Abstract
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.
Highlights
Forming of metal sheet is studied in many technologic fields especially in automotive industry
Data related to Forming Limit Diagram (FLD) of 2024 Al alloy have been reported in the literature
The aim of this study is to investigate the differences between two deep-drawing tests (Marciniak test and hemispheric punch test) and their capacities to be repetitive when changing the tooling and sample dimensions
Summary
Forming of metal sheet is studied in many technologic fields especially in automotive industry. The most widely used method is to draw a forming limit diagram from deep drawing tests. The forming limit diagram is drawn from the major and minor strains observed at the surface of the sample. This diagram generally corresponds to the boundary between uniform strain and diffuse necking [1, 2] but the choice of the limit criteria remains an open question. To investigate formability limits of Al 2024 in expansion, major and minor strains data were generated using both Marciniak tests and hemispherical punch tests and both centimetric and decimetric punch dimensions
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