CN107917957B - Damage detection method for plate-shaped structure - Google Patents
Damage detection method for plate-shaped structure Download PDFInfo
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Abstract
The invention relates to a damage detection method of a plate-shaped structure, which comprises the following steps: s1: an array of piezoelectric transducers arranged in a plate-shaped structure; s2: establishing a reference database; s3: collecting a current signal and a current temperature of a plate-shaped structure to be detected; s4: calculating a difference signal, the difference signal being the current baseline signal-the current signal in the reference database; s5: and calculating a damage index according to the difference signal and the current baseline signal, judging that the plate-shaped structure to be detected is damaged if the damage index exceeds a preset threshold value, and judging that the plate-shaped structure to be detected is not damaged if the damage index does not exceed the preset threshold value. The damage detection method adopts a temperature compensation mode, weakens the influence caused by large temperature change in the damage detection process of the plate-shaped structure through the piezoelectric transducer, improves the detection precision and avoids potential safety hazards.
Description
Technical Field
The invention relates to the technical field of structure detection, in particular to a damage detection method for a plate-shaped structure of a railway vehicle.
Background
At present, the piezoelectric intelligent detection technology is used as one of structural health detection technologies, can perform regional detection, is easy to be fused with a structure, and is widely applied to damage detection of composite materials and metal structures. In the prior art, in the method for detecting the structural damage through the piezoelectric transducer, because the detection environment is mostly indoors and the environmental condition is relatively stable, the influence of the temperature on the detection result is not considered, but the change of the temperature can cause the structure to have the phenomenon of expansion with heat and contraction with cold, the propagation of the wave in the structure to be detected is influenced, and the precision of the structural damage detection is further influenced.
When damage detection is carried out on key parts of a train body of a motor train unit, due to the fact that the difference between the temperature of the external environment or the temperature of a transformer in a working state and the temperature of a transformer in a stopping state when a train runs is large, the temperature of key structures around the key structures is correspondingly increased, if damage detection is carried out on the key structures, piezoelectric transducers are used for detecting the damage of the key structures, but the temperature factor is not considered, the detection accuracy is influenced, and great potential safety hazards exist.
Disclosure of Invention
The invention aims to provide a damage detection method of a plate-shaped structure, which adopts a temperature compensation mode to weaken the influence caused by large temperature change in the damage detection process of the plate-shaped structure through a piezoelectric transducer, improves the detection precision and avoids the potential safety hazard.
In order to solve the technical problem, the invention provides a damage detection method of a plate-shaped structure, which comprises the following steps:
s1: an array of piezoelectric transducers arranged in a plate-shaped structure;
s2: establishing a reference database:
(1) the piezoelectric transducer excites the undamaged plate-shaped structure at a specific excitation frequency to generate lamb waves;
(2) collecting a plurality of groups of baseline signals and corresponding temperatures, wherein each baseline signal is a characteristic value of a first arrival wave of the lamb waves;
(3) storing each set of the baseline signals and the temperatures corresponding thereto in the reference database;
s3: collecting the current signal and the current temperature of the plate-shaped structure to be detected by the same method as the method (1) and the method (2) in the step S2;
s4: calculating a difference signal, wherein the difference signal is a current baseline signal-a current signal, and the current baseline signal is a baseline signal corresponding to the current temperature in the reference database;
s5: and calculating a damage index according to the difference signal and the current baseline signal, judging that the plate-shaped structure to be detected is damaged if the damage index exceeds a preset threshold value, and judging that the plate-shaped structure to be detected is not damaged if the damage index does not exceed the preset threshold value.
The detection scheme of the invention is that a piezoelectric transducer is used as an exciter, a voltage excitation signal is converted into a stress Lamb wave (Lamb wave) which is transmitted in a plate-shaped structure by utilizing the inverse piezoelectric effect of the piezoelectric transducer, the Lamb wave is transmitted to the vicinity of the piezoelectric transducer which is used as a sensor, and a mechanical vibration signal is converted into a voltage signal by utilizing the piezoelectric effect of the piezoelectric transducer and is output. Because the voltage excitation signal is constant, the voltage signal to be detected and the voltage signal in the complete state of the plate-shaped structure are contrastingly analyzed, namely, a baseline method is adopted to judge whether the plate-shaped structure is damaged or not. The plate-shaped structure is not limited to a flat plate structure, and can also have a corresponding curved surface structure, and the size of the curved surface structure in the thickness direction is smaller than that in the length direction and that in the width direction, so that the piezoelectric transducer can generate lamb waves instead of Rayleigh waves after being excited by a specific excitation frequency.
The piezoelectric transducer array is arranged on the plate-shaped structure, the piezoelectric transducer array can be designed according to the specific condition of the plate-shaped structure, and the specific number of the piezoelectric transducer array is not limited, so that the piezoelectric transducer array can be used for increasing the number of the piezoelectric transducers for the plate-shaped structure with larger volume, and is suitable for damage detection of the plate-shaped structure in a large area.
And establishing a reference database, acquiring baseline signals and temperatures of a plurality of groups of plate-shaped structures when the plate-shaped structures are in a complete state, namely a non-damage state, and storing the acquired baseline signals and temperatures in the reference database as a reference for judging structural damage. Wherein the acquiring of the baseline signal comprises: (1) the piezoelectric transducer excites the undamaged plate-shaped structure at a specific excitation frequency to generate lamb waves; (2) collecting a plurality of groups of baseline signals and corresponding temperatures, wherein each baseline signal is a characteristic value of a first arrival wave of lamb waves; (3) and storing the collected groups of baseline signals and the temperatures corresponding to the baseline signals in a reference database. At this time, the baseline data in the reference database has a certain correspondence with the temperature.
When the plate-shaped structure is used, the interior of the plate-shaped structure can be damaged, and when the plate-shaped structure is detected, the plate-shaped structure is a plate-shaped structure to be detected. Collecting a current signal S _ c and a current temperature t for the plate-shaped structure to be tested, wherein the collection of the current signal is the same as the collection of the baseline signal in S2: (1) the piezoelectric transducer excites the plate-shaped structure to be tested at a specific excitation frequency to generate lamb waves; (2) and acquiring a current signal and a current temperature, wherein the current signal is a characteristic value of a first arrival wave of the lamb wave.
And according to the corresponding relation between the baseline signal and the temperature in the baseline database, determining the current baseline signal s _ b by combining the current temperature, and calculating a difference signal s _ s, wherein s _ s is s _ b-s _ c.
And finally, calculating a damage index DI according to the difference signal s _ s and the current baseline signal s _ b, judging that the plate-shaped structure to be detected is damaged if the damage index DI exceeds a preset threshold value, and judging that the plate-shaped structure to be detected is not damaged if the damage index DI does not exceed the preset threshold value. The preset threshold is set according to the installation position and strength requirements of the plate-shaped structure, and is not specifically limited herein, when the damage index exceeds the preset threshold, it is indicated that the plate-shaped structure needs to be repaired or replaced so as to avoid danger, and when the damage index does not exceed the preset threshold, the plate-shaped structure has no defect or has small defect in a controllable range, has no danger, and can be continuously used.
That is, in the process of detecting the damage of the plate-shaped structure by using the baseline method, the baseline signal when the difference signal is calculated is the baseline signal corresponding to the current temperature in the reference database, namely, the temperature compensation is considered when the difference signal is calculated, so that the influence of the temperature change on the damage detection of the piezoelectric transducer is effectively weakened, the accuracy of the detection result is not influenced even if the environmental temperature is changed, the damage detection precision is improved, and the potential safety hazard is avoided.
Optionally, the damage index is the energy of the difference signal/the energy of the current baseline signal, wherein the energy of the signal is calculated according to the following formula:
wherein t ise、tsRespectively, the start-stop time of the interval of the first arrival wave of the lamb wave, and s (t) is the voltage signal detected by the piezoelectric transducer.
Optionally, in S2, if the energy of the baseline signal meets a specific gaussian distribution condition, the energy of the baseline signal is included in the reference database, and if the energy of the baseline signal does not meet the specific gaussian distribution condition, the start-stop time of the interval of the first arrival wave of the lamb wave or the arrangement of the piezoelectric transducer array in S1 is detected.
Optionally, in S5, if the damage index does not exceed the preset threshold and the energy of the current signal meets a specific gaussian distribution condition of the energy of the baseline signal in the reference database, the current signal and the current temperature are included in the reference database.
Optionally, the specific gaussian distribution condition is a gaussian distribution in a frequency range of 5% to 95%.
Optionally, the filtering and reconstructing of the signal are performed in both the process of acquiring the baseline signal and the process of acquiring the current signal.
Optionally, the filtering is performed in a band-pass manner.
Optionally, a start-stop time of an interval of a first arrival wave of the reconstructed signal is determined using a wavelet transform.
Optionally, the current baseline signal is a baseline signal determined by fitting a least squares method to a relationship between a characteristic value of each first arrival wave in the reference database and a temperature, and combining the current temperature in S3.
Drawings
FIG. 1 is a graph showing the dispersion of an aluminum alloy sheet;
fig. 2 is a flow chart of a damage detection method of a plate-shaped structure according to an embodiment of the present invention.
Detailed Description
In order to make the technical solutions of the present invention better understood by those skilled in the art, the present invention will be further described in detail with reference to the accompanying drawings and specific embodiments.
The embodiment of the invention provides a damage detection method of a plate-shaped structure, which comprises the following steps:
s1: an array of piezoelectric transducers arranged in a plate-shaped structure;
s2: establishing a reference database:
(1) the piezoelectric transducer excites the undamaged plate-shaped structure at a specific excitation frequency to generate lamb waves;
(2) collecting a plurality of groups of baseline signals and corresponding temperatures, wherein each baseline signal is a characteristic value of a first arrival wave of lamb waves;
(3) storing each group of baseline signals and the corresponding temperature in a reference database;
s3: collecting the current signal and the current temperature of the plate-shaped structure to be detected by the same method as the method (1) and the method (2) in the step S2;
s4: calculating a difference signal as a current baseline signal-a current signal, the current baseline signal being a baseline signal in the reference database corresponding to the current temperature;
s5: and calculating a damage index according to the difference signal and the current baseline signal, judging that the plate-shaped structure to be detected is damaged if the damage index exceeds a preset threshold value, and judging that the plate-shaped structure to be detected is not damaged if the damage index does not exceed the preset threshold value.
The detection scheme of the embodiment of the invention is that the piezoelectric transducer is used as an exciter, a voltage excitation signal is converted into a stress Lamb wave (Lamb wave) which is transmitted in a plate-shaped structure by utilizing the inverse piezoelectric effect of the piezoelectric transducer, the Lamb wave is transmitted to the vicinity of the piezoelectric transducer which is used as a sensor, and a mechanical vibration signal is converted into a voltage signal by utilizing the piezoelectric effect of the piezoelectric transducer and is output. Because the voltage excitation signal is constant, the voltage signal to be detected and the voltage signal in the complete state of the plate-shaped structure are contrastingly analyzed, namely, a baseline method is adopted to judge whether the plate-shaped structure is damaged or not. The plate-shaped structure is not limited to a flat plate structure, and can also have a corresponding curved surface structure, and the size of the curved surface structure in the thickness direction is smaller than that in the length direction and that in the width direction, so that the piezoelectric transducer can generate lamb waves instead of Rayleigh waves after being excited by a specific excitation frequency.
The specific excitation frequency is determined according to the frequency dispersion characteristics of the structure, taking an aluminum alloy plate-shaped structure as an example, fig. 1 is a frequency dispersion curve of an aluminum alloy plate, the horizontal axis is a frequency thickness product (f · d), the vertical axis is a group velocity, the group velocity is a distance between piezoelectric transducers divided by an arrival time of a first arrival wave, and the excitation frequency (such as 250kHz) is usually selected in a selected region in the figure, so that the obtained first arrival wave only includes an S0 mode or an a0 mode, and the signal is relatively simple and easy to extract and analyze, and meanwhile, boundary reflection waves can be avoided from being mixed.
The piezoelectric transducer array is arranged on the plate-shaped structure, the piezoelectric transducer array can be designed according to the specific condition of the plate-shaped structure, and the specific number of the piezoelectric transducer array is not limited, so that the piezoelectric transducer array can be used for increasing the number of the piezoelectric transducers for the plate-shaped structure with larger volume, and is suitable for damage detection of the plate-shaped structure in a large area.
Establishing a reference database, collecting baseline signals and temperatures of a plurality of groups of plate-shaped structures when the plate-shaped structures are in a complete state, namely a non-damage state, storing the collected baseline signals and temperatures in the reference database as a reference for judging structural damage, and determining the corresponding relation between the baseline signals and the temperatures according to the baseline signals and the temperatures. Wherein the acquiring of the baseline signal comprises: (1) the piezoelectric transducer excites the undamaged plate-shaped structure at a specific excitation frequency to generate lamb waves; (2) collecting a plurality of groups of baseline signals and corresponding temperatures, wherein each baseline signal is a characteristic value of a first arrival wave of lamb waves; (3) and storing the collected groups of baseline signals and the temperatures corresponding to the baseline signals in a reference database.
When the plate-shaped structure is used, the interior of the plate-shaped structure can be damaged, and when the plate-shaped structure is detected, the plate-shaped structure is a plate-shaped structure to be detected. Collecting a current signal S _ c and a current temperature t for the plate-shaped structure to be tested, wherein the collection of the current signal is the same as the collection of the baseline signal in S2: (1) the piezoelectric transducer excites the plate-shaped structure to be tested at a specific excitation frequency to generate lamb waves; (2) and acquiring a current signal and a current temperature, wherein the current signal is a characteristic value of a first arrival wave of the lamb wave.
And according to the corresponding relation between the baseline signal and the temperature in the baseline database, determining the current baseline signal by combining the current temperature, and calculating a difference signal s _ s which is the current baseline signal s _ b-the current signal s _ c.
And finally, calculating a damage index DI according to the difference signal s _ s and the current baseline signal s _ b, judging that the plate-shaped structure to be detected is damaged if the damage index DI exceeds a preset threshold value, and judging that the plate-shaped structure to be detected is not damaged if the damage index DI does not exceed the preset threshold value. The preset threshold is set according to the installation position and strength requirements of the plate-shaped structure, and is not specifically limited herein, when the damage index exceeds the preset threshold, it is indicated that the plate-shaped structure needs to be repaired or replaced so as to avoid danger, and when the damage index does not exceed the preset threshold, the plate-shaped structure has no defect or has small defect in a controllable range, has no danger, and can be continuously used.
That is to say, in the process of detecting the damage of the plate-shaped structure by using the baseline method, the baseline signal when the difference signal is calculated is the baseline signal corresponding to the current temperature in the reference database, that is, the temperature compensation is considered when the difference signal is calculated, so that the influence of the temperature change on the damage detection of the piezoelectric transducer is effectively weakened, even if the environmental temperature changes, the accuracy of the detection result is not influenced, the damage detection precision is improved, and the potential safety hazard is avoided.
In the above embodiment, the damage index DI is calculated from the ratio of the energy E _ s of the difference signal s _ s and the energy E _ b of the current baseline signal s _ b, i.e., DI — E _ s/E _ b. The energy of the signal is calculated according to the following energy calculation formula:
wherein, te、tsRespectively, the start and stop time of the interval of the first arrival wave of the Lamb wave, and s (t) is the voltage signal detected by the piezoelectric transducer, i.e. the energy of the signal is the start and stop time of the voltage signal in the interval, respectively, te、tsIs calculated. Of course, in this embodiment, the damage index DI may also be calculated according to a ratio of the voltage signal of the difference signal s _ s and the voltage signal of the current baseline signal s _ b, and a preset threshold corresponding to the ratio is set to determine the damage condition of the plate-shaped structure. However, when the damage index DI is calculated by the energy value of the signal, the specific damage condition of the plate-shaped structure, such as the size and depth of a crack, can be intuitively reflected from the graph corresponding to the damage index, so as to prevent or further operate the damage.
In this embodiment, in order to ensure the accuracy of the detection result, the reference database needs to determine the corresponding relationship between the baseline signal and the temperature corresponding to the baseline signal by a sufficient amount. In step S2, during the process of creating the reference database, when the baseline signal is collected, the plate-shaped structure is intact and non-damaged, the energy of the collected baseline signal should meet the specific gaussian distribution condition, and if not, it is necessary to check whether the start-stop time of the first arrival interval of Lamb waves or the arrangement of the piezoelectric transducer array in S1 is appropriate. That is to say, while establishing the reference database, the start and stop time of the first arrival wave interval of Lamb waves and the arrangement of the piezoelectric transducer array are also adjusted, wherein the adjustment of the arrangement of the piezoelectric transducer array includes the adjustment of specific positions, intervals, number and the like of each piezoelectric transducer, and the accuracy of the result when the damage detection is performed on the plate-shaped structure is further ensured.
When damage detection is carried out on an attention area of a plate-shaped structure of a railway vehicle, the attention area needs to be designed in detail according to bench tests, simulation analysis, line operation experience, design requirements and the like, on one hand, the requirement for detecting the attention area is met, on the other hand, the distance between piezoelectric transducers is not too short, the first arrival wave is prevented from being annihilated by system crosstalk, and is not too long, and the first arrival wave is prevented from containing too much line noise.
In step S5, if the damage index of the detection result does not exceed the preset threshold and the energy of the current signal meets the specific gaussian distribution condition of the energy of the baseline signal in the reference database, the current signal and the current temperature can be brought into the reference database, that is, the baseline signal amount in the database is continuously expanded during the detection process, and the larger the baseline signal amount in the reference database is, the more accurate the corresponding relationship between the baseline signal amount and the temperature is, thereby ensuring the accuracy of the detection result.
The calculation of the energy for the baseline signal and the calculation of the energy for the current signal in the above embodiments are both calculated according to the above energy calculation formula.
The specific gaussian distribution condition is within a frequency range of 5% -95% of the gaussian distribution, that is, when the energy of the acquired baseline signal is within the frequency range of 5% -95% of the energy gaussian distribution, the acquired baseline signal is included in the reference database, and if the acquired baseline signal is not within the frequency range of 5% -95% of the energy gaussian distribution, whether the start-stop time of the first arrival interval of the Lamb wave or the array arrangement of the piezoelectric transducers is appropriate or not is checked, so that the start-stop time of the first arrival interval of the Lamb wave and the array arrangement of the piezoelectric transducers are adjusted. If the damage index of the current signal does not exceed the preset threshold and the energy of the current signal is within the frequency range of 5% -95% of Gaussian distribution of energy, the current signal and the current temperature are brought into the reference database, if the current signal and the current temperature are not matched, the current signal and the current temperature are not brought into the reference database, so that signals with potential defects, such as the signals with the defects of which the damage degree does not reach the preset threshold, are prevented from being brought into the reference database, and the accuracy of the detection result is prevented from being influenced.
In the above embodiment, in the process of acquiring the baseline signal and the current signal, both the signal is filtered and reconstructed, so as to avoid interference of the noise when the signal is acquired. Taking damage detection on a plate-shaped structure of a train as an example, due to the influence of environmental noises such as vibration impact, electromagnetic interference and the like in the running process of the train, the signals are filtered and reconstructed when being collected, so that the interference of noise can be avoided, the first arriving wave can be obviously seen, the detection result can be conveniently analyzed, and the accuracy of the detection result is improved.
In this embodiment, the signal energy is concentrated in a narrow frequency band by band-pass filtering, such as 250 (specific excitation frequency) ± 50kHz to filter other frequency band noise, so as to ensure the accuracy of the detection result.
In addition, for the reconstructed signal, the start-stop time of the interval of the first arrival wave needs to be determined first, in this embodiment, the start-stop time of the interval of the first arrival wave is determined by using a wavelet transform method, but may also be determined by using other methods, such as a hilbert transform method.
In this embodiment, the current baseline signal is determined by fitting the relationship between each baseline data in the reference database and the temperature by using the least square method and combining the current temperature collected in S3. That is, the inside of the system may adopt a least square method to fit the corresponding relationship between each baseline signal and the temperature in the reference database, and combine the acquired current temperature to determine the baseline signal corresponding to the current temperature. During the detection process, the amount of the baseline data in the reference database changes, the corresponding relationship between each baseline signal and the temperature in the reference database also changes correspondingly, and when the data amount reaches a certain amount, the relationship between the baseline signal and the temperature is relatively stable.
Specifically, the damage detection flow of the plate-shaped structure according to the embodiment of the present invention is shown in fig. 2, where FAW refers to a characteristic value of the first arriving wave of the first lamb wave. After the piezoelectric transducer array is arranged on the plate-shaped structure, two types of signal acquisition are included, one type is to acquire a baseline signal to establish a reference database when the plate-shaped structure is in a complete state, the other type is to acquire a current signal in a detection process, temperature data are acquired while the two types of signals are acquired, and the method for acquiring the signals is the same as that of the method for acquiring the signals, and the method comprises the following steps: and exciting the model structure by using a specific excitation frequency, and filtering and reconstructing the acquired signal to remove the interference of the clutter. The start-stop time of the interval of FAW of the reconstructed signal is determined so as to calculate the energy of the signal.
If a reference database is established, the plate-shaped structure is in an integral state, a baseline signal and temperature are collected at the same time, the energy of the baseline signal is calculated, if the energy of the baseline signal meets the energy-specific Gaussian distribution requirement of the signal in the reference database, the baseline signal and the temperature are brought into the reference database, if the energy of the baseline signal does not meet the energy-specific Gaussian distribution requirement of the signal in the reference database, the starting and ending time of a FAW interval for calculating the energy of the baseline signal is checked, if the design is improper, corresponding adjustment is carried out, if the design of the starting and ending time of the FAW interval has no problem, the arrangement of the piezoelectric transducer array in S1 is checked, if the design is improper, other misoperation and other reasons possibly exist in the collection of the baseline signal, and the baseline signal is discarded.
When the reference database contains enough temperature data, the current signal s _ c and the current temperature are collected in the process of detecting the plate-shaped structure, the corresponding relation between the baseline signal in the reference database and the temperature is fitted through a least square method, the baseline signal corresponding to the current temperature, namely the current baseline signal s _ b, is determined, and the difference signal s _ s is calculated to be s _ b-s _ c. And calculating the energy E _ s of the difference signal s _ s and the energy E _ b of the current baseline signal, wherein the damage index DI is E _ s/E _ b, if DI exceeds a preset threshold, the plate-shaped structure is damaged, and if DI does not exceed the preset threshold and the energy E _ c of the current signal loads a specific Gaussian distribution condition of the signal energy in the reference database, the current signal and the current temperature are contained in the reference database so as to expand the temperature data in the reference database.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that it is obvious to those skilled in the art that various modifications and improvements can be made without departing from the principle of the present invention, and these modifications and improvements should also be considered as the protection scope of the present invention.
Claims (6)
1. A damage detection method of a plate-shaped structure is characterized by comprising the following steps:
s1: an array of piezoelectric transducers arranged in a plate-shaped structure;
s2: establishing a reference database:
(1) the piezoelectric transducer excites the undamaged plate-shaped structure at a specific excitation frequency to generate lamb waves;
(2) collecting a plurality of groups of baseline signals and corresponding temperatures, wherein each baseline signal is a characteristic value of a first arrival wave of the lamb waves;
(3) storing each set of the baseline signals and the temperatures corresponding thereto in the reference database;
s3: collecting the current signal and the current temperature of the plate-shaped structure to be detected by the same method as the method (1) and the method (2) in the step S2;
s4: calculating a difference signal, wherein the difference signal is a current baseline signal-a current signal, and the current baseline signal is a baseline signal corresponding to the current temperature in the reference database;
s5: calculating a damage index according to the difference signal and the current baseline signal, judging that the plate-shaped structure to be detected is damaged if the damage index exceeds a preset threshold value, and judging that the plate-shaped structure to be detected is not damaged if the damage index does not exceed the preset threshold value;
the impairment index is the energy of the difference signal/the energy of the current baseline signal, where the energy of the signal is calculated according to the following formula:
wherein t ise、tsRespectively, the start-stop time of the interval of the first arrival wave of the lamb wave, and s (t) is a voltage signal detected by the piezoelectric transducer;
at S2, if the energy of the baseline signal meets a specific gaussian distribution condition, the energy of the baseline signal is included in the reference database, and if the energy of the baseline signal does not meet the specific gaussian distribution condition, the start-stop time of the interval of the first arrival wave of the lamb wave or the arrangement of the piezoelectric transducer array at S1 is detected;
in S5, if the damage index does not exceed the preset threshold and the energy of the current signal meets a specific gaussian distribution condition of the energy of the baseline signal in the reference database, the current signal and the current temperature are included in the reference database.
2. The method according to claim 1, wherein the specific gaussian distribution condition is a gaussian distribution in a frequency range of 5% to 95%.
3. The method of claim 1, wherein the filtering and reconstructing of the signal is performed during both the acquisition of the baseline signal and the acquisition of the current signal.
4. The method of claim 3, wherein the filtering is performed in a band-pass manner.
5. A method of impairment detection by a wavelet transform in which the start-stop time of the interval of the first arrival of the reconstructed signal is determined.
6. The method of claim 1, wherein the current baseline signal is determined by fitting a least squares fit of the baseline signals to the temperature in the reference database in conjunction with the current temperature in S3.
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| EP3896442A4 (en) * | 2019-01-15 | 2022-01-26 | Yamaha Hatsudoki Kabushiki Kaisha | Internal state detection device and vehicle |
| CN110031552B (en) * | 2019-05-27 | 2021-10-22 | 嘉兴博传科技有限公司 | Structural health monitoring damage characteristic value calculation method |
| CN111208206B (en) * | 2020-02-20 | 2022-11-25 | 北京博感科技有限公司 | Composite material ultrasonic guided wave structure health monitoring method in temperature change environment |
| CN112033710B (en) * | 2020-09-15 | 2022-04-01 | 中车青岛四方机车车辆股份有限公司 | Urban rail vehicle framework damage degree detection method based on neural network |
| CN113533513A (en) * | 2021-06-29 | 2021-10-22 | 北京交通大学 | Real-time monitoring method and monitoring device for steel rail damage |
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