Indentation densification of fused silica assessed by raman spectroscopy and constitutive finite element analysis. Issue 5 (26th January 2020)

• Record Type: Journal Article
• Authors: Bruns, Sebastian; Uesbeck, Tobias; Fuhrmann, Sindy; Tarragó Aymerich, Mariona; Wondraczek, Lothar; de Ligny, Dominique; Durst, Karsten
• Is Part Of: Journal of the American Ceramic Society. Volume 103:Issue 5(2020)
• Page Start: 3076
• Page End: 3088
• Publication Date: 2020-01-26
• Subjects: densification -- drucker‐prager‐cap plasticity -- finite element analysis -- fused silica -- indentation -- Raman Spectroscopy; Ceramics -- Periodicals; 620.1405
• DOI: 10.1111/jace.17024
• Languages: English
• ISSNs: 0002-7820

Abstract

Abstract: 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.