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Sample records for damage detection system

  1. Detection of damage in axial (membrane) systems

    SciTech Connect

    Duffey, T.A.; Baker, W.E.; Farrar, C.R.; Rhee, W.H.

    1998-12-31

    In a recent paper, two methods of damage identification (Modified Damage Index and Change-in-Flexibility) were applied to detection of damage in an 8-DOF vibrating system. The goal of the work was to detect damage (reduction in stiffness of one or more of the elements) as well as to locate the particular damaged elements (S). However, the investigation was limited to numerical simulations only. In this paper, a physical, spring-mass model of a similar, degenerate 8-DOF system (7 normal modes plus a rigid-body mode) was constructed. Experiments were then performed and the modal properties of the system were determined in undamaged and damaged states. Excitation was provided either by an impact hammer or by an electromechanical shaker. Damage was induced by replacing one of the springs with a spring of lower stiffness. The Modified Damage Index method clearly isolated the location of damage for a variety of damage locations and levels of damage. The Change-in-Flexibility method, however, was found to be less reliable. The ability of the method to locate damage depended strongly on location and the level of damage as well as the number of modes included.

  2. Flat Surface Damage Detection System (FSDDS)

    NASA Technical Reports Server (NTRS)

    Williams, Martha; Lewis, Mark; Gibson, Tracy; Lane, John; Medelius, Pedro; Snyder, Sarah; Ciarlariello, Dan; Parks, Steve; Carrejo, Danny; Rojdev, Kristina

    2013-01-01

    The Flat Surface Damage Detection system (FSDDS} is a sensory system that is capable of detecting impact damages to surfaces utilizing a novel sensor system. This system will provide the ability to monitor the integrity of an inflatable habitat during in situ system health monitoring. The system consists of three main custom designed subsystems: the multi-layer sensing panel, the embedded monitoring system, and the graphical user interface (GUI). The GUI LABVIEW software uses a custom developed damage detection algorithm to determine the damage location based on the sequence of broken sensing lines. It estimates the damage size, the maximum depth, and plots the damage location on a graph. Successfully demonstrated as a stand alone technology during 2011 D-RATS. Software modification also allowed for communication with HDU avionics crew display which was demonstrated remotely (KSC to JSC} during 2012 integration testing. Integrated FSDDS system and stand alone multi-panel systems were demonstrated remotely and at JSC, Mission Operations Test using Space Network Research Federation (SNRF} network in 2012. FY13, FSDDS multi-panel integration with JSC and SNRF network Technology can allow for integration with other complementary damage detection systems.

  3. In-Situ Wire Damage Detection System

    NASA Technical Reports Server (NTRS)

    Williams, Martha K. (Inventor); Roberson, Luke B. (Inventor); Tate, Lanetra C. (Inventor); Smith, Trent M. (Inventor); Gibson, Tracy L. (Inventor); Jolley, Scott T. (Inventor); Medelius, Pedro J. (Inventor)

    2014-01-01

    An in-situ system for detecting damage in an electrically conductive wire. The system includes a substrate at least partially covered by a layer of electrically conductive material forming a continuous or non-continuous electrically conductive layer connected to an electrical signal generator adapted to delivering electrical signals to the electrically conductive layer. Data is received and processed to identify damage to the substrate or electrically conductive layer. The electrically conductive material may include metalized carbon fibers, a thin metal coating, a conductive polymer, carbon nanotubes, metal nanoparticles or a combination thereof.

  4. In-Situ Wire Damage Detection System

    NASA Technical Reports Server (NTRS)

    Williams, Martha; Roberson, Luke; Tate, Lanetra; Smith, Trent; Gibson, Tracy; Medelius, Pedro; Jolley, Scott

    2012-01-01

    An In-Situ Wire Damage Detection System (ISWDDS) has been developed that is capable of detecting damage to a wire insulation, or a wire conductor, or to both. The system will allow for realtime, continuous monitoring of wiring health/integrity and reduce the number of false negatives and false positives while being smaller, lighter in weight, and more robust than current systems. The technology allows for improved safety and significant reduction in maintenance hours for aircraft, space vehicles, satellites, and other critical high-performance wiring systems for industries such as energy production and mining. The integrated ISWDDS is comprised of two main components: (1) a wire with an innermost core conductor, an inner insulation film, a conductive layer or inherently conductive polymer (ICP) covering the inner insulation film, an outermost insulation jacket; and (2) smart connectors and electronics capable of producing and detecting electronic signals, and a central processing unit (CPU) for data collection and analysis. The wire is constructed by applying the inner insulation films to the conductor, followed by the outer insulation jacket. The conductive layer or ICP is on the outer surface of the inner insulation film. One or more wires are connected to the CPU using the smart connectors, and up to 64 wires can be monitored in real-time. The ISWDDS uses time domain reflectometry for damage detection. A fast-risetime pulse is injected into either the core conductor or conductive layer and referenced against the other conductor, producing transmission line behavior. If either conductor is damaged, then the signal is reflected. By knowing the speed of propagation of the pulse, and the time it takes to reflect, one can calculate the distance to and location of the damage.

  5. Damage detection in initially nonlinear systems

    SciTech Connect

    Bornn, Luke; Farrar, Charles; Park, Gyuhae

    2009-01-01

    The primary goal of Structural Health Monitoring (SHM) is to detect structural anomalies before they reach a critical level. Because of the potential life-safety and economic benefits, SHM has been widely studied over the past decade. In recent years there has been an effort to provide solid mathematical and physical underpinnings for these methods; however, most focus on systems that behave linearly in their undamaged state - a condition that often does not hold in complex 'real world' systems and systems for which monitoring begins mid-lifecycle. In this work, we highlight the inadequacy of linear-based methodology in handling initially nonlinear systems. We then show how the recently developed autoregressive support vector machine (AR-SVM) approach to time series modeling can be used for detecting damage in a system that exhibits initially nonlinear response. This process is applied to data acquired from a structure with induced nonlinearity tested in a laboratory environment.

  6. Cable Damage Detection System and Algorithms Using Time Domain Reflectometry

    SciTech Connect

    Clark, G A; Robbins, C L; Wade, K A; Souza, P R

    2009-03-24

    This report describes the hardware system and the set of algorithms we have developed for detecting damage in cables for the Advanced Development and Process Technologies (ADAPT) Program. This program is part of the W80 Life Extension Program (LEP). The system could be generalized for application to other systems in the future. Critical cables can undergo various types of damage (e.g. short circuits, open circuits, punctures, compression) that manifest as changes in the dielectric/impedance properties of the cables. For our specific problem, only one end of the cable is accessible, and no exemplars of actual damage are available. This work addresses the detection of dielectric/impedance anomalies in transient time domain reflectometry (TDR) measurements on the cables. The approach is to interrogate the cable using time domain reflectometry (TDR) techniques, in which a known pulse is inserted into the cable, and reflections from the cable are measured. The key operating principle is that any important cable damage will manifest itself as an electrical impedance discontinuity that can be measured in the TDR response signal. Machine learning classification algorithms are effectively eliminated from consideration, because only a small number of cables is available for testing; so a sufficient sample size is not attainable. Nonetheless, a key requirement is to achieve very high probability of detection and very low probability of false alarm. The approach is to compare TDR signals from possibly damaged cables to signals or an empirical model derived from reference cables that are known to be undamaged. This requires that the TDR signals are reasonably repeatable from test to test on the same cable, and from cable to cable. Empirical studies show that the repeatability issue is the 'long pole in the tent' for damage detection, because it is has been difficult to achieve reasonable repeatability. This one factor dominated the project. The two-step model-based approach is

  7. Damage Detection/Locating System Providing Thermal Protection

    NASA Technical Reports Server (NTRS)

    Woodard, Stanley E. (Inventor); Jones, Thomas W. (Inventor); Taylor, Bryant D. (Inventor); Qamar, A. Shams (Inventor)

    2010-01-01

    A damage locating system also provides thermal protection. An array of sensors substantially tiles an area of interest. Each sensor is a reflective-surface conductor having operatively coupled inductance and capacitance. A magnetic field response recorder is provided to interrogate each sensor before and after a damage condition. Changes in response are indicative of damage and a corresponding location thereof.

  8. System Would Detect Foreign-Object Damage in Turbofan Engine

    NASA Technical Reports Server (NTRS)

    Torso, James A.; Litt, Jonathan S.

    2006-01-01

    A proposed data-fusion system, to be implemented mostly in software, would further process the digitized and preprocessed outputs of sensors in a turbofan engine to detect foreign-object damage (FOD) [more precisely, damage caused by impingement of such foreign objects as birds, pieces of ice, and runway debris]. The proposed system could help a flight crew to decide what, if any, response is necessary to complete a flight safely, and could aid mechanics in deciding what post-flight maintenance action might be needed. The sensory information to be utilized by the proposed system would consist of (1) the output of an accelerometer in an engine-vibration-monitoring subsystem and (2) features extracted from a gas path analysis. ["Gas path analysis" (GPA) is a term of art that denotes comprehensive analysis of engine performance derived from readings of fuel-flow meters, shaft-speed sensors, temperature sensors, and the like.] The acceleration signal would first be processed by a wavelet-transform-based algorithm, using a wavelet created for the specific purpose of finding abrupt FOD-induced changes in noisy accelerometer signals. Two additional features extracted would be the amplitude of vibration (determined via a single- frequency Fourier transform calculated at the rotational speed of the engine), and the rate of change in amplitude due to an FOD-induced rotor imbalance. This system would utilize two GPA features: the fan efficiency and the rate of change of fan efficiency with time. The selected GPA and vibrational features would be assessed by two fuzzy-logic inference engines, denoted the "Gas Path Expert" and the "Vibration Expert," respectively (see Figure 1). Each of these inference engines would generate a "possibility" distribution for occurrence of an FOD event: Each inference engine would assign, to its input information, degrees of membership, which would subsequently be transformed into basic probability assignments for the gas path and vibration

  9. Damage Detection and Verification System (DDVS) for In-Situ Health Monitoring

    NASA Technical Reports Server (NTRS)

    Williams, Martha K.; Lewis, Mark; Szafran, J.; Shelton, C.; Ludwig, L.; Gibson, T.; Lane, J.; Trautwein, T.

    2015-01-01

    Project presentation for Game Changing Program Smart Book Release. Detection and Verification System (DDVS) expands the Flat Surface Damage Detection System (FSDDS) sensory panels damage detection capabilities and includes an autonomous inspection capability utilizing cameras and dynamic computer vision algorithms to verify system health. Objectives of this formulation task are to establish the concept of operations, formulate the system requirements for a potential ISS flight experiment, and develop a preliminary design of an autonomous inspection capability system that will be demonstrated as a proof-of-concept ground based damage detection and inspection system.

  10. Damage detection in nonlinear systems using multiple system augmentations and matrix updating

    NASA Astrophysics Data System (ADS)

    D'Souza, Kiran; Epureanu, Bogdan I.

    2006-03-01

    Recently, a damage detection method for nonlinear systems using model updating has been developed by the authors. The method uses an augmented linear model of the system, which is determined from the functional form of the nonlinearities and a nonlinear discrete model of the system. The modal properties of the augmented system after the onset of damage are extracted from the system using a modal analysis technique that uses known but not prescribed forcing. Minimum Rank Perturbation Theory was generalized so that damage location and extent could be determined using the augmented modal properties. The method was demonstrated previously for cubic springs and Coulomb friction nonlinearities. In this work, the methodology is extended to handle large systems where only the first few of the augmented eigenvectors are known. The methodology capitalizes on the ability to create multiple augmentations for a single nonlinear system. Cubic spring nonlinearities are explored within a nonlinear 3-bay truss structure for various damage scenarios simulated numerically.

  11. The study of target damage assessment system based on image change detection

    NASA Astrophysics Data System (ADS)

    Zhao, Ping; Yang, Fan; Feng, Xinxi

    2009-10-01

    Target Damage Assessment (TDA) system is an important component of the intelligent command and control system. The method of building TDA based on Image Change Detection can greatly improve the system efficiency and accuracy, thus get a fast and precise assessment results. This paper firstly analyzes the structure of TDA system. Then studies the key technology in this system. Finally, gives an evaluation criteria based on image change detection of the target damage assessment system.

  12. SmartComposite system for impact damage detection on composite structures

    NASA Astrophysics Data System (ADS)

    Qing, Xinlin P.; Beard, Shawn J.; Pinsonnault, Jerome; Banerjee, Sourav

    2009-03-01

    Composites are increasingly used in numerous structural applications because of their low weight-to-strength and weight-to-stiffness ratios. However, the performance and behavior characteristics of nearly all in-service composite structures can be affected by degradation resulting from sustained use as well as from exposure to severe environmental conditions or damage resulting from external conditions such as impact, loading abrasion, operator abuse. These factors can have serious consequences on the structures relative to safety, cost, and operational capability. In this paper, a SmartComposite system is introduced for monitoring the integrity of large composite structures. Key features of the system include miniaturized lightweight hardware, self-diagnostics and an adaptive algorithm to automatically compensate for damaged sensors, reliable damage detection under different environmental conditions, and generation of POD curves. Tests were conducted on composite test article with sensor network embedded inside the composite skin or surface mounted to demonstrate the impact damage detection capability of the SmartComposite System. It is clear from the test results that the SmartComposite system can successfully detect impact damages, including both damage location and probability of damage size.

  13. Damage Detection System with Sub-microsecond Resolution

    SciTech Connect

    Udd, E; Benterou, J

    2008-02-11

    Fiber optic grating sensors have been used to measure multi-dimensional strain, pressure, temperature, corrosion and moisture. This paper presents a method of using fiber grating sensors to measure the position and velocity of a very fast event associated with a blast wave. A chirped fiber grating of 50 mm length is placed in a highly energetic material. The action of the shock wave is to destroy the fiber grating as it propagates along it. By using a spectral filter such as a chirped fiber grating in combination with high speed detectors the position and velocity of the shock wave may be determined. A layout of a system used to experimentally verify this technique is described and results presented for two different highly energetic materials.

  14. A multi-stage approach for damage detection in structural systems based on flexibility

    NASA Astrophysics Data System (ADS)

    Grande, E.; Imbimbo, M.

    2016-08-01

    The paper proposes a fusion approach for damage detection in structural applications in the case of multiple damage locations and three-dimensional systems. Based on the Dempster-Shafer evidence theory, a multi-stage approach is proposed with the mode shapes assumed as primary sources and local decisions based on a flexibility method. The proposed approach has been applied to two case studies, a a fixed end beam analyzed in other papers and a three dimensional structures codified in a Benchmark problem. Both the case studies have shown the ability and the efficiency of the proposed approach to detect damage also in the case of multiple damage, limited number of identified parameters and noise measurements.

  15. Use of near-infrared video recording system for the detection of freeze damaged citrus leaves

    NASA Technical Reports Server (NTRS)

    Escobar, D. E.; Bowen, R. L.; Gausman, H. W.; Cooper, G. (Principal Investigator)

    1982-01-01

    A video recording system with a visible light blocking filter to give sensitivity in the 0.78 m to 1.1 m waveband detected freeze-damaged citrus leaves rapidly. With this technique, the time to analyze images can be decreased from about one day for conventional photography to less than one hour for video recording.

  16. Excitation optimization for damage detection

    SciTech Connect

    Bement, Matthew T; Bewley, Thomas R

    2009-01-01

    A technique is developed to answer the important question: 'Given limited system response measurements and ever-present physical limits on the level of excitation, what excitation should be provided to a system to make damage most detectable?' Specifically, a method is presented for optimizing excitations that maximize the sensitivity of output measurements to perturbations in damage-related parameters estimated with an extended Kalman filter. This optimization is carried out in a computationally efficient manner using adjoint-based optimization and causes the innovations term in the extended Kalman filter to be larger in the presence of estimation errors, which leads to a better estimate of the damage-related parameters in question. The technique is demonstrated numerically on a nonlinear 2 DOF system, where a significant improvement in the damage-related parameter estimation is observed.

  17. Multifunctional system for active noise control and damage detection on a typical aeronautical structure

    NASA Astrophysics Data System (ADS)

    Lecce, Leonardo; Viscardi, Massimo; Zumpano, Giuseppe

    2001-08-01

    The present work relates to the assessment and testing of a multifunctional intelligent system, based upon the use of piezoelectric devices, devoted both to the active noise and vibration control and to damage detection f the structure. In the control application, the piezoelectric devices (in form of patches) play the role of actuators; their induced secondary vibration field has the target to reduce the primary one through a specific control algorithm and system. In the health monitoring application, the piezo devices play both the roles of actuators and sensors. In fact the developed technique is primarily based upon the evaluation and comparison of the structure Frequency Response Functions (FRF) that intrinsically contains all the information regarding the structural properties whose change may be correlated with incipient damages. The aforementioned application were investigated and experimentally assessed with good results with reference to a typical partial fuselage structure (three frames, eight stringers and the skin panels: 1.2 m x 1.7 m). On the noise control application side, a height sensors/height actuators control architecture was then assessed and experimentally tested whose results may be synthesized in a 30 dB vibration level reduction at sensors locations and more than 20 dB of reduction of the associated noise field. In the optic of a multifunctional intelligent system, the aforementioned set of piezo's was decided to be used also for health monitoring application. As a preliminary activity, an extensive monitoring was performed on the integer structure to verify the sensibility of the system and the stability of the defined Damage Index (DI) in respect to environmental factor not related to structural real modification. To verify the sensibility of the technique to reveal and locate a typical shear clip damage, a set of rivets were successively cut in the area surrounding the frame shear clip, and relative FRF's were acquired and relative DI

  18. Multi-Dimensional Damage Detection

    NASA Technical Reports Server (NTRS)

    Gibson, Tracy L. (Inventor); Williams, Martha K. (Inventor); Lewis, Mark E. (Inventor); Roberson, Luke B. (Inventor); Snyder, Sarah J. (Inventor); Medelius, Pedro J. (Inventor)

    2016-01-01

    Methods and systems may provide for a structure having a plurality of interconnected panels, wherein each panel has a plurality of detection layers separated from one another by one or more non-detection layers. The plurality of detection layers may form a grid of conductive traces. Additionally, a monitor may be coupled to each grid of conductive traces, wherein the monitor is configured to detect damage to the plurality of interconnected panels in response to an electrical property change with respect to one or more of the conductive traces. In one example, the structure is part of an inflatable space platform such as a spacecraft or habitat.

  19. Rotor health monitoring and damage detection utilizing a disk spin simulation system

    NASA Astrophysics Data System (ADS)

    Gyekenyesi, Andrew L.; Baaklini, George Y.

    2001-08-01

    This paper describes a unique, disk spin simulation system currently being utilized at NASA Glenn Research Center. The system allows for precision controlled spin tests that can facilitate the application of various sensing technologies for in-situ detection of rotor damage. In addition, the disk spin simulation system has the capability for elevated temperatures up to 540°C (1000°F). The current rotor used to simulate a bladed disk consists of a 46 cm(18 in.) diameter, titanium disk with 30 machined gear teeth. The gear design imitates the blades of a compressor or turbine disk. Operating speeds for the system can reach 1000 revolutions per minute. This allows the system to achieve circumferential velocities paralleling those seen in actual aircraft engines. For this study, a new, innovative capacitive sensing system was used to monitor blade tip clearance (i.e., gear tooth clearance). In turn, the sensor information was employed to calculate the change in the center of mass of the rotor system. T he capacitive sensor and corresponding software were analyzed by attaching a localized weight at numerous positions on the disk. Upon calculating the change in the center of mass, the sensitivities of the sensor and software were established. In the end, it is hoped that by studying the motion and position of blades as well as the change in the center of mass of a rotor system, it may be feasible to identify alterations due to damage (e.g., cracks) eitehr in the blades or the disk itself.

  20. Structural damage detection via nonlinear system identification and structural intensity methods

    NASA Astrophysics Data System (ADS)

    Semperlotti, Fabio

    sensory system for data acquisition. The second technique presented in this work is based on the use of Structural Intensity (SI) as a damage detection tool. Although SI has been used in the past for structural vibrations and noise control systems, applications to damage detection are still very limited. A numerical study exploring the relationship between several structural (loss factors, damage size) and experimental (frequency resolution, sensor size and placements) parameters and the SI field is presented. The changes in SI at discrete structural locations are used as the damage metric. In order to improve performance and adaptability of the SI based system over a wide spectrum of structures, the concept of Active Energy Sink (AES) is introduced. A feedback control system is used to realize the absorption device. The AES design is presented, and validated through experimental testing. An increase in the closed loop loss factors up to eta=29% was measured for the low frequency modes. Finally, the concept of Nonlinear Structural Surface Intensity (NSSI) is presented. The SI-based SHM was initially developed by relying on the availability of a baseline for the healthy structure. In order to develop a baseline-free technique, the HHRS is integrated into the SI concept. This approach results in a single technique which benefits from the localization capabilities from the HHRS approach and of the sizing capabilities proper of the SI approach.

  1. Detection and Location of Damage on Pipelines

    SciTech Connect

    Karen A. Moore; Robert Carrington; John Richardson

    2003-11-01

    The INEEL has developed and successfully tested a real-time pipeline damage detection and location system. This system uses porous metal resistive traces applied to the pipe to detect and locate damage. The porous metal resistive traces are sprayed along the length of a pipeline. The unique nature and arrangement of the traces allows locating the damage in real time along miles of pipe. This system allows pipeline operators to detect damage when and where it is occurring, and the decision to shut down a transmission pipeline can be made with actual real-time data, instead of conservative estimates from visual inspection above the area.

  2. Development of a wireless, self-sustaining damage detection sensor system based on chemiluminescence for structural health monitoring

    NASA Astrophysics Data System (ADS)

    Kuang, K. S. C.

    2014-03-01

    A novel application of chemiluminescence resulting from the chemical reaction in a glow-stick as sensors for structural health monitoring is demonstrated here. By detecting the presence of light emitting from these glow-sticks, it is possible to develop a low-cost sensing device with the potential to provide early warning of damage in a variety of engineering applications such as monitoring of cracks or damage in concrete shear walls, detecting of ground settlement, soil liquefaction, slope instability, liquefaction-related damage of underground structure and others. In addition, this paper demonstrates the ease of incorporating wireless capability to the sensor device and the possibility of making the sensor system self-sustaining by means of a renewable power source for the wireless module. A significant advantage of the system compared to previous work on the use of plastic optical fibre (POF) for damage detection is that here the system does not require an electrically-powered light source. Here, the sensing device, embedded in a cement host, is shown to be capable of detecting damage. A series of specimens with embedded glow-sticks have been investigated and an assessment of their damage detection capability will be reported. The specimens were loaded under flexure and the sensor responses were transmitted via a wireless connection.

  3. Impact damage detection system using small-diameter optical fiber sensors wavily embedded in CFRP laminate structures

    NASA Astrophysics Data System (ADS)

    Tsutsui, Hiroaki; Kawamata, Akio; Kimoto, Junichi; Isoe, Akira; Hirose, Yasuo; Sanda, Tomio; Takeda, Nobuo

    2003-08-01

    It is well known that barely visible damage is often induced in composite structures subjected to out-of plane impact, and the mechanical properties of the composites decrease markedly. In this study, some element technologies for the detection of the damage are explained. Those are (1) the technologies for the arrangement of embedded small-diameter optical fibers which have no serious effect on the mechanical properties of composites, (2) the technologies for the egress of the optical fibers using "the embedded connector for smart structures" which can be trimmed without care about the optical fibers, (3) the technologies for the damage detection system that has the functions for data acquisition and analysis, the evaluation of the initiation and the position of damage, and the visualization of damage information. The impact test using the composite airframe demonstrator is conducted. The sensors embedded in the upper panel of the stiffened cylindrical composite structure with 1.5 m in diameter and 3 m in length, are FBG sensors for strain measurement and the optical fibers for optical loss measurement. The detection of damage in the composite structures using a developed damage detection system is demonstrated.

  4. Structural Damage Detection Using Virtual Passive Controllers

    NASA Technical Reports Server (NTRS)

    Lew, Jiann-Shiun; Juang, Jer-Nan

    2001-01-01

    This paper presents novel approaches for structural damage detection which uses the virtual passive controllers attached to structures, where passive controllers are energy dissipative devices and thus guarantee the closed-loop stability. The use of the identified parameters of various closed-loop systems can solve the problem that reliable identified parameters, such as natural frequencies of the open-loop system may not provide enough information for damage detection. Only a small number of sensors are required for the proposed approaches. The identified natural frequencies, which are generally much less sensitive to noise and more reliable than the identified natural frequencies, are used for damage detection. Two damage detection techniques are presented. One technique is based on the structures with direct output feedback controllers while the other technique uses the second-order dynamic feedback controllers. A least-squares technique, which is based on the sensitivity of natural frequencies to damage variables, is used for accurately identifying the damage variables.

  5. Detection of impact damage on thermal protection systems using thin-film piezoelectric sensors for integrated structural health monitoring

    NASA Astrophysics Data System (ADS)

    Na, Jeong K.; Kuhr, Samuel J.; Jata, Kumar V.

    2008-03-01

    Thermal Protection Systems (TPS) can be subjected to impact damage during flight and/or during ground maintenance and/or repair. AFRL/RXLP is developing a reliable and robust on-board sensing/monitoring capability for next generation thermal protection systems to detect and assess impact damage. This study was focused on two classes of metallic thermal protection tiles to determine threshold for impact damage and develop sensing capability of the impacts. Sensors made of PVDF piezoelectric film were employed and tested to evaluate the detectability of impact signals and assess the onset or threshold of impact damage. Testing was performed over a range of impact energy levels, where the sensors were adhered to the back of the specimens. The PVDF signal levels were analyzed and compared to assess damage, where digital microscopy, visual inspection, and white light interferometry were used for damage verification. Based on the impact test results, an assessment of the impact damage thresholds for each type of metallic TPS system was made.

  6. Experimental validation of a modal flexibility-based damage detection method for a cyber-physical system

    NASA Astrophysics Data System (ADS)

    Martinez-Castro, Rosana E.; Eskew, Edward L.; Jang, Shinae

    2014-03-01

    The detection and localization of damage in a timely manner is critical in order to avoid the failure of structures. When a structure is subjected to an unscheduled impulsive force, the resulting damage can lead to failure in a very short period of time. As such, a monitoring strategy that can adapt to variability in the environment and that anticipates changes in physical processes has the potential of detecting, locating and mitigating damage. These requirements can be met by a cyber-physical system (CPS) equipped with Wireless Smart Sensor Network (WSSN) systems that is capable of measuring and analyzing dynamic responses in real time using on-board in network processing. The Eigenparameter Decomposition of Structural Flexibility Change (ED) Method is validated with real data and considered to be used in the computational core of this CPS. The condition screening is implemented on a damaged structure and compared to an original baseline calculation, hence providing a supervised learning environment. An experimental laboratory study on a 5-story shear building with three damage conditions subjected to an impulsive force has been chosen to validate the effectiveness of the method proposed to locate and quantify the extent of damage. A numerical simulation of the same building subject to band-limited white noise has also been developed with this purpose. The effectiveness of the ED Method to locate damage is compared to that of the Damage Index Method. With some modifications, the ED Method is capable of locating and quantifying damage satisfactorily in a shear building subject to a lower frequency content predominant excitation.

  7. Optimal controller design for structural damage detection

    NASA Astrophysics Data System (ADS)

    Lew, Jiann-Shiun

    2005-03-01

    The virtual passive control technique has recently been applied to structural damage detection, where the virtual passive controller only uses the existing control devices, and no additional physical elements are attached to the tested structure. One important task is to design passive controllers that can enhance the sensitivity of the identified parameters, such as natural frequencies, to structural damage. This paper presents a novel study of an optimal controller design for structural damage detection. We apply not only passive controllers but also low-order and fixed-structure controllers, such as PID controllers. In the optimal control design, the performance of structural damage detection is based on the application of a neural network technique, which uses the pattern of the correlation between the natural frequency changes of the tested system and the damaged system.

  8. Development of integrated damage detection system for international America's Cup class yacht structures using a fiber optic distributed sensor

    NASA Astrophysics Data System (ADS)

    Akiyoshi, Shimada; Naruse, Hiroshi; Uzawa, Kyoshi; Murayama, Hideaki; Kageyama, Kazuro

    2000-06-01

    We constructed a new health monitoring system to detect damage using a fiber optic distributed sensor, namely a Brillouin optical time domain reflectometer (BOTDR), and installed it in International America's Cup Class (IACC) yachts, the Japanese entry in America's Cup 2000. IACC yachts are designed to be as fast as possible, so it is essential that they are lightweight and encounter minimum water resistance. Advanced composite sandwich structures, made with carbon fiber reinforced plastic (CFRP) skins and a honeycomb core, are used to achieve the lightweight structure. Yacht structure designs push the strength of the materials to their limit and so it is important to detect highly stressed or damaged regions that might cause a catastrophic fracture. The BOTDR measures changes in the Brillouin frequency shift caused by distributed strain along one optical fiber. We undertook two experiments: a pulling test and a four point bending test on a composite beam. The former showed that no slippage occurred between the optical fiber glass and its coating. The latter confirmed that a debonding between the skin and the core of 300 mm length could be found with the BOTDR. Next we examined the effectiveness with which this system can assess the structural integrity of IACC yachts. The results show that our system has the potential for use as a damage detection system for smart structures.

  9. Evaluation of SonicIR handheld system on composite impact damage detection

    NASA Astrophysics Data System (ADS)

    Han, Xiaoyan; Ar-Rasheed, Justin M.; Zhang, Ding; Lubowicki, Anthony

    2016-02-01

    Sonic Infrared (IR) Imaging has shown its capability as a fast, wide area NDE method. We have demonstrated its wide applications to different types of materials and structures. Along the path of the development of this technology, we have studied the effect of the input UT source transducer frequency, heating mechanism of different types of defects, the role coupling materials, the non-linear phenomena, the effect of crack closure, etc. The WSU team has also been developing prototypes of this technology for future in-field inspection. In this paper, we present the evaluation of the system with structured composite samples containing widespread impact damages.

  10. Smart accelerometer. [vibration damage detection

    NASA Technical Reports Server (NTRS)

    Bozeman, Richard J., Jr. (Inventor)

    1994-01-01

    The invention discloses methods and apparatus for detecting vibrations from machines which indicate an impending malfunction for the purpose of preventing additional damage and allowing for an orderly shutdown or a change in mode of operation. The method and apparatus is especially suited for reliable operation in providing thruster control data concerning unstable vibration in an electrical environment which is typically noisy and in which unrecognized ground loops may exist.

  11. Damage detection via shortest-path network sampling

    NASA Astrophysics Data System (ADS)

    Ciulla, Fabio; Perra, Nicola; Baronchelli, Andrea; Vespignani, Alessandro

    2014-05-01

    Large networked systems are constantly exposed to local damages and failures that can alter their functionality. The knowledge of the structure of these systems is, however, often derived through sampling strategies whose effectiveness at damage detection has not been thoroughly investigated so far. Here, we study the performance of shortest-path sampling for damage detection in large-scale networks. We define appropriate metrics to characterize the sampling process before and after the damage, providing statistical estimates for the status of nodes (damaged, not damaged). The proposed methodology is flexible and allows tuning the trade-off between the accuracy of the damage detection and the number of probes used to sample the network. We test and measure the efficiency of our approach considering both synthetic and real networks data. Remarkably, in all of the systems studied, the number of correctly identified damaged nodes exceeds the number of false positives, allowing us to uncover the damage precisely.

  12. Intelligent-based Structural Damage Detection Model

    SciTech Connect

    Lee, Eric Wai Ming; Yu, K.F.

    2010-05-21

    This paper presents the application of a novel Artificial Neural Network (ANN) model for the diagnosis of structural damage. The ANN model, denoted as the GRNNFA, is a hybrid model combining the General Regression Neural Network Model (GRNN) and the Fuzzy ART (FA) model. It not only retains the important features of the GRNN and FA models (i.e. fast and stable network training and incremental growth of network structure) but also facilitates the removal of the noise embedded in the training samples. Structural damage alters the stiffness distribution of the structure and so as to change the natural frequencies and mode shapes of the system. The measured modal parameter changes due to a particular damage are treated as patterns for that damage. The proposed GRNNFA model was trained to learn those patterns in order to detect the possible damage location of the structure. Simulated data is employed to verify and illustrate the procedures of the proposed ANN-based damage diagnosis methodology. The results of this study have demonstrated the feasibility of applying the GRNNFA model to structural damage diagnosis even when the training samples were noise contaminated.

  13. Vibration-Based Damage Detection in Rotating Machinery

    SciTech Connect

    Farrar, C.R.; Duffey, T.A.

    1999-06-28

    Damage detection as determined from changes in the vibration characteristics of a system has been a popular research topic for the last thirty years. Numerous damage identification algorithms have been proposed for detecting and locating damage in structural and mechanical systems. To date, these damage-detection methods have shown mixed results. A particular application of vibration-based damage detection that has perhaps enjoyed the greatest success is that of damage detection in rotating machinery. This paper summarizes the state of technology in vibration-based damage detection applied to rotating machinery. The review interprets the damage detection process in terms of a statistical pattern recognition paradigm that encompasses all vibration-based damage detection methods and applications. The motivation for the study reported herein is to identify the reasons that vibration-based damage detection has been successfully applied to rotating machinery, but has yet to show robust applications to civil engineering infrastructure. The paper concludes by comparing and contrasting the vibration-based damage detection applied to rotating machinery with large civil engineering infrastructure applications.

  14. Acoustic emission beamforming for enhanced damage detection

    NASA Astrophysics Data System (ADS)

    McLaskey, Gregory C.; Glaser, Steven D.; Grosse, Christian U.

    2008-03-01

    As civil infrastructure ages, the early detection of damage in a structure becomes increasingly important for both life safety and economic reasons. This paper describes the analysis procedures used for beamforming acoustic emission techniques as well as the promising results of preliminary experimental tests on a concrete bridge deck. The method of acoustic emission offers a tool for detecting damage, such as cracking, as it occurs on or in a structure. In order to gain meaningful information from acoustic emission analyses, the damage must be localized. Current acoustic emission systems with localization capabilities are very costly and difficult to install. Sensors must be placed throughout the structure to ensure that the damage is encompassed by the array. Beamforming offers a promising solution to these problems and permits the use of wireless sensor networks for acoustic emission analyses. Using the beamforming technique, the azmuthal direction of the location of the damage may be estimated by the stress waves impinging upon a small diameter array (e.g. 30mm) of acoustic emission sensors. Additional signal discrimination may be gained via array processing techniques such as the VESPA process. The beamforming approach requires no arrival time information and is based on very simple delay and sum beamforming algorithms which can be easily implemented on a wireless sensor or mote.

  15. Current Status of Hybrid Bearing Damage Detection

    NASA Technical Reports Server (NTRS)

    Dempsey, Paula J.; Certo, Joseph M.; Morales, Wilfredo

    2004-01-01

    Advances in material development and processing have led to the introduction of ceramic hybrid bearings for many applications. The introduction of silicon nitride hybrid bearings into the high pressure oxidizer turbopump, on the space shuttle main engine, led NASA to solve a highly persistent and troublesome bearing problem. Hybrid bearings consist of ceramic balls and steel races. The majority of hybrid bearings utilize Si3N4 balls. The aerospace industry is currently studying the use of hybrid bearings and naturally the failure modes of these bearings become an issue in light of the limited data available. In today s turbine engines and helicopter transmissions, the health of the bearings is detected by the properties of the debris found in the lubrication line when damage begins to occur. Current oil debris sensor technology relies on the magnetic properties of the debris to detect damage. Since the ceramic rolling elements of hybrid bearings have no metallic properties, a new sensing system must be developed to indicate the system health if ceramic components are to be safely implemented in aerospace applications. The ceramic oil debris sensor must be capable of detecting ceramic and metallic component damage with sufficient reliability and forewarning to prevent a catastrophic failure. The objective of this research is to provide a background summary on what is currently known about hybrid bearing failure modes and to report preliminary results on the detection of silicon nitride debris, in oil, using a commercial particle counter.

  16. Damage detection using multivariate recurrence quantification analysis

    NASA Astrophysics Data System (ADS)

    Nichols, J. M.; Trickey, S. T.; Seaver, M.

    2006-02-01

    Recurrence-quantification analysis (RQA) has emerged as a useful tool for detecting subtle non-stationarities and/or changes in time-series data. Here, we extend the RQA analysis methods to multivariate observations and present a method by which the "length scale" parameter ɛ (the only parameter required for RQA) may be selected. We then apply the technique to the difficult engineering problem of damage detection. The structure considered is a finite element model of a rectangular steel plate where damage is represented as a cut in the plate, starting at one edge and extending from 0% to 25% of the plate width in 5% increments. Time series, recorded at nine separate locations on the structure, are used to reconstruct the phase space of the system's dynamics and subsequently generate the multivariate recurrence (and cross-recurrence) plots. Multivariate RQA is then used to detect damage-induced changes to the structural dynamics. These results are then compared with shifts in the plate's natural frequencies. Two of the RQA-based features are found to be more sensitive to damage than are the plate's frequencies.

  17. Damage detection in concrete and cementitious composites

    NASA Astrophysics Data System (ADS)

    Wu, Hwai-Chung; Pai, P. Frank

    2008-03-01

    Traditionally ultrasonic testing is used to estimate the extent of damage in a concrete structure. However Pulse-velocity and amplitude attenuation methods are not very reliable, and are difficult to reveal early damage of concrete. In a previous study, a new active modulation approach, Nonlinear Active Wave Modulation Spectroscopy, was developed and found promising for early detection of damage in concrete. In this procedure, a probe wave is passed through the system in a fashion similar to regular acoustic methods for inspection. Simultaneously, a second, low-frequency modulating wave is applied to the system to effectively change the size and stiffness of flaws microscopically and cyclically, thereby causing the frequency modulation to change cyclically as well. It has been also shown that it is advantageous to apply the Hilbert-Huang transform to decompose nonlinear non-stationary time-domain responses of plain concrete. Such procedure leads to improving the damage detection sensitivity of this modulation method in concrete. In this paper, further investigation on mortar and fiber reinforced concrete will be presented and discussed.

  18. Long term application of bus monitoring system to short and medium span bridges and damage detection

    NASA Astrophysics Data System (ADS)

    Miyamoto, Ayaho; Lúcio, Válter J. G.; Emoto, Hisao; Tanaka, Hideaki

    2015-07-01

    In this study, as one solution to the problem for condition assessment of existing short and medium span reinforced/prestressed concrete bridges, a new monitoring method using a public bus as part of a public transit system (bus monitoring system) is proposed, along with safety indices, namely, characteristic deflection, which is relatively free from the influence of dynamic disturbances due to such factors as the roughness of the road surface, and a structural anomaly parameter. A basic study was conducted by using the results of technical verification experiments and numerical analysis simulation. This paper describes the details of not only how to assess the bridge condition by public bus vibration measured in operating on Ube City bus network as a specific example for verify the system but also what kind of consideration we need to apply the system to existing bridges in overseas country.

  19. Ability of Impedance-Based Health Monitoring To Detect Structural Damage of Propulsion System Components Assessed

    NASA Technical Reports Server (NTRS)

    Martin, Richard E.; Gyekenyesi, Andrew L.; Sawicki, Jerzy T.; Baaklini, George Y.

    2005-01-01

    Impedance-based structural-health-monitoring uses piezoelectric (PZT) patches that are bonded onto or embedded in a structure. Each individual patch behaves as both an actuator of the surrounding structural area as well as a sensor of the structural response. The size of the excited area varies with the geometry and material composition of the structure, and an active patch is driven by a sinusoidal voltage sweep. When a PZT patch is subjected to an electric field, it produces a mechanical strain; and when it is stressed, it produces an electric charge. Since the patch is bonded to the structure, driving a patch deforms and vibrates the structure. The structure then produces a localized dynamic response. This structural system response is transferred back to the PZT patch, which in turn produces an electrical response. The electromechanical impedance method is based on the principle of electromechanical coupling between the active sensor and the structure, which allows researchers to assess local structural dynamics directly by interrogating a distributed sensor array. Because of mechanical coupling between the sensor and the host structure, this mechanical effect is picked up by the sensor and, through electromechanical coupling inside the active element, is reflected in electrical impedance measured at the sensor s terminals.

  20. Rotor damage detection by using piezoelectric impedance

    NASA Astrophysics Data System (ADS)

    Qin, Y.; Tao, Y.; Mao, Y. F.

    2016-04-01

    Rotor is a core component of rotary machinery. Once the rotor has the damage, it may lead to a major accident. Thus the quantitative rotor damage detection method based on piezoelectric impedance is studied in this paper. With the governing equation of piezoelectric transducer (PZT) in a cylindrical coordinate, the displacement along the radius direction is derived. The charge of PZT is calculated by the electric displacement. Then, by the use of the obtained displacement and charge, an analytic piezoelectric impedance model of the rotor is built. Given the circular boundary condition of a rotor, annular elements are used as the analyzed objects and spectral element method is used to set up the damage detection model. The Electro-Mechanical (E/M) coupled impedance expression of an undamaged rotor is deduced with the application of a low-cost impedance test circuit. A Taylor expansion method is used to obtain the approximate E/M coupled impedance expression for the damaged rotor. After obtaining the difference between the undamaged and damaged rotor impedance, a rotor damage detection method is proposed. This method can directly calculate the change of bending stiffness of the structural elements, it follows that the rotor damage can be effectively detected. Finally, a preset damage configuration is used for the numerical simulation. The result shows that the quantitative damage detection algorithm based on spectral element method and piezoelectric impedance proposed in this paper can identify the location and the severity of the damaged rotor accurately.

  1. Multi-Dimensional Damage Detection for Surfaces and Structures

    NASA Technical Reports Server (NTRS)

    Williams, Martha; Lewis, Mark; Roberson, Luke; Medelius, Pedro; Gibson, Tracy; Parks, Steen; Snyder, Sarah

    2013-01-01

    Current designs for inflatable or semi-rigidized structures for habitats and space applications use a multiple-layer construction, alternating thin layers with thicker, stronger layers, which produces a layered composite structure that is much better at resisting damage. Even though such composite structures or layered systems are robust, they can still be susceptible to penetration damage. The ability to detect damage to surfaces of inflatable or semi-rigid habitat structures is of great interest to NASA. Damage caused by impacts of foreign objects such as micrometeorites can rupture the shell of these structures, causing loss of critical hardware and/or the life of the crew. While not all impacts will have a catastrophic result, it will be very important to identify and locate areas of the exterior shell that have been damaged by impacts so that repairs (or other provisions) can be made to reduce the probability of shell wall rupture. This disclosure describes a system that will provide real-time data regarding the health of the inflatable shell or rigidized structures, and information related to the location and depth of impact damage. The innovation described here is a method of determining the size, location, and direction of damage in a multilayered structure. In the multi-dimensional damage detection system, layers of two-dimensional thin film detection layers are used to form a layered composite, with non-detection layers separating the detection layers. The non-detection layers may be either thicker or thinner than the detection layers. The thin-film damage detection layers are thin films of materials with a conductive grid or striped pattern. The conductive pattern may be applied by several methods, including printing, plating, sputtering, photolithography, and etching, and can include as many detection layers that are necessary for the structure construction or to afford the detection detail level required. The damage is detected using a detector or

  2. Optical detection of DNA damage

    NASA Astrophysics Data System (ADS)

    Rogers, Kim R.; Apostol, A.; Cembrano, J.

    1999-02-01

    A rapid and sensitive fluorescence assay for oxidative damage to calf thymus DNA is reported. A decrease in the transition temperature for strand separation resulted from exposure of the DNA to the reactive decomposition products of 3- morpholinosydnonimine (SIN-1) (i.e., nitric oxide, superoxide, peroxynitrite, hydrogen peroxide, and hydroxyl radicals). A decrease in melting temperature of 12 degrees Celsius was indicative of oxidative damage including single strand chain breaks. Double stranded (ds) and single stranded (ss) forms of DNA were determined using the indicator dyes ethidium bromide and PicoGreen. The change in DNA 'melting' curves was dependant on the concentration of SIN-1 and was most pronounced at 75 degrees Celsius. This chemically induced damage was significantly inhibited by sodium citrate, tris(hydroxymethyl)aminomethane (Tris), and diethylenetriaminepentaacetic acid (DTPA), but was unaffected by superoxide dismutase (SOD), catalase, ethylenediamine tetraacietic acid (EDTA), or deferoxamine. Lowest observable effect level for SIN-1-induced damage was 200 (mu) M.

  3. Dynamic based damage detection in composite structures

    NASA Astrophysics Data System (ADS)

    Banerjee, Sauvik; Ricci, Fabrizio; Baid, Harsh; Mal, Ajit K.

    2009-03-01

    Advanced composites are being used increasingly in state-of-the-art aircraft and aerospace structures. In spite of their many advantages, composite materials are highly susceptible to hidden flaws that may occur at any time during the life cycle of a structure, and if undetected, may cause sudden and catastrophic failure of the entire structure. This paper is concerned with the detection and characterization of hidden defects in composite structures before they grow to a critical size. A methodology for automatic damage identification and localization is developed using a combination of vibration and wave propagation data. The structure is assumed to be instrumented with an array of actuators and sensors to excite and record its dynamic response, including vibration and wave propagation effects. A damage index, calculated from the measured dynamical response of the structure in a previous (reference) state and the current state, is introduced as a determinant of structural damage. The indices are used to identify low velocity impact damages in increasingly complex composite structural components. The potential application of the approach in developing health monitoring systems in defects-critical structures is indicated.

  4. Remote detection of forest damage

    NASA Technical Reports Server (NTRS)

    Rock, B. N.; Vogelmann, J. E.; Vogelmann, A. F.; Hoshizaki, T.; Williams, D. L.

    1986-01-01

    The use of remote sensing to discriminate, measure, and map forest damage is evaluated. TM spectal coverage, a helicopter-mounted radiometer, and ground-based surveys were utilized to examine the responses of the spruces and firs of Camels Hump Mountain, Vermont to stresses, such as pollution and trace metals. The basic spectral properties of vegetation are described. Forest damage at the site was estimated as 11.8-76.0 percent for the spruces and 19-43.8 percent for the balsam firs. Shifts in the spectra of the conifers in particular in the near IR region are analyzed, and variations in the mesophyll cell anatomy and pigment content of the spruces and firs are investigated. The relations between canopy moisture and damage is studied. The TM data are compared to aircraft data and found to be well correlated.

  5. Damage Detection Using Holography and Interferometry

    NASA Technical Reports Server (NTRS)

    Decker, Arthur J.

    2003-01-01

    This paper reviews classical approaches to damage detection using laser holography and interferometry. The paper then details the modern uses of electronic holography and neural-net-processed characteristic patterns to detect structural damage. The design of the neural networks and the preparation of the training sets are discussed. The use of a technique to optimize the training sets, called folding, is explained. Then a training procedure is detailed that uses the holography-measured vibration modes of the undamaged structures to impart damage-detection sensitivity to the neural networks. The inspections of an optical strain gauge mounting plate and an International Space Station cold plate are presented as examples.

  6. Tissue damage detection by osmotic surveillance

    PubMed Central

    Enyedi, Balázs; Kala, Snigdha; Nikolich-Zugich, Tijana; Niethammer, Philipp

    2013-01-01

    How tissue damage is detected to induce inflammatory responses is unclear. Most studies have focused on damage signals released by cell breakage and necrosis1. Whether tissues utilize other cues besides cell lysis to detect that they are damaged is unknown. We find that osmolarity differences between interstitial fluid and the external environment mediate rapid leukocyte recruitment to sites of tissue damage in zebrafish by activating cytosolic phospholipase a2 (cPLA2) at injury sites. cPLA2 initiates the production of non-canonical arachidonate metabolites that mediate leukocyte chemotaxis via a 5-oxo-ETE receptor (OXE-R). Thus, tissues can detect damage through direct surveillance of barrier integrity. By this mechanism, cell-swelling likely functions as a pro-inflammatory intermediate. PMID:23934216

  7. Tissue damage detection by osmotic surveillance.

    PubMed

    Enyedi, Balázs; Kala, Snigdha; Nikolich-Zugich, Tijana; Niethammer, Philipp

    2013-09-01

    How tissue damage is detected to induce inflammatory responses is unclear. Most studies have focused on damage signals released by cell breakage and necrosis. Whether tissues use other cues in addition to cell lysis to detect that they are damaged is unknown. We find that osmolarity differences between interstitial fluid and the external environment mediate rapid leukocyte recruitment to sites of tissue damage in zebrafish by activating cytosolic phospholipase a2 (cPLA2) at injury sites. cPLA2 initiates the production of non-canonical arachidonate metabolites that mediate leukocyte chemotaxis through a 5-oxo-ETE receptor (OXE-R). Thus, tissues can detect damage through direct surveillance of barrier integrity, with cell swelling probably functioning as a pro-inflammatory intermediate in the process. PMID:23934216

  8. Development of the Non-Destructive Evaluation System Using an Eddy Current Probe for Detection of Fatigue Damage in a Stainless Steel

    SciTech Connect

    Oka, M.; Yakushiji, T.; Tsuchida, Y.; Enokizono, M.

    2006-03-06

    The non-destructive evaluation system which is developed using an eddy current probe to evaluate fatigue damage in an austenitic stainless steel is reported in this paper. This probe is composed of the ferrite core and two pick-up coils connected differentially. The eddy current induced by the excitation coil is disarranged by nonuniform distribution of electromagnetic characteristics due to fatigue damage. The structural function of the eddy current probe proposed, enable to detect the eddy current disarrangement by fatigue damage. This probe detects the change of electromagnetic characteristics in the direction of X. In this paper, SUS304, a austenitic stainless steel was used as the sample. The experimental results show that the output voltage of the probe clearly depends on the number of stress cycles.

  9. Damage detection in mechanical structures using extreme value statistic.

    SciTech Connect

    Worden, K.; Allen, D. W.; Sohn, H.; Farrar, C. R.

    2002-01-01

    The first and most important objective of any damage identification algorithms is to ascertain with confidence if damage is present or not. Many methods have been proposed for damage detection based on ideas of novelty detection founded in pattern recognition and multivariate statistics. The philosophy of novelty detection is simple. Features are first extracted from a baseline system to be monitored, and subsequent data are then compared to see if the new features are outliers, which significantly depart from the rest of population. In damage diagnosis problems, the assumption is that outliers are generated from a damaged condition of the monitored system. This damage classification necessitates the establishment of a decision boundary. Choosing this threshold value is often based on the assumption that the parent distribution of data is Gaussian in nature. While the problem of novelty detection focuses attention on the outlier or extreme values of the data i.e. those points in the tails of the distribution, the threshold selection using the normality assumption weighs the central population of data. Therefore, this normality assumption might impose potentially misleading behavior on damage classification, and is likely to lead the damage diagnosis astray. In this paper, extreme value statistics is integrated with the novelty detection to specifically model the tails of the distribution of interest. Finally, the proposed technique is demonstrated on simulated numerical data and time series data measured from an eight degree-of-freedom spring-mass system.

  10. Damage detection of an in-service condensation pipeline joint

    NASA Astrophysics Data System (ADS)

    Briand, Julie; Rezaei, Davood; Taheri, Farid

    2010-04-01

    The early detection of damage in structural or mechanical systems is of vital importance. With early detection, the damage may be repaired before the integrity of the system is jeopardized, resulting in monetary losses, loss of life or limb, and environmental impacts. Among the various types of structural health monitoring techniques, vibration-based methods are of significant interest since the damage location does not need to be known beforehand, making it a more versatile approach. The non-destructive damage detection method used for the experiments herein is a novel vibration-based method which uses an index called the EMD Energy Damage Index, developed with the aim of providing improved qualitative results compared to those methods currently available. As part of an effort to establish the integrity and limitation of this novel damage detection method, field testing was completed on a mechanical pipe joint on a condensation line, located in the physical plant of Dalhousie University. Piezoceramic sensors, placed at various locations around the joint were used to monitor the free vibration of the pipe imposed through the use of an impulse hammer. Multiple damage progression scenarios were completed, each having a healthy state and multiple damage cases. Subsequently, the recorded signals from the healthy and damaged joint were processed through the EMD Energy Damage Index developed in-house in an effort to detect the inflicted damage. The proposed methodology successfully detected the inflicted damages. In this paper, the effects of impact location, sensor location, frequency bandwidth, intrinsic mode functions, and boundary conditions are discussed.

  11. Ozone damage detection in cantaloupe plants

    NASA Technical Reports Server (NTRS)

    Gausman, H. W.; Escobar, D. E.; Rodriguez, R. R.; Thomas, C. E.; Bowen, R. L.

    1978-01-01

    Ozone causes up to 90 percent of air pollution injury to vegetation in the United States; excess ozone affects plant growth and development and can cause undetected decrease in yields. Laboratory and field reflectance measurements showed that ozone-damaged cantaloupe (Cucumis melo L.) leaves had lower water contents and higher reflectance than did nondamaged leaves. Cantaloupe plants which were lightly, severely, and very severely ozone-damaged were distinguishable from nondamaged plants by reflectance measurements in the 1.35- to 2.5 micron near-infrared water absorption waveband. Ozone-damaged leaf areas were detected photographically 16 h before the damage was visible. Sensors are available for use with aircraft and spacecraft that possibly could be used routinely to detect ozone-damaged crops.

  12. Spiral Bevel Gear Damage Detection Using Decision Fusion Analysis

    NASA Technical Reports Server (NTRS)

    Dempsey, Paula J.; Handschuh, Robert F.; Afjeh, Abdollah A.

    2002-01-01

    A diagnostic tool for detecting damage to spiral bevel gears was developed. Two different monitoring technologies, oil debris analysis and vibration, were integrated using data fusion into a health monitoring system for detecting surface fatigue pitting damage on gears. This integrated system showed improved detection and decision-making capabilities as compared to using individual monitoring technologies. This diagnostic tool was evaluated by collecting vibration and oil debris data from fatigue tests performed in the NASA Glenn Spiral Bevel Gear Fatigue Rigs. Data was collected during experiments performed in this test rig when pitting damage occurred. Results show that combining the vibration and oil debris measurement technologies improves the detection of pitting damage on spiral bevel gears.

  13. Wireless Damage Location Sensing System

    NASA Technical Reports Server (NTRS)

    Woodard, Stanley E. (Inventor); Taylor, Bryant Douglas (Inventor)

    2012-01-01

    A wireless damage location sensing system uses a geometric-patterned wireless sensor that resonates in the presence of a time-varying magnetic field to generate a harmonic response that will experience a change when the sensor experiences a change in its geometric pattern. The sensing system also includes a magnetic field response recorder for wirelessly transmitting the time-varying magnetic field and for wirelessly detecting the harmonic response. The sensing system compares the actual harmonic response to a plurality of predetermined harmonic responses. Each predetermined harmonic response is associated with a severing of the sensor at a corresponding known location thereof so that a match between the actual harmonic response and one of the predetermined harmonic responses defines the known location of the severing that is associated therewith.

  14. Impact Damage Detection in Composite Plates using a Self-diagnostic Electro-Mechanical Impedance-based Structural Health Monitoring System

    NASA Astrophysics Data System (ADS)

    Sharif-Khodaei, Z.; Ghajari, M.; Aliabadi, M. H.

    2015-03-01

    In this work, application of the electro-mechanical impedance (EMI) method in structural health monitoring as a damage detection technique has been investigated. A damage metric based on the real and imaginary parts of the impedance measures is introduced. Numerical and experimental tests are carried out to investigate the applicability of the method for various types of damage, such as debonding between the transducers and the plate, faulty sensors and impact damage in composite plates. The effect of several parameters, such as environmental effects, frequency sweep, severity of damage, location of damage, etc., on the damage metric has been reported.

  15. Open Circuit Resonant Sensors for Composite Damage Detection and Diagnosis

    NASA Technical Reports Server (NTRS)

    Mielnik, John J., Jr.

    2011-01-01

    Under the Integrated Vehicle Health Management (IVHM) program work was begun to investigate the feasibility of sensor systems for detecting and diagnosing damage to aircraft composite structures and materials. Specific interest for this study was in damage initiated by environmental storm hazards and the direct effect of lightning strikes on the material structures of a composite aircraft in flight. A series of open circuit resonant sensors was designed, fabricated, characterized, and determined to be a potentially viable means for damage detection and diagnosis of composite materials. The results of this research and development effort are documented in this report.

  16. Transmission Bearing Damage Detection Using Decision Fusion Analysis

    NASA Technical Reports Server (NTRS)

    Dempsey, Paula J.; Lewicki, David G.; Decker, Harry J.

    2004-01-01

    A diagnostic tool was developed for detecting fatigue damage to rolling element bearings in an OH-58 main rotor transmission. Two different monitoring technologies, oil debris analysis and vibration, were integrated using data fusion into a health monitoring system for detecting bearing surface fatigue pitting damage. This integrated system showed improved detection and decision-making capabilities as compared to using individual monitoring technologies. This diagnostic tool was evaluated by collecting vibration and oil debris data from tests performed in the NASA Glenn 500 hp Helicopter Transmission Test Stand. Data was collected during experiments performed in this test rig when two unanticipated bearing failures occurred. Results show that combining the vibration and oil debris measurement technologies improves the detection of pitting damage on spiral bevel gears duplex ball bearings and spiral bevel pinion triplex ball bearings in a main rotor transmission.

  17. Prototype Systems Containing Human Cytochrome P450 for High-Throughput Real-Time Detection of DNA Damage by Compounds That Form DNA-Reactive Metabolites.

    PubMed

    Brito Palma, Bernardo; Fisher, Charles W; Rueff, José; Kranendonk, Michel

    2016-05-16

    The formation of reactive metabolites through biotransformation is the suspected cause of many adverse drug reactions. Testing for the propensity of a drug to form reactive metabolites has increasingly become an integral part of lead-optimization strategy in drug discovery. DNA reactivity is one undesirable facet of a drug or its metabolites and can lead to increased risk of cancer and reproductive toxicity. Many drugs are metabolized by cytochromes P450 in the liver and other tissues, and these reactions can generate hard electrophiles. These hard electrophilic reactive metabolites may react with DNA and may be detected in standard in vitro genotoxicity assays; however, the majority of these assays fall short due to the use of animal-derived organ extracts that inadequately represent human metabolism. The current study describes the development of bacterial systems that efficiently detect DNA-damaging electrophilic reactive metabolites generated by human P450 biotransformation. These assays use a GFP reporter system that detects DNA damage through induction of the SOS response and a GFP reporter to control for cytotoxicity. Two human CYP1A2-competent prototypes presented here have appropriate characteristics for the detection of DNA-damaging reactive metabolites in a high-throughput manner. The advantages of this approach include a short assay time (120-180 min) with real-time measurement, sensitivity to small amounts of compound, and adaptability to a microplate format. These systems are suitable for high-throughput assays and can serve as prototypes for the development of future enhanced versions. PMID:27031942

  18. A Robust Damage Assessment Model for Corrupted Database Systems

    NASA Astrophysics Data System (ADS)

    Fu, Ge; Zhu, Hong; Li, Yingjiu

    An intrusion tolerant database uses damage assessment techniques to detect damage propagation scales in a corrupted database system. Traditional damage assessment approaches in a intrusion tolerant database system can only locate damages which are caused by reading corrupted data. In fact, there are many other damage spreading patterns that have not been considered in traditional damage assessment model. In this paper, we systematically analyze inter-transaction dependency relationships that have been neglected in the previous research and propose four different dependency relationships between transactions which may cause damage propagation. We extend existing damage assessment model based on the four novel dependency relationships. The essential properties of our model is also discussed.

  19. Damage Detection in Electrically Conductive Structures

    NASA Astrophysics Data System (ADS)

    Anderson, Todd A.

    2002-12-01

    High-technology systems are in need of structures that perform with increased functionality and a reduction in weight, while simultaneously maintaining a high level of performance and reliability. To accomplish this, structural elements must be designed more efficiently and with increased functionality, thereby creating multifunctional structures (MFS). Through the addition of carbon fibers, nanotubes, or particles, composite structures can be made electrically conductive while simultaneously increasing their strength and stiffness to weight ratios. Using the electrical properties of these structures for the purpose of damage detection and location for health and usage monitoring is of particular interest for aerospace structures. One such method for doing this is Electrical Impedance Tomography (EIT). With EIT, an electric current is applied through a pair of electrodes and the electric potential is recorded at other monitoring electrodes around the area of study. An inverse solution of the governing Maxwell equations is then required to determine the conductivities of discrete areas within the region of interest. However, this method is nearly ill-posed and computationally intensive as it focuses on imaging small changes in conductivity within the region of interest. For locating damage in a medium with an otherwise homogeneous conductivity, an alternative approach is to search for parameters such as the damage location and size. Towards those ends, this study develops an Artificial Neural Network (ANN) to determine the state of an electrically conductive region based on applied reference current and electrical potentials at electrodes around the periphery of the region. A significant benefit of the ANN approach is that once trained, the solution of an inverse problem does not require costly computations of the inverse problem. This method also takes advantage of the pattern recognition abilities of neural networks and is a robust solution method in the presence

  20. Detecting Tooth Damage in Geared Drive Trains

    NASA Technical Reports Server (NTRS)

    Nachtsheim, Philip R.

    1997-01-01

    This paper describes a method that was developed to detect gear tooth damage that does not require a priori knowledge of the frequency characteristic of the fault. The basic idea of the method is that a few damaged teeth will cause transient load fluctuations unlike the normal tooth load fluctuations. The method attempts to measure the energy in the lower side bands of the modulated signal caused by the transient load fluctuations. The method monitors the energy in the frequency interval which excludes the frequency of the lowest dominant normal tooth load fluctuation and all frequencies above it. The method reacted significantly to the tooth fracture damage results documented in the Lewis data sets which were obtained from tests of the OH-58A transmission and tests of high contact ratio spiral bevel gears. The method detected gear tooth fractures in all four of the high contact ratio spiral bevel gear runs. Published results indicate other detection methods were only able to detect faults for three out of four runs.

  1. Earthquake damage to transportation systems

    USGS Publications Warehouse

    McCullough, Heather

    1994-01-01

    Earthquakes represent one of the most destructive natural hazards known to man. A large magnitude earthquake near a populated area can affect residents over thousands of square kilometers and cause billions of dollars in property damage. Such an event can kill or injure thousands of residents and disrupt the socioeconomic environment for months, sometimes years. A serious result of a large-magnitude earthquake is the disruption of transportation systems, which limits post-disaster emergency response. Movement of emergency vehicles, such as police cars, fire trucks and ambulances, is often severely restricted. Damage to transportation systems is categorized below by cause including: ground failure, faulting, vibration damage, and tsunamis.

  2. In-flight fiber optic acoustic emission sensor (FAESense) system for the real time detection, localization, and classification of damage in composite aircraft structures

    NASA Astrophysics Data System (ADS)

    Mendoza, Edgar; Prohaska, John; Kempen, Connie; Esterkin, Yan; Sun, Sunjian

    2013-05-01

    Acoustic emission sensing is a leading structural health monitoring technique use for the early warning detection of structural damage associated with impacts, cracks, fracture, and delaminations in advanced materials. Current AE systems based on electronic PZT transducers suffer from various limitations that prevent its wide dynamic use in practical avionics and aerospace applications where weight, size and power are critical for operation. This paper describes progress towards the development of a wireless in-flight distributed fiber optic acoustic emission monitoring system (FAESense™) suitable for the onboard-unattended detection, localization, and classification of damage in avionics and aerospace structures. Fiber optic AE sensors offer significant advantages over its counterpart electronic AE sensors by using a high-density array of micron-size AE transducers distributed and multiplex over long lengths of a standard single mode optical fiber. Immediate SHM applications are found in commercial and military aircraft, helicopters, spacecraft, wind mil turbine blades, and in next generation weapon systems, as well as in the petrochemical and aerospace industries, civil structures, power utilities, and a wide spectrum of other applications.

  3. Spiral-Bevel-Gear Damage Detected Using Decision Fusion Analysis

    NASA Technical Reports Server (NTRS)

    Dempsey, Paula J.; Handschuh, Robert F.

    2003-01-01

    Helicopter transmission integrity is critical to helicopter safety because helicopters depend on the power train for propulsion, lift, and flight maneuvering. To detect impending transmission failures, the ideal diagnostic tools used in the health-monitoring system would provide real-time health monitoring of the transmission, demonstrate a high level of reliable detection to minimize false alarms, and provide end users with clear information on the health of the system without requiring them to interpret large amounts of sensor data. A diagnostic tool for detecting damage to spiral bevel gears was developed. (Spiral bevel gears are used in helicopter transmissions to transfer power between nonparallel intersecting shafts.) Data fusion was used to integrate two different monitoring technologies, oil debris analysis and vibration, into a health-monitoring system for detecting surface fatigue pitting damage on the gears.

  4. Capacitance-based damage detection sensing for aerospace structural composites

    NASA Astrophysics Data System (ADS)

    Bahrami, P.; Yamamoto, N.; Chen, Y.; Manohara, H.

    2014-04-01

    Damage detection technology needs improvement for aerospace engineering application because detection within complex composite structures is difficult yet critical to avoid catastrophic failure. Damage detection is challenging in aerospace structures because not all the damage detection technology can cover the various defect types (delamination, fiber fracture, matrix crack etc.), or conditions (visibility, crack length size, etc.). These defect states are expected to become even more complex with future introduction of novel composites including nano-/microparticle reinforcement. Currently, non-destructive evaluation (NDE) methods with X-ray, ultrasound, or eddy current have good resolutions (< 0.1 mm), but their detection capabilities is limited by defect locations and orientations and require massive inspection devices. System health monitoring (SHM) methods are often paired with NDE technologies to signal out sensed damage, but their data collection and analysis currently requires excessive wiring and complex signal analysis. Here, we present a capacitance sensor-based, structural defect detection technology with improved sensing capability. Thin dielectric polymer layer is integrated as part of the structure; the defect in the structure directly alters the sensing layer's capacitance, allowing full-coverage sensing capability independent of defect size, orientation or location. In this work, capacitance-based sensing capability was experimentally demonstrated with a 2D sensing layer consisting of a dielectric layer sandwiched by electrodes. These sensing layers were applied on substrate surfaces. Surface indentation damage (~1mm diameter) and its location were detected through measured capacitance changes: 1 to 250 % depending on the substrates. The damage detection sensors are light weight, and they can be conformably coated and can be part of the composite structure. Therefore it is suitable for aerospace structures such as cryogenic tanks and rocket

  5. Damage detection using frequency shift path

    NASA Astrophysics Data System (ADS)

    Wang, Longqi; Lie, Seng Tjhen; Zhang, Yao

    2016-01-01

    This paper introduces a novel concept called FREquency Shift (FRESH) path to describe the dynamic behavior of structures with auxiliary mass. FRESH path combines the effects of frequency shifting and amplitude changing into one space curve, providing a tool for analyzing structure health status and properties. A damage index called FRESH curvature is then proposed to detect local stiffness reduction. FRESH curvature can be easily adapted for a particular problem since the sensitivity of the index can be adjusted by changing auxiliary mass or excitation power. An algorithm is proposed to adjust automatically the contribution from frequency and amplitude in the method. Because the extraction of FRESH path requires highly accurate frequency and amplitude estimators; therefore, a procedure based on discrete time Fourier transform is introduced to extract accurate frequency and amplitude with the time complexity of O (n log n), which is verified by simulation signals. Moreover, numerical examples with different damage sizes, severities and damping are presented to demonstrate the validity of the proposed damage index. In addition, applications of FRESH path on two steel beams with different damages are presented and the results show that the proposed method is valid and computational efficient.

  6. Damage modeling and damage detection for structures using a perturbation method

    NASA Astrophysics Data System (ADS)

    Dixit, Akash

    non-contact Laser-Doppler Vibrometer sensors. Assuming the damaged structure to be a linear system, the response is expressed as the summation of the responses of the corresponding undamaged structure and the response (negative response) of the damage alone. If the second part of the response is isolated, it forms what can be regarded as the damage signature. The damage signature gives a clear indication of the damage. In this thesis, the existence of the damage signature is investigated when the damaged structure is excited at one of its natural frequencies and therefore it is called "partial mode contribution". The second damage detection method is based on this new physical parameter as determined using the partial mode contribution. The physical reasoning is verified analytically, thereupon it is verified using finite element models and experiments. The limits of damage size that can be determined using the method are also investigated. There is no requirement of having a baseline data with this damage detection method. Since the partial mode contribution is a local parameter, it is thus very sensitive to the presence of damage. The parameter is also shown to be not affected by noise in the detection ambience.

  7. Experimental system identification of the dynamics of a vibro-impact beam with a view towards structural health monitoring and damage detection

    NASA Astrophysics Data System (ADS)

    Chen, Heng; Kurt, Mehmet; Lee, Young S.; McFarland, D. Michael; Bergman, Lawrence A.; Vakakis, Alexander F.

    2014-05-01

    We perform nonlinear system identification (NSI) on the acceleration signals that were experimentally measured at ten, almost evenly spaced positions along a cantilever beam undergoing vibro-impacts between two rigid stops with clearances. Our goal is to characterize the nonlinear dynamics due to vibro-impacts with a view toward structural health monitoring (SHM) and damage detection (DD). The NSI methodology is based on the correspondence between analytical and empirical slow-flow dynamics, with the first step requiring empirical mode decomposition (EMD) analysis of the measured time series leading to sets of intrinsic modal oscillators (IMOs) governing the vibro-impact dynamics at different time scales. By comparing the spatiotemporal variations of the nonlinear modal interactions (and hence the IMOs), we examine how vibro-impacts influence the low- and high-frequency modes in global and local senses. In applications of the NSI results to SHM/DD, we calculate typical measures such as the modal assurance criterion (MAC) and the coordinate modal assurance criterion (COMAC) by extracting information about the mode shape functions from the spatiotemporal IMO solutions. Whereas the MAC provides a global aspect of damage occurrence (i.e., which modes are more affected by induced defects), the COMAC can narrow down the damage locations (i.e., where in the structure defects exist that yield low correlation values in specific modes).

  8. Tapered Roller Bearing Damage Detection Using Decision Fusion Analysis

    NASA Technical Reports Server (NTRS)

    Dempsey, Paula J.; Kreider, Gary; Fichter, Thomas

    2006-01-01

    A diagnostic tool was developed for detecting fatigue damage of tapered roller bearings. Tapered roller bearings are used in helicopter transmissions and have potential for use in high bypass advanced gas turbine aircraft engines. A diagnostic tool was developed and evaluated experimentally by collecting oil debris data from failure progression tests conducted using health monitoring hardware. Failure progression tests were performed with tapered roller bearings under simulated engine load conditions. Tests were performed on one healthy bearing and three pre-damaged bearings. During each test, data from an on-line, in-line, inductance type oil debris sensor and three accelerometers were monitored and recorded for the occurrence of bearing failure. The bearing was removed and inspected periodically for damage progression throughout testing. Using data fusion techniques, two different monitoring technologies, oil debris analysis and vibration, were integrated into a health monitoring system for detecting bearing surface fatigue pitting damage. The data fusion diagnostic tool was evaluated during bearing failure progression tests under simulated engine load conditions. This integrated system showed improved detection of fatigue damage and health assessment of the tapered roller bearings as compared to using individual health monitoring technologies.

  9. Development of a Fish Cell Biosensor System for Genotoxicity Detection Based on DNA Damage-Induced Trans-Activation of p21 Gene Expression

    PubMed Central

    Geng, Deyu; Zhang, Zhixia; Guo, Huarong

    2012-01-01

    p21CIP1/WAF1 is a p53-target gene in response to cellular DNA damage. Here we report the development of a fish cell biosensor system for high throughput genotoxicity detection of new drugs, by stably integrating two reporter plasmids of pGL3-p21-luc (human p21 promoter linked to firefly luciferase) and pRL-CMV-luc (CMV promoter linked to Renilla luciferase) into marine flatfish flounder gill (FG) cells, referred to as p21FGLuc. Initial validation of this genotoxicity biosensor system showed that p21FGLuc cells had a wild-type p53 signaling pathway and responded positively to the challenge of both directly acting genotoxic agents (bleomycin and mitomycin C) and indirectly acting genotoxic agents (cyclophosphamide with metabolic activation), but negatively to cyclophosphamide without metabolic activation and the non-genotoxic agents ethanol and D-mannitol, thus confirming a high specificity and sensitivity, fast and stable response to genotoxic agents for this easily maintained fish cell biosensor system. This system was especially useful in the genotoxicity detection of Di(2-ethylhexyl) phthalate (DEHP), a rodent carcinogen, but negatively reported in most non-mammalian in vitro mutation assays, by providing a strong indication of genotoxicity for DEHP. A limitation for this biosensor system was that it might give false positive results in response to sodium butyrate and any other agents, which can trans-activate the p21 gene in a p53-independent manner. PMID:25585933

  10. A Comparison of Vibration and Oil Debris Gear Damage Detection Methods Applied to Pitting Damage

    NASA Technical Reports Server (NTRS)

    Dempsey, Paula J.

    2000-01-01

    Helicopter Health Usage Monitoring Systems (HUMS) must provide reliable, real-time performance monitoring of helicopter operating parameters to prevent damage of flight critical components. Helicopter transmission diagnostics are an important part of a helicopter HUMS. In order to improve the reliability of transmission diagnostics, many researchers propose combining two technologies, vibration and oil monitoring, using data fusion and intelligent systems. Some benefits of combining multiple sensors to make decisions include improved detection capabilities and increased probability the event is detected. However, if the sensors are inaccurate, or the features extracted from the sensors are poor predictors of transmission health, integration of these sensors will decrease the accuracy of damage prediction. For this reason, one must verify the individual integrity of vibration and oil analysis methods prior to integrating the two technologies. This research focuses on comparing the capability of two vibration algorithms, FM4 and NA4, and a commercially available on-line oil debris monitor to detect pitting damage on spur gears in the NASA Glenn Research Center Spur Gear Fatigue Test Rig. Results from this research indicate that the rate of change of debris mass measured by the oil debris monitor is comparable to the vibration algorithms in detecting gear pitting damage.

  11. Wavenumber Imaging For Damage Detection and Measurement

    NASA Technical Reports Server (NTRS)

    Rogge, Matthew D.; Johnson, Pat H.

    2011-01-01

    This paper presents a method for analyzing ultrasonic wavefield data using the Continuous Wavelet Transform (CWT) applied in the spatial domain. Unlike data obtained by sparse arrays of transducers, full wavefield data contains information local to the structure and can be used to obtain more detailed measurements of damage type, location, size, etc. By calculating the CWT of the wavefield in the spatial domain, the wavenumber spectrum is determined for the inspected locations. Because wavenumber is affected by the local geometry and material properties of the structure through which Lamb waves propagate, the wavenumber spectrum can be analyzed to assess the location, severity, and size of damage. The technique is first applied to experimental wavefield data obtained using a laser Doppler vibrometer and automated positioning stage. The out-of-plane velocity along the length of a composite stringer was measured to detect the presence of delaminations within the composite overwrap. Next, simulated corrosion is detected and measured within an aluminum plate using the two dimensional CWT. The experimental results show the usefulness of the technique for vehicle structure inspection applications.

  12. Damage assessment of the truss system with uncertainty using frequency response function based damage identification method

    NASA Astrophysics Data System (ADS)

    Zhao, Jie; DeSmidt, Hans; Yao, Wei

    2015-04-01

    A novel vibration-based damage identification methodology for the truss system with mass and stiffness uncertainties is proposed and demonstrated. This approach utilizes the damaged-induced changes of frequency response functions (FRF) to assess the severity and location of the structural damage in the system. The damage identification algorithm is developed basing on the least square and Newton-Raphson methods. The dynamical model of system is built using finite element method and Lagrange principle while the crack model is based on fracture mechanics. The method is synthesized via numerical examples for a truss system to demonstrate the effectiveness in detecting both stiffness and mass uncertainty existed in the system.

  13. Multi-stage identification scheme for detecting damage in structures under ambient excitations

    NASA Astrophysics Data System (ADS)

    Bao, Chunxiao; Hao, Hong; Li, Zhong-Xian

    2013-04-01

    Structural damage identification methods are critical to the successful application of structural health monitoring (SHM) systems to civil engineering structures. The dynamic response of civil engineering structures is usually characterized by high nonlinearity and non-stationarity. Accordingly, an improved Hilbert-Huang transform (HHT) method which is adaptive, output-only and applicable to system identification of in-service structures under ambient excitations is developed in this study. Based on this method, a multi-stage damage detection scheme including the detection of damage occurrence, damage existence, damage location and the estimation of damage severity is developed. In this scheme, the improved HHT method is used to analyse the structural acceleration response, the obtained instantaneous frequency detects the instant of damage occurrence, the instantaneous phase is sensitive to minor damage and provides reliable damage indication, and the damage indicator developed based on statistical analysis of the Hilbert marginal spectrum detects damage locations. Finally, the response sampled at the detected damage location is continuously analysed to estimate the damage severity. Numerical and experimental studies of frame structures under ambient excitations are performed. The results demonstrate that this scheme accomplishes the above damage detection functions within one flow. It is robust, time efficient, simply implemented and applicable to the real-time SHM of in-service structures.

  14. Acoustic Emission Beamforming for Detection and Localization of Damage

    NASA Astrophysics Data System (ADS)

    Rivey, Joshua Callen

    The aerospace industry is a constantly evolving field with corporate manufacturers continually utilizing innovative processes and materials. These materials include advanced metallics and composite systems. The exploration and implementation of new materials and structures has prompted the development of numerous structural health monitoring and nondestructive evaluation techniques for quality assurance purposes and pre- and in-service damage detection. Exploitation of acoustic emission sensors coupled with a beamforming technique provides the potential for creating an effective non-contact and non-invasive monitoring capability for assessing structural integrity. This investigation used an acoustic emission detection device that employs helical arrays of MEMS-based microphones around a high-definition optical camera to provide real-time non-contact monitoring of inspection specimens during testing. The study assessed the feasibility of the sound camera for use in structural health monitoring of composite specimens during tensile testing for detecting onset of damage in addition to nondestructive evaluation of aluminum inspection plates for visualizing stress wave propagation in structures. During composite material monitoring, the sound camera was able to accurately identify the onset and location of damage resulting from large amplitude acoustic feedback mechanisms such as fiber breakage. Damage resulting from smaller acoustic feedback events such as matrix failure was detected but not localized to the degree of accuracy of larger feedback events. Findings suggest that beamforming technology can provide effective non-contact and non-invasive inspection of composite materials, characterizing the onset and the location of damage in an efficient manner. With regards to the nondestructive evaluation of metallic plates, this remote sensing system allows us to record wave propagation events in situ via a single-shot measurement. This is a significant improvement over

  15. Vibration Monitoring Techniques Applied to Detect Damage in Rotating Disks

    NASA Technical Reports Server (NTRS)

    Gyekenyesi, Andrew L.; Sawicki, Jerzy T.

    2002-01-01

    Rotor health monitoring and online damage detection are increasingly gaining the interest of the manufacturers of aircraft engines. This is primarily due to the need for improved safety during operation as well as the need for lower maintenance costs. Applied techniques for detecting damage in and monitoring the health of rotors are essential for engine safety, reliability, and life prediction. The goals of engine safety are addressed within the NASA-sponsored Aviation Safety Program (AvSP). AvSP provides research and technology products needed to help the Federal Aviation Administration and the aerospace industry improve aviation safety. The Nondestructive Evaluation Group at the NASA Glenn Research Center is addressing propulsion health management and the development of propulsion-system-specific technologies intended to detect potential failures prior to catastrophe.

  16. Ultrasonic Techniques for Baseline-Free Damage Detection in Structures

    NASA Astrophysics Data System (ADS)

    Dutta, Debaditya

    This research presents ultrasonic techniques for baseline-free damage detection in structures in the context of structural health monitoring (SHM). Conventional SHM methods compare signals obtained from the pristine condition of a structure (baseline signals) with those from the current state, and relate certain changes in the signal characteristics to damage. While this approach has been successful in the laboratory, there are certain drawbacks of depending on baseline signals in real field applications. Data from the pristine condition are not available for most existing structures. Even if they are available, operational and environmental variations tend to mask the effect of damage on the signal characteristics. Most important, baseline measurements may become meaningless while assessing the condition of a structure after an extreme event such as an earthquake or a hurricane. Such events may destroy the sensors themselves and require installation of new sensors at different locations on the structure. Baseline-free structural damage detection can broaden the scope of SHM in the scenarios described above. A detailed discussion on the philosophy of baseline-free damage detection is provided in Chapter 1. Following this discussion, the research questions are formulated. The organization of this document and the major contributions of this research are also listed in this chapter. Chapter 2 describes a fully automated baseline-free technique for notch and crack detection in plates using a collocated pair of piezoelectric wafer transducers for measuring ultrasonic signals. Signal component corresponding to the damage induced mode-converted Lamb waves is extracted by processing the originally measured ultrasonic signals. The damage index is computed as a function of this mode-converted Lamb wave signal component. An over-determined system of Lamb wave measurements is used to find a least-square estimate of the measurement errors. This error estimate serves as the

  17. Underlying modal data issues for detecting damage in truss structures

    NASA Technical Reports Server (NTRS)

    Kashangaki, Thomas A-L.; Smith, Suzanne Weaver; Lim, Tae W.

    1992-01-01

    Independent of the modal identification techniques employed for damage detection, use of measured modal data limits the expectations for damage location. These limitations are examined using the distribution of modal strain energy and the sensitivity of the frequency and mode shapes to structural stiffness changes. For given measured modal information of specific accuracy, this examination reveals the following: (1) damage detection is feasible for members that contribute significantly to the strain energy of the measured modes, (2) the modes which are most effective in detecting damage to certain critical members can be identified, and (3) a relationship can be drawn between the accuracy of the measured modes and frequencies and damage detection feasibility.

  18. Semi-active control of isolated and damaged structures using online damage detection

    NASA Astrophysics Data System (ADS)

    Amini, Fereidoun; Mohajeri, Seyed Ahmad; Javanbakht, Majd

    2015-10-01

    The idea of using semi-active or active control devices within a base isolation system has been developed recently, since applying this system to building structures has some shortcomings such as the creation of large displacements at the base level and the system's lack of adaptability to different seismic excitations. In this study, an integrated structural health monitoring and semi-active control scheme is proposed to enhance the seismic behavior of damaged isolated structures. The nonlinear behavior of an isolated structure is limited to the isolator level and the superstructure is assumed to remain linear. Then, using an online damage detection algorithm based on identified system Markov parameters and a semi-active fuzzy controller, the damage in the base isolator is mitigated and the seismic response of the structure is reduced. In addition, a magnetorheological damper is utilized as a well-studied semi-active actuator in the control system. The effectiveness of the proposed control system is evaluated through the numerical study of a six-degrees-of-freedom model of base-isolated buildings excited by various near-fault and far-field earthquake records. The results of the simulation show that the integrated algorithm is substantially effective in improving the dynamic behavior of isolated structures and reducing the damage in the isolator.

  19. A local damage detection approach based on restoring force method

    NASA Astrophysics Data System (ADS)

    Zhan, Chao; Li, Dongsheng; Li, Hongnan

    2014-09-01

    Chain-like systems have been studied by many researchers for their simple structure and wide range of application. Previously, the damage in a chain-like system was detected by the reduction of the mass-normalized stiffness coefficient for certain elements as reported by Nayeri et al. (2008 [16]). However, some shortcomings exist in that approach and for overcoming them; an improved approach is derived and presented in this paper. In our improved approach, the mass normalized stiffness coefficients under two states (baseline state and potentially damaged state) are first estimated by a least square method, then these mass-stiffness coupled coefficients are decoupled to derive stiffness and mass relative change ratios for individual elements. These ratios are assembled in a vector, which is defined as damage indication vector (DIV). Each component in DIV is normalized individually to one to get multiple solutions. These solutions are averaged for estimating relative system changes, while abnormal solutions are discarded. The work of judging a solution as normal or abnormal is done by a cluster analysis algorithm. The most intriguing merit of this improved approach is that the relative stiffness and mass changes, which are coupled in the previous approach, can be separately identified. By this approach, the damage (single or multiple) extent and location can be correctly detected under operational conditions, meanwhile the proposed damage index has a clear physical meaning and is directly related to the stiffness reduction of corresponding structural elements. For illustrating the effectiveness and robustness of the improved approach, numerical simulation of a four floor building was carried out and experimental data from a structure tested at the Los Alamos National Laboratory was employed. Identified structural changes with both simulation and experimental data properly indicated the location and extent of actual structural damage, which validated the proposed

  20. Damage scenarios and an onboard support system for damaged ships

    NASA Astrophysics Data System (ADS)

    Choi, Jin; Lee, Dongkon; Kang, Hee Jin; Kim, Soo-Young; Shin, Sung-Chul

    2014-06-01

    Although a safety assessment of damaged ships, which considers environmental conditions such as waves and wind, is important in both the design and operation phases of ships, in Korea, rules or guidelines to conduct such assessments are not yet developed. However, NATO and European maritime societies have developed guidelines for a safety assessment. Therefore, it is required to develop rules or guidelines for safety assessments such as the Naval Ship Code (NSC) of NATO. Before the safety assessment of a damaged ship can be performed, the available damage scenarios must be developed and the safety assessment criteria must be established. In this paper, the parameters related to damage by accidents are identified and categorized when developing damage scenarios. The need for damage safety assessment criteria is discussed, and an example is presented. In addition, a concept and specifications for the DB-based supporting system, which is used in the operation phases, are proposed.

  1. A damage detection technique for reinforced concrete structures

    NASA Astrophysics Data System (ADS)

    Wu, Ai-Lun; Yang, Jann N.; Loh, Chin-Hsiung

    2012-04-01

    Civil engineering structures, such as reinforced concrete frames, exhibit nonlinear hysteretic behavior when subject to dynamic loads, such as earthquakes. The ability to detect damages in structures after a major earthquake will ensure their reliability and safety. Innovative analysis techniques for damage detection of structures have been extensively studied recently. However, practical and effective damage identification techniques remain to be developed for nonlinear structures, in particular hysteretic reinforced concrete (RC) structures. In this paper, a smooth hysteretic model with stiffness and strength degradations and with the pinching effect is used to represent the dynamic characteristics of reinforced concrete (RC) frames. A system identification method capable of detecting damages in nonlinear structures, referred to as the adaptive quadratic sum-square error with unknown inputs (AQSSE-UI), is used to detect damages in hysteretic RC frames. The performance of the AQSSE-UI technique is demonstrated by the experimental data. A 1/3 scale 2-story RC frame has been tested experimentally on the shake table at NCREE, Taiwan. This 2-story RC frame was subject to different levels of ground excitations back to back. The RC frame is firstly considered as a linear model with rotational springs and the tracking of the degradation of the stiffness parameters is carried out using the AQSSE-UI technique. Then the same RC frame is considered as a nonlinear structure with plastic hinges following a smooth hysteretic model. Experimental results show that the AQSSE-UI technique is quite effective for tracking of : (i) the stiffness degradation of linear structures, and (ii) the non-linear hysteretic parameters with stiffness and strength degradations.

  2. Impedance-based damage detection for civil infrastructures

    NASA Astrophysics Data System (ADS)

    Park, Seunghee; Roh, YongRae; Yi, JinHak; Yun, Chung-Bang; Kwak, Hyo-Gyoung; Lee, SangHan

    2004-07-01

    The objective of this study is to investigate the feasibility of an impedance-based damage detection technique using piezoelectric (PZT) transducers for civil infrastructures such as steel bridges. The basic concept of the technique is to monitor the changes in the electrical impedance to detect structural damages. Those changes in the electrical impedance are due to the electro-mechanical coupling property of piezoelectric materials. The smart PZT transducers which act as both actuators and sensors in a self-analyzing manner are emerging to be effective in non-parametric health monitoring of structural systems. This health monitoring technique can be easily adapted to existing structures, since only a small number of PZT patches are needed for continuous monitoring of their structural integrity. This impedance-based method operates at high frequencies (above 100 kHz), which enables it to detect incipient-type damage. It is not interfered by normal operating conditions, vibrations of the host structure, and changes in the host external body. The results of the experimental study on three kinds of structural members indicate that cracks or loosened bolts/nuts near the PZT sensors may be effectively detected by monitoring the shifts of the resonant frequencies of the impedance functions.

  3. Gear Damage Detection Using Oil Debris Analysis

    NASA Technical Reports Server (NTRS)

    Dempsey, Paula J.

    2001-01-01

    The purpose of this paper was to verify, when using an oil debris sensor, that accumulated mass predicts gear pitting damage and to identify a method to set threshold limits for damaged gears. Oil debris data was collected from 8 experiments with no damage and 8 with pitting damage in the NASA Glenn Spur Gear Fatigue Rig. Oil debris feature analysis was performed on this data. Video images of damage progression were also collected from 6 of the experiments with pitting damage. During each test, data from an oil debris sensor was monitored and recorded for the occurrence of pitting damage. The data measured from the oil debris sensor during experiments with damage and with no damage was used to identify membership functions to build a simple fuzzy logic model. Using fuzzy logic techniques and the oil debris data, threshold limits were defined that discriminate between stages of pitting wear. Results indicate accumulated mass combined with fuzzy logic analysis techniques is a good predictor of pitting damage on spur gears.

  4. Evaluation of the damage detection capability of a sparse-array guided-wave SHM system applied to a complex structure under varying thermal conditions.

    PubMed

    Clarke, Thomas; Cawley, Peter; Wilcox, Paul David; Croxford, Anthony John

    2009-12-01

    A sparse-array structural health monitoring (SHM) system based on guided waves was applied to the door of a commercial shipping container. The door comprised a corrugated steel panel approximately 2.4 m by 2.4 m surrounded by a box beam frame and testing was performed in a nonlaboratory environment. A 3-D finite element (FE) model of the corrugations was used to predict transmission coefficients for the A0 and S0 modes across the corrugations as a function of incidence angle. The S0 mode transmission across the corrugations was substantially stronger, and this mode was used in the main test series. A sparse array with 9 transducers was attached to the structure, and signals from the undamaged structure were recorded at periodic intervals over a 3-week period, and the resulting signal database was used for temperature compensation of subsequent signals. Defects in the form of holes whose diameter was increased incrementally from 1 to 10 mm were introduced at 2 different points of the structure, and signals were taken for each condition. Direct analysis of subtracted signals allowed understanding of the defect detection capability of the system. Comparison of signals transmitted between different transducer pairs before and after damage was used to give an initial indication of defect detectability. Signals from all combinations of transducers were then used in imaging algorithms, and good localization of holes with a 5-mm diameter or above was possible within the sparse array, which covered half of the area of the structure. PMID:20040403

  5. Image Science and Analysis Group Spacecraft Damage Detection/Characterization

    NASA Technical Reports Server (NTRS)

    Wheaton, Ira M., Jr.

    2010-01-01

    This project consisted of several tasks that could be served by an intern to assist the ISAG in detecting damage to spacecrafts during missions. First, this project focused on supporting the Micrometeoroid Orbital Debris (MMOD) damage detection and assessment for the Hubble Space Telescope (HST) using imagery from the last two HST Shuttle servicing missions. In this project, we used coordinates of two windows on the Shuttle Aft flight deck from where images were taken and the coordinates of three ID points in order to calculate the distance from each window to the three points. Then, using the specifications from the camera used, we calculated the image scale in pixels per inch for planes parallel to and planes in the z-direction to the image plane (shown in Table 1). This will help in the future for calculating measurements of objects in the images. Next, tabulation and statistical analysis were conducted for screening results (shown in Table 2) of imagery with Orion Thermal Protection System (TPS) damage. Using the Microsoft Excel CRITBINOM function and Goal Seek, the probabilities of detection of damage to different shuttle tiles were calculated as shown in Table 3. Using developed measuring tools, volume and area measurements will be created from 3D models of Orion TPS damage. Last, mathematical expertise was provided to the Photogrammetry Team. These mathematical tasks consisted of developing elegant image space error equations for observations along 3D lines, circles, planes, etc. and checking proofs for minimal sets of sufficient multi-linear constraints. Some of the processes and resulting equations are displayed in Figure 1.

  6. DNA damage may drive nucleosomal reorganization to facilitate damage detection

    NASA Astrophysics Data System (ADS)

    LeGresley, Sarah E.; Wilt, Jamie; Antonik, Matthew

    2014-03-01

    One issue in genome maintenance is how DNA repair proteins find lesions at rates that seem to exceed diffusion-limited search rates. We propose a phenomenon where DNA damage induces nucleosomal rearrangements which move lesions to potential rendezvous points in the chromatin structure. These rendezvous points are the dyad and the linker DNA between histones, positions in the chromatin which are more likely to be accessible by repair proteins engaged in a random search. The feasibility of this mechanism is tested by considering the statistical mechanics of DNA containing a single lesion wrapped onto the nucleosome. We consider lesions which make the DNA either more flexible or more rigid by modeling the lesion as either a decrease or an increase in the bending energy. We include this energy in a partition function model of nucleosome breathing. Our results indicate that the steady state for a breathing nucleosome will most likely position the lesion at the dyad or in the linker, depending on the energy of the lesion. A role for DNA binding proteins and chromatin remodelers is suggested based on their ability to alter the mechanical properties of the DNA and DNA-histone binding, respectively. We speculate that these positions around the nucleosome potentially serve as rendezvous points where DNA lesions may be encountered by repair proteins which may be sterically hindered from searching the rest of the nucleosomal DNA. The strength of the repositioning is strongly dependent on the structural details of the DNA lesion and the wrapping and breathing of the nucleosome. A more sophisticated evaluation of this proposed mechanism will require detailed information about breathing dynamics, the structure of partially wrapped nucleosomes, and the structural properties of damaged DNA.

  7. Quantitative phase imaging applied to laser damage detection and analysis.

    PubMed

    Douti, Dam-Bé L; Chrayteh, Mhamad; Aknoun, Sherazade; Doualle, Thomas; Hecquet, Christophe; Monneret, Serge; Gallais, Laurent

    2015-10-01

    We investigate phase imaging as a measurement method for laser damage detection and analysis of laser-induced modification of optical materials. Experiments have been conducted with a wavefront sensor based on lateral shearing interferometry associated with a high-magnification optical microscope. The system has been used for the in-line observation of optical thin films and bulk samples, laser irradiated in two different conditions: 500 fs pulses at 343 and 1030 nm, and millisecond to second irradiation with a CO2 laser at 10.6 μm. We investigate the measurement of the laser-induced damage threshold of optical material by detection and phase changes and show that the technique realizes high sensitivity with different optical path measurements lower than 1 nm. Additionally, the quantitative information on the refractive index or surface modification of the samples under test that is provided by the system has been compared to classical metrology instruments used for laser damage or laser ablation characterization (an atomic force microscope, a differential interference contrast microscope, and an optical surface profiler). An accurate in-line measurement of the morphology of laser-ablated sites, from few nanometers to hundred microns in depth, is shown. PMID:26479612

  8. Damage detection using the eigenparameter decomposition of substructural flexibility matrix

    NASA Astrophysics Data System (ADS)

    Weng, Shun; Zhu, Hong-Ping; Xia, Yong; Mao, Ling

    2013-01-01

    The crack or local damage on a structure reduces the stiffness of the structure, and thus leads to the modification of the dynamic properties. Damage detection is widely performed by comparing the initial modal data of the intact structure with those of the damaged structure. For a large-scale structure, the local damage usually introduces slight change to the global modal data, which makes the local damage difficult to be detected. This paper proposes a new substructuring method for the damage detection of a structure. The global structure is divided into manageable substructures. The modal data measured on the global structure are disassembled for obtaining the independent substructural dynamic flexibility matrices, under the force and displacement compatibility constraints. Thereafter, the substructural flexibility matrix is decomposed into its eigenvalues and eigenvectors to be used as the indicators for damage detection. Since the substructuring method concerns the local area by treating it as an independent structure, the substructural eigenparameters are more sensitive to the local damage than the global eigenparameters. The proposed substructuring method is firstly verified by a laboratory-tested portal frame structure. The location of the artificial cuts can be detected successfully by comparing the change of substructural eigenparameters. The proposed method is then applied to the 600 m tall Guangzhou New TV Tower. As compared with the global eigenparameters, the substructural eigenparameters bear larger changes caused by the local damage and thus are more sensitive to the local damage.

  9. Damage detection in bridges through fiber optic structural health monitoring

    NASA Astrophysics Data System (ADS)

    Doornink, J. D.; Phares, B. M.; Wipf, T. J.; Wood, D. L.

    2006-10-01

    A fiber optic structural health monitoring (SHM) system was developed and deployed by the Iowa State University (ISU) Bridge Engineering Center (BEC) to detect gradual or sudden damage in fracture-critical bridges (FCBs). The SHM system is trained with measured performance data, which are collected by fiber optic strain sensors to identify typical bridge behavior when subjected to ambient traffic loads. Structural responses deviating from the trained behavior are considered to be signs of structural damage or degradation and are identified through analytical procedures similar to control chart analyses used in statistical process control (SPC). The demonstration FCB SHM system was installed on the US Highway 30 bridge near Ames, IA, and utilizes 40 fiber bragg grating (FBG) sensors to continuously monitor the bridge response when subjected to ambient traffic loads. After the data is collected and processed, weekly evaluation reports are developed that summarize the continuous monitoring results. Through use of the evaluation reports, the bridge owner is able to identify and estimate the location and severity of the damage. The information presented herein includes an overview of the SHM components, results from laboratory and field validation testing on the system components, and samples of the reduced and analyzed data.

  10. Integrating Oil Debris and Vibration Gear Damage Detection Technologies Using Fuzzy Logic

    NASA Technical Reports Server (NTRS)

    Dempsey, Paula J.; Afjeh, Abdollah A.

    2002-01-01

    A diagnostic tool for detecting damage to spur gears was developed. Two different measurement technologies, wear debris analysis and vibration, were integrated into a health monitoring system for detecting surface fatigue pitting damage on gears. This integrated system showed improved detection and decision-making capabilities as compared to using individual measurement technologies. This diagnostic tool was developed and evaluated experimentally by collecting vibration and oil debris data from fatigue tests performed in the NASA Glenn Spur Gear Fatigue Test Rig. Experimental data were collected during experiments performed in this test rig with and without pitting. Results show combining the two measurement technologies improves the detection of pitting damage on spur gears.

  11. Application of Damage Detection Techniques Using Wind Turbine Modal Data

    SciTech Connect

    Gross, E.; Rumsey, M.; Simmermacher, T.; Zadoks, R.I.

    1998-12-17

    As any structure ages, its structural characteristics will also change. The goal of this work was to determine if modal response data fkom a wind turbine could be used in the detection of damage. The input stimuli to the wind turbine were from traditional modal hammer input and natural wind excitation. The structural response data was acquired using accelerometers mounted on the rotor of a parked and undamaged horizontal-axis wind turbine. The bolts at the root of one of the three blades were then loosened to simulate a damaged blade. The structural response data of the rotor was again recorded. The undamaged and damage-simulated datasets were compared using existing darnage detection algorithms. Also, a novel algorithm for combining the results of different damage detection algorithms was utilized in the assessment of the data. This paper summarizes the code development and discusses some preliminary damage detection results.

  12. Vibration Based Sun Gear Damage Detection

    NASA Technical Reports Server (NTRS)

    Hood, Adrian; LaBerge, Kelsen; Lewicki, David; Pines, Darryll

    2013-01-01

    Seeded fault experiments were conducted on the planetary stage of an OH-58C helicopter transmission. Two vibration based methods are discussed that isolate the dynamics of the sun gear from that of the planet gears, bearings, input spiral bevel stage, and other components in and around the gearbox. Three damaged sun gears: two spalled and one cracked, serve as the focus of this current work. A non-sequential vibration separation algorithm was developed and the resulting signals analyzed. The second method uses only the time synchronously averaged data but takes advantage of the signal/source mapping required for vibration separation. Both algorithms were successful in identifying the spall damage. Sun gear damage was confirmed by the presence of sun mesh groups. The sun tooth crack condition was inconclusive.

  13. DAMAGE DETECTION IN PLATE STRUCTURES USING MODAL POWER FLOW ANALYSIS

    SciTech Connect

    Liu, X.; Wong, W. O.; Cheng, L.

    2010-05-28

    The power flow and energy distribution of a vibration mode of a damaged plate is studied experimentally. Variation of the modal reactive power distribution of a damaged plate is experimentally evaluated with a scanning LDV and compared to the theoretical predictions. Large variation of local reactive power flow in or around the damage region of a plate under resonant vibration is found to be related to the change of strain and kinetic energies in the damage region. Feasibility of damage identification based on the detection of this local variation of modal reactive power flow in a structure is studied.

  14. Damage diagnosis algorithm using a sequential change point detection method with an unknown distribution for damage

    NASA Astrophysics Data System (ADS)

    Noh, Hae Young; Rajagopal, Ram; Kiremidjian, Anne S.

    2012-04-01

    This paper introduces a damage diagnosis algorithm for civil structures that uses a sequential change point detection method for the cases where the post-damage feature distribution is unknown a priori. This algorithm extracts features from structural vibration data using time-series analysis and then declares damage using the change point detection method. The change point detection method asymptotically minimizes detection delay for a given false alarm rate. The conventional method uses the known pre- and post-damage feature distributions to perform a sequential hypothesis test. In practice, however, the post-damage distribution is unlikely to be known a priori. Therefore, our algorithm estimates and updates this distribution as data are collected using the maximum likelihood and the Bayesian methods. We also applied an approximate method to reduce the computation load and memory requirement associated with the estimation. The algorithm is validated using multiple sets of simulated data and a set of experimental data collected from a four-story steel special moment-resisting frame. Our algorithm was able to estimate the post-damage distribution consistently and resulted in detection delays only a few seconds longer than the delays from the conventional method that assumes we know the post-damage feature distribution. We confirmed that the Bayesian method is particularly efficient in declaring damage with minimal memory requirement, but the maximum likelihood method provides an insightful heuristic approach.

  15. On damage detection in wind turbine gearboxes using outlier analysis

    NASA Astrophysics Data System (ADS)

    Antoniadou, Ifigeneia; Manson, Graeme; Dervilis, Nikolaos; Staszewski, Wieslaw J.; Worden, Keith

    2012-04-01

    The proportion of worldwide installed wind power in power systems increases over the years as a result of the steadily growing interest in renewable energy sources. Still, the advantages offered by the use of wind power are overshadowed by the high operational and maintenance costs, resulting in the low competitiveness of wind power in the energy market. In order to reduce the costs of corrective maintenance, the application of condition monitoring to gearboxes becomes highly important, since gearboxes are among the wind turbine components with the most frequent failure observations. While condition monitoring of gearboxes in general is common practice, with various methods having been developed over the last few decades, wind turbine gearbox condition monitoring faces a major challenge: the detection of faults under the time-varying load conditions prevailing in wind turbine systems. Classical time and frequency domain methods fail to detect faults under variable load conditions, due to the temporary effect that these faults have on vibration signals. This paper uses the statistical discipline of outlier analysis for the damage detection of gearbox tooth faults. A simplified two-degree-of-freedom gearbox model considering nonlinear backlash, time-periodic mesh stiffness and static transmission error, simulates the vibration signals to be analysed. Local stiffness reduction is used for the simulation of tooth faults and statistical processes determine the existence of intermittencies. The lowest level of fault detection, the threshold value, is considered and the Mahalanobis squared-distance is calculated for the novelty detection problem.

  16. Vibration-based damage detection algorithm for WTT structures

    NASA Astrophysics Data System (ADS)

    Nguyen, Tuan-Cuong; Kim, Tae-Hwan; Choi, Sang-Hoon; Ryu, Joo-Young; Kim, Jeong-Tae

    2016-04-01

    In this paper, the integrity of a wind turbine tower (WTT) structure is nondestructively estimated using its vibration responses. Firstly, a damage detection algorithm using changes in modal characteristics to predict damage locations and severities in structures is outlined. Secondly, a finite element (FE) model based on a real WTT structure is established by using a commercial software, Midas FEA. Thirdly, forced vibration tests are performed on the FE model of the WTT structure under various damage scenarios. The changes in modal parameters such as natural frequencies and mode shapes are examined for damage monitoring in the structure. Finally, the feasibility of the vibration-based damage detection method is numerically verified by predicting locations and severities of the damage in the FE model of the WTT structure.

  17. Vibration characteristics and damage detection in a suspension bridge

    NASA Astrophysics Data System (ADS)

    Wickramasinghe, Wasanthi R.; Thambiratnam, David P.; Chan, Tommy H. T.; Nguyen, Theanh

    2016-08-01

    Suspension bridges are flexible and vibration sensitive structures that exhibit complex and multi-modal vibration. Due to this, the usual vibration based methods could face a challenge when used for damage detection in these structures. This paper develops and applies a mode shape component specific damage index (DI) to detect and locate damage in a suspension bridge with pre-tensioned cables. This is important as suspension bridges are large structures and damage in them during their long service lives could easily go un-noticed. The capability of the proposed vibration based DI is demonstrated through its application to detect and locate single and multiple damages with varied locations and severity in the cables of the suspension bridge. The outcome of this research will enhance the safety and performance of these bridges which play an important role in the transport network.

  18. Guided wave damage detection with PZT-FBG sensing

    NASA Astrophysics Data System (ADS)

    Sun, Xiaoyi; Tian, Zhenhua; Lin, Bin; Yu, Lingyu

    2016-04-01

    This paper presents guided waves based damage detection by using a hybrid PZT actuator and optic fiber Bragg grating (FBG) sensors. In the hybrid sensing, a piezoelectric wafer (PZT) is used to generate incident guided waves based on the piezoelectric principle. Meanwhile, multiple fiber Bragg grating sensors (FBG) are adopted as receivers to measure the high-frequency small-strain guided waves base on the full width half maximum (FWHM) principle. If the inspected structure has damage such as hole, crack and notch, the incident guided waves will be reflected or scattered by the damage. Through multiple FBG sensors at different locations, the damage induced waves can be acquired and further processed for damage detection. In this research, two configurations are explored, the rosette and line arrangements of multiple sensors. The sensing and wave source localization on aluminum plate are demonstrated. The results show that wave source can be successfully detected by using both the FBG rosette and the FBG array.

  19. Damage detection and health monitoring of operational structures

    SciTech Connect

    James, G.; Mayes, R.; Carne, T.; Reese, G.

    1994-09-01

    Initial damage detection/health monitoring experiments have been performed on three different operational structures: a fracture critical bridge, a composite wind turbine blade, and an aging aircraft. An induced damage test was performed on the Rio Grande/I40 bridge before its demolition. The composite wind turbine test was fatgued to failure with periodic modal testing performed throughout the testing. The front fuselage of a DC-9 aircraft was used as the testbed for an induced damage test. These tests have yielded important insights into techniques for experimental damage detection on real structures. Additionally, the data are currently being used with current damage detection algorithms to further develop the numerical technology. State of the art testing technologies such as, high density modal testing, scanning laser vibrometry and natural excitation testing have also been utilized for these tests.

  20. Structural Damage Detection Using Slopes of Longitudinal Vibration Shapes

    DOE PAGESBeta

    Xu, W.; Zhu, W. D.; Smith, S. A.; Cao, M. S.

    2016-03-18

    While structural damage detection based on flexural vibration shapes, such as mode shapes and steady-state response shapes under harmonic excitation, has been well developed, little attention is paid to that based on longitudinal vibration shapes that also contain damage information. This study originally formulates a slope vibration shape for damage detection in bars using longitudinal vibration shapes. To enhance noise robustness of the method, a slope vibration shape is transformed to a multiscale slope vibration shape in a multiscale domain using wavelet transform, which has explicit physical implication, high damage sensitivity, and noise robustness. These advantages are demonstrated in numericalmore » cases of damaged bars, and results show that multiscale slope vibration shapes can be used for identifying and locating damage in a noisy environment. A three-dimensional (3D) scanning laser vibrometer is used to measure the longitudinal steady-state response shape of an aluminum bar with damage due to reduced cross-sectional dimensions under harmonic excitation, and results show that the method can successfully identify and locate the damage. Slopes of longitudinal vibration shapes are shown to be suitable for damage detection in bars and have potential for applications in noisy environments.« less

  1. Numerical simulation of damage detection using laser-generated ultrasound.

    PubMed

    Liu, Peipei; Nazirah, Ab Wahab; Sohn, Hoon

    2016-07-01

    Laser ultrasonic techniques have been widely investigated due to its high spatial resolution and capacity for remote and noncontact measurement. In this study, the laser induced ultrasonic wave on an aluminum plate is simulated, and a nonlinear feature is used to detect a micro crack introduced in the plate model. A multi-physics simulation is conducted and optimized considering the effect of thermal diffusion. A nonlinear feature, called Bhattacharyya Distance (BD), is calculated to show the crack-induced geometric difference among the state space attractors obtained from closely spaced measurement points near the crack. First, a 3D model is built, and its simulation result is compared with an experiment performed using a noncontact laser ultrasonic measurement system. Then, by creating a micro crack in the model, BD is extracted and the crack is successfully detected and visualized. Finally, the effects of BD parameters, such as embedding dimension and frequency band, on damage visualization are investigated. PMID:27079488

  2. Detection of distributed damage in concrete using transient stress waves

    NASA Astrophysics Data System (ADS)

    Kesner, Keith; Sansalone, Mary; Poston, Randall W.

    1998-03-01

    Distributed damage mechanisms, such as delayed ettringite formation (DEF) and alkali-silica reactivity (ASR) can cause cracking and premature deterioration of concrete structures. The focus of the authors' research has been to determine whether transient stress waves can be used for assessing the amount of damage present in plate-like concrete sections. Results obtained from numerical, laboratory, and field studies are presented. Finite element analyses were performed to study the effects caused by distributed damage on propagation stress waves. Laboratory studies involved the use of accelerated damage specimens for performing tests for detecting changes in physical properties over time, impact-echo tests, and neutron radiography to quantify the amount of cracking present in a specimen. A correlation was made between damage predictions obtained from impact-echo signals and the actual amount of cracking as determined from radiographs. A field study on concrete box beams suffering deterioration caused by distributed damage mechanisms was performed to demonstrate the feasibility of the methods for quantifying damage in actual concrete members. These studies demonstrated that impact-echo signals can be used to detect and quantify the amount of distributed damage in concrete sections. Guidelines for determining the amount of damage using impact-echo signals are presented. For the first time, engineers have a tool for assessing the amount of damage in concrete structures with distributed cracking.

  3. Damage Detection Using the Frequency-Response Curvature Method

    NASA Astrophysics Data System (ADS)

    SAMPAIO, R. P. C.; MAIA, N. M. M.; SILVA, J. M. M.

    1999-10-01

    Structural damage detection has gained increasing attention from the scientific community since unpredicted major hazards, most with human losses, have been reported. Aircraft crashes and the catastrophic bridge failures are some examples. Security and economy aspects are the important motivations for increasing research on structural health monitoring. Since damage alters the dynamic characteristics of a structure, namely its eigenproperties (natural frequencies, modal damping and modes of vibration), several techniques based on experimental modal analysis have been developed in recent years. A method that covers the four steps of the process of damage detection—existence, localization, extent and prediction—has not yet been recognized or reported. The frequency-response-function (FRF) curvature method encompasses the first three referred steps being based on only the measured data without the need for any modal identification. In this paper, the method is described theoretically and compared with two of the most referenced methods on literature. Numerically generated data, from a lumped-mass system, and experimental data, from a real bridge, are used for better illustration.

  4. Airframe structural damage detection: a non-linear structural surface intensity based technique.

    PubMed

    Semperlotti, Fabio; Conlon, Stephen C; Barnard, Andrew R

    2011-04-01

    The non-linear structural surface intensity (NSSI) based damage detection technique is extended to airframe applications. The selected test structure is an upper cabin airframe section from a UH-60 Blackhawk helicopter (Sikorsky Aircraft, Stratford, CT). Structural damage is simulated through an impact resonator device, designed to simulate the induced vibration effects typical of non-linear behaving damage. An experimental study is conducted to prove the applicability of NSSI on complex mechanical systems as well as to evaluate the minimum sensor and actuator requirements. The NSSI technique is shown to have high damage detection sensitivity, covering an extended substructure with a single sensing location. PMID:21476618

  5. Automatic Damage Detection for Sensitive Cultural Heritage Sites

    NASA Astrophysics Data System (ADS)

    Cerra, D.; Tian, J.; Lysandrou, V.; Plank, S.

    2016-06-01

    The intentional damages to local Cultural Heritage sites carried out in recent months by the Islamic State (IS) have received wide coverage from the media worldwide. Earth Observation data is an important tool to assess these damages in such non-accessible areas: If a fast response is desired, automated image processing techniques would be needed to speed up the analysis. This paper shows the first results of applying fast and robust change detection techniques to sensitive areas. A map highlighting potentially damaged buildings is derived, which could help experts at timely assessing the damages to the Cultural Heritage sites in the observed images.

  6. Chimeric Proteins to Detect DNA Damage and Mismatches

    SciTech Connect

    McCutchen-Maloney, S; Malfatti, M; Robbins, K M

    2002-01-14

    The goal of this project was to develop chimeric proteins composed of a DNA mismatch or damage binding protein and a nuclease, as well as methods to detect DNA mismatches and damage. We accomplished this through protein engineering based on using polymerase chain reactions (PCRs) to create chimeras with novel functions for damage and mismatch detection. This project addressed fundamental questions relating to disease susceptibility and radiation-induced damage in cells. It also supported and enhanced LLNL's competency in the emerging field of proteomics. In nature, DNA is constantly being subjected to damaging agents such as exposure to ultraviolet (UV) radiation and various environmental and dietary carcinogens. If DNA damage is not repaired however, mutations in DNA result that can eventually manifest in cancer and other diseases. In addition to damage-induced DNA mutations, single nucleotide polymorphisms (SNPs), which are variations in the genetic sequence between individuals, may predispose some to disease. As a result of the Human Genome Project, the integrity of a person's DNA can now be monitored. Therefore, methods to detect DNA damage, mutations, and SNPs are useful not only in basic research but also in the health and biotechnology industries. Current methods of detection often use radioactive labeling and rely on expensive instrumentation that is not readily available in many research settings. Our methods to detect DNA damage and mismatches employ simple gel electrophoresis and flow cytometry, thereby alleviating the need for radioactive labeling and expensive equipment. In FY2001, we explored SNP detection by developing methods based on the ability of the chimeric proteins to detect mismatches. Using multiplex assays with flow cytometry and fluorescent beads to which the DNA substrates where attached, we showed that several of the chimeras possess greater affinity for damaged and mismatched DNA than for native DNA. This affinity was demonstrated in

  7. DEVELOPMENT OF NONLINEAR HARMONIC SENSORS FOR DETECTION OF MECHANICAL DAMAGE

    SciTech Connect

    Alfred E. Crouch; Alan Dean; Carl Torres; Jeff Aron

    2004-03-01

    In a joint effort with Tuboscope Pipeline Services of Houston, Texas, Southwest Research Institute (SwRI) adapted its nonlinear harmonic (NLH) sensing technology for use on a new in-line inspection system (smart pig). Nonlinear harmonics, an AC magnetic method for detecting local anomalies of stress and plastic deformation, shows promise of improved characterization of mechanical damage defects such as gouged dents, even though the dents may have re-rounded. The SwRI-Tuboscope project produced a sensor design, electronic design, and sensor suspension design that are directly adaptable to a multitechnology ILI system. This report describes the NLH method, the sensor, circuit, and suspension designs, and shows results from the supporting laboratory work.

  8. Sequential damage detection based on the continuous wavelet transform

    NASA Astrophysics Data System (ADS)

    Liao, Yizheng; Balafas, Konstantinos; Rajagopal, Ram; Kiremidjian, Anne S.

    2015-03-01

    This paper presents a sequential structural damage detection algorithm that is based on a statistical model for the wavelet transform of the structural responses. The detector uses the coefficients of the wavelet model and does not require prior knowledge of the structural properties. Principal Component Analysis is applied to select and extract the most sensitive features from the wavelet coefficients as the damage sensitive features. The damage detection algorithm is validated using the simulation data collected from a four-story steel moment frame. Various features have been explored and the detection algorithm was able to identify damage. Additionally, we show that for a desired probability of false alarm, the proposed detector is asymptotically optimal on the expected delay.

  9. Nonlinear damage identification of breathing cracks in Truss system

    NASA Astrophysics Data System (ADS)

    Zhao, Jie; DeSmidt, Hans

    2014-03-01

    The breathing cracks in truss system are detected by Frequency Response Function (FRF) based damage identification method. This method utilizes damage-induced changes of frequency response functions to estimate the severity and location of structural damage. This approach enables the possibility of arbitrary interrogation frequency and multiple inputs/outputs which greatly enrich the dataset for damage identification. The dynamical model of truss system is built using the finite element method and the crack model is based on fracture mechanics. Since the crack is driven by tensional and compressive forces of truss member, only one damage parameter is needed to represent the stiffness reduction of each truss member. Assuming that the crack constantly breathes with the exciting frequency, the linear damage detection algorithm is developed in frequency/time domain using Least Square and Newton Raphson methods. Then, the dynamic response of the truss system with breathing cracks is simulated in the time domain and meanwhile the crack breathing status for each member is determined by the feedback from real-time displacements of member's nodes. Harmonic Fourier Coefficients (HFCs) of dynamical response are computed by processing the data through convolution and moving average filters. Finally, the results show the effectiveness of linear damage detection algorithm in identifying the nonlinear breathing cracks using different combinations of HFCs and sensors.

  10. Damage detection in concrete using Lamb waves

    NASA Astrophysics Data System (ADS)

    Jung, Young-Chul; Na, Won-Bae; Kundu, Tribikram; Ehsani, Mohammad R.

    2000-06-01

    The feasibility of detecting defects in concrete beams using Lamb waves is investigated in this paper. The Lamb wave can propagate a long distance along the specimen as the guided wave and is sensitive to defects that are smaller than its wavelength. The traditional ultrasonic methods for inspecting defects in concrete use reflection, transmission and scattering of longitudinal waves by internal defects. In traditional techniques signal amplitude and time of flight measurements provide information about the internal defects in concrete. These methods are time consuming and often fail to detect a variety of defects, such as internal corrosion, honeycombs, closed cracks and small inclusions. In this paper Lamb waves are used to detect those defects in concrete beams with and without reinforcement. The Lamb wave technique is found to be reliable for detecting such defects. The effect of separation or delamination between concrete and reinforcing steel bars on the Lamb wave propagation characteristics is also investigated. Corrosion of rebars can cause this delamination. It is found that the cylindrical guided waves propagating along the steel rebars are very sensitive to the degree of delamination between the concrete and the rebars. This investigation shows that the Lamb wave inspection technique is an efficient and effective tool for health monitoring of concrete structures.

  11. Acoustic Emission Detection of Impact Damage on Space Shuttle Structures

    NASA Technical Reports Server (NTRS)

    Prosser, William H.; Gorman, Michael R.; Madaras, Eric I.

    2004-01-01

    The loss of the Space Shuttle Columbia as a result of impact damage from foam debris during ascent has led NASA to investigate the feasibility of on-board impact detection technologies. AE sensing has been utilized to monitor a wide variety of impact conditions on Space Shuttle components ranging from insulating foam and ablator materials, and ice at ascent velocities to simulated hypervelocity micrometeoroid and orbital debris impacts. Impact testing has been performed on both reinforced carbon composite leading edge materials as well as Shuttle tile materials on representative aluminum wing structures. Results of these impact tests will be presented with a focus on the acoustic emission sensor responses to these impact conditions. These tests have demonstrated the potential of employing an on-board Shuttle impact detection system. We will describe the present plans for implementation of an initial, very low frequency acoustic impact sensing system using pre-existing flight qualified hardware. The details of an accompanying flight measurement system to assess the Shuttle s acoustic background noise environment as a function of frequency will be described. The background noise assessment is being performed to optimize the frequency range of sensing for a planned future upgrade to the initial impact sensing system.

  12. Detection and damage assessment of citrus tree losses with aerial color infrared photography /ACIR/

    NASA Technical Reports Server (NTRS)

    Blazquez, C. H.; Horn, F. W., Jr.; Edwards, G. J.

    1981-01-01

    Detection and disease damage assessment of citrus tree losses in a Florida citrus grove were made by establishing a registration (grove site location) coordinate system, developing a damage assessment system, and testing sequential aerial color infrared (ACIR) photography at the scale of 1 in. = 333 ft (2.5 cm = 100 m) during the winter, spring, and summer seasons of 1978 and spring of 1979. Spring photography was the easiest to photo interpret, showed the greatest differences between healthy and diseased trees, and had the least shadow and background interference for photo interpretation. Trees showing slight disease damage were detected in ACIR before they were found in ground surveys.

  13. Development of practical damage-mapping and inspection systems

    SciTech Connect

    Rainer, F.

    1998-08-19

    We have developed and are continuing to refine semi-automated technology for the detection and inspection of surface and bulk defects and damage in large laser optics Different manifestations of the DAMOCLES system (Damage and Artifact Mapping Of Coherent-Laser-Exposed Substrates) provide an effective and economical means of being able to detect, map and characterize surface and bulk defects which may become precursors of massive damage in optics when subjected to high-fluence laser irradiation Subsequent morphology and evolution of damage due to laser irradiation can be tracked efficiently The strength of the Damocles system is that it allows for immediate visual observation of defects in an entire optic, which can range up to l-meter dimensions, while also being able to provide digital map and magnified images of the defects with resolutions better than 5 µm.

  14. Damage detection in turbine wind blades by vibration based methods

    NASA Astrophysics Data System (ADS)

    Doliński, L.; Krawczuk, M.

    2009-08-01

    The paper describes results of numerical simulation for damage localization in the composite coat of a wind turbine blade using modal parameters and a modern damage detection method (wavelet transform). The presented results were obtained in the first period of research on the diagnostic method, which is aimed at detecting damage in the blades of large wind turbines during normal operation. A blade-modelling process including the geometry, loads and failures has been introduced in the paper. A series of simulations has been carried out for different localizations and size of damage for finding the method's limits. To verify the results of numeric simulations a subscale blade has been built which has geometric features and mechanical properties similar to the computer model.

  15. Direct Detection and Sequencing of Damaged DNA Bases

    PubMed Central

    2011-01-01

    Products of various forms of DNA damage have been implicated in a variety of important biological processes, such as aging, neurodegenerative diseases, and cancer. Therefore, there exists great interest to develop methods for interrogating damaged DNA in the context of sequencing. Here, we demonstrate that single-molecule, real-time (SMRT®) DNA sequencing can directly detect damaged DNA bases in the DNA template - as a by-product of the sequencing method - through an analysis of the DNA polymerase kinetics that are altered by the presence of a modified base. We demonstrate the sequencing of several DNA templates containing products of DNA damage, including 8-oxoguanine, 8-oxoadenine, O6-methylguanine, 1-methyladenine, O4-methylthymine, 5-hydroxycytosine, 5-hydroxyuracil, 5-hydroxymethyluracil, or thymine dimers, and show that these base modifications can be readily detected with single-modification resolution and DNA strand specificity. We characterize the distinct kinetic signatures generated by these DNA base modifications. PMID:22185597

  16. Study on an auto-correlation-function-based damage index: Sensitivity analysis and structural damage detection

    NASA Astrophysics Data System (ADS)

    Zhang, Muyu; Schmidt, Rüdiger

    2015-12-01

    The damage index based on the auto correlation function to detect the damage of the structure under white noise excitation is studied in detail in this paper. The maximum values of the auto correlation function of the vibration response signals (displacement, velocity and acceleration) from different measurement points of the structure are collected and formulated as a vector called Auto Correlation Function at Maximum Point Value Vector (AMV), which is expressed as a weighted combination of the Hadamard product of two mode shapes. AMV is normalized by its root mean square value so that the influence of the excitation can be eliminated. Sensitivity analysis for the different parts of the normalized AMV shows that the sensitivity of the normalized AMV to the local stiffness is dependent most on the sensitivity of the Hadamard product of the two lower order mode shapes to the local stiffness, which has a sudden change of the value around the local stiffness change position. The sensitivity of the normalized AMV has the similar shape and same trend that shows it is a very good damage indicator even for the very small damage. The relative change of the normalized AMV before and after damage occurs in the structure is adopted as the damage index to show the damage location. Several examples of the stiffness reduction detection of a 12-story shear frame structure are utilized to validate the results in sensitivity analysis, illustrate the effectiveness and anti-noise ability of the AMV-based damage detection method and compare the effect of the response type on the detectability of the normalized AMV.

  17. Rapid detection and quantification of impact damage in composite structures

    NASA Technical Reports Server (NTRS)

    Smith, Barry T.

    1992-01-01

    It is shown that a multidisciplinary nondestructive evaluation approach for impact damage detection in composite structures can be used to produce a more efficient inspection. The multidisciplinary NDE approach relies on fast large area thermographic inspections along with detailed ultrasonic volumetric imaging. The thermal inspection technique rapidly identifies the impact damage. The ultrasonic volumetric imaging quantifies the impact generated delaminations through the volume of the structure.

  18. Rapid detection and quantification of impact damage in composite structures

    NASA Technical Reports Server (NTRS)

    Zalameda, Joseph N.; Farley, Gary; Smith, Barry T.

    1991-01-01

    NDE results from thermographic and volumetric ultrasonic techniques are presented to illustrate the multidisciplinary NDE approach to impact-damage detection in such composite structures as are increasingly prevalent in helicopters. Attention is given to both flat-panel and 'y-stiffened' panel specimens; these were fabricated either with kevlar or carbon fiber through-the-thickness reinforcements. While thermal inspection identifies impact damage, volumetric imaging quantifies the impact-generated delaminations through the volume of the structure.

  19. Detecting damage in steel with scanning SQUID microscopy

    SciTech Connect

    Lee, Tae-Kyu; Clatterbuck, David; Morris Jr., J.W.; Shaw, T.J.; McDermott R.; Clarke, John

    2001-09-04

    A ''Holy Grail'' of NDE research is a non-destructive method for measuring fatigue damage prior to crack initiation. High-Tc scanning SQUID microscopy may be a useful tool. Because of the exceptional magnetic sensitivity of this technique, fatigue damage can be detected well before microcrack initiation, and in the absence of other obvious microstructure or property changes. Given the spatial resolution of the technique, undamaged material can be located and used to set internal standards.

  20. Info-gap robustness of an input signal optimization algorithm for damage detection

    NASA Astrophysics Data System (ADS)

    Pasquali, M.; Stull, C. J.; Farrar, C. R.

    2015-01-01

    Info-Gap Decision Theory is adopted to assess the robustness of a technique aimed at identifying the optimal excitation signal to be used for active sensing approaches to damage detection. Here the term "active sensing" refers to procedures where a known input is applied to the structure to enhance the damage detection process. Given limited system response measurements and ever-present physical limits on the level of excitation, the ultimate goal of the mentioned technique is to improve the detectability of damage by increasing the difference between measured outputs of the undamaged and damaged systems. In particular, a two degree-of-freedom mass-spring-damper system characterized by the presence of a nonlinear stiffness is considered. Uncertainty is introduced to the system in the form of deviations of its parameters (mass, stiffness, damping ratio) from their nominal values. Variations in the performance of the mentioned technique are then evaluated both in terms of changes in the estimated difference between the responses of the damaged and undamaged systems and in terms of deviations of the identified optimal input signal from its nominal estimation. Finally, plots of the performances of the analyzed algorithm for different levels of uncertainty are obtained, enabling a clear evaluation of the risks connected with designing excitation signals for damage detection, when the parameters that dictate system behavior (e.g. stiffness, mass) are poorly characterized or improperly modeled.

  1. Damage Detection Response Characteristics of Open Circuit Resonant (SansEC) Sensors

    NASA Technical Reports Server (NTRS)

    Dudley, Kenneth L.; Szatkowski, George N.; Smith, Laura J.; Koppen, Sandra V.; Ely, Jay J.; Nguyen, Truong X.; Wang, Chuantong; Ticatch, Larry A.; Mielnik, John J.

    2013-01-01

    The capability to assess the current or future state of the health of an aircraft to improve safety, availability, and reliability while reducing maintenance costs has been a continuous goal for decades. Many companies, commercial entities, and academic institutions have become interested in Integrated Vehicle Health Management (IVHM) and a growing effort of research into "smart" vehicle sensing systems has emerged. Methods to detect damage to aircraft materials and structures have historically relied on visual inspection during pre-flight or post-flight operations by flight and ground crews. More quantitative non-destructive investigations with various instruments and sensors have traditionally been performed when the aircraft is out of operational service during major scheduled maintenance. Through the use of reliable sensors coupled with data monitoring, data mining, and data analysis techniques, the health state of a vehicle can be detected in-situ. NASA Langley Research Center (LaRC) is developing a composite aircraft skin damage detection method and system based on open circuit SansEC (Sans Electric Connection) sensor technology. Composite materials are increasingly used in modern aircraft for reducing weight, improving fuel efficiency, and enhancing the overall design, performance, and manufacturability of airborne vehicles. Materials such as fiberglass reinforced composites (FRC) and carbon-fiber-reinforced polymers (CFRP) are being used to great advantage in airframes, wings, engine nacelles, turbine blades, fairings, fuselage structures, empennage structures, control surfaces and aircraft skins. SansEC sensor technology is a new technical framework for designing, powering, and interrogating sensors to detect various types of damage in composite materials. The source cause of the in-service damage (lightning strike, impact damage, material fatigue, etc.) to the aircraft composite is not relevant. The sensor will detect damage independent of the cause

  2. Damage Detection of Structures Identified with Deterministic-Stochastic Models Using Seismic Data

    PubMed Central

    Huang, Ming-Chih; Wang, Yen-Po; Chang, Ming-Lian

    2014-01-01

    A deterministic-stochastic subspace identification method is adopted and experimentally verified in this study to identify the equivalent single-input-multiple-output system parameters of the discrete-time state equation. The method of damage locating vector (DLV) is then considered for damage detection. A series of shaking table tests using a five-storey steel frame has been conducted. Both single and multiple damage conditions at various locations have been considered. In the system identification analysis, either full or partial observation conditions have been taken into account. It has been shown that the damaged stories can be identified from global responses of the structure to earthquakes if sufficiently observed. In addition to detecting damage(s) with respect to the intact structure, identification of new or extended damages of the as-damaged counterpart has also been studied. This study gives further insights into the scheme in terms of effectiveness, robustness, and limitation for damage localization of frame systems. PMID:25165749

  3. Damage detection of structures identified with deterministic-stochastic models using seismic data.

    PubMed

    Huang, Ming-Chih; Wang, Yen-Po; Chang, Ming-Lian

    2014-01-01

    A deterministic-stochastic subspace identification method is adopted and experimentally verified in this study to identify the equivalent single-input-multiple-output system parameters of the discrete-time state equation. The method of damage locating vector (DLV) is then considered for damage detection. A series of shaking table tests using a five-storey steel frame has been conducted. Both single and multiple damage conditions at various locations have been considered. In the system identification analysis, either full or partial observation conditions have been taken into account. It has been shown that the damaged stories can be identified from global responses of the structure to earthquakes if sufficiently observed. In addition to detecting damage(s) with respect to the intact structure, identification of new or extended damages of the as-damaged counterpart has also been studied. This study gives further insights into the scheme in terms of effectiveness, robustness, and limitation for damage localization of frame systems. PMID:25165749

  4. Non-Harmonic Fourier Analysis for bladed wheels damage detection

    NASA Astrophysics Data System (ADS)

    Neri, P.; Peeters, B.

    2015-11-01

    The interaction between bladed wheels and the fluid distributed by the stator vanes results in cyclic loading of the rotating components. Compressors and turbines wheels are subject to vibration and fatigue issues, especially when resonance conditions are excited. Even if resonance conditions can be often predicted and avoided, high cycle fatigue failures can occur, causing safety issues and economic loss. Rigorous maintenance programs are then needed, forcing the system to expensive shut-down. Blade crack detection methods are beneficial for condition-based maintenance. While contact measurement systems are not always usable in exercise conditions (e.g. high temperature), non-contact methods can be more suitable. One (or more) stator-fixed sensor can measure all the blades as they pass by, in order to detect the damaged ones. The main drawback in this situation is the short acquisition time available for each blade, which is shortened by the high rotational speed of the components. A traditional Discrete Fourier Transform (DFT) analysis would result in a poor frequency resolution. A Non-Harmonic Fourier Analysis (NHFA) can be executed with an arbitrary frequency resolution instead, allowing to obtain frequency information even with short-time data samples. This paper shows an analytical investigation of the NHFA method. A data processing algorithm is then proposed to obtain frequency shift information from short time samples. The performances of this algorithm are then studied by experimental and numerical tests.

  5. The use of strain gauges in vibration-based damage detection

    NASA Astrophysics Data System (ADS)

    Marques dos Santos, Fabio Luis; Peeters, Bart; Lau, Jenny; Desmet, Wim; Sandoval Goes, Luiz Carlos

    2015-07-01

    Strain gauges and strain measurements have been widely used in structural health monitoring (SHM) systems as a means of detecting and localizing damage, due to their higher sensitivity to local damage. These damage identification techniques normally use strain related measurements such as the mode curvature, strain frequency response function or strain energy as the main parameter to detect damage. However, damage detection techniques based on acceleration measurements have also been investigated in the past, using modal parameter comparison and other methodologies. In this paper, the use of vibration-based strain measurements for use in SHM systems will be evaluated, with the purpose of characterizing their higher sensitivity in damage detection, when compared to other vibration measurements, such as acceleration-based measurements. Since the choice and use of the most damage sensitive parameter can lead to a more sensitive and robust system, the assessment of the more suitable sensor and processing of information is very important. For this purpose, numerical and experimental examples will be discussed to evaluate the higher performance of the strain gauges.

  6. Laser-based structural sensing and surface damage detection

    NASA Astrophysics Data System (ADS)

    Guldur, Burcu

    Damage due to age or accumulated damage from hazards on existing structures poses a worldwide problem. In order to evaluate the current status of aging, deteriorating and damaged structures, it is vital to accurately assess the present conditions. It is possible to capture the in situ condition of structures by using laser scanners that create dense three-dimensional point clouds. This research investigates the use of high resolution three-dimensional terrestrial laser scanners with image capturing abilities as tools to capture geometric range data of complex scenes for structural engineering applications. Laser scanning technology is continuously improving, with commonly available scanners now capturing over 1,000,000 texture-mapped points per second with an accuracy of ~2 mm. However, automatically extracting meaningful information from point clouds remains a challenge, and the current state-of-the-art requires significant user interaction. The first objective of this research is to use widely accepted point cloud processing steps such as registration, feature extraction, segmentation, surface fitting and object detection to divide laser scanner data into meaningful object clusters and then apply several damage detection methods to these clusters. This required establishing a process for extracting important information from raw laser-scanned data sets such as the location, orientation and size of objects in a scanned region, and location of damaged regions on a structure. For this purpose, first a methodology for processing range data to identify objects in a scene is presented and then, once the objects from model library are correctly detected and fitted into the captured point cloud, these fitted objects are compared with the as-is point cloud of the investigated object to locate defects on the structure. The algorithms are demonstrated on synthetic scenes and validated on range data collected from test specimens and test-bed bridges. The second objective of

  7. Machine learning algorithms for damage detection: Kernel-based approaches

    NASA Astrophysics Data System (ADS)

    Santos, Adam; Figueiredo, Eloi; Silva, M. F. M.; Sales, C. S.; Costa, J. C. W. A.

    2016-02-01

    This paper presents four kernel-based algorithms for damage detection under varying operational and environmental conditions, namely based on one-class support vector machine, support vector data description, kernel principal component analysis and greedy kernel principal component analysis. Acceleration time-series from an array of accelerometers were obtained from a laboratory structure and used for performance comparison. The main contribution of this study is the applicability of the proposed algorithms for damage detection as well as the comparison of the classification performance between these algorithms and other four ones already considered as reliable approaches in the literature. All proposed algorithms revealed to have better classification performance than the previous ones.

  8. Polarimetric sensors for damage detection of aluminum materials

    NASA Astrophysics Data System (ADS)

    Chang, Wee M.; Ng, Poh K.; Sng, Su-fern S.; Ma, Jianjun; Asundi, Anand K.; Puttappa, Jayanth

    2001-06-01

    A PFOS for monitoring and detecting damages in aluminum specimen has been demonstrated. It has been shown that PFOS can be used to monitor the development of cracks and predict residual load on aluminum structures. The experimental result obtained is very consistent and the sensor is immune to temperature changes and electromagnetic interference, as it does not require a reference are more accurate for damage detection. Some of the features such as low cost, durable, light weight and real-time applications of PFOS have been highlighted.

  9. Optical components damage parameters database system

    NASA Astrophysics Data System (ADS)

    Tao, Yizheng; Li, Xinglan; Jin, Yuquan; Xie, Dongmei; Tang, Dingyong

    2012-10-01

    Optical component is the key to large-scale laser device developed by one of its load capacity is directly related to the device output capacity indicators, load capacity depends on many factors. Through the optical components will damage parameters database load capacity factors of various digital, information technology, for the load capacity of optical components to provide a scientific basis for data support; use of business processes and model-driven approach, the establishment of component damage parameter information model and database systems, system application results that meet the injury test optical components business processes and data management requirements of damage parameters, component parameters of flexible, configurable system is simple, easy to use, improve the efficiency of the optical component damage test.

  10. Detection of Damaged DNA Bases by DNA Glycosylase Enzymes†

    PubMed Central

    Friedman, Joshua I.; Stivers, James T.

    2010-01-01

    A fundamental and shared process in all forms of life is the use of DNA glycosylase enzymes to excise rare damaged bases from genomic DNA. Without such enzymes, the highly-ordered primary sequences of genes would rapidly deteriorate. Recent structural and biophysical studies are beginning to reveal a fascinating multistep mechanism for damaged base detection that begins with short-range sliding of the glycosylase along the DNA chain in a distinct conformation we refer to as the search complex (SC). Sliding is frequently punctuated by the formation of a transient “interrogation” complex (IC) where the enzyme extrahelically inspects both normal and damaged bases in an exosite pocket that is distant from the active site. When normal bases are presented in the exosite, the IC rapidly collapses back to the SC, while a damaged base will efficiently partition forward into the active site to form the catalytically competent excision complex (EC). Here we review the unique problems associated with enzymatic detection of rare damaged DNA bases in the genome, and emphasize how each complex must have specific dynamic properties that are tuned to optimize the rate and efficiency of damage site location. PMID:20469926

  11. Detection of Ca2+-dependent acid phosphatase activity identifies neuronal integrity in damaged rat central nervous system after application of bacterial melanin

    PubMed Central

    Petrosyan, Tigran R.; Ter-Markosyan, Anna S.; Hovsepyan, Anna S.

    2016-01-01

    The study aims to confirm the neuroregenerative effects of bacterial melanin (BM) on central nervous system injury using a special staining method based on the detection of Ca2+-dependent acid phosphatase activity. Twenty-four rats were randomly assigned to undergo either unilateral destruction of sensorimotor cortex (group I; n = 12) or unilateral rubrospinal tract transection at the cervical level (C3–4) (group II; n = 12). In each group, six rats were randomly selected after surgery to undergo intramuscular injection of BM solution (BM subgroup) and the remaining six rats were intramuscularly injected with saline (saline subgroup). Neurological testing confirmed that BM accelerated the recovery of motor function in rats from both BM and saline subgroups. Two months after surgery, Ca2+-dependent acid phosphatase activity detection in combination with Chilingarian’s calcium adenoside triphosphate method revealed that BM stimulated the sprouting of fibers and dilated the capillaries in the brain and spinal cord. These results suggest that BM can promote the recovery of motor function of rats with central nervous system injury; and detection of Ca2+-dependent acid phosphatase activity is a fast and easy method used to study the regeneration-promoting effects of BM on the injured central nervous system.

  12. Application of Hilbert-Huang transformation for detection of damage in concrete

    NASA Astrophysics Data System (ADS)

    Wu, Hwai-Chung; Pai, P. Frank; Warnemuende, Kraig

    2007-04-01

    Several nondestructive testing methods can be used to estimate the extent of damage in a concrete structure. Pulse-velocity and amplitude attenuation methods are very common in nondestructive ultrasonic evaluation. Velocity of propagation is not very sensitive to the degree of damage unless a great deal of micro-damages have evolved into localized macro-damages. The amplitude attenuation method is potentially more sensitive to damage than the pulse-velocity method. However, this method depends strongly on the coupling conditions between the transducers and the concrete and hence is unreliable. In a previous study, a new active modulation approach, Nonlinear Active Wave Modulation Spectroscopy, was developed and found promising for early detection of damage in concrete. In this procedure, a probe wave is passed through the system in a fashion similar to regular acoustic methods for inspection. Simultaneously, a second, low-frequency modulating wave is applied to the system to effectively change the size and stiffness of flaws microscopically and cyclically, thereby causing the frequency modulation to change cyclically as well. The resulting amplified modulations can be correlated to the extent of damage and quantification of small damage becomes possible. In this paper, we present the use of Hilbert-Huang transform to significantly enhance the damage detection sensitivity of this modulation method by performing time-frequency decomposition of nonlinear non-stationary time-domain responses.

  13. Nonlinear damage detection in composite structures using bispectral analysis

    NASA Astrophysics Data System (ADS)

    Ciampa, Francesco; Pickering, Simon; Scarselli, Gennaro; Meo, Michele

    2014-03-01

    Literature offers a quantitative number of diagnostic methods that can continuously provide detailed information of the material defects and damages in aerospace and civil engineering applications. Indeed, low velocity impact damages can considerably degrade the integrity of structural components and, if not detected, they can result in catastrophic failure conditions. This paper presents a nonlinear Structural Health Monitoring (SHM) method, based on ultrasonic guided waves (GW), for the detection of the nonlinear signature in a damaged composite structure. The proposed technique, based on a bispectral analysis of ultrasonic input waveforms, allows for the evaluation of the nonlinear response due to the presence of cracks and delaminations. Indeed, such a methodology was used to characterize the nonlinear behaviour of the structure, by exploiting the frequency mixing of the original waveform acquired from a sparse array of sensors. The robustness of bispectral analysis was experimentally demonstrated on a damaged carbon fibre reinforce plastic (CFRP) composite panel, and the nonlinear source was retrieved with a high level of accuracy. Unlike other linear and nonlinear ultrasonic methods for damage detection, this methodology does not require any baseline with the undamaged structure for the evaluation of the nonlinear source, nor a priori knowledge of the mechanical properties of the specimen. Moreover, bispectral analysis can be considered as a nonlinear elastic wave spectroscopy (NEWS) technique for materials showing either classical or non-classical nonlinear behaviour.

  14. Portable modular detection system

    DOEpatents

    Brennan, James S.; Singh, Anup; Throckmorton, Daniel J.; Stamps, James F.

    2009-10-13

    Disclosed herein are portable and modular detection devices and systems for detecting electromagnetic radiation, such as fluorescence, from an analyte which comprises at least one optical element removably attached to at least one alignment rail. Also disclosed are modular detection devices and systems having an integrated lock-in amplifier and spatial filter and assay methods using the portable and modular detection devices.

  15. Detecting Damage in Ceramic Matrix Composites Using Electrical Resistance

    NASA Technical Reports Server (NTRS)

    Smith, Craig E.; Gyekenyesi, Andrew

    2011-01-01

    The majority of damage in SiC/SiC ceramic matrix composites subjected to monotonic tensile loads is in the form of distributed matrix cracks. These cracks initiate near stress concentrations, such as 90 deg fiber tows or large matrix pores and continue to accumulate with additional stress until matrix crack saturation is achieved. Such damage is difficult to detect with conventional nondestructive evaluation techniques (immersion ultrasonics, x-ray, etc.). Monitoring a specimen.s electrical resistance change provides an indirect approach for monitoring matrix crack density. Sylramic-iBN fiber- reinforced SiC composites with a melt infiltrated (MI) matrix were tensile tested at room temperature. Results showed an increase in resistance of more than 500% prior to fracture, which can be detected either in situ or post-damage. A relationship between resistance change and matrix crack density was also determined.

  16. Lightning detection network averts damage and speeds restoration

    SciTech Connect

    Bernstein, R.; Samm, R.; Cummins, K.; Pyle, R.; Tuel, J.

    1996-04-01

    This article describes new tools to track thunderstorms for advance warning, enabling utilities to reduce damage and shorten repair time. Based on an extensive survey of US power utilities, lightning is the single largest cause of outages on distribution and transmission systems in lightning prone areas. But now with the aid of a network of electromagnetic sensors, computer systems, and satellite communications, the National Lightning Detection Network{trademark} (NLDN) helps utilities prepare for storms. Utilities in the path of intense lightning storms can prepare for storms, alert repair crews, and arrange for help from neighboring utilities. Real-time lightning data has been shown to reduce maintenance costs by shortening the thunder-storm-watch period and to improve reliability by allowing prepositioning of repair crews. Also, using line failure history, designers can analyze the lightning and line historical data and prioritize line upgrades to protect them from future storms by employing additional protection. Documented evidence available from the NLDN system helps utilities prove the time and location of lightning strikes, quickly resolving insurance claims. This network is a product of two EPRI research projects (RP3669 and RP2741).

  17. Structural damage detection based on the reconstructed phase space for reinforced concrete slab: Experimental study

    NASA Astrophysics Data System (ADS)

    Nie, Zhenhua; Hao, Hong; Ma, Hongwei

    2013-02-01

    In this paper, a parameter based on geometry changes of the reconstructed multidimensional phase space of the measured vibration signals for structural damage identification is proposed. The choice of the proper delay time steps and embedding dimensions for phase space reconstruction of linear systems is discussed. Using the determined delay time and embedding dimensions, an index Changes of Phase Space Topology (CPST) with multiple embedding dimensions is calculated and then used to identify the structural damage. To demonstrate the reliability of the proposed method, vibration test data corresponding to different damage states of a continuous reinforced concrete slab is used to calculate the CPST value for damage identification. The results indicate that except the measurement points at structural supports, the CPST values at all the measurement points on the structure increase with structural damage level irrespective of the damage location, indicating that using a single or a minimum number of measurement points and their CPST value can effectively identify damage existence in the structure. The traditional modal-based indices are also calculated using the same vibration data for comparison. It is found that the proposed method with CPST is the most sensitive to structural damage than any modal-based index. The results demonstrate that the proposed method with CPST value is very effective in identifying damage existence in the structure. Although it cannot quantify the damage, it can be a good candidate for continuous structural health monitoring because it needs only a few sensors to detect damage existence in the entire structure.

  18. Gas Flow Detection System

    NASA Technical Reports Server (NTRS)

    Moss, Thomas; Ihlefeld, Curtis; Slack, Barry

    2010-01-01

    This system provides a portable means to detect gas flow through a thin-walled tube without breaking into the tubing system. The flow detection system was specifically designed to detect flow through two parallel branches of a manifold with only one inlet and outlet, and is a means for verifying a space shuttle program requirement that saves time and reduces the risk of flight hardware damage compared to the current means of requirement verification. The prototype Purge Vent and Drain Window Cavity Conditioning System (PVD WCCS) Flow Detection System consists of a heater and a temperature-sensing thermistor attached to a piece of Velcro to be attached to each branch of a WCCS manifold for the duration of the requirement verification test. The heaters and thermistors are connected to a shielded cable and then to an electronics enclosure, which contains the power supplies, relays, and circuit board to provide power, signal conditioning, and control. The electronics enclosure is then connected to a commercial data acquisition box to provide analog to digital conversion as well as digital control. This data acquisition box is then connected to a commercial laptop running a custom application created using National Instruments LabVIEW. The operation of the PVD WCCS Flow Detection System consists of first attaching a heater/thermistor assembly to each of the two branches of one manifold while there is no flow through the manifold. Next, the software application running on the laptop is used to turn on the heaters and to monitor the manifold branch temperatures. When the system has reached thermal equilibrium, the software application s graphical user interface (GUI) will indicate that the branch temperatures are stable. The operator can then physically open the flow control valve to initiate the test flow of gaseous nitrogen (GN2) through the manifold. Next, the software user interface will be monitored for stable temperature indications when the system is again at

  19. Damage Detection in Bridge Structure Using Vibration Data under Random Travelling Vehicle Loads

    NASA Astrophysics Data System (ADS)

    Loh, C. H.; Hung, T. Y.; Chen, S. F.; Hsu, W. T.

    2015-07-01

    Due to the random nature of the road excitation and the inherent uncertainties in bridge-vehicle system, damage identification of bridge structure through continuous monitoring under operating situation become a challenge problem. Methods for system identification and damage detection of a continuous two-span concrete bridge structure in time domain is presented using interaction forces from random moving vehicles as excitation. The signals recorded in different locations of the instrumented bridge are mixed with signals from different internal and external (road roughness) vibration sources. The damage structure is also modelled as the stiffness reduction in one of the beam element. For the purpose of system identification and damage detection three different output-only modal analysis techniques are proposed: The covariance-driven stochastic subspace identification (SSI-COV), the blind source separation algorithms (called Second Order Blind Identification) and the multivariate AR model. The advantages and disadvantages of the three algorithms are discussed. Finally, the null-space damage index, subspace damage indices and mode shape slope change are used to detect and locate the damage. The proposed approaches has been tested in simulation and proved to be effective for structural health monitoring.

  20. Automatic detection of impact damage in carbon fiber composites using active thermography

    NASA Astrophysics Data System (ADS)

    Usamentiaga, R.; Venegas, P.; Guerediaga, J.; Vega, L.; López, I.

    2013-05-01

    Accidental impacts can severely reduce the structural strength and stability of composite materials, which can lead to severe consequences due to the degradation of the mechanical properties of components designed to perform for decades. Because accidental impacts are difficult to avoid, robust and reliable inspection methods to detect impact damage are required. Many methods have been proposed recently. However, most of them require an experienced technician to analyze the data, which leads to a significant decrease in manufacturing productivity. This work proposes a method to automatically detect impact damage in carbon fiber composites using active thermography. The proposed system detects defects caused by impact damage in the infrared images without human intervention. Impact damage detection is performed using a robust method based on an active thermographic inspection. Thermographic data is preprocessed to improve signal-to-noise ratio and to remove non-uniform background caused by non-uniform heating. Then, peaks and edges are identified and clustered, and regions corresponding to impact damage are detected. The proposed procedure has been applied to three specimens that contain 6 and 12 plies, different types of cores, and damage caused by energies from 6 J to 50 J. All defects are detected correctly.

  1. Detection of damage in welded structure using experimental modal data

    NASA Astrophysics Data System (ADS)

    Abu Husain, N.; Ouyang, H.

    2011-07-01

    A typical automotive structure could contain thousands of spot weld joints that contribute significantly to the vehicle's structural stiffness and dynamic characteristics. However, some of these joints may be imperfect or even absent during the manufacturing process and they are also highly susceptible to damage due to operational and environmental conditions during the vehicle lifetime. Therefore, early detection and estimation of damage are important so necessary actions can be taken to avoid further problems. Changes in physical parameters due to existence of damage in a structure often leads to alteration of vibration modes; thus demonstrating the dependency between the vibration characteristics and the physical properties of structures. A sensitivity-based model updating method, performed using a combination of MATLAB and NASTRAN, has been selected for the purpose of this work. The updating procedure is regarded as parameter identification which aims to bring the numerical prediction to be as closely as possible to the measured natural frequencies and mode shapes data of the damaged structure in order to identify the damage parameters (characterised by the reductions in the Young's modulus of the weld patches to indicate the loss of material/stiffness at the damage region).

  2. Structural Damage Detection with Piezoelectric Wafer Active Sensors

    NASA Astrophysics Data System (ADS)

    Giurgiutiu, Victor

    2011-07-01

    Piezoelectric wafer active sensors (PWAS) are lightweight and inexpensive enablers for a large class of damage detection and structural health monitoring (SHM) applications. This paper starts with a brief review of PWAS physical principles and basic modelling and continues by considering the various ways in which PWAS can be used for damage detection: (a) embedded guided-wave ultrasonics, i.e., pitch-catch, pulse-echo, phased arrays, thickness mode; (b) high-frequency modal sensing, i.e., the electro-mechanical (E/M) impedance method; (c) passive detection, i.e., acoustic emission and impact detection. An example of crack-like damage detection and localization with PWAS phased arrays on a small metallic plate is given. The modelling of PWAS detection of disbond damage in adhesive joints is achieved with the analytical transfer matrix method (TMM). The analytical methods offer the advantage of fast computation which enables parameter studies and carpet plots. A parametric study of the effect of crack size and PWAS location on disbond detection is presented. The power and energy transduction between PWAS and structure is studied analytically with a wave propagation method. Special attention is given to the mechatronics modeling of the complete transduction cycle from electrical excitation into ultrasonic acoustic waves by the piezoelectric effect, the transfer through the structure, and finally reverse piezoelectric transduction to generate the received electric signal. It is found that the combination of PWAS size and wave frequency/wavelength play an important role in identifying transduction maxima and minima that could be exploited to achieve an optimum power-efficient design. The multi-physics finite element method (MP-FEM), which permits fine discretization of damaged regions and complicated structural geometries, is used to study the generation of guided waves in a plate from an electrically excited transmitter PWAS and the capture of these waves as electric

  3. In situ detection and analysis of laser-induced damage on a 1.5-m multilayer-dielectric grating compressor for high-energy, petawatt-class laser systems.

    PubMed

    Qiao, J; Schmid, A W; Waxer, L J; Nguyen, T; Bunkenburg, J; Kingsley, C; Kozlov, A; Weiner, D

    2010-05-10

    A grating-inspection system and a damage-analysis method have been developed to measure in situ laser-induced damage on a 1.5-m tiled-grating assembly of the OMEGA EP pulse compressor during a 15-ps, 2.2-kJ energy ramp. The beam fluence at which significant damage growth occurred was determined. This is the first report on beam fluence versus laser-induced-damage growth of meter-sized multilayer-dielectric-diffraction gratings. This result was correlated to the damage-probability measurement conducted on a small grating sample and is consistent with the fluence, corresponding to 100% damage probability. PMID:20588897

  4. Damage Detection Based on Static Strain Responses Using FBG in a Wind Turbine Blade.

    PubMed

    Tian, Shaohua; Yang, Zhibo; Chen, Xuefeng; Xie, Yong

    2015-01-01

    The damage detection of a wind turbine blade enables better operation of the turbines, and provides an early alert to the destroyed events of the blade in order to avoid catastrophic losses. A new non-baseline damage detection method based on the Fiber Bragg grating (FBG) in a wind turbine blade is developed in this paper. Firstly, the Chi-square distribution is proven to be an effective damage-sensitive feature which is adopted as the individual information source for the local decision. In order to obtain the global and optimal decision for the damage detection, the feature information fusion (FIF) method is proposed to fuse and optimize information in above individual information sources, and the damage is detected accurately through of the global decision. Then a 13.2 m wind turbine blade with the distributed strain sensor system is adopted to describe the feasibility of the proposed method, and the strain energy method (SEM) is used to describe the advantage of the proposed method. Finally results show that the proposed method can deliver encouraging results of the damage detection in the wind turbine blade. PMID:26287200

  5. Damage Detection Based on Static Strain Responses Using FBG in a Wind Turbine Blade

    PubMed Central

    Tian, Shaohua; Yang, Zhibo; Chen, Xuefeng; Xie, Yong

    2015-01-01

    The damage detection of a wind turbine blade enables better operation of the turbines, and provides an early alert to the destroyed events of the blade in order to avoid catastrophic losses. A new non-baseline damage detection method based on the Fiber Bragg grating (FBG) in a wind turbine blade is developed in this paper. Firstly, the Chi-square distribution is proven to be an effective damage-sensitive feature which is adopted as the individual information source for the local decision. In order to obtain the global and optimal decision for the damage detection, the feature information fusion (FIF) method is proposed to fuse and optimize information in above individual information sources, and the damage is detected accurately through of the global decision. Then a 13.2 m wind turbine blade with the distributed strain sensor system is adopted to describe the feasibility of the proposed method, and the strain energy method (SEM) is used to describe the advantage of the proposed method. Finally results show that the proposed method can deliver encouraging results of the damage detection in the wind turbine blade. PMID:26287200

  6. Automated laser-based barely visible impact damage detection in honeycomb sandwich composite structures

    SciTech Connect

    Girolamo, D. Yuan, F. G.; Girolamo, L.

    2015-03-31

    Nondestructive evaluation (NDE) for detection and quantification of damage in composite materials is fundamental in the assessment of the overall structural integrity of modern aerospace systems. Conventional NDE systems have been extensively used to detect the location and size of damages by propagating ultrasonic waves normal to the surface. However they usually require physical contact with the structure and are time consuming and labor intensive. An automated, contactless laser ultrasonic imaging system for barely visible impact damage (BVID) detection in advanced composite structures has been developed to overcome these limitations. Lamb waves are generated by a Q-switched Nd:YAG laser, raster scanned by a set of galvano-mirrors over the damaged area. The out-of-plane vibrations are measured through a laser Doppler Vibrometer (LDV) that is stationary at a point on the corner of the grid. The ultrasonic wave field of the scanned area is reconstructed in polar coordinates and analyzed for high resolution characterization of impact damage in the composite honeycomb panel. Two methodologies are used for ultrasonic wave-field analysis: scattered wave field analysis (SWA) and standing wave energy analysis (SWEA) in the frequency domain. The SWA is employed for processing the wave field and estimate spatially dependent wavenumber values, related to discontinuities in the structural domain. The SWEA algorithm extracts standing waves trapped within damaged areas and, by studying the spectrum of the standing wave field, returns high fidelity damage imaging. While the SWA can be used to locate the impact damage in the honeycomb panel, the SWEA produces damage images in good agreement with X-ray computed tomographic (X-ray CT) scans. The results obtained prove that the laser-based nondestructive system is an effective alternative to overcome limitations of conventional NDI technologies.

  7. Automated laser-based barely visible impact damage detection in honeycomb sandwich composite structures

    NASA Astrophysics Data System (ADS)

    Girolamo, D.; Girolamo, L.; Yuan, F. G.

    2015-03-01

    Nondestructive evaluation (NDE) for detection and quantification of damage in composite materials is fundamental in the assessment of the overall structural integrity of modern aerospace systems. Conventional NDE systems have been extensively used to detect the location and size of damages by propagating ultrasonic waves normal to the surface. However they usually require physical contact with the structure and are time consuming and labor intensive. An automated, contactless laser ultrasonic imaging system for barely visible impact damage (BVID) detection in advanced composite structures has been developed to overcome these limitations. Lamb waves are generated by a Q-switched Nd:YAG laser, raster scanned by a set of galvano-mirrors over the damaged area. The out-of-plane vibrations are measured through a laser Doppler Vibrometer (LDV) that is stationary at a point on the corner of the grid. The ultrasonic wave field of the scanned area is reconstructed in polar coordinates and analyzed for high resolution characterization of impact damage in the composite honeycomb panel. Two methodologies are used for ultrasonic wave-field analysis: scattered wave field analysis (SWA) and standing wave energy analysis (SWEA) in the frequency domain. The SWA is employed for processing the wave field and estimate spatially dependent wavenumber values, related to discontinuities in the structural domain. The SWEA algorithm extracts standing waves trapped within damaged areas and, by studying the spectrum of the standing wave field, returns high fidelity damage imaging. While the SWA can be used to locate the impact damage in the honeycomb panel, the SWEA produces damage images in good agreement with X-ray computed tomographic (X-ray CT) scans. The results obtained prove that the laser-based nondestructive system is an effective alternative to overcome limitations of conventional NDI technologies.

  8. Analysis of shape memory alloy sensory particles for damage detection via substructure and continuum damage modeling

    NASA Astrophysics Data System (ADS)

    Bielefeldt, Brent R.; Benzerga, A. Amine; Hartl, Darren J.

    2016-04-01

    The ability to monitor and predict the structural health of an aircraft is of growing importance to the aerospace industry. Currently, structural inspections and maintenance are based upon experiences with similar aircraft operating in similar conditions. While effective, these methods are time-intensive and unnecessary if the aircraft is not in danger of structural failure. It is imagined that future aircraft will utilize non-destructive evaluation methods, allowing for the near real-time monitoring of structural health. A particularly interesting method involves utilizing the unique transformation response of shape memory alloy (SMA) particles embedded in an aircraft structure. By detecting changes in the mechanical and/or electromagnetic responses of embedded particles, operators could detect the formation or propagation of fatigue cracks in the vicinity of these particles. This work focuses on a finite element model of SMA particles embedded in an aircraft wing using a substructure modeling approach in which degrees of freedom are retained only at specified points of connection to other parts or the application of boundary conditions, greatly reducing computational cost. Previous work evaluated isolated particle response to a static crack to numerically demonstrate and validate this damage detection method. This paper presents the implementation of a damage model to account for crack propagation and examine for the first time the effect of particle configuration and/or relative placement with respect to the ability to detect damage.

  9. A Coupled Approach for Structural Damage Detection with Incomplete Measurements

    NASA Technical Reports Server (NTRS)

    James, George; Cao, Timothy; Kaouk, Mo; Zimmerman, David

    2013-01-01

    This historical work couples model order reduction, damage detection, dynamic residual/mode shape expansion, and damage extent estimation to overcome the incomplete measurements problem by using an appropriate undamaged structural model. A contribution of this work is the development of a process to estimate the full dynamic residuals using the columns of a spring connectivity matrix obtained by disassembling the structural stiffness matrix. Another contribution is the extension of an eigenvector filtering procedure to produce full-order mode shapes that more closely match the measured active partition of the mode shapes using a set of modified Ritz vectors. The full dynamic residuals and full mode shapes are used as inputs to the minimum rank perturbation theory to provide an estimate of damage location and extent. The issues associated with this process are also discussed as drivers of near-term development activities to understand and improve this approach.

  10. Damage detection and characterization using fiber optic sensors

    NASA Astrophysics Data System (ADS)

    Glisic, Branko; Sigurdardottir, Dorotea; Yao, Yao; Hubbell, David

    2013-04-01

    Fiber optic sensors (FOS) have significantly evolved and have reached their market maturity during the last decade. Their widely recognized advantages are high precision, long-term stability, and durability. But in addition to these advantageous performances, FOS technologies allow for affordable instrumentation of large areas of structure enabling global large-scale monitoring based on long-gauge sensors and integrity monitoring based on distributed sensors. These two approaches are particularly suitable for damage detection and characterization, i.e., damage localization and to certain extent quantification and propagation, as illustrated by two applications presented in detail in this paper: post-tensioned concrete bridge and segmented concrete pipeline. Early age cracking was detected, localized and quantified in the concrete deck of a pedestrian bridge using embedded long-gauge FOS. Post-tensioning of deck closed the cracks; however, permanent weakening in a bridge joint occurred due to cracking and it was identified and quantified. The damage was confirmed using embedded distributed FOS and a separate load test of the bridge. Real-size concrete pipeline specimens and surrounding soil were equipped with distributed FOS and exposed to permanent ground displacement in a large-scale testing facility. Two tests were performed on different pipeline specimens. The sensors bonded on the pipeline specimens successfully detected and localized rupture of pipeline joints, while the sensors embedded in the soil were able to detect and localize the failure plane. Comparison with strain-gauges installed on the pipeline and visual inspection after the test confirmed accurate damage detection and characterization.

  11. Detection Of Tornado Damage Tracks With EOS Data

    NASA Technical Reports Server (NTRS)

    Jedlovec, Gary J.; Nair, Udaysankar; Haines, Stephanie L.

    2005-01-01

    The damage surveys conducted by the NWS in the aftermath of a reported tornadic event are used to document the location of the tornado ground damage track (path length and width) and an estimation of the tornado intensity. This study explored the possibility of using near real-time medium and high-resolution satellite imagery from the NASA EOS satellites to provide additional information for the surveys. MODIS and ASTER data were used to study the damage tracks from three tornadic storms; the La Plata, Maryland storm of 28 April 2002 and the Carter-Butler Counties and Madison County Missouri storms of 24 April 2002. These storms varied in intensity (from F0-F4) and occurred over regions with different land use. It was found that, depending on the nature of land use, tornado damage tracks from intense storms (F2 or greater) may be evident in both ASTER and MODIS satellite imagery. In areas of dense vegetation the scar patterns show up very clearly, while in areas of grassland and regions with few trees, scar patterns are not at all obvious in the satellite imagery. The detection of previously unidentified segments of a damage track caused by the 24 April 2004 Madison County, Missouri tornado demonstrates the utility of satellite imagery for damage surveys. However, the capability to detect tornado tracks in satellite imagery appears to be as much dependent on the nature of the underlying surface and land use as on the severity of the tornadic storm. The imaging sensors on the NPOESS operational satellites to be launched in 2006 will continue the unique observing capabilities of the EOS instruments.

  12. In-situ damage detection using self-sensing composites

    NASA Astrophysics Data System (ADS)

    Malik, Shoaib A.; Wang, Liwei; Mahendran, Ramani S.; Harris, Dee; Ojo, Samuel O.; Collins, Dave; Paget, Mark; Pandita, Surya D.; Machavaram, Venkata R.; Fernando, Gerard F.

    2009-03-01

    The focus of this paper is on real-time damage detection in reinforcing fiber bundles and composites using high-speed photography and image analysis. In other words, the end of a reinforcing fiber bundle or composite is imaged and the sequence of fiber fracture is monitored using a high-speed camera. These studies were undertaken using as-received and silane-treated custom-made optical fibers of around 12 μm diameter and E-glass fibers of 15 (+/-3) μm diameter. The first part of this paper reports on the techniques that were developed to produce void-free test specimens and the procedures used for imaging the end of the fiber bundle and composite during tensile loading. Evanescent wave spectroscopy was used to study the effect of silane treatment on the cross-linking kinetics of an epoxy/amine resin system. Conventional piezo-electric acoustic emission (AE) transducers were used to monitor the acoustic events occurring during the tensile test. The signals from the AE transducers were used to trigger the high-speed camera. The second part of this paper presents details of the image analysis routines that were developed to track the light intensity transmitted through individual fibers during tensile loading. Good correlation was observed between the transmitted light intensity and the AE signals.

  13. Long distance laser ultrasonic propagation imaging system for damage visualization

    NASA Astrophysics Data System (ADS)

    Lee, Jung-Ryul; Shin, He-Jin; Chia, Chen Ciang; Dhital, Dipesh; Yoon, Dong-Jin; Huh, Yong-Hak

    2011-12-01

    Wind turbine blade failure is the most prominent and common type of damage occurring in operating wind turbine systems. Conventional nondestructive testing systems are not available for in situ wind turbine blades. We propose a portable long distance ultrasonic propagation imaging (LUPI) system that uses a laser beam targeting and scanning system to excite, from a long distance, acoustic emission sensors installed in the blade. An examination of the beam collimation effect using geometric parameters of a commercial 2 MW wind turbine provided Lamb wave amplitude increases of 41.5 and 23.1 dB at a distance of 40 m for symmetrical and asymmetrical modes, respectively, in a 2 mm-thick stainless steel plate. With this improvement in signal-to-noise ratio, a feasibility study of damage detection was conducted with a 5 mm-thick composite leading edge specimen. To develop a reliable damage evaluation system, the excitation/sensing technology and the associated damage visualization algorithm are equally important. Hence, our results provide a new platform based on anomalous wave propagation imaging (AWPI) methods with adjacent wave subtraction, reference wave subtraction, reference image subtraction, and the variable time window amplitude mapping method. The advantages and disadvantages of AWPI algorithms are reported in terms of reference data requirements, signal-to-noise ratios, and damage evaluation accuracy. The compactness and portability of the proposed UPI system are also important for in-field applications at wind farms.

  14. Advanced signal processing technique for damage detection in steel tubes

    NASA Astrophysics Data System (ADS)

    Amjad, Umar; Yadav, Susheel Kumar; Dao, Cac Minh; Dao, Kiet; Kundu, Tribikram

    2016-04-01

    In recent years, ultrasonic guided waves gained attention for reliable testing and characterization of metals and composites. Guided wave modes are excited and detected by PZT (Lead Zirconate Titanate) transducers either in transmission or reflection mode. In this study guided waves are excited and detected in the transmission mode and the phase change of the propagating wave modes are recorded. In most of the other studies reported in the literature, the change in the received signal strength (amplitude) is investigated with varying degrees of damage while in this study the change in phase is correlated with the extent of damage. Feature extraction techniques are used for extracting phase and time-frequency information. The main advantage of this approach is that the bonding condition between the transducer and the specimen does not affect the phase while it can affect the strength of recorded signal. Therefore, if the specimen is not damaged but the transducer-specimen bonding is deteriorated then the received signal strength is altered but the phase remains same and thus false positive predictions for damage can be avoided.

  15. Damage Detection in Composite Structures with Wavenumber Array Data Processing

    NASA Technical Reports Server (NTRS)

    Tian, Zhenhua; Leckey, Cara; Yu, Lingyu

    2013-01-01

    Guided ultrasonic waves (GUW) have the potential to be an efficient and cost-effective method for rapid damage detection and quantification of large structures. Attractive features include sensitivity to a variety of damage types and the capability of traveling relatively long distances. They have proven to be an efficient approach for crack detection and localization in isotropic materials. However, techniques must be pushed beyond isotropic materials in order to be valid for composite aircraft components. This paper presents our study on GUW propagation and interaction with delamination damage in composite structures using wavenumber array data processing, together with advanced wave propagation simulations. Parallel elastodynamic finite integration technique (EFIT) is used for the example simulations. Multi-dimensional Fourier transform is used to convert time-space wavefield data into frequency-wavenumber domain. Wave propagation in the wavenumber-frequency domain shows clear distinction among the guided wave modes that are present. This allows for extracting a guided wave mode through filtering and reconstruction techniques. Presence of delamination causes spectral change accordingly. Results from 3D CFRP guided wave simulations with delamination damage in flat-plate specimens are used for wave interaction with structural defect study.

  16. A simple damage detection indicator using operational deflection shapes

    NASA Astrophysics Data System (ADS)

    Sampaio, R. P. C.; Maia, N. M. M.; Almeida, R. A. B.; Urgueira, A. P. V.

    2016-05-01

    Catastrophic structural failure of aircrafts, bridges, buildings and other structures in modern societies has always been of primary concern because of the loss of human lifes and of negative economic impact. The aging of the structures, the growing dependency on their role in our networks of transportation, energy and comunications, the smaller construction tolerances, the bigger power demanded and the media and society awardness to catastrophic events are sufficient motivations for the growing field of structural health monitoring, which aims at assessing the actual condition of a structure and to identify incipient damage. Damage identification can be considered as a two step process, the detection and the diagnosis. The former, and fundamental step, is the confirmation of an efective damage existence. When the response is affirmative, the latter step begins with the diagnosis, and then the questions are: where?, how much?, what type?, when will it fail? In this paper the authors propose a simple method to detect and relatively quantify structural damage by using measured vibrations data, specifically the operational deflections shapes. Numerical simulations and experimental tests are presented to validate the proposed method.

  17. Interior intrusion detection systems

    SciTech Connect

    Rodriguez, J.R.; Matter, J.C. ); Dry, B. )

    1991-10-01

    The purpose of this NUREG is to present technical information that should be useful to NRC licensees in designing interior intrusion detection systems. Interior intrusion sensors are discussed according to their primary application: boundary-penetration detection, volumetric detection, and point protection. Information necessary for implementation of an effective interior intrusion detection system is presented, including principles of operation, performance characteristics and guidelines for design, procurement, installation, testing, and maintenance. A glossary of sensor data terms is included. 36 figs., 6 tabs.

  18. Offline and online detection of damage using autoregressive models and artificial neural networks

    NASA Astrophysics Data System (ADS)

    Omenzetter, Piotr; de Lautour, Oliver R.

    2007-04-01

    Developed to study long, regularly sampled streams of data, time series analysis methods are being increasingly investigated for the use of Structural Health Monitoring. In this research, Autoregressive (AR) models are used in conjunction with Artificial Neural Networks (ANNs) for damage detection, localisation and severity assessment. In the first reported experimental exercise, AR models were used offline to fit the acceleration time histories of a 3-storey test structure in undamaged and various damaged states when excited by earthquake motion simulated on a shake table. Damage was introduced into the structure by replacing the columns with those of a thinner thickness. Analytical models of the structure in both damaged and undamaged states were also developed and updated using experimental data in order to determine structural stiffness. The coefficients of AR models were used as damage sensitive features and input into an ANN to build a relationship between them and the remaining structural stiffness. In the second, analytical exercise, a system with gradually progressing damage was numerically simulated and acceleration AR models with exogenous inputs were identified recursively. A trained ANN was then required to trace the structural stiffness online. The results for the offline and online approach showed the efficiency of using AR coefficient as damage sensitive features and good performance of the ANNs for damage detection, localization and quantification.

  19. Early detection of fatigue damage in composite materials

    NASA Technical Reports Server (NTRS)

    Salkind, M. J.

    1975-01-01

    Early detection of fatigue damage in composite materials by nondestructive inspection (NDI) techniques has been demonstrated for glass/epoxy, graphite/glass/epoxy, and graphite/epoxy composites. Modulus and temperature were monitored and a correlation between them observed. Axial modulus and torsional modulus changes were a function of the laminate orientation. Torsional modulus measurements and coin tap tests were performed at 0, 1 million, 5 million, and 10 million cycles, on axial fatigue specimens. Three distinct regions were noted. In the primary region a small but rapid change in stiffness was noted in the first few thousand cycles. This was followed by a secondary region of little or no stiffness change. The tertiary region was characterized by an increasing rate of stiffness change leading to fracture. NDI procedures including holographic interferometry, ultrasonics, penetrant, and X-ray radiography were evaluated for fatigue damage detection.

  20. HC-NIDS: signatures and simulations for detecting cyber-attacks aiming to cause damage against cyber-physical energy systems

    Energy Science and Technology Software Center (ESTSC)

    2014-12-01

    Physical device safety is typically implemented locally using embedded controllers, while operations safety is primarily performed in control centers. Safe operations can be enhanced by correct design of device-level control algorithms, and protocols, procedures and operator training at the control-room level, but all can fail. Moreover, these elements exchange data and issue commands via vulnerable communication layers. In order to secure these gaps and enhance operational safety, we believe monitoring of command sequences must bemore » combined with an awareness of physical device limitations and automata models that capture safety mechanisms. One way of doing this is by leveraging specification-based intrusion detection to monitor for physical constraint violations. The method can also verify that physical infrastructure state is consistent with monitoring information and control commands exchanged between field devices and control centers. This additional security layer enhances protection from both outsider attacks and insider mistakes. We implemented specification-based SCADA command analyzers using physical constraint algorithms directly in the Bro framework and Broccoli APIs for three separate scenarios: a water heater, an automated distribution system, and an over-current protection scheme. To accomplish this, we added low-level analyzers capable of examining control system-specific protocol packets for both Modbus TCP and DNP3, and also higher-level analyzers able to interpret device command and data streams within the context of each device’s physical capabilities and present operational state. Thus the software that we are making available includes the Bro/Broccoli scripts for these three scenarios, as well as simulators, written in C, of those scenarios that generate sample traffic that is monitored by the Bro/Broccoli scripts. In addition, we have also implemented systems to directly pull cyber-physical information from the OSIsoft PI historian

  1. HC-NIDS: signatures and simulations for detecting cyber-attacks aiming to cause damage against cyber-physical energy systems

    SciTech Connect

    2014-12-01

    Physical device safety is typically implemented locally using embedded controllers, while operations safety is primarily performed in control centers. Safe operations can be enhanced by correct design of device-level control algorithms, and protocols, procedures and operator training at the control-room level, but all can fail. Moreover, these elements exchange data and issue commands via vulnerable communication layers. In order to secure these gaps and enhance operational safety, we believe monitoring of command sequences must be combined with an awareness of physical device limitations and automata models that capture safety mechanisms. One way of doing this is by leveraging specification-based intrusion detection to monitor for physical constraint violations. The method can also verify that physical infrastructure state is consistent with monitoring information and control commands exchanged between field devices and control centers. This additional security layer enhances protection from both outsider attacks and insider mistakes. We implemented specification-based SCADA command analyzers using physical constraint algorithms directly in the Bro framework and Broccoli APIs for three separate scenarios: a water heater, an automated distribution system, and an over-current protection scheme. To accomplish this, we added low-level analyzers capable of examining control system-specific protocol packets for both Modbus TCP and DNP3, and also higher-level analyzers able to interpret device command and data streams within the context of each device’s physical capabilities and present operational state. Thus the software that we are making available includes the Bro/Broccoli scripts for these three scenarios, as well as simulators, written in C, of those scenarios that generate sample traffic that is monitored by the Bro/Broccoli scripts. In addition, we have also implemented systems to directly pull cyber-physical information from the OSIsoft PI historian system. We

  2. PVDF piezo film as dynamic strain sensor for local damage detection of steel frame buildings

    NASA Astrophysics Data System (ADS)

    Kurata, M.; Li, X.; Fujita, K.; He, L.; Yamaguchi, M.

    2013-04-01

    A structural health monitoring system that aims to extract local damage information (i.e., existence, location and severity) in buildings may require a dense array of transducers due to the high complexity and high degree of statical indeterminacy of their structural system. While monitoring systems for building applications are mostly consisted of seismographs or tremor sensors, a technique to pragmatically and accurately capture strain information of structural members is efficacious for detecting damage in individual members. This paper presents the use of polyvinylidene fluoride piezoelectric films as dynamic strain sensors for detecting local damage in steel moment-resisting frames. First, a damage detection methodology that monitors the changes in the relative distribution of the bending moments in structural systems is presented. Next, an array of dynamic strain sensors networked by wireless sensing units is developed in consideration of its installation cost and efforts when it is applied to real buildings. Finally, the performances of the developed methodology and its sensing system are evaluated through a series of vibration testing using a 5-story steel testbed frame that can simulate seismic damage at beam-to-column connections.

  3. Uncertainty handling in structural damage detection using fuzzy logic and probabilistic simulation

    NASA Astrophysics Data System (ADS)

    Chandrashekhar, M.; Ganguli, Ranjan

    2009-02-01

    A fuzzy logic system (FLS) with a new sliding window defuzzifier is developed for damage detection. The effect of changes in the damage evaluation parameter (frequency) due to uncertainty in material properties is explored and the results of the probabilistic analysis are used to develop a robust FLS for damage detection. Probabilistic analysis is performed using Monte Carlo Simulation (MCS) on a beam finite element (FE) model to calculate statistical properties of the variation in natural frequencies of the beam due to structural damage and material uncertainty. Variation in these frequency measures, further contaminated with measurement noise, are used for testing the FLS. The FLS developed for damage detection in the steel beam having material uncertainty (elastic modulus) with coefficient of variation (COV) of 3 percent and noise level of 0.15 in the measurement data, correctly identifies the fault with an accuracy of about 94 percent. The FLS also accurately classifies the undamaged condition in presence of the mentioned uncertainties reducing the possibility of false alarms. From an algorithmic standpoint, this paper connects the disparate areas of probability and fuzzy logic to alleviate uncertainty issues in damage detection.

  4. Digestive system damage caused by substance abuse.

    PubMed

    Dimitrijević, I; Kalezić, N; Ristić, J; Bojović, O; Dimitrijević, N

    2008-01-01

    Substance abuse and addiction represent a worldwide problem and cause a number of family, social and health problems. Digestive system damage caused by substance intake is an increasing problem amoung drug addicts. Many studies show that substances can cause cancer of all parts of the digestive system. Alcohol consumption was significantly associated with colon and rectal cancer. For rectal cancer, the risk was increased in association with drinking of alcoholic beverages, specialy for beer consumption. Sinthetic drugs such as ecstasy may lead also to digestive and hepatic damage, as well as vascular complications of the stomach. Many studies show the existance of supstance associated enterocolitis as well as ishemic colitis. Diagnosis of ishemic colitis is based on the presence of rectal bleeding, abdominal pain, a history of substance use, supportive endoscopic and histopathologic findings, and the absence of other etiologic mechanisms of ischemic colitis. Great damage to the digestive system is also produced by smuggling narcotics packed into small pages that are afterwards been swallowed or implemented on other sorts of ways inside the smugglers natural body spaces as the rectum or vagina. In the paper authors reviewed literature conserning digestive system damage caused by substance abuse and drug smuggling. PMID:19069706

  5. Feasibility study on an angular velocity-based damage detection method using gyroscopes

    NASA Astrophysics Data System (ADS)

    Sung, S. H.; Lee, J. H.; Park, J. W.; Koo, K. Y.; Jung, H. J.

    2014-07-01

    This paper proposes an angular velocity-based damage detection method using gyroscopes and investigates its feasibility. This study basically intends to enhance the performance of the existing modal flexibility-based methods by replacing accelerations measured from accelerometers with angular velocities measured from gyroscopes. In order to verify the superiority of a gyroscope in damage detection, numerical studies were performed by changing optional parameters such as damage location, severity, and measurement noise. From parametric studies, it was shown that the damage detection results using gyroscopes are more sensitive to damage and more robust to noise generated from the curvature estimation than those using accelerometers. Experimental validations were also carried out to investigate the feasibility of a gyroscope in damage detection. From the results, it was shown that the gyroscope-based damage detection method can successfully identify damage location. In conclusion, it was numerically and experimentally verified that a new damage detection approach using gyroscopes could improve damage detection ability significantly.

  6. LiDAR scan and smart piezo layer combined damage detection

    NASA Astrophysics Data System (ADS)

    Chen, Shenen; Chung, Howard; Park, Youngjin

    2013-04-01

    The motivation of this study is to determine a technique to completely describe the damage state of large deformed structures commonly found during forensic investigations. The combination of Laser Detecting and Ranging (LiDAR) and Piezoelectric (PZT) Sensing Technologies for damage quantification is suggested to generate the full-field description of large deformation of a plate. The test subject is a 16 inch by 16 inch aluminum plate subjected to different damage scenarios. LiDAR is a static scanning laser that provides a 3-dimensional picture of the object. Smart Layer is a commercial PZT actuator/sensor network system that generates stress waves for internal damage evaluation. Both techniques were applied to the test plate after damages are introduced. In order to effectively analyze the results, the images for each test were superimposed. Frequencies that depicted the best interpretation of damage in the direct path images were superimposed with the 3-dimensional LiDAR images. Four damage scenarios were imposed on an aluminum plate including saw cuts at different depths using an electric saw. The final damage is a severe bending of the plate. The bending of the specimen produced an image that located the most severe damage directly under the left hand portion and directly above the right hand portion of the bend.

  7. Application of damage detection methods using passive reconstruction of impulse response functions.

    PubMed

    Tippmann, J D; Zhu, X; Lanza di Scalea, F

    2015-02-28

    In structural health monitoring (SHM), using only the existing noise has long been an attractive goal. The advances in understanding cross-correlations in ambient noise in the past decade, as well as new understanding in damage indication and other advanced signal processing methods, have continued to drive new research into passive SHM systems. Because passive systems take advantage of the existing noise mechanisms in a structure, offshore wind turbines are a particularly attractive application due to the noise created from the various aerodynamic and wave loading conditions. Two damage detection methods using a passively reconstructed impulse response function, or Green's function, are presented. Damage detection is first studied using the reciprocity of the impulse response functions, where damage introduces new nonlinearities that break down the similarity in the causal and anticausal wave components. Damage detection and localization are then studied using a matched-field processing technique that aims to spatially locate sources that identify a change in the structure. Results from experiments conducted on an aluminium plate and wind turbine blade with simulated damage are also presented. PMID:25583863

  8. Non-invasive damage detection in beams using marker extraction and wavelets

    NASA Astrophysics Data System (ADS)

    Song, Yi-Zhe; Bowen, Chris R.; Kim, H. Alicia; Nassehi, Aydin; Padget, Julian; Gathercole, Nick; Dent, Andrew

    2014-12-01

    For structural health monitoring applications there is a need for simple and contact-less methods of Non-Destructive Evaluation (NDE). A number of damage detection techniques have been developed, such as frequency shift, generalised fractal dimension and wavelet transforms with the aim to identify, locate and determine the severity of damage in a material or structure. These techniques are often tailored for factors such as (i) type of material, (ii) damage pattern (crack, delamination), and (iii) the nature of any input signals (space and time). This paper describes and evaluates a wavelet-based damage detection framework that locates damage on cantilevered beams via NDE using computer vision technologies. The novelty of the approach is the use of computer vision algorithms for the contact-less acquisition of modal shapes. Using the proposed method, the modal shapes of cantilever beams are reconstructed by extracting markers using sub-pixel Hough Transforms from images captured using conventional slow motion cameras. The extracted modal shapes are then used as an input for wavelet transform damage detection, exploiting both discrete and continuous variants. The experimental results are verified and compared against finite element analysis. The methodology enables a non-invasive damage detection system that avoids the need for expensive equipment or the attachment of sensors to the structure. Two types of damage are investigated in our experiments: (i) defects induced by removing material to reduce the stiffness of a steel beam and (ii) delaminations in a (0/90/0/90/0)s composite laminate. Results show successful detection of notch depths of 5%, 28% and 50% for the steel beam and of 30 mm delaminations in central and outer layers for the composite laminate.

  9. Neural network based system for damage identification and location in structural and mechanical systems

    SciTech Connect

    Farrar, C.R.; Doebling, S.W.; Prime, M.B.; Cornwell, P.; Kam, M.; Straser, E.G.; Hoerst, B.C.

    1998-11-01

    This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Recent advances in wireless, remotely monitored data acquisition systems coupled with the development of vibration-based damage detection algorithms make the possibility of self- or remotely-monitored structures and mechanical systems appear to be within the capabilities of current technology. However, before such a system can be relied upon to perform this monitoring, the variability of the vibration properties that are the basis for the damage detection algorithm must be understood and quantified. This understanding is necessary so that the artificial intelligence/expert system that is employed to discriminate when changes in modal properties are indicative of damage will not yield false indications of damage. To this end, this project has focused on developing statistical methods for quantifying variability in identified vibration proper ties of structural and mechanical systems.

  10. Robust ultrasonic damage detection under complex environmental conditions using singular value decomposition.

    PubMed

    Liu, Chang; Harley, Joel B; Bergés, Mario; Greve, David W; Oppenheim, Irving J

    2015-04-01

    Guided wave ultrasonics is an attractive monitoring technique for damage diagnosis in large-scale plate and pipe structures. Damage can be detected by comparing incoming records with baseline records collected on intact structure. However, during long-term monitoring, environmental and operational conditions often vary significantly and produce large changes in the ultrasonic signals, thereby challenging the baseline comparison based damage detection. Researchers developed temperature compensation methods to eliminate the effects of temperature variation, but they have limitations in practical implementations. In this paper, we develop a robust damage detection method based on singular value decomposition (SVD). We show that the orthogonality of singular vectors ensures that the effect of damage and that of environmental and operational variations are separated into different singular vectors. We report on our field ultrasonic monitoring of a 273.05 mm outer diameter pipe segment, which belongs to a hot water piping system in continuous operation. We demonstrate the efficacy of our method on experimental pitch-catch records collected during seven months. We show that our method accurately detects the presence of a mass scatterer, and is robust to the environmental and operational variations exhibited in the practical system. PMID:25600118

  11. In situ CTE measurements and damage detection using optical metrology

    NASA Astrophysics Data System (ADS)

    Rajaram, Satish; Cuadra, Jefferson; Saralaya, Raghav; Bartoli, Ivan; Kontsos, Antonios

    2016-02-01

    This paper presents a methodology to make coefficient of thermal expansion measurements through the combined use of two non-contact and full field optical metrology methods including digital image correlation and infrared thermography. In this context, active Infrared Thermography techniques combined with contact and non-contact deformation measurement methods have already been reported to measure materials’ thermal expansion. In addition, such techniques have been reported to be capable to detect surface and subsurface defects from changes in homogenous heat diffusion due to damage. Based on this knowledge, it is hypothesized in this article that the material response induced by thermal loading and quantified by coefficient of thermal expansion measurements could be further used as an indicator of damage. To validate the hypothesis three measurements were performed. The first established the effectiveness of using deformation and thermal full field data for coefficient of thermal expansion measurements. The second intended to demonstrate the advantage of using such full field data in order to provide site-specific measurements of thermal expansion. Finally damage was a priori induced to a metallic specimen, and the measured variations of local CTE confirmed the potential of using the described approach as a means of damage quantification in materials and structures.

  12. Sensitivity of PZT Impedance Sensors for Damage Detection of Concrete Structures

    PubMed Central

    Yang, Yaowen; Hu, Yuhang; Lu, Yong

    2008-01-01

    Piezoelectric ceramic Lead Zirconate Titanate (PZT) based electro-mechanical impedance (EMI) technique for structural health monitoring (SHM) has been successfully applied to various engineering systems. However, fundamental research work on the sensitivity of the PZT impedance sensors for damage detection is still in need. In the traditional EMI method, the PZT electro-mechanical (EM) admittance (inverse of the impedance) is used as damage indicator, which is difficult to specify the effect of damage on structural properties. This paper uses the structural mechanical impedance (SMI) extracted from the PZT EM admittance signature as the damage indicator. A comparison study on the sensitivity of the EM admittance and the structural mechanical impedance to the damages in a concrete structure is conducted. Results show that the SMI is more sensitive to the damage than the EM admittance thus a better indicator for damage detection. Furthermore, this paper proposes a dynamic system consisting of a number of single-degree-of-freedom elements with mass, spring and damper components to model the SMI. A genetic algorithm is employed to search for the optimal value of the unknown parameters in the dynamic system. An experiment is carried out on a two-storey concrete frame subjected to base vibrations that simulate earthquake. A number of PZT sensors are regularly arrayed and bonded to the frame structure to acquire PZT EM admittance signatures. The relationship between the damage index and the distance of the PZT sensor from the damage is studied. Consequently, the sensitivity of the PZT sensors is discussed and their sensing region in concrete is derived.

  13. Detection of structural damage using novelty detection algorithm under variational environmental and operational conditions

    NASA Astrophysics Data System (ADS)

    El Mountassir, M.; Yaacoubi, S.; Dahmene, F.

    2015-07-01

    Novelty detection is a widely used algorithm in different fields of study due to its capabilities to recognize any kind of abnormalities in a specific process in order to ensure better working in normal conditions. In the context of Structural Health Monitoring (SHM), this method is utilized as damage detection technique because the presence of defects can be considered as abnormal to the structure. Nevertheless, the performance of such a method could be jeopardized if the structure is operating in harsh environmental and operational conditions (EOCs). In this paper, novelty detection statistical technique is used to investigate the detection of damages under various EOCs. Experiments were conducted with different scenarios: damage sizes and shapes. EOCs effects were simulated by adding stochastic noise to the collected experimental data. Different levels of noise were studied to determine the accuracy and the performance of the proposed method.

  14. Damage detection in elastic structures using vibratory residual forces and weighted sensitivity

    NASA Technical Reports Server (NTRS)

    Ricles, J. M.; Kosmatka, J. B.

    1992-01-01

    A methodology is presented for detecting structural damage in elastic structures by nondestructive means. Measured modal test data along with a correlated analytical structural model are used to locate potentially damaged regions using residual modal force vectors and to conduct a weighted sensitivity analysis to assess the extent of mass and/or stiffness variations, where damage is characterized as a stiffness reduction. The current approach is unique among other approaches in that it accounts for (1) variations in system mass, system stiffness, and mass center (locations), (2) perturbations of both the natural frequencies and modal vectors, and (3) statistical confidence factors for the structural parameters and potential experimental instrumentation error. Moreover, this procedure can be used with either full or reduced models. A wide variety of numerical examples are presented that show that the current method provides a precise indication of both the location and the extent of structural damage.

  15. Wireless and embedded carbon nanotube networks for damage detection in concrete structures

    NASA Astrophysics Data System (ADS)

    Saafi, Mohamed

    2009-09-01

    Concrete structures undergo an uncontrollable damage process manifesting in the form of cracks due to the coupling of fatigue loading and environmental effects. In order to achieve long-term durability and performance, continuous health monitoring systems are needed to make critical decisions regarding operation, maintenance and repairs. Recent advances in nanostructured materials such as carbon nanotubes have opened the door for new smart and advanced sensing materials that could effectively be used in health monitoring of structures where wireless and real time sensing could provide information on damage development. In this paper, carbon nanotube networks were embedded into a cement matrix to develop an in situ wireless and embedded sensor for damage detection in concrete structures. By wirelessly measuring the change in the electrical resistance of the carbon nanotube networks, the progress of damage can be detected and monitored. As a proof of concept, wireless cement-carbon nanotube sensors were embedded into concrete beams and subjected to monotonic and cyclic loading to evaluate the effect of damage on their response. Experimental results showed that the wireless response of the embedded nanotube sensors changes due to the formation of cracks during loading. In addition, the nanotube sensors were able to detect the initiation of damage at an early stage of loading.

  16. Damage detection using the signal entropy of an ultrasonic sensor network

    NASA Astrophysics Data System (ADS)

    Rojas, E.; Baltazar, A.; Loh, K. J.

    2015-07-01

    Piezoelectric ultrasonic sensors used to propagate guided waves can potentially be implemented to inspect large areas in engineering structures. However, the inherent dispersion and noise of guided acoustic signals, multiple echoes in the structure, as well as a lack of an approximate or exact model, limit their use as a continuous structural health monitoring system. In this work, the implementation of a network of piezoelectric sensors randomly placed on a plate-like structure to detect and locate artificial damage is studied. A network of macro fiber composite (MFC) sensors working in a pitch-catch configuration was set on an aluminum thin plate 1.9 mm in thickness. Signals were analyzed in the time-scale domain using the discrete wavelet transform. The objectives of this work were threefold, namely to first develop a damage index based on the entropy distribution using short time wavelet entropy of the ultrasonic waves generated by a sensor network, second to determine the performance of an array of spare MFC sensors to detect artificial damage, and third to implement a time-of-arrival (TOA) algorithm on the gathered signals for damage location of an artificial circular discontinuity. Our preliminary test results show that the proposed methodology provides sufficient information for damage detection, which, once combined with the TOA algorithm, allows localization of the damage.

  17. Wireless and embedded carbon nanotube networks for damage detection in concrete structures.

    PubMed

    Saafi, Mohamed

    2009-09-30

    Concrete structures undergo an uncontrollable damage process manifesting in the form of cracks due to the coupling of fatigue loading and environmental effects. In order to achieve long-term durability and performance, continuous health monitoring systems are needed to make critical decisions regarding operation, maintenance and repairs. Recent advances in nanostructured materials such as carbon nanotubes have opened the door for new smart and advanced sensing materials that could effectively be used in health monitoring of structures where wireless and real time sensing could provide information on damage development. In this paper, carbon nanotube networks were embedded into a cement matrix to develop an in situ wireless and embedded sensor for damage detection in concrete structures. By wirelessly measuring the change in the electrical resistance of the carbon nanotube networks, the progress of damage can be detected and monitored. As a proof of concept, wireless cement-carbon nanotube sensors were embedded into concrete beams and subjected to monotonic and cyclic loading to evaluate the effect of damage on their response. Experimental results showed that the wireless response of the embedded nanotube sensors changes due to the formation of cracks during loading. In addition, the nanotube sensors were able to detect the initiation of damage at an early stage of loading. PMID:19724107

  18. Nondestructive Structural Damage Detection in Flexible Space Structures Using Vibration Characterization

    NASA Technical Reports Server (NTRS)

    Ricles, James M.

    1991-01-01

    Spacecraft are susceptible to structural damage over their operating life from impact, environmental loads, and fatigue. Structural damage that is not detected and not corrected may potentially cause more damage and eventually catastrophic structural failure. NASA's current fleet of reusable spacecraft, namely the Space Shuttle, has been flown on several missions. In addition, configurations of future NASA space structures, e.g. Space Station Freedom, are larger and more complex than current structures, making them more susceptible to damage as well as being more difficult to inspect. Consequently, a reliable structural damage detection capability is essential to maintain the flight safety of these structures. Visual inspections alone can not locate impending material failure (fatigue cracks, yielding); it can only observe post-failure situations. An alternative approach is to develop an inspection and monitoring system based on vibration characterization that assesses the integrity of structural and mechanical components. A methodology for detecting structural damage is presented. This methodology is based on utilizing modal test data in conjunction with a correlated analytical model of the structure to: (1) identify the structural dynamic characteristics (resonant frequencies and mode shapes) from measurements of ambient motions and/or force excitation; (2) calculate modal residual force vectors to identify the location of structural damage; and (3) conduct a weighted sensitivity analysis in order to assess the extent of mass and stiffness variations, where structural damage is characterized by stiffness reductions. The approach is unique from other existing approaches in that varying system mass and stiffness, mass center locations, the perturbation of both the natural frequencies and mode shapes, and statistical confidence factors for structural parameters and experimental instrumentation are all accounted for directly.

  19. Structural damage detection for in-service highway bridge under operational and environmental variability

    NASA Astrophysics Data System (ADS)

    Jin, Chenhao; Li, Jingcheng; Jang, Shinae; Sun, Xiaorong; Christenson, Richard

    2015-03-01

    Structural health monitoring has drawn significant attention in the past decades with numerous methodologies and applications for civil structural systems. Although many researchers have developed analytical and experimental damage detection algorithms through vibration-based methods, these methods are not widely accepted for practical structural systems because of their sensitivity to uncertain environmental and operational conditions. The primary environmental factor that influences the structural modal properties is temperature. The goal of this article is to analyze the natural frequency-temperature relationships and detect structural damage in the presence of operational and environmental variations using modal-based method. For this purpose, correlations between natural frequency and temperature are analyzed to select proper independent variables and inputs for the multiple linear regression model and neural network model. In order to capture the changes of natural frequency, confidence intervals to detect the damages for both models are generated. A long-term structural health monitoring system was installed on an in-service highway bridge located in Meriden, Connecticut to obtain vibration and environmental data. Experimental testing results show that the variability of measured natural frequencies due to temperature is captured, and the temperature-induced changes in natural frequencies have been considered prior to the establishment of the threshold in the damage warning system. This novel approach is applicable for structural health monitoring system and helpful to assess the performance of the structure for bridge management and maintenance.

  20. Guided Wave and Damage Detection in Composite Laminates Using Different Fiber Optic Sensors

    PubMed Central

    Li, Fucai; Murayama, Hideaki; Kageyama, Kazuro; Shirai, Takehiro

    2009-01-01

    Guided wave detection using different fiber optic sensors and their applications in damage detection for composite laminates were systematically investigated and compared in this paper. Two types of fiber optic sensors, namely fiber Bragg gratings (FBG) and Doppler effect-based fiber optic (FOD) sensors, were addressed and guided wave detection systems were constructed for both types. Guided waves generated by a piezoelectric transducer were propagated through a quasi-isotropic carbon fiber reinforced plastic (CFRP) laminate and acquired by these fiber optic sensors. Characteristics of these fiber optic sensors in ultrasonic guided wave detection were systematically compared. Results demonstrated that both the FBG and FOD sensors can be applied in guided wave and damage detection for the CFRP laminates. The signal-to-noise ratio (SNR) of guided wave signal captured by an FOD sensor is relatively high in comparison with that of the FBG sensor because of their different physical principles in ultrasonic detection. Further, the FOD sensor is sensitive to the damage-induced fundamental shear horizontal (SH0) guided wave that, however, cannot be detected by using the FBG sensor, because the FOD sensor is omnidirectional in ultrasound detection and, in contrast, the FBG sensor is severely direction dependent. PMID:22412347

  1. Sensitivity analysis of an auto-correlation-function-based damage index and its application in structural damage detection

    NASA Astrophysics Data System (ADS)

    Zhang, Muyu; Schmidt, Rüdiger

    2014-12-01

    Structural damage detection using time domain vibration responses has advantages such as simplicity in calculation and no requirement of a finite element model, which attracts more and more researchers in recent years. In present paper, a new approach to detect the damage based on the auto correlation function is proposed. The maximum values of the auto correlation function of the vibration response signals from different measurement points are formulated as a vector called Auto Correlation Function at Maximum Point Value Vector, AMV for short. The relative change of the normalized AMV before and after damage is used as the damage index to locate the damage. Sensitivity analysis of the normalized AMV with respect to the local stiffness shows that the normalized AMV has a sharp change around the local stiffness change location, which means the normalized AMV is a good indicator to detect the damage even when the damage is very small. Stiffness reduction detection of a 12-story frame structure is provided to illustrate the validity, effectiveness and the anti-noise ability of the proposed method. Comparison of the normalized AMV and the other correlation-function-based damage detection method shows the normalized AMV has a better detectability.

  2. Idaho Explosive Detection System

    SciTech Connect

    Klinger, Jeff

    2011-01-01

    Learn how INL researchers are making the world safer by developing an explosives detection system that can inspect cargo. For more information about INL security research, visit http://www.facebook.com/idahonationallaboratory

  3. Idaho Explosive Detection System

    ScienceCinema

    Klinger, Jeff

    2013-05-28

    Learn how INL researchers are making the world safer by developing an explosives detection system that can inspect cargo. For more information about INL security research, visit http://www.facebook.com/idahonationallaboratory

  4. Damage detection of civil infrastructures with piezoelectric oscillator sensors

    NASA Astrophysics Data System (ADS)

    Roh, Y. R.; Kim, D. Y.; Park, S. H.; Yun, C. B.

    2006-03-01

    Many researches have been reported on the condition monitoring of civil infrastructures by means of piezoelectric sensors. Most of them made use of the impedance change of the piezoelectric device in relation to the creation of internal damages to the structure. The impedance measurement is a well accepted method in the piezoelectric sensor area, and has been proved by many authors to be useful for civil structure diagnosis. However, the impedance measurement normally requires sophisticated equipment and analysis technology. For more general and wide application of the piezoelectric diagnosis tool, a new methodology is desired to overcome the limitations of the impedance measurement. This paper presents the feasibility of a piezoelectric oscillator sensor to detect the damages in civil infrastructures. The oscillator sensor is composed of an electronic feedback oscillator circuit and a piezoelectric thickness mode vibrator to be attached to the structure of interest. Damage to the structure causes a change in the impedance spectrum of the structure, which results in a corresponding change of the resonant frequency of the structure. The oscillator sensors can instantly detect the frequency change in a very simple manner. Feasibility of the piezoelectric oscillator sensor was verified in this work with a sample aluminum plate where artificial cracks of different depth were imposed in sequence. Validity of the measurement was confirmed through comparison of the experimental data with the results of finite element analyses of the plate with cracks. Performance of the oscillator sensor was also compared with that of its conventional counterpart, i.e. impedance measurement, to manifest the superiority of the oscillator sensor.

  5. Damage detection and model refinement using elemental stiffness perturbations with constrained connectivity

    SciTech Connect

    Doebling, S.W.

    1996-04-01

    A new optimal update method for the correlation of dynamic structural finite element models with modal data is presented. The method computes a minimum-rank solution for the perturbations of the elemental stiffness parameters while constraining the connectivity of the global stiffness matrix. The resulting model contains a more accurate representation of the dynamics of the test structure. The changes between the original model and the updated model can be interpreted as modeling errors or as changes in the structure resulting from damage. The motivation for the method is presented in the context of existing optimal matrix update procedures. The method is demonstrated numerically on a spring-mass system and is also applied to experimental data from the NASA Langley 8-bay truss damage detection experiment. The results demonstrate that the proposed procedure may be useful for updating elemental stiffness parameters in the context of damage detection and model refinement.

  6. Underwater laser detection system

    NASA Astrophysics Data System (ADS)

    Gomaa, Walid; El-Sherif, Ashraf F.; El-Sharkawy, Yasser H.

    2015-02-01

    The conventional method used to detect an underwater target is by sending and receiving some form of acoustic energy. But the acoustic systems have limitations in the range resolution and accuracy; while, the potential benefits of a laserbased underwater target detection include high directionality, high response, and high range accuracy. Lasers operating in the blue-green region of the light spectrum(420 : 570nm)have a several applications in the area of detection and ranging of submersible targets due to minimum attenuation through water ( less than 0.1 m-1) and maximum laser reflection from estimated target (like mines or submarines) to provide a long range of detection. In this paper laser attenuation in water was measured experimentally by new simple method by using high resolution spectrometer. The laser echoes from different targets (metal, plastic, wood, and rubber) were detected using high resolution CCD camera; the position of detection camera was optimized to provide a high reflection laser from target and low backscattering noise from the water medium, digital image processing techniques were applied to detect and discriminate the echoes from the metal target and subtract the echoes from other objects. Extraction the image of target from the scattering noise is done by background subtraction and edge detection techniques. As a conclusion, we present a high response laser imaging system to detect and discriminate small size, like-mine underwater targets.

  7. Bro Intrusion Detection System

    SciTech Connect

    Paxson, Vern; Campbell, Scott; leres, Craig; Lee, Jason

    2006-01-25

    Bro is a Unix-based Network Intrusion Detection System (IDS). Bro monitors network traffic and detects intrusion attempts based on the traffic characteristics and content. Bro detects intrusions by comparing network traffic against rules describing events that are deemed troublesome. These rules might describe activities (e.g., certain hosts connecting to certain services), what activities are worth alerting (e.g., attempts to a given number of different hosts constitutes a "scan"), or signatures describing known attacks or access to known vulnerabilities. If Bro detects something of interest, it can be instructed to either issue a log entry or initiate the execution of an operating system command. Bro targets high-speed (Gbps), high-volume intrusion detection. By judiciously leveraging packet filtering techniques, Bro is able to achieve the performance necessary to do so while running on commercially available PC hardware, and thus can serve as a cost effective means of monitoring a site’s Internet connection.

  8. Application of ARMAV models to the identification and damage detection of mechanical and civil engineering structures

    NASA Astrophysics Data System (ADS)

    Bodeux, J. B.; Golinval, J. C.

    2001-06-01

    In this paper, the application of auto-regressive moving average vector models to system identification and damage detection is investigated. These parametric models have already been applied for the analysis of multiple input-output systems under ambient excitation. Their main advantage consists in the capability of extracting modal parameters from the recorded time signals, without the requirement of excitation measurement. The excitation is supposed to be a stationary Gaussian white noise. The method also allows the estimation of modal parameter uncertainties. On the basis of these uncertainties, a statistically based damage detection scheme is performed and it becomes possible to assess whether changes of modal parameters are caused by, e.g. some damage or simply by estimation inaccuracies. The paper reports first an example of identification and damage detection applied to a simulated system under random excitation. The `Steel-Quake' benchmark proposed in the framework of COST Action F3 `Structural Dynamics' is also analysed. This structure was defined by the Joint Research Centre in Ispra (Italy) to test steel building performance during earthquakes. The proposed method gives an excellent identification of frequencies and mode shapes, while damping ratios are estimated with less accuracy.

  9. Portable pathogen detection system

    DOEpatents

    Colston, Billy W.; Everett, Matthew; Milanovich, Fred P.; Brown, Steve B.; Vendateswaran, Kodumudi; Simon, Jonathan N.

    2005-06-14

    A portable pathogen detection system that accomplishes on-site multiplex detection of targets in biological samples. The system includes: microbead specific reagents, incubation/mixing chambers, a disposable microbead capture substrate, and an optical measurement and decoding arrangement. The basis of this system is a highly flexible Liquid Array that utilizes optically encoded microbeads as the templates for biological assays. Target biological samples are optically labeled and captured on the microbeads, which are in turn captured on an ordered array or disordered array disposable capture substrate and then optically read.

  10. [Preliminary research on insect damage detection in pecans using terahertz spectroscopy].

    PubMed

    Li, Bin; Wang, Ning; Zhang, Wei-Li; Zhao, Chun-Jiang; Zhang, Bao-Hua

    2014-05-01

    Pecan is an important nut in US, however, the inner insect influences pecan's quality a lot. To realize the nondestructive detection of insect damage in American pecans rapidly and efficiently, preliminary research on insect damage detection in pecans was conducted based on terahertz spectroscopy. Firstly, a set of native pecan nuts were collected and were manually sliced with a thickness of about 1, 2 and 3 mm and with a size of about 2 cm(length) X 1 cm(width) for every pecan nutmeat; Pecan shell and inner separator were also cut into the same size. Secondly, the absorption spectra of the nutmeat slices, shell, and inner separator were collected using THz time-domain spectroscopy (THz-TDS) developed by a group of researchers at Oklahoma State University, and the spectral characteristic of the slices was analyzed. Thirdly, the absorption spectra of the alive manduca sexta and dry pecan weevil were collected, and due to the high contents in the insects, very obvious spectral characteristics were found. Finally, the transmission experiment was conducted with the whole pecans. The results from the preliminary study show a potential application of THz technology for insect damage detection. This research provides a reference for further understanding terahertz and exploring sample preparation methods, test methods, data acquisition and optical parameters calculation methods, and developing nondestructive detection system for insect damage in American pecans based on terahertz technology. PMID:25095406

  11. Solar system fault detection

    DOEpatents

    Farrington, R.B.; Pruett, J.C. Jr.

    1984-05-14

    A fault detecting apparatus and method are provided for use with an active solar system. The apparatus provides an indication as to whether one or more predetermined faults have occurred in the solar system. The apparatus includes a plurality of sensors, each sensor being used in determining whether a predetermined condition is present. The outputs of the sensors are combined in a pre-established manner in accordance with the kind of predetermined faults to be detected. Indicators communicate with the outputs generated by combining the sensor outputs to give the user of the solar system and the apparatus an indication as to whether a predetermined fault has occurred. Upon detection and indication of any predetermined fault, the user can take appropriate corrective action so that the overall reliability and efficiency of the active solar system are increased.

  12. Solar system fault detection

    DOEpatents

    Farrington, Robert B.; Pruett, Jr., James C.

    1986-01-01

    A fault detecting apparatus and method are provided for use with an active solar system. The apparatus provides an indication as to whether one or more predetermined faults have occurred in the solar system. The apparatus includes a plurality of sensors, each sensor being used in determining whether a predetermined condition is present. The outputs of the sensors are combined in a pre-established manner in accordance with the kind of predetermined faults to be detected. Indicators communicate with the outputs generated by combining the sensor outputs to give the user of the solar system and the apparatus an indication as to whether a predetermined fault has occurred. Upon detection and indication of any predetermined fault, the user can take appropriate corrective action so that the overall reliability and efficiency of the active solar system are increased.

  13. Fractal mechanism for characterizing singularity of mode shape for damage detection

    SciTech Connect

    Cao, M. S.; Ostachowicz, W.; Bai, R. B.; Radzieński, M.

    2013-11-25

    Damage is an ordinary physical phenomenon jeopardizing structural safety; damage detection is an ongoing interdisciplinary issue. Waveform fractal theory has provided a promising resource for detecting damage in plates while presenting a concomitant problem: susceptibility to false features of damage. This study proposes a fractal dimension method based on affine transformation to address this problem. Physical experiments using laser measurement demonstrate that this method can substantially eliminate false features of damage and accurately identify complex cracks in plates, providing a fundamental mechanism that brings the merits of waveform fractal theory into full play in structural damage detection applications.

  14. Fish detection and classification system

    NASA Astrophysics Data System (ADS)

    Tidd, Richard A.; Wilder, Joseph

    2001-01-01

    Marine biologists traditionally determine the presence and quantities of different types of fish by dragging nets across the bottom, and examining their contents. This method, although accurate, kills the collected fish, damages their habitat, and consumes large quantities of resources. This paper presents an alternative, a machine vision system capable of determining the presence of fish species. Illumination presents a unique problem in this environment, and the design of an effective illumination system is discussed. The related issues of object orientation and measurement are also discussed and resolved. Capturing images of fish in murky water also presents challenges. An adaptive thresholding technique is required to appropriately segment the fish from the background in these images. Mode detection, and histogram analysis are useful tools in determining these localized thresholds. It is anticipated that this system, created in conjunction with the Rutgers Institute for Marine and Coastal Science, will effectively classify fish in the estuarine environment.

  15. Continuous dynamic monitoring of a lively footbridge for serviceability assessment and damage detection

    NASA Astrophysics Data System (ADS)

    Hu, Wei-Hua; Moutinho, Carlos; Caetano, Elsa; Magalhães, Filipe; Cunha, Álvaro

    2012-11-01

    This paper aims at analyzing the feasibility of applying a vibration based damage detection approach, based on Principal Components Analysis (PCA), to eliminate environmental effects using the large amount of high quality data continuously collected by the dynamic monitoring system of Pedro e Inês footbridge since 2007. Few works describe real data, regularly collected along several years by reliable continuous dynamic monitoring systems in bridge structures. One main contribution is to show a large difference between making academic research based on numerical simulations or limited experimental samples, and making validity tests of innovative procedures using large high quality databases collected in real structures. The monitoring system, installed with the only initial objective of checking the efficiency of vibration control devices used to mitigate lateral and vertical vibrations, was therefore further developed for research purposes by implementing LabVIEW based automated signal processing and output-only modal identification routines, that enabled the analysis of the correlation of modal estimates with the temperature and the vibration level, as well as the automatic tracking of modal parameters along several years. With the final purpose of detecting potential structural damage at an early stage, the Principal Components Analysis (PCA) was employed to effectively eliminate temperature effects, whereas Novelty Analysis on the residual errors of the PCA model was used to provide a statistical indication of damage. The efficiency of this vibration based damage detection approach was verified using 3 years of measurements at Pedro e Inês footbridge under operational conditions and simulating several realistic damage scenarios affecting the boundary conditions. It is demonstrated that such a dynamic monitoring system, apart from providing relevant instantaneous dynamic information, working as an alert system associated to the verification of vibration

  16. Embedded transmissibility function analysis for damage detection in a mobile sensor network

    NASA Astrophysics Data System (ADS)

    Yi, Xiaohua; Zhu, Dapeng; Wang, Yang; Guo, Jiajie; Lee, Kok-Meng

    2010-04-01

    Structural health monitoring (SHM) and damage detection have attracted great interest in recent decades, in meeting the challenges of assessing the safety condition of large-scale civil structures. By wiring remote sensors directly to a centralized data acquisition system, traditional structural health monitoring systems are usually costly and the installation is time-consuming. Recent advances in wireless sensing technology have made it feasible for structural health monitoring; furthermore, the computational core in a wireless sensing unit offers onboard data interrogation. In addition to wireless sensing, the authors have recently developed a mobile sensing system for providing high spatial resolution and flexible sensor deployment in structural health monitoring. In this study, transmissibility function analysis is embedded in the mobile sensing node to perform onboard and in-network structural damage detection. The system implementation is validated using a laboratory 2D steel portal frame. Simulated damage is applied to the frame structure, and the damage is successfully identified by two mobile sensing nodes that autonomously navigate through the structure.

  17. Damage detection under varying environmental and operational conditions using Wavelet Transform Modulus Maxima decay lines similarity

    NASA Astrophysics Data System (ADS)

    Tjirkallis, A.; Kyprianou, A.

    2016-01-01

    Over the last three decades, there have been increasing demands to develop and deploy Structural Health Monitoring (SHM) systems for engineering structures in service. Since these structures are subjected to varying environmental and operational conditions, reliable SHM methodologies must be capable of not misattributing to damage changes due to environmental conditions. This paper presents a novel damage detection methodology based on the similarity between maxima decay lines of the continuous wavelet transform scalogram of the structural responses obtained under different operational and environmental conditions. The normalized cross correlation (NCC) is used as a measure of this similarity. In addition, the pointwise summation of similar Wavelet Transform Modulus Maxima (WTMM) decay lines is used to identify changes due to the presence of damage from different force realizations and/or varying environmental conditions. The effectiveness of the proposed methodology is demonstrated using a simulated 3DOF system and an experimental cantilever beam.

  18. Idaho Explosives Detection System

    SciTech Connect

    Edward L. Reber; Larry G. Blackwood; Andrew J. Edwards; J. Keith Jewell; Kenneth W. Rohde; Edward H. Seabury; Jeffery B. Klinger

    2005-12-01

    The Idaho Explosives Detection System was developed at the Idaho National Laboratory (INL) to respond to threats imposed by delivery trucks potentially carrying explosives into military bases. A full-scale prototype system has been built and is currently undergoing testing. The system consists of two racks, one on each side of a subject vehicle. Each rack includes a neutron generator and an array of NaI detectors. The two neutron generators are pulsed and synchronized. A laptop computer controls the entire system. The control software is easily operable by minimally trained staff. The system was developed to detect explosives in a medium size truck within a 5-min measurement time. System performance was successfully demonstrated with explosives at the INL in June 2004 and at Andrews Air Force Base in July 2004.

  19. Damage detection by Acousto-Ultrasonic Location (AUL)

    NASA Astrophysics Data System (ADS)

    Marioli-Riga, Z. P.; Karanika, A. N.; Philippidis, T. P.; Paipetis, S. A.

    1992-12-01

    Damage detection in aircraft structures in-situ is important, especially with not visible defects in composite components for a variety of reasons. In the present paper a new technique based on the Acousto-Ultrasonic (AU) concept is introduced, but instead of extracting information from the externally generated pulsed wave, as with AU, the characteristics of waves reflected from defects are measured. In this way it was possible to identify and locate defected areas in honeycomb panels and thermoplastic carbon fiber laminates. The results were correlated with ultrasonic C-scans, and satisfactory agreement was obtained. The present is part of a major project aiming at the development of a fast inspection method for aircraft components during routine maintenance cycles.

  20. Detection and location of debris cloud impact damage

    NASA Astrophysics Data System (ADS)

    Zhang, Kai; Pang, Baojun; Liu, Zhidong; Chi, Runqiang

    2009-12-01

    A variety of anomalies and system failure can be caused by micrometeoroid and space debris impact on spacecraft. A system based on acoustic emission technique is considered for monitoring the impact events. Most of recent works focused on point-like source localization. However, the spacecraft may use a single thin plate named "bumper" placed at a short distance ahead of a primary structural system. The impact source would be in the form of debris cloud. In this study, normal hypervelocity impact experiments were used to study the characteristics of signals caused by debris cloud impact. Four ultrasonic transducers were mounted on the target plate for collecting the debris cloud impact signals. In the Fourier transform of the signals, the distinctions caused by different form of debris cloud impact could be seen. The mathematical model to determine the impact location was provided. It was found that the position predicted was near the center of the damaged region caused by debris cloud impact.

  1. Detection and location of debris cloud impact damage

    NASA Astrophysics Data System (ADS)

    Zhang, Kai; Pang, Baojun; Liu, ZhiDong; Chi, Runqiang

    2010-03-01

    A variety of anomalies and system failure can be caused by micrometeoroid and space debris impact on spacecraft. A system based on acoustic emission technique is considered for monitoring the impact events. Most of recent works focused on point-like source localization. However, the spacecraft may use a single thin plate named "bumper" placed at a short distance ahead of a primary structural system. The impact source would be in the form of debris cloud. In this study, normal hypervelocity impact experiments were used to study the characteristics of signals caused by debris cloud impact. Four ultrasonic transducers were mounted on the target plate for collecting the debris cloud impact signals. In the Fourier transform of the signals, the distinctions caused by different form of debris cloud impact could be seen. The mathematical model to determine the impact location was provided. It was found that the position predicted was near the center of the damaged region caused by debris cloud impact.

  2. Nondestructive detection of damage in carbon fibre composites by SQUID magnetometry

    NASA Astrophysics Data System (ADS)

    Ruosi, A.

    2005-03-01

    Monitoring of structural integrity is an essential issue in enhancing the affordability as well the safety of modern aircraft and spacecraft structures. Increasingly, metallic parts of aircrafts are being replaced by carbon fibre composite components due to their high strength and stiffness combined with low density. This paper reviews of the use of superconducting quantum interference devices (SQUIDs) in the detection of different types of damage in carbon fibre panels. The results presented here on impact damage on carbon fibre reinforced polymer and cracks induced by tensile loads on carbon fibre reinforced carbon matrix show that this method is sensitive not only to the presence but also the severity of damage. Indeed, it enables one to distinguish between the different failure mechanisms as the damage process evolves. SQUIDs response to artificial delaminations, flaws and deep-lying defects are also presented. The application of a neural network system for the detection of impact damage in a noisy environment is discussed. Experimental results demonstrate that nondestructive evaluation using SQUID magnetometers is a suitable technique to investigate composites to improve their mechanical properties.

  3. Damage detection tomography based on guided waves in composite structures using a distributed sensor network

    NASA Astrophysics Data System (ADS)

    Memmolo, Vittorio; Maio, Leandro; Boffa, Natalino Daniele; Monaco, Ernesto; Ricci, Fabrizio

    2016-01-01

    Structural health monitoring (SHM) based on guided waves allows assessing the health of a structure due to the sensitivity to the occurrence of delamination. However, wave propagation presents several complexities for effective damage identification in composite structures. An efficient implementation of a guided wave-based SHM system requires an accurate analysis of collected data to obtain a useful detection. This paper is concerned with the identification of small emerging delaminations in composite structural components using a sparse array of surface ultrasonic transducers. An ultrasonic-guided wave tomography technique focused on impact damage detection in composite plate-like structures is presented. A statistical damage index approach is adopted to interpret the recorded signals, and a subsequent graphic interpolation is implemented to reconstruct the damage appearance. Experimental tests carried out on a typical composite structure demonstrated the effectiveness of the developed technique with the aim to investigate the presence and location of damage using simple imaging reports and a limited number of measurements. A traditional ultrasonic inspection (C-scan) is used to assess the methodology.

  4. Water system virus detection

    NASA Technical Reports Server (NTRS)

    Fraser, A. S.; Wells, A. F.; Tenoso, H. J.

    1975-01-01

    A monitoring system developed to test the capability of a water recovery system to reject the passage of viruses into the recovered water is described. A nonpathogenic marker virus, bacteriophage F2, is fed into the process stream before the recovery unit and the reclaimed water is assayed for its presence. Detection of the marker virus consists of two major components, concentration and isolation of the marker virus, and detection of the marker virus. The concentration system involves adsorption of virus to cellulose acetate filters in the presence of trivalent cations and low pH with subsequent desorption of the virus using volumes of high pH buffer. The detection of the virus is performed by a passive immune agglutination test utilizing specially prepared polystyrene particles. An engineering preliminary design was performed as a parallel effort to the laboratory development of the marker virus test system. Engineering schematics and drawings of a fully functional laboratory prototype capable of zero-G operation are presented. The instrument consists of reagent pump/metering system, reagent storage containers, a filter concentrator, an incubation/detector system, and an electronic readout and control system.

  5. Extended Kalman filter based structural damage detection for MR damper controlled structures

    NASA Astrophysics Data System (ADS)

    Jin, Chenhao; Jang, Shinae; Sun, Xiaorong; Jiang, Zhaoshuo; Christenson, Richard

    2016-04-01

    The Magneto-rheological (MR) dampers have been widely used in many building and bridge structures against earthquake and wind loadings due to its advantages including mechanical simplicity, high dynamic range, low power requirements, large force capacity, and robustness. However, research about structural damage detection methods for MR damper controlled structures is limited. This paper aims to develop a real-time structural damage detection method for MR damper controlled structures. A novel state space model of MR damper controlled structure is first built by combining the structure's equation of motion and MR damper's hyperbolic tangent model. In this way, the state parameters of both the structure and MR damper are added in the state vector of the state space model. Extended Kalman filter is then used to provide prediction for state variables from measurement data. The two techniques are synergistically combined to identify parameters and track the changes of both structure and MR damper in real time. The proposed method is tested using response data of a three-floor MR damper controlled linear building structure under earthquake excitation. The testing results show that the adaptive extended Kalman filter based approach is capable to estimate not only structural parameters such as stiffness and damping of each floor, but also the parameters of MR damper, so that more insights and understanding of the damage can be obtained. The developed method also demonstrates high damage detection accuracy and light computation, as well as the potential to implement in a structural health monitoring system.

  6. A microsuspension adaptation of the Bacillus subtilis ''rec'' assay. [Detection of chemically induced DNA damage

    SciTech Connect

    McCarroll, N.E.; Keech, B.H.; Piper, C.E.

    1981-01-01

    We have demonstrated the utility of an Escherichia coli microsuspension assay to detect and characterize chemical mediation of DNA damage by a wide variety of mutagens and carcinogens. The assay have been improved by the development of a microsuspension modification to the Bacillus subtilis ''rec'' assay. The addition of these gram-positive organisms has allowed detection of DNA damage induced by benzo(a)pyrene (B(a)P), 3-aminopyrene (3-AP), 7, 12-dimethylbenz(a)anthrancene (DMBA), 3-methylcholanthrene (3-MC), and 4-nitrobiphenyl (4-NBP). Data presented in this paper from tests of 61 additional compounds, including a representative number of direct and promutagenic agents, indicate that the B subtilis H17 and M45 strains provide an effective microbial system for identification of DNA damage susceptible to postreplicational repair. The results of this study further suggests that the inclusion of these strains in the microsuspension assay for DNA damage will markedly enhance the detection of agents which cannot readily penetrate the intact cell wall of E coli.

  7. Research on fatigue damage detection for wind turbine blade based on high-spatial-resolution DPP-BOTDA

    NASA Astrophysics Data System (ADS)

    Xu, Jinlong; Dong, Yongkang; Li, Hui

    2014-03-01

    In this paper, a fatigue damage detection system used for wind turbine blade is successfully developed by using highspatial- resolution differential pulse-width pair Brillouin optical time-domain analysis (DPP-BOTDA) sensing system. A piece of polarization-maintaining optical fiber is bonded on the blade surface to form the distributed sensing network. A DPP-BOTDA system, with a spatial resolution of 20cm and sampling interval of 1cm, is adopted to measuring distributed strain and detecting fatigue damage of wind turbine blade during fatigue test using the differential pulse pair of 39.5ns/41.5ns. Strain and the Brillouin gain spectra changes from undamaged state to fatigue failure are experimentally presented. The experimental results reveal that fatigue damage changes the strain distribution especially around the high strain area, and the width, amplitude and central frequency of the Brillouin gain spectra are sensitive to fatigue damage as the stiffness degradation and accumulated cracks change local strain gradient. As the damage becomes larger, the width of the Brillouin gain spectra becomes broader. Consequently, location and size of fatigue damage could be estimated. The developed system shows its potentiality for developing highly reliable wind turbine monitoring system as the effectiveness of damage detection and distributed sensing.

  8. TECHNICAL NOTE: An unsupervised statistical damage detection method for structural health monitoring (applied to detection of delamination of a composite beam)

    NASA Astrophysics Data System (ADS)

    Iwasaki, Atsushi; Todoroki, Akira; Shimamura, Yoshinobu; Kobayashi, Hideo

    2004-10-01

    The present paper proposes a new damage diagnosis method for structural health monitoring that does not require data on damaged-state structures. Structural health monitoring is an essential technology for aged civil structures and advanced composite structures. For damage diagnostic methods, most current structural health monitoring systems adopt parametric methods based on modeling, or non-parametric methods such as artificial neural networks. The conventional methods require FEM modeling of structure or data for training the damaged-state structure. These processes require judgment by a human, resulting in high cost. The present paper proposes a new automatic damage diagnostic method for structural health monitoring that does not require these processes by using a system identification and statistical similarity test of the identified systems using an F-test. As an example of damage diagnosis using the new method, the present study describes delamination detection of a CFRP beam. System identification among the strain data measured on the surface of a composite beam is used for damage diagnosis. The results show that the new statistical damage diagnostic method successfully diagnoses damage without the use of modeling and without learning data for damaged structures.

  9. Bro Intrusion Detection System

    Energy Science and Technology Software Center (ESTSC)

    2006-01-25

    Bro is a Unix-based Network Intrusion Detection System (IDS). Bro monitors network traffic and detects intrusion attempts based on the traffic characteristics and content. Bro detects intrusions by comparing network traffic against rules describing events that are deemed troublesome. These rules might describe activities (e.g., certain hosts connecting to certain services), what activities are worth alerting (e.g., attempts to a given number of different hosts constitutes a "scan"), or signatures describing known attacks or accessmore » to known vulnerabilities. If Bro detects something of interest, it can be instructed to either issue a log entry or initiate the execution of an operating system command. Bro targets high-speed (Gbps), high-volume intrusion detection. By judiciously leveraging packet filtering techniques, Bro is able to achieve the performance necessary to do so while running on commercially available PC hardware, and thus can serve as a cost effective means of monitoring a site’s Internet connection.« less

  10. Application of electromechanical impedance-based SHM for damage detection in bolted pipeline connection

    NASA Astrophysics Data System (ADS)

    Martowicz, Adam; Sendecki, Arkadiusz; Salamon, Marcin; Rosiek, Mateusz; Uhl, Tadeusz

    2016-01-01

    The work discusses the effectiveness of the electromechanical impedance-based Structural Health Monitoring system for damage detection in a laboratory test stand - a bolted pipeline section. The impedance-based system developed by the authors and equipped with 12 piezoelectric transducers was used to acquire the data. Different damage scenarios related to loosened bolts and measurement configurations are analysed. Both point and transfer frequency response functions are applied to deterministic and stochastic damage metrics, which are used to assess the condition of the monitored structure. The thresholds levels are proposed for different measurement configurations. Moreover, the authors discuss the perspective to determine the size and localisation of a damage. As confirmed in the work, the stochastic damage metric, preferably applied with a transfer frequency response, is found as of the most practical significance for the tested structure. The carried out analyses consider an outlier removal technique, which becomes necessary to prevent from errors due to temporary variation of the acquired characteristics after initialisation of the measurements.

  11. Corticosteroids: do they damage the cardiovascular system?

    PubMed Central

    Maxwell, S. R.; Moots, R. J.; Kendall, M. J.

    1994-01-01

    Since their introduction for the treatment of rheumatoid arthritis, corticosteroids have become widely used as effective agents in the control of inflammatory diseases. Although there have been undoubted benefits upon mortality in diseases such as systemic lupus erythematosus, many patients survive only to suffer a high incidence of premature atherosclerosis. There is also evidence of increased rates of vascular mortality in other corticosteroid-treated diseases, such as rheumatoid arthritis, reversible airways obstruction and transplant recipients. Possible mechanisms of damage include elevated blood pressure, impaired glucose tolerance, dyslipidaemia, and imbalances in thrombosis and fibrinolysis. This paper reviews the clinical evidence supporting the contention that there is an excess cardiovascular mortality in steroid-treated patients and the underlying mechanisms, and points to further areas of research. PMID:7870631

  12. Towards damage detection using blind source separation integrated with time-varying auto-regressive modeling

    NASA Astrophysics Data System (ADS)

    Musafere, F.; Sadhu, A.; Liu, K.

    2016-01-01

    In the last few decades, structural health monitoring (SHM) has been an indispensable subject in the field of vibration engineering. With the aid of modern sensing technology, SHM has garnered significant attention towards diagnosis and risk management of large-scale civil structures and mechanical systems. In SHM, system identification is one of major building blocks through which unknown system parameters are extracted from vibration data of the structures. Such system information is then utilized to detect the damage instant, and its severity to rehabilitate and prolong the existing health of the structures. In recent years, blind source separation (BSS) algorithm has become one of the newly emerging advanced signal processing techniques for output-only system identification of civil structures. In this paper, a novel damage detection technique is proposed by integrating BSS with the time-varying auto-regressive modeling to identify the instant and severity of damage. The proposed method is validated using a suite of numerical studies and experimental models followed by a full-scale structure.

  13. Radiation detection system

    DOEpatents

    Nelson, Melvin A.; Davies, Terence J.; Morton, III, John R.

    1976-01-01

    A radiation detection system which utilizes the generation of Cerenkov light in and the transmission of that light longitudinally through fiber optic wave guides in order to transmit intelligence relating to the radiation to a remote location. The wave guides are aligned with respect to charged particle radiation so that the Cerenkov light, which is generated at an angle to the radiation, is accepted by the fiber for transmission therethrough. The Cerenkov radiation is detected, recorded, and analyzed at the other end of the fiber.

  14. Eddy Current System and Method for Crack Detection

    NASA Technical Reports Server (NTRS)

    Wincheski, Russell A. (Inventor); Simpson, John W. (Inventor)

    2012-01-01

    An eddy current system and method enables detection of sub-surface damage in a cylindrical object. The invention incorporates a dual frequency, orthogonally wound eddy current probe mounted on a stepper motor-controlled scanning system. The system is designed to inspect for outer surface damage from the interior of the cylindrical object.

  15. Detection of Ballast Damage by In-Situ Vibration Measurement of Sleepers

    NASA Astrophysics Data System (ADS)

    Lam, H. F.; Wong, M. T.; Keefe, R. M.

    2010-05-01

    Ballasted track is one of the most important elements of railway transportation systems worldwide. Owing to its importance in railway safety, many monitoring and evaluation methods have been developed. Current railway track monitoring systems are comprehensive, fast and efficient in testing railway track level and alignment, rail gauge, rail corrugation, etc. However, the monitoring of ballast condition still relies very much on visual inspection and core tests. Although extensive research has been carried out in the development of non-destructive methods for ballast condition evaluation, a commonly accepted and cost-effective method is still in demand. In Hong Kong practice, if abnormal train vibration is reported by the train operator or passengers, permanent way inspectors will locate the problem area by track geometry measurement. It must be pointed out that visual inspection can only identify ballast damage on the track surface, the track geometry deficiencies and rail twists can be detected using a track gauge. Ballast damage under the sleeper loading area and the ballast shoulder, which are the main factors affecting track stability and ride quality, are extremely difficult if not impossible to be detected by visual inspection. Core test is a destructive test, which is expensive, time consuming and may be disruptive to traffic. A fast real-time ballast damage detection method that can be implemented by permanent way inspectors with simple equipment can certainly provide valuable information for engineers in assessing the safety and riding quality of ballasted track systems. The main objective of this paper is to study the feasibility in using the vibration characteristics of sleepers in quantifying the ballast condition under the sleepers, and so as to explore the possibility in developing a handy method for the detection of ballast damage based on the measured vibration of sleepers.

  16. A procedure for damage detection and localization of framed buildings based on curvature variation

    NASA Astrophysics Data System (ADS)

    Ditommaso, Rocco; Carlo Ponzo, Felice; Auletta, Gianluca; Iacovino, Chiara; Mossucca, Antonello; Nigro, Domenico; Nigro, Antonella

    2014-05-01

    Structural Health Monitoring and Damage Detection are topics of current interest in civil, mechanical and aerospace engineering. Damage Detection approach based on dynamic monitoring of structural properties over time has received a considerable attention in recent scientific literature of the last years. The basic idea arises from the observation that spectral properties, described in terms of the so-called modal parameters (eigenfrequencies, mode shapes, and modal damping), are functions of the physical properties of the structure (mass, energy dissipation mechanisms and stiffness). Structural damage exhibits its main effects in terms of stiffness and damping variation. As a consequence, a permanent dynamic monitoring system makes it possible to detect and, if suitably concentrated on the structure, to localize structural and non-structural damage occurred on the structure during a strong earthquake. In the last years many researchers are working to set-up new methodologies for Non-destructive Damage Evaluation (NDE) based on the variation of the dynamic behaviour of structures under seismic loads. Pandey et al. (1991) highlighted on the possibility to use the structural mode shapes to extract useful information for structural damage localization. In this paper a new procedure for damage detection on framed structures based on changes in modal curvature is proposed. The proposed approach is based on the use of Stockwell Transform, a special kind of integral transformation that become a powerful tool for nonlinear signal analysis and then to analyse the nonlinear behaviour of a general structure. Using this kind of approach, it is possible to use a band-variable filter (Ditommaso et al., 2012) to extract from a signal recorded on a structure (excited by an earthquake) the response related to a single mode of vibration for which the related frequency changes over time (if the structure is being damaged). İn general, by acting simultaneously in both frequency and

  17. Open Circuit Resonant (SansEC) Sensor for Composite Damage Detection and Diagnosis in Aircraft Lightning Environments

    NASA Technical Reports Server (NTRS)

    Wang, Chuantong; Dudley, Kenneth L.; Szatkowski, George N.

    2012-01-01

    Composite materials are increasingly used in modern aircraft for reducing weight, improving fuel efficiency, and enhancing the overall design, performance, and manufacturability of airborne vehicles. Materials such as fiberglass reinforced composites (FRC) and carbon-fiber-reinforced polymers (CFRP) are being used to great advantage in airframes, wings, engine nacelles, turbine blades, fairings, fuselage and empennage structures, control surfaces and coverings. However, the potential damage from the direct and indirect effects of lightning strikes is of increased concern to aircraft designers and operators. When a lightning strike occurs, the points of attachment and detachment on the aircraft surface must be found by visual inspection, and then assessed for damage by maintenance personnel to ensure continued safe flight operations. In this paper, a new method and system for aircraft in-situ damage detection and diagnosis are presented. The method and system are based on open circuit (SansEC) sensor technology developed at NASA Langley Research Center. SansEC (Sans Electric Connection) sensor technology is a new technical framework for designing, powering, and interrogating sensors to detect damage in composite materials. Damage in composite material is generally associated with a localized change in material permittivity and/or conductivity. These changes are sensed using SansEC. Unique electrical signatures are used for damage detection and diagnosis. NASA LaRC has both experimentally and theoretically demonstrated that SansEC sensors can be effectively used for in-situ composite damage detection.

  18. How damage diversification can reduce systemic risk

    NASA Astrophysics Data System (ADS)

    Burkholz, Rebekka; Garas, Antonios; Schweitzer, Frank

    2016-04-01

    We study the influence of risk diversification on cascading failures in weighted complex networks, where weighted directed links represent exposures between nodes. These weights result from different diversification strategies and their adjustment allows us to reduce systemic risk significantly by topological means. As an example, we contrast a classical exposure diversification (ED) approach with a damage diversification (DD) variant. The latter reduces the loss that the failure of high degree nodes generally inflict to their network neighbors and thus hampers the cascade amplification. To quantify the final cascade size and obtain our results, we develop a branching process approximation taking into account that inflicted losses cannot only depend on properties of the exposed, but also of the failing node. This analytic extension is a natural consequence of the paradigm shift from individual to system safety. To deepen our understanding of the cascade process, we complement this systemic perspective by a mesoscopic one: an analysis of the failure risk of nodes dependent on their degree. Additionally, we ask for the role of these failures in the cascade amplification.

  19. Damage detection for beam-like structures using the normalized curvature of a uniform load surface

    NASA Astrophysics Data System (ADS)

    Sung, S. H.; Jung, H. J.; Jung, H. Y.

    2013-03-01

    This paper presents a new vibration-based damage detection method for beam-like structures that uses the normalized uniform load surface (NULS) curvature obtained by modal flexibility. Analytical studies on the NULS curvature method for beam-like structures, which follow Bernoulli-Euler beam theory, have shown that changes in NULS curvature only occur at damaged elements and not at intact ones because the internal forces induced by damage only act on the damaged elements and not on the undamaged elements. Therefore, computing the changes in NULS curvature set indicating only damaged elements at a normalized level is central to the approach. Also, a damage index is proposed based on outlier analysis to account for measurement noise. In order to confirm the feasibility of the proposed method, a cantilever beam and a simply supported beam were numerically investigated for two damage scenarios by using modal parameters obtained by eigenvalue analysis and simulations of an impact test using MATLAB/Simulink. The results showed that the proposed method could accurately localize multiple damage locations as well as single damage locations without any false-positive or false-negative detections. For comparison, damage detection was also conducted using the uniform load surface (ULS) curvature method and the mode shape curvature method. The ULS curvature method clearly identified single damage locations but some missed multiple damage locations. For the mode shape curvature method, it was shown that the false-positive and false-negative detections were performed at several damaged or undamaged locations. The comparison showed that the proposed detection method can more effectively identify single and multiple damage locations than the other two methods. In conclusion, the proposed method performed better in detecting damages than the other two methods in terms of sensitivity to damage regardless of location and robustness against noisy signals generated from calculating the

  20. Acoustic damage detection in laser-cut CFRP composite materials

    NASA Astrophysics Data System (ADS)

    Nishino, Michiteru; Harada, Yoshihisa; Suzuki, Takayuki; Niino, Hiroyuki

    2012-03-01

    Carbon fiber reinforced plastics (CFRP) composite material, which is expected to reduce the weight of automotive, airplane and etc., was cut by laser irradiation with a pulsed-CO2 laser (TRUMPF TFL5000; P=800W, 20kHz, τ=8μs, λ=10.6μm, V=1m/min) and single-mode fiber lasers (IPG YLR-300-SM; P=300W, λ=1.07μm, V=1m/min)(IPG YLR- 2000-SM; P=2kW, λ=1.07μm, V=7m/min). To detect thermal damage at the laser cutting of CFRP materials consisting of thermoset resin matrix and PAN or PITCH-based carbon fiber, the cut quality was observed by X-ray CT. The effect of laser cutting process on the mechanical strength for CFRP tested at the tensile test. Acoustic emission (AE) monitoring, high-speed camera and scanning electron microscopy were used for the failure process analysis. AE signals and fractographic features characteristic of each laser-cut CFRP were identified.

  1. Damage detection technique by measuring laser-based mechanical impedance

    SciTech Connect

    Lee, Hyeonseok; Sohn, Hoon

    2014-02-18

    This study proposes a method for measurement of mechanical impedance using noncontact laser ultrasound. The measurement of mechanical impedance has been of great interest in nondestructive testing (NDT) or structural health monitoring (SHM) since mechanical impedance is sensitive even to small-sized structural defects. Conventional impedance measurements, however, have been based on electromechanical impedance (EMI) using contact-type piezoelectric transducers, which show deteriorated performances induced by the effects of a) Curie temperature limitations, b) electromagnetic interference (EMI), c) bonding layers and etc. This study aims to tackle the limitations of conventional EMI measurement by utilizing laser-based mechanical impedance (LMI) measurement. The LMI response, which is equivalent to a steady-state ultrasound response, is generated by shooting the pulse laser beam to the target structure, and is acquired by measuring the out-of-plane velocity using a laser vibrometer. The formation of the LMI response is observed through the thermo-mechanical finite element analysis. The feasibility of applying the LMI technique for damage detection is experimentally verified using a pipe specimen under high temperature environment.

  2. Damage detection technique by measuring laser-based mechanical impedance

    NASA Astrophysics Data System (ADS)

    Lee, Hyeonseok; Sohn, Hoon

    2014-02-01

    This study proposes a method for measurement of mechanical impedance using noncontact laser ultrasound. The measurement of mechanical impedance has been of great interest in nondestructive testing (NDT) or structural health monitoring (SHM) since mechanical impedance is sensitive even to small-sized structural defects. Conventional impedance measurements, however, have been based on electromechanical impedance (EMI) using contact-type piezoelectric transducers, which show deteriorated performances induced by the effects of a) Curie temperature limitations, b) electromagnetic interference (EMI), c) bonding layers and etc. This study aims to tackle the limitations of conventional EMI measurement by utilizing laser-based mechanical impedance (LMI) measurement. The LMI response, which is equivalent to a steady-state ultrasound response, is generated by shooting the pulse laser beam to the target structure, and is acquired by measuring the out-of-plane velocity using a laser vibrometer. The formation of the LMI response is observed through the thermo-mechanical finite element analysis. The feasibility of applying the LMI technique for damage detection is experimentally verified using a pipe specimen under high temperature environment.

  3. An automatic damage detection algorithm based on the Short Time Impulse Response Function

    NASA Astrophysics Data System (ADS)

    Auletta, Gianluca; Carlo Ponzo, Felice; Ditommaso, Rocco; Iacovino, Chiara

    2016-04-01

    Structural Health Monitoring together with all the dynamic identification techniques and damage detection techniques are increasing in popularity in both scientific and civil community in last years. The basic idea arises from the observation that spectral properties, described in terms of the so-called modal parameters (eigenfrequencies, mode shapes, and modal damping), are functions of the physical properties of the structure (mass, energy dissipation mechanisms and stiffness). Damage detection techniques traditionally consist in visual inspection and/or non-destructive testing. A different approach consists in vibration based methods detecting changes of feature related to damage. Structural damage exhibits its main effects in terms of stiffness and damping variation. Damage detection approach based on dynamic monitoring of structural properties over time has received a considerable attention in recent scientific literature. We focused the attention on the structural damage localization and detection after an earthquake, from the evaluation of the mode curvature difference. The methodology is based on the acquisition of the structural dynamic response through a three-directional accelerometer installed on the top floor of the structure. It is able to assess the presence of any damage on the structure providing also information about the related position and severity of the damage. The procedure is based on a Band-Variable Filter, (Ditommaso et al., 2012), used to extract the dynamic characteristics of systems that evolve over time by acting simultaneously in both time and frequency domain. In this paper using a combined approach based on the Fourier Transform and on the seismic interferometric analysis, an useful tool for the automatic fundamental frequency evaluation of nonlinear structures has been proposed. Moreover, using this kind of approach it is possible to improve some of the existing methods for the automatic damage detection providing stable results

  4. A novel damage index for fatigue damage detection in a laminated composites using Lamb waves

    NASA Astrophysics Data System (ADS)

    Seki, Daigo

    A well-established structural health monitoring (SHM) technique, the Lamb wave based approach, is used for fatigue damage identification in a laminated composite. A novel damage index, 'normalized correlation moment' (NCM) which is composed of the nth moment of the cross correlation of the baseline and comparison waves, was used as damage index for monitoring damage in composites and compared with the signal difference coefficient (SDC) which is one of the most commonly used damage indices. Composite specimens were fabricated by the hand layup method by followed by compression. Piezo electric disks mounted on composite specimens were used as actuators and sensors. Three point bending fatigue tests were carried out on an intact composite laminate and a delaminated composite laminate with [06/904/06] orientation. Finite element analysis was performed to test the validity of SDC and NCM for fatigue damage.

  5. Wireless ultrasonic wavefield imaging via laser for hidden damage detection inside a steel box girder bridge

    NASA Astrophysics Data System (ADS)

    An, Yun-Kyu; Song, Homin; Sohn, Hoon

    2014-09-01

    This paper presents a wireless ultrasonic wavefield imaging (WUWI) technique for detecting hidden damage inside a steel box girder bridge. The proposed technique allows (1) complete wireless excitation of piezoelectric transducers and noncontact sensing of the corresponding responses using laser beams, (2) autonomous damage visualization without comparing against baseline data previously accumulated from the pristine condition of a target structure and (3) robust damage diagnosis even for real structures with complex structural geometries. First, a new WUWI hardware system was developed by integrating optoelectronic-based signal transmitting and receiving devices and a scanning laser Doppler vibrometer. Next, a damage visualization algorithm, self-referencing f-k filter (SRF), was introduced to isolate and visualize only crack-induced ultrasonic modes from measured ultrasonic wavefield images. Finally, the performance of the proposed technique was validated through hidden crack visualization at a decommissioned Ramp-G Bridge in South Korea. The experimental results reveal that the proposed technique instantaneously detects and successfully visualizes hidden cracks even in the complex structure of a real bridge.

  6. Online Damage Detection on Metal and Composite Space Structures by Active and Passive Acoustic Methods

    NASA Astrophysics Data System (ADS)

    Scheerer, M.; Cardone, T.; Rapisarda, A.; Ottaviano, S.; Ftancesconi, D.

    2012-07-01

    In the frame of ESA funded programme Future Launcher Preparatory Programme Period 1 “Preparatory Activities on M&S”, Aerospace & Advanced Composites and Thales Alenia Space-Italia, have conceived and tested a structural health monitoring approach based on integrated Acoustic Emission - Active Ultrasound Damage Identification. The monitoring methods implemented in the study are both passive and active methods and the purpose is to cover large areas with a sufficient damage size detection capability. Two representative space sub-structures have been built and tested: a composite overwrapped pressure vessel (COPV) and a curved, stiffened Al-Li panel. In each structure, typical critical damages have been introduced: delaminations caused by impacts in the COPV and a crack in the stiffener of the Al-Li panel which was grown during a fatigue test campaign. The location and severity of both types of damages have been successfully assessed online using two commercially available systems: one 6 channel AE system from Vallen and one 64 channel AU system from Acellent.

  7. Ultrasonic Leak Detection System

    NASA Technical Reports Server (NTRS)

    Youngquist, Robert C. (Inventor); Moerk, J. Steven (Inventor)

    1998-01-01

    A system for detecting ultrasonic vibrations. such as those generated by a small leak in a pressurized container. vessel. pipe. or the like. comprises an ultrasonic transducer assembly and a processing circuit for converting transducer signals into an audio frequency range signal. The audio frequency range signal can be used to drive a pair of headphones worn by an operator. A diode rectifier based mixing circuit provides a simple, inexpensive way to mix the transducer signal with a square wave signal generated by an oscillator, and thereby generate the audio frequency signal. The sensitivity of the system is greatly increased through proper selection and matching of the system components. and the use of noise rejection filters and elements. In addition, a parabolic collecting horn is preferably employed which is mounted on the transducer assembly housing. The collecting horn increases sensitivity of the system by amplifying the received signals. and provides directionality which facilitates easier location of an ultrasonic vibration source.

  8. Water system virus detection

    NASA Technical Reports Server (NTRS)

    Fraser, A. S.; Wells, A. F.; Tenoso, H. J. (Inventor)

    1978-01-01

    The performance of a waste water reclamation system is monitored by introducing a non-pathogenic marker virus, bacteriophage F2, into the waste-water prior to treatment and, thereafter, testing the reclaimed water for the presence of the marker virus. A test sample is first concentrated by absorbing any marker virus onto a cellulose acetate filter in the presence of a trivalent cation at low pH and then flushing the filter with a limited quantity of a glycine buffer solution to desorb any marker virus present on the filter. Photo-optical detection of indirect passive immune agglutination by polystyrene beads indicates the performance of the water reclamation system in removing the marker virus. A closed system provides for concentrating any marker virus, initiating and monitoring the passive immune agglutination reaction, and then flushing the system to prepare for another sample.

  9. Seismic response and damage detection analyses of an instrumented steel moment-framed building

    USGS Publications Warehouse

    Rodgers, J.E.; Celebi, M.

    2006-01-01

    The seismic performance of steel moment-framed buildings has been of particular interest since brittle fractures were discovered at the beam-column connections in a number of buildings following the M 6.7 Northridge earthquake of January 17, 1994. A case study of the seismic behavior of an extensively instrumented 13-story steel moment frame building located in the greater Los Angeles area of California is described herein. Response studies using frequency domain, joint time-frequency, system identification, and simple damage detection analyses are performed using an extensive strong motion dataset dating from 1971 to the present, supported by engineering drawings and results of postearthquake inspections. These studies show that the building's response is more complex than would be expected from its highly symmetrical geometry. The response is characterized by low damping in the fundamental mode, larger accelerations in the middle and lower stories than at the roof and base, extended periods of vibration after the cessation of strong input shaking, beating in the response, elliptical particle motion, and significant torsion during strong shaking at the top of the concrete piers which extend from the basement to the second floor. The analyses conducted indicate that the response of the structure was elastic in all recorded earthquakes to date, including Northridge. Also, several simple damage detection methods employed did not indicate any structural damage or connection fractures. The combination of a large, real structure and low instrumentation density precluded the application of many recently proposed advanced damage detection methods in this case study. Overall, however, the findings of this study are consistent with the limited code-compliant postearthquake intrusive inspections conducted after the Northridge earthquake, which found no connection fractures or other structural damage. ?? ASCE.

  10. Corrosion damage detection with piezoelectric wafer active sensors

    NASA Astrophysics Data System (ADS)

    Thomas, Dustin T.; Welter, John T.; Giurgiutiu, Victor

    2004-07-01

    Since today's aging fleet is intended to far exceed their proposed design life, monitoring the structural integrity of those aircraft has become a priority issue for today's Air Force. One of the most critical structural problems is corrosion. In fact the KC-135 now costs $1.2 billion a year to repair corrosion. In this paper, we plan to show the use of Lamb waves to detect material loss in thin plates representative of aircraft skins. To do this we will use embedded transducers called Piezoelectric Wafer Active Sensor (PWAS) in a pitch-catch configuration. The sensors were placed on a grid pattern. Material loss through corrosion was simulated by removing the material mechanically with an abrasive tool. Thus, simulated corrosion pits of various depths and area coverage were made. Three-count tone burst wave packets were used. The Lamb wave packets were sent in a pitch-catch mode from one transmitter PWAS to the other PWAS in the grid acting as receivers. The Lamb wave mode used in these experiments was A1, since this was found to be more sensitive to changes due to material loss. At the frequencies considered in our experiments, the A1 waves are highly dispersive. It was found that, as the Lamb wave travels through simulated corrosion damage, the signal changes. The observed changes were in the signal wavelength (due to change in the dispersive properties of the medium) and in signal amplitude (due to redistribution of energy in the wave packet). This change in signal can be correlated to the magnitude of damage. To achieve this, we have used several approaches: (a) direct correlation between the sent and the received signals; (b) wavelet transform of the signal followed by correlation of the wavelet coefficients time-frequency maps; (c) Hilbert transform of the signal to produce the signal envelope and comparison of the resulting envelope signals (d) neural network correlation between the sent and received signals. It was found that these methods work well

  11. Volatile Semiochemicals Released from Undamaged Cotton Leaves (A Systemic Response of Living Plants to Caterpillar Damage).

    PubMed Central

    Rose, USR.; Manukian, A.; Heath, R. R.; Tumlinson, J. H.

    1996-01-01

    Cotton plants (Gossypium hirsutum L.), attacked by herbivorous insects release volatile semiochemicals (chemical signals) that attract natural enemies of the herbivores to the damaged plants. We found chemical evidence that volatiles are released not only at the damaged site but from the entire cotton plant. The release of volatiles was detected from upper, undamaged leaves after 2 to 3 d of continuous larval damage on lower leaves of the same plant. Compounds released systemically were (Z)-3-hexenyl acetate, (E)-[beta]-ocimene, linalool, (E)-4,8-dimethyl-1,3,7-nonatriene, (E)-[beta]-farnesene, (E,E)-[alpha]-farnesene, and (E,E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene. All systemically released compounds are known to be induced by caterpillar damage and are not released in significant amounts by undamaged plants. Other compounds, specifically indole, isomeric hexenyl butyrates, and 2-methylbutyrates, known to be released by cotton in response to caterpillar damage, were not released systemically. However, when upper, undamaged leaves of a caterpillar-damaged plant were damaged with a razor blade, they released isomeric hexenyl butyrates, 2-methylbutyrates, and large amounts of constitutive compounds in addition to the previously detected induced compounds. Control plants, damaged with a razor blade in the same way, did not release isomeric hexenyl butyrates or 2-methylbutyrates and released significantly smaller amounts of constitutive compounds. Indole was not released systemically, even after artificial damage. PMID:12226304

  12. Performance optimization of a diagnostic system based upon a simulated strain field for fatigue damage characterization

    NASA Astrophysics Data System (ADS)

    Sbarufatti, C.; Manes, A.; Giglio, M.

    2013-11-01

    The work presented hereafter is about the development of a diagnostic system for crack damage detection, localization and quantification on a typical metallic aeronautical structure (skin stiffened through riveted stringers). Crack detection and characterization are based upon strain field sensitivity to damage. The structural diagnosis is carried out by a dedicated smart algorithm (Artificial Neural Network) which is trained on a database of Finite Element simulations relative to damaged and undamaged conditions, providing the system with an accurate predictor at low overall cost. The algorithm, trained on numerical damage experience, is used in a simulated environment to provide reliable preliminary information concerning the algorithm performances for damage diagnosis, thus further reducing the experimental costs and efforts associated with the development and optimization of such systems. The same algorithm has been tested on real experimental strain patterns acquired during real fatigue crack propagation, thus verifying the capability of the numerically trained algorithm for anomaly detection, damage assessment and localization on a real complex structure. The load variability, the discrepancy between the Finite Element Model and the real structure, and the uncertainty in the algorithm training process have been addressed in order to enhance the robustness of the system inference process. Some further algorithm training strategies are discussed, aimed at minimizing the risk for false alarms while maintaining a high probability of damage detection.

  13. Damage Detection and Analysis in CFRPs Using Acoustic Emission Technique

    NASA Astrophysics Data System (ADS)

    Whitlow, Travis Laron

    Real time monitoring of damage is an important aspect of life management of critical structures. Acoustic emission (AE) techniques allow for measurement and assessment of damage in real time. Acoustic emission parameters such as signal amplitude and duration were monitored during the loading sequences. Criteria that can indicate the onset of critical damage to the structure were developed. Tracking the damage as it happens gives a better analysis of the failure evolution that will allow for a more accurate determination of structural life. The main challenge is distinguishing between legitimate damage signals and "false positives" which are unrelated to damage growth. Such false positives can be related to electrical noise, friction, or mechanical vibrations. This research focuses on monitoring signals of damage growth in carbon fiber reinforced polymers (CFRPs) and separating the relevant signals from the false ones. In this Dissertation, acoustic emission signals from CFRP specimens were experimentally recorded and analyzed. The objectives of this work are: (1) perform static and fatigue loading of CFRP composite specimens and measure the associated AE signals, (2) accurately determine the AE parameters (energy, frequency, duration, etc.) of signals generated during failure of such specimens, (3) use fiber optic sensors to monitor the strain distribution of the damage zone and relate these changes in strain measurements to AE data.

  14. Arc fault detection system

    DOEpatents

    Jha, K.N.

    1999-05-18

    An arc fault detection system for use on ungrounded or high-resistance-grounded power distribution systems is provided which can be retrofitted outside electrical switchboard circuits having limited space constraints. The system includes a differential current relay that senses a current differential between current flowing from secondary windings located in a current transformer coupled to a power supply side of a switchboard, and a total current induced in secondary windings coupled to a load side of the switchboard. When such a current differential is experienced, a current travels through a operating coil of the differential current relay, which in turn opens an upstream circuit breaker located between the switchboard and a power supply to remove the supply of power to the switchboard. 1 fig.

  15. Arc fault detection system

    DOEpatents

    Jha, Kamal N.

    1999-01-01

    An arc fault detection system for use on ungrounded or high-resistance-grounded power distribution systems is provided which can be retrofitted outside electrical switchboard circuits having limited space constraints. The system includes a differential current relay that senses a current differential between current flowing from secondary windings located in a current transformer coupled to a power supply side of a switchboard, and a total current induced in secondary windings coupled to a load side of the switchboard. When such a current differential is experienced, a current travels through a operating coil of the differential current relay, which in turn opens an upstream circuit breaker located between the switchboard and a power supply to remove the supply of power to the switchboard.

  16. Autoregressive modeling with state-space embedding vectors for damage detection under operational and environmental variability

    SciTech Connect

    Farrar, Charles; Figueiredo, Eloi; Todd, Michael; Flynn, Eric

    2010-01-01

    A nonlinear time series approach is presented to detect damage in systems by using a state-space reconstruction to infer the geometrical structure of a deterministic dynamical system from observed time series response at multiple locations. The unique contribution of this approach is using a Multivariate Autoregressive (MAR) model of a baseline condition to predict the state space, where the model encodes the embedding vectors rather than scalar time series. A hypothesis test is established that the MAR model will fail to predict future response if damage is present in the test condition, and this test is investigated for robustness in the context of operational and environmental variability. The applicability of this approach is demonstrated using acceleration time series from a base-excited 3-story frame structure.

  17. Acoustic-sensor-based detection of damage in composite aircraft structures

    NASA Astrophysics Data System (ADS)

    Foote, Peter; Martin, Tony; Read, Ian

    2004-03-01

    Acoustic emission detection is a well-established method of locating and monitoring crack development in metal structures. The technique has been adapted to test facilities for non-destructive testing applications. Deployment as an operational or on-line automated damage detection technology in vehicles is posing greater challenges. A clear requirement of potential end-users of such systems is a level of automation capable of delivering low-level diagnosis information. The output from the system is in the form of "go", "no-go" indications of structural integrity or immediate maintenance actions. This level of automation requires significant data reduction and processing. This paper describes recent trials of acoustic emission detection technology for the diagnosis of damage in composite aerospace structures. The technology comprises low profile detection sensors using piezo electric wafers encapsulated in polymer film ad optical sensors. Sensors are bonded to the structure"s surface and enable acoustic events from the loaded structure to be located by triangulation. Instrumentation has been enveloped to capture and parameterise the sensor data in a form suitable for low-bandwidth storage and transmission.

  18. Using reflectance and photography to detect ozone damage to cantaloupe plants

    NASA Technical Reports Server (NTRS)

    Gausman, H. W.; Escobar, D. E.; Rodriguez, R. R.; Thomas, C. E.; Bowen, R. L.

    1978-01-01

    Laboratory and field reflectance measurements showed that ozone-damaged cantaloupe (Cucumis melo L.) leaves had lower water contents and higher reflectance than nondamaged leaves. Cantaloupe plants with lightly, severely, and very severely ozone-damaged leaves were distinguishable from nondamaged plants by reflectance measurements in the 1.35-2.5-micron near-IR water absorption band. Ozone-damaged leaf areas were detected photographically 16 hours before the damage was visible.

  19. Multi-physics modeling of multifunctional composite materials for damage detection

    NASA Astrophysics Data System (ADS)

    Sujidkul, Thanyawalai

    This study presents a modeling of multifunction composite materials for damage detection with its verification and validation to mechanical behavior predictions of Carbon Fibre Reinforced Polymer composites (CFRPs), CFRPs laminated composites, and woven SiC/SiC matrix composites that are subjected to fracture damage. Advantages of those materials are low cost, low density, high strength-to-weight ratio, and comparable specific tensile properties, the special of SiC/SiC is good environmental stability at high temperature. Resulting in, the composite has been used for many important structures such as helicopter rotors, aerojet engines, gas turbines, hot control surfaces, sporting goods, and windmill blades. Damage or material defect detection in a mechanical component can provide vital information for the prediction of remaining useful life, which will result in the prevention of catastrophic failures. Thus the understanding of the mechanical behavior have been challenge to the prevent damage and failure of composites in different scales. The damage detection methods in composites have been investigated widely in recent years. Non-destructive techniques are the traditional methods to detect the damage such as X-ray, acoustic emission and thermography. However, due to the invisible damage in composite can be occurred, to prevent the failure in composites. The developments of damage detection methods have been considered. Due to carbon fibers are conductive materials, in resulting CFRPs can be self-sensing to detect damage. As is well known, the electrical resistance has been shown to be a sensitive measure of internal damage, and also this work study in thermal resistance can detect damage in composites. However, there is a few number of different micromechanical modeling schemes has been proposed in the published literature for various types of composites. This works will provide with a numerical, analytical, and theoretical failure models in different damages to

  20. Modal flexibility-based damage detection of cantilever beam-type structures using baseline modification

    NASA Astrophysics Data System (ADS)

    Sung, S. H.; Koo, K. Y.; Jung, H. J.

    2014-09-01

    This paper presents a new damage detection approach for cantilever beam-type structures using the damage-induced inter-storey deflection (DIID) estimated by modal flexibility matrix. This approach can be utilized for damage detection of cantilever beam-type structures such as super high-rise buildings, high-rise apartment buildings, etc. Analytical studies on the DIID of cantilever beam-type structures have shown that the DIID abruptly occurs from damage location. Baseline modification concept was newly introduced to detect multiple damages in cantilever beam-type structures by changing the baseline to the prior damage location. This approach has a clear theoretical base and directly identifies damage location(s) without the use of a finite element (FE) model. For validating the applicability of the proposed approach to cantilever beam-type structures, a series of numerical and experimental studies on a 10-storey building model were carried out. From the tests, it was found that the damage locations can be successfully identified by the proposed approach for multiple damages as well as a single damage. In order to confirm the superiority of the proposed approach, a comparative study was carried out on two well-known damage metrics such as modal strain-based damage index approach and uniform load surface curvature approach.

  1. Unified Mars detection system. [life detection

    NASA Technical Reports Server (NTRS)

    Martin, J. P.; Kok, B.; Radmer, R.; Johnson, R. D.

    1976-01-01

    A life-detection system is described which is designed to detect and characterize possible Martian biota and to gather information about the chemical environment of Mars, especially the water and amino acid contents of the soil. The system is organized around a central mass spectrometer that can sensitively analyze trace gases from a variety of different experiments. Some biological assays and soil-chemistry tests that have been performed in the laboratory as typical experiment candidates for the system are discussed, including tests for soil-organism metabolism, measurements of soil carbon contents, and determinations of primary aliphatic amines (amino acids and protein) in soils. Two possible test strategies are outlined, and the operational concept of the detection system is illustrated. Detailed descriptions are given for the mass spectrometer, gas inlet, incubation box, test cell modules, seal drive mechanism, soil distribution assembly, and electronic control system.

  2. Barely visible impact damage detection for composite sandwich structures by optical-fiber-based distributed strain measurement

    NASA Astrophysics Data System (ADS)

    Minakuchi, S.; Okabe, Y.; Mizutani, T.; Takeda, N.

    2009-08-01

    The authors developed an impact damage-detection system for large-scale composite sandwich structures using an optical fiber network running throughout the structure. A Brillouin-based sensing system with high spatial resolution (pre-pump pulse Brillouin optical time-domain analysis (PPP-BOTDA)) was utilized for distributed strain measurement. The PPP-BOTDA sensing system can measure axial strain along the optical fiber by employing stimulated Brillouin scattering. The system realizes a spatial resolution of 10 cm, a sampling interval of 5 cm, and a sensing range of more than 1 km. Our previous study revealed that a non-uniform axial strain within centimeter spatial resolution broadens the width of the Brillouin gain spectrum, which is the output of the PPP-BOTDA. The specific response of the PPP-BOTDA was employed to detect non-uniform strain distribution along a residual facesheet dent in a damaged area. First, the response of the optical fiber sensor network, formed in the adhesive layer, was simulated to clarify the effectiveness and limitations of the proposed damage-detection technique. The system was then validated by an experiment. As the damage became larger, the width of the Brillouin gain spectra became broader. Consequently, the location and size of barely visible damage could be estimated. The system developed is quite useful for a first inspection of large-scale sandwich structures in aerospace and marine applications.

  3. Vibration-based damage detection for filament wound pressure vessel filled with fluid

    NASA Astrophysics Data System (ADS)

    Zhou, W.; Wu, Z.; Li, H.

    2008-03-01

    Filament wound pressure vessels have been extensively used in industry and engineering. The existing damage detection and health monitoring methods for these vessels, such as X-ray and ultrasonic scan, can not meet the requirement of online damage detection; moreover optical grating fibre can only sense the local damage, but not the damage far away from the location of sensors. Vibration-based damage detection methods have the potential to meet such requirements. There methods are based on the fact that damages in a structure results in a change in structural dynamic characteristics. A damage detection method based on a residual associated with output-only subspace-based modal identification and global or focused chi^2-tests built on that residual has been proposed and successfully experimented on a variety of test cases. The purpose of this work is to describe the damage detection method and apply this method to assess the composite structure filled with fluid. The results of identification and damage detection will be presented.

  4. Statistical damage detection method for frame structures using a confidence interval

    NASA Astrophysics Data System (ADS)

    Li, Weiming; Zhu, Hongping; Luo, Hanbin; Xia, Yong

    2010-03-01

    A novel damage detection method is applied to a 3-story frame structure, to obtain statistical quantification control criterion of the existence, location and identification of damage. The mean, standard deviation, and exponentially weighted moving average (EWMA) are applied to detect damage information according to statistical process control (SPC) theory. It is concluded that the detection is insignificant with the mean and EWMA because the structural response is not independent and is not a normal distribution. On the other hand, the damage information is detected well with the standard deviation because the influence of the data distribution is not pronounced with this parameter. A suitable moderate confidence level is explored for more significant damage location and quantification detection, and the impact of noise is investigated to illustrate the robustness of the method.

  5. Heat transfer computed tomography techniques for damage detection in metallic structures

    NASA Astrophysics Data System (ADS)

    Johnson, Nephi R.; Lynch, Jerome P.; Jeffers, Ann E.

    2015-04-01

    The detection of damage in structures at its earliest stages has many economical and safety benefits. Permanent monitoring systems using various forms of sensor networks and analysis methods are often employed to increase the frequency and diagnostic capabilities of inspections. Some of these techniques provide spatial/volumetric information about a given area/volume of a structure. Many of the available spatial sensing techniques can be costly and cannot be permanently deployed (e.g., IR camera thermography). For this reason intricate analysis methods using permanently deployable sensors are being developed (e.g., ultrasonic piezoelectrics, sensing skins). One approach is to leverage the low cost of heaters and temperature sensors to develop an economical, permanently installable method of spatial damage detection using heat transfer. This paper presents a method similar to that of X-ray computed tomography (CT). However, the theories for Xray CT must be adapted to properly represent heat transfer as well as account for the relatively large and immobile sensors spacing used on a structure (i.e., there is a finite number of heaters/sensors permanently installed around the perimeter of the area of interest). The derivation of heat transfer computed tomography is discussed in this paper including two methods for steering the effective heat wave. A high fidelity finite element method (FEM) model is used to verify the analytical derivation of individual steps within the method as well as simulate the complete damage detection technique. Experimental results from both damaged and undamaged aluminum plate specimens are used to validate the FEM model and to justify theoretical assumptions. The simulation results are discussed along with possible improvements and modifications to the technique.

  6. Fatigue crack damage detection using subharmonic component with nonlinear boundary condition

    SciTech Connect

    Wu, Weiliang Qu, Wenzhong E-mail: xiaoli6401@126.com; Xiao, Li E-mail: xiaoli6401@126.com; Shen, Yanfeng Giurgiutiu, Victor

    2015-03-31

    In recent years, researchers have focused on structural health monitoring (SHM) and damage detection techniques using nonlinear vibration and nonlinear ultrasonic methods. Fatigue cracks may exhibit contact acoustic nonlinearity (CAN) with distinctive features such as superharmonics and subharmonics in the power spectrum of the sensing signals. However, challenges have been noticed in the practical applications of the harmonic methods. For instance, superharmonics can also be generated by the piezoelectric transducers and the electronic equipment; super/subharmonics may also stem from the nonlinear boundary conditions such as structural fixtures and joints. It is hard to tell whether the nonlinear features come from the structural damage or the intrinsic nonlinear boundary conditions. The objective of this paper is to demonstrate the application of nonlinear ultrasonic subharmonic method for detecting fatigue cracks with nonlinear boundary conditions. The fatigue crack was qualitatively modeled as a single-degree-of-freedom (SDOF) system with non-classical hysteretic nonlinear interface forces at both sides of the crack surfaces. The threshold of subharmonic generation was studied, and the influence of crack interface parameters on the subharmonic resonance condition was investigated. The different threshold behaviors between the nonlinear boundary condition and the fatigue crack was found, which can be used to distinguish the source of nonlinear subharmonic features. To evaluate the proposed method, experiments of an aluminum plate with a fatigue crack were conducted to quantitatively verify the subharmonic resonance range. Two surface-bonded piezoelectric transducers were used to generate and receive ultrasonic wave signals. The fatigue damage was characterized in terms of a subharmonic damage index. The experimental results demonstrated that the subharmonic component of the sensing signal can be used to detect the fatigue crack and further distinguish it from

  7. Fatigue crack damage detection using subharmonic component with nonlinear boundary condition

    NASA Astrophysics Data System (ADS)

    Wu, Weiliang; Shen, Yanfeng; Qu, Wenzhong; Xiao, Li; Giurgiutiu, Victor

    2015-03-01

    In recent years, researchers have focused on structural health monitoring (SHM) and damage detection techniques using nonlinear vibration and nonlinear ultrasonic methods. Fatigue cracks may exhibit contact acoustic nonlinearity (CAN) with distinctive features such as superharmonics and subharmonics in the power spectrum of the sensing signals. However, challenges have been noticed in the practical applications of the harmonic methods. For instance, superharmonics can also be generated by the piezoelectric transducers and the electronic equipment; super/subharmonics may also stem from the nonlinear boundary conditions such as structural fixtures and joints. It is hard to tell whether the nonlinear features come from the structural damage or the intrinsic nonlinear boundary conditions. The objective of this paper is to demonstrate the application of nonlinear ultrasonic subharmonic method for detecting fatigue cracks with nonlinear boundary conditions. The fatigue crack was qualitatively modeled as a single-degree-of-freedom (SDOF) system with non-classical hysteretic nonlinear interface forces at both sides of the crack surfaces. The threshold of subharmonic generation was studied, and the influence of crack interface parameters on the subharmonic resonance condition was investigated. The different threshold behaviors between the nonlinear boundary condition and the fatigue crack was found, which can be used to distinguish the source of nonlinear subharmonic features. To evaluate the proposed method, experiments of an aluminum plate with a fatigue crack were conducted to quantitatively verify the subharmonic resonance range. Two surface-bonded piezoelectric transducers were used to generate and receive ultrasonic wave signals. The fatigue damage was characterized in terms of a subharmonic damage index. The experimental results demonstrated that the subharmonic component of the sensing signal can be used to detect the fatigue crack and further distinguish it from

  8. An Evaluation of the Applicability of Damage Tolerance to Dynamic Systems

    NASA Technical Reports Server (NTRS)

    Forth, Scott C.; Le, Dy; Turnberg, Jay

    2005-01-01

    The Federal Aviation Administration, the National Aeronautics and Space Administration and the aircraft industry have teamed together to develop methods and guidance for the safe life-cycle management of dynamic systems. Based on the success of the United States Air Force damage tolerance initiative for airframe structure, a crack growth based damage tolerance approach is being examined for implementation into the design and management of dynamic systems. However, dynamic systems accumulate millions of vibratory cycles per flight hour, more than 12,000 times faster than an airframe system. If a detectable crack develops in a dynamic system, the time to failure is extremely short, less than 100 flight hours in most cases, leaving little room for error in the material characterization, life cycle analysis, nondestructive inspection and maintenance processes. In this paper, the authors review the damage tolerant design process focusing on uncertainties that affect dynamic systems and evaluate the applicability of damage tolerance on dynamic systems.

  9. Neonatal Jaundice Detection System.

    PubMed

    Aydın, Mustafa; Hardalaç, Fırat; Ural, Berkan; Karap, Serhat

    2016-07-01

    Neonatal jaundice is a common condition that occurs in newborn infants in the first week of life. Today, techniques used for detection are required blood samples and other clinical testing with special equipment. The aim of this study is creating a non-invasive system to control and to detect the jaundice periodically and helping doctors for early diagnosis. In this work, first, a patient group which is consisted from jaundiced babies and a control group which is consisted from healthy babies are prepared, then between 24 and 48 h after birth, 40 jaundiced and 40 healthy newborns are chosen. Second, advanced image processing techniques are used on the images which are taken with a standard smartphone and the color calibration card. Segmentation, pixel similarity and white balancing methods are used as image processing techniques and RGB values and pixels' important information are obtained exactly. Third, during feature extraction stage, with using colormap transformations and feature calculation, comparisons are done in RGB plane between color change values and the 8-color calibration card which is specially designed. Finally, in the bilirubin level estimation stage, kNN and SVR machine learning regressions are used on the dataset which are obtained from feature extraction. At the end of the process, when the control group is based on for comparisons, jaundice is succesfully detected for 40 jaundiced infants and the success rate is 85 %. Obtained bilirubin estimation results are consisted with bilirubin results which are obtained from the standard blood test and the compliance rate is 85 %. PMID:27229489

  10. Case study: Automated utilities damage assessment (AUDA) system

    SciTech Connect

    Salavani, R.; Laventure, G.C.; Smith, M.D.

    1994-12-31

    A demonstration program of an automated utility damage assessment system (AUDA) at a United States Air Force facility (USAF) is described. The AUDA is designed to assess damage, in an efficient manner, to military equipment or utilities, such as electrical equipment, potable and waste water, HVAC systems, petroleum, oil and lubricants, and natural gas.