Unidirectional non-dispersion guided wave transducer and design method thereof

Abstract

The invention discloses a unidirectional non-dispersion guided wave transducer and a design method thereof, the unidirectional non-dispersion guided wave transducer comprises a plurality of basic units, the basic units are arranged on the surface of a tested piece and are arranged in an array along the propagation direction of non-dispersion guided waves to form a basic unit array; the basic units are divided into positive basic units and negative basic units, and the positive basic units and the negative basic units generate force sources in opposite directions on the surface of the test piece; and designing the spatial distribution of the basic unit array and the excitation signal of the unidirectional non-dispersion guided wave transducer based on the linear frequency modulation signal. The unidirectional non-dispersion guided wave transducer provided by the invention only needs one transceiving circuit, the cost of a detection system is low, the transducer is simple in structure, and the reliability of detection equipment is high. In addition, the design method of the unidirectional non-dispersion guided wave transducer is suitable for different types of ultrasonic transducers, such as a piezoelectric ultrasonic transducer, a magnetostrictive ultrasonic transducer, an electromagnetic ultrasonic transducer and a laser ultrasonic transducer.

Description

Technical Field

[0001] This invention belongs to the field of ultrasonic guided wave nondestructive testing, and relates to a guided wave transducer, specifically a unidirectional non-dispersion guided wave transducer and its design method. Background Technology

[0002] Ultrasonic guided wave nondestructive testing technology has been widely used in the field of industrial nondestructive testing due to its advantages such as large detection range and high efficiency. Among them, non-dispersive guided waves (such as Rayleigh waves in thick plates and SHO guided waves in thin plates) have propagation speeds that do not change with frequency and stable signal characteristics, which significantly improves the interpretability of test results and makes them an ideal choice for defect detection.

[0003] Traditional guided wave transducers possess bidirectional excitation and reception characteristics, which is detrimental to defect localization. Even if a clear defect echo appears in the detection signal, it is impossible to directly determine which side of the transducer the defect is located on. To address this issue, researchers and engineers have developed unidirectional guided wave transducers. Currently, unidirectional transducers rely on a phased array system composed of multiple transducers, achieving beam orientation by controlling the excitation or reception phase of each transducer. However, this approach requires at least two independent transceiver circuits, which not only increases the cost and structural complexity of the detection system but also reduces the overall reliability of the equipment due to the increased number of electronic components. Therefore, developing a low-cost, high-reliability, and unidirectional non-dispersion guided wave transducer is of great significance for improving the engineering applicability of guided wave non-destructive testing technology. Summary of the Invention

[0004] To address the aforementioned problems in the background technology, this invention provides a unidirectional non-dispersion guided wave transducer that uses only one set of transceiver circuits and its design method.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A unidirectional non-dispersion guided wave transducer comprises several basic units, wherein:

[0007] The basic units are arranged on the surface of the test piece and in an array along the propagation direction of the non-dispersion guided wave to form a basic unit array.

[0008] The basic unit is divided into two types: positive basic unit and negative basic unit. Positive basic unit and negative basic unit generate force sources with opposite directions on the surface of the specimen.

[0009] The criterion for judging the basic unit is: when the transducer is used as an excitation transducer, the spatial distribution of the force source generated by the transducer on the surface of the specimen is approximately the same as the spatial distribution of the projection of the basic unit on the surface of the specimen.

[0010] The basic units include, but are not limited to, the piezoelectric crystal in a piezoelectric ultrasonic transducer, the magnetostrictive patch in a magnetostrictive transducer, the zigzag coil in a zigzag coil electromagnetic ultrasonic transducer, and the permanent magnet in a periodic permanent magnet electromagnetic ultrasonic transducer.

[0011] A structural design method for the above-mentioned unidirectional non-dispersion guided wave transducer, the method being based on designing the spatial distribution of the basic unit array using a linear frequency modulation signal, includes the following steps:

[0012] Step (1) Select a linear frequency modulation signal in the time domain According to the pulse width modulation method, the linear frequency modulated signal in the time domain is... This is converted into a combination of multiple rectangular signals in the time domain, i.e., a pulse width modulation signal in the time domain. ;

[0013] Step (2) Utilize the phase velocity of the non-dispersion guided wave and formula ,Will Converted into a pulse width modulation signal in space , That is, the spatial distribution of the basic unit;

[0014] Step (3) according to Design a basic cell array. Arrange the basic elements at position 1. Negative basic elements are arranged at positions -1. No basic units are placed at positions where the value is 0.

[0015] In this invention, the linear frequency modulation signal in the time domain Satisfying formula (1):

[0016] (1)

[0017] In the formula, and They represent signals respectively The start and end times; It is a signal The instantaneous rate of change of frequency; and They represent signals respectively The initial frequency and cutoff frequency.

[0018] In this invention, the pulse width modulation method is as follows: The area enclosed by the signal and the coordinate axes is equal to the area enclosed by the rectangular signal and the coordinate axes. The center position of the rectangular signal corresponds to... The peak position of the signal; multiple rectangular signals form a pulse width modulation signal. .

[0019] A method for designing the excitation signal of the aforementioned unidirectional non-dispersion guided wave transducer, the method being based on a linear frequency modulation signal in the time domain. Design the excitation signal for a unidirectional non-dispersion guided wave transducer, thereby achieving unidirectional enhancement of the received signal by the non-dispersion guided wave transducer. The excitation signal for the unidirectional non-dispersion guided wave transducer... It is a linear frequency modulated signal, and The following relationship must be satisfied: and Their frequency band ranges are the same. The signal length in the time domain is 2 times, that is Satisfying formula (2) or formula (3):

[0020] (2)

[0021] (3)

[0022] When the excitation signal satisfies formula (2), that is, the excitation signal is At this time, the amplitude of the received signal on the right side of the transducer is enhanced, while the received signal on the left side of the transducer is weakened. This is a right-side enhanced unidirectional non-dispersion guided wave transducer.

[0023] When the excitation signal satisfies formula (3), that is, the excitation signal is At this time, the amplitude of the received signal on the left side of the transducer is enhanced, while the received signal on the right side of the transducer is weakened. This is a left-side enhanced unidirectional non-dispersion guided wave transducer.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] This invention is based on linear frequency modulation signal The basic unit array of the non-dispersion guided wave transducer is designed using the pulse width modulation method, and then the signal is modulated by another linear frequency with the same frequency band and twice the duration. As an excitation signal, the unidirectional amplification of the received signal by the non-dispersion guided wave transducer is achieved, and the amplification direction can be controlled by changing the excitation signal. Compared with existing technologies, the unidirectional non-dispersion guided wave transducer of this invention requires only one transceiver circuit, resulting in low detection system cost, simple transducer structure, and high reliability of detection equipment. Furthermore, the design method of the unidirectional non-dispersion guided wave transducer is applicable to different types of ultrasonic transducers, such as piezoelectric ultrasonic transducers, magnetostrictive ultrasonic transducers, electromagnetic ultrasonic transducers, and laser ultrasonic transducers. Attached Figure Description

[0026] Figure 1 A schematic diagram of a detection system for a unidirectional non-dispersion guided wave transducer;

[0027] Figure 2 This is a schematic diagram of the excitation signal, structure, and unidirectional enhancement result of a unidirectional non-dispersion guided wave transducer.

[0028] Figure 3 A schematic diagram of a unidirectional SHO guided periodic permanent magnet electromagnetic ultrasonic transducer.

[0029] Figure 4 Linear frequency modulation signal in the time domain ;

[0030] Figure 5 Pulse width modulated signal in the time domain ;

[0031] Figure 6 Pulse width modulated signal in space ;

[0032] Figure 7 The excitation signal for a unidirectional non-dispersion guided wave transducer ;

[0033] Figure 8 The received signal is from the right-side enhanced unidirectional SHO guided wave periodic permanent magnet electromagnetic ultrasonic transducer.

[0034] Figure 9 The excitation signal for a unidirectional non-dispersion guided wave transducer ;

[0035] Figure 10 The signal received by the left-side enhanced unidirectional SHO guided periodic permanent magnet electromagnetic ultrasonic transducer;

[0036] Figure 11 Schematic diagram of a unidirectional Rayleigh wave zigzag coil electromagnetic ultrasonic transducer;

[0037] Figure 12 The received signal is from the right-side enhanced unidirectional Rayleigh wave zigzag coil electromagnetic ultrasonic transducer.

[0038] Figure 13 This is the received signal from the enhanced unidirectional Rayleigh wave zigzag coil electromagnetic ultrasonic transducer on the left. Detailed Implementation

[0039] The technical solution of the present invention will be further described below with reference to the accompanying drawings, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention that do not depart from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0040] Example 1:

[0041] like Figure 1 As shown, the testing configuration of the unidirectional SHO guided periodic permanent magnet electromagnetic ultrasonic transducer includes a transceiver circuit, the unidirectional SHO guided periodic permanent magnet electromagnetic ultrasonic transducer, and the test piece. The transceiver circuit includes an excitation module and a receiving module. The excitation module generates a high-voltage excitation signal of arbitrary waveform and can pass the excitation signal into the unidirectional SHO guided periodic permanent magnet electromagnetic ultrasonic transducer. The receiving module amplifies, filters, and stores the weak electrical signal collected by the unidirectional SHO guided periodic permanent magnet electromagnetic ultrasonic transducer, and can be used with an external oscilloscope to display the received signal waveform in real time.

[0042] like Figure 2 and Figure 3 As shown, the unidirectional SHO guided wave periodic permanent magnet electromagnetic ultrasonic transducer consists of an array of basic units, where the basic units are permanent magnets. The permanent magnets are arranged on the surface of the test piece along the propagation direction of the SHO guided wave, forming a periodic permanent magnet array. Permanent magnets magnetized downwards along the test piece surface are designated as positive permanent magnets, and those not magnetized are designated as negative permanent magnets. The positive and negative permanent magnets generate force sources in opposite directions on the test piece surface. The spatial distribution of the force sources is approximately the same as the spatial distribution of the permanent magnets along the propagation direction of the guided wave.

[0043] The design steps for the aforementioned periodic permanent magnet array are as follows:

[0044] Step (1) as follows Figure 4 As shown, a linear frequency modulation signal in the time domain is selected. According to the pulse width modulation method, the linear frequency modulated signal in the time domain is... This is converted into a combination of multiple rectangular signals in the time domain, i.e., a pulse width modulation signal in the time domain. ,like Figure 5 As shown;

[0045] Step (2) Utilize the phase velocity of the non-dispersion guided wave and formula ,Will Converted into a pulse width modulation signal in space , This refers to the spatial distribution of a periodic permanent magnet array, such as... Figure 6 As shown;

[0046] Step (3) according to Design a periodic permanent magnet array, A positive permanent magnet is placed at position 1. A negative permanent magnet is placed at position -1. Permanent magnets are not placed at positions where the value is 0, such as Figure 3 As shown.

[0047] The linear frequency modulation signal in the time domain mentioned above like Figure 4 As shown, it satisfies formula (4):

[0048] (4)

[0049] in, and They represent signals respectively The start and end times; It is a signal The instantaneous rate of change of frequency; and They represent signals respectively The initial frequency and cutoff frequency.

[0050] like Figure 4 and Figure 5 As shown, the pulse width modulation method described above is as follows: The area enclosed by the signal and the coordinate axes ( Figure 4 The shaded area is equal to the area enclosed by the rectangular signal and the coordinate axes. Figure 5 (Shadow area in the image), the center position of the rectangular signal corresponds to The peak position of the signal; multiple rectangular signals form a pulse width modulation signal. .

[0051] Based on linear frequency modulation signal in the time domain The excitation signal of a unidirectional SHO guided periodic permanent magnet electromagnetic ultrasonic transducer is designed to achieve unidirectional enhancement of the received signal. Specifically, the excitation signal of the unidirectional SHO guided periodic permanent magnet electromagnetic ultrasonic transducer... It is a linear frequency modulated signal, and The following relationship must be satisfied: and Their frequency band ranges are the same. The signal length in the time domain is 2 times, that is Satisfying formula (5) or formula (6):

[0052] (5)

[0053] (6)

[0054] When the excitation signal satisfies formula (5), that is, the excitation signal is hour( Figure 7 The echo signal amplitude on the right side of the transducer is amplified, while the echo signal on the left side is weakened. This indicates a right-side enhanced unidirectional SHO guided wave periodic permanent magnet electromagnetic ultrasonic transducer. The experimental results of the received signal are as follows: Figure 8 As shown.

[0055] When the excitation signal satisfies formula (6), that is, the excitation signal is hour( Figure 9 The received signal amplitude on the left side of the transducer is amplified, while the received signal on the right side is weakened. This is a left-enhanced unidirectional SHO guided wave periodic permanent magnet electromagnetic ultrasonic transducer. The experimental results of the received signal are as follows: Figure 10 As shown.

[0056] Example 2:

[0057] like Figure 1 As shown, the testing system for a unidirectional Rayleigh wave zigzag coil electromagnetic ultrasonic transducer includes a transceiver circuit, a unidirectional Rayleigh wave zigzag coil electromagnetic ultrasonic transducer, and the test piece. The transceiver circuit includes an excitation module and a receiving module. The excitation module generates a high-voltage excitation signal of arbitrary waveform and can pass the excitation signal into the unidirectional Rayleigh wave zigzag coil electromagnetic ultrasonic transducer. The receiving module amplifies, filters, and stores the weak electrical signal acquired by the unidirectional Rayleigh wave zigzag coil electromagnetic ultrasonic transducer, and can be used with an external oscilloscope to display the received signal waveform in real time.

[0058] like Figure 2 and Figure 11 As shown, the unidirectional Rayleigh wave zigzag coil electromagnetic ultrasonic transducer consists of an array of basic units, where each basic unit is a coil. The coils are arranged on the surface of the test piece along the propagation direction of the Rayleigh wave, forming a zigzag coil array. A coil is considered positive when the current direction is outward from the plane, and negative otherwise. The positive and negative coils generate force sources in opposite directions on the test piece surface. The spatial distribution of the force sources is approximately the same as the spatial distribution of the coils along the waveguide propagation direction.

[0059] The design steps for the above-mentioned tortuous coil array are as follows:

[0060] Step (1) as follows Figure 4 As shown, a linear frequency modulation signal in the time domain is selected. According to the pulse width modulation method, the linear frequency modulated signal in the time domain is... This is converted into a combination of multiple rectangular signals in the time domain, i.e., a pulse width modulation signal in the time domain. ,like Figure 5 As shown;

[0061] Step (2) Utilize the phase velocity of the non-dispersion guided wave and formula ,Will Converted into a pulse width modulation signal in space , This refers to the spatial distribution of the coil array, such as... Figure 6 As shown;

[0062] Step (3) according to Design a zigzag coil array, Arrange the positive coil at position 1. The negative coil is positioned at the -1 position. No coil is placed at the position where the value is 0, such as Figure 11 As shown.

[0063] The linear frequency modulation signal in the time domain mentioned above like Figure 4 As shown, it satisfies formula (7):

[0064] (7)

[0065] in, and They represent signals respectively The start and end times; It is a signal The instantaneous rate of change of frequency; and They represent signals respectively The initial frequency and cutoff frequency.

[0066] like Figure 4 and Figure 5 As shown, the pulse width modulation method described above is as follows: The area enclosed by the signal and the coordinate axes ( Figure 4 The shaded area is equal to the area enclosed by the rectangular signal and the coordinate axes. Figure 5 (Shadow area in the image), the center position of the rectangular signal corresponds to The peak position of the signal; multiple rectangular signals form a pulse width modulation signal. .

[0067] Based on linear frequency modulation signal in the time domain The excitation signal for a unidirectional Rayleigh wave zigzag coil electromagnetic ultrasonic transducer is designed to achieve unidirectional enhancement of the received signal. Specifically, the excitation signal for the Rayleigh wave zigzag coil electromagnetic ultrasonic transducer... It is a linear frequency modulated signal, and The following relationship must be satisfied: and Their frequency band ranges are the same. The signal length in the time domain is 2 times, that is Satisfying formula (8) or formula (9):

[0068] (8)

[0069] (9)

[0070] When the excitation signal satisfies formula (8), that is, the excitation signal is hour( Figure 7 The echo signal amplitude on the right side of the transducer is amplified, while the echo signal on the left side is weakened. This is a right-side enhanced unidirectional Rayleigh wave zigzag coil electromagnetic ultrasonic transducer. The finite element simulation results of the received signal are as follows: Figure 12 As shown.

[0071] When the excitation signal satisfies formula (9), that is, the excitation signal is hour( Figure 9 The received signal amplitude on the left side of the transducer is amplified, while the received signal on the right side is weakened. This is a left-side enhanced unidirectional Rayleigh wave zigzag coil electromagnetic ultrasonic transducer. The finite element simulation results of the received signal are as follows: Figure 13 As shown.

Claims

1. A unidirectional, non-dispersive, guided-wave transducer, characterized by The transducer comprises several basic units, wherein: The basic units are arranged on the surface of the tested object and arrayed along the propagation direction of the non-dispersive guided wave to form a basic unit array; The basic units are divided into positive basic units and negative basic units, and the positive basic units and the negative basic units generate force sources with opposite directions on the surface of the tested object.

2. The unidirectional, non-dispersive guided-wave transducer of claim 1, wherein The basic units are piezoelectric wafer, magnetostrictive patch, meander coil or permanent magnet.

3. A method of designing the structure of a unidirectional non-dispersive guided wave transducer according to any one of claims 1-2, characterized in that The method is based on the linear frequency modulation signal to design the spatial distribution of the basic unit array, and comprises the following steps: Step (1) Select a linear frequency modulation signal in the time domain According to the pulse width modulation method, the linear frequency modulated signal in the time domain is... This is converted into a combination of multiple rectangular signals in the time domain, i.e., a pulse width modulation signal in the time domain. ; Step (2) uses the phase velocity of the non-dispersive guided wave and the formula converts into a pulse width modulated signal in space , which is the spatial distribution of the basic unit; Step (3) is performed according to designing an array of elementary cells, arranging a positive elementary cell at positions for which the value is 1, arranging a negative elementary cell at positions for which the value is -1, not arranging an elementary cell at positions for which the value is 0.

4. The method of designing a structure of a unidirectional non-dispersive leaky wave transducer according to claim 3, characterized in that Linear frequency modulated signal in the time domain satisfies equation (1): （1）； wherein and represent the start time and the end time of the signal respectively; is the instantaneous frequency rate of the signal ; and represent the initial frequency and the cut-off frequency of the signal respectively.

5. The method of designing a structure of a unidirectional non-dispersive leaky wave transducer according to claim 3, characterized in that The pulse width modulation method is: The area surrounded by the signal and the coordinate axis is equal to the area surrounded by the rectangular signal and the coordinate axis, and the center position of the rectangular signal corresponds The peak position of the signal, and the plurality of rectangular signals constitute a pulse width modulation signal .

6. A method of designing an excitation signal for a unidirectional non-dispersive waveguide transducer as claimed in any one of claims 1 to 2, characterised by The method is based on a linear frequency modulation signal in the time domain. Design the excitation signal for a unidirectional non-dispersion guided wave transducer, thereby achieving unidirectional enhancement of the received signal by the non-dispersion guided wave transducer. The excitation signal for the unidirectional non-dispersion guided wave transducer... It is a linear frequency modulated signal, and The following relationship must be satisfied: and Their frequency band ranges are the same. The signal length in the time domain is 2 times, that is Satisfying formula (2) or formula (3): （2）； （3）； wherein and represent the start time and the end time of the signal , respectively; and represent the initial frequency and the cut-off frequency of the signal , respectively; is the rate of change of the instantaneous frequency of the signal .

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