Friction in finite-element analyses of metalforming processes

Abstract In recent years the application of finite-element methods in studies of bulk metalforming processes has received considerable attention. However, the inclusion of accurate surface conditions has not been sufficiently examined. Much of the theoretical work has been performed with unrealistic conditions, frequently the two limits of zero and sticking friction. This paper discribes the development of a method for introducing friction into the finite-element analysis. This is achieved by the inclusion of a layer of elements whose stiffness is modified by a function of the interfacial shear factor. To investigate the proposed approach it is applied to the friction sensitive process of ring compression. A critical experiment is performed where the properties of an aluminum ring and of an applied surface layer of lead are known prior to the test. Excellent agreement is found both in the diametral changes and in the profile of the inner surface.