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Title: Universality class of dislocation avalanches in microcrystals
Plain: Small metal crystals deform in sudden jumps called avalanches, whose sizes follow a power law, much like earthquakes. Whether these jumps obey the same simple theory as other avalanche systems, and what sets the largest size, is unsettled.
Precise: Compression of micropillars (Dimiduk et al. 2006) and acoustic emission in ice and metals give slip-size distributions $P(S) \sim S^{-\tau} \operatorname{exp}(-S/S_{0})$ with $\tau \sim 1.5 \text{ to } 1.6$. Determine whether the critical behavior is mean-field depinning ($\tau = 3/2, S_{0} \sim (\sigma_{c} - \sigma)^{-2}$), a distinct class set by long-range dislocation interactions, or criticality without a tuning parameter, and how $\tau$ depends on crystal structure (FCC versus BCC) and temperature. An answer is a classification with $\tau$, cutoff scaling and average avalanche shape.
Settled by: Stress-resolved avalanche statistics and avalanche shapes from experiments and 3D dislocation dynamics agreeing on exponents and cutoff scaling.
Kind: well-posed
Answer type: classification
References: (empty)
Literature status: contested
Status note: (empty)
Posed since: 2001