Strength models play a key role in the numerical simulation of impact
events. A revised form of the Johnson-Cook strength model is proposed
in this paper. The revised model treats the sudden strengthening that
many ductile metals exhibit at strain rates greater than 10(4)/s. Stra
in rates of this magnitude are generally considered to be beyond the c
apability of the split-Hopkinson pressure bar and so such abrupt stren
gthening behavior is often not observed and reported. A method to econ
omically estimate all eight coefficients of the revised strength model
using quasi-static tension data and Taylor impact test data reduced w
ith a modified version of the EPIC finite element code is also describ
ed. Revised strength model coefficients were determined for: 7075-T6 a
luminum, OFHC copper, wrought iron, and a high-strength steel (Astrall
oy-V (R)). A good fit to the quasi-static tension data and Taylor impa
ct test results was obtained for these four different metals. The beha
vior of the revised strength model at high strain rates also compared
favorably with independent predictions from an analytical model calibr
ated with the Taylor impact data. (C) 1998 Elsevier Science Ltd. All r
ights reserved.