Validation of Predictive Approaches for Ductile Fracture in Cold Extrusion

Abstract

Cold extrusion is sometimes accompanied by some typical internal defects, known in the technical literature as “central bursts”, which dramatically could affect the component behaviour during its service life. Several researchers, following both analytical and numerical approaches have attempted central bursting prediction in extrusion. Among the latter several approaches have been proposed in the literature, namely the ones based on the use of ductile fracture criteria and the ones founded on the damage mechanics analysis. Each one of these approaches presents some advantages and drawbacks. In the paper the authors analyze a set of cold extrusion processes on AISI 1040 specimens at varying the most relevant process parameters. The occurrence of central bursting has been predicted utilizing all the classes of approach previously mentioned and the goodness of the predictions has been validated through a set of experimental tests. On the basis of this validation the usefulness and the industrial suitability of each approach is discussed.