Fracture behavior of thin foils

The downscaling of manufacturing processes leads to a rise in new challenges in process design. Amongst these challenges is a decrease in the limiting drawing ratio observed in micro deep drawing of metal foils. Furthermore, fracture occurs at punch force levels well below those predicted by common equations. In this paper it is proposed that these phenomena can be accounted for by non-uniformities in the flow behavior of the material due the large difference between grain sizes. The localized strains before fracture – as recorded by digital image correlation – of stretch formed aluminum foils are presented and the strain evolution is examined. Evidence to verify the hypothesis is gathered by implementing the observed flow non-uniformities into a finite element simulation and comparing the computed results to the experimental ones.