Lubricant Modeling and Its Effect on Simulation of Material Forming

Abstract

Solid cylinder upsetting is analyzed using three different approaches for frictional boundary condition modeling. These are (1) constant shear friction factor, (2) experimentally measured frictional stresses, and (3) analytical models accounting for lubricant entrapment and redistribution. All three approaches are implemented in the CFORM finite element code. The error between the three approaches and actual experimental measurements of the material deformation and interfacial pressures is investigated. It is shown that the constant shear friction factor is more accurate for solid film lubricants than for liquid lubricants. However, the calculations indicate that if accurate prediction of near net shape forming processes is to become a reality, improvements need to be made in the characterization of frictional boundary conditions. New theoretical developments applicable to arbitrary shapes and more accurate than the constant shear friction factor approach are needed.