Dynamic constitutive relation and fracture model of Q235A steel

摘要

Strength and ductility data for Q235A steel from 20°C to 950°C was obtained from a series of experimental tests. The stress rate sensitivity was studied by conducting Split-Hopkinson Tension Bar (SHTB) test and uniaxial tension test on smooth cylindrical specimens while the influence of stress triaxiality on ductility was revealed by conducting upsetting tests, tension tests on pre-notched cylinder specimens and torsion tests on SASs. Slightly modified versions of the two Johnson-Cook (J-C) models describing flow stress and fracture strain are presented to characterize the properties of Q235A steel as function of strain rate, temperature and stress triaxiality. Corresponding model parameters were calibrated based on the test data and with the help of finite element calculation. It was found that the modified Johnson-Cook (MJC) models give more close predictive results compared with the original J-C models.