Digital Repository, ECF14, Cracow 2002

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Ductile rupture of 2024 aluminum thin sheets - Experimental study of damage growth and crack initiation

Last modified: 2013-02-10


The damage and rupture mechanisms of a 2024 aluminum thin sheet are investigated.Mechanical tests are carried out on flat specimens including smooth tensile panels,U-notched samples with various notch radii and V-notched samples. Cracked samples werealso tested which include Kahn samples and large MT panels; stable crack growth is obtainedin both cases. The microstructure of the material is characterized to obtain the second phasevolume content. The largest particles consist of intermetallics. The macroscopic fracture surfaceof the different specimens is observed using scanning electron microscopy. Smooth andmoderately notched samples exhibit a slanted fracture surface, which has an angle of about45 with the loading direction. With increasing notch severity, the fracture mode changessignificantly. Failure initiates at the notch root in a small triangular region whose normal isparallel to the loading direction. Outside this zone, slant fracture is observed. Microscopicobservations show two failure mechanisms. Voids are first initiated at intermetallics in bothcases. At low stress triaxiality ratio (smooth or moderately notched samples), these voids tendto coalesce rapidly according to a “void sheet mechanism” which creates smaller dimples inthe inter-void ligaments. At higher triaxiality, void growth is promoted and final rupture iscaused by “internal necking” between the large cavities.

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