Local waiting time fluctuations along a randomly pinned crack front

Area of Science:

• Materials Science
• Physics of Complex Systems
• Fracture Mechanics

Background:

• Interfacial crack propagation is crucial in material failure.
• Understanding fracture dynamics in heterogeneous materials is complex.
• Previous studies highlight the importance of disorder in fracture mechanics.

Purpose of the Study:

• To investigate the dynamics of interfacial crack propagation in a heterogeneous weak plane.
• To characterize the intermittent behavior and avalanche dynamics of crack front movement.
• To determine the statistical distributions governing crack velocity and burst size.

Main Methods:

• High-resolution fast camera imaging of crack propagation in a transparent Plexiglas block.
• Analysis of local pinning and depinning events by measuring waiting time fluctuations.
• Statistical analysis of crack front velocity and burst size distributions.

Main Results:

• Fracture front dynamics are governed by local, irregular avalanches with significant velocity fluctuations.
• Local front line velocity distribution follows a power law P(v) ∝ v⁻ eta (eta=2.55±0.15).
• Burst size distribution also follows a power law P(S) ∝ S⁻ gamma (gamma=1.7±0.1).
• Avalanche clusters become anisotropic above a disorder length scale (Ld ≈ 15 μm), yielding a roughness exponent H=0.66.

Conclusions:

• Crack propagation in heterogeneous materials is characterized by intermittent, avalanche-like behavior.
• Power-law distributions characterize crack velocity and burst sizes, indicating scale-invariant properties.
• The observed anisotropy and roughness exponent provide insights into the role of disorder in fracture.