Probing elementary dislocation mechanisms of local plastic deformation by the advanced acoustic emission technique

Vinogradov, Alexei; Danyuk, A. V.; Мерсон, Д. Л.; Yasnikov, I. S.

doi:10.1016/j.scriptamat.2018.03.036

Cited by 23 publications

(18 citation statements)

References 28 publications

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“…The individual slip lines, such as those reflecting the dislocation-mediated AE response in pure well annealed Fe with mean grain size of 150 μm, Fig. 2, emerge on a free surface as a result of the collective dislocation behaviour which can be resolved by the modern AE technique revealing separated transients masked in the continuous noise-like signal 17 . Even though every elementary slip event involves the correlated motion of a large number of atoms on a microscale, during strain hardening, numerous slip lines appear sporadically and independently in different grains of polycrystalline aggregates 18 .…”

Section: Results and Data Analysismentioning

confidence: 99%

“…AE stemming from dislocation mechanisms such as breaking away from unevenly distributed pinning points, motion between randomly spaced obstacles, escaping to a free surface at random locations along the gauge length, etc. involves a relatively large number of cooperatively moving dislocation segments and appears as an autoregressive stochastic process represented by a train of low-amplitude transients 17,18 . The question remains if the same applies to mechanical twins arising as a result of the strongly correlated motion of twinning dislocations, and generating powerful AE bursts with the amplitude proportional to the length and velocity of the nucleating twin 19,20 .…”

Section: Motivation and Methodologymentioning

confidence: 99%

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Mechanical Twinning is a Correlated Dynamic Process

Vinogradov

Agletdinov

Мерсон

2019

Sci Rep

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Plastic deformation and fracture of materials is accompanied by generation of elastic wave transients known as acoustic emissions (AE). A novel complex methodology combining the statistical analysis of distributions of time intervals between the successive AE events, and the unsupervised cluster analysis of the time series is proposed to test for possible correlations between emitting sources and to highlight their intrinsic dynamics. Aiming at revealing the essential temporal features of the twinning and dislocation dynamics, the proposed methodology was applied to the AE signals produced during plastic deformation in a magnesium alloy where both primary deformation modes - dislocation slip and twinning - operate concurrently. It has been undoubtedly demonstrated that the mechanical twinning belongs to a class of non-Poisson processes having a memory of the past in the millisecond range. As opposes to the correlated behaviour of twins, it was shown that the dislocation slip falls into the category of Poisson processes caused by independent sources.

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Section: Results and Data Analysismentioning

confidence: 99%

Section: Motivation and Methodologymentioning

confidence: 99%

Mechanical Twinning is a Correlated Dynamic Process

Vinogradov

Agletdinov

Мерсон

2019

Sci Rep

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“…Although acoustic emission measurements are used in the literature to investigate the thermal-or strain-induced martensitic transformations in different steels, [9][10][11] in most cases the root mean square (RMS) values of AE jerks or the AE energy emitted during the transformation were analyzed and correlated with the martensite volume fraction. In recent publications on AE, [8,12,13] the analysis goes beyond extracting only the above average information. It contains both the statistical analysis of AE jerks (by plotting the probability distributions of the elementary AE peaks [12] ) and the analysis of the shapes of the individual AE events (which can lead to identification of different clusters of signals of the same origin [8,13] ).…”

Section: Twinning-induced Plasticity (Twip) Andmentioning

confidence: 99%

“…In recent publications on AE, [8,12,13] the analysis goes beyond extracting only the above average information. It contains both the statistical analysis of AE jerks (by plotting the probability distributions of the elementary AE peaks [12] ) and the analysis of the shapes of the individual AE events (which can lead to identification of different clusters of signals of the same origin [8,13] ). Thus, such measurements can provide further information on the details of the dynamics of the martensitic transformations.…”

Section: Twinning-induced Plasticity (Twip) Andmentioning

confidence: 99%

Acoustic Emission During Austenite → ε Martensitic Phase Transformation in TWIP/TRIP Steels

Bolgár

Nagy

Daróczi

et al. 2019

Metall Mater Trans A

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Acoustic emission in two different TWIP/TRIP steels during thermally induced c-e martensitic phase transformation was investigated. Large asymmetry was observed: the noise activity was considerably larger for heating than cooling. This was explained by the plastic deformation and strain-induced martensite nucleation (which usually provides much lower acoustic emission signals) in the austenite during cooling. The amplitude and energy probability distribution functions for heating followed the power-law behavior, and the critical exponents were counted as well. The amplitude and energy exponents (a and e, respectively) for the two different samples were the same within the errors (a = 2.4 ± 0.2, e = 1.7 ± 0.1), indicating the universal character. The acoustic activity vs martensite volume faction showed a maximum at around 60 pct for heating, which is most probably related to the coming apart of the elastic fields of the martensite variants.

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“…Вместе с тем, современные программно-аппаратные комплексы позволяют существенно улучшить чувствительность метода за счет использования алгоритмов обработки непрерывного сигнала АЭ [15], благодаря чему был получен ряд новых, чрезвычайно важных результатов. Так, в работе [16] было установлено, что при царапании поликристаллического крупнозернистого материала наблюдается локальная нестационарность непрерывного сигнала акустической эмиссии при пересечении индентором границ зерен, при этом спектр плотности мощности сигналов АЭ оказался строго индивидуальным для каждой ориентации зерна. Указанные оптимистичные результаты стимулировали авторов настоящей работы на более детальное исследование зависимости сигналов АЭ от направления царапания по отношению к ориентации кристаллической решетки.…”

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Anisotropy of the acoustic emission signal on scratch testing of a single crystal of aluminum

Myhre¹,

Afanasiev²,

Merson³

et al. 2019

LOM

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In modern materials science, one of the main directions of solving the problem of improving the performance of parts and mechanisms is a radical improvement in the properties of material surface through its modification or application of coatings. To control the mechanical properties of structurally modified layers and coatings, local test methods are becoming increasingly common. Indentation and scratch testing are the most popular among such local techniques. To increase the significance of these tests, it is plausible to combine them with the registration of the acoustic emission (AE) signal. The purpose of this work is to assess the sensitivity of the AE parameters to the change in the dislocation slip systems using an aluminum single crystal as a test piece. The sample surface has been polished and analyzed by scanning electron microscopy and EBSD. The localized deformation test has been carried out on an instrumented tribometer by moving a conical indenter around the circle with a radius of 100 μm under a constant load of 2 N. The advantage of such a test is its ability to plastically deform the surface continuously in all crystallographic directions, preserve the stationary conditions for external factors and ensure the optimal signal-to-noise ratio for recording the AE signal. It is established that, depending on the direction of scratching, the hardness and the AE power exhibit opposite trends, both following the anisotropic properties of a cubic crystal lattice, while changing the configuration of active slip systems can be monitored using an interferometer according to characteristic traces of the slip lines on the polished surface of the sample near еру trace indenter. It is shown that the direction of scratching affects not only the energy of the AE signal, but also its spectral characteristics, in particular, the median frequency, and the extremes in the AE power diagram do not coincide with the extremes in the median frequency diagram.

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Probing elementary dislocation mechanisms of local plastic deformation by the advanced acoustic emission technique

Cited by 23 publications

References 28 publications

Mechanical Twinning is a Correlated Dynamic Process

Mechanical Twinning is a Correlated Dynamic Process

Acoustic Emission During Austenite → ε Martensitic Phase Transformation in TWIP/TRIP Steels

Anisotropy of the acoustic emission signal on scratch testing of a single crystal of aluminum

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