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Movie of an expanding ring experiment

Ravi-Chandar's picture

I have posted a movie showing a ring expansion experiment. A thin aluminum ring is made to expand through electromagnetic interaction at strain rates of about 10^4 per second. As the strain increases, numerous necks and fragments appear. Multiple fragments are developed; further details are in the journal paper. This movie is posted on the blog associated with the International Journal of Fracture.


Teng Li's picture


I enjoyed viewing the movie and will look into details of the paper. I'd like to bring up some related research we've been working on.

Under tension, a thin metal film bonded to a polymer substrate can form multiple pre-rupture necks. This is because the constraint of the substrate to the strain localization in the thin metal film.  Our FEM study on the multiple necking of thin metal films on polymer substrates are available here and here.

Recently, Xue and Hutchinson reported substantial increases in necking limits and consequent energy absorption can be achieved in metal-elastomer bilayers for both quasi-static and dynamic stretching.

While the role of inertia in an expanding ring is analogous to that of the polymer substrate, we are unaware of any experimental observation of multiple necks in thin metal films on polymer substrate.  Maybe the experts in experiment can point out any available results or devise experiments to demonstrate.



Nanshu Lu's picture

Hi, Ravi, it is very fantastic work. I'm so exited to see the multiple necks in your Al ring. Thank you very much to share with us.

Teng used to work in the same group of mine and he did very good jobs on thin metal film multiple necking calculation and prediction. I am now doing tensile experiments on Cu-Kapton bilayer thin strip and hope to see the multiple necks in thin metal films as well. We were cheerful to see your results and the SEM figure provided here by Rongmei Niu, which seems quite like multiple necks.

I need to learn more about the mechanism on the forming of metal multiple necking.

Zhenyu Xue's picture

Hi Ravi,

Thanks for sharing. Very nice paper.

I'd like to introduce a paper to be published in JMPS:

Z. Xue, A. Vaziri and J.W. Hutchinson, "Material aspects of dynmaic neck retardation", JMPS, in press, 2007.

In the paper, an analytical model so-called two-state model was developed which is capable of capturing most of the parametric dependencies on dyanmic necking development. FEM calculations have also been carried out to systematically investigate the dynamic neck retardation of a metal bar (ring) under high strain-rate stretching.

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