  Tensile tests were conducted on dual-phase high-strength steel in a
Split-Hopkinson Tension Bar at a strain-rate in the range of 150-600/s and in a
servo-hydraulic testing machine at a strain-rate between 10-3 and 100/s. A
novel specimen design was utilized for the Hopkinson bar tests of this sheet
material. Digital image correlation was used together with high-speed
photography to study strain localisation in the tensile specimens at high rates
of strain. By using digital image correlation, it is possible to obtain
in-plane displacement and strain fields during non-uniform deformation of the
gauge section, and accordingly the strains associated with diffuse and
localised necking may be determined. The full-field measurements in high
strain-rate tests reveal that strain localisation started even before the
maximum load was attained in the specimen. An elasto-viscoplastic constitutive
model is used to predict the observed stress-strain behaviour and strain
localisation for the dual-phase steel. Numerical simulations of dynamic tensile
tests were performed using the non-linear explicit FE code LS-DYNA. Simulations
were done with shell (plane stress) and brick elements. Good correlation
between experiments and numerical predictions was achieved, in terms of
engineering stress-strain behaviour, deformed geometry and strain fields.
However, mesh density plays a role in the localisation of deformation in
numerical simulations, particularly for the shell element analysis.
