The acquisition of inertia by a moving crack


Tamar Goldman, Ariel Livne and Jay Fineberg

Racah Institute of Physics, Hebrew University of Jerusalem, Jerusalem 91904, Israel


We experimentally investigate the dynamics of \simple" tensile cracks. While within an effectively

infinite medium, a crack's dynamics perfectly correspond to inertia-less behavior predicted by linear

elastic fracture mechanics. Once a crack interacts with waves that it generated at earlier times,

this description breaks down. Cracks then acquire inertia and sluggishly accelerate. Crack inertia

increases with crack speed, v, and diverges as v approaches its limiting value. We show that these

dynamics are in excellent accord with an equation of motion derived in the limit of an in¯nite strip

(M. Marder, Phys. Rev. Lett. 66, 2484 (1991)).