Terumi Yamamoto

DYNAMIC TENSILE PROPERTIES OF IRON AND STEELS FOR A WIDE RANGE OF STRAIN RATES AND STRAIN

The tensile stress-strain curves of iron and a variety of steels, covering a wide range of strength level, over a wide strain rate range on the order of 10−3 ~ 103s−1, were obtained systematically by using the Sensing Block Type High Speed Material Testing System (SBTS, Saginomiya). Through intensive analysis of these results, the strain rate sensitivity of the flow stress for the large strain region, including the viscous term at high strain rates, the true fracture strength and the true fracture strain were cleared for the material group of the ferrous metals. These systematical data may be useful to develop a practical constitutive model for computer codes, including a fracture criterion for simulations of the dynamic behavior in crash worthiness studies and of work-pieces subjected to dynamic plastic working for a wide strain rate range.

Dynamic Tensile Properties of Steel Sheets for Automobiles

Abstract. In recent years, increasing interest has been paid to the accurate measurement of the entire tensile stress-strain curve of materials for a wide range of strain rates on the order of 10 ~10 s . Such data are needed to formulate precise constitutive equations for strain rate sensitive materials. The entire tensile stress-strain curves of a cold rolled high strength steel sheet (SPFC440), which due to its improved formability is widely used for automobile structures, and a cold rolled mild steel sheet (SPCE), for a wide strain rate range on the order of 10 ~10 s 1 were obtained by using the Sensing Block Type High Speed Material Testing System. Based on an investigation of experimental data, strain rate sensitivities of flow stresses of these materials were clarified for the wide strainrate range. The values of the true fracture strength and the true fracture strain were obtained. It was also found that the value of the fracture strength and the fracture strain are substantially not affected by the testing strain rates.