Modelling and simulation of friction in metal forming applications

Başpınar, Murat
In this study, a generalized friction model is proposed to be applied in metal forming processes. Friction model takes into account junction growth of asperities during combined loading and in order to represent real life cases. Asperities are defined by a curved surface such that elliptical contact is obtained between sheet and tooling. Curved surfaces with radius of curvature ratio of 0.5, 0.6, 0.8 and 1 are considered. Approximation equations are derived for junction growth until sliding inception for combined loading with sticking assumption. Lubrication mechanism is applied by solving the modified Reynolds equation. A finite element solution of rough contact zone is applied to solve lubricant pressure. Contact patch method is used to calculate the shear stress generated by rigid tooling asperities that penetrate into deformable asperities of workpiece. A fast and robust solid (real) contact area estimation approach is proposed to obtain relation between normal load and solid (real) contact area. A cylindrical cup drawing process is selected to apply the proposed friction model and calculate coefficients of friction along a radial line. Real surface roughness of the undeformed steel blank material is measured by an optical 3D surface roughness measurement insturement for a sample area. Deep drawing process is performed up to 35 mm cup height then; strain and punch force measurements are taken and an iterative method is used during simulations at every 5 mm cup height. Surface simplification is applied on the real surface asperities and assumed to be repetative throughout the blank.
Citation Formats
M. Başpınar, “Modelling and simulation of friction in metal forming applications,” Ph.D. - Doctoral Program, Middle East Technical University, 2024.