Numerically and Experimentally Investigation of the Effect of Anisotropy and Stress Triaxiality on the Fracture Strain

The aim of this article is to investigate numerically and experimentally the effect of stress triaxiality and anisotropy on the fracture strain for metals. As the aluminum has always been one of the most widely used metals in the industry. This metal has unique properties such as lightness and high resistance to corrosion, hence, 1100 aluminum alloy is used in this article. This metal is malleable and also has high workability so it is suitable for applications including shaping. To achieve the properties of the sheet, it is first necessary that all samples were made according to the ASTM-E8 standard and the specimens were designed to achieve some different stress triaxiality. This samples includes the standard-, notched- and shear-specimens. All samples are loaded in tension state. In order to investigate the anisotropy, the specimens are prepared in rolling direction, 45 and 90 degrees to rolling direction for each samples. The uniaxial tensile test was performed on the specimens until the onset of failure. For measuring the fracture strain experimentally, a new method with lower costs than others have been proposed. For standard and notched specimens, the strain measuring is based on the difference between cross-section areas for shear-specimen, the changes in the notched radius has been proposed for strain measuring criterion. Also, in order to calculate the stress triaxiality in the fracture zone, all experiment tests are simulated in Abaqus. The equivalent plastic strain and stress triaxiality of the elements in fracture zone are reported. The average value of these elements are compared to the corresponding experimental data. At the end comparing the results obtained from experimental and simulations shows that the failure strain is calculated with great accuracy. For more explanation, the maximum error is found to be 12.8% for notched-specimen. Furthermore, the non-linear effect of stress triaxiality on the fracture strain are well shown.