Measurements of Impact-Induced Fracto-Emission from Soda-Lime Glass and Simultaneous Observation of the Cracking Process by High-Speed Photography

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In order to study the fracto-emission mechanism, measurements of impact-induced fracto-emission (FE) of negatively charged particles from a soda-lime silicate glass were conducted at different impact energies, with simultaneous observation of the fracture mode by high-speed photography. The FE signals and their integrated values during the impact period were found to be dependent on the impact energy, E. For E ≤ 150 mJ, surface damage occurred around the impact track and the maximum fracto-emission signal was observed just after the indenter contacted the glass surface. The integrated FE signal intensity IFE increased according to a 0.60 power law for the impact energy. For E > 150 mJ, the glass body broke into several pieces and the integrated signal intensities were greater than those for the surface fractures. The IFE values increased according to a 0.84 power law for the impact energies. The FE signal patterns were compared with the high-speed camera photo-sequences. The dependence of IFE on E could be explained in terms of the relationship between the line crack length at the indention and the impact energy. The FE signals during impact were attributed to the contact electric potential of the indenter and the glass surface, crack generation, and the scattering of fragments.