What happens to fracture energy in brittle fracture? Revisiting the Griffith assumption

Laboratory experiments involving unconfined compressive failure of borosilicate glass cylinders quantified the elastic strain energy released at failure and the size distribution of the resulting fragments. The data were carefully assessed for potential inaccuracies in surface-area calculation, the...

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Bibliographic Details
Published in:Solid earth (Göttingen) 2019-08, Vol.10 (4), p.1385-1395
Main Authors: Davies, Timothy R. H, McSaveney, Maurice J, Reznichenko, Natalya V
Format: Article
Language:English
Subjects:
Avalanches
Borosilicate glass
Brittle fracture
Compression
Cylinders
Earth science
Earthquakes
Energy
Energy (Physics)
Failure
Fracture mechanics
Fracture toughness
Fragments
Geodynamics
Griffith Irwin fracture
Mechanics
Observations
Particle size distribution
Potential energy
Rocks
Seismic activity
Size distribution
Strain
Surface area
Surface potential
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Summary:Laboratory experiments involving unconfined compressive failure of borosilicate glass cylinders quantified the elastic strain energy released at failure and the size distribution of the resulting fragments. The data were carefully assessed for potential inaccuracies in surface-area calculation, the contribution of energy from the compression machine relaxation during specimen failure, and possible variations in the specific fracture energy of the specimens. The data showed that more new surface area was created during the failures than would be possible if the long-standing assumption, which is that all the energy involved in creating new rock surface area in brittle material is taken up by the newly created surfaces as surface potential energy and is not available to do further work, were valid. We therefore conclude that the assumption is false. This conclusion is supported by independent data from a previous investigation whose authors did not pursue this particular application. Our result does not affect the validity of Griffith fracture mechanics and is significant only when large numbers of very fine fragments are created by brittle fracture, as in rock-avalanche motion and earthquake rupture, and are identified in particle-size distributions. In such situations our result is very significant to understanding fracture energetics.
ISSN:1869-9529
1869-9510
1869-9529
DOI:10.5194/se-10-1385-2019