An attempt was made to derive the parameters in the macroscopic constitutive equations, for the plasticity of face-centered cubic single crystals, by means of simulations which were performed at the dislocation level. The macroscopic model was based upon the main physical mechanisms which were involved in plastic deformation. The three constitutive laws which were involved treated the total dislocation densities on each glide system as fundamental variables. These three expressions were derived from the physical processes which governed the behaviour of a single dislocation; as adapted for use at the macroscopic scale. Published results could be used for the identification of the material parameters for various face-centered cubic materials, but some of these quantities were mean values and had to be treated as phenomenological parameters. A good way to determine such values was to use a numerical tool in which each dislocation was individually simulated in a three-dimensional network. Such a tool worked at the mesoscopic scale of several microns, and dealt with dislocations which were discretized into pure screw and edge segments. It included all of the familiar elementary events which governed dislocation motion (line tension effect, Frank-Read multiplication, cross-slip, junction formation). Cross-analysis of several specific mesoscopic simulations permitted the determination of the values of some macroscopic parameters, and also the validation of both models.

Identification through Mesoscopic Simulations of Macroscopic Parameters of Physically Based Constitutive Equations for the Plastic Behaviour of FCC Single Crystals. M.Fivel, L.Tabourot, E.Rauch, G.Canova: Journal de Physique IV, 1998, 8[8], 151-8