To meet the requirements of energy savings and CO2 emission reductions for transportation vehicles great efforts have been made over the years to reduce the weight of vehicles by replacing the current heavy metal structures with light alloys, such as aluminium and magnesium alloys. But the common problems for the light alloys are brittle and difficult to form to complex-shaped structural panel components. Thus hot stamping techniques have been developed in recent years to enable high strength alloys to be stamped into complex-shaped components in one operation, such as, “HFQ(R)-Technology” for high strength aluminium alloys [1].

In this presentation, thermal-mechanical test set-up to meet the real production conditions will be outlined first. The temperature profile control [2] and strain field measurements within the gauge length of specimens, together with the spatio-temporal method for determining necking and fracture strains of sheet metals [3], will also be presented. Special attentions will be paid to the development of biaxial test facilities [4] for generating forming limit diagrams (FLD) and fracture forming limit diagrams (FFLD) [5]. At the end of the presentation, the creation of unified viscoplastic constitutive equations for hot stamping process modelling will be presented [6].

REFERENCES

1. M. S. Mohamed, A. D. Foster, J. Lin, D. Balint and T. A. Dean (2012). Investigation of deformation and failure features in hot stamping of AA6082: Experimentation and modelling, Int. J. of Machine Tools and Manuf., 53, 27-38.
2. M. Ganapathy, N. Li, J. Lin, M. Abspoel and D. Bhattacharjee (2018). A Novel Grip Design for High-Accuracy Thermo-Mechanical Tensile Testing of Boron Steel under Hot Stamping Conditions, Experimental Mechanics, 58, 243-258.
3. R. Zhang, Z. Shao, Z. Shi, T.A. Dean and J. Lin+, 2021, A novel spatio-temporal method for determining necking and fracture strains of sheet metals, Int. J. of Mechanical Sciences, 189 (2021), 105977. https://doi.org/10.1016/j.ijmecsci.2020.105977
4. Z. Shao, N. Li, J. Lin and T.A. Dean (2016). Development of a New Biaxial Testing System for Generating Forming Limit Diagrams for Sheet Metals Under Hot Stamping Conditions, Experimental Mechanics, 56, 1489-1500.
5. R. Zhang, Z. Shi, V.A. Yardley, J. Lin, 2022, Experimental studies of necking and fracture limits of boron steel sheet under hot stamping conditions, J. of Materials Proc. Tech., 302 (2022) 117481, https://doi.org/10.1016/j.jmatprotec.2021.117481
6. J. Lin, M Mohamed, D. Balint and T.A. Dean (2014) The Development of CDM-based theories for predicting FLD for hot stamping applications, Int. J. of Damage Mechanics. 23, 707 - 724.