Constitutive Model for an FCC Single-Crystal Material

Abstract

Taking into account the effects that the components of tension stresses couple with components of torsion stresses when off-axis loads are applied to orthotropic materials, Hill s yield criterion for plastically orthotropic solids is modified by adding an invariant that is composed of the product item of quadratic components of the deviatoric stress tensor, and a new yield criterion is put forward in terms of the characteristics of the face-centered cubic (FCC) single-crystal material. The correlation of prediction and experiments is very good, and the new criterion is used to predict the yield stresses of an internal single-crystal, Nickel-based superalloy, DD3, which is more accurate than that of Hill s at 760?C. Equivalent stress and strain that adapt to the new criterion are defined. Thinking of the yield function as a plastic potential function from the associated flow rule, the elastic plastic constitutive model for the FCC single-crystal material is constructed, and the corresponding elastic plastic matrix is educed. The new yield criterion and its equivalent stress and strain will be reduced to Von Mises  yield criterion and corresponding equivalent stress and strain for isotropic materials.