Dynamics of microcracks and time dependences of surface deformation of a heterogeneous body (granite) under an impact

The dynamics of fractoluminescence flashes and the time dependences of surface deformation of granite with different sizes of feldspar grains under an impact on samples by a metal pin have been studied with a 10 ns resolution. A band at ??1.9 eV has been observed in the fractoluminescence spectra, which means that, under the influence of mechanical stresses, Si-O-Si bonds are broken and ?? SiO^?? free radicals are formed. The fractoluminescence has the form of flashes with a duration of ??10 ns. It has been assumed that each of them corresponds to the nucleation of a microcrack. From the flash intensities and the elastic wave velocity, the linear size of microcracks has been estimated to be from ??8 to 30 ??m. Microcracks are mainly generated during passage of a deformation wave through feldspar grains. An impact causes the appearance of eigenvibrations of the entire sample, and cracking of grains gives rise to eigenvibrations of grains.