@phdthesis{BesongBesong2024, author = {Besong Besong, Lemopi Isidore}, title = {Development of novel hole-flanging processes}, doi = {10.26127/BTUOpen-6859}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-68597}, school = {BTU Cottbus - Senftenberg}, year = {2024}, abstract = {Flanges are essential elements in sheet metal parts, where they perform important functions such as increasing structural stiffness, serve as bearing seats and positioning aids. Currently, flanges are mainly formed by the conventional hole-flanging process, which uses dedicated dies and punches. The limitations of conventional hole-flanging include the high cost involved in die design and manufacture, poor accessibility to form flanges in some complicated dies, and low formability. High-speed tool rotation is introduced in hole-flanging processes to increase the process temperature and forming limit of hard-to-form materials. This is done using paddle-shaped tools and spherical punches in existing production lines. In addition, strategies are explored to enhance the geometrical accuracy in robot-based hole-flanging by single-point incremental forming (SPIF). This thesis investigates new hole-flanging process variants by using experiments and finite element (FE) analysis. Empirical material models are used to study the effects of the process parameters on flange shape, forming limits, process temperature, and forming mechanics. The process formability is highest in hole-flanging with punch rotation and reduces for paddle forming and hole-flanging by SPIF. The least formability is observed in conventional hole-flanging. High-speed tool rotation and tool feeds form flanges with high formability. Surface strain measurements of the flanges show that low-speed tool rotation combined with high tool feeds favor crack formation. Tensile tests revealed that the material's formability increases with temperature and strain rate. From FE analyses of the process variants, the deformation in hole-flanging was determined to be mainly because of membrane stretching and bending. Some shear was present in paddle forming and SPIF. Based on FE analyses and experiments, the temperature and strain rate are determined to be the main parameters that account for the difference in process formability. Hole-flanging by SPIF is conducted on a robot manipulator to enhance geometrical accuracy. New tool paths are explored to prevent flange conicity. A parametric study is conducted to determine the process's feasibility. The stiffness of a robot is compensated to achieve the target flange geometry.}, subject = {Bohrungsflanschen; Hole-flanging; Paddle forming; Robot incremental forming; Process development; Deformation analysis; Schaufelumformung; Inkrementelle Roboterumformung; Verformungsanalyse; Prozessentwicklung; Kragenziehen; Flansch; Prozessentwicklung ; Deformation; Blechumformen; Finite-Elemente-Methode}, language = {en} }