Estimating the slip resistance from spherical nanoindentation and orientation measurements in polycrystalline samples of cubic metals

Abstract

In this paper, we demonstrate the first application of a recently formulated two-step approach to the estimation of the average slip resistance in a cubic polycrystalline metal sample from a collection of spherical nanoindentation and lattice orientation measurements. In the first step, a crystal plasticity finite element model of the spherical nanoindentation experiment is developed, validated, and employed to capture the functional dependence of the indentation yield strength on the crystal lattice orientation at the indentation site. This functional dependence is captured in a compact representation using surface spherical harmonics (SSH) functions. In the second step, measured values of the indentation yield strength and the crystal lattice orientations at the indentation site from a polycrystalline sample are fit to the function established in the first step to provide a robust estimate for the value of the average slip resistance in the sample. The validity of this approach is demonstrated for cast and annealed Fe-3% Si using measurements published in prior literature.

High Throughput Assays for Additively Manufactured Ti-Ni Alloys Based on Compositional Gradients and Spherical Indentation

“…The main issues in this correlation are indeed related to the differences in the probe volumes and the inherent anisotropy of material response at the probed length scales. At this time, these correlations are most mature at the two ends of the spectrum of applications: (i) the indented volume is very large compared to the representative volume element of the material microstructure, and allows idealization of the material response in the indentation zone as a homogeneous isotropic medium [13,57] and (ii) the indented volume is a single phase crystalline region (e.g., a region within a grain in a single-phase polycrystalline sample) [7,13,32,58]. Clearly, the indentations in the sample studied here do not fall into either of these idealized conditions.…”

A Bayesian Framework for the Estimation of the Single Crystal Elastic Parameters From Spherical Indentation Stress-Strain Measurements

“…Currently employed strategies for extracting intrinsic material properties from indentation tests have generally involved the calibration of physics-based finite element (FE) models of these tests to the corresponding set of experimental measurements [6,[9][10][11]. In this regard, it has been pointed out in recent work [7] that these protocols are much more robust when the calibration is attempted in the form of the normalized indentation stress-strain curves as opposed to directly matching the load-displacement curves. This is mainly because the initial elastic response and the elastic-plastic transition occur over a very short early portion of the load-displacement curve that is not easily identified and isolated, resulting in a very high sensitivity of the extracted values of the intrinsic material properties to small changes in the calibration procedures.…”

“…The main challenge comes from the high computational expense of FE simulations of the indentation experiments. It should be noted that establishing each data point on the FE predicted indentation stress-strain curve needs the simulation of a suitable unloading segment [7], and this drives up the cost of the simulation significantly. Given all of the complexity described, the only logical path forward is to establish a reduced-order model for the FE simulations of the indentation test, and to use the reduced-order model in solving the inverse problem described above.…”

New Insights into the Microstructural Changes During the Processing of Dual-Phase Steels from Multiresolution Spherical Indentation Stress–Strain Protocols

“…An example indentation stress-strain curve extracted using the above protocols presented in Figure 3c. The spherical nanoindentation stress-strain protocols described above have been validated extensively in both experiments [53][54][55][56][57][58][59][60][61] and numerical simulations (performed using finite element models) [96][97][98][99]. As a result of these prior validations, we are now fairly confident in obtaining highly reproducible indentation stress-strain curves on a broad variety of material samples.…”