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Register a new userEffective dimensionality of the Portevin - Le Chatelier effect
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Added by
Arnomitra Chatterjee
Publication date
2009
fields
Physics
and research's language is
English
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Tensile tests have been carried out by deforming polycrystalline samples of substitutional Al-2.5%Mg alloy at room temperature at a range of strain rates. The Portevin - Le Chatelier (PLC) effect was observed. From an analysis of the experimental stress versus time series data we have inferred that the dynamics of the PLC effect in a local finite time is controlled by a finite number of degrees of freedom and this effective dimension becomes reduced with increasing strain.
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The scaling behavior of the Portevin-Le Chatelier (PLC) effect is studied by deforming a substitutional alloy, Al-2.5%Mg and an interstitial alloy, low carbon steel (0.15%C, 0.33%Mn, 0.04%P, 0.05%S, 0.15%Si and rest Iron) at room temperature for a wide range of strain rates. To reveal the exact scaling nature, the time series data of true stress vs. time, obtained during the tensile deformation (corrected for drift due to strain hardening by polynomial fitting method), are analyzed by two complementary methods: the standard deviation analysis and the diffusion entropy analysis. From these analyses we could establish that in the entire span of strain rates, PLC effect showed Levy walk type of scaling property.
The plastic deformation of dilute alloys is often accompanied by plastic instabilities due to dynamic strain aging and dislocation interaction. The repeated breakaway of dislocations from and their recapture by solute atoms leads to stress serrations and localized strain in the strain controlled tensile tests, known as the Portevin-Le Chatelier (PLC) effect. In this present work, we analyse the stress time series data of the observed PLC effect in the constant strain rate tensile tests on Al-2.5%Mg alloy for a wide range of strain rates at room temperature. The scaling behaviour of the PLC effect was studied using two complementary scaling analysis methods: the finite variance scaling method and the diffusion entropy analysis. From these analyses we could establish that in the entire span of strain rates, PLC effect showed Levy walk property. Moreover, the multiscale entropy analysis is carried out on the stress time series data observed during the PLC effect to quantify the complexity of the distinct spatiotemporal dynamical regimes. It is shown that for the static type C band, the entropy is very low for all the scales compared to the hopping type B and the propagating type A bands. The results are interpreted considering the time and length scales relevant to the effect.
Tensile tests were carried out by deforming polycrystalline samples of Al-2.5%Mg alloy at room temperature in a wide range of strain rates where the Portevin-Le Chatelier (PLC) effect was observed. The experimental stress-time series data have been analyzed using the recurrence analysis technique based on the Recurrence Plot (RP) and the Recurrence Quantification Analysis (RQA) to study the change in the dynamical behavior of the PLC effect with the imposed strain rate. Our study revealed that the RQA is able to detect the unique crossover phenomenon in the PLC dynamics.
We present a continuous time random walk model for the Portevin-Le Chatelier (PLC) effect. From our result it is shown that the dynamics of the PLC band can be explained in terms of the Levy Walk.
The scaling behavior of the Portevin-Le Chatelier (PLC) effect was studied by deforming Al-2.5%Mg alloy for a wide range of strain rates. To reveal the exact scaling nature, the time series data of true stress vs. time, obtained during deformation, were analyzed by two complementary methods: the finite variance scaling method and the diffusion entropy analysis. From these analyses we could establish that in the entire span of strain rates, PLC effect showed Levy walk property.
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