iMechanica - "Persistence of a pinch in a pipe" by L. Mahadevan, Ashkan Vaziri and Moumita Das - Comments

wrongly estimated: persistence length of a carbon nanotube

Henry Tan — Thu, 15 Feb 2007 14:22:06 -0500

In the discussion section of the paper, the persistence length of a carbon nanotube was estimated wrongly.

For a carbon nanotube, the Young's modulus E defined in this paper is not a constant. The material constant is E*R*t. Therefore, for carbon nanotube, the persistence length lp does not scale to 4.4*R^(3/2)/t^(1/2)!

However this equation, which does not apply to the case of carbon nanotube, was used for the estimation of the persistent length of a carbon nanotube (R~2, t~0.2nm). Therefore the conclusion that the persistence is lp~30nm is wrong.

The pdf file is now attached.

Ashkan Vaziri — Wed, 14 Feb 2007 10:59:45 -0500

Thank you very much for your interest. I have now uploaded the pdf file of the paper.

The link does not work.

Haimin Yao — Wed, 14 Feb 2007 09:50:40 -0500

The link does not work.

"Persistence of a pinch in a pipe" by L. Mahadevan, Ashkan Vaziri and Moumita Das

Ashkan Vaziri — Tue, 13 Feb 2007 12:24:41 -0500

The response of low-dimensional solid objects combines geometry and physics in unusual ways, exemplified in structures of great utility such as a thin-walled tube that is ubiquitous in nature and technology. Here we provide a consequence of this confluence of geometry and physics in tubular structures: our analysis shows that the persistence of a localized pinch in an elastic pipe whose effect decays as an oscillatory exponential with a persistence length that diverges as the thickness of the tube vanishes, which we confirm using simulations and simple experiments. The result is more a consequence of geometry than material properties, and is thus equally applicable to carbon nanotubes as it is to oil pipelines. The full article is attached.