Rotary draw bending of rectangular tubes using a novel parallelepiped elastic mandrel

Rotary draw bending is usually applied to round tubes, since their axisymmetric cross section helps reduce any type of distortion. In the present paper, we investigate rotary draw bending of rectangular tubes employing a novel elastic parallelepiped mandrel. For this purpose, tubes, manufactured by cold forming flat rolled sheets of steel S235JR into rectangular tubular shapes and electric resistance welded into solid wall tubing, were bent, both the “hard way” and the “easy way,” to form a nominal angle of 90°. A finite element (FE) model was developed to perform the process simulation based on an explicit dynamic time integration scheme using the commercial code ABAQUS. The FE outcomes have been validated by comparison with experimental results. Specifically, a coordinate measuring machine was used to determine the degree of bend as well as the radius, the profile, and the wall thickness of the bent sections. The obtained results showed the capability of the FE modeling to predict the material deformation process. Implementing the stiffness of the welding seam into the FE model of the tube dramatically increases the accuracy of the numerical simulations. The validated model is adopted for investigating the effect of mandrel position, clearance, and friction and how they can be set to minimize the tube distortions.