Modeling friction near sharp edges using a Eulerian reference frame: appliction to aluminium extrusion

When using a Eulerian finite element approach to model the material deformation that occurs in e.g. forming processes, the accurate capturing of friction is of crucial importance to the quality of the computational results. For the algorithm that incorporates the frictional phenomena into the system of equations, the direction of the contact surface normal in a node is an essential parameter. However, this normal is not uniquely defined in the nodes of a curved, discretized surface. Therefore, a substitute normal has to be reconstructed. The commonly used (averaging) methods to determine the normal are either mesh or geometry dependent which renders poor results on coarse meshes. Therefore, a new method is presented that reconstructs the direction of the normal from the flow field near the node. Comparing the flow fields on a coarse mesh with those obtained on a very fine mesh reveals that a more accurate solution field is obtained using the method introduced here.