scholarly journals Scale Effect on the Anisotropy of Acoustic Emission in Coal

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Honghua Song ◽  
Yixin Zhao ◽  
Yaodong Jiang ◽  
Jiehao Wang
Keyword(s):  
Acoustic Emission ◽  
Energy Dissipation ◽  
Scale Effect ◽  
Specimen Size ◽  
Exponential Equation ◽  
Volume Number ◽  
Ae Energy ◽  
Negative Exponential ◽  
Ae Counts ◽  
Cumulative Ae Energy

Acoustic emission (AE) in coal is anisotropic. In this paper, we investigate the microstructure-related scale effect on the anisotropic AE feature in coal at unconfined loading process. A series of coal specimens were processed with diameters of 25 mm, 38 mm, 50 mm, and 75 mm (height to diameter ratio of 2) and anisotropic angles of 0°, 15°, 30°, 45°, 60°, and 90°. The cumulative AE counts and energy dissipation increase with the specimen size, while the energy dissipation per AE count behaves in the opposite way. This may result from the increasing amount of both preexisting discontinuities and cracks (volume/number) needed for specimen failure and the lower energy dissipation AE counts generated by them. The effect of microstructures on the anisotropies of AE weakens with the increasing specimen size. The TRFD and its anisotropy reduce as the specimen size increases, and the reduction of fractal dimension is most pronounced at the anisotropic angle of 45°. The correlation between TRFD and cumulative AE energy in the specimens with different sizes are separately consistent with the negative exponential equation proposed by Xie and Pariseau. With the specimen size gain, the reduction of the TRFD weakens with the increasing amount of cumulative absolute AE energy.

scholarly journals Acoustic Emission Experimental Research of the Damage Characteristics of Raw Coal under Different Loading and Unloading Rates

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Minbo Zhang ◽  
Li Cui ◽  
Wenjun Hu ◽  
Jinlei Du ◽  
Zhen Zhang ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Practical Significance ◽  
Emission Characteristic ◽  
Strain Rates ◽  
Characteristic Parameters ◽  
Energy Increase ◽  
Damage Models ◽  
Ae Energy ◽  
Ae Counts ◽  
Cumulative Ae Energy

In this study, triaxial load failure experiments of coal samples under different strain rates and different confining pressure unloading rates were carried out using an RTX-1000 rock triaxial apparatus, and the acoustic emission characteristic parameters of a Micro-II acoustic emission imaging acquisition instrument were used to study the acoustic emission characteristics and damage deformation law of coals under different conditions. Damage models were constructed on the basis of the characteristic parameters to analyze the damage law of coal samples. Experimental results show that the acoustic emission (AE) counts and AE energy of the coal samples decrease, but the peak AE counts and peak AE energy increase with the increase in strain rates. The cumulative AE counts decrease from 9902 times to 6899 times, the peak counts increase from 209 times to 431 times, the cumulative AE energy decreases from 6986 aJ to 3786 aJ, and the peak AE energy increases from 129 aJ to 312 aJ. The overall level of the AE count rates and the AE energy of the coal samples decrease, but the peak AE counts and peak AE energy increase with the increase in unloading rates. The cumulative AE counts decrease from 18,689 times to 16,842 times, the peak AE count rates increase from 245 times/s to 535 times/s, the cumulative AE energy decreases from 9846 aJ to 7430 aJ, and the peak energy increases from 257 aJ to 587 aJ. The damage models are constructed on the basis of AE counts, and the comparative experimental and theoretical curves are analyzed to obtain a higher fitness close to 1. The damage threshold increases from 0.30 to 0.50 and from 0.34 to 0.55, and the damage amount increases from 0.50 to 0.60 and from 0.34 to 0.62 with the increase in strain rates and unloading rates. The research results have practical significance for revealing the mechanism of disaster occurrence in actual engineering excavation and proposing engineering measures to prevent coal rock damage and disaster occurrence.

scholarly journals Tensile Properties Analysis Of 3D Flat-Knitted Inlay Fabric Reinforced Composites Using Acoustic Emission

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Jiangtao Tan ◽  
Gaoming Jiang ◽  
Guangjun Wu ◽  
Pibo Ma
Keyword(s):  
Acoustic Emission ◽  
Tensile Properties ◽  
Reinforced Composites ◽  
Fiber Breakage ◽  
Damage Mechanisms ◽  
Duration Time ◽  
Ae Energy ◽  
Matrix Fracture ◽  
Interlock Structure ◽  
Cumulative Ae Energy

Abstract In this work, based on the quasi-static tensile test and acoustic emission technology, the tensile properties of two types of three-dimensional flat-knitted inlay fabrics reinforced composites are investigated, and the acoustic emission characteristic parameters of various damage mechanisms are obtained. The transverse tensile process of specimens could be divided into the elastic stage, yield stage, and fracture stage. We found that, compared with the fluctuation of the stress-strain curve in the yield stage, weft insertion yarns in composite with interlock structure broke almost simultaneously, while the composite with plain stitch broke successively. The transverse and longitudinal tensile strength of the composite with interlock structure was 44.70% and 28.63% higher than the composite with plain structure, respectively. The SEM micrographs showed that the damage mechanism of the composites was matrix fracture, fiber-matrix debonding, and fiber breakage. The amplitude ranges of the three damage mechanisms were 50–65 dB, 65–80 dB, and 90–100 dB, respectively, and the frequency ranges were 35–114 kHz, 116–187 kHz, and 252–281 kHz, respectively. Fiber-matrix debonding and matrix fracture had large cumulative AE energy, numerous events, and long duration time, while fiber breakage had the characteristics of large amplitude, high frequency, low cumulative AE energy, few events, and short duration time.

Research on damage evolution of deep formation rock based on acoustic emission test

2020 ◽  
Vol 30 (1) ◽  
pp. 145-159
Author(s):  
Yong Tian ◽  
Rangang Yu ◽  
Yin Zhang ◽  
Xinbo Zhao
Keyword(s):  
Acoustic Emission ◽  
Cyclic Loading ◽  
Damage Evolution ◽  
Initial Moment ◽  
Damage Development ◽  
Loading Test ◽  
Cyclic Loading Test ◽  
Ae Energy ◽  
Rock Specimens ◽  
Cumulative Ae Energy

The study of rock damage evolution is of great significance in the field of underground engineering. In this paper, the damage development of deep formation rock was quantitatively evaluated by acoustic emission (AE) test. The Young’s modulus of the test rock specimens under ideal intact state was obtained by assuming a linear relationship between the AE rate parameter and the damage variation based on the rate process theory. Through the multi-stage cyclic loading test, the damage parameters corresponding to the peak stress of the previous stage were calculated by using the tangent modulus at the initial moment. The results showed that there was abrupt transition stage of damage development with the linear increase of stress. The damage parameter curves of rock specimens during loading process were obtained by using the method of cumulative AE energy, and the development trend of the curves was analyzed simply by combining the concepts of crack initiation stress and crack damage stress. Comparing the two methods of obtaining damage parameters by using cyclic loading test and cumulative AE energy, the results of them were highly consistent except for some deviation in the initial and final stages.

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 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.

scholarly journals Energy dissipation via acoustic emission in ductile crack initiation

2016 ◽  
Vol 199 (1) ◽  
pp. 89-104 ◽  
Author(s):  
J. A. Cuadra ◽  
K. P. Baxevanakis ◽  
M. Mazzotti ◽  
I. Bartoli ◽  
A. Kontsos
Keyword(s):  
Acoustic Emission ◽  
Energy Dissipation ◽  
Crack Initiation ◽  
Ductile Crack

The study of a fatigue crack propagation in titanium Grade 2 using analysis of energy dissipation and acoustic emission data

2019 ◽  
Vol 210 ◽  
pp. 312-319 ◽  
Author(s):  
A.N. Vshivkov ◽  
A. Yu. Iziumova ◽  
I.A. Panteleev ◽  
A.V. Ilinykh ◽  
V.E. Wildemann ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Fatigue Crack ◽  
Energy Dissipation ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Emission Data ◽  
Titanium Grade

Study on the Effect of Cl- Concentration on the Corrosion Fatigue Damage in a Rolled AZ31B Magnesium Alloy by Acoustic Emission

2007 ◽  
Vol 353-358 ◽  
pp. 327-330 ◽  
Author(s):  
Hua Mao Zhou ◽  
Jian Qiu Wang ◽  
Qi Shan Zang ◽  
En Hou Han
Keyword(s):  
Acoustic Emission ◽  
Magnesium Alloy ◽  
Energy Release ◽  
Fatigue Damage ◽  
Corrosion Fatigue ◽  
Room Temperature ◽  
Fatigue Performance ◽  
Ae Energy ◽  
Magnesium Alloy Az31b ◽  
Wrought Magnesium Alloy

The fatigue performance of one widely used wrought magnesium alloy AZ31B in rolled form was studied using acoustic emission (AE). AE energy release during corrosion fatigue (CF) testing was measured at room temperature. It is found that AE energy release can express corrosion fatigue damage experienced by the material.

Sign in / Sign up

Export Citation Format

Share Document