Development and testing of a serially multiplexed fiber optic sensor system is described.The sensor differs from conventional fiber optic acoustic systems,as it is capable of sensing AE emissions at several points alo...Development and testing of a serially multiplexed fiber optic sensor system is described.The sensor differs from conventional fiber optic acoustic systems,as it is capable of sensing AE emissions at several points along the length of a single fiber.Multiplexing provides for single channel detection of cracks and their locations in large structural systems. An algorithm was developed for signal recognition and tagging of the AE waveforms for detection of' crack locations,Labora- tory experiments on plain concrete beams and post-tensioned FRP tendons were pcrlormed to evaluate the crack detection capability of the sensor system.The acoustic emission sensor was able to detect initiation,growth and location of the cracks in concrete as well as in the FRP tendons.The AE system is potentially suitable lot applications involving health monitoring of structures following an earthquake.展开更多
A type of combined optical fiber interferometric acoustic emission sensor is proposed. The sensor can be independent on the laser source and make light interference by matching the lengths of two arms,so it can be use...A type of combined optical fiber interferometric acoustic emission sensor is proposed. The sensor can be independent on the laser source and make light interference by matching the lengths of two arms,so it can be used to monitor the health of large structure. Theoretical analyses indicate that the system can be equivalent to the Michelson interferometer with two optical fiber loop reflectors,and its sensitivity has been remarkably increased because of the decrease of the losses of light energy. PZT is powered by DC regulator to control the operating point of the system,so the system can accurately detect feeble vibration which is generated by ultrasonic waves propagating on the surface of solid. The amplitude and the frequency of feeble vibration signal are obtained by detecting the output light intensity of interferometer and using Fourier transform technique. The results indicate that the system can be used to detect the acoustic emission signals by the frequency characteristics.展开更多
With the rapid development of modern industries,the high-temperature piezoelectric sensors that can work in extreme environments are in great demand.In this work,langasite(La_(3)Ga_(5)SiO_(14),LGS),as a high-temperatu...With the rapid development of modern industries,the high-temperature piezoelectric sensors that can work in extreme environments are in great demand.In this work,langasite(La_(3)Ga_(5)SiO_(14),LGS),as a high-temperature piezoelectric crystal with stable electro-elastic performance,is used as core element,and air and porous Al_(2)O_(3) are selected as backing layers respectively to prepare two kinds of high-temperature acoustic emission(AE)sensors.The detection sensitivities at 25–500℃ are analyzed by the ball falling test and Hsu–Nielsen experiment.Under the condition of 25–500℃,the received amplitude signals by both sensors are maintained above 90 dB stimulated by the ZrO_(2) ceramic ball dropping.In the Hsu–Nielsen experiment,as the temperature rising from 25℃ to 500℃,the signal amplitude of sensor with air backing layer decays from 447 mV to 365 mV,while the signal amplitude varies from 270 mV to 203 mV for the sensor with porous Al_(2)O_(3) backing layer.Signiffcantly,compared with the bandwidth of the air-backing sensor(37–183 kHz),the sensor with porous Al_(2)O_(3) backing layer broadens bandwidth to 28–273 kHz.These results show that both these AE sensors have strong and stable response ability to AE signals at high-temperature of 500℃.Therefore,piezoelectric AE sensor based on LGS has great potential application in the ffeld of high-temperature structural health monitoring.展开更多
Manmade debris and natural meteoroids, travelling in the Low Earth Orbit at a speed of several kilometers per second, pose a severe safety concern to the spacecraft in service through the HyperVelocity Impact(HVI). To...Manmade debris and natural meteoroids, travelling in the Low Earth Orbit at a speed of several kilometers per second, pose a severe safety concern to the spacecraft in service through the HyperVelocity Impact(HVI). To address this issue, an investigation of shock Acoustic Emission(AE) waves induced by HVI to a downscaled two-layer Whipple shielding structure is performed,to realize a quantitative damage evaluation. Firstly a hybrid numerical model integrating smoothparticle hydrodynamics and finite element is built to obtain the wave response. The projectiles, with various impact velocities and directions, are modelled to impact the shielding structure with different thicknesses. Then experimental validation is carried out with built-in miniaturized piezoelectric sensors to in situ sense the HVI-induced AE waves. A quantitative agreement is obtained between numerical and experimental results, demonstrating the correctness of the hybrid model and facilitating the explanation of obtained AE signals in experiment. Based on the understanding of HVI-induced wave components, assessment of the damage severity, i.e., whether the outer shielding layer is perforated or not, is performed using the energy ratio between the regions of ‘‘high frequency" and ‘‘low frequency" in the acquired AE signals. Lastly, the direct-arrival fundamentalsymmetric wave mode is isolated from each sensing signal to be input into an enhanced delay-andsum algorithm, which visualizes HVI spots accurately and instantaneously with different sensor network configuration. All these works demonstrate the potential of quantitative, in situ, and real time HVI monitoring using miniaturized piezoelectric sensor network.展开更多
The acoustic emission (AE) method could be used to detect and locate partial discharges (PD) in cast-resin dry-type transformers.However,due to the high sound attenuation in the filled epoxy,the signal is prone to int...The acoustic emission (AE) method could be used to detect and locate partial discharges (PD) in cast-resin dry-type transformers.However,due to the high sound attenuation in the filled epoxy,the signal is prone to interference from external noises and thus,in practice,there is little possibility of detecting PD.In this study,two techniques were developed to alleviate the shortcomings of the AE method.First,a waveguide is installed on the high-voltage (HV) windings,so that the acoustic signals of PD will propagate to the AE sensors that are installed on both terminals of the waveguide.The location of the winding that has PD can then be detected from the difference in arrival time of the acoustic signals.Test results indicate that the waveguide technique is able to enhance the safety of a measurement system and offers the advantages of easy installation and higher flexibility.Second,a specially designed AE sensor pair is used to distinguish whether acoustic signals are generated by PD inside the HV winding or by the corona outside the transformers.Using these two techniques of waveguide and AE sensor pair not only greatly improves sensitivity but also increases the reliability of the measurement system.Practical test results show that the new techniques can be used to locate precisely the PD in HV windings.展开更多
Excavation of underground caverns,such as mountain tunnels and energy-storage caverns,may cause the damages to the surrounding rock as a result of the stress redistribution.In this influenced zone,new cracks and disco...Excavation of underground caverns,such as mountain tunnels and energy-storage caverns,may cause the damages to the surrounding rock as a result of the stress redistribution.In this influenced zone,new cracks and discontinuities are created or propagate in the rock mass.Therefore,it is effective to measure and evaluate the acoustic emission(AE)events generated by the rocks,which is a small elastic vibration,and permeability change.The authors have developed a long-term measurement device that incorporates an optical AE(O-AE)sensor,an optical pore pressure sensor,and an optical temperature sensor in a single multi-optical measurement probe(MOP).Japan Atomic Energy Agency has been conducting R&D activities to enhance the reliability of high-level radioactive waste(HLW)deep geological disposal technology.In a high-level radioactive disposal project,one of the challenges is the development of methods for long-term monitoring of rock mass behavior.Therefore,in January 2014,the long-term measurements of the hydro-mechanical behavior of the rock mass were launched using the developed MOP in the vicinity of 350 m below the surface at the Horonobe Underground Research Center.The measurement results show that AEs occur frequently up to 1.5 m from the wall during excavation.In addition,hydraulic conductivity increased by 2e4 orders of magnitude.Elastoplastic analysis revealed that the hydraulic behavior of the rock mass affected the pore pressure fluctuations and caused micro-fractures.Based on this,a conceptual model is developed to represent the excavation damaged zone(EDZ),which contributes to the safe geological disposal of radioactive waste.展开更多
The ultrasonic (US) wave detection and an acoustic emission (AE) linear location system are proposed, which employ fiber Bragg gratings (FBGs) as US wave sensors. In the theoretical analysis, the FBG sensor response t...The ultrasonic (US) wave detection and an acoustic emission (AE) linear location system are proposed, which employ fiber Bragg gratings (FBGs) as US wave sensors. In the theoretical analysis, the FBG sensor response to longitudinal US wave is investigated. The result indicates that the FBG wavelength can be modulated as static case when the grating length is much shorter than US wavelength. The experimental results of standard sinusoidal and spindle wave test agree well with the generated signal. Further research using two FBGs for realizing linear location is also achieved. The maximum linear location error is obtained as less than 5 mm. FBG-based US wave sensor and AE linear location provide useful tools for specific requirements.展开更多
In some applications in structural health monitoring (SHM), the acoustic emission (AE) detection technology is used in the high temperature environment. In this paper, a high-temperature-resistant AE sensing syste...In some applications in structural health monitoring (SHM), the acoustic emission (AE) detection technology is used in the high temperature environment. In this paper, a high-temperature-resistant AE sensing system is developed based on the fiber Bragg grating (FBG) sensor. A novel high temperature FBG AE sensor is designed With a high signal-to-noise ratio (SNR) compared with the traditional FBG AE sensor. The output responses of the designed sensors with different sensing fiber lengths also are investigated both theoretically and experimentally. Excellent AE detection results are obtained using the proposed FBG AE sensing system over a temperature range from 25℃ to 200℃. The experimental results indicate that this FBG AE sensing system can well meet the application requirement in AE detecting areas at high temperature.展开更多
基金National Science Foundation,Grant number CMS-9900338
文摘Development and testing of a serially multiplexed fiber optic sensor system is described.The sensor differs from conventional fiber optic acoustic systems,as it is capable of sensing AE emissions at several points along the length of a single fiber.Multiplexing provides for single channel detection of cracks and their locations in large structural systems. An algorithm was developed for signal recognition and tagging of the AE waveforms for detection of' crack locations,Labora- tory experiments on plain concrete beams and post-tensioned FRP tendons were pcrlormed to evaluate the crack detection capability of the sensor system.The acoustic emission sensor was able to detect initiation,growth and location of the cracks in concrete as well as in the FRP tendons.The AE system is potentially suitable lot applications involving health monitoring of structures following an earthquake.
基金the Fundamental Research Foundation of Harbin Engineering University, (grant number HEUF 04017)
文摘A type of combined optical fiber interferometric acoustic emission sensor is proposed. The sensor can be independent on the laser source and make light interference by matching the lengths of two arms,so it can be used to monitor the health of large structure. Theoretical analyses indicate that the system can be equivalent to the Michelson interferometer with two optical fiber loop reflectors,and its sensitivity has been remarkably increased because of the decrease of the losses of light energy. PZT is powered by DC regulator to control the operating point of the system,so the system can accurately detect feeble vibration which is generated by ultrasonic waves propagating on the surface of solid. The amplitude and the frequency of feeble vibration signal are obtained by detecting the output light intensity of interferometer and using Fourier transform technique. The results indicate that the system can be used to detect the acoustic emission signals by the frequency characteristics.
基金supported by the Shandong Provincial Natural Science Foundation(Grant No.ZR2020KA003)the Project of“20 Items of University”of Jinan(Grant No.T202009)+1 种基金Shandong Provincial Key Research and Development Plan(Grant No.2022CXPT045)the Primary Research&Development Plan of Shandong Province(Grant No.2019JZZY010313).
文摘With the rapid development of modern industries,the high-temperature piezoelectric sensors that can work in extreme environments are in great demand.In this work,langasite(La_(3)Ga_(5)SiO_(14),LGS),as a high-temperature piezoelectric crystal with stable electro-elastic performance,is used as core element,and air and porous Al_(2)O_(3) are selected as backing layers respectively to prepare two kinds of high-temperature acoustic emission(AE)sensors.The detection sensitivities at 25–500℃ are analyzed by the ball falling test and Hsu–Nielsen experiment.Under the condition of 25–500℃,the received amplitude signals by both sensors are maintained above 90 dB stimulated by the ZrO_(2) ceramic ball dropping.In the Hsu–Nielsen experiment,as the temperature rising from 25℃ to 500℃,the signal amplitude of sensor with air backing layer decays from 447 mV to 365 mV,while the signal amplitude varies from 270 mV to 203 mV for the sensor with porous Al_(2)O_(3) backing layer.Signiffcantly,compared with the bandwidth of the air-backing sensor(37–183 kHz),the sensor with porous Al_(2)O_(3) backing layer broadens bandwidth to 28–273 kHz.These results show that both these AE sensors have strong and stable response ability to AE signals at high-temperature of 500℃.Therefore,piezoelectric AE sensor based on LGS has great potential application in the ffeld of high-temperature structural health monitoring.
基金the Hong Kong Research Grants Council via a General Research Fund(Nos.15201416 and 15212417)the National Natural Science Foundation of China(No.51635008)
文摘Manmade debris and natural meteoroids, travelling in the Low Earth Orbit at a speed of several kilometers per second, pose a severe safety concern to the spacecraft in service through the HyperVelocity Impact(HVI). To address this issue, an investigation of shock Acoustic Emission(AE) waves induced by HVI to a downscaled two-layer Whipple shielding structure is performed,to realize a quantitative damage evaluation. Firstly a hybrid numerical model integrating smoothparticle hydrodynamics and finite element is built to obtain the wave response. The projectiles, with various impact velocities and directions, are modelled to impact the shielding structure with different thicknesses. Then experimental validation is carried out with built-in miniaturized piezoelectric sensors to in situ sense the HVI-induced AE waves. A quantitative agreement is obtained between numerical and experimental results, demonstrating the correctness of the hybrid model and facilitating the explanation of obtained AE signals in experiment. Based on the understanding of HVI-induced wave components, assessment of the damage severity, i.e., whether the outer shielding layer is perforated or not, is performed using the energy ratio between the regions of ‘‘high frequency" and ‘‘low frequency" in the acquired AE signals. Lastly, the direct-arrival fundamentalsymmetric wave mode is isolated from each sensing signal to be input into an enhanced delay-andsum algorithm, which visualizes HVI spots accurately and instantaneously with different sensor network configuration. All these works demonstrate the potential of quantitative, in situ, and real time HVI monitoring using miniaturized piezoelectric sensor network.
基金supported by the National Science Council,Taiwan (No.NSC 92-2622-E-006-142)the Program of Top 100 Universities Advancement,Ministry of Education,Taiwan
文摘The acoustic emission (AE) method could be used to detect and locate partial discharges (PD) in cast-resin dry-type transformers.However,due to the high sound attenuation in the filled epoxy,the signal is prone to interference from external noises and thus,in practice,there is little possibility of detecting PD.In this study,two techniques were developed to alleviate the shortcomings of the AE method.First,a waveguide is installed on the high-voltage (HV) windings,so that the acoustic signals of PD will propagate to the AE sensors that are installed on both terminals of the waveguide.The location of the winding that has PD can then be detected from the difference in arrival time of the acoustic signals.Test results indicate that the waveguide technique is able to enhance the safety of a measurement system and offers the advantages of easy installation and higher flexibility.Second,a specially designed AE sensor pair is used to distinguish whether acoustic signals are generated by PD inside the HV winding or by the corona outside the transformers.Using these two techniques of waveguide and AE sensor pair not only greatly improves sensitivity but also increases the reliability of the measurement system.Practical test results show that the new techniques can be used to locate precisely the PD in HV windings.
文摘Excavation of underground caverns,such as mountain tunnels and energy-storage caverns,may cause the damages to the surrounding rock as a result of the stress redistribution.In this influenced zone,new cracks and discontinuities are created or propagate in the rock mass.Therefore,it is effective to measure and evaluate the acoustic emission(AE)events generated by the rocks,which is a small elastic vibration,and permeability change.The authors have developed a long-term measurement device that incorporates an optical AE(O-AE)sensor,an optical pore pressure sensor,and an optical temperature sensor in a single multi-optical measurement probe(MOP).Japan Atomic Energy Agency has been conducting R&D activities to enhance the reliability of high-level radioactive waste(HLW)deep geological disposal technology.In a high-level radioactive disposal project,one of the challenges is the development of methods for long-term monitoring of rock mass behavior.Therefore,in January 2014,the long-term measurements of the hydro-mechanical behavior of the rock mass were launched using the developed MOP in the vicinity of 350 m below the surface at the Horonobe Underground Research Center.The measurement results show that AEs occur frequently up to 1.5 m from the wall during excavation.In addition,hydraulic conductivity increased by 2e4 orders of magnitude.Elastoplastic analysis revealed that the hydraulic behavior of the rock mass affected the pore pressure fluctuations and caused micro-fractures.Based on this,a conceptual model is developed to represent the excavation damaged zone(EDZ),which contributes to the safe geological disposal of radioactive waste.
基金supported by the National Natural Science Foundation of China (No. 61074163)the Natural Science Foundation of Shandong Province (No.ZR2011FQ025)the Independent Innovation Fund of Shandong University (No.2010GN066)
文摘The ultrasonic (US) wave detection and an acoustic emission (AE) linear location system are proposed, which employ fiber Bragg gratings (FBGs) as US wave sensors. In the theoretical analysis, the FBG sensor response to longitudinal US wave is investigated. The result indicates that the FBG wavelength can be modulated as static case when the grating length is much shorter than US wavelength. The experimental results of standard sinusoidal and spindle wave test agree well with the generated signal. Further research using two FBGs for realizing linear location is also achieved. The maximum linear location error is obtained as less than 5 mm. FBG-based US wave sensor and AE linear location provide useful tools for specific requirements.
基金This research is supported by the National Natural Science Foundation of China (Grant Nos. 61403233, 61503218, 61573226, and 61473176), the Excellent Young and Middle-Aged Scientist Award Grant of Shandong Province of China (No. BS2013DX018), and the Natural Science Foundation of Shandong Province for Outstanding Young Talents (No. ZR2015JL021).
文摘In some applications in structural health monitoring (SHM), the acoustic emission (AE) detection technology is used in the high temperature environment. In this paper, a high-temperature-resistant AE sensing system is developed based on the fiber Bragg grating (FBG) sensor. A novel high temperature FBG AE sensor is designed With a high signal-to-noise ratio (SNR) compared with the traditional FBG AE sensor. The output responses of the designed sensors with different sensing fiber lengths also are investigated both theoretically and experimentally. Excellent AE detection results are obtained using the proposed FBG AE sensing system over a temperature range from 25℃ to 200℃. The experimental results indicate that this FBG AE sensing system can well meet the application requirement in AE detecting areas at high temperature.
基金Projects(11447242,41272304,51209236,51274254)supported by the National Natural Science Foundation of ChinaProject(2015CB060200)supported by the National Basic Research Program of China