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Design optimisation of a side impact beam made out of high strength aluminium alloys using Barlat YLD2000 and GISSMO failure model for the “Extended Hotforming Process”

The automotive industry is facing new challenges due to stricter CO2 emission laws. Thus, to design more environmentally-friendly cars, various lightweight construction strategies need to be considered to meet the growing demand for resource efficiency [1]. In order to minimise weight, the lightweight design strategy "design for lightweight construction" is increasingly becoming important for industry. Especially the “structural optimisation” with its sub-areas: topology-, fibre-, thickness- and parameter-optimisation is designated as a very powerful tool for lightweight applications. In addition, damage and failure modelling is getting more and more important in order to predict the behaviour of any component by FEM-simulations as accurate as possible. For this purpose, the entire material history (from production right through to the crash of the component) must be taken into account. Whereas for forming processes forming limit curves (FLC`s) are sufficient to predict the material behaviour failure models, which describe failure as a function of stress states, need to be applied for detailed crash calculations [2]. In this paper the design process of an AA7075 side impact beam will be presented; starting from structural optimisation through to the calibration of a material and a damage model. The geometry of the side impact beam is determined by topology optimisation. Special attention is given towards the temperature control of the forming process since a “Thermal Direct Joining” procedure (e.g. for CFRP-patches) is aimed to be implemented. The high-strength anisotropic aluminium alloy (AA7075) is characterised after applying the Hotforming process (Hotforming condition). Both, the Barlat YLD2000 material model and the GISSMO failure model are calibrated using the graphical optimisation tool LS-OPT.