DYMAT 2009
Volume 2, 2009
DYMAT 2009 - 9th International Conference on the Mechanical and Physical Behaviour of Materials under Dynamic Loading
Page(s) 1649 - 1655
Section Numerical Simulations
Published online 15 September 2009
DYMAT 2009 (2009) 1649-1655
DOI: 10.1051/dymat/2009233

Measuring dynamic strength at low plastic strains using a hat-shaped specimen

Z. Lovinger, Y. Ashuach and O. Firstenberg

RAFAEL, P.O.B 2250, 31021 Haifa, Israel

Published online: 15 September 2009

In the standard derivation of the stress-strain curve from a Split Hopkinson Pressure Bar (SHPB) test, the initial region of the stress-strain curve, at low strains, does not reflect the real strength of the material. The measurement in this initial region is affected by reverberations in the specimen, and the standard assumption of stress equilibrium does not hold. For typical specimen dimensions and striker velocities, our SS304L specimens reach strains of 20–50%, but the equilibrium required for the analysis is achieved only above strains of 5–10%. Therefore, in calibrating a constitutive model, e.g. the Johnson-Cook (JC) model, the free parameter of the model that expresses the material's initial strength cannot be fixed correctly from the experimental data. While conducting 2D simulations of SHPB tests with hat-shaped specimens, we have found that the strain-gauge signals are sensitive to the behavior at low plastic strains. We have used this information as a complementary test for the calibration of a JC model at the low strain region. Using 2D simulations, we demonstrate the particular stress fields in the deforming hat-specimen as well. These simulations prove to be a powerful tool in the calibration procedure.

© EDP Sciences 2009