What is "t-criterion"

The T-failure criterion is a set of material failure criteria that can be used to predict both brittle and ductile failure.

These criteria were designed as a replacement for the von Mises yield criterion which predicts the unphysical result that pure hydrostatic tensile loading of metals never leads to failure. The T-criteria use the volumetric stress in addition to the deviatoric stress used by the von Mises criterion and are similar to the Drucker Prager yield criterion. T-criteria have been designed on the basis of energy considerations and the observation that the reversible elastic energy density storage process has a limit which can be used to determine when a material has failed.