A crystal plasticity study of the necking of micro-films under tension

An integrated crystal viscoplastic modeling process has been developed to account for the effect of microstructure in the mechanical response of polycrystalline materials. Grain distributions, including size, shape and orientation, are generated automatically based on probability theories using VGRAIN software. For each set of control parameters (average, maximum and minimum grain size) used in the micro-film simulations, six grain orientation patterns were generated randomly for a micro-film based on a gamma distribution; a large number of analyses have been carried out to account for statistical variations in the spatial pattern of grain orientations. The simulations are used to investigate the effects of grain size and orientation on necking and flow stress in stainless steel under uniaxial tension, and to quantify the extent that variability in the spatial distribution of orientations affects the predictions. Based on the numerical studies, a map was generated indicating under what circumstances macro-mechanics theory can be used and when Crystal Plasticity (CP) theory must be used to ensure the accuracy of the analysis; if the theories are not used appropriately, huge errors can be expected.