Profilometry‐Based Inverse Finite Element Method Indentation Plastometry

Abstract

This is a review of the current state‐of‐the‐art regarding a particular approach to extraction of the (quasistatic) stress–strain relationship of a metallic sample from an indentation experiment. It is based on the application of a relatively high load (kN range) to the sample via a large spherical indenter (≈1 mm radius), followed by measurement of the indent profile. This profile is then used as the target outcome for inverse finite element method (FEM) modeling of the test, aimed at converging on the best fit set of parameter values in a constitutive plasticity law (true stress–true strain relationship). This can then be used to simulate any specified loading configuration, including a conventional tensile test. Commercial products are now available in which the indentation, profilometry, and convergence operations are all automated and completed within a few minutes. The review covers the various conceptual and practical issues involved in implementation and optimization of these procedures, including both those related to the measurement system (experimental and FEM simulation) and those associated with the sample (such as anisotropy, inhomogeneities, and residual stresses). An attempt is made to convey an impression of the expected levels of reliability and also the scope for obtaining insights that are not readily obtainable using other types of test.

Indentation Plastometry of Very Hard Metals

“…These steps are described in detail in a recent review paper. [8] Samples for indentation were in the form of 8 mm thick plates with lateral dimensions of about 45 by 20 mm. (As the preferred spacing between indents made with a 1 mm radius ball is at least about 4 mm, this allowed up to about 20 indents to be produced on each sample.)…”

“…Its emergence is the outcome of an extended period of research and development. [1][2][3][4][5][6][7][8] The superior reliability of PIP to the (instrumented indentation technique) methodology of converting a load-displacement plot to a stress-strain curve via analytic relationships has been clearly demonstrated. [9] It has already been applied to a thin plasma-sprayed layer [10] and (anisotropic) additively manufactured material, [11] both Ni-based superalloys.…”

Uncertainty Quantification of a High-Throughput Profilometry-Based Indentation Plasticity Test of Al 7075 T6 Alloy

“…Importantly, the observed grain size distribution is much lower than 500 μm, i.e., the threshold for the PIP test. Below the threshold, variability in local microstructure is not expected to affect the accuracy of indentation predictions, as the plastic zone is estimated to contain at least a few dozen grains (Clyne et al, 2021).…”

“…The relationship is inverse, so the simulation must be performed iteratively to optimize the parameters of the plasticity model to reproduce the observed profile. This process has been thoroughly documented elsewhere (Campbell et al, 2021;Clyne et al, 2021). The following overview is included to support discussion of uncertainty quantification.…”

An Inverse Method for Measuring Elastoplastic Properties of Metallic Materials Using Bayesian Model and Residual Imprint from Spherical Indentation

“…The spherical indentation profile has been proved to be more sensitive to the plastic parameters of materials than the load-displacement curve [ 13 ]. In the work by Clyne et al [ 23 ], the advantages of using the indentation imprint were summarized. It does not require the extra indentation loading–unloading data, thus eliminating the uncertainties involved in machine compliance.…”