Initial Crack Extension in Two Intermediate-Strength Aluminum Alloys

Three-point bend tests were conducted to examine the geometry dependence of J_Ic in two intermediate-strength aluminum alloys, 2024-T351 and 7005-T6351. The amounts of crack growth at selected points on the load-versus-deflection curves were delineated using a heat tinting technique. Resistance curves of J-versus-crack extension were constructed to facilitate determination of J_Ic at incipient crack movement. The through-thickness variation in fracture toughness of a 7.6-cm-thick plate of 7005 aluminum was determined and correlated with fractographic and metallographic observations. The current J_Ic measurements from subsized specimens of 7005 aluminum are compared with previous K_Ic characterizations using linear-elastic, full-thickness specimens.