Applicability of Hardening Models for Automobile Steel Sheets

With DX56D+Z, HC220BD+Z, HC420LA and HC420/780DP automobile steel sheets as research materials, flow stresses and plastic strains obtained by uniaxial tensile testing were fitted by Ludwik, Swift, Hockett-Sherby, Voce, Swift-Hockett-Sherby and Swift-Voce hardening models, and the fitting accuracy of the six hardening models was compared and analyzed. With HC420/780DP steel sheet as an example, the fitting effect of the six hardening models was analyzed for predicting flow stresses in a large strain range (after necking).The results show that in the plastic deformation stage, the growth mode of flow stresses described by Hockett-Sherby hardening model was the closest to the test results, and the fitted flow stresses coincided with the measured results at the highest degree. The difference of flow stresses in the large strain range of HC420/780DP steel obtained by extrapolation with the six hardening models was relatively large. Swift-Hockett-Sherby and Swift-Voce mixed model had higher degrees of freedom of fitting, and had more significant fitting effect.