New Technique to Model the Effect of Intermediate Induction Heat Treatment (IIHT) in Pre-Strained Aluminium Sheets

Abstract:

This paper presents a new technique to model the effect of intermediate induction heat treatment (IIHT) on pre-strained aluminium sheets, predominantly AA5182. IIHT is a heat treatment technique carried out between two conventional cold forming steps, which eventually lead to enhanced formability of aluminium alloys. The aim of IIHT is to alleviate the strain hardening of the material which is introduced in the first cold forming step and there by reducing the yield limit and increasing the hardening modulus for subsequent forming steps. As a result, a remarkable increase in formability can be achieved in the subsequent forming steps at room temperature. The scientific aspect of the IIHT process is demonstrated by defined pre-strained tensile test specimens at different object temperatures to establish a process window. To accurately model the effect of IHTT in simulations, it is necessary for the material model to consider the plastic recovery that the material undergoes during heat treatment. To this effect, material model Mat133 (Barlat_YLD2000) in LS-Dyna has been enhanced to account for the effect of intermediate heat treatment. The numerical simulation is carried out in four steps namely pre-forming, springback simulation to account for residual stresses, thermo-mechanical coupled simulation for heat treatment, and final forming with enhanced material model. To validate this model, experiments have been carried out on a simple cross-die deep drawn cup and compared with simulation results.

• Periodical: Key Engineering Materials (Volumes 504-506)
• Pages: 1073-1078
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.504-506.1073
• Online since: February 2012
• Authors: Rajarajan Govindarajan, Martin Zubeil, Kathleen Siefert, Tobias Kleeh, David Lorenz, Thomas Borrvall, Christophe Ageorges
• Keywords: Aluminium Alloy, Finite Element Method (FEM), Formability, Heat Assisted Forming, Heat Treatment, Material Model

References

[1] H.E. Friedrich, P. Treffinger, G. Kopp, H. Knäbel, Werkstoffe und Bauweisen ermöglichen neue Fahrzeugkonzepte, Forschung für das Auto von Morgen, Springer Verlag, Berlin (2008) 302-346.

DOI: 10.1007/978-3-540-74151-0_9

[2] Information on http://aluminium.matter.org.uk

[3] U. Vogt, Seriennahe Auslegung von Aluminium Tailored Heat Treated Blanks. Dissertation, Chair of Manufacturing Technology, University of Erlangen- Nuremberg, 2009.

[4] M. Hogg, Herstellung und Umformung lokal wärmebehandelter Platinen. Dissertation, Institute for Metal Forming Technology of the University of Stuttgart, 2006.

[5] D. Schmoeckel, Temperaturgeführte Prozessteuerung beim Umformen von Aluminiumblechen. EFB/AiF Forschungsbericht 55, Hanover, 1994.

[6] M. Geiger, M. Merklein, U. Vogt, Aluminum tailored heat treated blanks, Production Engineering Research and Development 11740 (2009) 401-410.

DOI: 10.1007/s11740-009-0179-8

[7] R. Govindarajan, M. Zubeil, K. Siefert, Dr. C. Ageorges, Prof. Dr-.Ing. K. Roll, Simulation of heat assisted forming of commercial aluminium alloy AA5182, Shemet, Leuven, (2011) 675-682.

DOI: 10.4028/www.scientific.net/kem.473.675

[8] K. Siefert, M. Merklein, W. Nester, M. Grünbaum, Enhancement of forming limits of aluminum alloys using an intermediate heat treatment. In: Proc. Of Conference Advances of materials and processing technology, Paris, (2010) in press.

DOI: 10.1063/1.3552469

[9] J.O. Hallquist, Recent Developements in LS-DYNA, LS-DYNA Anwenderforum, Filderstadt, (2011)

[10] D. Lorenz, Prozessauslegung in der Warmumformung durch thermomechanisch gekoppelte Simulation, M. Merklein, 6. Erlanger Workshop Warmblechumformung, Meisenbach, Bamberg, (2011)

[11] R. Greze, P.Y. Manach, H.Laurent, S.Thuillier, L.F. Menezes, Influence of the temperature on residual stresses and springback effect in an aluminium alloy, International Journal of Mechanical Sciences 52 (2010), 1094

DOI: 10.1016/j.ijmecsci.2010.04.008