(T_dev) = 0) and captures changes in shape.

When applied to stress, this yields the deviatoric stress s = σ − p I, with p = (1/3) tr(σ) representing the hydrostatic pressure. The deviatoric stress is responsible for distortion without a change in volume, while the hydrostatic part changes volume but does not cause distortion.

The magnitude of the deviatoric stress is central to material behavior in many theories of plasticity and failure. Quantities such as the second invariant J2 of the deviatoric stress and the related von Mises yield criterion quantify when a material yields under distortion. In geotechnical engineering, a related measure q = σ1 − σ3 (the difference between principal stresses) is often used to describe the intensity of deviatoric loading.

In summary, deviatorische (deviatoric) components are the distortion-inducing parts of tensors, separated from isotropic parts that affect volume. This decomposition is widely used in solid mechanics, materials science, and geotechnical engineering to analyze and predict material response under complex loading.