Abstract: The NC thin-walled tube bending process is multiple-factor-coupled and wrinkling often occur in the process. A numerical met hod is put forward to predict the wrinkling onset based on the energy method and FEM. Att he same time, the influences of forming parameters, such as bending radius, relative tube radius, material properties, forming speed and so on, on the wrinkling initiation are also researched. T he results indicate that the bendingr adius, the relative tube diameter, the extension of mandrel, the hardening factor of material and friction are themain factors determining the wrinkling onset in the process, while t he str ength coefficient of material and formingspeed only have little effect. T hese results provide guidance for the optimization of the forming parameters in tubebending.

Key words: wrinkling, forming parameters, energy method, thin-walled tube, NC bending