Warping and springback reduction in bending of U-profiles through partial heating over the cross-section

Abstract

Bending of profiles is challenging due to the high stiffness and possible deformations in the process. Especially bending of profiles with asymmetric cross-section regarding the force initiation axis leads to unwanted warping of the bent profile. This warping results from the position difference between the force initiation axis and the shear center, implying torsion moments on the profile. To prevent profile warping the use of shape-bound tools or a change of the force initiation axis position are common practices, though these methods reduce the flexibility of the process. A new method to prevent profile warping during bending is the use of partial, cross-sectional heating. Due to thermal softening in one profile area a quasi-symmetric bending case is achieved, which changes the position of the stress-free fiber and thus reduces the torsion moment. In this work, the warping and springback behavior of partially heated U-profiles consisting of S500MC steel after a three-roll push bending process is investigated using experimental methods. Through partial heating of one profile area to up to 600°C, a warping reduction of 83 % and a springback reduction of 69 % were achieved.