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The large-strain constitutive behavior of cold-rolled 1018 steel has been characterized at strain rates ranging from ϭ 10 Ϫ3 to 5 ϫ 10 4 s Ϫ1 using a newly developed shear compression specimen (SCS). The SCS technique allows for a seamless characterization of the constitutive behavior of materials over a large range of strain rates. The comparison of results with those obtained by cylindrical specimens shows an excellent correlation up to strain rates of 10 4 s Ϫ1 . The study also shows a marked strain rate sensitivity of the steel at rates exceeding 100 s Ϫ1 . With increasing strain rate, the apparent average strain hardening of the material decreases and becomes negative at rates exceeding 5000 s Ϫ1 . This observation corroborates recent results obtained in torsion tests, while the strain softening was not clearly observed during dynamic compression of cylindrical specimens. A possible evolution scheme for shear localization is discussed, based on the detailed characterization of deformed microstructures. The Johnson-Cook constitutive model has been modified to represent the experimental data over a wide range of strain rates as well as to include heat-transfer effects, and model parameters have been determined for 1018 cold-rolled steel.#

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