This content is not included in
your SAE MOBILUS subscription, or you are not logged in.
The Effective Unloading Modulus for Automotive Sheet Steels
Technical Paper
2006-01-0146
ISSN: 0148-7191, e-ISSN: 2688-3627
Annotation ability available
Sector:
Language:
English
Abstract
In stamping advanced high strength steels (AHSS), the deviations from desired part geometry caused by springback from a radius, curl, twist, and bow are major impediments to successfully producing AHSS parts. In general, the conventional elastic modulus is used to quantify the strain that occurs on unloading. This unloading strain causes deviations from desired part geometry. Considerable evidence in the literature indicates that for tensile testing, the conventional elastic modulus does not accurately describe the unloading strain. The present study uses new data and results from the literature to examine the average slope of tensile stress strain curves on unloading. This slope is termed the effective unloading modulus. The results from this study quantitatively describe how the effective unloading modulus decreases with increasing strength, prestrain, and unloading time. Calculations are also included that describe the relative contributions of: 1) dislocation related phenomena, 2) thermal contraction, and 3) conventional elasticity. The effective unloading modulus can be used as an engineering estimate to replace the conventional elastic modulus in mechanics equations that predict springback from a radius, curl, twist, and bow. The results from this study also indicate a need for evaluating the effective unloading modulus for other strain paths. Determination of the effective unloading modulus for other strain paths is needed before quantitative relationships suitable for finite element analysis codes can be precisely specified.
Recommended Content
Authors
Citation
Levy, B., Van Tyne, C., Moon, Y., and Mikalsen, C., "The Effective Unloading Modulus for Automotive Sheet Steels," SAE Technical Paper 2006-01-0146, 2006, https://doi.org/10.4271/2006-01-0146.Also In
References
- Zener C. Elasticity and Anelasticity of Metals University of Chicago Press Chicago, IL, USA 1948
- Blaimschin, M. Radlmayr, K. Pilcher, A. Till, E. Stiaszny, P. “Bake Hardening Effect in Components” Proceedings of the 19th Biennial Congress of the IDDRG Egger, Hungary 1996
- Cleveland R. Ghosh, A. K. “Inelastic Effects n Springback in Metals” Sheet Metal Forming for the New Millennium, Proceedings of the 21st Biennial Congress of the IDDRG Dearborn, MI, USA 2000 141 155
- Cleveland R. M Ghosh, A. K “Inelastic Effects on Springback in Metals” International Journal of Plasticity 18 2002 769 785
- Luo L. Ghosh, A. K. “Elastic and Inelastic Recovery after Plastic Deformation of DQSK Steel Sheet” Journal of Engineering Materials and Technology 125 2003 237 246
- Zhu H. Huang L. Wong C. “Unloading Modulus on Springback in Steels” SAE Technical Paper 2004-01-1050 Oetjens T. J. Stoughton T. B. Saran M. J. Pan J. Liu S.-D. Sheet/Hydro/Gas Forming Technology and Modeling, SP-1840 Society of Automotive Engineers Warrendale, PA, USA 2004 87 91
- Sriram S. Wong C. Huang M. Yan B. Urban D. “Formability Characterization of a New Generation of High Strength Steels” American Iron and Steel Institute Technology Roadmap Program Office Pittsburgh, PA, USA 2003
- Thibaud S. Gelin, J.-C. “Influence of Initial and Induced Hardening on the Formability in Sheet Metal Forming” International Journal of Forming Processes 5 2002 505 520
- Mould P. R. Johnson, T. E. “Rapid Assessment of Drawability of Cold-Rolled Low-Carbon Steel Sheets” Sheet Metal Industries 50 1973 328 330 332 348
- Krasowsky A. Walde T. Schmitt W. Andrieux F. Riedel H. Kulp S. Dröder K. “Springback Simulation in Sheet Metal Forming Using Material Formulation Based on Combined Isotropic-Kinematic Hardening with Elasto-Plastic Anisotopy” Proceedings of IDDRG International Deep Drawing Research Group 2004 Conference Kergen R. Keßler L. Langerrak N. Lenze F.-J. Janssen E. Steinbeck G. Verlag Stahleisen Düsseldorf, Germany 2004 104 113
- Hilditch T. B. Matlock D. K. Levy B. S. Siekirk J. F. “Experimental Evaluation of Curl and Tensile Properties of Advanced High Strength Sheet Steels” SAE Technical Paper 2004-01-1045 Oetjens T. J. Stoughton T. B. Saran M. J. Pan J. Liu S.-D. Sheet/Hydro/Gas Forming Technology and Modeling, SP-1840 Society of Automotive Engineers Warrendale, PA, USA 2004 63 72
- Sriram S. May 2005
- Benito, J. A. Manero, J. M. Jorba, J. Roca, A. “Change of Young’s Modulus of Cold-Deformed Pure Iron in a Tensile Test” Metallurgical and Materials Transactions A 36 2005 3317 3324
- Dieter G. Mechanical Metallurgy 3rd edition McGraw Hill New York, NY, USA 1986 525