Explicit full-range stress-strain model for aluminium alloys

An accurate stress-strain model is fundamental to the reliable analysis of aluminium structures, which are increasingly used due to their favourable properties such as corrosion resistance. Explicit stress-strain models offer higher computational efficiency than implicit formulations, particularly for fibre-based and analytical methods. However, existing explicit models remain limited and neglect the post-necking stage, which is essential for capturing large-deformation and fracture behaviour of aluminium alloys. This study aims to develop an explicit full-range stress-strain model for aluminium alloys that incorporates the post-necking stage. The formulas for pre-necking response are derived by inverting the two-stage Ramberg-Osgood model, while post-necking behaviour is characterised using an established equation for high-strength steels, calibrated with over 90 test data points. Predictions from the proposed model and two existing models are compared with experimental stress-strain curves of five commonly used aluminium alloy grades. Results demonstrate that the proposed model accurately captures the full-range stress-strain response up to fracture when supplied with accurate material parameters and outperforms existing explicit models. Overall, the proposed model serves as an effective tool for numerical simulation, analytical modelling, and advanced design of aluminium alloy structures.