面内異方性を持つIF鋼板の弾塑性特性とそのマクロ–メゾモデリング

概要

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Elasto–plasticity behavior of a IF steel sheet was investigated by performing uniaxial tension tests in three directions (0°, 45° and 90‚ to the rolling direction of the sheet), in-plane cyclic tension–compression test and bi-axial tension test. The sheet has strong planar r-value anisotropy (r0=2.15, r45=2.12 and r90=2.89) but very weak flow stress directionality. Equi-biaxial flow stress is as large as 1.23 times of the uniaxial flow stress. These elasto–plasticity deformation characteristics, as well as the Bauschinger effect and cyclic hardening behavior, are well described by a macro–plasticity model (Yoshida–Uemori model incorpolating with the 4th-order anisotropic yield function). Further, the simulation of elasto–plasticity stress–strain responses of the sheet were conducted by two types of crystal plasticity models, i.e., Taylor hypothesis based model and CPFEM, using the crystallographic orientation distribution data measured by neutron diffraction method. The models capture most of the above-mentioned deformation characteristics qualitatively, but the predicted anisotropy and the Bauschinger effect are weaker than those of the real material. The CPFEM gives more realistic results than the Taylor model.