Lu, X;
Rawson, SD;
Withers, PJ;
(2018)
Effect of hydration and crack orientation on crack-tip strain, crack opening displacement and crack-tip shielding in elephant dentin.
Dental Materials
, 34
(7)
pp. 1041-1053.
10.1016/j.dental.2018.04.002.
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Abstract
Objectives To quantify the extent of crack-tip plasticity, crack opening displacement (COD) and crack bridging for crack growth perpendicular (HAH) and parallel (RAR) to the tubules in elephant dentin under both hydrated and dry conditions to better understand their influence on intrinsic and extrinsic toughening during crack growth. Methods Compact tension test-pieces were prepared from a tusk of African elephant ivory. Crack-tip strain mapping and COD measurements by digital image correlation (DIC) technique were made under incremental loading and unloading of cracks for hydrated and dry dentin of different orientations. Results For the RAR test-piece the plastic zones were significantly larger in the hydrated condition compared to when dry. By contrast, the plastic strains in the HAH test-piece were negligible in both wet and dry conditions. In the RAR condition the crack front was broken up into overlapping longitudinal ‘fingers’ with crack bridging regions in between, the ligaments extending 400 μm behind the crack front in the dry case. This could only be seen in 3D by X-ray CT. Extrinsic shielding reduces the crack-tip stresses by 52% and 40% for hydrated and dry RAR test-pieces respectively. No significant bridging was found in the HAH case. Significance For crack growth parallel to the tubules, collagen plasticity determines the intrinsic toughening, whereas microcracking from the tubules governs extrinsic shielding via ligament bridging, which is maintained further behind the crack in the hydrated case. For cracks grown perpendicular to the tubules, neither toughening mechanisms are significant.
| Type: | Article |
|---|---|
| Title: | Effect of hydration and crack orientation on crack-tip strain, crack opening displacement and crack-tip shielding in elephant dentin |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1016/j.dental.2018.04.002 |
| Publisher version: | https://doi.org/10.1016/j.dental.2018.04.002 |
| Language: | English |
| Additional information: | This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/ |
| Keywords: | Science & Technology, Life Sciences & Biomedicine, Technology, Dentistry, Oral Surgery & Medicine, Materials Science, Biomaterials, Materials Science, Ivory, Moisture, Crack-tip plasticity, Intrinsic and extrinsic toughening, Strain, Bridging, Finger crack, DIGITAL IMAGE CORRELATION, MECHANICAL-PROPERTIES, FRACTURE-TOUGHNESS, TOUGHENING MECHANISMS, TUBULE ORIENTATION, BOND STRENGTHS, IVORY, DEFORMATION, PLASTICITY, RESISTANCE |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Chemical Engineering |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10081902 |
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