• simulation of polycrystal deformation with grain and grain boundary effects

    جزئیات بیشتر مقاله
    • تاریخ ارائه: 1390/01/01
    • تاریخ انتشار در تی پی بین: 1390/01/01
    • تعداد بازدید: 1053
    • تعداد پرسش و پاسخ ها: 0
    • شماره تماس دبیرخانه رویداد: -
     modeling the strengthening effect of grain boundaries (hall–petch effect) in metallic polycrystals in a physically consistent way, and without invoking arbitrary length scales, is a long-standing, unsolved problem. a two-scale method to treat predictively the interactions of large numbers of dislocations with grain boundaries has been developed, implemented, and tested. at the first scale, a standard grain-scale simulation (gss) based on a finite element (fe) formulation makes use of recently proposed dislocation-density-based single-crystal constitutive equations (“scce-d”) to determine local stresses, strains, and slip magnitudes. at the second scale, a novel meso-scale simulation (mss) redistributes the mobile part of the dislocation density within grains consistent with the plastic strain, computes the associated inter-dislocation back stress, and enforces local slip transmission criteria at grain boundaries.

    compared with a standard crystal plasticity finite element (fe) model (cp-fem), the two-scale model required only 5% more cpu time, making it suitable for practical material design. the model confers new capabilities as follows:

     

    (1)

    the two-scale method reproduced the dislocation densities predicted by analytical solutions of single pile-ups.

    (2)

    two-scale simulations of 2d and 3d arrays of regular grains predicted hall–petch slopes for iron of 1.2 ± 0.3 mn/m3/2 and 1.5 ± 0.3 mn/m3/2, in agreement with a measured slope of 0.9 ± 0.1 mn/m3/2.

    (3)

    the tensile stress–strain response of coarse-grained fe multi-crystals (9–39 grains) was predicted 2–4 times more accurately by the two-scale model as compared with cp-fem or taylor-type texture models.

    (4)

    the lattice curvature of a deformed fe-3% si columnar multi-crystal was predicted and measured. the measured maximum lattice curvature near grain boundaries agreed with model predictions within the experimental scatter.

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