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Cycle:. Cycle:. Cycle:. Cycle:. 0. 1. 100. 3000. 7050-T74. 10 m m. 250 m m. Common Damage Mechanisms. 7075-T651. Loading Direction. (a) Incubation – the process that leads to the first appearance of a cracked particle
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Cycle: Cycle: Cycle: Cycle: 0 1 100 3000 7050-T74 10 mm 250 mm Common Damage Mechanisms 7075-T651 Loading Direction • (a) Incubation – the process that leads to the first appearance of a cracked particle • (b) Nucleation – the appearance event of a crack in the matrix • (c) Propagation– the process of crack extension governed by microstructural heterogeneities • Stage I – Slip along a single band • Stage II – Slip along multiple bands, causing crack propagation subnormal to the global tensile direction • (d) Grain Boundary Decohesion– the process of crack formation/extension governed by misorientation of neighboring grains Loading Direction (a) (b) (c) (d) b 10 mm a c Stage I/II illustration from: C. Laird, 1967. SEM/OIM courtesy of Northrop Grumman Corporation