A monitoring method for local damage of structure

Abstract

The embodiment of the present invention discloses a monitoring method for local damage of a structure, including: constructing an elastic wave control structure to form an elastic wave control frequency band; arranging sensors and actuators to form an elastic wave control device; measuring the FRF curve of the target structure through simple harmonic excitation; correcting the formation of the loss valley of the FRF curve by the elastic wave control structure, and setting the FRF curve of the target structure when it is not damaged as a standard FRF curve; performing damage analysis to determine the target monitoring frequency and damage monitoring index; carrying out local damage monitoring, statistically measuring the damage index measurement value, and analyzing the change of the damage index to determine the local damage of the overall target structure. The technical solution provided by the embodiment of the present invention solves the problems that the existing algorithm monitoring method has a large data processing workload, it is difficult to achieve real-time monitoring, and the measurement data is affected by environmental noise, and the existing phononic crystal detection method is difficult to apply to the damage detection of limited-size structures in engineering.

Description

Technical Field

[0001] The present invention relates to, but is not limited to, the technical fields of structural self-detection, structural fault diagnosis and structural damage monitoring, and in particular to a monitoring method for local structural damage. Background Art

[0002] In the field of intelligent structure self-detection, structural fault diagnosis, and structural damage monitoring, the following monitoring methods are currently commonly used:

[0003] One is based on vibration signal damage identification. In terms of algorithms, the existing vibration signal-based structural damage monitoring methods mainly use signal processing algorithms, such as signal filtering, wavelet transform, differential amplification, fractal dimension and artificial intelligence. This structural monitoring method usually uses dynamic stiffness, damage factor, structural mode, and curvature mode as damage identification indicators. This type of algorithm monitoring method has a large data processing workload and is difficult to achieve real-time monitoring. In addition, since the measurement data is affected by environmental noise, the difficulty of data processing is further increased.

[0004] The other is the phononic crystal detection method. When using phononic crystal defect state detection for structural damage detection, it is necessary to draw the dispersion curve band gap and judge the damage from the elastic wave transition curve in the dispersion curve band gap. This detection method has the following problems: on the one hand, when certain types of structural damage occur, they may not cause obvious changes in the passband or elastic wave propagation mode; on the other hand, phononic crystals need to be arranged with a certain number of spatial periodicities (usually periods greater than 8) to form bandgap-regulated elastic waves. It is usually difficult to construct such multi-periodic structures to match the detection method, which is difficult to apply to structural damage detection of limited size in engineering. Summary of the invention

[0005] Purpose of the present invention: In order to solve the above-mentioned technical problems, an embodiment of the present invention provides a monitoring method for local structural damage, so as to solve the problems that the existing algorithm monitoring method has a large data processing workload, it is difficult to achieve real-time monitoring, and the measurement data is affected by environmental noise, and the existing phononic crystal detection method is difficult to apply to the detection of structural damage of limited size in engineering.

[0006] Technical solution of the present invention: An embodiment of the present invention provides a method for monitoring local damage of a structure, comprising:

[0007] Step 1: construct an elastic wave control structure according to the target structure measurement requirements to form an elastic wave control frequency band of the target structure at a specified medium and low frequency;

[0008] Step 2, determine the spatial distribution spacing between the sensor and the actuator to avoid the influence of elastic waves on the measurement when propagating in space;

[0009] Step 3, connecting the elastic wave control structure, the sensor and the actuator, and connecting the power supply, the signal source and the analysis equipment to form an elastic wave control device;

[0010] Step 4: Through simple harmonic excitation, the displacement frequency response function (FRF) of the target structure is measured by using a sensor; the elastic wave control structure is corrected for the formation of the loss valley of the FRF curve of the target structure, and the FRF curve of the target structure when it is undamaged is set as the standard FRF curve by examining the frequency position and amplitude changes of the propagation valley;

[0011] Step 5, performing damage analysis on the overall target structure equipped with the elastic wave control device to determine the target monitoring frequency and damage monitoring index;

[0012] Step 6, using the damage monitoring index to carry out local damage monitoring of the overall target structure, counting the damage index measurement values ​​in real time, and obtaining the damage index of the overall target structure;

[0013] Step 7: Analyze the changes in damage indicators to determine the local damage of the overall target structure.

[0014] Optionally, in the above-mentioned method for monitoring local damage of a structure, in said step 1,

[0015] The elastic wave control structure is composed of a local resonance superstructure and an array structure of inertial actuators;

[0016] By strongly coupling the constructed elastic wave control structure with the target structure to be measured, a new strong loss valley is formed in the target structure near the specified medium and low frequency bands.

[0017] Optionally, in the above-mentioned method for monitoring local damage of a structure, in said step 2,

[0018] The sensor and the actuator are located on both sides of the elastic wave control structure, and the distance between the sensor and the actuator and the elastic wave control structure is 2 cm to 10 cm respectively, and the position of the modal node is required to be avoided.

[0019] Optionally, in the above-mentioned method for monitoring local damage of a structure, step 3 comprises:

[0020] Step 3a, attaching the elastic wave control structure, the actuator, and the sensor to the upper surface of the target structure to be measured by means of structural adhesive, and connecting the actuator, the sensor, the power supply, the signal source, and the analysis equipment to form an elastic wave control device; or,

[0021] Optionally, in the above-mentioned method for monitoring local damage of a structure, step 3 comprises:

[0022] Step 3b, pre-packaging and curing the elastic wave control structure, sensor and actuator on a flexible glass fiber sheet (FR4) to form an integrated packaged elastic wave control device;

[0023] Step 3c: Use a multimeter and a vibration test analyzer to test the signal conduction and signal background noise of the packaged sensor device to ensure the reliability of the packaging process.

[0024] Optionally, in the above-mentioned method for monitoring local damage of a structure, step 5 comprises:

[0025] Step 51, performing damage analysis on the overall target structure on which the elastic wave control device is deployed;

[0026] Step 52: The absolute value of the difference between the amplitude of the FRF curve of the overall structure at the target monitoring frequency and the standard FRF curve at the corresponding frequency is used as a damage monitoring index.

[0027] Optionally, in the above-mentioned method for monitoring local damage of a structure, step 6 comprises:

[0028] Step 61, the actuator excites the overall target structure to vibrate under simple harmonic excitation;

[0029] Step 62, using a sensor to measure the local vibration displacement change of the surface of the overall target structure;

[0030] Step 63, analyzing the vibration signal measured by the sensor to obtain the frequency response function of the overall target structure, that is, the FRF curve of the overall target structure;

[0031] Step 64, calculating the average value of the FRF curve amplitude difference of the entire target structure in the working frequency band as a damage index.

[0032] Optionally, in the above-mentioned method for monitoring local damage of a structure,

[0033] According to the damage index change analysis results in step 7, a real-time warning is issued when the difference is greater than 2dB; the index value is 0 when no damage occurs, and it is marked as a damaged state when the index is greater than 2dB. The 0-2dB range is the range to be verified.

[0034] Beneficial effects of the present invention: The embodiment of the present invention provides a monitoring method for local damage of a structure. Based on the design concept of local resonance metamaterial or inertial actuator, on the one hand, it can realize the adjustment of certain medium and low frequency troughs of the vibration transmission rate curve and the frequency response curve, suppress the propagation of elastic waves, and design elastic wave propagation troughs in the medium and low frequency range; on the other hand, by monitoring the change in the amplitude of the elastic wave near the adjustable propagation trough to determine whether elastic wave transmission occurs, it is possible to determine whether damage occurs locally in the structure. The monitoring method for local damage of a structure provided by the embodiment of the present invention has the following beneficial effects:

[0035] 1. The technical solution of the present invention can be used to pre-modulate the fault characteristic signals of local structural damage or critical area damage (such as cracks, composite material delamination and stiffness reduction, etc.);

[0036] 2. The technical solution of the present invention improves the shortcomings of the vibration signal damage identification method, such as the difficulty in distinguishing characteristic signals and the need to match specific complex calculation algorithms. The method of the present invention can directly perform fault monitoring through vibration transmissibility, detectors, and mutual spectrum analysis.

[0037] 3. Compared with the phononic crystal detection method, which requires drawing dispersion curves and judging damage from the elastic wave transition curve in the band gap of the dispersion curve, the technical solution of the present invention has more engineering application prospects. For the vibration transmissibility curve or frequency response curve, the structural damage can be evaluated from two dimensions: frequency and amplitude. The pre-emphasis control effect of the local resonant structure or inertial actuator on the propagation of elastic waves makes the changes in stiffness, damping or dynamic mass caused by local damage to the structure clearly reflected in the natural frequency and resonance amplitude, effectively improving the prediction efficiency.

[0038] 4. By adopting the technical solution of the present invention, the local resonance structure and the inertial actuator structure can modulate (attenuate or enhance transmission) the medium and low frequency elastic waves with fewer units in the local space of the structure, which is convenient for arrangement and implementation in limited engineering structures; specifically, compared with the traditional monitoring method, the technical solution of the present invention adopts fewer sensors and actuators (for example, 2-4), and the laying and wiring are more convenient;

[0039] 5. In the technical solution of the present invention, the elastic wave control structure, sensor, and actuator can be integrated with the polyimide film (FPC) to be prepared as a flexible sensing / actuating functional layer. The flexible functional layer and the structure to be measured can be solidified by integrated layer laying; the consistency and stability of the sensor laying process are further improved, and the background noise of the output signal is improved; in addition, the signal networking measurement solution is simple, including a flexible sensing / actuating functional layer, a vibration signal generator and analyzer.

[0040] It can be seen that the monitoring method for local structural damage provided by the embodiment of the present invention provides a new idea for local structural damage monitoring. It completes the pre-modulation of elastic waves in the structure to be tested based on the cutting-edge super-structure design method, greatly simplifies the numerical analysis strategy for real-time detection of structural damage based on vibration parameters, and improves the sensitivity of the displacement response amplitude to local structural damage at a specific frequency. In the design of the elastic wave control structure, the overall packaging is carried out, and fewer sensor nodes, simple algorithms, and mature processes are used for low-cost and reliability design. Compared with the traditional method, it saves manpower and material resources in the system construction, debugging and actual service, and has better economy and maintainability. In addition, through pre-packaging, it can be integrated with composite structural parts for curing and molding. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The accompanying drawings are used to provide a further understanding of the technical solution of the present invention and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of the present invention and do not constitute a limitation on the technical solution of the present invention.

[0042] Figure 1 A schematic diagram of an overall target structure in which an elastic wave control device is deployed in a method for monitoring local damage of a structure provided by an embodiment of the present invention;

[0043] Figure 2 A schematic diagram showing the comparison effect of the FRF curves of the target structure before and after the elastic wave control device is used in the monitoring method for local damage of the structure provided by the embodiment of the present invention;

[0044] Figure 3 A schematic diagram of the comparison effect of FRF curves obtained by measuring the overall target structure before and after damage in the monitoring method for local structural damage provided by an embodiment of the present invention;

[0045] Figure 4 A schematic diagram of changes in damage indicators of an overall target structure in a method for monitoring local structural damage provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solution and advantages of the present invention more clear, the embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the embodiments and features in the embodiments of the present application can be combined with each other arbitrarily without conflict.

[0047] The present invention provides the following specific embodiments which can be combined with each other. The same or similar concepts or processes may not be described in detail in some embodiments.

[0048] Figure 1A schematic diagram of an overall target structure in which an elastic wave control device is deployed in a method for monitoring local structural damage provided in an embodiment of the present invention.

[0049] Example 1

[0050] This embodiment 1 takes the vibration signal monitoring of a stepped beam structure (aviation, aerospace structure, bridge, key parts of a composite material functional structure, etc.) as an example to illustrate the implementation process of the monitoring method for local structural damage provided by the embodiment 1 of the present invention, including the following steps:

[0051] Step 1: Design an elastic wave control structure according to the target structure measurement requirements. The elastic wave control structure can generally be composed of an array structure such as a local resonance superstructure and an inertial actuator. Figure 1 The typical step beam structure shown is designed with an elastic control structure, so that the step beam structure forms a new strong loss valley near 400 Hz in the low frequency band. Figure 2 A schematic diagram of the FRF curve of the target structure before and after the elastic wave control device is used in the monitoring method for local structural damage provided by an embodiment of the present invention, Figure 2 The monitoring method provided by the embodiment of the present invention is used to illustrate Figure 1 The schematic diagram of the comparison of the FRF curves of the elastic wave control structure designed for the typical step beam structure before and after the control is shown. It can be seen that a new strong loss valley is formed near 400Hz in the low frequency band. This kind of strong loss valley is formed due to the strong coupling between the elastic wave control structure and the measured structure, which controls the specific low-frequency elastic waves in the structure;

[0052] When elastic waves propagate in a locally damaged structure, they are more easily observed by damage indicators.

[0053] Step 2: Determine the spatial distribution distance between the sensor and the actuator. Figure 1 As shown, PZT piezoelectric sheet (i.e. actuator) and flexible sensor (such as piezoelectric PVDF, strain gauge, etc.)

[0054] They are located on both sides of the elastic wave control structure, generally with a spacing of 2 cm to 10 cm, and try to avoid the modal node position.

[0055] Step 3: Glue the elastic wave control structure, actuator, and sensor to the upper surface of the structure using structural adhesive. Figure 1 As shown, the actuator, sensor, power supply, signal source and analysis equipment are connected. The power supply, signal source and power supply processing module can be built into the vibration signal generator and analyzer.

[0056] Step 4, measuring the transfer function between the sensor and the actuator, that is, measuring the displacement frequency response function of the target structure by simple harmonic excitation, that is, obtaining the FRF curve of the target structure. In this step, it is also required to correct the formation of the loss valley of the FRF curve of the target structure by the designed elastic wave control structure, and specifically, the frequency position and the amplitude change of the propagation valley can be examined. In addition, the FRF curve of the target structure when it is undamaged is set to the standard FRF curve. In this embodiment 1, refer to Figure 2 The comparison of FRF curves before and after the target structure regulation is shown. Figure 2 It can be seen that for this step beam, two large loss valleys appear in the control frequency band within the range of [400 500] Hz. For other structures to be tested, the elastic wave loss or enhanced control structure in the medium and low frequency band [1002000] Hz can be designed in the same way to expand the existing detection frequency band based on vibration or sound waves to medium and low frequencies. In the same medium, because the wavelength of medium and low frequency elastic waves is longer than that of high frequency elastic waves, the propagation distance is longer, which can effectively avoid the interference of other structures on the control waves, thereby achieving effective control. Furthermore, the FRF curve when there is no damage is set as the standard FRF curve.

[0057] Step 5: Perform damage analysis on the overall target structure after the elastic wave control device is attached to determine the target monitoring frequency and damage monitoring index. Specifically, compare the 5FRF curve amplitude (or the average amplitude within the frequency range) at the monitoring frequency point with the FRF standard at the corresponding frequency point.

[0058] The absolute value of the difference between the two directrix curves is used as the damage monitoring index.

[0059] For example, based on Figure 2 The position of the medium-strong loss valley, the frequency point of the overall target structure in this embodiment 1 is selected as 420Hz, and the amplitude of the displacement response at this frequency point is sensitive to the damage change, such as

[0060] Figure 3 , which is a schematic diagram of the comparison effect of the FRF curves of the target structure to be measured before and after damage in an embodiment of the present invention.

[0061] Step 6: Use damage monitoring indicators to carry out local damage monitoring of the overall target structure and count the damage indicator measurement values ​​in real time.

[0062] Figure 4 Shown is a schematic diagram of the change in damage index of the overall target structure in an embodiment of the present invention. Figure 4 The schematic diagram of the change of the analysis damage index obtained by local damage monitoring is shown in FIG. The specific method of performing local damage monitoring in this step is:

[0063] ① The PZT actuator excites the vibration of the overall target structure under simple harmonic excitation (the excitation sweep range covers the working frequency point, such as in this embodiment 1, it can be selected to cover the [300 500] Hz interval) → ② The sensor measures the local vibration displacement change on the surface of the overall target structure → ③ By analyzing the vibration signal, the frequency response function (FRF curve) of the overall target structure is obtained → ④ The average value of the FRF amplitude difference of the overall target structure in the working frequency band is calculated as the damage indicator (in this embodiment 1, the average difference of 3 measurements of the 420 Hz valley amplitude is selected).

[0064] Step 7: Analyze the damage index changes to determine the local damage of the target structure, and issue a real-time warning when the difference is greater than 2dB. Figure 4 As shown, when there is no damage, the index value is 0, and when the index is greater than 2dB, it is calibrated as a damaged state. The 0-2dB range is the range to be verified, which can be assisted by ground non-destructive testing (C scan).

[0065] Example 2

[0066] This embodiment 2 still takes the real-time monitoring of damage signals of a typical step beam structure as an example to illustrate the monitoring embodiment of a composite material structure using bag pressing and curing processes. The implementation process of this embodiment is briefly described, including the following steps:

[0067] Step 1: According to the target structure measurement requirements, an elastic wave control structure is designed based on the local common low-frequency elastic wave control mechanism, such as a local resonance array, to achieve a specific low- and medium-frequency elastic wave control frequency band. Figure 1 The typical step beam structure shown in the figure is designed with an elastic wave control structure, so that the step beam structure forms a new strong loss valley near 400Hz in the low frequency band (such as Figure 2 By constructing an elastic wave control structure, it is easier to observe the damage indicator when the elastic wave propagates in the local damaged structure.

[0068] Step 2: Determine the spatial distribution distance between the sensor and the actuator to avoid the influence of elastic waves on the measurement when propagating in space. Figure 1 As shown in the figure, the PZT piezoelectric sheet (i.e., the actuator) and the flexible sensor (such as piezoelectric PVDF, strain gauge, etc.) are respectively located on both sides of the elastic wave control structure. For the composite structure, the effects of carbon fiber and resin are considered, the spacing is sub-wavelength scale, and the structural mode node position is avoided as much as possible.

[0069] Step 3: Pre-package and solidify the elastic wave control structure, actuator, and sensor on a flexible glass fiber sheet (FR4) with a thickness of about 1 mm to form an integrated package to form an elastic wave control device with a package structure, and ensure that the end faces of the actuator and sensor are level.

[0070] In the specific implementation of this step, the power supply can be built into the vibration signal generator and analyzer, and the signal and power supply processing module and the elastic wave control module are integrated into a package.

[0071] Step 4: Use a multimeter and a vibration test analyzer to test the signal conduction and signal background noise of the packaged sensor device to ensure the reliability of the packaging process.

[0072] In this embodiment 2, the elastic wave control structure, sensor, and actuator can be integrated with the polyimide film (FPC) to form a flexible sensing / actuating functional layer, and the flexible functional layer and the structure to be measured can be solidified by integrated layer laying. The consistency and stability of the sensor laying process are further improved, and the background noise of the output signal is improved. In addition, the signal networking measurement scheme is simple, including a flexible sensing / actuating functional layer, a vibration signal generator, and an analyzer.

[0073] Step 5: Through simple harmonic excitation, the displacement frequency response function of the target structure is measured by using a sensor to obtain the FRF curve of the target structure. The elastic wave control structure is corrected to adjust the formation of the loss valley of the FRF curve of the target structure, and the frequency position and amplitude changes of the propagation valley are examined. The FRF curve of the target structure without damage is set as the standard FRF curve.

[0074] Step 6: Perform damage analysis on the overall target structure behind the packaged elastic wave control device to determine the target monitoring frequency and damage monitoring index. Specifically, the absolute value of the difference between the FRF curve amplitude at the monitoring frequency point (or the average amplitude within the frequency range) and the FRF standard curve at the corresponding frequency point is used as the damage monitoring index.

[0075] Step 7: Use damage monitoring indicators to carry out local damage monitoring of the overall target structure and count the damage indicator measurement values ​​in real time.

[0076] like Figure 4 As shown, the specific method of performing local damage monitoring in the steps is: ① The PZT actuator excites the vibration of the overall target structure under a simple harmonic excitation force (the excitation sweep range covers the working frequency point, such as in this embodiment 2, it can be selected to cover the [300 500] Hz interval) → ② The sensor measures the local vibration displacement change on the surface of the overall target structure → ③ By analyzing the vibration signal, the frequency response function (FRF curve) of the overall target structure is obtained → ④ The average value of the FRF amplitude difference of the overall target structure in the working frequency band is calculated as the damage index (in this embodiment 2, the average difference of 3 measurements of the 420 Hz valley amplitude is selected).

[0077] Step 8: Analyze the damage index changes to determine the local damage of the target structure, and issue a real-time warning when the difference is greater than 2dB. Figure 4As shown, when there is no damage, the index value is 0, and when the index is greater than 2dB, it is calibrated as a damaged state. The 0-2dB range is the range to be verified, which can be assisted by ground non-destructive testing (C scan).

[0078] It should be noted that steps 1 and 2 of the above-mentioned embodiments 1 and 2 of the present invention are two key steps in the monitoring method for local structural damage provided by the present invention. The design of the elastic wave control structure in step 1 must be coupled with the structure to be measured, and the geometric parameters and physical parameters need to be optimized to obtain a better low-frequency elastic wave control frequency band. In step 2, the relative distance between the actuator and the sensor must be adjusted, and the pasting position must be matched with the modal distribution of the structure to be measured to ensure that the sensor output signal is stable and not disturbed.

[0079] The monitoring method for local damage of a structure provided by an embodiment of the present invention is based on the design concept of local resonance metamaterial or inertial actuator. On the one hand, it can realize the adjustment of certain medium and low frequency troughs of the vibration transmissibility curve and the frequency response curve, suppress the propagation of elastic waves, and design elastic wave propagation troughs in the medium and low frequency range; on the other hand, by monitoring the change in the amplitude of the elastic wave near the adjustable propagation trough to determine whether elastic wave transmission occurs, it can be determined whether damage occurs locally in the structure. The monitoring method for local damage of a structure provided by an embodiment of the present invention has the following beneficial effects:

[0080] 1. The technical solution of the present invention can be used to pre-modulate the fault characteristic signals of local structural damage or critical area damage (such as cracks, composite material delamination and stiffness reduction, etc.);

[0081] 2. The technical solution of the present invention improves the shortcomings of the vibration signal damage identification method, such as the difficulty in distinguishing characteristic signals and the need to match specific complex calculation algorithms. The method of the present invention can directly perform fault monitoring through vibration transmissibility, detectors, and mutual spectrum analysis.

[0082] 3. Compared with the phononic crystal detection method, which requires drawing dispersion curves and judging damage from the elastic wave transition curve in the band gap of the dispersion curve, the technical solution of the present invention has more engineering application prospects. For the vibration transmissibility curve or frequency response curve, the structural damage can be evaluated from two dimensions: frequency and amplitude. The pre-emphasis control effect of the local resonant structure or inertial actuator on the propagation of elastic waves makes the changes in stiffness, damping or dynamic mass caused by local damage to the structure clearly reflected in the natural frequency and resonance amplitude, effectively improving the prediction efficiency.

[0083] 4. By adopting the technical solution of the present invention, the local resonance structure and the inertial actuator structure can modulate (attenuate or enhance transmission) the medium and low frequency elastic waves with fewer units in the local space of the structure, which is convenient for arrangement and implementation in limited engineering structures; specifically, compared with the traditional monitoring method, the technical solution of the present invention adopts fewer sensors and actuators (for example, 2-4), and the laying and wiring are more convenient;

[0084] 5. In the technical solution of the present invention, the elastic wave control structure, sensor, and actuator can be integrated with the polyimide film (FPC) to be prepared as a flexible sensing / actuating functional layer. The flexible functional layer and the structure to be measured can be solidified by integrated layer laying; the consistency and stability of the sensor laying process are further improved, and the background noise of the output signal is improved; in addition, the signal networking measurement solution is simple, including a flexible sensing / actuating functional layer, a vibration signal generator and analyzer.

[0085] It can be seen that the monitoring method for local structural damage provided by the embodiment of the present invention provides a new idea for local structural damage monitoring. It completes the pre-modulation of elastic waves in the structure to be tested based on the cutting-edge super-structure design method, greatly simplifies the numerical analysis strategy for real-time detection of structural damage based on vibration parameters, and improves the sensitivity of the displacement response amplitude to local structural damage at a specific frequency. In the design of the elastic wave control structure, the overall packaging is carried out, and fewer sensor nodes, simple algorithms, and mature processes are used for low-cost and reliability design. Compared with the traditional method, it saves manpower and material resources in the system construction, debugging and actual service, and has better economy and maintainability. In addition, through pre-packaging, it can be integrated with composite structural parts for curing and molding.

[0086] The following describes the application scenarios and application methods of the monitoring method for local structural damage provided by the embodiment of the present invention:

[0087] 1. For local monitoring of key areas of aviation and aerospace structures, the technical solution of the present invention can quickly build a monitoring system for local vulnerable structures;

[0088] 2. Develop sensing strategies and instrument systems based on vibration monitoring based on local elastic wave modulation of local resonant structures or inertial actuators;

[0089] 3. The elastic wave control structure using the technical solution of the present invention can suppress the vibration of the aircraft engine nacelle connection area, and carry out local damage detection in combination with the technical solution of the present invention;

[0090] 4. The technical solution of the present invention is applicable to the solution of monitoring the main structure by using the structural transmissibility and displacement response changes after the elastic wave propagates in the structure and is further suppressed or strengthened by the local resonance structure or inertial actuator. For example, the technical solution of the present invention is used to extract and amplify the weak signals of medium and low frequencies in medical monitoring equipment to achieve accurate recognition of biological signals;

[0091] Another example is real-time measurement of bridge deck overload in the field of bridge overload monitoring.

[0092] Although the embodiments disclosed in the present invention are as above, the above contents are only embodiments adopted to facilitate understanding of the present invention and are not intended to limit the present invention. Any technician in the field to which the present invention belongs may make any modification and change in the form and details of implementation without departing from the spirit and scope disclosed in the present invention, but the patent protection scope of the present invention shall still be subject to the scope defined in the attached claims.

Claims

1. A method for monitoring local damage of a structure, characterized in that: include: Step 1: construct an elastic wave control structure according to the target structure measurement requirements to form an elastic wave control frequency band of the target structure at a specified medium and low frequency; Step 2, determine the spatial distribution spacing between the sensor and the actuator to avoid the influence of elastic waves on the measurement when propagating in space; Step 3, connecting the elastic wave control structure, the sensor and the actuator, and connecting the power supply, the signal source and the analysis equipment to form an elastic wave control device; Step 4: Through simple harmonic excitation, the displacement frequency response function (FRF) of the target structure is measured by using a sensor; the elastic wave control structure is corrected for the formation of the loss valley of the FRF curve of the target structure, and the FRF curve of the target structure when it is undamaged is set as the standard FRF curve by examining the frequency position and amplitude changes of the propagation valley; Step 5, performing damage analysis on the overall target structure equipped with the elastic wave control device to determine the target monitoring frequency and damage monitoring index; Step 6, using the damage monitoring index to carry out local damage monitoring of the overall target structure, counting the damage index measurement values ​​in real time, and obtaining the damage index of the overall target structure; Step 7, by analyzing the changes in damage indicators, to determine the local damage of the overall target structure; In the step 1, The elastic wave control structure is composed of a local resonance superstructure and an array structure of inertial actuators; Through the strong coupling between the constructed elastic wave control structure and the target structure to be measured, a new strong loss valley is formed in the target structure near the specified low and medium frequency bands; The step 3 comprises: Step 3b, pre-packing and curing the elastic wave control structure, sensor and actuator on a flexible glass fiber sheet to form an integrated packaged elastic wave control device; Step 3c, using a multimeter and a vibration test analyzer to test the signal conduction and signal background noise of the packaged sensor device to ensure the reliability of the packaging process; The step 5 comprises: Step 51, performing damage analysis on the overall target structure on which the elastic wave control device is deployed; Step 52: The absolute value of the difference between the amplitude of the FRF curve of the overall structure at the target monitoring frequency and the standard FRF curve at the corresponding frequency is used as a damage monitoring index.

2. The method for monitoring local damage of a structure according to claim 1, characterized in that: In the step 2, The sensor and the actuator are located on both sides of the elastic wave control structure, and the distance between the sensor and the actuator and the elastic wave control structure is 2 cm to 10 cm respectively, and the position of the modal node is required to be avoided.

3. The method for monitoring local damage of a structure according to claim 1, characterized in that: The step 6 comprises: Step 61, the actuator excites the overall target structure to vibrate under simple harmonic excitation; Step 62, using a sensor to measure the local vibration displacement change of the surface of the overall target structure; Step 63, analyzing the vibration signal measured by the sensor to obtain the frequency response function of the overall target structure, that is, the FRF curve of the overall target structure; Step 64, calculating the average value of the FRF curve amplitude difference of the entire target structure in the working frequency band as a damage index.

4. The method for monitoring local damage of a structure according to claim 1, characterized in that: According to the damage index change analysis results in step 7, a real-time warning is issued when the difference is greater than 2dB; the index value is 0 when no damage occurs, and it is marked as a damaged state when the index is greater than 2dB. The 0-2dB range is the range to be verified.

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