Nanoindentation of Fused Quartz at Loads Near the Cracking Threshold

Mound, Brittnee A.; Pharr, George M.

doi:10.1007/s11340-018-00446-3

Cited by 13 publications

(7 citation statements)

References 45 publications

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“…For smaller indentation loads, it is possible to find occasional indents without cracking (Figure A). Indents produced at loads below 3 N are mostly affected by edge cracks only, a crack type known to penetrate the material only to a relatively low depth . The present dataset indicates that cracking does not affect the determination of σ Zmax .…”

Section: Resultsmentioning

confidence: 57%

“…Indents produced at loads below 3 N are mostly affected by edge cracks only, a crack type known to penetrate the material only to a relatively low depth. 41 The present dataset indicates that cracking does not affect the determination of σ Zmax . Yet, cracking can introduce local shape modifications and thereby affect the expected laser spot position and the shape of the σ depth profile.…”

Section: Indentation Densification Field Of Silica Glass By Raman Smentioning

confidence: 53%

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Indentation densification of fused silica assessed by raman spectroscopy and constitutive finite element analysis

Bruns

Uesbeck²,

Fuhrmann

et al. 2020

J Am Ceram Soc

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Inelastic deformation of anomalous glasses manifests in shear flow and densification of the glass network; the deformation behavior during indentation testing is linked strongly to both processes. In this paper, the indentation densification field of fused silica is investigated using depth‐resolved Raman spectroscopy and finite element simulations. Through affecting the size of the indent, the normal load and the Raman laser spot size determine the spatial sampling resolution, leading to a certain degree of structural averaging. For appropriate combinations of normal load (indent size) and laser spot diameter, a maximum densification of 18.4% was found at the indent center. The indentation behavior was modeled by extended Drucker‐Prager‐Cap (DPC) plasticity, assuming a sigmoidal hardening behavior of fused silica with a densification saturation of 21%. This procedure significantly improved the reproduction of the experimental densification field, yielding a maximum densification of 18.2% directly below the indenter tip. The degree of densification was found to be strongly linked to the hydrostatic pressure limit below the indenter in accordance to Johnson's expanding cavity model (J. Mech. Phys. Solids, 18 (1970) 115). Based on the good overlap between FEA and Raman, an alternative way to extract the empirical correlation factor m, which scales structural densification to Raman spectroscopic observations, is obtained. This approach does not require the use of intensive hydrostatic compaction experiments.

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Section: Resultsmentioning

confidence: 57%

Section: Indentation Densification Field Of Silica Glass By Raman Smentioning

confidence: 53%

Indentation densification of fused silica assessed by raman spectroscopy and constitutive finite element analysis

Bruns

Uesbeck²,

Fuhrmann

et al. 2020

J Am Ceram Soc

View full text Add to dashboard Cite

show abstract

“…This might seem unexpected as the opening angle of the conical indenter was chosen to produce projected areas in good accordance with the Berkovich indenter. However, it should be noted that the indentations were performed at a shallow depth (100 to 250 nm), in order to remain below the cracking threshold of the materials [22]. At such depth, the tip blunting of the indenters cannot be neglected as it influences their effective geometries.…”

Section: Discussionmentioning

confidence: 99%

Conical Nanoindentation Allows Azimuthally Independent Hardness Determination in Geological and Biogenic Minerals

et al. 2019

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The remarkable mechanical performance of biominerals often relies on distinct crystallographic textures, which complicate the determination of the nanohardness from indentations with the standard non-rotational-symmetrical Berkovich punch. Due to the anisotropy of the biomineral to be probed, an azimuthal dependence of the hardness arises. This typically increases the standard deviation of the reported hardness values of biominerals and impedes comparison of hardness values across the literature and, as a result, across species. In this paper, we demonstrate that an azimuthally independent nanohardness determination can be achieved by using a conical indenter. It is also found that conical and Berkovich indentations yield slightly different hardness values because they result in different pile-up behaviors and because of technical limitations on the fabrication of perfectly equivalent geometries. For biogenic crystals, this deviation of hardness values between indenters is much lower than the azimuthal variation in non-rotational-symmetrical Berkovich indentations.

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“…When those cracks propagate to the surface they lead to chipping. Edge cracks are likely introduced by the tensile component, accompanied with sink-in upon loading, and typically penetrate only straight down to a very small depth (Mound and Pharr, 2019). Occasionally chipping can be observed, even at smaller loads.…”

Section: The Mechanical Propertiesmentioning

confidence: 99%

Influence of Al2O3 Addition on Structure and Mechanical Properties of Borosilicate Glasses

et al. 2020

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Alkali-borosilicate glasses are one of the most used types of glasses with a high technological importance. In order to optimize glasses for diverse applications, an understanding of the correlation between microscopic structure and macroscopic properties is of central interest in materials science. It has been found that the crack initiation in borosilicate glasses can be influenced by changes in network interconnectivity. In the NBS2 borosilicate glass system (74.0SiO 2 -20.7B 2 O 3 -4.3Na 2 O-1.0Al 2 O 3 in mol%) two subnetworks are present, i.e., a silicate and a borate network. Increasing cooling rates during processing were found to improve glasses crack resistance. Simultaneously, an increase in the network interconnectivity accompanied by an increasing capacity for densification were noticed. Their individual contribution to the mechanic response, however, remained unclear. In the present study the borosilicate glasses were systematically modified by addition of up to 4.0 mol% Al 2 O 3 . Changes in the network connectivity as well as the short-and medium-range order were characterized using Raman and NMR spectroscopy. Both the Raman and the 11 B NMR results show that four-fold-coordinated boron is converted into three-fold-coordination as the Al 2 O 3 content increases. Additionally, 27 Al NMR experiments show that aluminum is dominantly present in four-fold coordination. Aluminum-tetrahedra are thus charge balanced by sodium ions and incorporated into the silicate network. Finally, nanoindentation testing was employed to link the inherent glass structure and its network configuration to the mechanical glass response. It was found that the glass softens with increasing Al 2 O 3 content, which enhances the crack resistance of the borosilicate glass.

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Nanoindentation of Fused Quartz at Loads Near the Cracking Threshold

Cited by 13 publications

References 45 publications

Indentation densification of fused silica assessed by raman spectroscopy and constitutive finite element analysis

Indentation densification of fused silica assessed by raman spectroscopy and constitutive finite element analysis

Conical Nanoindentation Allows Azimuthally Independent Hardness Determination in Geological and Biogenic Minerals

Influence of Al2O3 Addition on Structure and Mechanical Properties of Borosilicate Glasses

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