Experimental Investigation of Stress Triaxiality-Equivalent Plastic Strain Relations at Failure of A2024-T3 via Digital Image Correlation for Fracture Model Calibration

Abstract

Stress triaxiality is a well-established factor influencing material failure, particularly after elongation. Its significance is evident in its widespread use among damage accumulation models. In this study, we aim to analyze the post-necking behavior of thin metal sheets, specifically A2024-T3 aluminum alloy sheets. Such behavior is explored across a spectrum of stress states, ranging from shear to biaxial conditions. To ensure the robustness of the findings, experiments were conducted on three different lots of the same designated appellation, carefully considering the subtle microstructural variations. The data was meticulously gathered through localized fracture area analysis, employing digital image correlation techniques. Stress triaxiality was directly calculated from the experimental data. Notably, this study offers normalized data using a specific specimen shape, which is particularly valuable in scenarios where conducting an extensive array of experimental tests may be difficult. Based on the results, the overall shape of the fracture locus was effectively confirmed. Moreover, this study provides valuable insight on the influence of microstructure on the fracture locus. Finally, parameters essential for numerical simulations were determined.