Research on the springback of thin-walled tube NC bending based on the numerical simulation of the whole process

The whole process of thin-walled tube NC bending includes three processes: bending tube, retracting mandrel and springback. Based on the numerical simulation of the whole process, the springback mechanism and rule of thin-walled tube NC bending are revealed. During springback, the angle of the bending portion decreases and the radius of the bending portion increases. The springback of the two straight portions is similar to the bending deformation of a projecting beam. The total springback angle considering retracting mandrel is much smaller than that not considering retracting mandrel and the maximum difference between them in the paper is 107.34%. The process of retracting mandrel must be considered to predict accurately the springback of thin-walled tube NC bending. The total springback angle increases linearly with the increase of the bending angle when the bending angle is big. The springback radius can be obtained based on that the length of the neutral layer keeps unchangeable during springback. The length change of the bending portion during springback is usually very small so that it can be neglected when the springback radius is computed. And then the springback radius is independent on the bending angle and the linearly increasing rate of the total springback angle with the increase of the bending angle can be used to compute the springback radius.