Letter/Communication
A matter of scale - Reply
American scientist, Vol.89(5), pp.388-388
Sep 2001
Abstract
Reply to letter from Cinna Lomnitz, "A Matter of Scale"
Dr. Barsoum replies:
The point Dr. Lomnitz raises is certainly very interesting. Indeed, Johannes Weertman and Julia R. Weertman start their book Elementary Dislocation Theory by noting that "dislocations play a commanding role in the grandest of all deformations on Earth: the upheavals that have produced the mountain ranges and the continents themselves." They then go on to state how dislocations in grains of ice allow the plastic flow of glaciers, etc. As we pointed out, the similarities in the deformations, at both the atomic and macroscopic levels, in ice and the MAX phases are uncanny Since we made that connection, our understanding of the deformation of the MAX phases has deepened considerably.
The analogy, however, breaks down if the scale is no longer atomic. For example, the formation of macroscopic kink bands in geologic formations, or playing cards for that matter, is not from the motion of dislocations, but rather occurs as a consequence of their layering. Once dislocations are removed from the picture, they cannot be responsible for why fractures stop in tectonic plates; the answer must lie elsewhere. The point of critical importance is that the MAX phases do not behave like any other layered material, precisely because the dislocation walls that form prevent further damage. That said, I am still thrilled to have scientists from totally different fields find our work useful or applicable.
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Details
- Title
- A matter of scale - Reply
- Creators
- Michel W Barsoum - Drexel University, Materials Science and Engineering
- Publication Details
- American scientist, Vol.89(5), pp.388-388
- Number of pages
- 1
- Resource Type
- Letter/Communication
- Language
- English
- Academic Unit
- Materials Science and Engineering
- Identifiers
- 991021930812504721