Biomedical subjects

L P Kubin

Publications and source records attributed to L P Kubin.

6 recordsLinked to original sources

PubMed2006

Dislocation patterns and the similitude principle: 2.5D mesoscale simulations.

During plastic flow of crystalline solids, dislocations self-organize in the form of patterns, with a wavelength that is inversely proportional to stress. After four decades of investigations, the origin of this property is still under discussion. We show that dislocation patterns verifying the principle of similitude can be obtained from dynamics simulations of double slip. These patterns are formed in the presence of long- and short-range interactions, but they are not significantly modified when only short-range interactions are present. This new insight into dislocation patterning phenomena has important implications regarding current models.

Journal Article↗

PubMed2002

From dislocation junctions to forest hardening.

The mechanisms of dislocation intersection and strain hardening in fcc crystals are examined with emphasis on the process of junction formation and destruction. Large-scale 3D simulations of dislocation dynamics were performed yielding access for the first time to statistically averaged quantities. These simulations provide a parameter-free estimate of the dislocation microstructure strength and of its scaling law. It is shown that forest hardening is dominated by short-range elastic processes and is insensitive to the detail of the dislocation core structure.

Journal Article↗

PubMed2002

Comment on "Portevin-Le Chatelier effect".

Instabilities of plastic flow in alloys and the associated deformation patterns are currently attracting a lot of attention. We comment on a recent investigation by Franklin et al. [Phys. Rev. E 62, 8195 (2000)] on one such type of instability, the Portevin-Le Chatelier effect, attempting to clarify a few points about the instability mechanism as well as the reported experimental results.

Journal Article↗

PubMed2001

Multifractal burst in the spatiotemporal dynamics of jerky flow.

The collective behavior of dislocations in jerky flow is studied in Al-Mg polycrystalline samples subjected to constant strain rate tests. Complementary dynamical, statistical, and multifractal analyses are carried out on the stress-time series recorded during jerky flow to characterize the distinct spatiotemporal dynamical regimes. It is shown that the hopping type B and the propagating type A bands correspond to chaotic and self-organized critical states, respectively. The crossover between these types of bands is identified by a large spread in the multifractal spectrum. These results are interpreted on the basis of competing scales and mechanisms.

Journal Article↗

PubMed1999

Crossover from chaotic to self-organized critical dynamics in jerky flow of single crystals.

We report a crossover from chaotic to self-organized critical dynamics in the Portevin-Le Chatelier effect in single crystals of Cu-10% Al in tension as a function of the applied strain rate. For low and intermediate strain rates, we provide an unambiguous support for the existence of chaotic stress drops by showing the existence of a finite correlation dimension and a stable positive Lyapunov exponent. A surrogate data analysis rules out the possibility that the time series is due to a power law stochastic process. As the strain rate is increased, the distributions of stress drops and the time intervals between the stress drops change from peaked to power law type with an exponent close to unity reminiscent of self-organized critical state. A scaling relation compatible with self-organized criticality relates the various exponents. The absence of a finite correlation dimension and a stable positive Lyapunov exponent at the highest strain rate also supports the evidence of crossover.

Journal Article↗

PubMed1978

Discussion on the limitations of "in situ" deformation experiments in a high voltage electron microscope.

Radiation damage as well as surface effects are two possible limitations of the "in situ" straining experiment in a high voltage electron microscope. The optimum experimental conditions and a few approximate criteria to be fulfilled are described, using the data presently available. In these criteria are involved the operating conditions of the microscope, the temperature, the geometry and properties of the material investigated.

Electrons↗