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Ajeet Kumar's blog

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An asymptotic numerical method for continuation of spatial equilibria of special Cosserat rods

We present an efficient numerical scheme based on asymptotic numerical method for continuation of spatial equilibria of special Cosserat rods. Using quaternions to represent rotation, the equations of static equilibria of special Cosserat rods are posed as a system of thirteen first order ordinary differential equations having cubic nonlinearity. The derivatives in these equations are further discretized to yield a system of cubic polynomial equations.

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A thermo-elasto-plastic theory for special Cosserat rods

A general framework is presented to model coupled thermo-elasto-plastic deformations in the theory of special Cosserat rods. The use of the one-dimensional form of the energy balance in conjunction with the one-dimensional entropy balance allows us to obtain an additional equation for the evolution of a temperature-like one-dimensional field variable together with constitutive relations for this theory. Reduction to the case of thermoelasticity leads us to the well known nonlinear theory of thermoelasticity for special Cosserat rods.

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Effect of surface elasticity on extensional and torsional stiffnesses of isotropic circular nanorods

We present a continuum formulation to obtain simple expressions demonstrating the effects of surface residual stress and surface elastic constants on extensional and torsional stiffnesses of isotropic circular nanorods. Unlike the case of rectangular nanorods, we show that the stiffnesses of circular nanorods also depend on surface residual stress components. This is attributed to non-zero surface curvature inherent in circular nanorods.

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Unusual couplings in elastic tubes - negative poisson effect and overwinding on being stretched

We demonstrate intersting extension-torsion-inflation coupling in intrinsically twisted chiral tubes. In particular, we show that by tuning its intrinsic twist and the material constants, such tubes can show negative poison effect on being stretched. Similarly, such tubes can overwind initially when stretched - the same unusual behavior has been reported earlier when a DNA molecule is stretched.

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Research Associate/Postdoc position at IIT Delhi

Job title: Research Associate/Postdoc

Minimum qualification: PhD in Solid Mechanics/Mathematics

Research area: Thermoelastic Modeling of nano and Contunuum Rods – A Molecular Approach

Salary: Rs 36000 per month + 30% HRA

Walk in interview: 3rd of Nov 2016 in Department of Applied Mechanics, IIT Delhi

Contact person: Prof. Ajeet Kumar,

See the attachment for more details.

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PhD/Postdoc position at IIT Delhi

A PhD/Postdoc position is available for Indian nationals in my group to work in the broad area of "Molecular origin of elastic/plastic deformations in nanorods". This is a collaborative project with Germany and may require a semester or two stay in Germany. The PhD applicant should have good background in mathematics and solid mechanics. The postdoc candidate should preferably also be familiar with molecular modeling of materials.

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Effect of material nonlinearity on spatial buckling of nanorods and nanotubes

You may be interested in reading our following article: We show the importance of incorporating material nonlinearity for accurate simulation of nanorods and nanotubes. The linear material laws are shown to give completely erroneous results. The nonlinear material laws for nanorods were obtained using the recently proposed "Helical Cauchy-Born rule". We also discuss how surface stress affects buckling in such nanostructures.

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A one-dimensional Rod Model for Carbon Nanotubes

We recently published a paper in International Journal of Solids and Structures titled "A rod model for three dimensional deformations of single walled carbon nanotubes".(paper attached)

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