The Mechanics of a Chain or Ring of Spherical Magnets

Cameron L. Hall, Dominic Vella, Alain Goriely

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


Strong magnets, such as neodymium-iron-boron magnets, are increasingly being manufactured as spheres. Because of their dipolar characters, these spheres can easily be arranged into long chains that exhibit mechanical properties reminiscent of elastic strings or rods. While simple formulations exist for the energy of a deformed elastic rod, it is not clear whether or not they are also appropriate for a chain of spherical magnets. In this paper, we use discrete-to-continuum asymptotic analysis to derive a continuum model for the energy of a deformed chain of magnets based on the magnetostatic interactions between individual spheres. We find that the mechanical properties of a chain of magnets differ significantly from those of an elastic rod: while both magnetic chains and elastic rods support bending by change of local curvature, nonlocal interaction terms also appear in the energy formulation for a magnetic chain. This continuum model for the energy of a chain of magnets is used to analyze small deformations of a circular ring of magnets and hence obtain theoretical predictions for the vibrational modes of a circular ring of magnets. Surprisingly, despite the contribution of nonlocal energy terms, we find that the vibrations of a circular ring of magnets are governed by the same equation that governs the vibrations of a circular elastic ring. Copyright © by SIAM.
Original languageEnglish (US)
Pages (from-to)2029-2054
Number of pages26
JournalSIAM Journal on Applied Mathematics
Issue number6
StatePublished - Jan 2013
Externally publishedYes

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): KUK-C1-013-04
Acknowledgements: This work was supported by Award KUK-C1-013-04, made by King Abdullah University of Science and Technology (KAUST).The first author's work was supported by grant EP/I017070/1 from the Engineering and Physical Sciences Research Council. The third author is a Wolfson Royal Society Merit Holder and was supported by a Reintegration grant under EC Framework VII.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.


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