Abstract: Crack extension paths are often irregular, producing rough fracture surfaceswhich have a fractal geometry.In this paper, crack tip motion along a fractal crack trace isanalysed. A fractal kinking model of the crack extension path is established to describe ir-regular crack growth. A formula is derived to describe the effects of fractal crack propagationon the dvnamic stross intensity factor and on crack velocity. The ratio of the dvnamic stressintensity factor to the applied stress intensity factor,K(l(t),V...