CN110687196A - System and method for detecting lamb wave action effect of plate-shaped structure reinforcing rib - Google Patents
System and method for detecting lamb wave action effect of plate-shaped structure reinforcing rib Download PDFInfo
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- CN110687196A CN110687196A CN201910789837.1A CN201910789837A CN110687196A CN 110687196 A CN110687196 A CN 110687196A CN 201910789837 A CN201910789837 A CN 201910789837A CN 110687196 A CN110687196 A CN 110687196A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/04—Analysing solids
- G01N29/041—Analysing solids on the surface of the material, e.g. using Lamb, Rayleigh or shear waves
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/44—Processing the detected response signal, e.g. electronic circuits specially adapted therefor
- G01N29/4409—Processing the detected response signal, e.g. electronic circuits specially adapted therefor by comparison
Abstract
The invention relates to a system for detecting the effect of a plate-shaped structure reinforcing rib on lamb waves, which is characterized in that: the left sides of the stiffened plates and the flat plates are provided with signal excitation sensors, the right sides of the stiffened plates and the flat plates are provided with signal receiving sensors, the signal generators are connected with the signal excitation sensors respectively connected to the stiffened plates and the flat plates, the signal receiving sensors of the stiffened plates and the flat plates are connected to the acoustic emission instrument, and the acoustic emission instrument is connected to the computer. The invention also relates to a method for detecting the lamb wave action effect of the plate-shaped structure reinforcing rib, which comprises the following steps: 1) building a system; 2) setting parameters; 3) signal acquisition; 4) and (6) signal processing. The method has scientific and reasonable design and definite purpose, eliminates the interference of other factors, reduces the difficulty of signal detection, saves the signal processing time, is beneficial to acquiring real and correct signal characteristics, and has important significance on the positioning of a damage source and the pattern recognition.
Description
Technical Field
The invention belongs to the field of precision instruments, relates to the research of lamb wave action effect, and particularly relates to a system and a method for detecting the lamb wave action effect of a plate-shaped structure reinforcing rib.
Background
The plate-shaped structure is widely applied to the fields of industry, medical treatment, aerospace, military and the like, and in order to ensure that the structure has enough mechanical strength and some accessories are installed, and simultaneously, the mass is not too large, periodic reinforcing ribs and installation frames are usually arranged on the surface of the plate-shaped structure. When a plate-like structure is acoustically tested for state of health (e.g., fatigue, collision, leakage, etc.), acoustic signals propagate in the structure in the form of lamb waves.
Because lamb waves can generate phenomena of frequency dispersion, reflection, transmission, mode conversion and the like when being transmitted in the stiffened plate, the amplitude and the energy distribution of the lamb waves can be changed violently, and the difficulty of signal detection is increased. However, studies have shown that different numbers of ribs have different effects on the signal. Reusser et al have studied the propagation law of lamb waves in stiffened plates with two aspect ratios, and lamb waves with different frequencies have different transmission energies and tend to oscillate when passing through the stiffened ribs. The phenomenon is more obvious in the stiffened plate with a high aspect ratio, and the accuracy of leakage positioning is improved by selecting A0 modal lamb waves in a specific frequency band. The simplified model is used to draw the conclusion that the signal attenuation is serious when the frequency of the S0 modal lamb wave is near the resonance frequency of the stiffened plate. However, the research mainly aims at the influence rule of a single reinforcing rib on lamb wave signals, and the collision signals are not researched in a related mode. The reflection characteristics of the rib with respect to lamb waves at different incident angles were studied by Ghandourah et al, and the relationship between the reflection coefficient of the plate end with respect to lamb waves of different modes, the incident angle, and the frequency was studied by Santhanam et al. Further, there have been studies on the characteristics of lamb wave signals in a ribbed aluminum sheet with cracks, the interaction between lamb waves and different types of notches, and the mode conversion phenomenon of lamb waves when they pass through notches.
Therefore, proper frequency detection is carried out on lamb waves in the flat plate with the reinforcing rib structure, the action effect of the reinforcing rib is compensated for the original signal, and the research difficulty can be reduced. For stiffened plate structures of different sizes and different numbers, a unified method is needed to quantify the influence of the stiffeners on lamb waves in the plate. Currently, there are some metrics, such as energy attenuation metrics using broadband lamb waves and based on two-dimensional fourier transforms. The broadband lamb wave is adopted as an excitation signal to be loaded on one side of the reinforcing rib, and the signals are sampled at two ends of the reinforcing rib at certain space intervals. And the energy attenuation degree of the lamb waves when passing through the reinforcing rib structure is quantified by calculating the energy ratio of the lamb waves before and after passing through the reinforcing rib. However, this method has the disadvantage of high requirements for detection equipment, and usually, some frequency bands have weak signal energy and inaccurate quantization results. Some scholars apply a sinusoidal signal of a single frequency on one side of the bar using a transducer and receive it on the other side using a receiver instrument. And after the frequency of the sinusoidal signal is changed, repeating the steps, and measuring the influence of the reinforcing rib on lamb waves by the ratio of the energy of the post-rib signal with the corresponding frequency to the energy of the pre-rib signal. This method is very labor intensive and time consuming, especially when the frequency range of interest is large. In addition, in the propagation process of lamb wave signals, phenomena such as energy attenuation, frequency dispersion and mode conversion occur along with the increase of the propagation distance, and the methods do not consider the influence of the propagation distance on the signals.
Through a search for a patent publication, no patent publication that is the same as the present patent application is found.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, and provides a method based on an energy ratio for solving the problem of how to measure the action effect of a reinforcing rib on lamb waves in a plate-shaped structure. The influence of the reinforcing ribs is quantized, so that the characteristic rules of damage signals such as collision and leakage become clearer, the difficulty of signal detection is reduced, the signal processing time is shortened, the real and correct signal characteristics can be acquired, and the method has important significance on the positioning and the mode recognition of a damage source.
The technical problem to be solved by the invention is realized by the following technical scheme:
the utility model provides a detecting system of platelike structure strengthening rib to lamb wave effect which characterized in that: the system comprises a signal generator, an acoustic emission instrument, a computer, a stiffened plate, a flat plate and a plurality of sensors, wherein signal excitation sensors are arranged on the left sides of the stiffened plate and the flat plate, signal receiving sensors are arranged on the right sides of the stiffened plate and the flat plate, the signal generator is connected with the signal excitation sensors which are respectively connected to the stiffened plate and the flat plate, the signal receiving sensors of the stiffened plate and the flat plate are both connected to the acoustic emission instrument, and the acoustic emission instrument is connected to the computer.
And the signal excitation sensors and the signal receiving sensors on the stiffened plate and the flat plate are symmetrically distributed.
Moreover, the signal excitation sensor on the stiffened plate corresponds to the signal excitation sensor on the flat plate in position; and the signal receiving sensors on the stiffened plates correspond to the signal receiving sensors on the flat plate in position.
A method for detecting the lamb wave action effect of a plate-shaped structure reinforcing rib is characterized by comprising the following steps: the detection method comprises the following steps:
1) system construction: pasting a signal excitation sensor to the left side of the stiffened plate through a high-vacuum silicone grease coupling agent, and pasting the signal excitation sensor at the same position on the flat plate corresponding to the stiffened plate; pasting a signal receiving sensor to the right side of the stiffened plate through a high-vacuum silicone grease coupling agent, and pasting the signal receiving sensor at the same position on the flat plate corresponding to the stiffened plate; connecting a signal transmitter, a signal excitation sensor, a signal receiving sensor, an acoustic generator and a computer;
2) setting parameters: setting the voltage of the signal generator to be 2V, inputting an expression of the broadband sinusoidal superposed signal into the signal generator, and enabling the signal generator to transmit an excitation signal to the signal excitation sensor; setting the threshold value of the acoustic emission instrument to be 40dB, setting the sampling rate to be 3MHz, setting the maximum frequency of the concerned signal to be 500kHz, receiving the signal through a signal receiving sensor and transmitting the received signal to a computer under the control of the acoustic emission instrument;
3) signal acquisition: the computer respectively carries out Fourier transform processing on the received signals in the stiffened plate and the flat plate to obtain frequency spectrum information of the two groups of signals;
4) signal processing: and (3) performing ratio operation on the obtained frequency spectrum energy by adopting the signal frequency spectrum energy calculated by the computer, and taking the result as an energy factor for measuring the action effect of the reinforcing rib on the lamb wave excitation signal.
In addition, the broadband sine superposition signal in the step 2) is superposition of sine waves with the duration of 20 mus and the frequency gradually increased from 50kHz to 500kHz at intervals of 1 kHz; and the expression of the excitation signal emitted by the signal generator is as follows:
wherein the content of the first and second substances,
y (t) is the excitation signal,
t is the time of day and t is,
f is the frequency of the signal to be detected,
a is the amplitude value of the signal,
In step 3), the mathematical expression used in the fourier transform is:
wherein:
f (t) is the signal time domain waveform,
w (ω) is the signal spectrum.
In step 4), the calculation expression of the signal spectrum energy is:
E(f)＝|W(ω)|2
wherein:
e (f) is the signal energy,
w (ω) is the signal spectrum,
the expression for the energy factor is:
wherein:
r (f) is an energy factor,
ES(f) in the stiffened plate, lamb waves are received by the signal receiving sensor after passing through the reinforcing rib,
EP(f) in the flat plate, lamb waves are received by the signal receiving sensor after passing through the flat plate.
The invention has the advantages and beneficial effects that:
1. the invention builds a detection system for measuring the action effect of the reinforcing ribs, and further explores the action effect of the reinforcing ribs in the plate-shaped structure on the lamb wave on the basis of the lamb wave theory.
2. The invention adopts the stiffened plate and the flat plate to carry out contrast experiments, and can eliminate the influence of phenomena of lamb wave energy attenuation, frequency dispersion, energy conversion and the like caused by the propagation distance.
3. The invention provides a method for measuring the effect of a strengthening rib on lamb waves in a plate-shaped structure by taking the energy ratio of corresponding frequencies of signals in two groups of test pieces as an energy factor, which has the advantages of clear purpose, elimination of interference of other factors and reasonable principle.
4. The method has scientific and reasonable design and definite purpose, eliminates the interference of other factors, reduces the difficulty of signal detection, saves the signal processing time, is beneficial to acquiring real and correct signal characteristics, and has important significance on the positioning of a damage source and the pattern recognition.
Drawings
FIG. 1 is an overall flow chart of the technical solution of the present invention;
FIG. 2 is a schematic diagram of the connection of the detection system of the present invention;
fig. 3a) is a time domain waveform diagram of the excitation signal, and fig. 3b) is a frequency domain waveform diagram of the excitation signal.
Detailed Description
The present invention is further illustrated by the following specific examples, which are intended to be illustrative, not limiting and are not intended to limit the scope of the invention.
A detection system for the lamb wave action effect of a plate-shaped structure reinforcing rib is characterized in that: the system comprises a signal generator, an acoustic emission instrument, a computer, a stiffened plate, a flat plate and a plurality of sensors, wherein signal excitation sensors are arranged on the left sides of the stiffened plate and the flat plate, signal receiving sensors are arranged on the right sides of the stiffened plate and the flat plate, the signal generator is connected with the signal excitation sensors which are respectively connected to the stiffened plate and the flat plate, the signal receiving sensors of the stiffened plate and the flat plate are both connected to the acoustic emission instrument, and the acoustic emission instrument is connected to the computer.
The signal excitation sensors and the signal receiving sensors on the stiffened plate and the flat plate are symmetrically distributed.
The signal excitation sensor on the stiffened plate corresponds to the signal excitation sensor on the flat plate in position; the signal receiving sensors on the stiffened plates correspond to the signal receiving sensors on the flat plates in position.
A method for detecting the effect of a plate-shaped structure reinforcing rib on lamb waves is innovative and characterized in that: the detection method comprises the following steps:
1) system construction: pasting a signal excitation sensor to the left side of the stiffened plate through a high-vacuum silicone grease coupling agent, and pasting the signal excitation sensor at the same position on the flat plate corresponding to the stiffened plate; pasting a signal receiving sensor to the right side of the stiffened plate through a high-vacuum silicone grease coupling agent, and pasting the signal receiving sensor at the same position on the flat plate corresponding to the stiffened plate; connecting a signal transmitter, a signal excitation sensor, a signal receiving sensor, an acoustic generator and a computer;
2) setting parameters: setting the voltage of the signal generator to be 2V, inputting an expression of the broadband sinusoidal superposed signal into the signal generator, and enabling the signal generator to transmit an excitation signal to the signal excitation sensor; setting the threshold value of the acoustic emission instrument to be 40dB, setting the sampling rate to be 3MHz, setting the maximum frequency of the concerned signal to be 500kHz, receiving the signal through a signal receiving sensor and transmitting the received signal to a computer under the control of the acoustic emission instrument;
the broadband sine superposition signal is superposition of sine waves with the duration of 20 mus and the frequency gradually increased from 50kHz to 500kHz at intervals of 1 kHz; and the expression of the excitation signal emitted by the signal generator is as follows:
wherein the content of the first and second substances,
y (t) is the excitation signal,
t is the time of day and t is,
f is the frequency of the signal to be detected,
a is the amplitude value of the signal,
3) Signal acquisition: the computer respectively carries out Fourier transform processing on the received signals in the stiffened plate and the flat plate to obtain frequency spectrum information of the two groups of signals;
the mathematical expression adopted by the Fourier transform is as follows:
wherein:
f (t) is the signal time domain waveform,
w (ω) is the signal spectrum.
4) Signal processing: performing ratio operation on the obtained frequency spectrum energy by adopting the signal frequency spectrum energy calculated by the computer, and taking the result as an energy factor for measuring the action effect of the reinforcing rib on the lamb wave excitation signal;
the computational expression of the signal spectral energy is:
E(f)＝|W(ω)|2
wherein:
e (f) is the signal energy,
w (ω) is the signal spectrum,
the expression for the energy factor is:
wherein:
r (f) is an energy factor,
ES(f) in the stiffened plate, lamb waves are received by the signal receiving sensor after passing through the reinforcing rib,
EP(f) in the flat plate, lamb waves are received by the signal receiving sensor after passing through the flat plate.
Although the embodiments of the present invention and the accompanying drawings are disclosed for illustrative purposes, those skilled in the art will appreciate that: various substitutions, changes and modifications are possible without departing from the spirit and scope of the invention and the appended claims, and therefore the scope of the invention is not limited to the disclosure of the embodiments and the accompanying drawings.
Claims (7)
1. The utility model provides a detecting system of platelike structure strengthening rib to lamb wave effect which characterized in that: the system comprises a signal generator, an acoustic emission instrument, a computer, a stiffened plate, a flat plate and a plurality of sensors, wherein signal excitation sensors are arranged on the left sides of the stiffened plate and the flat plate, signal receiving sensors are arranged on the right sides of the stiffened plate and the flat plate, the signal generator is connected with the signal excitation sensors which are respectively connected to the stiffened plate and the flat plate, the signal receiving sensors of the stiffened plate and the flat plate are both connected to the acoustic emission instrument, and the acoustic emission instrument is connected to the computer.
2. The system for detecting the effect of a plate-like structural reinforcing bar on lamb waves according to claim 1, wherein: and the signal excitation sensors and the signal receiving sensors on the stiffened plates and the flat plate are symmetrically distributed.
3. The system for detecting the effect of a plate-like structural reinforcing bar on lamb waves according to claim 1, wherein: the signal excitation sensor on the stiffened plate corresponds to the signal excitation sensor on the flat plate in position; and the signal receiving sensors on the stiffened plates correspond to the signal receiving sensors on the flat plate in position.
4. The method for detecting the effect of a plate-like structure reinforcing rib on lamb waves according to claim 1, wherein the method comprises the following steps: the detection method comprises the following steps:
1) system construction: pasting a signal excitation sensor to the left side of the stiffened plate through a high-vacuum silicone grease coupling agent, and pasting the signal excitation sensor at the same position on the flat plate corresponding to the stiffened plate; pasting a signal receiving sensor to the right side of the stiffened plate through a high-vacuum silicone grease coupling agent, and pasting the signal receiving sensor at the same position on the flat plate corresponding to the stiffened plate; connecting a signal transmitter, a signal excitation sensor, a signal receiving sensor, an acoustic generator and a computer;
2) setting parameters: setting the voltage of the signal generator to be 2V, inputting an expression of the broadband sinusoidal superposed signal into the signal generator, and enabling the signal generator to transmit an excitation signal to the signal excitation sensor; setting the threshold value of the acoustic emission instrument to be 40dB, setting the sampling rate to be 3MHz, setting the maximum frequency of the concerned signal to be 500kHz, receiving the signal through a signal receiving sensor and transmitting the received signal to a computer under the control of the acoustic emission instrument;
3) signal acquisition: the computer respectively carries out Fourier transform processing on the received signals in the stiffened plate and the flat plate to obtain frequency spectrum information of the two groups of signals;
4) signal processing: and (3) performing ratio operation on the obtained frequency spectrum energy by adopting the signal frequency spectrum energy calculated by the computer, and taking the result as an energy factor for measuring the action effect of the reinforcing rib on the lamb wave excitation signal.
5. The method for detecting the lamb wave action effect of a plate-shaped structural reinforcing rib according to claim 4, wherein the method comprises the following steps: the broadband sine superposition signal in the step 2) is superposition of sine waves with the duration of 20 mus and the frequency gradually increased from 50kHz to 500kHz at intervals of 1 kHz; and the expression of the excitation signal emitted by the signal generator is as follows:
wherein the content of the first and second substances,
y (t) is the excitation signal,
t is the time of day and t is,
f is the frequency of the signal to be detected,
a is the amplitude value of the signal,
t020 μ s.
6. The method for detecting the lamb wave action effect of a plate-shaped structural reinforcing rib according to claim 4, wherein the method comprises the following steps: in the step 3), the mathematical expression adopted by the Fourier transform is as follows:
wherein:
f (t) is the signal time domain waveform,
w (ω) is the signal spectrum.
7. The method for detecting the lamb wave action effect of a plate-shaped structural reinforcing rib according to claim 4, wherein the method comprises the following steps: in the step 4), the calculation expression of the signal spectrum energy is as follows:
E(f)＝|W(ω)|2
wherein:
e (f) is the signal energy,
w (ω) is the signal spectrum,
the expression for the energy factor is:
wherein:
r (f) is an energy factor,
ES(f) in the stiffened plate, lamb waves are received by the signal receiving sensor after passing through the reinforcing rib,
EP(f) in the flat plate, lamb waves are received by the signal receiving sensor after passing through the flat plate。
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| CN101539541A (en) * | 2009-04-09 | 2009-09-23 | 上海交通大学 | Detection method of thick beam structure damage based on guide wave |
| CN102128881A (en) * | 2010-12-22 | 2011-07-20 | 南京邮电大学 | Method for monitoring Lamb wave engineering structural damage by utilizing signal decomposition |
| CN103983691A (en) * | 2014-05-15 | 2014-08-13 | 西北工业大学 | Method for measuring material loss factor |
| CN104407054A (en) * | 2014-12-17 | 2015-03-11 | 厦门大学 | Ultrasonic micro-damage location detection method and device based on collinear aliasing of Lamb waves |
| CN109737899A (en) * | 2019-01-25 | 2019-05-10 | 北京科技大学 | A kind of metal material crack-type defect depth measurement device and method |
| CN109946381A (en) * | 2019-01-08 | 2019-06-28 | 南京质联智能科技有限公司 | A kind of detection method and device |
-
2019
- 2019-08-26 CN CN201910789837.1A patent/CN110687196A/en active Pending
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101539541A (en) * | 2009-04-09 | 2009-09-23 | 上海交通大学 | Detection method of thick beam structure damage based on guide wave |
| CN102128881A (en) * | 2010-12-22 | 2011-07-20 | 南京邮电大学 | Method for monitoring Lamb wave engineering structural damage by utilizing signal decomposition |
| CN103983691A (en) * | 2014-05-15 | 2014-08-13 | 西北工业大学 | Method for measuring material loss factor |
| CN104407054A (en) * | 2014-12-17 | 2015-03-11 | 厦门大学 | Ultrasonic micro-damage location detection method and device based on collinear aliasing of Lamb waves |
| CN109946381A (en) * | 2019-01-08 | 2019-06-28 | 南京质联智能科技有限公司 | A kind of detection method and device |
| CN109737899A (en) * | 2019-01-25 | 2019-05-10 | 北京科技大学 | A kind of metal material crack-type defect depth measurement device and method |
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Application publication date: 20200114 |