An intrinsic nonlinear scale governs oscillations in rapid fracture

Abstract

When branching is suppressed, rapid cracks undergo a dynamic instability from a straight to an oscillatory path at a critical velocity $v_c$. In a systematic experimental study using a wide range of different brittle materials, we first show how the opening profiles of straight cracks scale with the size ${\ell }_{nl}$ of the nonlinear zone surrounding a crack's tip. We then show, for all materials tested, that $v_c$ is both a fixed fraction of the shear speed and, moreover, that the instability wavelength is proportional to ${\ell }_{nl}$. These findings directly verify recent theoretical predictions and suggest that the nonlinear zone is not passive, but rather is closely linked to rapid crack instabilities.

4 pages, 4 figures + supplementary information

References in corpus (4)

• Dynamic instabilities of fracture under biaxial strain using a phase field model
• The Breakdown of Linear Elastic Fracture Mechanics near the Tip of a Rapid Crack
• Weakly Nonlinear Theory of Dynamic Fracture
• Study of the branching instability using a phase field model of inplane crack propagation

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• Size selection of crack front defects: Multiple fracture-plane interactions and intrinsic lengthscales
• The dynamics of crack front waves in 3D material failure