Yield behavior of low-carbon steel sheets (0.07%C) has been examined under the strain rate of 10-4 to 10-1/sec at room temperature using an Instron tensile machine. Stress-strain curves have been recorded by using a transient converter (NF, E-5001: 8bits×1024wards), since the response of a X-Y, T recorder is not sufficient for the measurements under high strain rates. The experimental results by the transient converter show that the upper and lower yield points appear clearly before the crosshead speed reaches to a given value of high strain rate. The transient converter is found most desirable in order to observe the yield behavior under high strain rates. The results also show another break point of the strain rate dependence of yield stress at the strain rate of ∼3 ×10-3/sec, which is different from M. J. Manjoin (1944)'s strain rate i. e. ∼10-1/sec. The strain rate dependences of yield stress, yield point elongation, and tensile strength in the range of high strain rate above ∼3×10-3/sec are larger than those at lower strain rates. The yield stress is much more sensitive to the strain rate as compared with the tensile strength.
