Parameter identification method for a polycrystalline viscoplastic selfconsistent model based on analytical derivatives of the direct model equations

inverse method for automatic identification of the parameters involved in a polycrystalline viscoplastic selfconsistent (VPSC) model is presented. The parameters of the constitutive viscoplastic law at the single-crystal leve l, i.e. the critical resolved shear stresses (CRSS) of slip and tu inning a nd the micro-hardening coefficients, can be identified using experimental d ata at the polycrystal level, i.e. stress-strain curves and deformation-ind uced textures. The minimization problem is solved by means of a Gauss-Newto n scheme and the sensitivity matrix is evaluated by analytical differentiat ion of the direct model equations. As a particular case, the optimization p rocedure for the Taylor full constraints (FC) formulation is also presented . The convergence and stability of the identification scheme are analysed u sing several validation tests for different deformation paths imposed to a polycrystal of hexagonal structure. As an example of application of this in verse method, the relative CRSS of the active deformation systems of a Zirc aloy-4 sheet are identified, based on several textures measured for differe nt reductions and rolling directions.