Effect of Strain Rate on Tensile Properties of Dual Phase Sheet Steel

Abstract

　　　Variations in tensile properties and temperature rise of Dual Phase sheet steel with strain rate were investigated. The uniform elongation did not change much, but the local elongation decreased over a range of strain rates from 0.001/s to 5/s. The material temperature was about 300K during uniform tensile deformation. In quasi-static tensile tests, the n value did not change at a temperature of less than 373K or less, but increased at a temperature of over 473K. Softening of the sheet did not occur at slow strain rates because the temperature rise was very small. Similarly, at a strain rate of 60/s, uniform elongation remained unchanged, but local elongation increased. The temperature during uniform elongation was about 300K, but exceeded 473K at the end of local elongation, resulting in increased local elongation. Strain increased during all of elongation at a strain rate of 1260/s or more. The following conclusions were obtained for the elongation. At strain rates less than 5/s, stress concentration due to temperature difference causes local elongation to decrease as the strain rate becomes faster. At strain rates above 60/s, the local elongation as well as the n value increased due to softening of the sheet steel caused by plastic heat generation.