An investigation on flaring process of thin-walled tubes using multistage single point incremental forming

The flaring of a thin-walled tube is conventionally carried out by pressing the tube end using dedicated die sets. As an alternative process with the high flexibility and low complexity, in this research, the utilization of single point incremental forming (SPIF), which is the simplest variant of incremental sheet metal forming (ISMF) processes, was assessed and investigated experimentally and numerically for flaring of the tube end. Results predicted by the finite element (FE) model through the commercial code Abaqus/Explicit showed a reasonable agreement with the experimental results. In the present research, the formability in SPIF was compared with that in pressing process and it was concluded that using multistage SPIF, the maximum semi-cone angle achievable before fracture can be improved at least 100%. The results showed that the thickness distribution in the conical flaring of the tube end includes thinning and thickening regions affected by the deformation strategy of multistage SPIF. In this regard, the formability of the tube end and the material deformation were studied under various forming strategies. Finally, for non-axisymmetric flaring of the tube end in the form of a pyramid with the semi-angle of 20° using SPIF, different three-stage forming strategies were designed and successfully implemented. The thickness distribution and the geometric accuracy under designed three-stage strategies were investigated.