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ErratumEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
(Source: Structural Health Monitoring)
Source: Structural Health Monitoring - October 13, 2009 Category: Medical Equipment Tags: Articles Source Type: journals

Experimental Investigation on Statistical Moment-based Structural Damage Detection MethodEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Although vibration-based structural damage detection methods have demonstrated various degrees of success, the damage detection of civil structures still remains as a challenging task. The main obstacles include the insensitivity to local damage and the high sensitivity to measurement noise. A new structural damage detection method based on the statistical moments of dynamic responses of a structure has been recently proposed by the authors, and the numerical study manifested that the proposed method is sensitive to local structural damage but insensitive to measurement noise. The experimental investigation on this method ...
Source: Structural Health Monitoring - October 13, 2009 Category: Medical Equipment Authors: Xu, Y.L., Zhang, J., Li, J.C., Xia, Y. Tags: Articles Source Type: journals

Structural Health Monitoring of a Metallic Sandwich Panel by the Method of Virtual ForcesEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
A structural health monitoring system for assessing thermal damage in a metallic sandwich panel was developed in this article. The method of virtual forces was utilized to detect, locate, and quantify damage. The method assumes that a damaged structural response is a summation of the undamaged response and the response from an effective forcing function, which represents the effects of the material damage. The effective forcing function, or virtual force, is an estimate of the forces that the damage mechanism exerts on the undamaged structure. Virtual forces were shown to detect changes in the mass, stiffness, and damping ...
Source: Structural Health Monitoring - October 13, 2009 Category: Medical Equipment Authors: White, J. R., Adams, D. E., Jata, K. Tags: Articles Source Type: journals

Correlating Low-energy Impact Damage with Changes in Modal Parameters: A Preliminary Study on Composite BeamsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
This article is an experimental study of the effects of multi-site damage on the vibration response of a composite beam damaged by low-energy impact. The variation of the modal parameters with different levels of impact energy and density of impact is studied. Specimens are impacted symmetrically in order to induce a global rate of damage. A damage detection tool Damage Index is introduced in order to verify the estimation of damping ratios. Design of Experiments is used to establish the sensitivity of both energy of impact and density of damage. The DOE analysis results (using natural frequency only) indicate that impact ...
Source: Structural Health Monitoring - October 13, 2009 Category: Medical Equipment Authors: Shahdin, A., Morlier, J., Gourinat, Y. Tags: Articles Source Type: journals

Development of a Real-time Remote Structural Monitoring Scheme for Civil Infrastructural SystemsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
This article describes the development of an RSM scheme, developed at SERC, Chennai. The article outlines the laboratory and field investigations carried out to validate the developed scheme. Brief information about the observations and modifications made during these trials are also presented. A part of the work carried out for synthesizing online data using Auto Regressive Moving Average model is also presented. (Source: Structural Health Monitoring)
Source: Structural Health Monitoring - October 13, 2009 Category: Medical Equipment Authors: Sridhar, S., Ravisankar, K., Sreeshylam, P., Parivallal, S., Kesavan, K., Murthy, S.G.N. Tags: Articles Source Type: journals

Onset of Resin Micro-cracks in Unidirectional Glass Fiber Laminates with Integrated SHM Sensors: Numerical AnalysisEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
This article presents the efforts to estimate the effects of these stress/strain concentrations induced by the integration of rectangular-shape sensors within unidirectional fiber-glass composites. The micro-crack initiation sites and the failure load are predicted using finite-element simulations. Good agreement has been found between the numerical results and the experimental findings presented in an accompanying paper. (Source: Structural Health Monitoring)
Source: Structural Health Monitoring - October 13, 2009 Category: Medical Equipment Authors: Huang, Y., Ghezzo, F., Nemat-Nasser, S. Tags: Articles Source Type: journals

Onset of Resin Micro-Cracks in Unidirectional Glass Fiber Laminates with Integrated SHM Sensors: Experimental ResultsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
This article presents the results of experiments conducted in order to identify and locate the failure initiation in glass fiber/epoxy laminates with integrated structural health monitoring sensors (SHM) and electronics. Recent advances in health monitoring technologies have resulted in the development of micro-dimensional devices that can be embedded into composite laminates. Notwithstanding their small size, such inclusions may affect the response of the composite. Damage induced by the peak values of stress concentration around the embedded inclusion is, in fact, one of the main concerns in smart structures technology. ...
Source: Structural Health Monitoring - October 13, 2009 Category: Medical Equipment Authors: Ghezzo, F., Huang, Y., Nemat-Nasser, S. Tags: Articles Source Type: journals

Time Domain Reflectometry Automatic Bridge Scour Measurement System: Principles and PotentialsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
This study introduces the development of an automatic scour monitoring system using time domain reflectometry (TDR) principle. It presents the principles and system design of the TDR sediment scour monitoring system. An analyses algorithm for scour signals has been developed. It was found to be robust and can be implemented to automate scour signal interpretation. Simulated experiments were conducted to validate the performance of the scour monitoring system prototype. The results showed that this TDR technology can accurately measure the scour depth. Besides, the properties of the sediments, such as the porosity and densi...
Source: Structural Health Monitoring - October 13, 2009 Category: Medical Equipment Authors: Yu, X., Yu, X. Tags: Articles Source Type: journals

Assessment of Vibration-based Damage Identification Methods Using Displacement and Distributed Strain MeasurementsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
This article, through computer simulation and experimental investigation of a simply supported beam, comparatively evaluates the performance of these techniques for practical civil SHM by using displacement modes from accelerometers and long-gage distributed strain measurements. Most of all the techniques proved unreliable for damage identification using noisy measurements from accelerometers, while successful with distributed strain measurements. The findings reveal that long-gage distributed strain measurements are much more efficient choice over the traditional measurement techniques for reliable civil SHM. It may there...
Source: Structural Health Monitoring - October 13, 2009 Category: Medical Equipment Authors: Philips Adewuyi, A., Wu, Z., Kammrujaman Serker, N.H.M. Tags: Articles Source Type: journals

Three-point Frequency Tracking MethodEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
This paper presents and evaluates in detail a harmonics tracking method (HTM) for tracking the instantaneous frequency and amplitude of a vibration signal by processing only three most recent data points. Teager—Kaiser algorithm (TKA) is a popular four-point method for online frequency tracking, but its accuracy is easily destroyed by measurement noise due to the use of finite difference. Moreover, because a signal is assumed to be a pure harmonic in TKA, any moving average in the signal can destroy the accuracy of TKA. On the other hand, HTM uses a constant and a pair of harmonics to fit three recent data points and...
Source: Structural Health Monitoring - October 13, 2009 Category: Medical Equipment Authors: Pai, P. F. Tags: Articles Source Type: journals

Sensitivity Enhancement of Long-gage FBG Sensors for Macro-strain MeasurementsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In our recent study, a structural health monitoring strategy based on distributed fiber optic sensing techniques has been proposed to utilize the strain responses throughout the full or some partial areas of structures to detect the arbitrary and unforeseen damage. However, to perform this strategy more effectively, there is an increasing demand for improving the ability of such sensors to measure small structural responses, especially for the cases such as damage identification based on ambient vibration tests, fatigue crack monitoring of steel structures and crack detection of reinforced concrete structures. This work pu...
Source: Structural Health Monitoring - October 13, 2009 Category: Medical Equipment Authors: Suzhen Li, , Zhishen Wu, Tags: Articles Source Type: journals

Numerical and Experimental Studies of a Substructural Identification StrategyEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
For structural health monitoring it is impractical to identify a large structure with complete measurement due to limited number of sensors and difficulty in field instrumentation. Furthermore, it is not desirable to identify a large number of unknown parameters in a full system because of numerical difficulty in convergence. A novel substructural strategy was presented for identification of stiffness matrices and damage assessment with incomplete measurement. The substructural approach was employed to identify large systems in a divide-and-conquer manner. In addition, the concept of model condensation was invoked to avoid...
Source: Structural Health Monitoring - August 26, 2009 Category: Medical Equipment Authors: Tee, K.F., Koh, C.G., Quek, S.T. Tags: Article Source Type: journals

Potential and Limitations of a Deconvolution Approach for Guided Wave Structural Health MonitoringEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Ultrasonic guided waves offer the possibility of inspecting large areas of structures from a small number of sensor positions. However, inspection of complex structures is difficult as the reflections from different features overlap. Estimating the number and amplitude of the wave packets in ultrasonic time traces is crucial for the development of a guided wave inspection system, in order to detect and locate damage. Deconvolution has been extensively used in geophysical applications to resolve overlapping echoes in the recorded signals. The main objective of this work was to evaluate the applicability of the deconvolution...
Source: Structural Health Monitoring - August 26, 2009 Category: Medical Equipment Authors: Cicero, T., Cawley, P., Simonetti, F., Rokhlin, S.I. Tags: Article Source Type: journals

Mesh-free Modeling of Ultrasonic Wave Fields in Damaged Layered Half-spacesEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Modeling of an ultrasonic wave field inside a layered half-space is carried out by using the mesh-free semi-analytical Distributed Point Source Method (DPSM). The complete field is computed in a layered half-space in presence and absence of defects. The layered structure is excited by a bounded ultrasonic beam generated by a finite-sized transducer. It is important to have theoretical models to predict the ultrasonic fields in damaged and damage-free structures for its nondestructive evaluation. Numerical exercises can be carried out aided by these theoretical models to determine the area of the most distorted ultrasonic f...
Source: Structural Health Monitoring - August 26, 2009 Category: Medical Equipment Authors: Das, S., Kundu, T. Tags: Article Source Type: journals

Passive Impact Location Estimation Using Piezoelectric SensorsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
As part of Structural Health Monitoring (SHM), the history of a structure has become a crucial element to take into account. This has been shown, for example, by the spectacular accident of the flight Aloha 243 near Hawaï, when a whole part of the fuselage of a Boeing 737 had been torn off. Thus, monitoring impacts has become particularly interesting to give a comprehensive view of the occurrence of structural damage. Typical impact location estimation techniques use structural frequency drifts of a structure. Thus, such methods need an external excitation of the structure, which is unrealistic in most of the cases. A...
Source: Structural Health Monitoring - August 26, 2009 Category: Medical Equipment Authors: Guyomar, D., Lallart, M., Monnier, T., Xingjun Wang, , Petit, L. Tags: Article Source Type: journals

Damage Detection of Shear Connectors in Composite BridgesEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Headed shear studs are commonly used to resist longitudinal shear forces in composite railway bridges. Due to the growth of traffic and increase in train speed, these studs are subjected to high-cycle fatigue loading which may lead to damage, thus affecting the integrity between the steel girder and the concrete slab. Therefore, it is necessary to find a corresponding nondestructive damage detection method. Within the frame of this paper, the occurrence of damage in shear studs is studied by numerical analysis. In the numerical model of a real composite bridge, headed shear studs are represented by spring elements. A damag...
Source: Structural Health Monitoring - August 26, 2009 Category: Medical Equipment Authors: Liu, K., De Roeck, G. Tags: Article Source Type: journals

An Oil Condition Monitoring Technique to Determine the Optimal Oil Type and Maintenance ScheduleEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Oil analysis is the main condition monitoring technique for reciprocating machinery maintenance and fault diagnosis. The object of this research was to choose and to investigate the best oil for Dump Truck HD325-5, used for transportation of minerals, by oil condition monitoring. This was achieved by analysing different oil samples after use in Dump Truck HD325-5. The oil analyses were initially carried out at regular intervals during life. A series of tests were then conducted during the operating hours of the machine. Oil samples were regularly collected. Numerical data produced by oil analyses were compared with those f...
Source: Structural Health Monitoring - June 18, 2009 Category: Medical Equipment Authors: Ahmadi, H., Mollazade, K. Tags: Article Source Type: journals

Near-field Sub-band Beamforming for Damage Detection in BridgesEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Traditional structural health monitoring techniques based on the vibration response of bridge structures are limited because of several factors — including a poorly formed aggregate system model, very low SNR, and unrealistic boundary conditions. Many times, these methods rely on global parameters to describe the dynamic behavior of local structural elements. In this paper, we proposed a novel efficient SHM technique that employs the use of compactly supported sub-band space/ frequency and time/frequency analysis using local vibration characteristics. To overcome the problem of the low-error sensitivity of features e...
Source: Structural Health Monitoring - June 18, 2009 Category: Medical Equipment Authors: Medda, A., DeBrunner, V. Tags: Article Source Type: journals

Robust Damage Metric in Terms of Magnitude and Phase for Impedance-based Structural Health MonitoringEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Structural health monitoring has been a research interest for its great potential for life safety and economic benefits for decades. Structural vibration impedance by way of piezoceramic patch excitation and sensoring offers a local damage detection technique and has caused a wide research interest. The commonly used damage index in this method is the rate of change of the real part of the measured electromechanical impedance. This paper studied several damage indices constructed by the real and imaginary parts or magnitude and phase. It theoretically deducted and concluded that the damage index in terms of changes in real...
Source: Structural Health Monitoring - June 18, 2009 Category: Medical Equipment Authors: Xianhua Liu, , Paurobally, R. Tags: Article Source Type: journals

An Investigation on Vibration-based Damage Detection in Circular PlatesEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
This study aimed at the development of vibration-based health monitoring methodology for thin circular plates. The possibility of using the first several natural frequencies of a circular plate for damage detection purposes was investigated first. The study then suggested a damage detection method, which considered a vibrating plate as a dynamic system and used its time-domain response represented in a new phase (state) space to extract damage sensitive characteristics. The paper introduced the idea of using large amplitude vibrations and nonlinear time series analysis for damage detection purposes. The suggested damage de...
Source: Structural Health Monitoring - June 18, 2009 Category: Medical Equipment Authors: Trendafoilova, I., Gorman, D.G., Manoach, E. Tags: Article Source Type: journals

Lead-free Piezoelectric KNN-based Pin Transducers for Structural Monitoring ApplicationsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
A 2.4 mm diameter piezoelectric ceramic disc was used to construct a spring-loaded pin-type transducer for intelligent monitoring of systems. Two types of lead-free KNN-based ceramics (0.95K0.5Na0.5 (Nb0.94Sb0.06)O 3 — 0.05LiTaO3 + 1.25 mol% BaO and K0.5Na 0.5NbO3 -0.75 mol% K5.4Cu1.3Ta 10O29) were selected as a sensing element of the pin. The piezoelectric spring-loaded pins were mounted on the corners of the aluminum plate for the performance evaluation using a laser ultrasonic technique. The signals detected by transducers with different sensing elements including lead-based ceramics have been compared. The capabi...
Source: Structural Health Monitoring - June 18, 2009 Category: Medical Equipment Authors: Lam, K.H., Lin, D.M., Ni, Y.Q., Chan, H.L.W. Tags: Article Source Type: journals

Structural Damage Detection Using Modal Curvature and Fuzzy LogicEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
A fuzzy logic system (FLS) with a new sliding window defuzzifier is proposed for structural damage detection using modal curvatures. Changes in the modal curvatures due to damage are fuzzified using Gaussian fuzzy sets and mapped to damage location and size using the FLS. The first four modal vectors obtained from finite element simulations of a cantilever beam are used for identifying the location and size of damage. Parametric studies show that modal curvatures can be used to accurately locate the damage; however, quantifying the size of damage is difficult. Tests with noisy simulated data show that the method detects da...
Source: Structural Health Monitoring - June 18, 2009 Category: Medical Equipment Authors: Chandrashekhar, M., Ganguli, R. Tags: Article Source Type: journals

A Nonlinear Acoustic Technique for Crack Detection in Metallic StructuresEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
A crack detection technique based on nonlinear acoustics is investigated in this study. Acoustic waves at a chosen frequency are generated using an actuating lead zirconate titanate (PZT) transducer, and they travel through the target structure before being received by a sensing PZT wafer. Unlike an undamaged medium, a cracked medium exhibits high acoustic nonlinearity which is manifested as harmonics in the power spectrum of the received signal. Experimental results also indicate that the harmonic components increase nonlinearly in magnitude with increasing amplitude of the input signal. The proposed technique identifies ...
Source: Structural Health Monitoring - April 14, 2009 Category: Medical Equipment Authors: Dutta, D., Sohn, H., Harries, K. A., Rizzo, P. Tags: Article Source Type: journals

Vertical Displacement Measurements for Bridges Using Optical Fiber Sensors and CCD Cameras -- A Preliminary StudyEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Bridge managers all over the world are always looking for simple ways to measure bridge vertical displacements for structural health monitoring. However, traditional methods to obtain such data are either tedious or expensive. There is a need to develop a simple, inexpensive, and yet practical method to measure bridge vertical displacements. This paper proposes two methods using either optical fiber (FBG) sensors or a charge-coupled-device (CCD) camera, respectively, for vertical displacement measurements of bridges. The FBG sensor method is based on the measured horizontal strains together with the identified curvature fu...
Source: Structural Health Monitoring - April 14, 2009 Category: Medical Equipment Authors: Chan, T. H. T., Ashebo, D. B., Tam, H.Y., Yu, Y., Chan, T.F., Lee, P.C., Perez Gracia, E. Tags: Article Source Type: journals

On Selection of Data Fusion Schemes for Structural Damage EvaluationEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Conclusions drawn from this study have given an indication on how to select a better, if not the most optimal, data fusion scheme for structural damage evaluation. (Source: Structural Health Monitoring)
Source: Structural Health Monitoring - April 14, 2009 Category: Medical Equipment Authors: Zhongqing Su, , Xiaoming Wang, , Li Cheng, , Long Yu, , Zhiping Chen, Tags: Article Source Type: journals

Localized Damage Detection of Structures Subject to Multiple Ambient Excitations Using Two Distance Measures for Autoregressive ModelsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In this paper, the distance measures of autoregressive (AR) models are used as damage indicators. Two distance measures are discussed: one is the Itakura distance, and the other is the cepstral distance. The distance measures of AR model have been successfully applied in image, speech, and neurological signal processing applications. This research explores new applications of two distance measures for damage detection in civil engineering. A five-storey building model is used for performance verification. Verification simulations show efficiencies of both distance-based damage indicators when the excitations are mutually u...
Source: Structural Health Monitoring - April 14, 2009 Category: Medical Equipment Authors: Haitao Zheng, , Mita, A. Tags: Article Source Type: journals

Wireless Sensor Networks for Strain Monitoring during Steel Bridges LaunchingEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In this paper, an experimental test performed on a hybrid steel plate girder was subjected to concentrated loads at the end of an unstiffened panel is presented. This load was intended to produce a typical reaction of the piers while launching steel girders in bridges. In this test, strain measurements were taken with conventional pre-wired gauges as well as with newly developed wirelessly connected strain-measuring system. Both measurements were carefully compared and the accuracy of the developed system was demonstrated. Results were also compared with numerical simulations deployed with FE models and on such a basis; th...
Source: Structural Health Monitoring - April 14, 2009 Category: Medical Equipment Authors: Chacon, R., Guzman, F., Mirambell, E., Real, E., Onate, E. Tags: Article Source Type: journals

AE Monitoring for Damage Assessment of RC Exterior Beam-column Subassemblages Subjected to Cyclic LoadingEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
This paper ascertains that Acoustic Emission (AE) monitoring is very effective for assessing the damage of reinforced concrete wide beam-column connections subjected to earthquake-type loadings. A cyclic test is conducted on an exterior connection until its failure. The experimental results show a strong correlation between the hysteretic strain energy and the AE energy histories. For this reason, a tentative formula is proposed, to predict the level of damage and the closeness to failure of the connection on the basis of the AE recorded by one piezoelectric sensor located near the critical zone (i.e., the beam-end and bea...
Source: Structural Health Monitoring - March 11, 2009 Category: Medical Equipment Authors: Benavent-Climent, A., Castro, E., Gallego, A. Tags: Article Source Type: journals

Structural Health Monitoring of Rods Based on Natural Frequency and Antiresonant Frequency MeasurementsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In this paper it is shown that natural frequency and antiresonant frequency shifts induced by a structural damage in an axially vibrating rod contain information on certain generalized Fourier coefficients of the stiffness variation caused by the degradation. This property is used to define a reconstruction procedure based on iterative updating of the undamaged configuration. The results of numerical simulations on rods with localized or diffuse damages are in good agreement with the theory, provided that average frequency and antiresonant frequency shifts due to degradation are bigger than the shifts due to modeling/measu...
Source: Structural Health Monitoring - March 11, 2009 Category: Medical Equipment Authors: Dilena, M., Morassi, A. Tags: Article Source Type: journals

A Monolithic Interdigitated PVDF Transducer for Lamb Wave InspectionEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
A monolithic interdigitated PVDF transducer (PVDF IDT) was built in this study. This PVDF IDT is capable of generating and receiving Lamb waves for structural health monitoring. Unlike most existing laminate-structured interdigitated PVDF transducers, this PVDF IDT features a monolithic structure, which eliminates sensor delamination as a potential problem. The flexible nature of PVDF promises the ability for the sensor to be attached to different structural surfaces. Other advantages of this PVDF IDT include low unit cost, easy installation, low power consumption, and the ability for wireless operation or remote interroga...
Source: Structural Health Monitoring - March 11, 2009 Category: Medical Equipment Authors: Hua Gu, , Wang, M. L. Tags: Article Source Type: journals

Structural Damage Detection Using Time Domain Periodogram AnalysisEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Before the advent of computers, scientists used time domain periodogram analysis (TDPA) for analysis of phenomena described by time-dependent parameters. Famous examples of this approach include investigations of periodicities in Sun activity, analysis of annual rings of trees and deposits of clays in large lakes, both of which are indicators of climate variations. These periodicities found by TDPA were later confirmed using modern Fourier transform-based methods. Since the advent of the computer era and the fast Fourier transform, TDPA has been almost completely abandoned. In this work, we develop a computer-based TDPA al...
Source: Structural Health Monitoring - March 11, 2009 Category: Medical Equipment Authors: Zimin, V.D., Zimmerman, D.C. Tags: Article Source Type: journals

Performance Evaluation and Reliable Implementation of Data Transmission for Wireless Sensors on Rotating Mechanical StructuresEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
This study is devoted to characterizing such performance of wireless sensors on a rotating lathe spindle and further examining the efficacy of a commonly adopted automatic repeat request (ARQ)-based reliable transmission method. The experimental measurements have shown that the transmission error rates were proportional to rotation speeds at certain receiver locations, while a minor change in the receiver location could significantly alter such dependency. It was found that the ARQ approach effectively assured a reliable data transmission during rotation with little retransmission overheads, and the reliable transmission t...
Source: Structural Health Monitoring - March 11, 2009 Category: Medical Equipment Authors: Lei Tang, , Wang, K.-C., Yong Huang, Tags: Article Source Type: journals

Structural Damage Detection Using Auxiliary Particle Filtering MethodEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Structural damage identification is an important objective of health monitoring for civil infrastructures. Frequently, damage to a structure may be reflected by a change of some system parameters, such as a degradation of the stiffness. In this paper, an auxiliary particle filtering (APF) method is applied to track a dynamic system with sudden parameter changes. In the APF, the importance density is proposed as a mixture density that depends upon the past state and the most recent observations, and hence which has a good time-tracking ability that is more suitable for tracking the nonstationary system than the conventional...
Source: Structural Health Monitoring - March 11, 2009 Category: Medical Equipment Authors: Songtao Xue, , Hesheng Tang, , Qiang Xie, Tags: Article Source Type: journals

An Algorithm for Simultaneous Optimization of Parameters of Condition-based Preventive MaintenanceEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
A new condition-based preventive maintenance model for a system, subject to deterioration-failures and to random failures with increasing intensity, is presented. Deterioration is modeled as discrete stages. After an inspection, based on the degree of deterioration, a minimal maintenance or a major maintenance is performed, or no action is taken. Deterioration failures are restored by complete replacements; Random failures are restored by minimal repair. Major maintenance restores the system to `' deterioration stages younger ( > 1), while minimal maintenance restores the system one stage. The proposed model considers a...
Source: Structural Health Monitoring - January 16, 2009 Category: Medical Equipment Authors: Naga Srinivasa Rao, P., Achutha Naikan, V.N. Tags: Article Source Type: journals

Sensor Self-diagnosis Using a Modified Impedance Model for Active Sensing-based Structural Health MonitoringEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The active sensing methods using piezoelectric materials have been extensively investigated for the efficient use in structural health monitoring (SHM) applications. Relying on high frequency structural excitations, the methods showed the extreme sensitivity to minor defects in a structure. Recently, a sensor self-diagnostic procedure that performs in situ monitoring of the operational status of piezoelectric (PZT) active sensors and actuators in SHM applications has been proposed. In this investigation, previously developed impedance models were revisited in order to investigate the effects of sensor and/or bonding defect...
Source: Structural Health Monitoring - January 16, 2009 Category: Medical Equipment Authors: Park, S., Park, G., Yun, C.-B., Farrar, C. R. Tags: Article Source Type: journals

Feature Selection for Robust Classification of Crack and Drop SignalsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
This paper presents a study to the problem of features selection for accurate recognition of crack signals in raining conditions, using a multilayer perceptron and a radial basis function neural network. The features extraction process is accomplished for two time frames: in the first time frame the presence of the signal reflection is minimal; in the later a wider window include signal reflections at the specimen edges. An extensive set of 90 features (41 of them are novel), 67 in the time domain and 23 in the frequency domain, are extracted from the normalized signals and are sorted according to Fisher ratio (F-ratio). T...
Source: Structural Health Monitoring - January 16, 2009 Category: Medical Equipment Authors: Kappatos, V., Dermatas, E. Tags: Article Source Type: journals

Long-term Structural Health Monitoring of a Multi-girder Steel Composite Bridge Using Strain DataEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
This paper presents an approach to use strain data from a multi-girder, composite steel bridge for long-term Structural Health Monitoring (SHM). The bridge being studied is part of a research project at the University of Connecticut in which long-term SHM systems are being installed on a series of bridges throughout the State of Connecticut. Strain data is collected from normal truck traffic to determine live load stresses, load distribution factors, and the location of the neutral axis in each girder. Known weight trucks were used along with a finite element analysis for verification of the behavior. The long-term monitor...
Source: Structural Health Monitoring - January 16, 2009 Category: Medical Equipment Authors: Cardini, A.J., DeWolf, J.T. Tags: Article Source Type: journals

Health Monitoring of a Thermal Protection System using Lamb WavesEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The applicability of guided waves as a structural health monitoring (SHM) tool to predict the point of impact and detect delamination in a thermal protection system (TPS) is studied. A model TPS was designed by bonding ceramic porous tiles to a 2.2 mm thick 2124-T351 aluminum alloy plate. The delamination defect may be caused by the impact phenomenon or due to other reasons such as manufacturing defect, thermal, or mechanical fatigue, etc. Impact phenomenon is simulated by dropping a ping pong ball on the tiled structure. The delamination at the interface between the ceramic tile and the aluminum plate is simulated by remo...
Source: Structural Health Monitoring - January 16, 2009 Category: Medical Equipment Authors: Kundu, T., Das, S., Jata, K. V. Tags: Article Source Type: journals

Modeling and Simulation of Normal and Damage Vibration Signatures of Idealized GearsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
A physics-based first principles approach is adopted in this study to simulate vibration signatures from an idealized gear such as a thin spur gear under plane dynamic stresses induced by an impulsive rotation. The governing equations of velocity—stress are solved using a finite-difference formulation in generalized curvilinear coordinates and a fully characteristic set of boundary conditions based on the theory of hyperbolic systems. The vibration signatures are thus directly obtained in the time domain. A second-order accurate in time and space, time-staggered leapfrog scheme, is used to integrate the time-dependen...
Source: Structural Health Monitoring - January 16, 2009 Category: Medical Equipment Authors: Kaul, U. K. Tags: Article Source Type: journals

A Phased Array-based Method for Damage Detection and Localization in Thin PlatesEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
A method for damage localization based on the phased array idea has been developed. Four arrays of transducers are used to perform a beam-forming procedure. Each array consists of nine transducers placed along a line, which are able to excite and register elastic waves. The A0 Lamb wave mode has been chosen for the localization method. The arrays are placed in such a way that the angular difference between them is 45° and the rotation point is the middle transducer, which is common for all the arrays. The idea has been tested on a square aluminium plate modeled by the Spectral Element Method. Two types of damage were c...
Source: Structural Health Monitoring - January 16, 2009 Category: Medical Equipment Authors: Malinowski, P., Wandowski, T., Trendafilova, I., Ostachowicz, W. Tags: Article Source Type: journals