Effects of friction laws on metal forming processes

In this paper, the Coulomb friction law and the constant shear friction law were compared and investigated in detail using a rigid-plastic finite element method with emphasis on their application in bulk metal forming. The ring compression test for two different materials was used to evaluate the two friction laws, and then their effects on metal flow lines and forming loads for various friction-sensitive metal forming processes including strip rolling, ring gear forging, multistep extrusion, and pipe shrinkage and expansion were investigated. It was shown that considerable differences exist between the two friction laws, especially in friction-sensitive metal forming processes.