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Acoustic sensor. RU patent 2498525.

Acoustic sensor. RU patent 2498525.
IPC classes for russian patent Acoustic sensor. RU patent 2498525. (RU 2498525):

H04R17/00 - Piezo-electric transducers; Electrostrictive transducers (piezo-electric or electrostrictive elements in general H01L0041000000; details of piezo-electric or electrostrictive motors, generators or positioners H02N0002000000)
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FIELD: measurement equipment.

SUBSTANCE: acoustic sensor includes a piezoelectric substrate, a common electrode located on one side of the piezoelectric substrate, a set of the first electrode structures located on opposite side of the piezoelectric substrate relative to the common electrode; with that, each first electrode structure is located radially relative to a conditional central point and includes a set of electrode elements located in circumferential directions. With that, the above first electrode structures are located with possibility of choosing one or more groups of electrode elements from the specified first electrode structure so that the above first electrode structure can be tuned to the pre-determined frequency range, and each of the above first electrode structures is arranged pre-determined radial direction relative to the above conditional central point so that each of the above first electrode structures can be tuned to signals having the corresponding directivity. In addition, the sensor is equipped with the second and the third electrode structures and can operate in the frequency range of 10 kHz to 20 MHz using directional Lamb waves.

EFFECT: improving accuracy of determination of a place of failure.

10 cl, 6 dwg

 

The technical field to which the invention relates

The present invention relates to the acoustic sensor.

The level of technology

During operation of any design can be subjected to damage, which can lead to the possibility of structural failure. In many situations, it is important to monitor damage to repair the damage or replace the design before there is any performance decrease. Many similar structures are created and used in aviation, aerospace, shipbuilding or automotive industries.

When the design is damaged, the damaged area emits acoustic waves (acoustic emission (AE)), which are distributed through the material of construction. For the detection of acoustic emission that occurs when the design corruption occurs, place the acoustic monitoring system damage, which are systems of detection and monitoring using acoustic emission method. Such systems are used in systems of non-destructive testing (NDT), for example, systems to monitor the condition of a design (SHM). In certain places of the design for the purpose of detection of acoustic emission sensors are put these systems. Registered passing time (ToF) of the acoustic wave to each sensor. In this case, you can determine the source of acoustic emission, using triangulation time of passage (ToF) of the acoustic wave on the basis of the known locations of the host sensor. In such methods for the detection of acoustic emission are used, the so-called passive acoustic monitoring system. Another type of acoustic monitoring systems called active systems. In such active sensor systems, mounted on the design, generates an acoustic signal request and any resulting reflected signal is analyzed to identify and classify defects or damage.

In mechanical constructions such as the compartments of aircraft or components, which are mainly made of sheet material, acoustic waves form a separate types of plate waves, known as the lamb waves. In passive systems of acoustic waves are emitted damage when it occurs, while in active systems acoustic waves are emitted or generated by the sensor. Lamb waves has many different types of oscillations or shows that are able to keep their shape and spread steadily or unsteadily, depending on their state of dispersion. Changes in mechanical shape design, for example, border areas between one material and other material, or change the thickness of the section of this material may influence the signal lamb waves. For example, the materials can affect the signal lamb waves, reduce its amplitude or change his fashion. On a different wave modes such design changes can have a different impact. For example, with this modification, the path of the wave weakening of one fashion lamb waves can differ from weakening the other fashion. Indeed, the weakening of some modes can be so large that when the weakened fashion reaches the sensor location, it has an amplitude that the sensor cannot detect. Lamb waves propagate in all directions, but they are sensitive to the aimed stiffness and thickness of the structure, in which they apply. Thus, the distribution of the lamb wave may be easier in a particular direction of this design. Stiffness and thickness are determined by the peculiarities of the structure.

Each fashion lamb waves usually has a characteristic frequency and wavelength range. However, all the mods may not reach the point where the sensor is passive or active monitoring system. Thus, the problem consists in the coordination of frequency sensors, generating or receiving lamb waves, located in the place, with a range of frequency of the wave, which should probably be found in the specified location.

Disclosure of the invention

In one of the options for the implementation of the invention features acoustic sensor, containing:

the common electrode;

piezoelectric layer with General electrode located on the same side;

the first set of electrode structures, located on the opposite side of the piezoelectric layer relative to the General electrode, with each the first electrode structure radially located on the conditional Central point and contains a set situated in circles electrode elements, with the first electrode structure is arranged with a possibility to select one or more groups of electrode elements of the given first electrode structures in order to configure the specified set the first electrode structure for a pre-defined frequency range.

Each of the first electrode structures can be placed in a pre-defined radial direction to set up the structure of the signals, which have the appropriate orientation. The first electrode structure placed with the possibility to select one or more groups of electrode elements of the given first electrode structure for setting first given electrode structure for a predefined frequency range and to determine the position of groups relative to the nominal center. Electrode elements of a given first electrode structures can be made of the same size along the circles. Electrode elements of a given first electrode structure can be performed along with the size of circles is proportional to the distance from the conventional Central point to a given electrode element.

Additionally, the sensor can contain located in circles second structure of radially placed electrode elements. Additionally, the sensor may contain third structure, centred relatively conditional Central point. The third structure can contain one or more concentric elements spatially separated in the radial direction. The sensor can be installed so that it operates in the frequency range from 10 kHz to 20 MHz. Each electrode element can be connected by wires to a processor to signal received by the sensor.

Brief description of drawings

Next invention will be described only by example with reference to the accompanying drawings.

Figure 1 side view of the plane on the ground.

Figure 2 - schematic illustration of acoustic monitoring systems in the plane, submitted on figure 1.

Figure 3 - a plan view of the sensor used in acoustic monitoring system presented in figure 2.

Figure 4 - the kind in section sensor used in acoustic monitoring system presented in figure 2.

Figure 5 and 6 - type in the plan sensors placed under other options.

A detailed description of the preferred embodiments of the invention

1 is a plane 101 containing the fuselage 102 and wings 103, rendered valid by the streamlined shape, and fairings 104. The plane 101, in addition, contains a passive acoustic system 105 monitoring posted to detection of acoustic emission caused by damage to the aircraft design 101, through a set of sensors, representing an acoustic sensor (not shown in figure 1), installed in aircraft design 101. The sensors are installed to detect the spread of the lamb wave emitted when damage to the design of the aircraft, to identify the areas of aircraft design, which require testing or repair. Figure 2 shows a fuselage 102, which gauges, namely, sensors 201, 202, 203, 204 installed in certain locations relative to the pivot point 205 and form a grid. Each sensor 201, 202 203, 204 connected with the system 105 acoustic monitoring.

If corruption occurs, for example, on the section 206 of the fuselage, acoustic emission comes from the plot 206 and distributed under the fuselage to the sensors 201, 202, 203, 204. On each of the sensors 201, 202, 203, 204 acoustic emission is detected in different times, as there is a difference in the length of the sound wave to each sensor and the possible difference of the group velocities. In the example on figure 2, acoustic emission is detected by the first sensor And 201, then the sensor In 202 sensor With 203 and sensor sensor D 204. Speaker system 105 monitoring installed for registration series times of passage (ToF) of the acoustic waves in a series of relative time measurements, i.e. as a temporal measurements relative to the first detection of acoustic emission any of the sensors 201, 202, 203, 204. In other words, the relative time for the sensor And is zero and relative time for other sensors, B, C, D is a time difference between the intake of acoustic emission sensor and its subsequent admission of other sensors, B, C, D. Then the difference of values ToF to determine the location of the source of acoustic emission.

As noted above, changes in the design of different can affect different fashion lamb waves. For example, for a given change in the design of the weakening of one fashion wave on wave way may differ from weakening the other fashion. The impact of this design on acoustic emission can be calculated by using the known experimental or empirical data to weaken and theoretical data on the dispersion of relevant materials provided in the form of the dispersion functions or curves. Such dispersion curves detail the available wave modes and their speed as well as the length of the wave (sensitivity), and are used to determine the wave modes that must be detected at this point. In this embodiment, the dispersion curves are used to match the characteristics of detecting the frequency of each sensor 201, 202, 203, 204. In other words, the dispersion curves are used to determine which individual wave modes have the largest amplitude in these areas, so that on these sites you can adjust the sensors 201, 202, 203, 204 correct frequency that can detect these specific wave modes. The dispersion curves also define the group and phase velocity of each fashion, along with a measure of the sensitivity of the lamb waves to the size of the damage. The dispersion curves may be constructed analytically or experimentally.

In figure 3 you can see that each sensor 201 is essentially in the plan contains a set of sixteen first electrode structures 301 placed around the point of the nominal center of the probe. Each first electrode structure 301 evenly radially located around of a point 302 of the nominal centre and contains a set around the circumference of the electrode elements having the same radial size. In other words, each of the first electrode structures is a strip of electrode elements, located at equal intervals. In this embodiment, the sensor 201, in addition, contains an additional set of sixteen second electrode structures 303, located uniformly radially with respect to the point 302 nominal center, and placed between the relevant first electrode structures 301. Each of the second electrode structures 303 contains a set of placed around the circumference of the second electrode elements, radial size of which is directly proportional to the radial distance of the electrode element from the point of nominal center of the probe. In this embodiment, each of the first and second structures 301, 303 includes thirty-six elements. Each of the first and second electrode structures ensures directional detection of acoustic emission. Thus, the required signals only from two sensors for triangulation location 206 source of acoustic emission.

Figure 4 shows a cross-section of the sensor 201 from a Central point, 302 twelve of the electrode elements of one of the first electrode structures 301. Electrode elements 401 first electrode structure 301 placed on any flat surface of the piezoelectric substrate in the form of plates 402 of - lead (DTN). The common electrode 403 is located on the opposite surface of the plate 402 relative to the surface, where are situated the first and second sets of electrode structures 301, 303. All electrodes 301, 303 403 attached wires to the speakers, 105 monitoring, which performs the analysis of the received signals. When the sensor 201 fixed on the surface, mechanical waves on the surface activate plate of - lead 402. These excitation proportionally converted to electric potential in the plate 402, which is then detected by acoustic system 105 monitoring through electrode structures 301, 303 and General electrode 403. Electric potential, discovered each electrode element 401, depends on the radial width of the electrode item 401, the thickness of the plate of - lead 402, as well as on the amplitude and frequency of the acoustic emission in the place of the electrode item 401.

As noted above, the lamb waves contains a set of wave modes, each of which has a characteristic frequency or wavelength range and speed of propagation. Placement of the matrix elements of the 401 in the electrode structure 301 provides the ability to selectively configure the structure of this wave length. In other words, from electrode structure 301 select the corresponding matrix elements of 401 to provide narrowband sensor with working frequency and wavelength corresponding to the characteristics of the wave of fashion, which is to be discovered, so there are fewer unwanted wave modes. For example, as shown in figure 4, the selection of the first and second electrode items on the left, according to figure 4, will be configured electrode structure 301 for detection of a given wavelength XI, which is determined by the following equation:

1=n.λX,

For example, consider two fashion X and Y lamb waves with wavelengths of 3 mm 42 mm, respectively. To delete a fashion Y, choose the distance between the two electrode elements 1=21 mm, which is equal to the length of a wave of fashion X, multiplied by 7, and is equal to half of length of a wave of fashion Y. In other words, n=7, m=1 and h=2. If he had chosen distance between the two electrode elements 1=63 mm, would have been the same result if not to take into account the weakening of fashion lamb waves. In the following example, if we consider the two fashions X and Y with the relevant wavelengths 4 mm and 22.5 mm, then remove the fashion Y the distance between two (or more) electrode elements would be 1=12 mm, i.e. λX multiplied by 3 and would be approximately equal to?. λY. In other words, n=3, m=1 and h=1,875. Thus, it will be detected only X fashion, and fashion Y will mainly be excluded, however, not completely, since h is not equal to 2. Alternatively, for the detection of fashion Y and exceptions fashion X sensor set up so that the length of the electrode item was 1=22.5 mm, equal to 15·½λY (n integer) and 1·λY (m=2 and h=2). In other words, the physical space occupied by a combination of elements of the first or second electrode structures, should be at or near the wavelength of 1. Likewise, the choice of electrode elements 401 the first to the third or the first to ninth on the left will lead to the configuration of the electrode structure for receiving wavelength λ2 and λ3, as shown in figure 4.

Can be chosen by a separate group of elements for the detection wavelength corresponding to the distance between the centers of each of the selected group. For example, the choice of first, second and third electrode elements left for one group and the fifth, sixth and seventh electrode elements left for the second group would electrode structure, tuned to the wavelength λ4. Wavelength λ4 corresponds to the physical distance between the centers of two selected groups of electrode elements. Thus, using the corresponding dispersion curve for the material on which the sensor is fixed 201, can help determine the appropriate fashion for a given point of fastening sensor and, accordingly, configure sensor 201. Details on the definition of the dispersion curves for a composite material are described in the paper "Design of optimal configuration for generating JSC Lamb mode in a composite plate using piezoceramic transducers" authors Sebastien Grondel, Christophe Paget, Christophe Delebarre and Jamal Assaad, in the Journal of the Acoustical Society of America, 112(1), July 2002. In this embodiment, a sensor adjustments performed by means of an acoustic system 105 monitoring with appropriate selection and processing of signals from electrode elements 401 sensor 201.

As will be appreciated by specialists in a given field of technology for the configuration of the electrode structure 301 can select any set of groups electrode elements 401. For example, for a given wavelength, you can use the electrode elements from the fifth to the twentieth, providing, thus, the discovery of lamb waves, is offset from the center point 302. The presence in this embodiment, a sixteen radial separated electrode structures 301 allows to configure the sensor direction for each electrode structure 301, custom on a given frequency or wavelength. Directional detection lamb waves allows you to focus on sensor potential source of damage or use it in combination with one or more other similar sensors for triangulation position of the source of acoustic emission.

In this embodiment, the second electrode structure 303 placed in such a way that they are configured similarly the first electrode structure 301. Each of the first electrode structures 301 has electrode elements 401 of the same width, and focuses in particular a single direction with a narrow detection zone. Each of the second electrode structures 303, has electrode elements with radial increasing the width and less focused, it has diverging detection zone. The diverging detection zone provides more complex, however, more comprehensive data for analysis. In other words, the second electrode structure 303 can provide a greater range of detection of acoustic emission, potentially providing more accurate data on the place of damage.

Additional embodiment sensor 201, presented in figure 3, is used in the active acoustic monitoring system, which acoustic control system, which uses the first electrode structure 301, aimed to generate a lamb wave with a frequency that is selected, as described above. The direction of generated waves can also be selected by supply power to one or more appropriately oriented first of electrode structures 301. In this case, the second electrode structure 303 used to detect the reflected signals or reflections generated lamb wave caused by the damaged areas.

In another embodiment, as shown in figure 5, the sensor 501 additionally contains the Central third electrode structure 503, located on the Central point 504 sensor 501. The third electrode structure 503 contains two concentric annular electrode element, centered relative to the Central disk electrode element. Concentric annular electrode elements choose so that you can use a third electrode structure 503 as a multipurpose narrowband sensor. The resonant frequency of the third electrode structure 503 regulated by the total diameter of the selected group of annular electrode elements. The third electrode structure 503 is powered by a corresponding signal, processed by a method of the window, usually with a filter or filter Hamming to lamb waves. The third electrode structure 503 can be used to generate aimed lamb waves, so that the sensor 501 used as a pulse/echo sensor used in acoustic control system. In such systems, acoustic control are used non-destructive testing methods to detect corruption in complex systems such as aircraft designs.

In another embodiment, as shown in Fig.6, the sensor 601 additionally contains a fourth electrode structure 602, made up of radially arranged electrode elements. Fourth electrode structure includes 180 electrode elements, each electrode is placed so that it can detect components of the signal emitted by a third electrode structure 503 and reflected area of damage in a controlled design. Radial location of electrode series which is found on the reflected signal indicates the direction of the location of the damage relative to the sensor 601. Thus, the sensor 601 is suitable for use both active and passive acoustic monitoring systems to determine the location of directional signal.

In another embodiment, the sensor contains only a set of parallel electrode structures for custom detection lamb waves or generation. Additional embodiment sensor contains only a set of divergent electrode structures for custom detection lamb waves or generation. The specialists in this field of technology it is clear that parallel electrode structure are more energy efficient compared with divergent electrode structures, but have less physical area of action, at the same time, the divergent electrode structure consume more energy, but have a large physical area for action. In another embodiment, the sensor contains only the electrode structure, which are the third and fourth electrode structure, as described above.

In another embodiment, the sensor can be used in the procedure of installation of the necessary frequency settings, without the need of calculation of theoretical dispersion curves. For example, the sensor can be mounted on a working surface, and then activate using the method aimed lamb waves. The resulting signals generated by the sensor, then analyze when using classical methods, such as methods of two-dimensional fast Fourier transform (2D FFT), to determine the dispersion curves, including amplitude fashion lamb waves, so it is possible to adjust the frequency of the sensor for working detects this fashion wave. Each structure in the sensor can also be used to determine the dispersion curves in the correct direction and place within the area of the base of the sensor. As a rule, to obtain the results you are using a 32 sensor element 301. However, when using structures on both sides of the elements of 503 and 504, the number of elements in the structure 301 may be reduced to 16. On the other hand, maintaining constant number (32) elements in the structure 301 will increase the accuracy of determining the dispersion curve.

Additional embodiment used diverging patterns to collect the energy of low-frequency oscillations, for example, aerodynamic or vibration/noise of the engine. In another embodiment, the structure of such collect energy sensors placed so that the energy from one source of energy transmitted through the wireless connection from one sensor to another. Source of energy may be in the sensor itself. In another embodiment, the sensors are used for the collection of energy of high-frequency oscillations that allows this resembles the action of sensor to provide power to the surrounding sensors wirelessly through lamb wave.

The options for implementing the present invention sensors include the first and second radial electrode structure with thirty electrode elements, or third Central electrode structure with three elements. The specialists in this field of technology it is clear that with fewer elements will decrease the possible frequency resolution of electrode structures, while a larger number of electrode elements of possible frequency resolution of electrode structures will increase. Similarly, electrode items with small intervals or radially narrower electrode elements of a possible increase the frequency resolution of electrode structures, while the electrode items with large gaps or radially broader electrode elements reduce possible frequency resolution of electrode structures. In variants of realization of the invention may be provided for the structure of elements of various sizes, different intervals, so that you can get sensor with a variety of structures with different frequency or with different ranges of wavelengths and different resolutions. The structure can consist of electrode elements of unequal or located with different intervals to in this range provide the nonlinear frequency resolution.

The specialists in this field of technology it is clear that a full size sensor is determined by many factors. The greatest distance between elements is determined by the half of the maximum length of a wave of fashion lamb waves that you want to exclude, or filter upon detection of generating. In addition, this distance is also optimal equal to a multiple of the wavelength fashion lamb waves, which should be detected or generated.

The specialists in this field of technology it is clear that the sensors can be placed at any suitable configuration of the design, and where they apply. As described above, may be used in any combination of sensors with different characteristics, and, in addition, the combination may be combined depending on their application. For example, for some applications it may be suitable combination of one of the transmitting sensor with one or more host sensors. Besides, the sensor does not necessarily have to be the round form, to ensure the desired frequency range, resolution and orientation of the sensor can be used any suitable form.

The specialists in this field of technology is clear, though embodiments of the invention described above, illustrate the invention on the example of the basic structural elements of the plane, namely, the example of the fuselage, the invention is equally applicable to other items of the aircraft, such constructions, doors, engines, controls or the chassis.

The specialists in this field of technology it is clear that to make sensor, you can use a variety of technologies, such as using photolithography or functional lithography. The specialists in this field of technology it is clear that the sensor can be formed from any suitable piezoelectric material, for example, you can use - lead, polyvinylidene fluoride (PVDF), and it can also be formed from a composite layers or be columnar types. The specialists in this field of technology it is clear that the radial position of the electrode structures may coincide with the fiber orientation in structure containing the composite material.

The specialists in this field of technology it is clear that the device, which is embodied part of the invention or all of the present invention may be a device for General purposes, having the software installed for the enforcement of part of the invention or all of the invention. The device can be a single device or set of devices and software can be a program or set of programs. In addition, any portion of the software or all software used to carry out the invention may to provide communication by any suitable means of transmission or storage so that the software can be downloaded in one or more devices.

While the present invention was illustrated description of implementation options, and while options the implementation of the invention have been described in some detail, the applicant does not intend these details to limit or any limitation of the volume attached to the claims. Additional benefits and modification, undoubtedly, are the specialists in this field of technology. Therefore invention in its broader sense, not be limited to parts represented by the device and method of manufacture, as well as illustrative examples and described. Accordingly, there can be deviations are made, not beyond the creature or the total inventive concept.

1. Acoustic sensor, containing: piezoelectric substrate; total electrode is located on one side of the piezoelectric substrate; the first set of electrode structures, located on the opposite side of the piezoelectric substrate relative to total electrode, each of the first electrode structure situated radially relatively conditional Central point and contains a set of electrode elements arranged in circles, the first electrode structure is arranged with a possibility to select one or more groups of electrode elements from the set of the first electrode structure in order to configure the specified first electrode structure for a predefined frequency range, each specified the first electrode structure placed in a pre-defined radial direction relative to a specified notional the Central point to configure every listed first electrode structure of the signals, which have the appropriate orientation.

2. Acoustic sensor of claim 1, wherein the first electrode structure placed with the possibility to select one or more groups of electrode elements of a given the first electrode structure for setting specified the given first electrode structure for a predefined frequency range and to determine the position of groups on the conditional Central point.

3. Acoustic sensor according to claim 1 in which the electrode elements to one or more first electrode structures made of the same size in the direction of the circles.

4. Acoustic sensor according to claim 1 in which the electrode elements to one or more first electrode structures are made along with the size of circles is proportional to the distance from a specified notional Central point to a given electrode element.

5. Acoustic sensor according to claim 1, characterized in that it additionally contains located in circles second structure of radially placed electrode elements.

6. Acoustic sensor according to claim 1, characterized in that it additionally contains a third structure, centred on the conditional Central point.

7. Acoustic sensor 6, in which the third structure contains one or more concentric elements spatially separated in the radial direction.

8. Acoustic sensor according to claim 1, characterized in that is configured to work in the frequency range from 10 kHz to 20 MHz.

9. Acoustic sensor according to claim 1, characterized in that is configured to use with guided waves lamb.

10. Acoustic sensor according to claim 1 in which each electrode element is connected by a wire to a processor to signal received by the specified sensor.


 

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