Abstract Advanced crack monitoring technique is the cornerstone of aircraft structural health monitoring. To achieve realtime crack monitoring of aircraft metal structures in the course of ser vice, a new crack monito...Abstract Advanced crack monitoring technique is the cornerstone of aircraft structural health monitoring. To achieve realtime crack monitoring of aircraft metal structures in the course of ser vice, a new crack monitoring method is proposed based on Cu coating sensor and electrical poten tial difference principle. Firstly, insulation treatment process was used to prepare a dielectric layer on structural substrate, such as an anodizing layer on 2AI2T4 aluminum alloy substrate, and then a Cu coating crack monitoring sensor was deposited on the structure fatigue critical parts by pulsed bias arc ion plating technology. Secondly, the damage consistency of the Cu coating sensor and 2A12T4 aluminum alloy substrate was investigated by static tensile experiment and fatigue test. The results show that strain values of the coating sensor and the 2A 12T4 aluminum alloy substrate measured by strain gauges are highly coincident in static tensile experiment and the sensor has excel lent fatigue damage consistency with the substrate. Thirdly, the fatigue performance discrepancy between samples with the coating sensor and original samples was investigated. The result shows that there is no obvious negative influence on the fatigue performance of the 2A12T4 aluminum alloy after preparing the Cu coating sensor on its surface. Finally, crack monitoring experiment was carried out with the Cu coating sensor. The experimental results indicate that the sensor is sensitive to crack, and crack origination and propagation can be monitored effectively through analyzing the change of electrical potential values of the coating sensor.展开更多
Polarimetric optical fibre sensors have been embedded within the 0° ply and close to the 0/90 interface of transparent cross-ply GFRP coupons. The laminate ply cracks may initiate and propagate across the coupon ...Polarimetric optical fibre sensors have been embedded within the 0° ply and close to the 0/90 interface of transparent cross-ply GFRP coupons. The laminate ply cracks may initiate and propagate across the coupon when the coupons were subjected to an increasing quasi-static load in a servo-hydraulic testing machine. Crack accumulation have been monitored using a long gauge-length extensometer. The response of the strain signal, the optical signal and the load signal to cracks at different positions in the coupon in relation to the extensometer and optical sensor positions have been acquired and compared by means of video images of the crack growth. The relationship between crack growth and sensor response was demonstrated. The displacement induced by a new transverse crack has been predicted and compared with experimental data.展开更多
Eddy-current (EC) testing is an effective electromagnetic non-destructive testing (NDT) technique.Planar eddy-current sensor arrays have several advantages such as good coherence,fast response speed,and high sensitivi...Eddy-current (EC) testing is an effective electromagnetic non-destructive testing (NDT) technique.Planar eddy-current sensor arrays have several advantages such as good coherence,fast response speed,and high sensitivity,which can be used for micro-damage inspection of crucial parts in mechanical equipments and aerospace aviation.The main purpose of this research is to detect the defect in a metallic material surface and identify the length of a crack using planar eddy-current sensor arrays in different directions.The principle and characteristics of planar eddy-current sensor arrays are introduced,and a crack length quantification algorithm in different directions is investigated.A damage quantitative detection system is established based on a field programmable gate array and ARM processor.The system is utilized to inspect the micro defect in a metallic material,which is carved to micro crack with size of 7mm(length)×0.1mm(width)×1mm(depth).The experimental data show that the sensor arrays can be used for the length measurement repeatedly,and that the uncertainty of the length measurement is below ±0.2mm.展开更多
The present paper focused on the detection of methanol and propanol using Pd-gate metal-oxide-semiconductor （MOS） sensor. Surface mor- phology and composition of the gate film were studied by scanning electron micro...The present paper focused on the detection of methanol and propanol using Pd-gate metal-oxide-semiconductor （MOS） sensor. Surface mor- phology and composition of the gate film were studied by scanning electron microscopy （SEM） and atomic force microscopy （AFM）. The response of the sensor for propanol and methanol was measured as shift in capacitance-voltage （C-V） and conductance-voltage （G-V） curves of the MOS structure. The sensitivity of the sensor towards methanol was found to be greater than that towards propanol. It was 58.2% for methanol and 32% for propanol （at 0.6 V, 1 MHz） in terms of capacitance measurements, while in terms of conductance results the sensitivity was found to be 57.2% for methanol and 38.9% for propanol at 1 kHz. The discontinuities or cracks present in the microstructure of the gate material are believed to be mainly responsible for the high sensitivity of the sensor, going with the decomposition of gas molecules and subsequent hydrogen permeation through Pd.展开更多
Crack monitoring plays a great role in modern structural health monitoring, however, most of the conventional crack inspections have disadvantages in terms of the accuracy, expense, reliability, durability and level o...Crack monitoring plays a great role in modern structural health monitoring, however, most of the conventional crack inspections have disadvantages in terms of the accuracy, expense, reliability, durability and level of instrumentation required. Thus, development of a simple and reliable crack inspection technique that allows continuous monitoring has been desired. In this paper, electrical potential technique and modern surface technology are employed together to develop a new structural surface crack monitoring method. A special crack monitoring coating sensor based on electrical potential technique was deposited on the hot spot of the structure by modern surface technology. The sensor consists of three layers： the isolated layer, the sensing layer and the protective layer. The isolated layer is prepared by anodic oxidation technology, the sensing layer is made of ion plated copper, and the protective layer is made of silicone. The thickness of each layer is at micrometer magnitude. The electrical conductivity of the sensor is very stable, and the fatigue performance of the specimen with or without coating sensor is nearly unchanged. The crack monitoring experiment result shows that there are two sudden rises of the coating sensor electrical potential values, corresponding to different stages of the crack initiation and propagation. Since the width of the surface coating sensor is only 0.5 mm, this crack monitoring sensor can detect the propagation of cracks less than 0.5 mm long. The method proposed takes the simplicity of electrical potential technique and can monitor surface crack of nearly all kinds of structures precisely. The results of this paper may form the basis of a new crack monitoring system.展开更多
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
Fiber loop ringdown (FLRD) has demonstrated to be capable of sensing various quantities, such as chemical species, pressure, refractive index, strain, temperature, etc.;and it has high potential for the development of...Fiber loop ringdown (FLRD) has demonstrated to be capable of sensing various quantities, such as chemical species, pressure, refractive index, strain, temperature, etc.;and it has high potential for the development of a sensor network. In the present work, we describe design and development of three different types of FLRD sensors for water, cracks, and temperature sensing in concrete structures. All of the three aforementioned sensors were indigenously developed very recently in our laboratory and their capabilities of detecting the respective quantities were demonstrated. Later, all of the sensors were installed in a test grout cube for real-time monitoring. This work presents the results obtained in the laboratory-based experiments as well as the results from the real-time monitoring process in the test cube.展开更多
铁路轨道与车轮长期滚动接触,容易产生疲劳裂纹,导致钢轨表面剥离甚至钢轨断裂等严重问题,因此开展裂纹尺寸、扩展深度以及裂纹形状的检测与定量表征具有重要意义。设计搭建了采用阵列式传感器交流电磁场检测技术(Alternating current f...铁路轨道与车轮长期滚动接触,容易产生疲劳裂纹,导致钢轨表面剥离甚至钢轨断裂等严重问题,因此开展裂纹尺寸、扩展深度以及裂纹形状的检测与定量表征具有重要意义。设计搭建了采用阵列式传感器交流电磁场检测技术(Alternating current field measurement,ACFM)的钢轨裂纹检测系统。结合检测信号等值线彩色图研究了不同长度、不同深度、不同形状(簇状、Y形和W形)裂纹对ACFM信号的影响规律,分析了裂纹形状对交流电磁场检测信号影响机理。研究结果表明:随着裂纹长度与深度的增加,B_(x)信号谷值减小,B_(z)信号出现越来越明显的双极值特征,蝶形图中缺陷环面积逐渐增加,表明裂纹引起的磁场扰动逐渐变大,B_(z)信号相比B_(x)信号对裂纹长度与深度的变化更敏感;随簇状裂纹条数的增加,裂纹周围的B_(x)和B_(z)信号强度逐渐增加,B_(x)信号波峰位置的连线可反应裂纹走向;W形裂纹的B_(x)信号出现了三个极值,B_(z)信号出现了对称分布的极值特征;Y形裂纹的B_(x)信号出现了六个极值,B_(z)信号出现了四个极值。利用阵列式传感器ACFM信号的等值线彩色图可实现对复杂形状裂纹的识别和表征。展开更多
基金co-supported by the National Natural Science Foundation of China(No.51201182)
文摘Abstract Advanced crack monitoring technique is the cornerstone of aircraft structural health monitoring. To achieve realtime crack monitoring of aircraft metal structures in the course of ser vice, a new crack monitoring method is proposed based on Cu coating sensor and electrical poten tial difference principle. Firstly, insulation treatment process was used to prepare a dielectric layer on structural substrate, such as an anodizing layer on 2AI2T4 aluminum alloy substrate, and then a Cu coating crack monitoring sensor was deposited on the structure fatigue critical parts by pulsed bias arc ion plating technology. Secondly, the damage consistency of the Cu coating sensor and 2A12T4 aluminum alloy substrate was investigated by static tensile experiment and fatigue test. The results show that strain values of the coating sensor and the 2A 12T4 aluminum alloy substrate measured by strain gauges are highly coincident in static tensile experiment and the sensor has excel lent fatigue damage consistency with the substrate. Thirdly, the fatigue performance discrepancy between samples with the coating sensor and original samples was investigated. The result shows that there is no obvious negative influence on the fatigue performance of the 2A12T4 aluminum alloy after preparing the Cu coating sensor on its surface. Finally, crack monitoring experiment was carried out with the Cu coating sensor. The experimental results indicate that the sensor is sensitive to crack, and crack origination and propagation can be monitored effectively through analyzing the change of electrical potential values of the coating sensor.
文摘Polarimetric optical fibre sensors have been embedded within the 0° ply and close to the 0/90 interface of transparent cross-ply GFRP coupons. The laminate ply cracks may initiate and propagate across the coupon when the coupons were subjected to an increasing quasi-static load in a servo-hydraulic testing machine. Crack accumulation have been monitored using a long gauge-length extensometer. The response of the strain signal, the optical signal and the load signal to cracks at different positions in the coupon in relation to the extensometer and optical sensor positions have been acquired and compared by means of video images of the crack growth. The relationship between crack growth and sensor response was demonstrated. The displacement induced by a new transverse crack has been predicted and compared with experimental data.
基金supported by the National Natural Science Foundation of China (No.61171460)
文摘Eddy-current (EC) testing is an effective electromagnetic non-destructive testing (NDT) technique.Planar eddy-current sensor arrays have several advantages such as good coherence,fast response speed,and high sensitivity,which can be used for micro-damage inspection of crucial parts in mechanical equipments and aerospace aviation.The main purpose of this research is to detect the defect in a metallic material surface and identify the length of a crack using planar eddy-current sensor arrays in different directions.The principle and characteristics of planar eddy-current sensor arrays are introduced,and a crack length quantification algorithm in different directions is investigated.A damage quantitative detection system is established based on a field programmable gate array and ARM processor.The system is utilized to inspect the micro defect in a metallic material,which is carved to micro crack with size of 7mm(length)×0.1mm(width)×1mm(depth).The experimental data show that the sensor arrays can be used for the length measurement repeatedly,and that the uncertainty of the length measurement is below ±0.2mm.
文摘The present paper focused on the detection of methanol and propanol using Pd-gate metal-oxide-semiconductor （MOS） sensor. Surface mor- phology and composition of the gate film were studied by scanning electron microscopy （SEM） and atomic force microscopy （AFM）. The response of the sensor for propanol and methanol was measured as shift in capacitance-voltage （C-V） and conductance-voltage （G-V） curves of the MOS structure. The sensitivity of the sensor towards methanol was found to be greater than that towards propanol. It was 58.2% for methanol and 32% for propanol （at 0.6 V, 1 MHz） in terms of capacitance measurements, while in terms of conductance results the sensitivity was found to be 57.2% for methanol and 38.9% for propanol at 1 kHz. The discontinuities or cracks present in the microstructure of the gate material are believed to be mainly responsible for the high sensitivity of the sensor, going with the decomposition of gas molecules and subsequent hydrogen permeation through Pd.
基金supported by National Hi-tech Research and Development Program of China (863 Program, Grant No. 2009AA03Z103)Scientific Research Foundation for the Returned Overseas Chinese Scholars of Ministry of Education of China (Grant No. [2006]331)
文摘Crack monitoring plays a great role in modern structural health monitoring, however, most of the conventional crack inspections have disadvantages in terms of the accuracy, expense, reliability, durability and level of instrumentation required. Thus, development of a simple and reliable crack inspection technique that allows continuous monitoring has been desired. In this paper, electrical potential technique and modern surface technology are employed together to develop a new structural surface crack monitoring method. A special crack monitoring coating sensor based on electrical potential technique was deposited on the hot spot of the structure by modern surface technology. The sensor consists of three layers： the isolated layer, the sensing layer and the protective layer. The isolated layer is prepared by anodic oxidation technology, the sensing layer is made of ion plated copper, and the protective layer is made of silicone. The thickness of each layer is at micrometer magnitude. The electrical conductivity of the sensor is very stable, and the fatigue performance of the specimen with or without coating sensor is nearly unchanged. The crack monitoring experiment result shows that there are two sudden rises of the coating sensor electrical potential values, corresponding to different stages of the crack initiation and propagation. Since the width of the surface coating sensor is only 0.5 mm, this crack monitoring sensor can detect the propagation of cracks less than 0.5 mm long. The method proposed takes the simplicity of electrical potential technique and can monitor surface crack of nearly all kinds of structures precisely. The results of this paper may form the basis of a new crack monitoring system.
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.
文摘Fiber loop ringdown (FLRD) has demonstrated to be capable of sensing various quantities, such as chemical species, pressure, refractive index, strain, temperature, etc.;and it has high potential for the development of a sensor network. In the present work, we describe design and development of three different types of FLRD sensors for water, cracks, and temperature sensing in concrete structures. All of the three aforementioned sensors were indigenously developed very recently in our laboratory and their capabilities of detecting the respective quantities were demonstrated. Later, all of the sensors were installed in a test grout cube for real-time monitoring. This work presents the results obtained in the laboratory-based experiments as well as the results from the real-time monitoring process in the test cube.
文摘铁路轨道与车轮长期滚动接触,容易产生疲劳裂纹,导致钢轨表面剥离甚至钢轨断裂等严重问题,因此开展裂纹尺寸、扩展深度以及裂纹形状的检测与定量表征具有重要意义。设计搭建了采用阵列式传感器交流电磁场检测技术(Alternating current field measurement,ACFM)的钢轨裂纹检测系统。结合检测信号等值线彩色图研究了不同长度、不同深度、不同形状(簇状、Y形和W形)裂纹对ACFM信号的影响规律,分析了裂纹形状对交流电磁场检测信号影响机理。研究结果表明:随着裂纹长度与深度的增加,B_(x)信号谷值减小,B_(z)信号出现越来越明显的双极值特征,蝶形图中缺陷环面积逐渐增加,表明裂纹引起的磁场扰动逐渐变大,B_(z)信号相比B_(x)信号对裂纹长度与深度的变化更敏感;随簇状裂纹条数的增加,裂纹周围的B_(x)和B_(z)信号强度逐渐增加,B_(x)信号波峰位置的连线可反应裂纹走向;W形裂纹的B_(x)信号出现了三个极值,B_(z)信号出现了对称分布的极值特征;Y形裂纹的B_(x)信号出现了六个极值,B_(z)信号出现了四个极值。利用阵列式传感器ACFM信号的等值线彩色图可实现对复杂形状裂纹的识别和表征。
