Measurement of hardness and elastic modulus by load and depth sensing indentation: Improvements to the technique based on continuous stiffness measurement

Phani, P. Sudharshan; Oliver, W. C.; Pharr, George M.

doi:10.1557/s43578-021-00131-7

Cited by 44 publications

(10 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Calibrations of spherical tips can be assessed with a variety of key benchmarks. The most common benchmark in nanoindentation is observation of a constant Young's modulus with depth [e.g., 28,49]. Following the derivation from Hackett et al [16] and using Equations 4 and 9, we can express the effective Young's modulus as…”

Section: Benchmarksmentioning

confidence: 99%

Calibration and data analysis routines for nanoindentation with spherical tips

Avadanii¹,

Kareer²,

Hansen³

et al. 2023

Preprint

View full text Add to dashboard Cite

Instrumented spherical nanoindentation with a continuous stiffness measurement has gained increased popularity in material science studies in brittle and ductile materials alike. These investigations span hypotheses related to a wide range of microphysics involving grain boundaries, twins, dislocation densities, ion-induced damage and more. These studies rely on the implementation of different methodologies for instrument calibration and for circumventing tip shape imperfections. In this study, we test, integrate, and re-adapt published strategies for tip and machinestiffness calibration for spherical tips. We propose a routine for independently calibrating the effective tip radius and the machine stiffness using three reference materials (fused silica, sapphire, glassy carbon), which requires the parametrization of the effective radius as a function of load. We validate our proposed workflow against key benchmarks, such as variation of Young's modulus with depth. We apply the resulting calibrations to data collected in materials with varying ductility (olivine, titanium, and tungsten) to extract indentation stress-strain curves. We also test the impact of the machine stiffness on recently proposed methods for identification of yield stress, and compare the influence of different conventions on assessing the indentation size effect. Finally, we synthesize these analysis routines in a single workflow for use in future studies aiming to extract and process data from spherical nanoindentation.

show abstract

Section: Benchmarksmentioning

confidence: 99%

Calibration and data analysis routines for nanoindentation with spherical tips

Avadanii¹,

Kareer²,

Hansen³

et al. 2023

Preprint

View full text Add to dashboard Cite

show abstract

“…Most indentation instruments are preset calculation equations of hardness [49,50]. The penetration depth h is calculated through an initial point that the indenter begins to contact the tested surface of the specimen.…”

Section: Theoretical Modelmentioning

confidence: 99%

Study on Size Effect in Indentation Tests

Zhang

Dong

et al. 2022

Coatings

View full text Add to dashboard Cite

The depth dependence of the indentation hardness, i.e., the indentation size effect (ISE), was manifested as an increase or decrease in hardness when penetration depth decreases, which was observed by previous experiments. Most scholars believe it is generated by strain gradient. However, additional opinions argue that other factors, similar to the strain gradient, can also contribute to the ISE. Importantly, if such an ISE occurs in an experiment, one needs to distinguish its causes. In this study, two external factors were considered, i.e., the specimen surface defect and indenter tip irregularity, which can lead to the hardness–depth-dependent relationships of the ISE. Moreover, a theoretical model was established to interpret the two dependent relationships and validated via finite element simulations. The simulation results showed that both external factors lead to significant hardness–depth dependences, in great agreement with theoretical derivations. Moreover, the simulation results demonstrated that the surface defect and indenter tip irregularity have a unified influence on the ISE, which is attributed to a sole depth deviation d. Lastly, the ISE based on both external factors was eliminated and the real hardness was obtained. Based on this, when an ISE appears, it can be distinguished whether it is caused by external factors or strain gradient.

show abstract

“…In 2002, it became the first and, to date, the only nanomechanical testing method sanctioned with an ISO norm (ISO:14,577 [7]). Still, a non-negligible number of the contributions to this focus issue are devoted to further improving its reliability [8][9][10][11][12][13], based on emerging technologies. These include more accurate imaging [8,10,11] and faster data processing [9], which, for example, allow for improved characterization of the geometry of the indenter tip and the resulting contact area.…”

Section: Nanoindentationmentioning

confidence: 99%

“…Still, a non-negligible number of the contributions to this focus issue are devoted to further improving its reliability [8][9][10][11][12][13], based on emerging technologies. These include more accurate imaging [8,10,11] and faster data processing [9], which, for example, allow for improved characterization of the geometry of the indenter tip and the resulting contact area. In addition, this focus issue documents new method developments, which aim at further expanding the capabilities of nanoindentation beyond the measurement of hardness and Young's modulus, e.g., accessing the local creep properties [14], ductility [15], and surface free energy [16] of materials.…”

Section: Nanoindentationmentioning

confidence: 99%