The comparison of two continuum damage mechanics-based material models for formability prediction of AA6082 under hot stamping conditions

Abstract

Abstract. The hot stamping and cold die quenching process has experienced tremendous development in order to obtain shapes of structural components with great complexity in automotive applications. Prediction of the formability of a metal sheet is significant for practical applications of forming components in the automotive industry. Since microstructural evolution in an alloy at elevated temperature has a large effect on formability, continuum damage mechanics (CDM)-based material models can be used to characterise the behaviour of metals when a forming process is conducted at elevated temperatures. In this paper, two sets of unified multi-axial constitutive equations based on material's stress states and strain states, respectively, were calibrated and used to effectively predict the thermo-mechanical response and forming limits of alloys under complex hot stamping conditions. In order to determine and calibrate the two material models, formability tests of AA6082 using a developed novel biaxial testing system were conducted at various temperatures and strain rates under hot stamping conditions. The determined unified constitutive equations from experimental data are presented in this paper. It is found that both of the stress-state based and strain-state based material models can predict the formability of AA6082 under hot stamping conditions. IntroductionThe automotive industry is facing a huge global challenge to reduce fuel consumption and minimise environmental pollution from vehicle emissions. The hot stamping and cold die quenching process has been developed to obtain components with great complexity and high mechanical properties. The control of heating rate, cooling rate, forming speed and metallic sheet temperature is critical for the success of these processes. Formability tests with special tooling and test procedures are usually needed to evaluate the formability of a metal sheet. The forming limit diagram (FLD) is a conventional tool to illustrate the formability of sheet metals. It is very difficult to obtain FLDs of metals under hot stamping and cold die quenching conditions by using conventional methods, since the cooling which occurs prior to deformation and constant deformation temperature, strain rate and strain path are not easy to obtain. A novel formability testing system have been proposed and developed to determine formability of metals experimentally for hot sheet stamping applications [1].Experimentally determination [2] of the FLD of a material is time-consuming and costly, which restricts the number of tests to be conducted. Although various analytical and numerical models have been developed for formability prediction, most of them are applicable to only ambient conditions. Banabic et al. [3] reviewed primary models in the field of forming limit prediction at room

Rapid feasibility assessment of components to be formed through hot stamping: A deep learning approach

“…Published literature on HFQ® focuses largely on the development of advanced material models that predict the material constitutive behaviour under HFQ® conditions [4,6,[8][9][10]. These models are then used to accurately simulate the forming response of HFQ® formed components using Finite Element (FE) simulations [5,9,11] in order to assess their manufacturing feasibility.…”