A study on variable friction model in sheet metal forming with advanced high strength steels

Conventional Coulomb model assumes constant friction coefficient in sheet metal forming simulation. It tends to predict too high friction shear stress in forming advanced high-strength steels (AHSS). Study is conducted by firstly designing an experiment method to develop a pressure-dependent variable friction model for DP780 AHSS sheet sliding against DC53 cold-work tool. The model is then used to simulate the forming and springback of U-shape bending under tension. Comparison of the predicted results with (i) pressure-dependent variable friction model, (ii) constant friction model, and the result of experimental verification indicates significant improvement of springback prediction with the proposed model.