scholarly journals Effect of Thermal Treatment on Fractals in Acoustic Emission of Rock Material

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Z. Z. Zhang ◽  
X. L. Xu ◽  
Q. P. Sun ◽  
Y. Dong
Keyword(s):  
Acoustic Emission ◽  
Stress Level ◽  
Failure Process ◽  
Fractal Dimensions ◽  
Rock Material ◽  
External Loading ◽  
Heat Temperature ◽  
Failure Point ◽  
Ae Counts ◽  
Peak Value

Acoustic emission (AE) series on time and location distributions on space are all fractal during the failure process of rock material. In this paper, AE signals of heated rock samples at different temperature under uniaxial compression were captured, and the correlation fractal dimensions (CFDs) of AE counts series at different stress level were calculated using Grassberger-Procaccia algorithm. The temperature effect on AE fractal behavior was revealed. The results show that as the heat temperature increases, the total AE counts are more, while the peak value is less. With the increase of external loading, the AE CFD increases fast to a peak at first and then decreases to a bottom and, after that, increases again but within a narrow range. 200°C and 800°C are two thresholds. As the heat temperature rises, the maximum CFD value and the corresponding stress level both increase from 25°C to 200°C and decrease from 200°C to 800°C and then increase again from 800°C to 1200°C. The CFD value at the failure point shows polynomial decline with rising heat temperature.

scholarly journals Acoustic Emission Characteristics of Graded Loading Intact and Holey Rock Samples during the Damage and Failure Process

2019 ◽  
Vol 9 (8) ◽  
pp. 1595 ◽  
Author(s):  
Xiaofei Liu ◽  
Huajie Zhang ◽  
Xiaoran Wang ◽  
Chong Zhang ◽  
Hui Xie ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Rock Mass ◽  
Large Scale ◽  
Rock Sample ◽  
Axial Stress ◽  
Failure Process ◽  
Dynamic Monitoring ◽  
Rock Samples ◽  
General Law ◽  
Ae Counts

Rock burst is the result of the development and extension of micro-cracks during the loading process of large-scale rock mass in underground space engineering. Dynamic monitoring results by acoustic emission (AE) can accurately perceive the inner fracture evolution of rock mass and effectively warn about its induced disasters early. By contrastive testing the AE parameters in the whole fracture process of the intact and holey rock samples under graded loading, their spatiotemporal evolution rules were analyzed in this paper, and the damage model of rock samples based on AE localization events was established to analyze the relationship between rock damage and loads. The results show that: (1) Under the condition of grading loading, AE parameter increases with the increase of axial stress and show three states, respectively, which are slow-growth, stabilization and rapid increasing; meanwhile, the damage of the sample has a cumulative effect with time. (2) The AE counts and energy are highly correlated with the fracture of the sample that the more severe the damage of the sample, the faster the crack propagation as well as the higher the acoustic emission counts and the energy amplitude. The damage state of granite sample can be accurately judged by two parameters to character the damage evolution process and fracture mechanism. (3) Compared with the intact rock sample, due to the pressure relief effect of the hole, the rock sample containing the hole takes a long time in the compaction stage and with higher load stress level. Although the AE counts and energy were lower in the damage process, the general law of their response during damage and instability process still exists.

scholarly journals On the Kaiser Effect of Rock under Cyclic Loading and Unloading Conditions: Insights from Acoustic Emission Monitoring

Energies ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 3255 ◽  
Author(s):  
Qingbin Meng ◽  
Yanlong Chen ◽  
Mingwei Zhang ◽  
Lijun Han ◽  
Hai Pu ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Cyclic Loading ◽  
Stress Level ◽  
Loading Rate ◽  
Transition Period ◽  
Failure Process ◽  
Future Application ◽  
Emission Characteristic ◽  
Kaiser Effect ◽  
Stress Point

The Kaiser effect reflects the memory of the loaded rock to the irreversible damage and deformation. The stress level, loading rate and lithology are the main factors affecting the Kaiser effect of the rock. To identify the accurate stress point of the Kaiser effect, the MTS 816 rock mechanics testing system and the DS5-A acoustic emission testing and analysis system were adopted. The uniaxial cyclic loading–unloading and acoustic emission characteristic test of 90 rock specimens from three types of rocks under different stress level and loading rate was carried out. The evolution of acoustic emission under uniaxial compression of the rock corresponds to the compaction stage, elastic stage, yield stage and post-peak stress drop stage of the rock deformation and failure process and is divided into the quiet period, transition period, active period and decay period of the acoustic emission. The larger the hardness of rock is, the earlier the stress point of the Kaiser effect appears. The loading stress level (σA) has appreciable influence on the Kaiser effect of the rock. When σA ≥ 0.7σc, the Kaiser effect disappears. Usually, the dilatancy stress (crack initiation stress) does not exceed 70% of the uniaxial compressive strength (σc) of the rock, and the stress point can be the threshold to determine whether the Kaiser effect occurs. The influence of loading rate (lr) on Felicity rate (FR) is relatively large when lr < 0.01 mm/s, and FR rapidly grows with increase of the loading rate. When lr ≥ 0.01 mm/s, the influence of the loading rate on FR is relatively small. The findings facilitate the future application of the Kaiser effect and improvement of the accuracy of the acoustic emission data interpretation.

scholarly journals Bearing defect diagnosis and acoustic emission

2003 ◽  
Vol 217 (4) ◽  
pp. 257-272 ◽  
Author(s):  
A Morhain ◽  
D Mba
Keyword(s):  
Acoustic Emission ◽  
Threshold Level ◽  
Diagnostic Methods ◽  
Non Destructive Testing ◽  
Test Rig ◽  
Destructive Testing ◽  
High Background ◽  
Bearing Defect ◽  
Non Destructive ◽  
Ae Counts

Acoustic emission (AE) was originally developed for non-destructive testing of static structures, but over the years its application has been extended to health monitoring of rotating machines and bearings. It offers the advantage of earlier defect detection in comparison with vibration analysis. However, limitations in the successful application of the AE technique for monitoring bearings have been partly due to the difficulty in processing, interpreting and classifying the acquired data. The investigation reported in this paper was centred on the application of standard AE characteristic parameters on a radially loaded bearing. An experimental test rig was modified such that defects could be seeded onto the inner and outer races of a test bearing. As the test rig was adapted for this purpose, it offered high background acoustic emission noise providing a realistic test for fault diagnosis. In addition to a review of current diagnostic methods for applying AE to bearing diagnosis, the results of this investigation validated the use of r. m. s., amplitude, energy and AE counts for diagnosis. Furthermore, this study determined the most appropriate threshold level for AE count diagnosis, the first known attempt.

scholarly journals Research on Failure Characteristics of Concrete Three-Point Bending Beams with Preexisting Cracks in Different Positions Based on Numerical Simulation

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Liuqun Zhao ◽  
Li Zheng ◽  
Hui Qin ◽  
Tiesuo Geng ◽  
Yonggang Tan ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Bearing Capacity ◽  
Failure Modes ◽  
Failure Process ◽  
Engineering Application ◽  
Tensile Failure ◽  
Engineering Structures ◽  
Failure Characteristics ◽  
Three Point Bending ◽  
Wide Range

Concrete three-point bending beams with preexisting cracks are widely used to study the growth process of I-II mixed mode cracks. Studying the failure characteristics of preexisting cracks at different locations on concrete three-point bending beams not only has important scientific significance but also has a wide range of engineering application backgrounds in the safety assessment of engineering structures. In this paper, through several numerical experiments, the influence of preexisting cracks at different positions on the failure characteristics of concrete three-point bending beams is studied, and three typical failure modes are obtained. The failure process of the specimens with three typical failure modes is discussed in detail, and it is pointed out that the crack failure mode is tensile failure. The change trends of bearing capacity, acoustic emission quantity, and acoustic emission energy of three typical failure modes are analyzed. The maximum bearing capacity, the maximum acoustic emission quantity, and energy of three failure modes of concrete three-point bending beams generally show an increasing trend.

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

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.

scholarly journals Acoustic Emission Simulation on Coal Specimen Subjected to Cyclic Loading

2020 ◽  
Vol 2020 ◽  
pp. 1-17
Author(s):  
Huiqiang Duan ◽  
Depeng Ma
Keyword(s):  
Numerical Simulation ◽  
Acoustic Emission ◽  
Cyclic Loading ◽  
Confining Pressure ◽  
Rock Masses ◽  
Coal Specimen ◽  
Cycle Number ◽  
Confining Pressures ◽  
Unloading Rate ◽  
Ae Counts

The damage and failure state of the loaded coal and rock masses is indirectly reflected by its acoustic emission (AE) characteristics. Therefore, it is of great significance to study the AE evolution of loaded coal and rock masses for the evaluation of damage degree and prediction of collapse. The paper mainly represents a numerical simulation investigation of the AE characteristics of coal specimen subjected to cyclic loading under three confining pressures, loading-unloading rates, and valley stresses. From the numerical simulation tests, the following conclusions can be drawn: (1) The final cycle number of coal specimen subjected to cyclic loading is significantly influenced by the confining pressure, followed the valley stress. With the increase in confining pressure or valley stress, the cycle number tends to increase. However, the loading-unloading rate has a little influence on it. (2) The AE counts of coal specimen subjected to cyclic loading are greatly influenced by the confining pressure and the valley stress. With the increase in the confining pressure, the cumulative AE counts at the 1st cycle tend to increase but decrease at a cycle before failure; with the decrease in the valley stress, the cumulative AE counts per cycle increase in the relatively quiet phase. However, the loading-unloading rate has a little influence on it. (3) The failure mode of coal specimen subjected to cyclic loading is significantly influenced by the confining pressure. Under the uniaxial stress state, there is an inclined main fractured plane in the coal specimen, under the confining pressures of 5 and 10 MPa, the coal specimen represents dispersion failure. The loading-unloading rate and valley stress have little influence on it. (4) The AE ratio is proposed, and its evolution can better reflect the different stages of coal specimen failure under cyclic loading. (5) The influence of confining pressure on the broken degree of coal specimen subjected to cyclic loading is analyzed, and the higher the confining pressure, the more broken the failed coal specimen.

Influence of supercritical CO2 saturation on the failure process of hot dry rock with acoustic emission monitoring

2020 ◽  
Vol 374 ◽  
pp. 241-249 ◽  
Author(s):  
Honglian Li ◽  
Lei Zhou ◽  
Yiyu Lu ◽  
Fazhi Yan ◽  
Jiankun Zhou ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Supercritical Co2 ◽  
Failure Process ◽  
Acoustic Emission Monitoring ◽  
Hot Dry Rock ◽  
Emission Monitoring

Acoustic Emission Characteristics of Rock Failure under Uniaxial Loading

2011 ◽  
Vol 378-379 ◽  
pp. 43-46 ◽  
Author(s):  
Tao Xie ◽  
Qing Hui Jiang ◽  
Rui Chen ◽  
Wei Zhang
Keyword(s):  
Acoustic Emission ◽  
Failure Modes ◽  
Mechanical Performance ◽  
Progressive Failure ◽  
Failure Process ◽  
Testing Machine ◽  
Rock Failure ◽  
Rock Failure Process ◽  
State Variation ◽  
Acoustic Emission Test

With RMT-150C rock testing machine and AEWIN E1.86 DISP acoustic emission system applied, the acoustic emission test was accomplished with two kinds of rock samples including marble and granite under uniaxial compression. Cyclic loading and continuous loading were used through the experiment, and the mechanical performance and acoustic emission (AE) characteristics were obtained during the process of rock progressive failure. Details related to the relationship between amount of AE and stress-strain was given in this paper. A comparison between marble and granite was made as well following the general AE law, on the basis of which, the failure mechanism of rock mass was investigated. Finally, some conclusions can be summarized as follows:(1) AE activity features are different with stress state variation in rock failure process;(2) loading patterns make a direct impact on the failure process thereby affecting AE activities;(3)AE activities are various basing on the different types of rocks, structures and failure modes.

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