Flow curve approximation of high-strength aluminium alloys in heat-assisted forming processes; M. Schmiedt, R. Schneider, J. Jung · W. Rimkus, A. K. M. De Silva, Production Engineering, Springer Verlag, 2024
von Wolfgang, Rimkus
Abstract
Predicting the flow behaviour at high strain values beyond uniform elongation is a critical factor in sheet metal forming,especially in the context of heat-assisted forming processes of lightweight materials. Based on uniaxial tensile tests con-ducted at the temperature profiles of the Hotforming, W-Temper, and Warmforming process routes this study presents thedetermination of the flow curve for EN AW-7021 sheet material using five commonly used empirical approximation models.A support point obtained from layer compression tests was introduced to analyse the accuracy of the extrapolation models athigher strain values. All models considered were found to be in good agreement with the experimental tensile test data in thearea of uniform elongation. However, the empirical approximation models show significant differences in strain hardeningbehaviour when higher strain values and varying temperature profiles are considered. For the Hotforming and W-Temperprocess routes, the Hockett-Sherby model estimates the flow behaviour with the highest accuracy. When using the Warmform-ing process, all approximation models considered seem to estimate the flow behaviour with reasonable accuracy, howeverthe Ludwik-Hollomon modified equation shows the best correlation with the experimental data.