Residual Strength of an Aluminum Panel with a Centric Hole and One Cracked Ligament

The residual strength of an aluminum panel with a centric hole and one cracked ligament was investigated experimentally. Each of the 7075-T6 aluminum panels which were tested included a cracked ligament of varying length on one side of the centric hole and an uncracked ligament on the other side of the hole. The failure of such a panel subjected to uniform tensile loading normally occurs according to the lower of two modes: brittle fracture or a net section type of yielding. On the other hand, the question of whether one or both ligaments fail is not easily answered. Results show that one or two ligament failure depends upon test conditions such as crack length and loading method. For short crack lengths, the uncracked ligament will fail almost simultaneously with the failure of the cracked ligament. In the case of long crack lengths, the ligament with the crack will completely fracture, followed by arrest until the load is increased so as to cause failure (by yielding) in the remaining uncracked ligament. Test results also show that the loading method used by the test machine also affects the ligament failure process. Some results for panels subjected to fastener loading are also discussed.