Cold Heading of Cylindrical PVC Billets: An Experimental and Theoretical Investigation

The design of upset forged metal parts by cold heading is presently well established. Major operating parameters are identified and the typical modes of deformation that may occur during the process are fully characterized. In contrast to metals, there is no research work and no practical design rules in the specialized literature concerning the cold heading of polymer parts. This paper is concerned with the abovementioned lack of knowledge and is a contribution toward the application of cold heading to polymers. The experimental research work makes use of polyvinyl chloride (PVC) and the overall findings are interpreted in the light of an innovative extension of the flow formulation that is capable of modeling cold forming of pressure-sensitive materials under a nonassociated flow rule. Emphasis is placed on the deformation mechanics of cold heading applied to PVC and on the influence of the major operating parameters on the overall formability limits of the process. Results show that cold heading of PVC can be successfully utilized for producing upset forged parts.