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Do Plastic Zones Form at Crack Tips in Silicate Glasses?



Jose Lopez-Cepero, Sheldon M. Wiederhorn, Theo Fett, Jean-Pierre Guin


In a number of recent studies, the claim has been made that silicate glasses fracture by the formation, growth and coalescence of cavities, in the same way that metals do but at a much smaller scale. Evidence for cavity formation comes from the examination of side surfaces of fracture mechanics specimens, at the point where the crack intersects the free surface. Carried out using an atomic force microscope (AFM), such measurements demonstrate finite depressions in the regions that are supposedly located in front of crack tips in silicate glasses. These depressions were interpreted as cavities. In this paper, we summarize experimental results obtained using an atomic force microscope to characterize the fracture surfaces themselves. The experimental results demonstrate the absence of the kind of residual damage that could be interpreted as cavity formation. We also observe cracks moving in glass and show that the kinds of features reported as cavities actually occur within and not in front of the moving crack. A simulation of an AFM probe passing over a crack in a rough surface strongly suggests that the features identified as cavities are in fact associated with the crack and are due to the roughness of the specimen surface. Our results support the view that cracks in glass propagate by brittle fracture; bond-snapping appears to be the dominant feature of crack growth in silicate glasses.
International Journal of Materials Research


atomic force microscopy, crack growth, fracture surfaces, glass, simulation


Lopez-Cepero, J. , Wiederhorn, S. , Fett, T. and Guin, J. (2007), Do Plastic Zones Form at Crack Tips in Silicate Glasses?, International Journal of Materials Research (Accessed April 16, 2024)
Created December 12, 2007, Updated October 12, 2021