Incipient spall fracture investigation in Al2024-T351

The shock response and ductile damage development in aluminum alloy 2024-T351, induced by the plate impact technique, has been investigated as a function of the orientation of the loading axis to the rolling, transverse, and through-thickness directions. Impact velocities for incipient spall were selected based on preliminary numerical simulation using the plasticity-damage self-consistent (PDSC) model with the objective to quantify the plastic deformation, accumulated under positive stress triaxiality, necessary for damage initiation. The Hugoniot Elastic Limit (HEL), compared with 0.2% yield stress, has been measured to evaluate the degree of strain-rate sensitivity along different orientations. Microstructure characterization through optical and EBSD analysis was performed on recovered samples to elucidate nucleation, growth, and coalescence process as a function of strain rate and orientation. Preliminary results seem to indicate that damage occurs by nucleating voids, with limited growth, undergoing coalescence by intervoid ligament necking and shearing.