A mathematical description of orthotropy in sheet metals

The plane stress description of orthotropy presented by Hill [1990. Constitutive modelling of orthotropic plasticity in sheet metals. J. Mech. Phys. Solids 38(3), 405–417] is revisited. In particular, the calibration methods are analysed in an alternative form. The alternative calibration methods are used to develop the mathematical form of the orthotropic representation. The new seven parameter yield criterion is shown to be more flexible than the current model without the need for additional test data. The usefulness of the model in describing aluminium, titanium and steel is also illustrated.