Influence of a single bend in the bumping process of large radius air bending

Bump bending or step bending is a forming technique that allows making large radius bends in a sheet metal part by means of a series of bends performed close to each other. The bump bending process has been studied by means of both an experimental campaign and finite element analysis. High-strength steel Weldox 1300 and a punch of radius 30 mm have been used. The finite element calculations have been performed with Abaqus using the solid formulation and Implicit/Explicit solvers. The results of the finite element analysis have been validated experimentally by monitoring the bending process using a camera system aligned with the bending line. Experiments were performed on a press-brake with a capacity of 50 metric tons. Deflections of a sheet during and after bending have been measured using the images recorded by the camera. In order to investigate the influence of a new bend on a previously formed bend, experiments have been performed with different distances between two consecutive bends. Based on the experiments, the size of the affected zone for the bend has been measured. The dependence of the distance between two consecutive bends on the resulting global bending angle has been studied. Moreover, the influence of the bump distance on the springback has been investigated.status: publishe