Results and Outlook Development of a Friction Approach for the FE Method of Sheet Metal Forming Based on Multi-Scale Modeling Motivation Prof. Dr.-Ing. B.-A. Behrens Prof. Dr. P.-A. Guidault Goals Methods Dipl.-Math. B. Homann ViVaCE „Virtual Materials and their Validation: German-French School of Computational Engineering” – IRTG 1627 • Correlations between occurring normal force, effective plastic strain, direction of motion, and resulting roughness = 1 n , max ,α • Function for friction coefficient of change in roughness, sliding velocity, and direction of motion = 2 , ∆, Angle between direction of motion and rolling direction Angle between direction of measurement and rolling direction Arithm. mean surface roughness measured in to rolling direction n Maximal occurring normal pressure max Maximal occurring effective plastic strain Friction coefficient Current sliding velocity ∆ Change in roughness • Strong influence of friction on the part quality • Existing laws for friction are not adequate for the realistic description of local contact conditions. Investigation of surface topography evolution • Material: aluminum alloy AlMg3 (EN AW-5754) • Basic experiments: Pressure test (PT) Tensile test (TT) Strip drawing test (SD) • Roughness measurement before and after the tests • Measurements in and to rolling direction Main influences on deep drawing processes Focus of study: Friction modeling in FE simulation Setup to apply contact pressure Setup for tensile test Setup for strip drawing test Strong influence of friction coefficient μ on the result, e.g. sheet thickness Friction modeling • Mathematical description of the friction coefficient • Depending on Roughness evolution Forming parameters Implementation • In FE software LS-DYNA • User subroutine usrfrc in dyn21.F Algorithm of the new friction law Specimens of different rolling directions Longitudinal 0° Transversal 90° Diagonal 45° 59 mm 730 mm 20 mm 9 mm Simulation of basic experiments • To analyze the forming parameters • With respect to rolling direction x y z Sheet thickness [mm] 1.10 1.08 1.06 1.04 1.02 1.00 0.99 0.97 0.95 0.93 0.91 initial Numerical models of tensile test (upper) and strip drawing test (lower) with evaluated element for roughness calculation Further investigations • Further parameter studies to extend the model • Adoption/adjustment of the model to different materials ViVaCE-Projects with strong Interaction • Multiscale FEM for Rubber Friction on Rough Surfaces (P. Wagner) • Multiphysics Homogenization Schemes for Microstructured Interfaces (N. Noii) y x z Initial state Stretched state Evaluated element Specimen Force Chafe body of the machine z x y Initial state Drawn state Evaluated element eps max [−] 0 [μm] Example of roughness-strain dependence of tensile test for -specimen 0° 0° -specimen 0° 90°