Title: Pre-strain effect on springback of 2D draw bending

Authors: Pedro D. Barros; M.C. Oliveira; J.L. Alves; L.F. Menezes

Addresses: Center of Mechanical Engineering, Department of Mechanical Engineering, University of Coimbra, Pólo II, Rua Luís Reis Santos, Pinhal de Marrocos, 3030-788 Coimbra, Portugal ' Center of Mechanical Engineering, Department of Mechanical Engineering, University of Coimbra, Pólo II, Rua Luís Reis Santos, Pinhal de Marrocos, 3030-788 Coimbra, Portugal ' Center for Mechanical and Materials Technologies, School of Engineering, University of Minho, Campus of Azurém, 4800-058, Guimarães, Portugal ' Center of Mechanical Engineering, Department of Mechanical Engineering, University of Coimbra, Pólo II, Rua Luís Reis Santos, Pinhal de Marrocos, 3030-788 Coimbra, Portugal

Abstract: This work focuses on the BENCHMARK 4 - pre-strain effect on springback of 2-D draw bending, proposed under the NUMISHEET 2011 conference (Huh et al., 2011), where the deep drawing of a U-rail is performed considering the same base material, submitted or not to an 8% tensile pre-strain. A DP780 steel with a thickness of 1.4 mm is studied. The analysis considers all the results reported in Huh et al. (2011) and the ones obtained using DD3IMP. Experimental and numerical results show that the pre-strain leads to a springback increase, showing the influence of the yield stress to elastic modulus ratio. Indeed, the elastic modulus during unloading seems to be as important as the adopted hardening model, being the contribution of the yield criterion smaller. The results accuracy seems to depend more on the strategy adopted to determine the material constitutive parameters than on the selected constitutive model.

Keywords: springback; finite element analysis; FEA; tensile pre-strain; DP780; elastic stiffness degradation; 2D draw bending; deep drawing; U-rails; yield stress; elastic modulus ratio; hardening model; material constitutive parameters.

DOI: 10.1504/IJMATEI.2013.054395

International Journal of Materials Engineering Innovation, 2013 Vol.4 No.2, pp.187 - 211

Published online: 06 Jun 2013 *

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