Segmentation Method for Bending Tools – Fundamental Investigation of Profile Forming by Segmented Tools

In bending processes with generic tools (e.g., three-roll push bending), the part geometry is a result of the free tool kinematics. In contrast, processes with geometry-specific tools (e.g., rotary draw bending) require a specialized tool geometry to form a dedicated part geometry. To make them more flexible while maintaining their advantages of dimensional accuracy and process controllability, adjustable tools are needed. Inspired by multi forming techniques, one possible approach is to segment the conventionally closed tool surfaces and adjust them in-process. For the design of the segmentation in terms of segment geometry and size, as well as in terms of tolerable spaces, a deep understanding of the deformation mechanisms of the workpiece in contact with segmented surfaces is crucial. As a first step toward this goal, this work presents lateral indentation tests of circular and square steel and aluminum tubes by segments and segmented surfaces. Based on these tests, finite element (FE) models are validated and show a good correlation with the experimental tests in terms of force-displacement curves and part geometries. Finally, the FE-model is used to perform a parameter study to investigate the deformation behavior of tubes subjected to lateral loading by segmented surfaces in dependency of different tube wall thicknesses as well as of different segment spacings. It is outlined, that the segmentation of forming tools is generally possible with negligible impact on the process when choosing a suitable surface topology.