Link-Up Strength of 2524-T3 and 2024-T3 Aluminum Panels with Multiple Site Damage

The aluminum alloy 2524-T3 is replacing 2024-T3 for many applications because 2524-T3 has a greater fracture toughness while retaining the same strength. Much attention has been given to the effect of multiple site damage on 2024-T3 aluminum; however, very little has been reported about 2524-T3. Twenty-two panels of 2524-T3, each with a different crack configuration, were tested for critical (linkup) strength, and the results were compared with an identical set of previously tested 2024-T3 panels with MSD. The panels were 24 in. wide with a midspan row of 0.25-in.-diam holes at 1-in. pitch. Each panel had a central lead crack with collinear MSD cracks emerging from both sides of the adjacent holes. A comparison of the results showed the 2524-T3 panels to average approximately 27% greater strength than the 2024-T3 panels. The linkup or plastic-zone-touch model used to predict the critical (link-up) strength of the panels was found to be highly conservative. Consequently the test data were used for a semi-empirical analysis to develop a modified link-up model for 2524-T3, similar to the one previously developed for 2024-T3. The average error between the critical strengths from testing and those predicted by the link-up model was approximately 20%, whereas that for the modified link-up model was approximately 3%.