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TY  - THES
AU  - Müller, Clemens David
TI  - Elektrische Widerstandserwärmung von Blechwerkstoffen zur Steigerung der Umformbarkeit; 1. Auflage
VL  - 2023,27
PB  - RWTH Aachen University
VL  - Dissertation
CY  - Aachen
M1  - RWTH-2023-09766
SN  - 978-3-98555-175-0
T2  - Ergebnisse aus der Produktionstechnik
SP  - 1 Online-Ressource : Illustrationen, Diagramme
PY  - 2023
N1  - Druckausgabe: 2023. - Auch veröffentlicht auf dem Publikationsserver der RWTH Aachen University
N1  - Dissertation, RWTH Aachen University, 2023
AB  - The increased utilization of high strength steel sheets in mobile applications as well as the use of electric drives are crucial measures for the reduction of emissions. The material characteristics lead to limited degrees of deformation and geometries of the parts. To extend these limitations, electrical resistance heating for processing sheet metals is developed in this thesis, taking high strength steel sheets and metallic bipolar plates for fuel cells as examples. Hot forming is established as a technology for the processing of sheet metals with high requirements for the degree of deformation. According to the current state of the art, heating is associated with long process durations. There is a clear need for innovative technologies for the rapid and energy-efficient heating of sheet metals, which can be integrated into high volume production processes for economic manufacturing. The general potential of electrical resistance heating to heat sheet metals locally in a short process time is analyzed in analytical calculations and numerical simulations. Results show, that depending on the electrical current, sheets can be heated up to their melting temperature in less than a second. This proves the general suitability of the technology. For the experimental validation, a lab test bench is developed on the basis of the predicted process parameters from the simulation. This test bench enables the coupled thermal-mechanical processing. By optical inspection methods, the optimization of cutting surfaces and the extension of the formable aspect ratio in flange forming is successfully demonstrated. After the proof of concept with the lab test bench, the technology of electrical resistance heating is integrated into a module of a progressive die tool. Higher degrees of deformation are confirmed with the local heating in flange forming under near-series production conditions. Micro hardness measurements and metallographic analysis give proof that the process can be developed in a way, that no increase of hardness is caused by the heating and subsequent cooling during tool contact. For further evaluation of the heating technology, electrical resistance heating is transferred to additional materials, sheet thicknesses and heating geometries in form of metallic bipolar plates for fuel cell applications. Larger channel depths and optimized geometrical ratios in the flow field allow improved system efficiency. For the validation of the suitability of this heating technology, a lab test bench is developed, which combines a heating unit with a press and successfully demonstrates the feasibility. For single-stage hot forming as well as two-stage forming with intermediate annealing, an increase in the formable channel depth without cracks is realized for stainless steel plates. Both research questions that are raised about the optimized cutting quality and enlarged degree of deformation for high strength steels as well as deeper flow field channels in metallic bipolar plates are successfully answered with the presented results in this thesis.
LB  - PUB:(DE-HGF)11 ; PUB:(DE-HGF)3
DO  - DOI:10.18154/RWTH-2023-09766
UR  - https://publications.rwth-aachen.de/record/971675
ER  -