Insights into Cruciform Sample Design.

Four different cruciform sample designs, based on the work of Abu-Farha et al., were studied in this paper. Key features of this design are a recessed pocket with fillet and re-entrant corners. These samples were shown via digital image correlation to achieve widely differing strain values inside and outside the pocket. From the results of these tests, there are two competing failure mechanisms in the sample. The pocket region is affected by stress concentrations caused by the fillet, and re-entrant notches lead to strain limited constraints similar to diffuse and localized necks in uniaxial samples. Balancing these two constraints determines the success or premature failure of the sample.