title: Key role of elastic vortices in the initiation of intersonic shear cracks.
abstract: Using the particle-based method of movable cellular automata, we analyze the initiation and propagation of intersonic mode II cracks along a weak interface. We show that the stress concentration in front of the crack tip, which is believed to be the mechanism of acceleration of the crack beyond the speed of shear waves, is due to the formation of an elastic vortex. The vortex develops in front of the crack during the short initial period of crack propagation. It expands and moves away from the crack tip and finally detaches from it. Maximum stress concentration in the vortex is achieved at the moment of detachment of the vortex. The crack can accelerate towards the longitudinal wave speed if the magnitude of shear stresses in the elastic vortex reaches the material shear strength before vortex detachment. We have found that for given material parameters, the condition for the unstable accelerated crack propagation depends only on the ratio of the initial crack length to its width (e.g., due to surface roughness).
authors.affiliation: Institute of Strength Physics and Materials Science, Russian Academy of Sciences, Tomsk, Russia.|Skolkovo Institute of Science and Technology, 143025 Moscow, Russia.|Tomsk State University, 634050 Tomsk, Russia.|Tomsk Polytechnic University, Tomsk, 634050 Tomsk, Russia.
authors.forename: Sergey G
authors.initials: SG
authors.lastname: Psakhie
authors.affiliation: Institute of Strength Physics and Materials Science, Russian Academy of Sciences, Tomsk, Russia.|Tomsk State University, 634050 Tomsk, Russia.
authors.forename: Evgeny V
authors.initials: EV
authors.lastname: Shilko
authors.affiliation: Tomsk State University, 634050 Tomsk, Russia.|Berlin University of Technology, 10623 Berlin, Germany.
authors.forename: Mikhail V
authors.initials: MV
authors.lastname: Popov
authors.affiliation: Tomsk State University, 634050 Tomsk, Russia.|Tomsk Polytechnic University, Tomsk, 634050 Tomsk, Russia.|Berlin University of Technology, 10623 Berlin, Germany.
authors.forename: Valentin L
authors.initials: VL
authors.lastname: Popov