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Study on Influence of Crack on the Blade Status Using FBGs

Photonic Sensors 2018年第1期8卷 63-69页

作者： Gang XU Lei LIANG Jianzhi LI Huaping MEI Hongli LI Yijun LIU National Engineering Laboratory of Fiber Optic Sensing Technology Wuhan University of Technology Wuhan 430070 China The Key Laboratory for Health Monitoring and Control of Large Structures Shijiazhuang 050043 China School of Mechanical Engineering Hubei Engineering University Xiaogan 432000 China

The status detection for rotating parts is difficult since the sensor is influenced by the rotation in the inflammable, explosive, and strong magnetic environment. Based on the fiber Bragg grating sensing technology, this paper studies the influence of the natural frequency and deformation of a rotor blade affected by the size of crack in the blade. Test results show that the speed of the equipment and blade excited vibration frequency are two main factors or deformation and vibration frequency of the blade. With an increase in the crack depth, the blade deformation is increased while the stimulated natural frequency of the blade is decreased; at a low rotational speed, the deformation is mainly caused by the rotating speed of the blade. On the contrary, the vibration blade itself contributes to the deformation at a high speed. During the process of full speed rotation, the influence of the rotational speed on the blade deformation almost remains the same, and the influence of the natural vibration on blade deformation is increased with an increase in the rotational speed.

关键词： Rotor blade fiber Bragg grating crack depth rotational speed blade frequency blade deformation

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Effective concrete surface crack detection based on extreme learning machine 8

Effective concrete surface crack detection based on extreme ...

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8th International Conference on Structural health monitoring of Intelligent Infrastructure, SHMII 2017

作者： Wang, Baoxian Zhao, Weigang Zhang, Hao Wang, Xinmin Zhang, Guangyuan Structural Health Monitoring and Control Institute Shijiazhuang Tiedao University Shijiazhuang050043 China Key Laboratory for Health Monitoring and Control of Large Structures Shijiazhuang050043 China Collaborative Innovation Center of Large Infrastructure Disaster Prevention and Reduction of Hebei Province China

ISBN: (纸本)9781925553055

Concrete surface crack detection has been an important field for the safety of civil engineering structure. However, under the background of high-density data acquiring demand, the existing crack detecting methods could not obtain the favorable efficiency and capability. In this work, we present a novel concrete surface crack detector for efficiently dealing with the massive crack images. Specifically, discrete cosine transformation is firstly utilized to extract the frequency domain characteristics of concrete surface images. Then, with the calculated image frequency features, an emergent learning technique (i.e., Extreme Learning Machine) is exploited to find the optimal separate hyper-plane between the crack object and backgrounds. Experiments on the crack images from the railway ballast-less track slab validate the effectiveness of the proposed method. © 2017 International Society for Structural health monitoring of Intelligent Infrastrucure. All rights reserved.

关键词： Frequency domain analysis

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Analysis of void-disease detection in ballastless track of high-speed railway based on directional filter 8

Analysis of void-disease detection in ballastless track of h...

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8th International Conference on Structural health monitoring of Intelligent Infrastructure, SHMII 2017

作者： Yang, Y. Zhao, W.G. Du, Y.L. Tian, X.S. School of Electrical and Electronic engineering Shijiazhuang Tiedao University Shijiazhuang China Key Laboratory for Health Monitoring and Control of Large Structures in Hebei Province Shijiazhuang Tiedao University Shijiazhuang China

ISBN: (纸本)9781925553055

Owing to the concealment of void disease in cement-asphalt (CA) mortar and the requirements for rapidness, ground penetrating radar (GPR) has a good application prospect in detecting disease on a high-speed railway. Track slab, the covering of the CA mortar layer, is a multi-layer reinforced concrete structure;strong reflection of reinforcement makes disease identification difficult. To solve this problem, directional models were established to study the feature difference of echoes between reinforcement and void disease, and a horizontal filter based on curvelet transform was proposed to identify the void disease in CA mortar. Finally, forward simulation was conducted to validate the performance of the presented algorithm. Results show that the horizontal filter method contributes to the identification of void diseases in the CA mortar layer which were located in the middle of the reinforcement group. This study promotes the application of GPR on disease detection in a high-speed railway. © 2017 International Society for Structural health monitoring of Intelligent Infrastrucure. All rights reserved.

关键词： Ground penetrating radar systems

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Effects of the reattachment on dry galloping in the critical Reynolds number range 9

Effects of the reattachment on dry galloping in the critical...

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9th Asia Pacific Conference on Wind Engineering, APCWE 2017

作者： Ma, Wenyong Liu, Qingkuan Liu, Xiaobing Key Laboratory for Health Monitoring and Control of Large Structure Shijiazhuang Tiedao University Hebei province China Department of Wind Science and Engineering Shijiazhuang Tiedao University Shijiazhuang City Hebei Province China

large amplitude vibrations of circular cylinders in the critical Reynolds number range are reproduced in wind tunnels. Displacements and wind pressure for the cylinders are measured synchronously to reveal the characteristics of aerodynamic force for the vibrating cylinders in a Reynolds number range where flow re-attaches on the rear of the cylinder. Effects of these reattachments on the aerodynamic forces and the vibrations are discussed. The results show that the reattachment can produce unsteady aerodynamic force and excite large amplitude vibration when it forms unstable separation bubble at the early critical Reynolds number range. Once it develops stable separation bubble, the reattachment mitigates the vibrations by creating strong negative aerodynamic damping. © 9th Asia Pacific Conference on Wind Engineering, APCWE 2017. All Rights Reserved.

关键词： Circular cylinders

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Effective intrusion detection for railway scene based on video analytics 8

Effective intrusion detection for railway scene based on vid...

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8th International Conference on Structural health monitoring of Intelligent Infrastructure, SHMII 2017

作者： Li, Y.D. Lin, Y.B. Zhang, C. Zhao, W.G. School of Electronic and Information Engineering North China University of Technology Beijing100041 China Key Laboratory for Health Monitoring and Control of Large Structures Shijiazhuang050043 China Institute of Structure Health Monitoring and Control Shijiazhuang Tiedao University Shijiazhuang050043 China

ISBN: (纸本)9781925553055

Intrusion detection for railway scene is the essential method to avoid railway accidents caused by the invasions of pedestrians, falling rocks, animals, etc. In this paper, an automatic computer-vision based scheme is proposed to detect abnormal events in the track area, and send pre-warning signals to the control center. First, background is estimated by Gaussian mixture models, and the targets are obtained from the difference image between foreground and background combining with threshold, morphological filtering and connected component labeling. Second, mean shift algorithm is used to track the invasive target. To improve the tracking robustness, Histogram of Oriented Gradient (HOG) is chosen as the feature space to establish the target model, which has strong discriminative ability and robustness over illumination variation and small distortion of object. Third, behavior analysis is conducted based on target trajectory to determine whether there exist abnormal events in the track area. If yes, alarm messages with high-definition pictures are sent to control center. The proposed method has been operated on K141 spot of Shuohuang railway. The practical running results show that the intrusion detection system is effective and robust in railway scene. © 2017 International Society for Structural health monitoring of Intelligent Infrastrucure. All rights reserved.

关键词： Intrusion detection

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Experimental study on wind pressure distribution and wind-induced interference effects on long-span spherical structure

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Jianzhu Jiegou Xuebao/Journal of Building structures 2016年第10期37卷 140-146页

作者： Liu, Qingkuan Lu, Zhaoliang Zheng, Yunfei Ma, Wenyong Liu, Xiaobing Structural Health Monitoring and Control Institute Shijiazhuang Tiedao University Shijiazhuang050043 China Key Laboratory for Structure Health Monitoring and Control in Hebei Province Shijiazhuang050043 China School of Civil Engineering Shijiazhuang Tiedao University Shijiazhuang050043 China

Spherical shell structure is very sensitive to wind loads. The wind load is one of the most important loads in structural design. By wind tunnel tests, simultaneous multi-pressure measurement on surface of spherical shell structure was carried out under different conditions to study the characteristics of wind load distribution and wind-induced interference effects. Results show that opened and closed sunroofs have significant effect on wind pressure distribution on the outer surface of the structure in partial region, especially, leeward side. For the inner surface of the structure, wind pressure become small when sunroof is closed, which is safe for the outer structure. Coal dump has no effect on wind pressure distribution along wind direction, while in cross wind direction it has effect. Different relative positions of adjacent structures have certain influence on wind-induced interference effects and different regions have different effects. © 2016, Editorial Office of Journal of Building structures. All right reserved.

关键词： Wind stress

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Analysis on GPR echo signal enhancement algorithm based on subspace sparsity deconvolution

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Journal of Engineering Science and Technology Review 2016年第6期9卷 43-51页

作者： Yong, Yang Yanliang, Du Weigang, Zhao Baoxian, Wang Hao, Zhao School of Mechanical Electronic and Control Engineering Beijing Jiaotong University Beijing100044 China The Key Laboratory for Health Monitoring and Control of Large Structures in Hebei Province Shijiazhuang Tiedao University Shijiazhuang050043 China Department of Urban and Civil Engineering Ibaraki University Hitachi316-8511 Japan

Strong reflection interference of rebar is the main barrier against ground-penetrating radar (GPR) detection of internal diseases in reinforced concrete structure. Deconvolution can strengthen GPR echo data through acquiring structural layer data. However, existing deconvolution echo signal processing algorithms cannot be applied to process the GPR echo data because of the hypothesis that the wavelet is in the minimum phase system, which is inconsistent with the attenuation of GPR wavelet during two-way travel time. To resolve this problem, a new subspace sparsity deconvolution algorithm was proposed in this paper to enhance the echo signal of rebar lower diseases. A wavelet signal attenuation model of layered structure was firstly established to analyse the influencing factors of disease echo signal attenuation under different conditions. On this basis, the sparsity deconvolution algorithm based on wavelet iteration was placed to enhance GPR echo signal quickly by using the constraint condition of subspace errors. The processing of GPR forward simulation data also reveals that the proposed algorithm can inhibit noises effectively and acquire layer information from the concrete structure when the local signal-to-noise ratio is larger than -19.7dB. The proposed algorithm is clearly superior to the existing automatic gain control algorithm with respect to the echo enhancement effect of GPR. Results show that this method overcomes the minimum phase restriction of deconvolution and it is of great significance to detect and recognize inter-layer diseases of high-speed railway ballastless tracks. © 2016 Eastern Macedonia and Thrace Institute of Technology. All rights reserved.

关键词： Concrete construction

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A Novel Rough-Surface Direct Wave Suppression Algorithm b ased on Energy Adaptive Analysis

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Journal of Engineering Science and Technology Review 2016年第4期9卷 202-208页

作者： Yong, Yang Weigang, Zhao Yanliang, Du Hao, Zhang School of Mechanical Electronic and Control Engineering Beijing Jiaotong University Beijing100044 China The Key Laboratory for Health Monitoring and Control of Large Structures in Hebei Province Shijiazhuang Tiedao University Shijiazhuang050043 China Department of Urban & Civil Engineering Ibaraki University Hitachi 316-8511 Japan

As a nondestructive testing technology, ground penetrating radar (GPR) is widely used in the detection and recognition of high-speed railway subgrade diseases. Rough-surface direct wave suppression caused by locomotive vibration and subgrade irregularity is a challenge in the GPR signal process. Flat-surface assumption makes traditional method difficult to apply directly to the rough terrain environment. To remove rough-surface direct wave and improve the signal-to-noise ratio, a new adaptive algorithm is proposed in this paper. First, according to the characteristic of electromagnetic wave propagation, the echo model of GPR was constructed, and the composition of ground radar echo signal was analyzed. Next, the eigenvalue and eigenvector of the echo signal and ground direct wave were studied. With the increase of relative permittivity, the energy eigenvector of direct wave and echo signal converged to the same vector space. On this basis, a rough-surface direct wave suppression framework based on energy feature adaptive analysis was proposed. Finally, a numerical simulation and field experiment were carried out to verify the feasibility of the algorithm. Results showed that the algorithm effectively suppresses the rough ground direct wave, and the processing result preserves the target echo more completely. Without intervention, this method can be applied in automatic direct wave suppression, which will promote the development of automatic identification technology in the detection of railway subgrade diseases. © 2016. Eastern Macedonia and Thrace Institute of Technology. All rights reserved.

关键词： Vector spaces

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THE INTERNAL CRACK IN PIEZOELECTRICPIEZOMAGNETIC SANDWICHED STRUCTURE UNDER IN-PLANE COUPLE LOADING

THE INTERNAL CRACK IN PIEZOELECTRICPIEZOMAGNETIC SANDWICHED ...

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2016年全国压电和声波理论及器件应用研讨会

作者： Xing ZHAO Jin-xi LIU Zheng-hua QIAN Department of Engineering Mechanics/The Key Laboratory for Health Monitoring and Control of Large Structures Shijiazhuang Tiedao University State Key Laboratory of Mechanics and Control of Mechanical Structures/College of Aerospace Engineering Nanjing University of Aeronautics and Astronautics

Background, Motivation and Objective The piezoelectric-piezomagnetic(PE-PM) sandwiched structures are consisted of layered piezoelectric and piezomagnetic materials. They are easy to be manufactured and possess superior magnetoelectric(ME) coupling effect. With these superiorities, the PE-PM sandwiched structures have been widely used in sensors, transducers and acoustic wave devices and so on. However, due to the fragility of the materials and complicated in-service loading conditions, the PE-PM sandwiched structures tend to fracture easily. So, it is essential to research the internal crack in PE-PM sandwiched structures under electro-magneto-mechanical coupled loadings. However, up until now, there is no paper studies the mode-I crack in PE-PM-PE sandwiched structure under in-plane electro-mechanical coupled loading. From the above, considering the magnetic field of piezoelectric material and the electric field of piezomagnetic material, a mode-I internal crack problem of a PM layer bonded to two PE layers is studied in this paper. Statement of Contribution/Methods This paper contributes to obtaining an analytical solution by using the integral transform technique. Firstly, the Fourier transforms are applied to the governing equations, and a set of appropriate solutions are obtained with some unknown functions. Then, substituting the appropriate solutions into boundary conditions meanwhile considering the magnetoelectric permeable crack plane conditions, we could derive the dual integral equations after the complex mathematical process. In order to obtain the magneto-electro-elastic field in the near of the crack tip, the dual integral equations are reduced into the singular integral equations with Cauchy kernel of the second kind. Finally, the Cauchy singular integral equations will be solved by Gauss-Jacobi collocation method. Meanwhile, the field intensity factors(FIFs) could be obtained. Results In this paper, an integral transform technique is employed to re

关键词： Mode I crack Piezoelectric-piezomagnetic sandwiched structure Field intensity factors Cauchy singular integral equation

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Mechanical and Failure Characteristics of Shear keys on Immersed Tunnel Segment Joints under Differential Settlements

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Procedia Engineering 2016年 166卷 373-378页

作者： Zhi-nan Hu Yong-li Xie School of Civil Engineering Shijiazhuang Tiedao University Shijiazhuang 050043 China The Key Laboratory for Health Monitoring and Control of Large Structures Shijiazhuang 050043 China College of Highway Chang’an University Xi’an 710064 China

In order to research mechanical and failure characteristics of shear keys on immersed tunnel segment joints, a 1:4.69 large scale immersed tunnel physical model test was conducted on a settlement platform. Bending and twisting working conditions of segment joints caused by uneven settlements and uneven back-silting were simulated, by means of controlling the lifting jacks under the settlement platform. Simultaneously, a 3-D numerical simulation which considered the nonlinearity of rubber pads and contacting effects between segment joints was carried out. The results shows that vertical shear keys have main contribution to resist expansion of segment joints in bending condition, and vertical shear keys on the soft layer have larger shear forces than that on the hard layer. In addition, shear stresses were mainly concentrated at the terminal corners and connecting corners between shear keys and segments. Correspondingly, at the terminal corners and connecting corners between shear key and segments appeared 30° ∼60° and 45° extending cracks respectively. At last, some structural strengthen suggestions on shear keys were offered for immersed tunnel design.

关键词： Immersed tunnel Segment joints Shear keys Failure characteristics Differential settlements

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