Influence of the Punch Geometry and Sample Size on the Deep-Drawing Limits in Expansion of an Aluminium Alloy

The effects of punch geometry and sample size on forming limit diagrams in expansion are investigated in the case of a 2024 aluminium alloy. Four configurations were selected: flat punch (Marciniak test) or hemispheric punch and decimetric vs. centimetric tooling dimensions. Both decimetric and centimetric deep-drawing devices are associated with an image correlation tool that allows to identify without any contact the deformation on the surface of planar or non-planar specimens. Strains on the surface of the samples are observed by means of a double numerisation in three dimensions of the sample before and after deformation by using stereoscopic vision and triangulation. Finally, deep-drawing limit of the four configurations are compared in expansion state and with literature. Results mainly show that hemispherical punch is less sensitive to size effect than Marciniak test.