In-Situ DIC and Strain Gauges to Isolate the Deficiencies in a Model for Indentation Including Anisotropic Plasticity

Abstract

A 60-mm diameter disk of 2024 aluminum was indented by opposing steel indenters over a central 10 mm region. Residual stress measurements made using neutron diffraction and the contour method matched each other, but not a finite element (FE) model with a calibrated model for plastic anisotropy of the aluminum. Since residual stresses are only the endpoint of the process, in situ data was needed to determine which portion of the load/unload process was causing model deficiencies. The indentation process was repeated on a new specimen with three-dimensional Digital Image Correlation (3D-DIC) to map full-field strain information and with resistance strain gauges to obtain high fidelity strain information at discrete locations. The DIC data was too noisy to extract strains, so displacements were analyzed after rigid body motion was removed. The deformation field revealed geometric imperfections of the indenters that were within tolerance, but had significant effect on the stress state. An updated FE model including geometric imperfections in the indenters gave better agreement with the DIC data. It did not however allow the material model to become the dominant effect and thus model calibration was unsuccessful.

Jacob Merson

Assistant Professor of Mechanical Engineering

loves to scale multiphysics simulations onto leadership class supercomputers