SELF-SIMILAR CRACK-GENERATION EFFECTS IN THE FRACTURE PROCESS IN BRITTLE MATERIALS

Using acoustic-emission data banks we have computed time and space cor relation functions for the purpose of investigation of crack-propagati on self-similarity during the fracture process in brittle materials. I t is shown that the whole fracture process may be represented as a two -stage process. In the first stage, the crack propagation is uniform a nd uncorrelated in space, having a time spectral density of the white- noise type and a correlation fractal dimension approximately equal to that of 3D Euclidean space. In the second stage, this fractal dimensio n decreases significantly, reaching the value of 2.2-2.4, characterist ic for the fracture surfaces, while the time spectral density exhibits a significant low-frequency increase becoming of 1/f-noise type. The resulting fractal shows no multifractal behaviour, appearing to be a s ingle fractal.