Effect of material properties on deformation behavior in incremental tube-burring process using a bar tool

To enhance the formability, product quality and process flexibility of large branched tubing, a new incremental burring process for manufacturing branched tubing without welding has been developed. A highly significant processing path using a bar tool is proposed that is based on the forming characteristics of two conventional forming processes, namely, the rigid plug pullout method and the T-drill method. In this paper, a suitable tooling path and the effect of the tubular material properties on the incremental tube-burring process to achieve a more uniform thickness distribution at the edge of branched tubing has been investigated using a simulation. In the analysis, the tubular material used for branched tubing was the aluminum alloy, A5083-O, with a diameter of 400 mm and wall thickness of 6.0 mm, while an oval hole in the mother tube had a major axis of 360 mm and a minor axis of 194 mm. A bar tool with a diameter of 65 mm was used for the incremental tube-burring method. This burring model was analyzed using an explicit finite element method code. This method consists of three processes: (i) the oval hole is expanded by moving a bar tool keeping vertical tool condition nearby minor axis area, (ii) the oval hole is deformed and flanged-up at major axis by rocking and raising a bar tool, (iii) the oval hole is expanded out and flanged-up to the desired diameter of the branched tubing. The thickness reduction ratio distribution at the edge of branched tubing is influenced by material properties such as the n-value, the transverse anisotropy, and the planar anisotropy. The validity of this simulation model was also verified by comparing with experimental results.