scholarly journals A Bayesian Approach for Localization of Acoustic Emission Source in Plate-Like Structures

2015 ◽  
Vol 2015 ◽  
pp. 1-14 ◽  
Author(s):  
Gang Yan ◽  
Jianfei Tang
Keyword(s):  
Acoustic Emission ◽  
Wave Velocity ◽  
Bayesian Approach ◽  
Experimental Studies ◽  
Source Location ◽  
Measured Time ◽  
Specific Frequency ◽  
Multiple Frequencies ◽  
Fusion Scheme ◽  
Localization Approach

This paper presents a Bayesian approach for localizing acoustic emission (AE) source in plate-like structures with consideration of uncertainties from modeling error and measurement noise. A PZT sensor network is deployed to monitor and acquire AE wave signals released by possible damage. By using continuous wavelet transform (CWT), the time-of-flight (TOF) information of the AE wave signals is extracted and measured. With a theoretical TOF model, a Bayesian parameter identification procedure is developed to obtain the AE source location and the wave velocity at a specific frequency simultaneously and meanwhile quantify their uncertainties. It is based on Bayes’ theorem that the posterior distributions of the parameters about the AE source location and the wave velocity are obtained by relating their priors and the likelihood of the measured time difference data. A Markov chain Monte Carlo (MCMC) algorithm is employed to draw samples to approximate the posteriors. Also, a data fusion scheme is performed to fuse results identified at multiple frequencies to increase accuracy and reduce uncertainty of the final localization results. Experimental studies on a stiffened aluminum panel with simulated AE events by pensile lead breaks (PLBs) are conducted to validate the proposed Bayesian AE source localization approach.

Acoustic Emission Source Location Based on Signal Features

2006 ◽  
Vol 13-14 ◽  
pp. 77-82 ◽  
Author(s):  
Michal Blahacek ◽  
M. Chlada ◽  
Z. Prevorovský
Keyword(s):  
Acoustic Emission ◽  
Elastic Wave ◽  
Wave Velocity ◽  
Arrival Time ◽  
Damage Mechanism ◽  
Source Location ◽  
Elastic Wave Velocity ◽  
New Approach ◽  
Signal Features ◽  
Artificial Neural Network Ann

Good knowledge of acoustic emission (AE) source location is the basic requirement for further damage mechanism characterization. Calculation of the AE source location is mostly based on arrival time differences of the signals recorded by different transducers. Error free arrival time determination is the crucial factor for the localization results accuracy together with the exact elastic wave velocity measurement. In the paper difficulties and limitations of the elastic wave velocity computation are shown. To solve the velocity and the time differences problems, new approach to AE source localization is described. The new method estimates the AE source coordinates using artificial neural network (ANN) processing extracted signal parameters. The ANN do not uses neither arrival time differences nor elastic wave velocities as input data. The new approach advantages are discussed in cases of both numerical and practical experiments. The experiments results are promising for the use of designed localization method in praxis.

scholarly journals The effect of liquid nitrogen cooling on coal cracking and mechanical properties

2018 ◽  
Vol 36 (6) ◽  
pp. 1609-1628 ◽  
Author(s):  
Chengzheng Cai ◽  
Feng Gao ◽  
Yugui Yang
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Acoustic Emission ◽  
Liquid Nitrogen ◽  
Wave Velocity ◽  
Count Rate ◽  
Initial State ◽  
Nitrogen Injection ◽  
Strength Tests ◽  
Liquid Nitrogen Cooling

Liquid nitrogen is a type of super-cryogenic fluid, which can cause the reservoir temperature to decrease significantly and thereby induce formation rock damage and cracking when it is injected into the wellbore as fracturing fluid. An experimental set-up was designed to monitor the acoustic emission signals of coal during its contact with cryogenic liquid nitrogen. Ultrasonic and tensile strength tests were then performed to investigate the effect of liquid nitrogen cooling on coal cracking and the changes in mechanical properties thereof. The results showed that acoustic emission phenomena occurred immediately as the coal sample came into contact with liquid nitrogen. This indicated that evident damage and cracking were induced by liquid nitrogen cooling. During liquid nitrogen injection, the ring-down count rate was high, and the cumulative ring-down counts also increased rapidly. Both the ring-down count rate and the cumulative ring-down counts during liquid nitrogen injection were much greater than those in the post-injection period. Liquid nitrogen cooling caused the micro-fissures inside the coal to expand, leading to a decrease in wave velocity and the deterioration in mechanical strength. The wave velocity, which was measured as soon as the sample was removed from the liquid nitrogen (i.e. the wave velocity was recorded in the cooling state), decreased by 14.46% on average. As the cryogenic samples recovered to room temperature, this value increased to 18.69%. In tensile strength tests, the tensile strengths of samples in cooling and cool-treated states were (on average) 17.39 and 31.43% less than those in initial state. These indicated that both during the cooling and heating processes, damage and cracking were generated within these coal samples, resulting in the acoustic emission phenomenon as well as the decrease in wave velocity and tensile strength.

Acoustic emission source location in composite structure by Voronoi construction using geodesic curve evolution

2009 ◽  
Vol 126 (5) ◽  
pp. 2324-2330 ◽  
Author(s):  
R. Gangadharan ◽  
G. Prasanna ◽  
M. R. Bhat ◽  
C. R. L. Murthy ◽  
S. Gopalakrishnan
Keyword(s):  
Acoustic Emission ◽  
Composite Structure ◽  
Source Location ◽  
Emission Source ◽  
Curve Evolution ◽  
Geodesic Curve ◽  
Acoustic Emission Source

Hyperbolic Source Location of Crack Related Acoustic Emission in Bone

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
John O'Toole ◽  
Leo Creedon ◽  
John Hession ◽  
Gordon Muir
Keyword(s):  
Acoustic Emission ◽  
Constant Velocity ◽  
Good Accuracy ◽  
Source Location ◽  
Bovine Bone ◽  
Accuracy And Precision ◽  
Median Error ◽  
Acoustic Emission Source ◽  
Three Point Bend Test ◽  
Point Bend

Little work has been done on the localization of microcracks in bone using acoustic emission. Microcrack localization is useful to study the fracture process in bone and to prevent fractures in patients. Locating microcracks that occur before fracture allows one to predict where fracture will occur if continued stress is applied to the bone. Two source location algorithms were developed to locate microcracks on rectangular bovine bone samples. The first algorithm uses a constant velocity approach which has some difficulty dealing with the anisotropic nature of bone. However, the second algorithm uses an iterative technique to estimate the correct velocity for the acoustic emission source location being located. In tests with simulated microcracks, the constant velocity algorithm achieves a median error of 1.78 mm (IQR 1.51 mm) and the variable velocity algorithm improves this to a median error of 0.70 mm (IQR 0.79 mm). An experiment in which the bone samples were loaded in a three point bend test until they fractured showed a good correlation between the computed location of detected microcracks and where the final fracture occurred. Microcracks can be located on bovine bone samples using acoustic emission with good accuracy and precision.

Acoustic Emission Tomography to Improve Source Location in Concrete Material Using SART

2014 ◽  
pp. 323-335
Author(s):  
Yu Jiang ◽  
FeiYun Xu ◽  
Antolino Gallego ◽  
Francisco Sagata ◽  
Oswaldo Gonçalves dos Santos Filho
Keyword(s):  
Acoustic Emission ◽  
Source Location ◽  
Emission Tomography ◽  
Concrete Material
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