Characterisation of out-of-plane shear behaviour of anisotropic sheet materials based on indentation plastometry

This paper presents a new methodology for characterising the out-of-plane plastic anisotropy behaviour of sheet metal, based on indentation testing. Conventionally, advanced yield criteria are used to describe plastic anisotropy, requiring multiple in-plane mechanical tests (such as uniaxial and biaxial tests) to calibrate a model. However, in certain forming applications (e.g. blanking, ironing and incremental forming), the influence of mechanical behaviour through thickness cannot be ignored, necessitating the characterisation of out-of-plane material behaviour. To do this, a 3D plastic anisotropy model must be used and calibrated for the out-of-plane shear parameters, which can be difficult to determine. Researchers often assume an isotropic case or equal shear parameters for in-plane and out-of-plane behaviour. More advanced calibrations involve the crystal plasticity model. In this work, we propose a two-stage calibration procedure. In the first stage, we calibrate the in-plane parameters of the YLD2004–18p yield function conventionally. In the second stage, after fixing the in-plane parameters, we determine the remaining out-of-plane shear parameters based on the results of the ball indentation test. We show for the first time that out-of-plane shear parameters can be determined from a macro-mechanical test for a 2.42 mm thick cold-rolled AA5754-H22 series aluminium sheet.