Verification of Friction Models Implemented in the Simulation Software

Modern approaches in simulations of sheet metal stamping processes are based on definition the friction coefficient as not constant, but the different value in different regions, considering the nature of the actual deformation process in each individual region. In this contribution the regression and analytical models to determine the friction coefficients under blankholder and on the die drawing edge by strip drawing test are presented. These models were verified by experimental strip drawing test under the same contact conditions. Zn coated steel sheets for the automotive industry were used in experiments and simulations – extra deep drawing quality DX54D and high strength steel TRIP. The results indicate, that friction coefficients are not constant and depend on the pressure on the die contact surfaces. Friction coefficients were determined also at the cup test by the regression model of drawing versus blankholding force. Conformity of friction coefficients obtained by the cup and the strip tests was confirmed. Model of friction applied in FEM simulation was verified by cup test and good conformity was found out.