Prediction of forming limit diagrams of DP590 steel based on the M-K model with experimental verification

This paper analytically investigates forming limit diagrams (FLDs) of advanced high strength steel DP590 using the Marciniak-Kuczynski model (M-K model) with the strain rate effect. Tensile tests at various strain rates were conducted to obtain the strain hardening and strain rate hardening properties of DP590. The Johnson-Cook model was used to interpolate the experimental data with the strain rate effect. The FLDs of DP590 were then predicted with the M-K model. The material was assumed to be rigid-plastic and subjected to the flow rule based on the Hosford79 yield criterion. Punch stretching tests were conducted to verify the analytical results with different punch velocities to investigate the effect of the forming speed on formability. The analytical model without the strain rate effect underestimated the forming limits of DP590. The computed FLDs with the strain rate effect show good agreement with the experimental result especially when the exponent in the Hosford79 yield criterion is 8 for static forming and 10 for dynamic forming.