Structural Health Monitoring: Research and Applications

文章题目 页数

作者: Maryam Varmazyar, Nicholas Haritos, Michael Kirley, Tim Peterson
摘要: This paper describes a new global damage identification framework for the continuous/periodic monitoring of civil structures. In order to localize and estimate the severity of damage regions, a one-stage model-based Bayesian probabilistic damage detection approach is proposed. This method, which is based on the response power spectral density of the structure, enjoys the advantage of broadband frequency information and can be implemented on input-output as well as output-only damage identification studies. A parallel genetic algorithm is subsequently used to evolve the optimal model parameters introduced for different damage conditions. Given the complex search space and the need to perform multiple time-consuming objective function evaluations, a parallel meta-heuristic provides a robust optimization tool in this domain. It is shown that this approach is capable of detecting structural damage in both noisy and noise-free environments.
1
作者: T.J. Shelley, Chin Kian Liew
摘要: This study proposes a new nondestructive evaluation methodology named laser lock-in thermography (LLT) for fatigue crack detection. LLT utilizes a high power continuous wave (CW) laser as a heat generation source for lock-in thermography instead of commonly used flash and halogen lamps. The advantages of the proposed LLT method are that (1) the laser heat source can be positioned at an extended distance from a target structure thank to the directionality and low energy loss of the laser source, (2) thermal image degradation due to surrounding temperature disturbances can be minimized because of high temperature gradient generated by the laser source and (3) a large target surface can be inspected using a scanning laser heat source. The developed LLT system is composed of a modulated high power CW laser, galvanometer and infrared camera. Then, a holder exponent-based data processing algorithm is proposed for intuitive damage evaluation. The developed LLT is employed to detect a micro fatigue crack in a metal plate. The test result confirms that 5 μm (or smaller) fatigue crack in a dog-bone shape aluminum plate with a dimension of 400 x 140 x 3 mm3 can be detected.
12
作者: Samir Mustapha, Lin Ye
摘要: Damage detection using guided waves in the inspection of tapered sandwich structures with high density foam core (Dyvinicell HP100) is investigated. Characterisation of the fundamental symmetric and anti-symmetric Lamb wave modes is carried out in terms of their velocity and magnitude variation as they encounter a change in the thickness of a composite sandwich plate, aiming at optimising the mode selection to improve the capability and increase the sensitivity of guided waves in inspection of tapered sandwich structures. In addition, an imaging algorithm based on time reversal is developed to detect multiple debonding and artificial damage in tapered sandwich panels based guided waves from an active sensor network. The correlation coefficients between the original and reconstructed time reversal signals are calculated to define a damage index for individual sensing paths, which are used later in the fusion process, identifying the presence of damage in the monitoring area enclosed by the active sensor network. The results confirm that the incident wave signals and their reconstructed time-reversed counterparts can be used to accurately detect the debonding/damage in tapered sandwich structures.
25
作者: Xing Hua Chen, Piotr Omenzetter
摘要: Because of the critical role that bridges play in land transport networks and broader economy, the assessment of existing bridges is gradually becoming a global concern. Structural health monitoring (SHM) systems have been installed on many bridges to provide data for the evaluation of bridge performance and safety. The challenge for bridge engineers is now to make use of the data and convert them into usable information and knowledge. Integrating SHM data with reliability analysis procedures offers a useful and practical methodology for bridge assessment since reliability is an important performance index and reliability-based procedures have the capability of accommodating uncertainties in structural models, responses, loads and monitoring data. In this paper, an approach for integrating SHM data in a reliability assessment framework is proposed. The reliability of the bridge is quantified by incorporating SHM information in the resistance, load and structural models. Advanced modeling tools and techniques, such as finite element analysis, finite model updating and Bayesian updating, are used for the reliability computations. Data from the SHM system installed on the Newmarket Viaduct, a newly constructed, 12-span, post-tensioned box girder bridge erected by the balanced cantilever method in Auckland, New Zealand, are also presented in this paper and used to explain the proposed framework.
39
作者: Chin Hsiung Loh, Ming Che Chen
摘要: This paper deals with the problem of a bridge structure identification using output-only vibration measurements under changing environmental conditions. Two key issues of a real-life monitoring system are addressed through analysis. The first issue is the identification of structural dynamic characteristics directly from measurements under operating conditions. The covariance-driven recursive stochastic subspace identification (RSSI-COV) algorithm is applied to extract the system dynamic characteristics. The second issue is to distinguish the system dynamic features caused by abnormality from those caused by environmental and operational variations, such as temperature, and traffic loading. In this study a solution is proposed to model and remove the uncertainty due to environmental effects from the identified system dynamic characteristics from on-going measurements. Nonlinear principal component analysis incorporated with AANN is employed to distinguish the dynamic feature changes caused by abnormality from those caused by environmental and operational variation (i.e. ambient temperature and traffic loadings). Finally, field experiment of a bridge is conducted. The variation of the identified system natural frequencies was discussed by using the proposed method.
52
作者: Mohd Hafizi Zohari, Jayantha Ananda Epaarachchi, K.T. Lau
摘要: Acoustic Emission (AE) is one of the popular non-destructive (NDT) techniques and its applications have increased subsequently for Structural Health Monitoring (SHM). During the past few decades, many successful research works have evidently shown remarkable capability of AE for early damage detection of composite materials. This paper investigated the application of single channel acoustic emission (AE) source location detection method, utilizing time-frequency analysis for thin composite plates. Besides, failure characterization using Modal Acoustic Emission (MAE) also presented. Modal analysis of AE signals or MAE can offers a better theoretical background for acoustic emission analysis; which is necessary to get more qualitative and quantitative result and therefore, increase the reliability of early failure characterization for thin composite plates. For this study, tensile tests were conducted on the glass fiber epoxy resin specimen with small notch; and four channels of acoustic emission system were used to acquire AE signals. The results revealed that in practical, single channel AE source location was difficult to be done. Also, the study has successfully showed that matrix cracks and fiber fracture produced AE signals which dominated by symmetric wave mode.
65
作者: Yun Kyu An, Ji Min Kim, Hoon Sohn
摘要: This study proposes a new nondestructive evaluation methodology named laser lock-in thermography (LLT) for fatigue crack detection. LLT utilizes a high power continuous wave (CW) laser as a heat generation source for lock-in thermography instead of commonly used flash and halogen lamps. The advantages of the proposed LLT method are that (1) the laser heat source can be positioned at an extended distance from a target structure thank to the directionality and low energy loss of the laser source, (2) thermal image degradation due to surrounding temperature disturbances can be minimized because of high temperature gradient generated by the laser source and (3) a large target surface can be inspected using a scanning laser heat source. The developed LLT system is composed of a modulated high power CW laser, galvanometer and infrared camera. Then, a holder exponent-based data processing algorithm is proposed for intuitive damage evaluation. The developed LLT is employed to detect a micro fatigue crack in a metal plate. The test result confirms that 5 μm (or smaller) fatigue crack in a dog-bone shape aluminum plate with a dimension of 400 x 140 x 3 mm3 can be detected.
76
作者: Paritosh Giri, Jung Ryul Lee
摘要: With commercially viable global wind power potential, wind energy penetration is further expected to rise, as will the related problems. One issue is the collision of wind turbine blades with the tower during operation. Structured health monitoring is required to improve operational safety, minimize the risk of sudden failure or total breakdown, ensure reliable power generation, and reduce wind turbine life cycle costs. Large numbers of sensors such as fiber Bragg grating and piezoelectric devices have been attached to the structure, a design that is uneconomical and impractical for use in large wind turbines. This study proposes a single laser displacement sensor (LDS) system in which all of the rotating blades could be cost-effectively evaluated. Contrary to the approach of blade sensor installation, the LDS system is installed in the tower to enable noncontact blade displacement monitoring. The concept of a noncontact sensor and actuator and their energy delivery device installation in the tower will enable various approaches for wind turbine structural health monitoring. Blade bolt loosening causes deflection in the affected blade. Similarly, nacelle tilt or mass loss damage in the blade will result in changes in blade deflection, but the proposed system can identify such problems with ease. With the need of more energy, the sizes of wind blades are getting bigger and bigger. Due to the large size of wind turbine, nowadays wind turbines are installed very high above the ground or water level. It is impractical to monitor the results from LDS through wired connection in these cases. Hence, the wired connection of LDS to base (monitoring) station must be replaced by a wireless solution. This wireless solution is achieved using Zigbee technology. Zigbee operates in the industrial, scientific and medical (ISM) radio bands, typically 2.4 GHz, 915 MHz and 868 MHz. The output from the LDS is fed to the microcontroller which acts as an analog to digital converter. The output from the microcontroller is connected to the Zigbee transceiver module, which transmits the data and at the other end, the zigbee reads the data and displays on the PC from where user can monitor the condition of wind blades.
84
作者: Wieslaw Ostachowicz, Pawel Kudela, Maciej Radzienski
摘要: The goal of this paper is to develop a new method of filtering and processing of guided wavefield images acquired by the laser vibrometers. The concept is tested on both numerical results and experimental data obtained from measurements of aluminium alloy plate which notch cuts. Results were compared with RMS based maps for different excitation frequencies.
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