On the finite opening of intersonic shear cracks

Recent molecular dynamics simulations of dynamic crack propagation have shown that there is a finite crack opening for a shear crack propagating at a sub-Rayleigh speed, but the crack opening becomes significantly smaller once the crack tip velocity exceeds the shear wave speed. To understand this difference between the crack opening for sub-Rayleigh and intersonic shear cracks, we develop in this paper a finite deformation continuum theory incorporating the linear harmonic potential to describe the deformation of a crack in a solid with triangular lattice structure. Using the asymptotic method developed by Knowles [Eng. Fract. Mech. 15 (1981) 469], we show that even after the geometric nonlinearity of finite deformation is accounted for, the intersonic shear cracks have a vanishing crack opening displacement. [Copyright &y& Elsevier]