Hertzian testing of ceramics

Roberts, S.G.

doi:10.1179/096797800680686

Cited by 6 publications

(3 citation statements)

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“…Using simulated crack distributions, Roberts [34] demonstrated that the Hertzian test does not select all crack sizes equally. A combination of the elastic properties of the indenter, those of the surface under test, and the radius of the indenting sphere leads to an optimum crack depth for which the technique is most sensitive.…”

Section: Discussionmentioning

confidence: 99%

The mechanical properties of float glass surfaces measured by nanoindentation and acoustic microscopy

Goodman¹,

Derby²

2011

Acta Materialia

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We have combined nanoindentation with measurements of Rayleigh wave velocity to determine the elastic properties of the surfaces of a commercial soda-lime float glass and found significant differences between the mechanical behaviour of the side in contact with the air and that in contact with tin. By using two measurement methods we have obtained the two independent elastic constants of glass (assuming surface isotropy and homogeneity). The air-side has a Young's modulus E = 81.3 ± 0.5 GPa and Poisson's ratio m = 0.22 ± 0.01, which is significantly different from the tin-side values of E = 79.6 ± 1.0 GPa and m = 0.187 ± 0.015. The Young's modulus of both surfaces is significantly greater than the bulk value reported by the manufacturer of 73 GPa and Poisson's ratio smaller than the reported value of 0.23. The tin-side, having a lower Young's modulus than the air-side, is in the opposite sense to the reported increase in stiffness of bulk float glass with increasing levels of tin doping. We critically review the possible mechanisms for the difference in mechanical properties between the tin-and air-sides of a float glass sheet and produce quantified predictions of likely changes from each mechanism. From this we conclude that no individual mechanism can account for the magnitude of the difference we have measured.

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Section: Discussionmentioning

confidence: 99%

The mechanical properties of float glass surfaces measured by nanoindentation and acoustic microscopy

Goodman¹,

Derby²

2011

Acta Materialia

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“…In several cases chip scars on window glass specimens exhibited additional fracture (Fig. 5b), while quartz glass specimens displayed cracks similar to Hertzian quasi-cones 641 * The width is larger than the height [12].…”

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confidence: 97%

Glass fracture in edge flaking

et al. 2007

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Fracture resistance of technical quartz and normal window glasses was investigated in testing polished rectangular parallelepipeds by edge flaking their long edges with Rockwell and Vickers indenters (EF method) and by scratching the specimen surface with a Rockwell indenter followed by flaking its edge (S+EF method). It was established that the fracture of those glass specimens in their edge flaking with a Rockwell indenter was started with the formation of a Hertzian ring crack and their corresponding chip scars had the form of Hertzian "quasi-cones." Fractographic data were used in analysis of test results.Introduction. One can hardly find any field of human activities where silicate glasses are not in use. Despite brittleness and inconsiderable deformability inherent in such materials, they turn out indispensable for many technical and other fields of application. This gives impetus to studies on the mechanical behavior of those materials and, in particular on their ability to resist fracture. Their fracture toughness was evaluated by different methods, including fracture of the specimen surface with sharp and blunt indenters [1]. As a result, a great body of experimental data was accumulated, which contributed to the enhancement of glass capabilities and to the gain in reliability of glass items in operation.As was mentioned earlier [2], glass is a material very complicated for comprehension. Its fracture behavior is still not clearly understood, and the choice of an optimum method for determining its fracture resistance is unresolved as yet. Therefore, the investigation of glass fracture in flaking the edges of rectangular parallelepipeds with standard indenters was carried out, which turned out to be an effective approach to studying different ceramics and allowed new information on their behavior under loading to be obtained [3].Materials and Methods. This investigation was targeted for getting the general notion of glass behavior in its edge flaking. For this purpose the two types of glass varying in their compositions were taken: "normal" (silica contents are less than 70-75%) and "anomalous", i.e., containing up to 99.9% silica [4]. The mechanical behavior of the former is believed to be similar to the behavior of other brittle materials, while glass of the second type exhibits certain differences associated with its structure. Therefore, both technical quartz glass, containing about 90-95% silica doped with Na 2 O and Al 2 O 3 , and normal window glass with about 72% silica were studied. Experiments were also performed on industrial hardened sheet glass. Those glasses were manufactured commercially, thus, their correct compositions, being "know-how" of enterprises, are unknown.The tests made use of specimens in the form of polished rectangular beams of standard sizes (3 4 × -mm

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“…Before this higher load is reached the fracture of the sand particles may occur, thereby preventing that load from being attained. Roberts et al [28,29] have investigated the effect of compressive residual stress on the fracture load in a Hertz indentation test indenting glass with a 10 mm diameter glass ball. They found that as the surface compressive stress increased from 0 (nominally "stress free") to 500 MPa the minimum fracture load increased by more than an order of magnitude.…”

Section: Comparison Of Crack Diameters With Hertz Impact Theorymentioning

confidence: 99%