Development of a plane strain tensile test to characterize the formability of 5xxx and 6xxx aluminium alloys

This article presents the development of a plane strain tensile test aiming at an easy classification of aluminium automotive alloys according to their formability in prototyping steps. A parametric study with finite element method is performed on three different designs inspired by literature. It is found that, due to plastic anisotropy, specimens designed for steel are not suited for aluminium alloys. One optimized specimen geometry, ensuring near plane strain state on a large zone all along the deformation range up to failure, is selected. On this geometry, tensile tests instrumented by Digital Image Correlation are performed for five different aluminium alloys (5xxx and 6xxx) in three different directions of the metal sheet (rolling, diagonal and transverse). From Digital Image Correlation analysis, necking limits are evaluated and their relevance for the ranking of alloys according to their formability is discussed in comparison with a standard formability test, namely the Limiting Dome Height test.