6,332 research outputs found
Shape Memory Alloy Nanostructures With Coupled Dynamic Thermo-Mechanical Effects
Employing the Ginzburg-Landau phase-field theory, a new coupled dynamic
thermo-mechanical 3D model has been proposed for modeling the
cubic-to-tetragonal martensitic transformations in shape memory alloy (SMA)
nanostructures. The stress-induced phase transformations and thermo-mechanical
behavior of nanostructured SMAs have been investigated. The mechanical and
thermal hysteresis phenomena, local non-uniform phase transformations and
corresponding non-uniform temperature and deformations distributions are
captured successfully using the developed model. The predicted microstructure
evolution qualitatively matches with the experimental observations. The
developed coupled dynamic model has provided a better understanding of
underlying martensitic transformation mechanisms in SMAs, as well as their
effect on the thermo-mechanical behavior of nanostructures.Comment: 8 pages, 3 figure
Once again: Instanton method vs. WKB
A recent analytic test of the instanton method performed by comparing the
exact spectrum of the Lam potential (derived from representations
of a finite dimensional matrix expressed in terms of generators) with
the results of the tight--binding and instanton approximations as well as the
standard WKB approximation is commented upon. It is pointed out that in the
case of the Lam potential as well as others the WKB--related method
of matched asymptotic expansions yields the exact instanton result as a result
of boundary conditions imposed on wave functions which are matched in domains
of overlap.Comment: 10 pages, no figures. References list revised according to JHE
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