FE-based springback prediction of sheet metal forming processes from lightweight materials considering the anisotropic hardening

Funding period:

Start: 1. February 2019
Ende: 31. January 2021

Abstract

Lightweight construction allows a reduction in the weight of transportation means and thus contributes to meeting the growing demands for lower emissions and higher payloads. Therefore, especially lightweight materials, such as magnesium and high-strength aluminium alloys, are of importance in the automotive and aviation industry. Since magnesium and high-strength aluminium alloys are limited formable at room temperature, they are usually formed at elevated temperatures. Furthermore, previous investigations have shown that these materials harden anisotropically and exhibit a temperature-dependent as well as a tensile-compressive asymmetric material behaviour. According to the current state of research, new approaches are required to integrate the asymmetric hardening behaviour of magnesium and high-strength aluminium alloys into appropriate material models.

Within this research project, selected magnesium and high-strength aluminium alloys will be examined for anisotropic hardening and tensile-compressive asymmetric material behaviour. Using isothermal cold forming and warm forming tests between room temperature and 200°C, relevant material parameters are determined to provide support points for a material model.To characterize the material parameters, uniaxial tensile and compression tests as well as shear tensile and bulge tests are carried out. According to present research, the relations between the microstructure and the tension-compression asymmetry of high-strength aluminium alloys are insufficiently identified. Hence, the uniaxial tensile and compression tests are also metallographically analysed to detect the change in the microstructure after tensile or compressive load. The material behaviour is modelled on the basis of the experimentally detected support points, by selecting suitable yield criteria, identifying them and classifying them with regard to the mapping accuracy. The identified material model is extended by the anisotropic hardening as well as the temperature dependence and subsequently evaluated by a reference model. The extended material model is implemented in an industry-oriented simulation environment and then verified by comparison with the experimentally determined flow curves. For validation of the developed material model, the real spring back angle of a deep drawn cross profile is investigated and compared with the predicted spring back angle of a simulation model. Subsequently, the extended material model is assessed with respect to the prediction accuracy of the spring back behaviour.

Research groups

• Materials Characterization and Modelling

Publications