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Is it possible to obtain (without modeling) the fracture strength of defect-free nanotubes or nanowires by tensile loading?

Submitted by Rod Ruoff on
research
fracture strength
pure tensile load

What boundary conditions would allow failure to occur in the gauge length and not at or near the clamps? One is not allowed (in suggesting ways of overcoming stress concentation at the clamps) to create defects in the nanotube or nanowire, to configure the region where failure will occur.  Thus, it is not possible (or is it?)  to create an analog of dog-bone specimens by, e.g., milling away part of the nanowire with a focused ion beam, etc., because this creates defects in the nanowire.

Plastic Deformation Recovery in Freestanding Nanocrystalline Aluminum and Gold Thin Films

Submitted by Taher A Saif on
research



Science 30 March 2007:
Vol. 315. no. 5820, pp. 1831 - 1834
DOI: 10.1126/science.1137580

Jagannathan Rajagopalan, Jong H. Han, M. Taher A. Saif*

In nanocrystalline metals, lack of intragranular dislocation sources leads to plastic deformation mechanisms that substantially differ from those in coarse-grained metals. However, irrespective of grain size, plastic deformation is considered irrecoverable. We show experimentally that plastically deformed nanocrystalline aluminum and gold films with grain sizes of 65 nanometers and 50 nanometers, respectively, recovered a substantial fraction (50 to 100%) of plastic strain after unloading. This recoverywas time dependent and was expedited at higher temperatures. Furthermore, the stress-strain characteristics during the next loading remained almost unchanged when strain recovery was complete.These observations in two dissimilar face-centered cubic metals suggest that strain recovery might be characteristic of other metals with similar grain sizes and crystalline packing.

Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.

Self-healing polymers - an introduction

Submitted by Jinglei Yang on
research

I'm now working on the preparation and characterization of self-healing polymers, a promising branch in materials science. The following is a general conception of this kind of materials system. (Pasted from our group website http://www.autonomic.uiuc.edu.) I may introduce some of my current work later.

Boundary Element Method for Hyperelastic Materials

Submitted by Mohsin Hamzah on
research

I am interested in using the Boundary Element Method for the hyperelastic materials. The objective of this work  is to simulate the behaviour of elastomeric or rubber-like materials parts. I am now in the derivation stage, and I intened to use Ogden constitutive model with this derivation.

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