Semi-analytical contact model to determine the flattening behavior of coated sheets under normal load

Friction influences the formability in sheet metal forming processes. It depends on the local contact condition between tool and sheet metal. Therefore, precise estimation of real area of contact is the first step for an accurate prediction of friction. In this study, a multi-scale contact model is developed to predict deformation of asperities on a rough uncoated and coated surfaces under normal load. The model accounts for the coating thickness and material behavior of coating and substrate. Finite element simulations are performed to determine the contact pressure of single asperities of different sizes. These are used to determine the real area of contact. The model is validated relative to the experiments performed on uncoated and zinc coated steel sheets.