Prandtl–Reuss equations

Summary

The Prandtl–Reuss equations are the constitutive equations of an isotropic elastic-plastic solid at small strains. They use the von Mises yield criterion and the associated flow rule. They give the strain rate as the sum of an elastic part from Hooke's law and a plastic part parallel to the deviatoric stress. They are the standard model of metal plasticity at small strains; without the elastic part they become the Lévy–Mises equations.