Showing papers on "Structural health monitoring published in 2003"
TL;DR: In this article, Niezrecki et al. summarized the hardware and software issues of impedance-based structural health modi- toring based on piezoelectric materials.
Abstract: In this paper we summarize the hardware and software issues of impedance-based structural health moni- toring based on piezoelectric materials. The basic concept of the method is to use high-frequency structural excitations to monitor the local area of a structure for changes in structural impedance that would indicate imminent damage. A brief overview of research work on experimental and theoretical stud- ies on various structures is considered and several research papers on these topics are cited. This paper concludes with a discussion of future research areas and path forward. Piezoelectric materials acting in the "direct" manner pro- duce an electrical charge when stressed mechanically. Con- versely, a mechanical strain is produced when an electrical field is applied. The direct piezoelectric effect has often been used in sensors such as piezoelectric accelerometers. With the converse effect, piezoelectric materials apply local- ized strains and directly influence the dynamic response of the structural elements when either embedded or surface bonded into a structure. Piezoelectric materials have been widely used in structural dynamics applications because they are lightweight, robust, inexpensive, and come in a variety of forms ranging from thin rectangular patches to complex shapes being used in microelectromechanical systems (MEMS) fabrications. The applications of piezoelectric mate- rials in structural dynamics are too numerous to mention and are detailed in the literature (Niezrecki et al., 2001; Chopra, 2002). The purpose of this paper is to explore the importance and effectiveness of impedance-based structural health mon- itoring from both hardware and software standpoints. Imped- ance-based structural health monitoring techniques have been developed as a promising tool for real-time structural dam- age assessment, and are considered as a new non-destructive evaluation (NDE) method. A key aspect of impedance-based structural health monitoring is the use of piezoceramic (PZT) materials as collocated sensors and actuators. The basis of this active sensing technology is the energy transfer between the actuator and its host mechanical system. It has been shown that the electrical impedance of the PZT material can be directly related to the mechanical impedance of a host structural component where the PZT patch is attached. Uti- lizing the same material for both actuation and sensing not only reduces the number of sensors and actuators, but also reduces the electrical wiring and associated hardware. Fur- thermore, the size and weight of the PZT patch are negligible compared to those of the host structures so that its attach- ment to the structure introduces no impact on dynamic char- acteristics of the structure. A typical deployment of a PZT on a structure being monitored is shown in Figure 1. The first part of this paper (Sections 2 and 3) deals with the theoretical background and design considerations of the impedance-based structural health monitoring. The signal processing of the impedance method is outlined in Section 4. In Section 5, experimental studies using the impedance approaches are summarized and related previous works are listed. Section 6 presents a brief comparison of the imped- ance method with other NDE approaches and, finally, sev- eral future issues are outlined in Section 7. 2. Theoretical Background
1,048 citations
TL;DR: In this paper, a fiber-optic system based on fiber Bragg grating sensors is proposed to detect ultrasonic Lamb waves in aircraft structures, in particular aircraft structural structures.
Abstract: This paper describes a fiber-optic system which is able to detect ultrasound in structures. The aim of the sensing system is to monitor structures, in particular aircraft structures, by detecting ultrasonic Lamb waves. This type of monitoring technique has recently become a key topic in structural health monitoring. Most common approaches use piezoceramic devices to launch and receive the ultrasound. A new way of fiber-optic detection of Lamb waves is based on fiber Bragg grating sensors. In addition to the well known advantages of fiber-optic sensors, this new interrogation scheme allows the use of Bragg gratings for both high-resolution strain and high-speed ultrasound detection. The focus of the paper is on the ultrasonic part of the system. The theoretical approach and the implementation into a laboratory set-up are elaborated. Experiments have been carried out to calibrate the system and first results on simple structures show the feasibility of the system for sensing ultrasonic Lamb waves.
280 citations
05 Aug 2003
TL;DR: In this article, the capability of embedded piezoelectric wafer active sensors (PWAS) to perform in-situ nondestructive evaluation (NDE) is explored.
Abstract: The capability of embedded piezoelectric wafer active sensors (PWAS) to perform in-situ nondestructive evaluation (NDE) is explored. Theoretical developments and laboratory tests are used to prove that PWAS transducers can satisfactorily perform Lamb wave transmission and reception, pulse-echo, pitch-catch, and phased array functions of conventional ultrasonics thus opening the road for embedded ultrasonics. Subsequently, crack detection in an aircraft panel with the pulse-echo method is illustrated. For large area scanning, a PWAS phased array is used to create the embedded ultrasonics structural radar (EUSR). For quality assurance, PWAS self-tests with the electromechanical impedance method are discussed.
254 citations
TL;DR: In this paper, the extrinsic Fabry-Perot interferometer (EFPI) and fiber Bragg grating (FBG) sensors are real-time employed to simultaneously monitor the cure process of CFRP composite laminates with and without damage.
Abstract: Structural health monitoring (SHM) including the real-time cure monitoring and non-destructive evaluation (NDE) in-service is very important and definitely demanded for safely working of high performance composite structures in situ. It is very difficult to carry out by using conventional methods. A unique opportunity was provided to real-time monitor the health status of composite structures by using embedded fiber optic sensors (FOSs). In this paper, the extrinsic Fabry–Perot interferometer (EFPI) and fiber Bragg grating (FBG) sensors are real-time employed to simultaneously monitoring the cure process of CFRP composite laminates with and without damage. The results show that both embedded EFPI and FBG sensors could be used to monitor the cure progress of composite materials and detect the occurred damage on-line during the fabrication of composite structures. Furthermore, the NDE of smart composite laminates embedded both EFPI and FBG sensors are performed by using the three-point bending test. The experimental results present that the flexural strain of CFRP composite laminates with damage is more than that of CFRP laminates without damage under same load as we expected. Both EFPI and FBG sensors also show the excellent correlation during the cure monitoring and bending test.
251 citations
TL;DR: In this paper, a structural health monitoring methodology for a wing box is presented. Butler et al. used novelty detection based on measured transmissibilities from the structure of the wing.
237 citations
TL;DR: In this paper, the local interaction simulation approach for Lamb wave propagation modelling in metallic structures is applied to analyze two-dimensional wave interactions with slot-type defects, and the results show the potential for complex modeling of acousto-ultrasonic waves in damage detection applications.
Abstract: Lamb waves have shown great potential for structural health monitoring The technique is based on guided ultrasonic waves introduced into a structure at one point and sensed at a different location Damage in a structure is identified by a change in the output signal However, previous studies show that even simple structural configurations can lead to complex response signals Therefore a knowledge and understanding of wave propagation can ease the interpretation of damage detection results This paper reports an application of the local interaction simulation approach for Lamb wave propagation modelling in metallic structures The focus of the analysis is on two-dimensional wave interactions with slot-type defects The method shows the potential for complex modelling of acousto-ultrasonic waves in damage detection applications
221 citations
TL;DR: In this article, structural health monitoring of the Z24 bridge in Switzerland was studied using the measurement data from three damage configurations, and the identification of the modal parameters from the response data was automated using stochastic subspace identification technique and the stabilisation diagram.
146 citations
TL;DR: In this paper, structural health monitoring should be similar to medical health monitoring of the body, in which life signs such as pulse and blood pressure give an overall indication of the overall health of the human body.
Abstract: Assessing the condition of a structure is necessary to determine its safety and reliability. Ideally, structural health monitoring should be similar to medical health monitoring of the body. In medical health monitoring, the life signs such as pulse and blood pressure give an overall indication of the overall health of the body. This is analogous to global structural health monitoring, in which damage to the structure can be identified by measuring changes in the global properties of the structure. Once the body signs show an anomaly, we do a battery of tests to determine the cause of the anomaly. Analogously in structural health monitoring, nondestructive evaluation (NDE) can be used to determine the nature of the damage. NDE methods to determine local damage are also becoming more accepted in practice. This paper describes some of the recent and current National Science Foundation projects in this area of research. Promising areas for NDE are identified.
141 citations
TL;DR: In this article, the second phase of an experimental validation program for a structural health monitoring methodology based on novelty detection is described, in which damage is introduced by making several copies of an inspection panel, each with a different controlled fault.
140 citations
TL;DR: An extension of the detection method for damage location is proposed and demonstrated and the method was demonstrated by determining which of a set of inspection panels had been removed from a Gnat aircraft wing.
140 citations
TL;DR: In this paper, a neural network-based approach for detecting structural damage is presented, which consists of two steps: system identification and structural damage detection, where the first step uses neural system identification networks (NSINs) to identify the undamaged and damaged states of a structural system.
TL;DR: In this article, a structural health monitoring module was implemented by coupling commercially available microelectro-mechanical system sensors and a wireless telemetry unit with damage detection firmware, which can detect damage to the joint.
Abstract: System integration of an online structural health monitoring module was accomplished by coupling commercially available microelectro-mechanical system sensors and a wireless telemetry unit with damage detection firmware. To showcase the capabilities of the integrated monitoring module, a bolted frame structure was constructed, and the preload in one of the bolted joints was controlled by a piezoelectric stack actuator to simulate gradual deterioration of a bolted connection. Two separate damage detection algorithms were used to classify a joint as damaged or undamaged. First, a statistical process control algorithm was used to monitor the correlation of vibration data from two accelerometers mounted across a joint. Changes in correlation were used to detect damage to the joint. For each joint, data were processed locally on a microprocessor integrated with the wireless module, and the diagnosis result was remotely transmitted to the base monitoring station. Second, a more sophisticated damage detection al...
TL;DR: To illustrate the computational capabilities of the proposed wireless sensing unit, the fast Fourier transform and auto- regressive time-series modeling are locally executed by the unit and suggest strong potential for unit installation in automated structural health monitoring systems.
Abstract: Complementing recent advances made in the field of structural health monitoring and damage detection, the concept of a wireless sensing network with distributed computational power is proposed. The fundamental building block of the proposed sensing network is a wireless sensing unit capable of acquiring measurement data, interrogating the data and transmitting the data in real time. The computational core of a prototype wireless sensing unit can potentially be utilized for execution of embedded engineering analyses such as damage detection and system identification. To illustrate the computational capabilities of the proposed wireless sensing unit, the fast Fourier transform and auto- regressive time-series modeling are locally executed by the unit. Fast Fourier transforms and auto- regressive models are two important techniques that have been previously used for the identification of damage in structural systems. Their embedment illustrates the computational capabilities of the prototype wireless sensing unit and suggests strong potential for unit installation in automated structural health monitoring systems.
TL;DR: This work explores the utility of attractor-based approaches in the field of vibration-based structural health monitoring by driving the structure directly with the output of a chaotic oscillator using the Kaplan-Yorke conjecture.
Abstract: This work explores the utility of attractor-based approaches in the field of vibration-based structural health monitoring The technique utilizes the unique properties of chaotic signals by driving the structure directly with the output of a chaotic oscillator Using the Kaplan-Yorke conjecture, the Lyapunov exponents of the driving signal may be tuned to the dominant eigenvalues of the structure, thus controlling the dimension of the structural response Data are collected at various stages of structural degradation and a simple nonlinear model, constructed from the undamaged data, is used to make predictions for the damaged response data Prediction error is then introduced as a "feature" for classifying the magnitude of the damage Results are presented for an experimental cantilevered beam instrumented with fiber-optic strain sensors
TL;DR: The purpose of structural health monitoring (SHM) is to lead a structure to be safer at lower cost as mentioned in this paper, and the purpose of SHM is to assess structural integrity during manufacture and in-service operation.
Abstract: The purpose of structural health monitoring (SHM) is to lead a structure to be safer at lower cost. SHM systems capable of assessing structural integrity during manufacture and in-service operation...
14 Oct 2003
TL;DR: In this article, the authors reviewed the fundamental electro-mechanical coupling between the structure and the PZT patch and introduced a new concept of 'active' signatures, whereby it is possible to utilize the direct interactive component of the signature for NDE afte filtering the 'inert' component.
Abstract: In recent years, the piezoelectric-ceramic (PZT) patches are increasingly been used as impedance transducers for non-destructive evaluation (NDE) of structures. In this application, the electrical admittance of a PZT patch surface bonded to the structure is utilized as a diagnostic signature of the structure. The operating frequency is typically maintained in the kHz range for optimum sensitivity in damage detection. The electro-mechanical interaction between the host structure and the bonded patch is key to the detection of damage in this NDE technique. Although the method is well established for a wide variety of structures and material types, very little research has focused on the fundamental structure-PZT interaction. This paper reviews the fundamental electro-mechanical coupling between the structure and the PZT patch and introduces a new concept of 'active' signatures, whereby it is possible to utilize the direct interactive component of the signature for NDE afte filtering the 'inert' component. Consequences of this concept, which include increased sensitivity to damage and reduced influence of temperature fluctuations on signatures are highlighted.
TL;DR: In this paper, two simple models of an articulated offshore structure are excited with the output of a stochastic process conforming to the ambient Pierson-Moskowitz wave distribution, which can successfully detect a stiffness degradation in model offshore structures.
Book Chapter•
01 Jul 2003
TL;DR: This paper introduces the second experimental phase of the activities of the IASC-ASCE Structural Health Monitoring Task Group, involving the application of structural health monitoring techniques to data obtained from a four story steel frame structure tested in August 2002 at the University of British Columbia.
Abstract: This paper introduces the second experimental phase of the activities of the IASC-ASCE Structural Health Monitoring Task Group, involving the application of structural health monitoring techniques to data obtained from a four story steel frame structure tested in August 2002 at the University of British Columbia. These Phase II experimental studies follow a series of analytical studies focusing on a model of the same structure. In the experiment, damage was simulated by removing bracing or loosening bolts within the structure. Three types of excitation were considered: electrodynamic shaker, impact hammer, and ambient vibration. In the shaker tests an electrodynamic shaker on the top floor of the frame was used to excite the structure. Accelerometers were placed throughout the structure to provide measurements of the structural responses. The data and a complete description of the experimental setup are also available at http://wusceel.cive.wustl.edu/asce.shm/ for potential participants to download and examine. Subsequent papers in this session will consider solution procedures for this problem.
TL;DR: In this article, the authors proposed a damage sensitive feature that takes advantage of the nonlinearities associated with discontinuities introduced into the dynamic response data as a result of certain types of damage.
Journal Article•
TL;DR: In this article, the magnetostrictive sensor technology is used for long range global testing and condition monitoring of structures such as piping, plates and steel cables, including the probe, instrument and data analysis software.
Abstract: A technical background on and applications of a guided wave technology called the magnetostrictive sensor are described. The magnetostrictive sensor technology is for long range global testing and condition monitoring of structures such as piping, plates and steel cables. For long range testing of piping in processing plants, such as refineries and chemical plants, the magnetostrictive sensor system, including the probe, instrument and data analysis software, is matured for use in commercial testing services. Capabilities of the present magnetostrictive sensor system for pipe testing are presented together with an example of testing data and their analysis.
TL;DR: In this article, the authors explored the role of steady-state dynamic analysis in the vibration-based structural health monitoring field and proposed a geometric portrait of system dynamics to extract information about the steady state response of the structure to sustained excitation.
Abstract: This work explores the role of steady-state dynamic analysis in the vibration-based structural health monitoring field. While more traditional approaches focus on transient or stochastic vibration analysis, the method described here utilizes a geometric portrait of system dynamics to extract information about the steady-state response of the structure to sustained excitation. The approach utilizes the fundamental properties of chaotic signals to produce low-dimensional response data which are then analyzed for features which indicate the degree to which the dynamics have been altered by damage. A discussion of the fundamental issues involved in the approach is presented along with experimental evidence of the approach's ability to discriminate among several damage scenarios.
TL;DR: In this paper, an attractor-based feature derived from the field of nonlinear time-series analysis is presented to quantify damage induced changes to the structure in the presence of ambient variation, that is, changes in ambient temperature, varying moisture levels, etc.
Abstract: The field of vibration based structural health monitoring involves extracting a ‘feature’ which robustly quantifies damage induced changes to the structure in the presence of ambient variation, that is, changes in ambient temperature, varying moisture levels, etc In this paper, we present an attractor-based feature derived from the field of nonlinear time-series analysis Emphasis is placed on the use of chaos for the purposes of system interrogation The structure is excited with the output of a chaotic oscillator providing a deterministic (low-dimensional) input Use is made of the Kaplan–Yorke conjecture in order to ‘tune’ the Lyapunov exponents of the driving signal so that varying degrees of damage in the structure will alter the state space properties of the response attractor The average local attractor variance ratio (ALAVR) is suggested as one possible means of quantifying the state space changes Finite element results are presented for a thin aluminum cantilever beam subject to increasing damage, as specified by weld line separation, at the clamped end Comparisons of the ALAVR to two modal features are evaluated through the use of a performance metric
Patent•
16 Jun 2003
TL;DR: In this article, a method and device for performing ultrasonic damage detection in a thin-wall structure using an array of embedded Piezoelectric Wafer Active Sensors (PWAS) for the transmission and reception of guided waves and a signal processing methodology based on the beamforming process is presented.
Abstract: A method and device for performing ultrasonic damage detection in a thin-wall structure using an array of embedded Piezoelectric Wafer Active Sensors (PWAS) for the transmission and reception of guided waves and a signal processing methodology based on the beamforming process. The beamforming signal processing has been adapted to the specifics of guided elastic waves traveling in thin-wall structures.
TL;DR: In this article, the use of the chirp vibration responses of an aircraft wing tip was investigated to detect, locate and approximately quantify damage. And the results obtained from the testing led to the concept of a sensor tape to detect damage at joints in an aircraft structure.
04 Aug 2003
TL;DR: In this paper, the applicability of the time-reversal concept to guided waves in plates, where the waves are dispersive and of multi-modes, has been investigated, and it is shown that although temmporal and spatial focusing can be achieved through time reversal, the dispersive behavior of the flexural waves renders it impossible to exactly reconstruct the waveform of the original excitation.
Abstract: In this paper an experimental and theoretical investigation of the applicability of the time-reversal concept to guided waves in plates, where the waves are dispersive and of multi-modes. It is shown that although temmporal and spatial focusing can be achieved through time reversal, the dispersive behavior of the flexural waves renders it impossible to exactly reconstruct the waveform of the original excitation. Nevertheless, the temporal and spatial focusing allows the development of a synthetic time-reversal array method for a distributed network of sensors and actuators. This new method, which overcomes the limitation of the conventional phased array method that operates under pulse-echo mode, can considerably enhance the signal strength, thus reducing the number of sensors and actuators required to achieve a given signal-to-noise ratio.
TL;DR: In this article, the current status of research and application activities on structural health monitoring (SHM) systems for civil infra-structures in Korea are briefly introduced by 4 parts: (1) current status on bridge monitoring systems on existing and newly constructed bridges, (2) research and development activities on smart sensors such as optical fiber sensors and piezo-electric sensors, (3) structural damage detection methods using measured data, and (4) a test road project for verification and enhancement of the pavement design procedures by Korea Highway Corporation.
Abstract: Developments and applications of structural health monitoring (SHM) systems have become active particularily for long-span bridges in Korea. They are composed of sensors, data acquisition system, data transmission system, information processing, damage assessment, and information management. In this paper, current status of research and application activities on SHM systems for civil infra-structures in Korea are briefly introduced by 4 parts: (1) current status of bridge monitoring systems on existing and newly constructed bridges, (2) research and development activities on smart sensors such as optical fiber sensors and piezo-electric sensors, (3) structural damage detection methods using measured data, and (4) a test road project for verification and enhancement of the pavement design procedures by the Korea Highway Corporation. Finally the R&D activities of a newly established Smart Infra-Structure Technology Center at Korea Advanced Institute of Science and Technology are also briefly described.
01 Mar 2003
TL;DR: In this article, a finite element (FE) model of a large suspension steel bridge for fatigue stress analysis is presented, and the verification of the model is carried out with the help of the measured bridge modal characteristics and the online data measured by the structural health monitoring system installed on the bridge.
Abstract: Fatigue is an important failure mode for large suspension bridges under traffic loadings However, large suspension bridges have so many attributes that it is difficult to analyze their fatigue damage using experimental measurement methods Numerical simulation is a feasible method of studying such fatigue damage In British standards, the finite element method is recommended as a rigorous method for steel bridge fatigue analysis This paper aims at developing a finite element (FE) model of a large suspension steel bridge for fatigue stress analysis As a case study, a FE model of the Tsing Ma Bridge is presented The verification of the model is carried out with the help of the measured bridge modal characteristics and the online data measured by the structural health monitoring system installed on the bridge The results show that the constructed FE model is efficient for bridge dynamic analysis Global structural analyses using the developed FE model are presented to determine the components of the nominal stress generated by railway loadings and some typical highway loadings The critical locations in the bridge main span are also identified with the numerical results of the global FE stress analysis Local stress analysis of a typical weld connection is carried out to obtain the hot-spot stresses in the region These results provide a basis for evaluating fatigue damage and predicting the remaining life of the bridge
TL;DR: In this paper, a finite element (FE) model of a large suspension steel bridge for fatigue stress analysis is presented, and the verification of the model is carried out with the help of the measured bridge modal characteristics and the online data measured by the structural health monitoring system installed on the bridge.
18 Aug 2003
TL;DR: The Smart Pebble as mentioned in this paper is a wireless sensor for monitoring the level of chloride ingress into concrete bridge decks, which can be queried remotely both to identify it and to indicate chloride concentration levels.
Abstract: SRI International is developing a wireless sensor for monitoring the level of chloride ingress into concrete bridge decks. We call this device a Smart Pebble since it has roughly the size and weight of a typical piece of the rock aggregate that is used in such structures. It is "smart" in that it contains a chloride sensor and a radio-frequency identification (RFID) chip that can be queried remotely both to identify it and to indicate chloride concentration levels. The Smart Pebble is also powered remotely, thus precluding the need for any lifetime-limiting batteries. It is designed to be inserted in the bridge deck either during the initial construction (or during refurbishment) or in a back-filled core hole. This paper will discuss the Smart Pebble design, operation, and status.
31 Jul 2003
TL;DR: In this paper, an instrumented impact testing system is used to record the contact force and the surface motion at locations away from the impact point, and the response of the plate due to localized sources is calculated using a modified laminate theory providing detailed information on the relationship between the impact load and the signals generated by the load.
Abstract: Hidden damage caused by foreign object impact in a composite structure, if left undetected, can grow and lead to a catastrophic failure of the structure. Detection of impact events and characterization of the degree of damage caused by them, preferably in real time, would be extremely helpful in safe continued operation of composite structures. In this paper, low velocity impact experiments are carried out on AS4/3501-6 [0/90]8S cross-ply graphite epoxy composite plates. An instrumented impact testing system is used to record the contact force and the surface motion at locations away from the impact point. The response of the plate due to localized sources is calculated using a modified laminate theory providing detailed information on the relationship between the impact load and the signals generated by the load. For thin plates, the far-field response is dominated by plate guided Lamb waves. It is shown that the occurrence of an impact loading can be easily detected from the recorded signals. Delamination damage, if any, can also be determined through careful analysis of the recorded waveforms. Practical applications of the technique in structural health monitoring will require careful investigation and elimination of environmental noise.