Investigation of High-Strength Steel Component Subjected to Stretch-Bending: Effect of Forming History

Abstract:

The behaviour of a closed top-hat section made of Dogal 800 DP subjected to stretch-bending is studied both experimentally and numerically. The top-hat section was made by forming of a sheet using a Flexform^TM fluid cell press and closed by a sheet using welding. Experiments were performed in a stretch-bending rig in two stages. During the first stage the profiles were bent under a constant horizontal stretch force. In the second stage the profiles were stretched back from the bent position. The force-displacement relations of the actuators involved in the experiments were recorded and the initiation and development of fracture during the stretching process after unloading of the die was detected by cameras. A finite element code was applied to model the forming operation and the stretch bending experiments including the unloading of the die and subsequent stretching of the profile. The elastic-plastic material model with calibrated parameters was adopted from previous studies on Dogal 800 DP, including the Cockcroft-Latham fracture criterion to detect initiation of fracture. The history variables were mapped from the forming model to the stretch-bending model. The forming process was simplified as a hydroforming operation and some deviations were observed regarding the thinning of the sheet between the model and the real process. The model of the stretch-bending experiment was able to capture the force-displacement relation during the first stage with reasonable accuracy. Some deviations between the experimental and simulated force-displacement relations were observed during the second stage, i.e. the stretch-back operation, but the initiation of fracture was well captured.

• Periodical: Key Engineering Materials (Volumes 611-612)
• Pages: 1702-1709
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.611-612.1702
• Online since: May 2014
• Authors: Ørjan Fyllingen*, Magnus Langseth, Odd Sture Hopperstad
• Keywords: Dual Phase Steel, Finite Element Modeling (FEM), Forming Operation, Stretch-Bending, Top-Hat Section

References

[1] V. Tarigopula , O.S. Hopperstad, M. Langseth, A.H. Clausen, Elastic-plastic behaviour of dual-phase, high-strength steel under strain-path changes, European Journal of Mechanics –A/solids 27: 5 (2008) 764-782.

DOI: 10.1016/j.euromechsol.2008.01.002

[2] V. Tarigopula , O.S. Hopperstad, M. Langseth, A.H. Clausen, An evaluation of a combined isotropic-kinematic hardening model for representation of complex strain-path changes in dual-phase steel, European Journal of Mechanics –A/solids 28: 4 (2009).

DOI: 10.1016/j.euromechsol.2008.12.004

[3] V. Tarigopula , O.S. Hopperstad, M. Langseth, A.H. Clausen, F. Hild, O. -G. Lademo, M. Eriksson, A Study of Large Plastic Deformations in Dual Phase Steel Using Digital Image Correlation and FE Analysis, Experimental Mechanics 48 (2008) 181–196.

DOI: 10.1007/s11340-007-9066-4

[4] V. Tarigopula , O.S. Hopperstad, M. Langseth, A.H. Clausen, F. Hild, A study of localisation in dual-phase high-strength steels under dynamic loading using digital image correlation and FE analysis, International Journal of Solids and Structures 45: 2 (2008).

DOI: 10.1016/j.ijsolstr.2007.08.021

[5] FlexformTM Fluid Cell Press, http: /www. avure. com/smf/products/default. asp (accessed 15th of February 2012).

[6] J.L. Chaboche, On some modifications of kinematic hardening to improve the description of ratcheting effects, Int. J. Plasticity 7 (1991) 661-678.

DOI: 10.1016/0749-6419(91)90050-9

[7] R.W. Lemaitre, J.L. Chaboche, Mechanics of Solids Materials, Cambridge University Press, (1990).

[8] M.G. Cockcroft, D.J. Latham, Ductility and the workability of metals, J. Inst. Met. 96 (1968) 33-39.

[9] LS-DYNA keywords user's manual, volume 1, Livermore Software Technology, (2007).

[10] R.W. Logan, W.F. Hosford, Upper-Bound Anisotropic Yield Locus Calculations Assuming <1 1 1>-Pencil Glide, Int J Mech Sci 22 (1980) 419-430.

DOI: 10.1016/0020-7403(80)90011-9