A Fully-Coupled Approach for Modelling Plastic Deformation and Liquid Lubrication in Metal Forming

This paper presents a new approach for combined modelling of plastic deformation andliquid lubrication in the contact interfaces between material and tooling in metal forming includingsituations where the lubricant is functioning as a pressure carrier. The approach is an alternative toconventional modelling techniques based on the utilization of friction shear stresses built uponexisting friction laws as e.g. the Coulomb law and the law of constant friction stress. As such itrepresents a shift from phenomenological modelling adopting an artificial friction layer techniqueconsisting of interface elements with fictitious small stiffness to physical modelling based on a fullycoupled procedure in which the lubricant flow and the plastic deformation of the metallic materialare solved simultaneously. The approach takes advantage of the intrinsic velocity-pressurecharacteristics of the finite element flow formulation which stands on the border line between fluidand solid mechanics and allows treating the lubricants as viscous incompressible (or nearlyincompressible) fluid and the metallic materials as non-Newtonian, high viscous, incompressiblefluids. The presentation is focused on the theoretical and numerical fundamentals of the proposedapproach and includes selected examples in order to illustrate its advantages and limitations.