Following the award of an EPSRC grant for the research project

Writhing Structures: Nonlinear Modelling and Analysis of Advanced Post-Buckling Behaviour of Rods and Filaments

a 3-year postdoc position in Nonlinear Dynamics is available at UCL from November 2004.

The project concerns the application of nonlinear elastic rod theory to the large-deformation behaviour and stability of twisting, writhing, whirling and whipping rods and filaments. A particular focus will be on modern textile applications such as the stability of micro- and nanofibre spinning and the twist-stretch behaviour of (multi)plied yarns. Techniques used will be Nonlinear Modelling, Dynamical Systems Theory (exploiting the close mathematical relation between twisted rods and spinning rigid bodies), Numerical Continuation and Bifurcation Theory as well as Asymptotic and Multiscale Analysis.

The research will be carried out under the supervision of Gert van der Heijden and involves collaboration with a Visiting Fellow and with researchers at CSIRO, the Australian Commonwealth Scientific and Industrial Research Organisation, Textile & Fibre Technology Division, Geelong VIC, where experiments on plied yarns and spinning fibres will be carried out.

The Research Assistant will join an environment of active research into the nonlinear mechanics of such modern slender structures as space tethers, marine pipelines, supercoiling DNA molecules and collagen nanofibres.

A more detailed project abstract follows:

The aim of this work is firstly to develop a theoretical framework for dealing with the advanced nonlinear post-buckling behaviour of writhing and whirling rods, and secondly to use this theory for a unified and timely attack on a number of stability problems involving slender engineering structures. A rod is here modelled as a 1D structure, i.e., a space curve endowed with mechanical properties such as bending and torsional stiffnesses. Arclength along the rod thus plays a role analogous to time in a dynamical system, making possible the application of powerful techniques from Nonlinear Dynamics.

Recent work of the grantholder offers scope for considerable progress in our understanding of slender structures undergoing large deformations. Drawing on expertise from a range of sources, including industry, a combination of modelling, analysis and numerical work is proposed, aided by validation against experimental data. The techniques used will be the modern mathematical tools from Nonlinear Dynamics and Numerical Bifurcation Theory as well as Asymptotic and Multiscale Analysis. The work will give us a complete theory of plied structures such as textile yarn, currently poorly understood, and will tackle such structural stability problems as the pop-out of looped cable, the birdcaging of mooring rope and the snarling of transported textile yarn. All of these instabilities pose severe limitations on the practical range of operation of the structural member, and may lead to expensive and catastrophic failure. Contacts with UK industries will be used to disseminate the results of the research.

Applicants should have (or be about to complete) a PhD in Mathematics, Physics or Engineering with a strong Nonlinear Dynamics component. The starting salary will be in the range 19,460 - 22,507 pounds, plus 2,330 pounds London Allowance, according to experience. To apply, please send a full CV and the names and addresses of two referees, together with the Equal Opportunities Classification Form (to be found at to Richard Sharp, Department of Civil and Environmental Engineering, UCL, preferably by e-mail ( and no later than 15 October 2004. Informal enquiries may be directed to Gert van der Heijden at

Page last updated: 26 August 2004.

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