Modeling of Crack Growth in Thin Sheet Aluminum

The present study reports on the application of a cohesive zone model to the analyses of crack growth in thin sheet specimen of a high strength aluminum alloy. In addition to the elastic-plastic material properties, the two parameters cohesive strength and cohesive energy describe material separation. For the sheet specimen under investigation the cohesive energy is determined via a numerical-experimental approach using tests on notched tensile specimens as well as a damage indicator. The cohesive energy is found to be close to the corresponding value of plane strain fracture toughness. The cohesive strength is approximately twice the yield strength. With these two additional material parameters being determined crack growth experiments in center crack panels are analyzed. Good agreement with experimental records is found. Finally the applicability of the model to study complex crack configurations as in multi-site damaged specimens is demonstrated.