Large strain mechanical behavior of 1018 cold-rolled steel over a wide range of strain rates

Abstract

The large-strain constitutive behavior of cold-rolled 1018 steel has been characterized at strain rates ranging from $$\dot \varepsilon = 10^{ - 3} $$ to 5 × 104 s−1 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 104 s−1. The study also shows a marked strain rate sensitivity of the steel at rates exceeding 100 s−1. With increasing strain rate, the apparent average strain hardening of the material decreases and becomes negative at rates exceeding 5000 s−1. 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.