Experimental Investigation of Crack Propagation Mechanisms in Commercially Pure Aluminium Plates

The crack surface morphology in tearing of ductile metal plates depends on the mechanical properties, chemical composition and the microstructure of the plate material as well as on the loading conditions and the specimen geometry. This study assesses the crack surface morphologies observed in commercially pure aluminium plates (Al 1050 H14). Mode I tearing was performed in both single and double edge notched tensile test setups with specimens cut from five different plates with different thickness t, viz. t ϵ {0.5, 1,3,4,5} mm. In each combination, the long axis of the notch was either parallel (0°) or perpendicular (90°) to the rolling direction. Fractographs showed that, for specimen thicknesses smaller than 5 mm, the crack had a cup-cup morphology almost throughout its entire length for 0° specimens, while slanted crack propagation was visible in some regions of 90° specimens. For t = 5 mm, on the other hand, the dominant crack morphology was slanted for both directions, the extent of the cup-cup regions being larger for 0° specimens. The crack morphologies were repeatable for each direction-thickness combination, while also being consistent for both test setups having different loading conditions.