A Simulative Method for Studying the Bonding Condition of Friction Stir Extrusion

In the manufacturing industry, the problem related to the management of metal waste is of considerable importance, since it is produced in large quantities during mechanical processing. However, its recovery is not always a simple task, especially with regard to the metal cutting processes. In fact, due to the presence of surface oxide and contaminating oily residues, the recovery process of these components is often very expensive and polluting. This problem can be solved with the FSE process, patented in 1993 by The Welding Institute. The FSE can be counted among the main innovative processing techniques developed in Industry 4.0, as it involves only metal scraps coming from the machining processes as starting material, without providing for their preliminary re-melting in a billet form, and it uses only the heat generated by the friction between the tool and the metal. Since FSE is a quite recent process, the development of simulative models is useful for understanding its basic mechanisms. The objective of this research is to analyze if and how the bonding phenomena occour considering both the thermal and the stress conditions involved and generated by the process parameters. As a result, FEM analysis proved to be a valid tool to correctly forecast if bonding phenomena really take place and how process parameters affect the bonding quality. Moreover, it was possible to confirm that the Piwnik and Plata bonding model is a good criterion for predicting the effects of this technology.