Damage and fracture study of cold extrusion dies

Abstract

In the present paper die fracture in cold extrusion was investigated considering a few different die reduction zone geometries. A former finite element method (FEM) analysis of the process was developed to obtain the contact pressure distribution at the workpiece-die interface for each of the investigated geometries; subsequently a stress and strain analysis utilizing the BEM code Franc3D was carried out, with the aim to evaluate the crack propagation at each loading cycle, i.e. at each extrusion process. In this way the die life for each of the investigated extrusion die geometries was compared utilizing the Paris law and the values assumed by the stress concentration coefficient for different crack dimensions. Furthermore the effectiveness of the application of an external ring to modify the die stress state during the process, was investigated.