Damage Evaluation of Concrete Based on Acoustic Emission b-Value

2013 ◽  
Vol 395-396 ◽  
pp. 515-519
Author(s):  
Zheng Zheng Xu ◽  
Yan Wang ◽  
Sheng Xing Wu ◽  
Yao Wang
Keyword(s):  
Acoustic Emission ◽  
Continuous Monitoring ◽  
Cement Mortar ◽  
B Value ◽  
Damage Evaluation ◽  
Technical Problems ◽  
Final Fracture ◽  
Concrete Damage ◽  
Damage Process ◽  
Important Position

Acoustic emission (AE) is capable of real time continuous monitoring and it's not sensitive to the geometry of components,so it's widely used in nondestructive testing of concrete. The AE b-value occupies an important position in the study of concrete damage evaluation as a parameter of AE technology. The basic theory of AE b-value and the related technical problems of AE b-value calculation was discussed. Then the research of AE b-value on concrete was reviewed. At last, the AE b-value in the damage process of cement mortar (CM) and polypropylene diber reinforced mortar (PFRM) under compression was studied and concluded that the trend of AE b-value of CM and PFRM was obviously different.The AE b-value is closely related to the formation and propagation of cracks in the damage process of concrete and it declines rapidly before final fracture occurs.

scholarly journals Experimental Study on the Troperty Degradation and Failure Mech- Anism of Weakly Cemented Sandstone Under Dry-wet Cycles

2021 ◽  
Author(s):  
Zhaoyang Song ◽  
Jie Tan ◽  
Zhiqiang Liu ◽  
Lihui Sun ◽  
Fangbo Ning
Keyword(s):  
Acoustic Emission ◽  
Longitudinal Wave ◽  
Loss Rate ◽  
B Value ◽  
Sudden Increase ◽  
Crack Penetration ◽  
Initial Stage ◽  
Failure State ◽  
Relative Stress ◽  
Damage Process

Abstract Taking the weakly cemented sandstone of Erdos, China, as the research object, the evolution law between the relative stress of weakly cemented sandstone and the multiparameters of the acoustic emission under different dry-wet cycles was explored, and the critical failure identification mode of weakly cemented sandstone under dry-wet cycles was established. The results show that as the number of dry-wet cycles increases, the wave velocity loss rate gradually increases. Overall, the longitudinal wave loss rate is larger than the shear wave loss rate, indicating that the longitudinal wave is more sensitive to the degradation of weakly cemented sandstone. With an increase in the number of dry-wet cycles, the fracture crack is mainly caused by the main crack penetration failure, and the secondary crack is significantly reduced. The fractal dimension decreases with an increase in the dry-wet cycles and reaches its maximum at 0 dry-wet cycles, which means that 0 dry-wet cycles witness the most complex morphology of fractures within the weakly cemented sandstone. This finding indicates that the dry-wet cycle inhibits the generation and expansion of fractures. The event rate appears to be close to 0 before the rupture, and then the platform oscillates, followed by a sudden increase. The acoustic emission b-value is relatively high during the initial stage and then decreases, which is the initial damage process. The elastoplastic phase rises again, the peak stage decreases rapidly, and the weakly cemented sandstone undergoes unstable damage. The change in the acoustic emission entropy value is exactly the opposite of the b-value change law. When the weakly cemented sandstone reaches the critical failure state under different dry-wet cycles, the relative stress value is 95%. The test results provide new methods and a basis for the damage evolution mechanism and fracture prediction of weakly cemented sandstone under dry-wet cycles.

Identification of the concrete damage degree based on the principal component analysis of acoustic emission signals and neural networks

2020 ◽  
Vol 62 (5) ◽  
pp. 517-524
Author(s):  
Yan Wang ◽  
G. Jie ◽  
W. Na ◽  
Y. Chao ◽  
Z. Li ◽  
...  
Keyword(s):  
Neural Network ◽  
Principal Component Analysis ◽  
Acoustic Emission ◽  
Principal Components ◽  
Principal Component ◽  
Damage Mechanism ◽  
Component Analysis ◽  
Damage Degree ◽  
Concrete Damage ◽  
Damage Process

Abstract This paper aims to improve the calculation efficiency and accuracy of concrete damage degree identification, and then to analyze the damage mechanism of concrete damage. First, the correlation analysis and principal component analysis of 15 characteristic parameters of acoustic emission signals accompanying concrete uniaxial compression and splitting damage process are performed through which the dimension is reduced into 5 non-correlated principal components. Then, based on the analysis of the relationship between each principal component and the damage and cracking mechanism of concrete, the damage degree of concrete is identified as an input variable of the BP neural network. The results show that the 5 principal components effectively eliminate redundant information and carry information on the failure mechanism of concrete damage and the damage process. Principal component analysis and the neural network are used to achieve the accurate recognition of acoustic emission parameters and the degree of concrete damage.

Quantitative acoustic emission investigation on the crack evolution in concrete prisms by frequency analysis based on wavelet packet transform

2021 ◽  
pp. 147592172110188
Author(s):  
Zonglian Wang ◽  
Keqin Ding ◽  
Huilan Ren ◽  
Jianguo Ning
Keyword(s):  
Acoustic Emission ◽  
Frequency Band ◽  
Wavelet Packet ◽  
Strain Energy Release ◽  
Crack Size ◽  
Frequency Bands ◽  
Emission Signal ◽  
Damage Process ◽  
Concrete Materials ◽  
Stage 1

To gain an insight into the evolution of micro-cracks in concrete materials, a quantitative acoustic emission investigation on the damage process of concrete prisms subjected to three-point bending loading was performed. Each of the monitored acoustic emission signals was processed by a two-level wavelet packet decomposition into four different frequency bands (AA2, DA2, AD2, and DD2), and the energy coefficients R1, R2, R3, and R4 that parameterize their characteristic frequency bands were calculated. By analyzing variations in energy coefficients of the lowest frequency band (AA2), R1, and the energy coefficients of the highest frequency band (DD2), R4, the whole damage process was divided into three stages: crack initiation, crack growth, and crack coalescence. An inverse relationship between the frequency of the acoustic emission signal emitted by the propagating crack and the crack size in concrete materials was acquired based on the damage theory of brittle materials and the strain energy release theory. The statistical analysis results of the experimental data indicated that the average of R1 increased in turn, and the average of R4 correspondingly decreased in turn from Stage 1 to Stage 3. It revealed that the frequencies of acoustic emission signals decreased gradually with the evolution of the damage of concrete prisms, which is in a good agreement with the theoretical analysis result.

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