INVESTIGATION OF THE ELASTOPLASTIC BEHAVIOR OF FCC POLYCRYTALS USING A FFT NUMERICAL SCHEME

International audienceThis work is devoted to the study of the effective mechanical response and strain and stress field fluctuations in FCC untextured polycrystals using a full-field numerical approach for a crystalline rate-independent elastoplastic constitutive behavior. The full-field simulations make use of the fast Fourier transform (FFT) numerical scheme. The first application of the developed scheme, which is presented in this paper, is the study of the elastoplastic behavior of non-hardening polycrystals in conjunction with two rate-independent crystal plasticity models: the standard Schmid law and the regularized Schmid law. The macroscopic yield stress is first obtained with the standard Schmid law by averaging the yield stresses calculated on several and different representative volume elements (RVE), each of them being constituted of 500 randomly distributed grains. This numerical estimate is then compared to published results for different nonlinear extensions of the self-consistent (SC) scheme for the case of viscoplasticity at very low rate sensitivity values. Among the different SC models considered, the second-order estimate developed by Ponte Castañeda in 1996 [1] appears to be the most accurate. The influence of the regularization of the Schmid law on the polycrystalline response is then studied using the FFT numerical scheme. It is shown that, unlike the incremental SC model, the FFT numerical estimate is not sensitive to the regularization of the local plastic yield criterion