Effects of process parameters on wrinkling of thin-walled circular tube under rotary draw bending

Process parameters, such as clearance, friction, boosting displacement, bending velocity, and centerline radius/tube diameter ratio, have a significant and complicated influence on wrinkling of circular tubes during rotary draw bending process. To explore the effects of these parameters on the wrinkling, a 3D elastic–plastic finite element (FE) model based on eta/DYNAFORM has been built and validated by experiments. Then, relevant simulation and analysis of the process have been performed. The results show that: (1) the wrinkling increases with the accretion of the clearance. A reasonable clearance of mold groove (less than 0.2 mm) can alleviate the severity of the wrinkling; (2) when the boosting velocity of the pressure die is larger than or equal to the linear velocity of the bend die in the X-axis direction, the wrinkling relieves as the friction between the pressure die and the tube decreases; conversely, when the boosting velocity is smaller than the linear velocity, the wrinkling reduces with the increase of the friction between the two contacted components; (3) the wrinkling is negatively correlated with the centerline radius/tube diameter ratio and positively correlated with the bending velocity of the bend die; and (4) the boosting displacement of the pressure die dominates the direction of frictional force exerted by the pressure die in the bending process. The wrinkling tendency becomes more obvious as the displacement increases.