Determination of Forming Limit Diagrams for Thin Foil Materials Based on Scaled Nakajima Test

Abstract:

For a better process understanding of micro deep drawing processes and reliable prediction of component failure in FE simulations, it requires the most accurate knowledge of actual material behaviour. However, it is not sufficient to describe material failure for a multi axial stress state in deep drawing using a mechanical parameter as the elongation from tensile test. A forming limit diagram and a forming limit curve are more suited to describe the limit of formability under deep drawing stress state conditions. Methods like hydraulic or pneumatic bulge tests are available to determine forming limit curves even for thin metal foil materials. Nevertheless, using these methods only positive minor strains can be achieved. Especially for a deep drawing process negative minor strains and the left side of a forming limit diagram are more important. Therefore, in this study, experiments based on scaled Nakazima tests were performed to determine complete forming limit diagrams for different foil materials with a thickness range of 20 µm to 25 µm. Scaling the test setup improves the handling of thin specimens. Results with a higher local resolution and the specimens’ size is much closer to the actual size of a micro deep drawn component. Using this testing method forming limit diagrams for the materials Al99.5, E-Cu58, stainless austenitic nickel-chromium steel X5CrNi18-10 (1.4301 / AISI 304), all produced by rolling, and an Al-Zr-foil, produced by a PVD sputtering process, were determined for the micro range.

• Periodical: Applied Mechanics and Materials (Volume 794)
• Pages: 190-198
• DOI: https://doi.org/10.4028/www.scientific.net/AMM.794.190
• Online since: October 2015
• Authors: Stefan Veenaas*, Gerrit Behrens, Konstantin Kröger, Frank Vollertsen
• Keywords: Forming Limit Diagram, Material, Micro Forming

References

[1] Keeler, S. P.; Engineers, S. of A.: Determination of Forming Limits in Automotive Stampings. Society of Automotive Engineers (1965).

[2] Goodwin, G. M.: Application of Strain Analysis to Sheet Metal Forming Problems in the Press Shop (No. 680093). SAE International Warrendale, PA (1968).

DOI: 10.4271/680093

[3] S. Bruschi, T. Altan, D. Banabic, P.F. Bariani, A. Brosius, J. Cao, A. Ghiotti, M. Khraisheh, M. Merklein, A.E. Tekkaya: Testing and modelling of material behavior and formability in sheet metal forming. CIRP Annals – Manufacturing Technology 63 (2014).

DOI: 10.1016/j.cirp.2014.05.005

[4] Banabic, D.: Sheet metal forming processes: constitutive modelling and numerical simulation. Springer Berlin, New York (2008).

[5] Nakajima, K.; Kikuma, T.; Hasuka, T.: Study on the formability of steel sheets. Yawata Technical Report, 284 (1968) 141 – 154.

[6] Hasek, V.; Lange, K.: Untersuchung und theoretische Beschreibung wichtiger Einflußgrößen auf das Grenzformänderungsschaubild - Teil 1. Blech, Rohre, Profile 25, 5 (1972) 213 – 220.

[7] ISO 12004-2: Metallic materials – sheet and strip – determination of forming limit curves – Part 2: determination of forming limit curves in the laboratory (2008).

DOI: 10.3403/30150423u

[8] Vollertsen, F., Biermann, D., Hansen, H.N., Jawahir, I.S., Kuzman, K., 2009. Size effects in manufacturing of metallic components, CIRP Annals - Manufacturing Technology, Vol. 58/2, pp.566-587.

DOI: 10.1016/j.cirp.2009.09.002

[9] Diehl, A.; Engel, U.: Grenzformänderung metallischer Folien *. Werkstattstechnik Online, 11/12 (2008) 982 – 987.

DOI: 10.37544/1436-4980-2008-11-12-982

[10] Merklein, M.; Kuppert, A.; Geiger, M.: Time dependent determination of forming limit diagrams. CIRP Annals - Manufacturing Technology 59, 1 (2010) 295 – 298.

DOI: 10.1016/j.cirp.2010.03.001

[11] Diehl, A.; Vierzigmann, U.; Engel, U.: Characterisation of the mechanical behaviour and the forming limits of metal foils using a pneumatic bulge test. International Journal of Material Forming 2, S1 (2009) 605 – 608.

DOI: 10.1007/s12289-009-0608-4

[12] Hu, Z.; Wielage, H.; Vollertsen, F.: Forming Behavior of Thin Foils. 14th International Conference on Sheet Metal. Trans Tech Publications Zürich- Durnten (2011) 1008 – 1015.

DOI: 10.4028/www.scientific.net/kem.473.1008

[13] Kim, J., Hoffmann, H.; Golle, M.; Golle, R.: Untersuchungen zum Werkstoffverhalten von sehr dünnen Kupferblechen. In: Grösseneinflüsse bei Fertigungsprozessen Beiträge zum Abschlusskolloquium des SPP 1138, Bonn, 11. - 12. Februar 2009. Hrsg.: F. Vollertsen, BIAS-Verlag Bremen (2009).

[14] Marciniak, Z.; Duncan, J. L.; Hu, S. J.: Mechanics of sheet metal forming. Butterworth-Heinemann Oxford; Boston (2002).