Fracture of U- and V-notched Al6061-T6 plates: The first examination of the Fictitious Material Concept under mixed mode I/III loading

In this study, for the first time, the load-carrying capacity (LCC) of test specimens containing U-shaped and V-shaped notches made of Al6061-T6 aluminum alloy under combination of out-of-plate shear and tensile loading (mixed mode I/III) is studied. U-notched specimens are made with different notch tip radii and V-notched specimens are made with different notch tip radii and notch opening angles. At first, the specimens are subjected to different mixed mode I/III loading conditions using a universal tension-compression loading device and their LCCs are measured experimentally. Then, considering the ductile behavior of the material under investigation, it is attempted to use the Equivalent Material Concept (EMC) in theoretical analysis, since it does not require complex and time-consuming elastic-plastic analyses. Initial evidence for the combination of the EMC with the brittle fracture criteria of point stress (PS) and mean stress (MS) indicates that both criteria show large errors in predicting the LCC of the test samples. The cause is the large failure strain of the Al6061-T6 alloy. Therefore, a newly developed concept similar to the EMC, called the Fictitious Material Concept (FMC), is applied. Based on the FMC, instead of equalizing the elasticity modulus of the ductile material and the fictitious material, the failure strains of those materials at the ultimate points are assumed to be equal. It is shown that combining the FMC with the PS and MS criteria leads to acceptable predictions of the LCC of the tested specimens.