An Examination of Frictional Boundary Conditions and their Effect in an Elastic-Plastic Finite Element Solution

Summary

The metallurgical inhomogeneity of forged products is a direct consequence of their deformation history and seriously affects the strength and durability of the products. A predictive theoretical approach, capable of determining the metal flow during forming is therefore likely to be of great value and could reduce much of the ‘trial and error’ basis common in industrial tool design, with obvious savings in time and expense.

Earlier papers by the authors have demonstrated the use of an incremental elastic-plastic finite element method to predict the internal deformation in backward extrusion (1) and the bulk shape change of rings (2) which offers the most sensitive practical test of friction influence in forging. Advances in this type of analysis have until recently been hampered by inadequate knowledge of the frictional boundary conditions. The present paper describes a method of including surface friction (3) and is exemplified by an examination in detail of the influence of interfacial shear stress, or lubrication, on the deformation in ring compression.