Intrinsic Nonlinear Scale Governs Oscillations in Rapid Fracture


  Tamar Goldman [1]  ,  Roi Harpaz [2]  ,  Eran Bouchbinder [2]  ,  Jay Fineberg [1]  
[1] The Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
[2] Chemical Physics Department, Weizmann Institute of Science, Rehovot 76100, Israel

When branching is suppressed, rapid cracks undergo a dynamic instability from a straight to an
oscillatory path at a critical velocity vc. 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 lnl of the
nonlinear zone surrounding a crack’s tip. We then show, for all materials tested, that vc is both a fixed
fraction of the shear speed and, moreover, that the instability wavelength is proportional to lnl. 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.