Modified Johnson–Cook model of SWRH82B steel under different manufacturing and cold-drawing conditions

Abstract

In this study, the parameters of the Johnson-Cook model of SWRH82B steel are determined to describe the dynamic mechanical properties and fracture behaviors of steel wires. A total of 299 specimens are tested to determine the parameters. Quasi-static tensile tests at varying temperatures (20–700 °C) and different strain rates (10−4–10 −2 s −1) and split Hopkinson pressure bar tests are conducted to identify the parameters of the Johnson-Cook model. Notch tensile tests are conducted to calibrate the Johnson-Cook fracture criterion model. The wires made from SWRH82B high-strength steel with different diameters and shapes have different material performance due to different manufacturing and cold-drawing process. Therefore, two cross-section types (circular and Z shapes) and seven diameters of high-strength steel wires are considered for the material characteristic tests. The strain rate hardening effect is not significant at low loading rates but has a remarkable effect at loads exceeding. Analysis of the stress-strain curves at elevated temperatures shows that the thermal softening effect of the two types of wires is evident and that the temperature sensitivity varies in different temperature ranges. In addition, the mechanical performance of circular wires with diameters ranging from 4.0 to 5.2 mm and Z-shaped wires with diameters from 4 to 6 mm are compared. Fractography of SWRH82B high-strength steel is conducted to investigate the failure mechanism at various temperatures and strain loading rates. Finally, an improved Johnson-Cook model is proposed considering the strain hardening of SWRH82B steel wires based on different shapes and diameters.