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Home Focus The role of disorder in fracture

The role of disorder in fracture

may 2013

Some materials like glasses break abruptly. Complex materials like bones and seashells develop many small damaged regions (microcracks) before breaking. These microcracks happen with a broad, scale-invariant distribution of sizes reminiscent of earthquakes and crackling noise. But this can not be due to a phase transition, focus_zapperi_maggio2013_gifbecause as the system size goes to infinity the strength of disordered materials goes to zero. ‘Smaller is stronger’ really means ‘large is weak’ here — a rare, large damaged zone will cause an infinite system to fail atarbitrarily low stress – hence nothing else breaks. Researchers at IENI-CNR in collaboration with Cornell University  show that these precursor fracture events are due to ‘finite-size criticality’. At short length scales, all materials are sensitive to disorder; at long length-scales all behave like glass. Researchers describe the smooth, finite-size crossover between these two regimes quantitatively using universal scaling functions and their leading corrections. Bones, seashells, and modern composite materials are tough because of this distributed damage — which we finally now understand clearly.

Ashivni Shekhawat, Stefano Zapperi, and James P. Sethna
From Damage Percolation to Crack Nucleation Through Finite Size Criticality
Phys. Rev. Lett. 110, 185505 (2013)

See also the viewpoint by Elisabeth Bouchaud

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