Modelling of Instability and Fracture Effects in the Sheet Metal Forming Based on an Extended X-FLC Concept

Abstract:

The industrial necking prediction in sheet metal forming is still based on the Forming Limit Diagram (FLD) as initially proposed by Keeler. The FLD is commonly specified by the Nakajima tests and evaluated with the so called cross section method. Although widely used, the FLC concept has numerous serious limitations. In the paper the influences of bending on the FLC as well as postponed crack limits will be discussed. Both criteria will be combined to an extended FLC concept (X-FLC). The new concept demonstrates that the Nakajima tests are not only appropriate for the evaluation of the necking instability, but also for the detection of the real crack strains. For the evaluation of the crack strains, a new local thinning method is proposed and tested for special 6xxx Al-alloys.

• Periodical: Key Engineering Materials (Volume 725)
• Pages: 15-32
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.725.15
• Online since: December 2016
• Authors: Pavel Hora*, Bekim Berisha, Maysam Gorji, Holger Hippke
• Keywords: Extended X-FLC, Nakajima Test, Sheet Metal Forming

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