• 专利附录
  • 专利说明
  • 权利要求
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    • 专利摘要:
    These are methods, devices and techniques for structural health monitoring ("SHM") that involve building maps of deformation fields (amplitude and phase related to excitation) on the surface of the structural component (7) under monitoring based on a network of deformity measurements by Bragg (9) fiber sensors.
    公开号:BR112017008942B1
    申请号:R112017008942-4
    申请日:2015-10-21
    公开日:2021-03-02
    发明作者:Lo Anchieta Da Silva；Fernando Dotta；Laudier Jacques De Moraes Da Costa；Arthur Martins Barbosa Braga；Luiz Carlos Guedes Valente；Daniel Ramos Louzada；Leonardo SALVINI；Paula Medeiros Proença De Gouvêa
    申请人:Embraer S.A.；Faculdades Católicas；
    IPC主号:
    专利说明:

    FIELD
    [0001] The technology in this document refers to the field of structural health monitoring (“SHM”), and more specifically, to methods and systems for monitoring structural health of composite, metal or other structures, based on the measurement of deformation field on the surface under test and comparison with an initial or otherwise known signature (or signatures) of the structure (not defective) by scanning a frequency range and evaluating the amplitude (or RMS value or peak value peak) resonance close to sensors (or resonances close to sensors) different. Even more particularly, methods, apparatus and techniques provided by the present exemplary non-limiting configuration comprise or involve maps of strain fields (amplitude and phase related to excitation) on the surface of the structural component under monitoring based on a network of sensor deformity measurements fiber Bragg mesh. BACKGROUND OF THE INVENTION
    [0002] Since all structures in service may require adequate inspection and maintenance, they must be monitored for their integrity and health condition to extend their lives or prevent catastrophic failure. Several techniques have been employed to identify failures or damage to structures. Such techniques include conventional visual inspection and automated non-destructive techniques that include ultrasonic scanning and eddy current, acoustic emission and X-ray inspection. Such conventional techniques often require at least temporary removal of structures from service for inspection. Although they are still widely used for inspecting isolated locations, they are often time-consuming and expensive and may not be adequate on their own to inspect equipment such as aircraft while the equipment is in service.
    [0003] Such approaches have their disadvantages and may not provide effective online methods for implementing a reliable sensory network system and / or accurate monitoring methods that can diagnose, classify and / or predict structural condition with minimal intervention by human operators.
    [0004] With the advancement of sensor technologies, new diagnostic techniques for monitoring structural integrity at the site have made significant progress. Typically, these new techniques use sensory systems of sensors and suitable actuators embedded in the host structures.
    [0005] Some SHM systems use "passive" deformity tracking techniques or acoustic emission monitoring. However, to effectively detect damage in many applications, both passive deformity tracking and passive monitoring acoustic emission techniques may require continuous monitoring. Consequently, if a power failure or power shutdown occurs, the SHM system can be deactivated - which can be a disadvantage. In addition, both passive deformity tracking and passive acoustic emission monitoring may not be as sensitive as desired, and therefore may be less accurate and / or reliable. The accuracy and reliability of acoustic emission monitoring techniques can also be compromised by the generally noisy environment of a vehicle or other environment. Another possible disadvantage of acoustic emission monitoring is that a large amount of data storage may be required. To quantify and locate the damage, the deformity tracking technique may require a finite element deformity distribution model with which to compare the measured deformity distribution along the structure, possibly increasing the development cost.
    [0006] Other SH systems can be considered “active” systems due to the fact that they use transducers to actively excite and capture the vibrational characteristics of the structure. The vibrational characteristics can be purchased from known or baseline (and thus predetermined) vibrational characteristics of a normal undamaged structure; and the difference (or differences) is used to determine the health of the structure. Specifically, in some SHM systems, vibrational characteristics can be defined by computing the transfer function between each actuator and sensor. The transfer functions can then be compared to a baseline reference that represents a normal “healthy” state of the structure. The baseline can be generated by collecting several sets of actuator / sensor data when the structure is healthy, and computing statistical values such as the medium and standard deviation of the data sets. However, variations in structure temperature can sometimes cause these active SHM systems to erroneously detect damage. Specifically, temperature variations in the structure can cause variations in the measured vibrational characteristics that are carried over to the transfer functions computed from them.
    [0007] Known techniques often follow one of two approaches: excitation and signal processing, on the one hand, and, on the other hand, signal and results worked.
    [0008] For example, the methods are known to detect changes in the attenuation characteristics of vibrational waves in a laminated composite structure to locate delaminated regions in the structure. Piezoceramic devices can be applied as actuators to generate vibrational waves, and fiber optic cables with different network locations can be used as sensors to obtain or capture propagation wave signals. A possible disadvantage of this type of system is that it cannot accommodate a large number of actuator arrays and, as a consequence, each of the actuators and sensors must be placed individually. Since damage detection is based on changes in vibrational waves that travel along line of sight paths between actuators and sensors, such a method may fail to detect damage located outside the paths and / or around the limit of the structure.
    [0009] Another known approach to damage detection uses a self-contained insulating circuit for monitoring and evaluating structural health. Such an insulating circuit can, for example, consist of a series of layers and stacked traces of deformity sensors, where each sensor measures changes in the deformity at their corresponding location to identify defects in an insulating structure. The insulating circuit can, for example, comprise a passive system, that is, it does not have any actuator to generate signals. Another exemplary passive sensing system can use a piezoceramic fiber sensing system that has flat fibers embedded in a composite structure.
    [0010] A possible disadvantage of these and other passive methods is that they cannot monitor delamination and internal damage between the sensors. In addition, these methods can typically detect the conditions of their host structures only in the local areas where the self-contained circuit and piezoceramic fiber are attached.
    [0011] Another interesting method for detecting damage to a structure uses a sensory network layer, called the Stanford Multiple Actuator and Receiver Transduction Layer (SMART). SMART Layer® includes piezoceramic sensors / actuators placed equidistant and cured with flexible dielectric films that sandwich piezoceramic sensors / actuators (“piezoceramics”). The actuators generate acoustic waves and the sensors receive / transform the acoustic waves into electrical signals. To connect the piezoceramics to an electronic box, metallic coated wires are notched using the conventional flexible circuitry and laminated between the substrates. As a consequence, a considerable amount of the flexible substrate area may be needed to cover the coated wire regions. In addition, SMART Layer® may need to be cured with its host structure composed of laminated composite layers. Due to the internal stress caused by a high temperature cycle during the curing process, the piezoceramics in SMART Layer® can be micro-cracked. In addition, the SMART Layer® substrate can sometimes be easily separated from the host structure. In addition, it can be very difficult to insert or attach the SMART Layer® to its host structure that has a curved section and, as a consequence, a compressive load applied to the curved section can sometimes easily bend the coated wires. Fractured piezo-ceramics and bent wires can be susceptible to electromagnetic interference noise and provide misleading electrical signals. In harsh environments, such as thermal stress, shock and field vibration, SMART Layer® may not necessarily be a robust and unreliable tool for monitoring structural health. In addition, replacing damaged and / or defective actuators / sensors can sometimes be costly since the host structure may need to be disassembled.
    [0012] Another known actuator and sensor system is known for use with composite structures, specifically, carbon fiber reinforced plastic structures with piezoceramic actuators, particularly for purposes of active vibration attenuation and / or shape control, as well as sensors fiber Bragg network, particularly in the form of deformity measurement sensors. Piezoceramic actuators are designed as piezofiber modules and Bragg network sensors in fiber are at least partially incorporated into piezofiber modules.
    [0013] Still other interrogation systems known to monitor structural health conditions include at least one wave generator to generate a wave signal and fiber optic sensors applied to a structure. The interrogation system also includes at least one electronic module to generate an input sensor signal and send the input sensor signal to the fiber optic sensors. Each fiber optic sensor prints the wave signal to the input sensor signal to generate an output sensor signal that is shifted by frequency of the input sensor signal. The electronics module generates an information signal in response to the output sensor signal. The interrogation system also includes a signal processing unit and a relay switch matrix module. Each relay switch relays the information signal to the signal processing unit and the signal processing unit generates a digital sensor signal which is subsequently sent to a computer.
    [0014] Yet another known method for monitoring damage to a structure that has an actuator and a sensor includes exciting the actuator over a predetermined frequency range to excite the structure, measuring a vibrational characteristic of the structure over the predetermined frequency range in response to excitation of the actuator using the sensor, calculating a transfer function for the actuator and the sensor using the measured vibrational characteristic, determining a change in the vibrational characteristic over the predetermined frequency range using the transfer function, and analyzing the determined change in the vibrational characteristic over the predetermined frequency range to facilitate determining the possibility of the structure being damaged.
    [0015] Other known devices for monitoring the structural health conditions of host structures include at least one fiber optic sensor and an electronic module. The fiber optic sensor includes an operational laminated fiber optic cable to generate a frequency shift of a light signal that passes through the optical fiber and a coating layer applied to the laminated optical cable. The frequency shift is proportional to the vibration of the host structure. The electronics module sends an incoming light signal to the fiber optic sensor, receives a sensor signal from the fiber optic sensor, and processes the sensor signal.
    [0016] Yet another known method for optimizing transducer performance in a transducer array in a structural health monitoring system includes specifying a plurality of trajectories between the pairs of transducers in a monitored structure and evaluating the quality of signal transmissions over along the trajectories in order to optimize the condition of frequency operation and gain of the transducers.
    [0017] In yet another known method for diagnosing a structure, at least one electromechanical transducer is attached to a structure as a diagnostic object and is actuated with an alternating voltage of constant amplitude, and a current flowing through at least an electromechanical transducer is measured. Next, high-frequency components around an electromechanical transducer drive frequency are separated from a current signal. Next, the modulation information due to damage is extracted from the amplitude and / or phase demodulation of the high frequency components. Then a damage index is assessed based on the modulation information. Therefore, structural health can be diagnosed with the use of at least one electromechanical transducer, without baseline data, in a measurement.
    [0018] Yet another known method refers to the testing of structures or bodies to determine whether they contain defects such as cracks or delamination. This method for testing a body comprises the steps of comparing the first data, representing an excitation signal sent to the body in order to produce a guided wave within the body, with second data, derived from the body while carrying the guided wave, to identify a phase difference between the first and second data; and determining a measure of the structural integrity of the body using the phase difference. It is argued that, based on the assessment of the structural body by means of phase modulation induced by defect, the most accurate test can be performed.
    [0019] Another known structural health monitoring system, for example, a system used in the non-destructive assessment of an aircraft structure provides a method and apparatus for assessing one or more anomalies within a structure using a monitoring system structural health that includes at least three transducers arranged in operational contact with the structure so that not even two transducers are aligned to be parallel. A transducer excites an elastic wave that propagates through the structure, and reflections of any anomalies within the structure are collected by the three transducers. These collected signals are analyzed to identify an anomaly within the structure. Flight time techniques are used to determine the location of the anomaly.
    [0020] The operation of the signal provided for in the non-limiting exemplary configurations in this document is unique at least due to the fact that the signal work involves matching phase and amplitude, while many other known techniques are directed to the operation of only phase or just amplitude. Corresponding to the phase and amplitude, many advantages are obtained, such as a much more refined resolution for the measurement of deformity with Bragg network sensors. These features are summarized in Tables 1 and 2 below. TABLE 1 - SIGNAL PROCESSING AND EXCITATION

    TABLE 2 - SIGNAL WORK AND RESULTS

    SUMMARY
    [0021] State of the art systems that refer to structural health monitoring are described in US 5,814,729 A and US 6,006,163 A. An ultrasonic acoustic sensor is described in US 2013/0 129 275 A1.
    [0022] The present invention provides a method for monitoring the structural health of a component according to claim 1 and a respective system according to claim 5. Configurations are defined by the dependent claims.
    [0023] The methods, devices and techniques provided by the present exemplary non-limiting configurations comprise or involve maps of strain fields (amplitude and phase related to excitation) on the surface of the structural component under monitoring based on a network of sensor deformity measurements fiber Bragg mesh.
    [0024] The mapped strain fields are obtained from the excitation of the structural component by piezoelectric actuators fixed and / or incorporated into the structural component.
    [0025] Several frequencies are used for excitation, one frequency at a time, generating additional strain fields that add to that already existing in the structure resulting from the primary and secondary loads in the structure.
    [0026] The fact that the deformations conferred by piezoelectric elements on the surface of the element are very small ensures the linearity of the response and allows the application of the superimposition principle.
    [0027] Therefore, the signals captured by the optical sensors are filtered in order to measure only the deformations of the same frequency used for excitation, that is, only the contribution to the field originated by the piezoelectric actuators.
    [0028] The deformation maps thus obtained are compared to a standard or baseline map obtained previously which is the structural component without any deformation or with a defect of known dimensions and positions.
    [0029] An artificial intelligence algorithm can be employed in some non-limiting configurations so that, based on the initial pattern or baseline, it is possible to detect, locate and quantify new failures or failures or, alternatively, monitor the growth of any failure or detected data.
    [0030] Therefore, in a non-limiting aspect, a method is provided for monitoring damage to a structure that has at least one actuator and at least one sensor. The method includes in-phase or out-of-phase excitation of at least one actuator or a group of actuators, or all actuators using CW (continuous wave) across a predetermined frequency range to excite the structure, so generating a dynamic strain field, with sinusoidal (sinusoidal) time variation at the same frequency as the potential difference imposed on the piezoelectric elements. The strain field superimposes on the strain field already existing in the structural component caused by primary and secondary loads that act on the structural component, including those related to temperature. In exemplary non-limiting configurations, the choice of the actuation frequency is made different from the frequency ranges associated with the primary and secondary loads as well as temperature variations in the structural component. The strain field measurement can then be filtered in order to select only that portion associated with the sinusoidal (sinusoidal) actuation generated by the actuators.
    [0031] Therefore, the signals captured by the optical sensors are filtered at a specific frequency of the sinusoidal (sinusoidal) signal used to power the actuators. These filters are used to detect its amplitude and phase.
    [0032] Based on the amplitude and phase of the various sensors distributed in a network of sensors fixed to the surface of the structural component under monitoring, a two-dimensional map is obtained from the surface deformities: amplitudes and phases. Using the pattern recognition methods, this map is analyzed in order to identify the presence of defects (example: delamination in a composite material or corrosion in a metallic material).
    [0033] By synchronizing, thus, the performance with the detection it is possible to obtain improved resolution for the measurement of deformity with the use of fiber Bragg grafts (FBG).
    [0034] In another aspect, the present exemplary non-limiting configuration includes a system for monitoring damage to a structural component. The system includes:
    [0035] a) an actuator operationally connected to the structural component to excite the structural component;
    [0036] b) a sensor operationally connected to the structural component to measure a vibrational characteristic of the structure in response to the excitation of the structure;
    [0037] c) a tunable laser used as a narrowband light source for interrogating fiber optic sensors;
    [0038] d) an optical circulator connected with the tunable laser and equipped with two outputs: one output transmits the light signal emitted by the tunable laser towards the Bragg network sensors, and the other output, transmits the signal reflected by the sensors to a photodetector;
    [0039] e) a locking amplifier;
    [0040] f) a power amplifier designed to increase the excitation signal provided by the lock (item e);
    [0041] g) a multiplexer to control the distribution of the harmonic excitation signal (phase and amplitude) among the various piezoelectric actuators;
    [0042] h) a photodetector to find the light signal reflected by the fiber optic sensors, transforming it into an electrical signal transmitted to the locking amplifier;
    [0043] i) a fiber optic multiplexer in order to access the sensors distributed in more than one optical fiber;
    [0044] j) a computer or other processing element configured to analyze the deformation signals that obtain the deformation field maps and compare them with the reference map, for example, automatically detecting, locating and quantifying damage to the structural component. BRIEF DESCRIPTION OF THE DRAWINGS
    [0045] The following detailed description of exemplary non-limiting configurations should be read in conjunction with the drawings, where:
    [0046] Figure 1 is an exemplary non-limiting system configuration for the structural health monitoring (SHM) of an exemplary structural component.
    [0047] Figure 2 is a flowchart that illustrates the general method of the exemplary non-limiting configuration for structural health monitoring (SHM) of an exemplary structural component.
    [0048] Figure 3 is an exemplary plot that represents the reflection spectrum of five FBG sensors, when irradiated with a broadband optical source.
    [0049] Figure 4 shows the displacement of the reflection spectrum of an FBG sensor and the variation of the amplitude in the infrared signal, when a mechanical excitation in the structure of interest is caused by a PZT actuator.
    [0050] Figures 5a and 5b illustrate two-dimensional and three-dimensional field deformation maps. DETAILED DESCRIPTION OF EXEMPLIFICATIVE NON-LIMITING SETTINGS
    [0051] According to the present exemplary non-limiting configuration, the term "structural damage" means delamination, de-agglutination, cracks, peeling, corrosion, wear, crushing, rolling, loss of mass and / or loss of rivets.
    [0052] The exemplary non-limiting configuration refers to a method and system for monitoring structural health of composites as well as metallic substrates.
    [0053] In relation to vibrations designed to induce deformities, the system can be operable by means of vibrations caused from piezoelectric actuators, alloy with shape memory, etc., or external vibrations, magnetic fields, sound fields, etc.
    [0054] The exemplary non-limiting configurations will now be described in relation to the Figures.
    [0055] Figure 1 depicts an exemplary non-limiting configuration of a system (100) designed for structural health monitoring (SHM) of an exemplary structure. According to Figure 1, (1) is a tunable laser connected to an optical circulator (2) with two outputs: a first output is connected to the optical fibers (8) in which they are connected to numerous fiber Bragg networks or sensors (9a, 9b, 9c); and a second output is connected to a photodetector (3). The photodetector (3) is, in turn, connected by any known means to a locking amplifier (4). The tunable laser (1) and the locking amplifier (4) are connected to a computer or other control processor 50. The locking amplifier (4) is also connected to a power amplifier (5) where it is connected to numerous actuators (6a, 6b, 6c). There can be any number of actuators (6), but for the sake of simplicity only three actuators (6a, 6b, 6c) are represented in this Figure.
    [0056] The actuators (6) are positioned linearly in the boundary of the end of the structural component (7).
    [0057] In the system (100) depicted in Figure 2, the FBG sensors (9) capture the amplitude and phase of vibrational characteristics of the structural component 7. These captured amplitudes and phases encoded in laser light are selected by the optical circulator 2, one light signal at a time, for photodetector 3. Photodetector 3 converts the received light signal into an analog electrical signal and provides the analog electrical signal to the locking amplifier (4). The locking amplifier (4) comprises a conventional analog double-phase locking amplifier that measures the amplitude and phase of the signals using a synchronous detection process to recover the signals. The locking amplifier (4) acts as a narrow bandpass filter that removes unwanted noise while allowing the signal to be measured. The frequency of the signal to be measured and then the bandpass region of the filter by a reference signal, which is supplied by the reference signal generator 52 to the locking amplifier together with the signal detected by the photodetector 3. The signal the reference signal generator 52 generates at the same frequency as the modulation of the photodetector signal to be measured since the reference signal is also provided for actuators 6. The locking amplifier (4) then compares the frequency of the signal measured by the photodetector (3) with the reference signals generated for the actuators (6). In this way, the signals obtained through sensors (9) and the signals generated through the actuators (6) are synchronized. For each excitation frequency, all information generated by the sensors (9) is stored in the storage device 54 in order to be analyzed in order to assess the integrity of the structural component (7).
    [0058] The exemplary non-limiting configuration of system 100 comprises a set of at least two Bragg 9 networks written along at least one optical fiber 10. The Bragg 9 networks are fixed (mechanically coupled) to the surface of structural component 7 or embedded in the structural component, in the region where they are defined to perform the monitoring, and provide deformity measurements.
    [0059] A set of piezoelectric actuators 6 consisting of at least one actuator is fixed (mechanically coupled) to the surface of the structural component or embedded in that structure.
    [0060] A tunable laser 1 is used as a narrow band light source for interrogating fiber optic sensors 9. Laser light source 1 scans a wide band of wavelengths to interrogate all network sensors Bragg 9 installed in structural component 7 under monitoring. Different FBGs 9 can be written to reflect different light frequencies in order to scan the laser light source through a light frequency band that allows the system 100 to acquire deformity characteristics captured by the distinctly located FBGs 9. The ability to an FBG 9 measuring deformity is well known in the art.
    [0061] The optical circulator 2 has two outputs: a first output sends the light signal emitted by the tunable laser 1 towards the Bragg network sensors 9, and another output sends the signal reflected by the sensors back along of the same optical fibers 10 for a photodetector 3.
    [0062] The locking amplifier 4 has a dual function: (i) using its own reference signal (from the reference signal generator 52) to provide a harmonic signal for excitations of the piezoelectric actuators 6; and (ii) recovering the amplitude and phase of the sinusoidal (sinusoidal) deformity signals, in that same frequency component, produced exclusively by the harmonically excited piezoelectric 6 actuators.
    [0063] The power amplifier 5 is designed to increase the excitation signal provided by the locking amplifier reference signal generator 52. In the proposed non-limiting system, the piezoelectric actuators are powered by means of a continuous wave signal (CW ).
    [0064] A multiplexer 58 is used to control the distribution of the harmonic excitation signal (phase and amplitude) across the various piezoelectric actuators 6.
    [0065] Photodetector 3 is used to find the light signal reflected by the fiber optic sensors 9, transforming them into an electrical signal conducted to the locking amplifier 4.
    [0066] A fiber optic multiplexer 2 can be used in order to access more than one optical fiber in case the sensors are distributed in more than one optical fiber 10.
    [0067] According to the exemplary non-limiting configuration, the system for the structural health monitoring (SHM) of a structural component, a computer or other processing element 50 designed to (i) control inspections by means of software, hardware , firmware or a combination thereof; and (ii) analyze the deformation signals in order to obtain the deformation field maps and compare them with the reference map, with detection, location and quantification of damages in the structural component or monitoring the growth of some previously detected damages . That is, the software based on artificial intelligence for pattern recognition automatically recognizes the comparison between deformation field maps.
    [0068] Figure 2 is a simplified flowchart of a method according to the exemplary non-limiting configuration, which can be performed by processor 50 under control of software code stored in storage 54. According to this flowchart, (101) means that the structural component is under monitoring. Then, in (102) the signal analysis is performed by means of excitation frequency as described above. A strain field map is generated at (103). The comparison between the deformation field map generated with a reference or deformation field map of is performed in (104). Damage detection (difference between the two maps) is evaluated by (105). In the absence of damage, the method returns to (101) and repeats steps (101) to (104). If any damage is detected, the method performs operations that lead to the assessment of Damage Location at (106), followed by the assessment of Damage Severity at (107) and the response with the location and severity of Damage at (108).
    [0069] An exemplary non-limiting method for structural health monitoring (SHM) of a structural component that has at least one actuator and at least one sensor or an actuator group and sensor group can then comprise:
    [0070] a) Excitation in phase or out of phase with a predetermined frequency range to excite said structural component 7, in order to generate a dynamic strain field, with sinusoidal time variation (sinusoidal) at the same frequency as the potential difference imposed on piezoelectric elements 6;
    [0071] b) filter the strain field measurement to select only the strain field range associated with the sinusoidal (sinusoidal) actuation generated by the actuators; 6;
    [0072] c) obtain a two-dimensional map with the amplitudes and phases of the surface deformities, in which these maps are based on the amplitude and phase of the various sensors 9 distributed in a network of sensors 9 fixed to the surface of the structural component under monitoring ;
    [0073] d) repeat the procedure for multiple frequency bands;
    [0074] e) to compare the two-dimensional maps obtained through the different frequencies in the analysis to detect structural damage; and
    [0075] f) perform computational analysis of two-dimensional field deformation maps then in this way with the aid of pattern recognition methods in order to identify structural damage.
    [0076] Figure 3 is a plot that represents the reflection spectrum of five FBG sensors, when irradiated with a broadband optical source. In the exemplary configuration, photodetector 3 converts the reflection spectrum into an electrical signal that can be analyzed in the frequency domain. Although it was possible for controller 50 to provide a digital signal processor using FFT technology, the preferred non-limiting configuration uses a simpler technique of a synchronous locking amplifier to synchronously detect the frequency and phase of the electrical signal detected.
    [0077] Figure 4 shows the exemplary displacement of the reflection spectrum of an exemplary FBG sensor and the variation in amplitude in the infrared signal, when a mechanical excitation in the structure of interest is caused by a PZT 6a actuator. If the excitation of the PZT actuator is sinusoidal, the signal detected by the resulting FBG will show a phase shift that changes sinusoidally. This phase shift can be detected synchronously by the locking amplifier (4). These signals can be stored in storage 54 along with other signals stored for other frequencies and other sensors 6. Processor 50 runs a stored program to analyze the stored signals and to generate a graphical strain map for display on the graphical display 56.
    [0078] Figure 5a illustrates an exemplary deformation 3D map. The 3D map indicates that a square delamination is in the center of the plate. As can be seen, the deformation map graphically represents the deformation (εU.A.) as a function of the position (x, y). In this case, deformation is represented by deformity and ε - which is defined as the amount of deformation per unit length of an object when a load is applied. The ε deformity is calculated by dividing the total deformation of the original length by the original length (L): ε = ΔL / L. Typical values for ε deformity are less than 0.013 cm / cm (0.005 inch / inch) and are often expressed in microdeform units (ie, 10-6). Note the scale on the right side of Figure 5a showing Deformity ε in units of 0-10 x 10-6. In the exemplary configuration, the amount of Deformity ε can be encoded in a visible color spectrum with, for example, greater deformities of ε = 10 x 105 that show red and lower deformities of ε = 0 that show violet, and deformities between evenly distributed along the “ROYGBIV” colors of the rainbow. The deformation map in Figure 5a shows, in addition, graphically the topography of the deformity, with lower deformities that have lower elevation and higher deformities that have higher elevations or peaks. Through such visualization, it is possible to see which parts of the structural element are under how much deformity. The deformation map visualization in Figure 5b is 2D and uses color coding as described above to allow visualization of the amount of deformity. Other representations are possible.
    [0079] The exemplary non-limiting configuration will now be illustrated by the Example shown below. EXAMPLE
    [0080] Through numerical simulations, strain maps related to the behavior of a composite plate were obtained. The composite plate has 16 overlapping layers, which have been subjected to mechanical vibration caused by PZT 6 actuators.
    [0081] Several delamination models were tested by varying the dimensions (length and width). For each model tested, 40 excitation frequencies ranging from 11.1 kHz to 15.0 kHz with a 0.1 kHz step were simulated. Thus, for each delamination model, 40 deformation maps were obtained.
    [0082] For this test, the excitation frequency was w = 13.7 kHz. The deformation map 5a shows that a square delamination is in the center of the plate (x coordinate = 0.250 m and y coordinate = 0.125 m), between layers 4 and 5.
    [0083] From Figures 5a, 5b it is clear that a deformation pattern of the order of 10 microdeformities is present in the delamination region.
    权利要求:
    Claims (7)
    [0001]
    1. Method for monitoring the structural health of a structural component (7) with several Bragg network sensors in FBG fiber (9), distributed in a network of FBG sensors (10) attached to the surface of the structural component (7) , the method comprises: a) exciting the structural component (7) by exciting at least one actuator (6) with the use of continuous waves over a predetermined frequency range, to generate a dynamic strain field, in the structural component, the dynamic strain field having sinusoidal time variations at the same frequencies as an excitation signal imposed on at least one actuator; the method being characterized by; b) measure a strain field using the various FBG sensors (9) distributed in the network of FBG sensors fixed to the surface of the structural component including synchronizing the actuation of said at least one actuator (6) with capture using the various FBG sensors (9) to obtain deformity measurements; synchronization includes c) filtering the strain field measurement to select only that portion of the strain field corresponding to the frequencies of the sinusoidal actuation generated by at least one actuator (6); d) in response at least in part to the filtered measurement of the deformation field, generate a two-dimensional map of the deformation field that indicates the amplitudes and phases of the surface deformities, and the said deformation field map is based on the amplitude and phase measured by the different FBG sensors (9); e) repeat the procedure for multiple excitation frequencies of at least one actuator (6); f) compare the two-dimensional maps of the strain field obtained by different excitation frequencies for the detection of structural damage; and g) to perform computational analysis of two-dimensional field deformation field maps obtained in this way with the aid of pattern recognition methods to identify structural damage.
    [0002]
    2. Method, according to claim 1, characterized by the fact that the FBG sensors (9) capture the amplitude and phase of the vibrational characteristics of the structural component (7), the amplitudes and phases captured are encoded in laser light and are converted into electrical signals; wherein a narrow bandpass filter is applied to electrical signals to remove unwanted noise while allowing a signal to be measured; in which the bandpass region of the filter is configured by a reference signal at the same frequency as the signals generated to excite at least one actuator (6).
    [0003]
    3. Method, according to claim 1, characterized by the fact that said filtering excludes not only the amplitude, but also the phase, and selects only a specific frequency of the sinusoidal signal used in the supply of at least one actuator (6) .
    [0004]
    4. Method, according to claim 1, characterized by the fact that the method additionally includes obtaining a baseline two-dimensional strain field map for comparison when the structural element (7) under monitoring is free from defects or has defects known.
    [0005]
    5. System for monitoring the structural health of a structural component (7), which comprises: a computer configured to (i) control inspections by running software; and (ii) analyze deformation signals to obtain deformation field maps and compare the deformation field maps to a reference map, for detecting, locating and assessing damages in the structural component (7) or monitoring the growth of some damages previously detected; a set of at least two Bragg grafts written along at least one optical fiber (10), Bragg grafts form Bragg network sensors (9), with Bragg network sensors (9) being positioned longitudinally in said structural component (7) under monitoring, with Bragg grafts being affixed to a surface of the structural component (7) and configured to affect monitoring, and to provide deformity measurements; a set of piezoelectric actuators (6) comprising at least one actuator (6), affixed to the surface of the structural component (7) or incorporated into the structure of the structural component (7) and powered by a continuous wave signal; characterized by understanding; a tunable laser (1) used as a narrowband light source to interrogate Bragg network sensors (9), where the tunable laser (1) is configured to scan a wide wavelength band to interrogate sensors Bragg network (9) installed in the structural component (7) under monitoring; an optical circulator providing at least the first and second outputs, where the first output sends a light signal emitted by the tunable laser (1) towards the Bragg network sensors (9), where the second output sends the reflected signal by the Bragg network sensors (9) to a photodetector (3); a locking amplifier (4), configured to perform a dual function: (i) use its own reference signal to provide a harmonic signal for excitations of the set of piezoelectric actuators (6); and (ii) recovering the amplitude and phase of the sinusoidal deformity signals, in the same frequency components as the excitation signal, produced by the harmonically excited piezoelectric actuators (6); a power amplifier (5) configured to increase the excitation signal provided by the locking amplifier (4); a multiplexer (58) configured to control the phase and amplitude distribution of the harmonic excitation signal by the piezoelectric actuators (6); the photodetector (3) configured to detect the reflected light signal through the Bragg network sensors (9), transforming the detected light signal into an electrical signal and transmit the electrical signal to the locking amplifier (4); and a fiber optic multiplexer (2) configured to access more than one fiber optic in case the Bragg network sensors (9) are distributed over more than one optical fiber.
    [0006]
    6. System, according to claim 5, characterized by the fact that the locking amplifier (4) acts as a narrow bandpass filter that removes unwanted noise while allowing through the sinusoidal deformity signals to be measured.
    [0007]
    7. System, according to claim 6, characterized by the fact that the bandpass region of the narrow bandpass filter is configured by the reference signal, in which the reference signal is generated by a reference signal generator ( 52) to the locking amplifier where the reference signal is also supplied to the actuator set (6).
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    同族专利:
    公开号 | 公开日
    US10024756B2|2018-07-17|
    BR112017008942A2|2018-01-02|
    WO2016065446A1|2016-05-06|
    CN107438758A|2017-12-05|
    EP3213045A1|2017-09-06|
    CN107438758B|2020-10-09|
    EP3213045B1|2020-05-27|
    US20160116366A1|2016-04-28|
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    法律状态:
    2020-05-05| B06U| Preliminary requirement: requests with searches performed by other patent offices: suspension of the patent application procedure|
    2020-12-22| B09A| Decision: intention to grant|
    2021-03-02| B16A| Patent or certificate of addition of invention granted|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 21/10/2015, OBSERVADAS AS CONDICOES LEGAIS. |
    优先权:
    申请号 | 申请日 | 专利标题
    US14/526,226|2014-10-28|
    US14/526,226|US10024756B2|2014-10-28|2014-10-28|Method and system for structural health monitoring with frequency synchronization|
    PCT/BR2015/000163|WO2016065446A1|2014-10-28|2015-10-21|Method and system for structural health monitoring with frequency synchronization|
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