Fig. 2. Comparing theoretical predictions of supershear crack velocities with numerical simulations and experimental measurements.

(A) Top: Spatially uniform τ₀ and nonuniform τ_p profiles are considered in simulations. The imposed τ₀/τ_p profiles are shown. Bottom: Colors represent the crack velocities C_f(l) corresponding to the stress profiles in the top panel. τ_p is low, dashed lines, near the point of nucleation (l/l₀ = 0) and increases at distances 50 for τ₀/τ_p > 0.2 and at l/l₀ = 130 for τ₀/τ_p = 0.2 (red). Black solid lines denote predictions of Eq. 1. For sufficiently low τ₀/τ_p (red example), two solution branches to Eq. 1 exist (dashed line shows the unstable solution). (B) Top: Profiles of the measured shear stress τ₀ and estimated interfacial strength τ_p in experiments. Bottom: Measured rupture velocities for rupture events with stresses shown in the top panel. Theoretical predictions according to Eq. 1 are shown (solid lines); average τ₀ values are used, l₀ = μГ/${\mathrm{\tau }}_{\mathrm{p}}^2$ = 2 mm. Dashed lines correspond to the error estimates of l₀ and τ_p. (C) C_f, measured at l = 120 mm (averaged over ±10 mm), for multiple experiments is plotted with respect to the measured τ₀ profiles averaged over the same interval. Solid dots and open circles indicate experiments performed with dry and boundary-lubricated interfaces, respectively. Black lines are the theoretical predictions with the estimated errors.