Modifications and Statistical Analysis of Acoustic Emission Models Based on the Damage and Fractal Characteristics

The damage process is accompanied by the acoustic emission for quasibrittle materials. And in the process of material damage evolution, the length of microcracks satisfies the fractal distribution. Research on their relationship in theory is helpful to reveal the law of material damage evolution and acoustic emission activities. Damage variable expressions are proposed based on the damage and fractal characteristics firstly. Then, the statistical models for acoustic emission considering damage and fractal characteristics are established by deducing the relationship between acoustic emission parameters and load cycles and fractal dimensions. The effects of damage and fractal effects on acoustic emission parameters are analyzed finally. The results show that the damage accelerates the AE activity to the rougher material, the opposite to the more homogeneous material. It can also be seen that the increase of the fractal dimension, the homogeneity constant m, will substantially increase the AE activities.

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Damage and fractal evolution trends of sandstones under constant-amplitude and tiered cyclic loading and unloading based on acoustic emission

International Journal of Distributed Sensor Networks ◽

10.1177/1550147719861020 ◽

2019 ◽

Vol 15 (7) ◽

pp. 155014771986102

Author(s):

Dongxu Liang ◽

Nong Zhang ◽

Lixiang Xie ◽

Guangming Zhao ◽

Deyu Qian

Keyword(s):

Acoustic Emission ◽

Cyclic Loading ◽

Damage Evolution ◽

Damage Accumulation ◽

Fractal Dimensions ◽

Damage Variable ◽

Constant Amplitude ◽

Kaiser Effect ◽

Cyclic Loading And Unloading ◽

Loading And Unloading

It is of significance to study the damage and destruction of rock under cyclic loading in geotechnical engineering. We determined the trends in damage evolution of sandstone under constant-amplitude and tiered cyclic loading and unloading under uniaxial compression. The results of the study show that (1) the variation of acoustic-emission events was consistent with the stress curves and 89% of all acoustic-emission events occurred during the cycling stages. The observed Kaiser effect was more notable in tiered cycling. (2) The damage variable increased sharply in the cycling stages and its increment was 0.07 higher for tiered cycling than constant-amplitude cycling. Sandstone exhibited greater damage under tiered cyclic loading and unloading. (3) Equations for the evolution of the damage variable under the two cycle modes were obtained by fitting of experimental data. (4) The fractal dimensions of the constant-amplitude cycle were larger than those of the tiered cycle. The process of damage and destruction presents a trend of reducing fractal dimension. The damage accumulation of sandstone under tiered cycling was faster than under constant-amplitude cycling. These results provide references for damage and early warning of rock under both constant-amplitude and tiered cyclic loading and unloading.

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Determination of the Box-Counting Fractal Dimension of Pore Distribution in Eggshell Based on Scanning Electron Microscopy Image Analysis

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.341-342.776 ◽

2011 ◽

Vol 341-342 ◽

pp. 776-779 ◽

Cited By ~ 1

Author(s):

Kai Zhang ◽

Shu Cai Wang

Keyword(s):

Fractal Dimensions ◽

Negative Slope ◽

Box Counting ◽

Microscopy Image ◽

Fractal Characteristics ◽

Object Of Study ◽

The Relationship ◽

Microscopy Image Analysis ◽

Electronic Microscope

The fractal characteristics of pore structures were investigated using duck eggshells as an object of study. The images of the sharp end, the equator and the blunt end of the eggshells were acquired by using scanning electronic microscope. The image processing operations were conducted for the preprocessing and the image converted into binary image. Then we developed programs based on the principle of changing megascopic degree and applied them to plot thelgN(δ)~lg(δ).The relationship betweenlgN(δ)andlg(δ)maintained linearity over a range [2,64] pixels. Therefore, the fractal dimensions of pore distributions were obtained from the negative slope by regression analysis. The experimental results showed that the fractal feature of the pore in eggshells was remarkable. The analysis confirmed that the blunt end of the eggshell in the pore distributions was more obvious than the sharp end and the equator.

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Fractal Characteristics of the Middle-Upper Ordovician Marine Shale Nano-Scale Porous Structure from the Ordos Basin, Northeast China

Journal of Nanoscience and Nanotechnology ◽

10.1166/jnn.2021.18885 ◽

2021 ◽

Vol 21 (1) ◽

pp. 274-283

Author(s):

Liang Liu ◽

Wuling Mo ◽

Min Wang ◽

Nengwu Zhou ◽

Yu Yan ◽

...

Keyword(s):

Fractal Dimension ◽

Pore Structure ◽

Pore Size ◽

Ordos Basin ◽

Fractal Dimensions ◽

Upper Ordovician ◽

Average Pore ◽

Marine Shale ◽

Fractal Characteristics ◽

The Relationship

The fractal characteristics of marine shale from the Middle-Upper Ordovician Wulalike Formation (O2w) in the southwest margin of the Ordos Basin are studied. Based on low-temperature nitrogen adsorption experiments, the FHH (Frenkel-Halsey-Hill) model was employed to investigate the relationship between the marine shale composition, such as TOC, mineral content and shale gas content, and pore structure parameters, such as BET specific surface area, average pore diameter, porosity and fractal dimension. The results show that the pore size distribution curve of shale slowly decreased after the pore size was greater than 50 nm, the pore size distribution showed multiple peaks, and the peak value was mainly in the range of 2–10 nm. Most pores are nanopores, although the pore type and shape are different. Two different fractal dimensions D1 and D2 are obtained from the two segments with relative pressures of 0–0.5 and 0.5–1.0, respectively: the D1 range is 2.77–2.82, and the D2 range is 2.63–2.66. As D1 is larger than D2, the pore structure of small pores is more uniform than that of large pores in the shale samples. The relationship between the fractal dimensions D1 and D2 and the total organic carbon (TOC) content is a convex curve. Fractal dimension D reaches its maximum when TOC is 0.53 wt.%. Fractal dimension D decreases with increasing specific surface area, porosity and average pore size. The fractal dimension has a different influence on the gas storage and migration in shale; the larger the fractal dimension is, the stronger the heterogeneity and the more complex the pore structure, and this outcome is conducive to the storage of gas in shale but not beneficial to the permeability and production of gas.

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Study on the Fractal Characteristics of Fracture Network Evolution Induced by Mining

Advances in Civil Engineering ◽

10.1155/2018/9589364 ◽

2018 ◽

Vol 2018 ◽

pp. 1-13 ◽

Cited By ~ 1

Author(s):

Tao Liang ◽

Xiaoli Liu ◽

Sijing Wang ◽

Enzhi Wang ◽

Quansheng Li

Keyword(s):

Fractal Dimension ◽

Fractal Dimensions ◽

Material Model ◽

Fracture Network ◽

Network Evolution ◽

Rock Properties ◽

Fracture Formation ◽

Fractal Characteristics ◽

Induced Fractures ◽

The Relationship

The evolution and distribution of fracture network induced by mining is essential to determine the mechanical properties and permeability of disturbed rock mass. In this paper, the similar material model tests are employed to simulate the stress variation, cyclic breaking, and fracture formation and distribution status of the overlying strata with different loading conditions, rock properties, and mining process. The fractal dimension of mining-induced fracture network varied with mining advancing, and the evolvement laws of fracture network with mining advancing and different mining advancing footage are concerned and obtained. By establishing the relationship between the fractal dimension and the mining length in different horizontal and vertical zones, it demonstrates that the fractal dimensions in horizontal and vertical zones have a self-similar characteristic, and the distribution of the fractal dimension of the mining-induced fractures shows generally the “W”-type trend.

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The influence of ultrasound signal parameters on sonoluminescence light intensity

Archives of Electrical Engineering ◽

10.2478/aee-2013-0048 ◽

2013 ◽

Vol 62 (4) ◽

pp. 605-612

Author(s):

Marek Szmechta ◽

Tomasz Boczar ◽

Dariusz Zmarzły

Keyword(s):

Acoustic Emission ◽

Acoustic Waves ◽

Power Transformer ◽

Electrical Power ◽

Partial Discharges ◽

Research Project ◽

Insulation Systems ◽

Secondary Phenomenon ◽

New Research ◽

The Relationship

Abstract Topics of this article concern the study of the fundamental nature of the sonoluminescence phenomenon occurring in liquids. At the Institute of Electrical Power Engineering at Opole University of Technology the interest in that phenomenon known as secondary phenomenon of cavitation caused by ultrasound became the genesis of a research project concerning acoustic cavitation in mineral insulation oils in which a number of additional experiments performed in the laboratory aimed to determine the influence of a number of acoustic parameters on the process of the studied phenomenona. The main purpose of scientific research subject undertaken was to determine the relationship between the generation of partial discharges in high-voltage power transformer insulation systems, the issue of gas bubbles in transformer oils and the generated acoustic emission signals. It should be noted that currently in the standard approach, the phenomenon of generation of acoustic waves accompanying the occurrence of partial discharges is generally treated as a secondary phenomenon, but it can also be a source of many other related phenomena. Based on our review of the literature data on those referred subjects taken, it must be noted, that this problem has not been clearly resolved, and the description of the relationship between these phenomena is still an open question. This study doesn’t prove all in line with the objective of the study, but can be an inspiration for new research project in the future in this topic. Solution of this problem could be a step forward in the diagnostics of insulation systems for electrical power devices based on non-invasive acoustic emission method.

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Study on mechanical properties and damage evolution of carbonaceous shale under triaxial compression with acoustic emission

International Journal of Damage Mechanics ◽

10.1177/1056789521991193 ◽

2021 ◽

pp. 105678952199119

Author(s):

Kai Yang ◽

Qixiang Yan ◽

Chuan Zhang ◽

Wang Wu ◽

Fei Wan

Keyword(s):

Mechanical Properties ◽

Acoustic Emission ◽

Water Content ◽

Damage Evolution ◽

Damage Assessment ◽

Triaxial Compression ◽

Confining Pressure ◽

Damage Variable ◽

Natural State ◽

Carbonaceous Shale

To explore the mechanical properties and damage evolution characteristics of carbonaceous shale with different confining pressures and water-bearing conditions, triaxial compression tests accompanied by simultaneous acoustic emission (AE) monitoring were conducted on carbonaceous shale rock specimens. The AE characteristics of carbonaceous shale were investigated, a damage assessment method based on Shannon entropy of AE was further proposed. The results suggest that the mechanical properties of carbonaceous shale intensify with increasing confining pressure and degrade with increasing water content. Moisture in rocks does not only weaken the cohesion but also reduce the internal friction angle of carbonaceous shale. It is observed that AE activities mainly occur in the post-peak stage and the strong AE activities of saturated carbonaceous shale specimens appear at a lower normalized stress level than that of natural-state specimens. The maximum AE counts and AE energy increase with water content while decrease with confining pressure. Both confining pressure and water content induce changes in the proportions of AE dominant frequency bands, but the changes caused by confining pressure are more significant than those caused by water content. The results also indicate that AE entropy can serve as an applicable index for rock damage assessment. The damage evolution process of carbonaceous shale can be divided into two main stages, including the stable damage development stage and the damage acceleration stage. The damage variable increases slowly accompanied by a few AE activities at the first stage, which is followed by a rapid growth along with intense acoustic emission activities at the damage acceleration stage. Moreover, there is a sharp rise in the damage evolution curve for the natural-state specimen at the damage acceleration stage, while the damage variable develops slowly for the saturated-state specimen.

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