COMPUTER-SIMULATION OF THE EFFECT OF GRAIN-SIZE ON THE PROPERTIES OF POLYCRYSTALLINE SPECIMENS BY FINITE-ELEMENT METHOD

On the basis of the data of single crystal deformation and the characteristics of polycrystal deformation, the deformation of a set of polycrystals with special orientations and special arrangement of grains were simulated in this paper to investigate the effect of grain size on the plastic deformation of grains and the stress distribution in polycrystals, particularly near grain boundary. The results obtained indicate that the relation of the true stress and grain size is according with the well known empirical relation sigma = sigma-0(epsilon) + k(epsilon)d-1/2 and it is found that the results by computer are a complement of experimental data. The k(epsilon) and sigma-0(epsilon) values, vary with the true strain. The polycrystal strengthening is mainly due to the contribution of the work hardening and the grain boundary rim (complex slip rim) which varies with gain size and true strain. The presence of grain boundary makes the stress near grain boundary markly up or down depending on orientation of grain and orientation difference between adjacent grains.