An appreciation of Alan Cottrell

Lindsay Greer and Frans Spaepen pay their tributes to Alan Cottrel in PNAS:

It was his lifelong ambition to bring to metallurgy, a field rich in observations but still mostly phenomenological in method, the quantitative and predictive rigor of the recent developments in atomic-scale physics.

His work on dislocations was a first success in this endeavor. The dislocation had been introduced as a theoretical concept in 1934 to explain the ease of plastic flow in crystals: moving a line defect that localizes shear
deformation requires a much lower stress than uniform shearing of the crystal planes. The concept was only gradually accepted. Even though dislocations provided key insights into mechanical behavior and crystal growth, it was only in 1956 that electron microscopy produced the first direct images of moving dislocations. In the late 1940s, Cottrell showed that dislocation theory could be used to make quantitative predictions.

A very nice piece!

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