Algorithm for the quantitative description of freeform bend tubes produced by the three-roll-push-bending process

Three-roll-push-bending (TRPB) is an innovative and flexible freeform bending process for the manufacturing of tube geometries with a continuous distribution of curvature along the bending line. The shaping is done kinematically, which means that the bending line is defined solely by the defined movement of the bending tools. Measurements of the resulting curvature have shown a characteristic oscillating transition zone over an extensive length of the part until a constant curvature is reached. The quantitative description of the transition zone and typical bending characteristics, such as radius of curvature and bending angle, is only possible to a limited extent using the common measurement approach. This paper presents an algorithm, which allows the determination of typical bending characteristics and the quantitative description of transition zones along the curvature distribution. For specimen components the results provided by this method are compared to those provided by a common method for the examination of bending radii. The algorithm forms the basis for investigating the influence of machine, tool and semi-finished parameters on the transition zone at the bending section.