Crack-Tip Strain Field in Supershear Crack of Elastomers.

We characterize the crack-tip strain field in the high-speed (supershear) crack in the elastomers propagating faster than the shear wave speed of sound ( C s ). The dependence of steady-state crack velocity ( V ) on input tearing energy exhibits a crossover at V ≈ C s between the subsonic ( V < C s ) and supershear cracks ( V > C s ). Several features of the crack-tip strain field such as strain-magnitude, extent boundary, and singularity exponent also change substantially accompanying the transition from subsonic to supershear cracks. The definite crossover of these characteristics at V ≈ C s reflects the variations in the crack-growth mechanism: The inertia effect comes into play in the supershear crack. We also demonstrate that the azimuthal distribution of the local crack-tip strain has a close correlation with the macroscopic crack-tip shape, regardless of the regime of V .