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Kamel SM, Daróczi L, Tóth LZ, Beke DL, Juárez GG, Cobo S, Salmon L, Molnár G, Bousseksou A. Acoustic emissions from spin crossover complexes. JOURNAL OF MATERIALS CHEMISTRY. C 2024; 12:5757-5765. [PMID: 38680543 PMCID: PMC11044199 DOI: 10.1039/d4tc00495g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/05/2024] [Accepted: 03/19/2024] [Indexed: 05/01/2024]
Abstract
Acoustic emission from the compounds [Fe(HB(tz)3)2] and [Fe(Htrz)(trz)2]BF4 was detected during the thermally induced spin transition and is correlated with simultaneously recorded calorimetric signals. We ascribe this phenomenon to elastic waves produced by microstructural and volume changes accompanying the spin transition. Despite the perfect reversibility of the spin state switching (seen by the calorimeter), the acoustic emission activity decreases for successive thermal cycles, revealing thus irreversible microstructural evolution of the samples. The acoustic emission signal amplitude and energy probability distribution functions followed power-law behavior and the characteristic exponents were found to be similar for the two samples both on heating and cooling, indicating the universal character, which is further substantiated by the well scaled average temporal shapes of the avalanches.
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Affiliation(s)
- Sarah M Kamel
- Department of Solid State Physics, Doctoral School of Physics, University of Debrecen P.O. Box 2 H-4010 Debrecen Hungary
- Physics Department, Faculty of Science Ain Shams University, Abbassia 11566 Cairo Egypt
| | - Lajos Daróczi
- Department of Solid State Physics, Doctoral School of Physics, University of Debrecen P.O. Box 2 H-4010 Debrecen Hungary
| | - László Z Tóth
- Department of Solid State Physics, Doctoral School of Physics, University of Debrecen P.O. Box 2 H-4010 Debrecen Hungary
| | - Dezső L Beke
- Department of Solid State Physics, Doctoral School of Physics, University of Debrecen P.O. Box 2 H-4010 Debrecen Hungary
| | - Gerardo Gutiérrez Juárez
- Departamento de Ingeniería Física, División de Ciencias e Ingenierías, Universidad de Guanajuato-Campus León, Loma del Bosque 103, Loma del Campestre 37150 León Gto. Mexico
| | - Saioa Cobo
- LCC, CNRS & University of Toulouse, 205 route de Narbonne 31077 Toulouse France
| | - Lionel Salmon
- LCC, CNRS & University of Toulouse, 205 route de Narbonne 31077 Toulouse France
| | - Gábor Molnár
- LCC, CNRS & University of Toulouse, 205 route de Narbonne 31077 Toulouse France
| | - Azzedine Bousseksou
- LCC, CNRS & University of Toulouse, 205 route de Narbonne 31077 Toulouse France
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2
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Tóth LZ, Bronstein E, Daróczi L, Shilo D, Beke DL. Scaling of Average Avalanche Shapes for Acoustic Emission during Jerky Motion of Single Twin Boundary in Single-Crystalline Ni 2MnGa. MATERIALS (BASEL, SWITZERLAND) 2023; 16:2089. [PMID: 36903204 PMCID: PMC10004433 DOI: 10.3390/ma16052089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Revised: 02/28/2023] [Accepted: 03/01/2023] [Indexed: 06/18/2023]
Abstract
Temporal average shapes of crackling noise avalanches, U(t) (U is the detected parameter proportional to the interface velocity), have self-similar behavior, and it is expected that by appropriate normalization, they can be scaled together according to a universal scaling function. There are also universal scaling relations between the avalanche parameters (amplitude, A, energy, E, size (area), S, and duration, T), which in the mean field theory (MFT) have the form E∝A3, S∝A2, S∝T2. Recently, it turned out that normalizing the theoretically predicted average U(t) function at a fixed size, U(t)=atexp-bt2 (a and b are non-universal, material-dependent constants) by A and the rising time, R, a universal function can be obtained for acoustic emission (AE) avalanches emitted during interface motions in martensitic transformations, using the relation R~A1-φ too, where φ is a mechanism-dependent constant. It was shown that φ also appears in the scaling relations E~A3-φ and S~A2-φ, in accordance with the enigma for AE, that the above exponents are close to 2 and 1, respectively (in the MFT limit, i.e., with φ= 0, they are 3 and 2, respectively). In this paper, we analyze these properties for acoustic emission measurements carried out during the jerky motion of a single twin boundary in a Ni50Mn28.5Ga21.5 single crystal during slow compression. We show that calculating from the above-mentioned relations and normalizing the time axis of the average avalanche shapes with A1-φ, and the voltage axis with A, the averaged avalanche shapes for the fixed area are well scaled together for different size ranges. These have similar universal shapes as those obtained for the intermittent motion of austenite/martensite interfaces in two different shape memory alloys. The averaged shapes for a fixed duration, although they could be acceptably scaled together, showed a strong positive asymmetry (the avalanches decelerate much slower than they accelerate) and thus did not show a shape reminiscent of an inverted parabola, predicted by the MFT. For comparison, the above scaling exponents were also calculated from simultaneously measured magnetic emission data. It was obtained that the φ values are in accordance with theoretical predictions going beyond the MFT, but the AE results for φ are characteristically different from these, supporting that the well-known enigma for AE is related to this deviation.
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Affiliation(s)
- László Z. Tóth
- Department of Solid State Physics, University of Debrecen, P.O. Box 400, H-4002 Debrecen, Hungary
| | - Emil Bronstein
- Faculty of Mechanical Engineering, Technion—Israel Institute of Technology, Haifa 3200003, Israel
| | - Lajos Daróczi
- Department of Solid State Physics, University of Debrecen, P.O. Box 400, H-4002 Debrecen, Hungary
| | - Doron Shilo
- Faculty of Mechanical Engineering, Technion—Israel Institute of Technology, Haifa 3200003, Israel
| | - Dezső L. Beke
- Department of Solid State Physics, University of Debrecen, P.O. Box 400, H-4002 Debrecen, Hungary
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Tóth LZ, Daróczi L, Elrasasi TY, Beke DL. Clustering Characterization of Acoustic Emission Signals Belonging to Twinning and Dislocation Slip during Plastic Deformation of Polycrystalline Sn. MATERIALS (BASEL, SWITZERLAND) 2022; 15:6696. [PMID: 36234037 PMCID: PMC9572014 DOI: 10.3390/ma15196696] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Revised: 09/21/2022] [Accepted: 09/22/2022] [Indexed: 06/16/2023]
Abstract
Results of acoustic emission (AE) measurements, carried out during plastic deformation of polycrystalline Sn samples, are analyzed by the adaptive sequential k-means method. The acoustic avalanches, originating from different sources, are separated on the basis of their spectral properties, that is, sorted into clusters, presented both on the so-called feature space (energy-median frequency plot) and on the power spectral density (PSD) curves. We found that one cluster in every measurement belongs to background vibrations, while the remaining ones are clearly attributed to twinning as well as dislocation slips at −30 °C and 25 °C, respectively. Interestingly, fingerprints of the well-known “ringing” of AE signals are present in different weights on the PSD curves. The energy and size distributions of the avalanches, corresponding to twinning and dislocation slips, show a bit different power-law exponents from those obtained earlier by fitting all AE signals without cluster separation. The maximum-likelihood estimation of the avalanche energy (ε) and size (τ) exponents provide ε=1.57±0.05 (at −30 °C) and ε=1.35±0.1 (at 25 °C), as well as τ=1.92±0.05 (at −30 °C) and τ= 1.55±0.1 (at 25 °C). The clustering analysis provides not only a manner to eliminate the background noise, but the characteristic avalanche shapes are also different for the two mechanisms, as it is visible on the PSD curves. Thus, we have illustrated that this clustering analysis is very useful in discriminating between different AE sources and can provide more realistic estimates, for example, for the characteristic exponents as compared to the classical hit-based approach where the exponents reflect an average value, containing hits from the low-frequency mechanical vibrations of the test machine, too.
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Affiliation(s)
- László Z. Tóth
- Department of Solid State Physics, University of Debrecen, P.O. Box 400, H-4002 Debrecen, Hungary
| | - Lajos Daróczi
- Department of Solid State Physics, University of Debrecen, P.O. Box 400, H-4002 Debrecen, Hungary
| | - Tarek Y. Elrasasi
- Department of Physics, Faculty of Science, Benha University, Benha 13518, Egypt
| | - Dezső L. Beke
- Department of Solid State Physics, University of Debrecen, P.O. Box 400, H-4002 Debrecen, Hungary
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Denouement of the Energy-Amplitude and Size-Amplitude Enigma for Acoustic-Emission Investigations of Materials. MATERIALS 2022; 15:ma15134556. [PMID: 35806681 PMCID: PMC9267350 DOI: 10.3390/ma15134556] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Revised: 06/17/2022] [Accepted: 06/24/2022] [Indexed: 02/04/2023]
Abstract
There are many systems producing crackling noise (avalanches) in materials. Temporal shapes of avalanches, U(t) (U is the detected voltage signal, t is the time), have self-similar behaviour and the normalized U(t) function (e.g., dividing both the values of U and t by S1/2, where S is the avalanche area), averaged for fixed S, should be the same, independently of the type of materials or avalanche mechanisms. However, there are experimental evidences that the temporal shapes of avalanches do not scale completely in a universal way. The self-similarity also leads to universal power-law-scaling relations, e.g., between the energy, E, and the peak amplitude, Am, or between S and Am. There are well-known enigmas, where the above exponents in acoustic emission measurements are rather close to 2 and 1, respectively, instead of E~Am3 and S~Am2, obtained from the mean field theory, MFT. We show, using a theoretically predicted averaged function for the fixed avalanche area, U(t)=atexp(−bt2) (where a and b are non-universal, material-dependent constants), that the scaling exponents can be different from the MFT values. Normalizing U by Am and t by tm (the time belonging to the Am: rise time), we obtain tm~Am1−φ (the MFT values can be obtained only if φ would be zero). Here, φ is expected to be material-independent and to be the same for the same mechanism. Using experimental results on martensitic transformations in two different shape-memory single-crystals, φ = 0.8 ± 0.1 was obtained (φ is the same for both alloys). Thus, dividing U by Am as well as t by Am1−φ (~tm) leads to the same common, normalized temporal shape for different, fixed values of S. This normalization can also be used in general for other experimental results (not only for acoustic emission), which provide information about jerky noises in materials.
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Ispánovity PD, Ugi D, Péterffy G, Knapek M, Kalácska S, Tüzes D, Dankházi Z, Máthis K, Chmelík F, Groma I. Dislocation avalanches are like earthquakes on the micron scale. Nat Commun 2022; 13:1975. [PMID: 35418187 PMCID: PMC9007997 DOI: 10.1038/s41467-022-29044-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Accepted: 02/16/2022] [Indexed: 11/29/2022] Open
Abstract
Compression experiments on micron-scale specimens and acoustic emission (AE) measurements on bulk samples revealed that the dislocation motion resembles a stick-slip process - a series of unpredictable local strain bursts with a scale-free size distribution. Here we present a unique experimental set-up, which detects weak AE waves of dislocation slip during the compression of Zn micropillars. Profound correlation is observed between the energies of deformation events and the emitted AE signals that, as we conclude, are induced by the collective dissipative motion of dislocations. The AE data also reveal a two-level structure of plastic events, which otherwise appear as a single stress drop. Hence, our experiments and simulations unravel the missing relationship between the properties of acoustic signals and the corresponding local deformation events. We further show by statistical analyses that despite fundamental differences in deformation mechanism and involved length- and time-scales, dislocation avalanches and earthquakes are essentially alike.
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Grants
- TKP2020-IKA-05 Emberi Eroforrások Minisztériuma (Ministry of Human Capacities)
- NKFIH-K-119561 Nemzeti Kutatási, Fejlesztési és Innovációs Hivatal (NKFI Office)
- NKFIH-FK-138975 Nemzeti Kutatási, Fejlesztési és Innovációs Hivatal (NKFI Office)
- NKFIH-K-119561 Nemzeti Kutatási, Fejlesztési és Innovációs Hivatal (NKFI Office)
- NKFIH-FK-138975 Nemzeti Kutatási, Fejlesztési és Innovációs Hivatal (NKFI Office)
- NKFIH-K-119561 Nemzeti Kutatási, Fejlesztési és Innovációs Hivatal (NKFI Office)
- NKFIH-K-119561 Nemzeti Kutatási, Fejlesztési és Innovációs Hivatal (NKFI Office)
- NKFIH-FK-138975 Nemzeti Kutatási, Fejlesztési és Innovációs Hivatal (NKFI Office)
- NKFIH-K-119561 Nemzeti Kutatási, Fejlesztési és Innovációs Hivatal (NKFI Office)
- 19-22604S Grantová Agentura České Republiky (Grant Agency of the Czech Republic)
- Innovációs és Technológiai Minisztérium: ÚNKP-20-3, ÚNKP-21-4, ÚNKP-21-3
- Innovációs és Technológiai Minisztérium: ÚNKP-21-3
- Czech Science Foundation (grant No.19-22604S)
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Affiliation(s)
- Péter Dusán Ispánovity
- Eötvös Loránd University, Department of Materials Physics, Pázmány Péter sétany 1/a., 1117 Budapest, Hungary.
| | - Dávid Ugi
- Eötvös Loránd University, Department of Materials Physics, Pázmány Péter sétany 1/a., 1117 Budapest, Hungary.
| | - Gábor Péterffy
- Eötvös Loránd University, Department of Materials Physics, Pázmány Péter sétany 1/a., 1117 Budapest, Hungary
| | - Michal Knapek
- Charles University, Faculty of Mathematics and Physics, Department of Physics of Materials, Ke Karlovu 5, 121 16 Prague 2, Czech Republic
| | - Szilvia Kalácska
- Eötvös Loránd University, Department of Materials Physics, Pázmány Péter sétany 1/a., 1117 Budapest, Hungary
- Mines Saint-Etienne, Univ Lyon, CNRS, UMR 5307 LGF, Centre SMS, 158 cours Fauriel 42023, Saint-Étienne, France
| | - Dániel Tüzes
- Eötvös Loránd University, Department of Materials Physics, Pázmány Péter sétany 1/a., 1117 Budapest, Hungary
| | - Zoltán Dankházi
- Eötvös Loránd University, Department of Materials Physics, Pázmány Péter sétany 1/a., 1117 Budapest, Hungary
| | - Kristián Máthis
- Charles University, Faculty of Mathematics and Physics, Department of Physics of Materials, Ke Karlovu 5, 121 16 Prague 2, Czech Republic
| | - František Chmelík
- Charles University, Faculty of Mathematics and Physics, Department of Physics of Materials, Ke Karlovu 5, 121 16 Prague 2, Czech Republic
| | - István Groma
- Eötvös Loránd University, Department of Materials Physics, Pázmány Péter sétany 1/a., 1117 Budapest, Hungary
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Change of Acoustic Emission Characteristics during Temperature Induced Transition from Twinning to Dislocation Slip under Compression in Polycrystalline Sn. MATERIALS 2021; 15:ma15010224. [PMID: 35009370 PMCID: PMC8745864 DOI: 10.3390/ma15010224] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Revised: 12/21/2021] [Accepted: 12/23/2021] [Indexed: 11/16/2022]
Abstract
In this study, acoustic emission (AE) measurements on polycrystalline tin as a function of temperature at different driving rates under compression were carried out. It is shown that there is a definite difference between the acoustic emission characteristics belonging to twinning (low temperatures) as well as to dislocation slip (high temperatures). The stress averaged values of the exponents of the energy probability density functions decreased from ε = 1.45 ± 0.05 (-60 °C) to ε = 1.20 ± 0.15 (50 °C) at a driving rate of ε=0.15 s-1, and the total acoustic energy decreased by three orders of magnitude with increasing temperature. In addition, the exponent γ in the scaling relation SAE~DAEγ (SAE is the area and DAE is the duration) also shows similar temperature dependence (changing from γ = 1.78 ± 0.08 to γ = 1.35 ± 0.05), illustrating that the avalanche statistics belong to two different microscopic deformation mechanisms. The power law scaling relations were also analyzed, taking into account that the detected signal is always the convolution of the source signal and the transfer function of the system. It was obtained that approximate values of the power exponents can be obtained from the parts of the above functions, belonging to large values of parameters. At short duration times, the attenuation effect of the AE detection system dominates the time dependence, from which the characteristic attenuation time, τa, was determined as τa ≅ 70 μs.
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Vincent-Dospital T, Cochard A, Santucci S, Måløy KJ, Toussaint R. Thermally activated intermittent dynamics of creeping crack fronts along disordered interfaces. Sci Rep 2021; 11:20418. [PMID: 34650113 PMCID: PMC8516960 DOI: 10.1038/s41598-021-98556-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Accepted: 09/03/2021] [Indexed: 12/02/2022] Open
Abstract
We present a subcritical fracture growth model, coupled with the elastic redistribution of the acting mechanical stress along rugous rupture fronts. We show the ability of this model to quantitatively reproduce the intermittent dynamics of cracks propagating along weak disordered interfaces. To this end, we assume that the fracture energy of such interfaces (in the sense of a critical energy release rate) follows a spatially correlated normal distribution. We compare various statistical features from the obtained fracture dynamics to that from cracks propagating in sintered polymethylmethacrylate (PMMA) interfaces. In previous works, it has been demonstrated that such an approach could reproduce the mean advance of fractures and their local front velocity distribution. Here, we go further by showing that the proposed model also quantitatively accounts for the complex self-affine scaling morphology of crack fronts and their temporal evolution, for the spatial and temporal correlations of the local velocity fields and for the avalanches size distribution of the intermittent growth dynamics. We thus provide new evidence that an Arrhenius-like subcritical growth is particularly suitable for the description of creeping cracks.
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Affiliation(s)
- Tom Vincent-Dospital
- ITES UMR 7063, Université de Strasbourg, 67084, Strasbourg, France.
- SFF Porelab, The Njord Centre, Department of physics, University of Oslo, Oslo, Norway.
| | - Alain Cochard
- ITES UMR 7063, Université de Strasbourg, 67084, Strasbourg, France.
| | - Stéphane Santucci
- ENS de Lyon, Université Claude Bernard, CNRS, Laboratoire de Physique, Université de Lyon, Lyon, France
- Lavrentyev Institute of Hydrodynamics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
| | - Knut Jørgen Måløy
- SFF Porelab, The Njord Centre, Department of physics, University of Oslo, Oslo, Norway
| | - Renaud Toussaint
- ITES UMR 7063, Université de Strasbourg, 67084, Strasbourg, France.
- SFF Porelab, The Njord Centre, Department of physics, University of Oslo, Oslo, Norway.
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Baró J, Pouragha M, Wan R, Davidsen J. Quasistatic kinetic avalanches and self-organized criticality in deviatorically loaded granular media. Phys Rev E 2021; 104:024901. [PMID: 34525539 DOI: 10.1103/physreve.104.024901] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Accepted: 07/08/2021] [Indexed: 11/07/2022]
Abstract
The behavior of granular media under quasistatic loading has recently been shown to attain a stable evolution state corresponding to a manifold in the space of micromechanical variables. This state is characterized by sudden transitions between metastable jammed states, involving the partial micromechanical rearrangement of the granular medium. Using numerical simulations of two-dimensional granular media under quasistatic biaxial compression, we show that the dynamics in the stable evolution state is characterized by scale-free avalanches well before the macromechanical stationary flow regime traditionally linked to a self-organized critical state. This, together with the nonuniqueness and the nonmonotony of macroscopic deformation curves, suggests that the statistical avalanche properties and the susceptibilities of the system cannot be reduced to a function of the macromechanical state. The associated scaling exponents are nonuniversal and depend on the interactions between particles. For stiffer particles (or samples at low confining pressure) we find distributions of avalanche properties compatible with the predictions of mean-field theory. The scaling exponents decrease below the mean-field values for softer interactions between particles. These lower exponents are consistent with observations for amorphous solids at their critical point. We specifically discuss the relationship between microscopic and macroscopic variables, including the relation between the external stress drop and the internal potential energy released during kinetic avalanches.
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Affiliation(s)
- Jordi Baró
- Department of Physics and Astronomy, University of Calgary, 2500 University Drive NW Calgary, Alberta, Canada T2N 1N4.,Centre for Mathematical Research, Campus de Bellaterra, Edifici C, 08193 Bellaterra, Barcelona, Spain
| | - Mehdi Pouragha
- Civil Engineering Department, University of Calgary, 2500 University Drive NW Calgary, Alberta, Canada T2N 1N4.,Department of Civil and Environmental Engineering, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario, Canada K1S 5B6
| | - Richard Wan
- Civil Engineering Department, University of Calgary, 2500 University Drive NW Calgary, Alberta, Canada T2N 1N4
| | - Jörn Davidsen
- Department of Physics and Astronomy, University of Calgary, 2500 University Drive NW Calgary, Alberta, Canada T2N 1N4.,Hotchkiss Brain Institute, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, Canada T2N 4N1
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9
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Casals B, Dahmen KA, Gou B, Rooke S, Salje EKH. The duration-energy-size enigma for acoustic emission. Sci Rep 2021; 11:5590. [PMID: 33692380 PMCID: PMC7947008 DOI: 10.1038/s41598-021-84688-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Accepted: 02/17/2021] [Indexed: 12/02/2022] Open
Abstract
Acoustic emission (AE) measurements of avalanches in different systems, such as domain movements in ferroics or the collapse of voids in porous materials, cannot be compared with model predictions without a detailed analysis of the AE process. In particular, most AE experiments scale the avalanche energy E, maximum amplitude Amax and duration D as E ~ Amaxx and Amax ~ Dχ with x = 2 and a poorly defined power law distribution for the duration. In contrast, simple mean field theory (MFT) predicts that x = 3 and χ = 2. The disagreement is due to details of the AE measurements: the initial acoustic strain signal of an avalanche is modified by the propagation of the acoustic wave, which is then measured by the detector. We demonstrate, by simple model simulations, that typical avalanches follow the observed AE results with x = 2 and ‘half-moon’ shapes for the cross-correlation. Furthermore, the size S of an avalanche does not always scale as the square of the maximum AE avalanche amplitude Amax as predicted by MFT but scales linearly S ~ Amax. We propose that the AE rise time reflects the atomistic avalanche time profile better than the duration of the AE signal.
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Affiliation(s)
- Blai Casals
- Department of Earth Sciences, Cambridge University, Cambridge, UK.
| | - Karin A Dahmen
- Department of Physics, University of Illinois, Urbana, IL, 61801, USA
| | - Boyuan Gou
- State Key Laboratory for Mechanical Behavior of Materials, Xi'An Jiao Tong University, Xian, 710049, Shaanxi, People's Republic of China
| | - Spencer Rooke
- Department of Physics, University of Illinois, Urbana, IL, 61801, USA
| | - Ekhard K H Salje
- Department of Earth Sciences, Cambridge University, Cambridge, UK
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