Naumann D, Sawodny A, Schmid H, Merklein M (2025)
Publication Type: Journal article
Publication year: 2025
Book Volume: 3104
Pages Range: 012006
Issue: 1
DOI: 10.1088/1742-6596/3104/1/012006
Determining the forming limit is a crucial factor in the design phase of deep drawing processes. Forming in established characterisation tests to determine the forming limit and fracture (F) strain is performed at a constant punch speed, but not at a constant strain rate. As a result, the strain rate in flat specimens, as well as in Nakajima specimens at the pole, show a strong time-dependent increase from the beginning of necking. For strain rate sensitive materials, this can lead to a deviating forming limit or fracture strain. By controlling the forming process to a constant strain rate in the main deformation direction, a direct influence can be exerted on the temporal evolution of the strains. Thus, the acceleration of the major strains towards the end of the deformation can be compensated. This extends the necking phase. Especially for high-strength steels and aluminium alloys, which provide a less ductile behaviour with a short necking phase and sudden cracking, this can have an advantage for a precise analysis of failure. Accordingly, a 5182 aluminium alloy and a dual-phase steel DP600 are investigated in Nakajima and flat tensile tests at a strain rate of 0.004 1/s with regard to their failure behaviour with and without strain rate control. Finally, the determined failure data is transferred into a numerical simulation of a deep drawing process and the influence of the different failure characterization methods on the prediction of the simulation is evaluated. The strain rate evolution was improved for both testing setups in terms of meeting the nominal strain rate. Also, an increased fracture limit was identified by utilising optical strain rate control for both materials.
APA:
Naumann, D., Sawodny, A., Schmid, H., & Merklein, M. (2025). Forming limit determination of sheet metals at constant true strain rates. Journal of Physics: Conference Series, 3104, 012006. https://doi.org/10.1088/1742-6596/3104/1/012006
MLA:
Naumann, David, et al. "Forming limit determination of sheet metals at constant true strain rates." Journal of Physics: Conference Series 3104 (2025): 012006.
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