title: 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 ℓ(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 ℓ(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.
authors.affiliation: The Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
authors.forename: Tamar
authors.initials: T
authors.lastname: Goldman
authors.forename: Roi
authors.initials: R
authors.lastname: Harpaz
authors.forename: Eran
authors.initials: E
authors.lastname: Bouchbinder
authors.forename: Jay
authors.initials: J
authors.lastname: Fineberg