Influence of specimen width on the deformation and fracture behaviour of AA5182 sheets

In this work, the influence of specimen width (in the range 6–15 mm) on the tensile deformation and fracture behaviour of AA5182 aluminium alloy sheets, characterised by the Portevin-Le Chatelier effect, was investigated. The experimental results showed that the elongation at necking and the plastic strain at fracture are influenced by the specimen geometry and, in particular, reached a maximum at a width of 12.5 mm. The experimental results are discussed on the basis of a finite element modelling of the tensile test. The material’s constitutive behaviour was implemented following an approach that accounts for microstructural inhomogeneities by considering the material to be composed of a matrix (main component) and regions of slightly higher and lower strength. The plastic properties of the three microstructural constituents were represented by interpolating the tensile stress–strain curve using Voce’s relationship. In this way, it was shown that the geometry of the specimen influences the onset and development of the stress triaxiality during plastic deformation, thus explaining the specimen width effect observed in the experimental results.