Approximate model to calculate foldover and strains during cold upsetting of cylinders. Part II. Use of the foldover model to estimate friction

This paper addresses an approach to calculate the friction coefficient during nonuniform compression of cylinders. The approach combines new friction-calibration curves (prepared using the finite-element analysis) that relate friction to workpiece shape and the foldover model from Part I. Foldover in upsetting is used in the same way that the change in internal diameter is used in the ring test to determine friction. However, the new approach has the advantage that measurements are taken directly from the workpiece. Comparisons of friction values calculated from the ring test and the new approach showed good agreement.