Effects of Strain Rate Control on Static Tensile Properties of Metallic Materials

The effects of different rate control modes on the tensile properties of metal materials were discussed. It is pointed out that there are differences between nominal rate and real-time feedback rate. For continuous yielding materials, the rate of extensometer feedback ė_Le is not significantly different from the strain rate ė_Lc estimated from the beam displacement rate and the parallel length of the sample. For discontinuous yielding materials, the strain rate of elastic section feedback ė_Le is much lower than the strain rate ė_Lc estimated by the parallel length of the sample, then ė_Le is higher than ė_Lc after yielding platform, and the two are substantially equal during the uniform deformation phase after yielding. Under the different test rates and control modes, with the increase of strain rate, the load increase rate increases, the difficulty of slip lines extending through the entire grain increases, so that the measured R_p0.2 and R_eL increase, R_m is basically in a stable state, the dimple size of the sample fracture decreases, the dislocation density of the sample increases, the elongation after fracture decreases, the plastic strain ratio does not change significantly, and the strain hardening index decreases.