Speaker
Description
This study targets a new observable for the simultaneous identification of the plastic parameters governing hardening mechanisms in Face Centered Cubic (FCC) single crystals via inverse method. Specifically, the goal is to design nanoindentation experiments that will be carried out to identify the 10 hardening parameters, including 7 slip system interaction parameters, of a single crystal Méric-Cailletaud type behavior law. The parameters are identified from lattice rotations after a Berkovich nanoindentation test, instead of classical observables such as the indentation curve (P-h) or residual topography.
In the literature, P–h curves have been widely used to identify elastic–plastic parameters of materials. However, many studies have shown that it is generally impossible to identify hardening plastic parameters using a single tip geometry. Residual topography provides richer information compared to P-h curve. However, previous works indicate that properly posing the inverse problem for parameter identification typically requires residual topography datasets collected from multiple relative orientations between tip and crystal.
The present work aims to quantify the information richness of the volumetric misorientation angle and the residual topography. Three-dimensional Crystal Plasticity finite element (CPFEM) simulation of the nano-indentation is performed for 13 selected crystallographic orientations. For each orientation, the information content of both the resulting volumetric misorientation angle field and residual topography is evaluated through a local parametric identifiability analysis.
The results demonstrate that the choice of observable strongly governs the achievable level of identifiability, while crystallographic orientation has a smaller, but noticeable, effect. In fact, the volumetric lattice misorientation angle field provides a better conditioning of the inverse problem than the residual topography. The identifiability analyses show that, when using the volumetric misorientation angle field as the observable, a single crystallographic orientation is sufficient to simultaneously identify the ten hardening parameters of a Méric–Cailletaud type law after Berkovich nanoindentation test.