Anisotropic and Pressure-Dependent Plasticity Modeling for Residual Stress Prediction

In order to provide well characterized residual stress specimens, 10-mm thick, 60-mm diameter disks of 2024-T351 Aluminum were plastically indented by opposing 15-mm diameter indenters of hardened steel. The residual stresses in the disk specimen were measured using neutron diffraction, the contour method, and the slitting method. A finite element model of the indentation process was constructed, but matching the measured residual stresses proved unexpectedly challenging. An attempt was made to improve the agreement honestly (without any unjustified parameter changes) by improving the constitutive model for 2024. Cyclic stress–strain curves were measured in multiple directions in the source plate of 2024-T351 which showed plastic anisotropy on the order of 15% in the flow strength. Recent literature has also shown a pressure dependence in 2024-T351 which would increase the flow strength in the triaxial stress region under the indenter. Combining anisotropy, cyclic loading, and pressure dependence effects in Abaqus has significantly improved agreement with the data, but a completely accurate prediction remains elusive.