The dependence of strain rate on deformation strength was investigated on various pre-strained specimens of carbon steels under plane strain. The strain rate was from 4×10-3 to 2×104sec-1. In the range of high strain rate, a newly developed Stress-Strain Curve Direct View Device was used for the measurement of deformation strength. Furthermore, Digital Memory Scopes were utilized to obtain highly accurate experimental data. The results obtained are summarized as follows:
(1) The deformation strength σ in plane strain is related to strain ε, strain rate ε and temperature T by
σ(ε, ε, T)=k0εn1εn2exp(α/T)
where n1 is the strain hardening exponent, n2 the strain rate exponent, α the temperature dependence index and k0 the strength constant.
(2) The carbon equivalent value of yield stress Cy and the strain hardening exponent n1 and the temperature dependence index α are related each other. If Cy is known, the deformation strength in plane strain can be estimated from the average value of n2 of all kinds of steel by using this correlation.
