Scale factor and punch shape effects on the expansion capacities of an aluminum alloy during deep-drawing operations

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 identifying 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 allows measuring higher strains and is less sensitive to size effect than Marciniak test.