title: Universality classes in constrained crack growth.
abstract: Based on an extension of the fiber bundle model we investigate numerically the motion of a crack front through a weak plane separating a soft and an infinitely stiff block. We find that there are two regimes. At large scales the motion is consistent with the pinned elastic line model and we find a roughness exponent equal to 0.39±0.04 characterizing it. At smaller scales, coalescence of holes dominates the motion, giving a roughness exponent consistent with 2/3, the gradient percolation value. The length of the crack front is fractal in this regime. Its fractal dimension is 1.77±0.02, consistent with the hull of percolation clusters, 7/4. This suggests that the crack front is described by two universality classes: on large scales, the pinned elastic line one and on small scales, the percolation universality class.
authors.affiliation: Department of Physics, Norwegian University of Science and Technology, N-7491 Trondheim, Norway.
authors.forename: Knut S
authors.initials: KS
authors.lastname: Gjerden
authors.forename: Arne
authors.initials: A
authors.lastname: Stormo
authors.forename: Alex
authors.initials: A
authors.lastname: Hansen