Abstract
The dependence of fracture strain on stress triaxiality has been recently recognized as an important factor that controls the fracture of aluminum alloys. A number of experimental programs have been reported to determine fracture strains in a wide range of stress triaxiality using a variety of types of specimens. However, because of the lack of direct measurement of local strains near the fracture zone, indirect estimations of fracture strain are commonly used. The errors in determining fracture strain are uncertain. In this study we use the digital image correlation (DIC) method to determine the fracture strains in AA6060 aluminum extrusion material. This material is often used in automotive crash management systems. A commercially available DIC system was used to follow the deformation occurring during the tests of a set of newly designed specimens with a wide range of stress triaxiality; thus, the inception of instability and fracture can be captured and distinguished precisely. More importantly, post-experiment analysis in DIC allows strain calculations at macroscopic levels at varying step sizes, thus, the dependence of fracture strain on gauge length has been determined in each testing condition. The fracture locus of AA6060 aluminum extrusion has been successfully determined and the concept of “scaled fracture strain” has then been proposed to ensure consistency of the fracture locus in both the experiment and in modeling.
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