An ultrasonic guided wave damage detection method based on modal conversion welded pipe

Abstract

The welding pipe ultrasonic guided wave damage detection method based on modal conversion can realize real-time detection of global damage of the pipe, including the non-welding seam area and the welding seam area, can effectively avoid the influence of the pipe welding seam on the damage detection, and is particularly suitable for the needs of nondestructive testing of the welded pipe.

Description

Technical Field

[0001] This invention relates to the field of ultrasonic guided wave nondestructive testing technology, and in particular to an ultrasonic guided wave damage detection method for welded pipes based on mode conversion. Background Technology

[0002] Long-distance welded pipelines are widely used in the petroleum, chemical, and natural gas industries as a fast and efficient transportation tool. However, due to the influence of complex environmental factors such as temperature and load, different types of damage can occur during pipeline service. This damage can continue to develop and expand, leading to leaks and economic losses. Therefore, real-time acquisition of pipeline damage information is essential.

[0003] While existing non-destructive testing (NDT) technologies can meet the needs of welded pipe damage detection to a certain extent, existing NDT technologies, such as the pipe inspection system and method disclosed in patent application CN108562642A, use longitudinal ultrasonic guided wave mode to complete pipe defect detection. Since both pipe welds and damages cause ultrasonic guided waves to be reflected, generating reflected echoes, the reflected echoes from the welds will overlap with the reflected echoes from the damages at the welds, making analysis and judgment difficult. Therefore, this method has the problem of difficulty in detecting weld areas.

[0004] Therefore, it is necessary to develop a new detection method to solve the problem of difficulty in detecting weld areas in existing detection methods. Summary of the Invention

[0005] The purpose of this invention is to provide an ultrasonic guided wave damage detection method for welded pipes based on mode conversion, so as to solve the problem that existing detection methods have difficulty in detecting the weld area.

[0006] The technical solution of this invention is:

[0007] An ultrasonic guided wave damage detection method for welded pipes based on mode conversion, characterized in that the ultrasonic guided wave damage detection method includes the following steps:

[0008] (1) Two rings of piezoelectric sensors are evenly arranged at the same end of the welded pipe to be inspected, with each ring containing 2 piezoelectric sensors. M Each piezoelectric sensor serves as both an exciter and a receiver, used to excite and receive ultrasonic guided wave signals.

[0009] (2) One ring of piezoelectric sensors at the end of the welded pipe acts as an exciter to excite axisymmetric mode ultrasonic guided waves in the welded pipe, and the other ring of piezoelectric sensors at the end of the welded pipe acts as a receiver to receive ultrasonic guided wave signals separately.

[0010] (3) Based on the ultrasonic guided wave signal received by the receiver, extract the axisymmetric modes contained therein and the modes generated due to mode transition. Bending mode signal;

[0011] (4) Use the Hilbert transform to find the axisymmetric modes and The envelope of the bending mode signal is obtained, the corresponding wave packets of the bending mode signal and the axisymmetric mode signal are identified, and the amplitude ratio of the corresponding wave packets in the bending mode signal and the axisymmetric mode signal is calculated.

[0012] (5) Set the threshold to 0.2 and determine whether the bending mode signal packet is caused by damage. The packet with the amplitude ratio of the bending mode to the axisymmetric mode is greater than the set threshold is judged as a damaged packet; otherwise, it is judged as a non-damaged packet.

[0013] (6) Extract the moment corresponding to the amplitude of the first damage wave packet in the bending mode signal, calculate the distance from the damage to the excitation end based on the group velocity of the axisymmetric mode and the bending mode, and determine the axial position of the damage.

[0014] In step (2), when exciting the axisymmetric mode ultrasonic guided wave, the same signal is simultaneously input into all exciters, and the input signal is modulated using a Hanning window. Periodic sinusoidal signal.

[0015] In step (3), the axisymmetric mode and The method for extracting bending mode signals is as follows:

[0016]

[0017] in Represents an axisymmetric modal signal. express First-order bending mode signal, It is a positive integer. Indicates the number is The signal received by the receiver This indicates the number of receivers; the receiver numbering method is to select one receiver and assign it number 1, then sequentially number the remaining sensors (number 2, 1, 2, 3, 4) along the circumference of the pipe in a clockwise or counterclockwise direction. M Number.

[0018] In step (4), the wave packet determination criteria for the axisymmetric mode and bending mode signals are that the peak values ​​of the wave packets correspond to the time that the wave packets meet the following conditions.

[0019]

[0020] in and These are the times corresponding to the peak values ​​of the wave packets of the axisymmetric and bending modes, respectively. and These are the axisymmetric and bending mode group velocities, respectively. Indicates the center frequency of the excitation signal. This indicates the number of excitation signal cycles.

[0021] The method for calculating the amplitude ratio of the bending mode and the axisymmetric mode wave packet in step (4) is as follows:

[0022]

[0023] in and These represent the amplitudes of the wave packets in the axisymmetric mode and the bending mode, respectively. This represents the amplitude ratio of the wave packet for the bending mode and the axisymmetric mode.

[0024] The calculation method for the distance from the damage to the excitation end in step (6) is as follows:

[0025]

[0026] in The distance from the excitation end to the damage point. It has the same meaning as in formula (3).

[0027] The beneficial effects of this invention are as follows:

[0028] This ultrasonic guided wave damage detection method for welded pipes based on mode conversion identifies damage scattering signals by comparing extracted axisymmetric and bending mode ultrasonic guided wave signals. It can achieve real-time damage detection across the entire pipe area, including both non-weld and welded zones, effectively avoiding the influence of pipe welds on damage detection. It is particularly suitable for the needs of non-destructive testing of welded pipes. Attached Figure Description

[0029] Figure 1 This is a flowchart of the steps of the present invention;

[0030] Figure 2 The pipeline numerical simulation model established for the numerical simulation of this invention;

[0031] Figure 3 This is a schematic diagram showing the exciter and receiver arranged along the circumference of the pipeline during numerical simulation of the present invention.

[0032] Figure 4 This is a time-domain diagram of the excitation signal during numerical simulation of this invention;

[0033] Figure 5 This is the frequency domain diagram of the excitation signal during numerical simulation of this invention;

[0034] Figure 6 The F(1,3) mode signal and its envelope extracted during the numerical simulation of this invention;

[0035] Figure 7 The L(0,2) mode signal and its envelope are extracted during the numerical simulation of this invention. Detailed Implementation

[0036] The ultrasonic guided wave damage detection method for welded pipes based on mode conversion is characterized by comprising the following steps:

[0037] (1) Two rings of piezoelectric sensors are evenly arranged at the same end of the welded pipe to be inspected, with each ring containing 2 piezoelectric sensors. M Each piezoelectric sensor serves as both an exciter and a receiver, used to excite and receive ultrasonic guided wave signals.

[0038] (2) One ring of piezoelectric sensors at the end of the welded pipe acts as an exciter to excite axisymmetric mode ultrasonic guided waves in the welded pipe, and the other ring of piezoelectric sensors at the end of the welded pipe acts as a receiver to receive ultrasonic guided wave signals separately.

[0039] In step (2), when exciting the axisymmetric mode ultrasonic guided wave, the same signal is simultaneously input into all exciters, and the input signal is modulated using a Hanning window. Periodic sinusoidal signal.

[0040] (3) Based on the ultrasonic guided wave signal received by the receiver, extract the axisymmetric modes contained therein and the modes generated due to mode transition. Bending mode signal;

[0041] In step (3), the axisymmetric mode and The method for extracting bending mode signals is as follows:

[0042]

[0043] in Represents an axisymmetric modal signal. express First-order bending mode signal, It is a positive integer. Indicates the number is The signal received by the receiver This indicates the number of receivers; the receiver numbering method is to select one receiver and assign it number 1, then sequentially number the remaining sensors (number 2, 1, 2, 3, 4) along the circumference of the pipe in a clockwise or counterclockwise direction. M Number.

[0044] (4) Use the Hilbert transform to find the axisymmetric modes and The envelope of the bending mode signal is obtained, the corresponding wave packets of the bending mode signal and the axisymmetric mode signal are identified, and the amplitude ratio of the corresponding wave packets in the bending mode signal and the axisymmetric mode signal is calculated.

[0045] In step (4), the wave packet determination criteria for the axisymmetric mode and bending mode signals are that the peak values ​​of the wave packets correspond to the time that the wave packets meet the following conditions.

[0046]

[0047] in and These are the times corresponding to the peak values ​​of the wave packets of the axisymmetric and bending modes, respectively. and These are the axisymmetric and bending mode group velocities, respectively. Indicates the center frequency of the excitation signal. This indicates the number of excitation signal cycles.

[0048] The method for calculating the amplitude ratio of the bending mode and the axisymmetric mode wave packet in step (4) is as follows:

[0049]

[0050] in and These represent the amplitudes of the wave packets in the axisymmetric mode and the bending mode, respectively. This represents the amplitude ratio of the wave packet for the bending mode and the axisymmetric mode.

[0051] (5) Set the threshold to 0.2 to determine whether the bending mode signal packet is caused by damage. The packet with the amplitude ratio of the bending mode to the axisymmetric mode is greater than the set threshold is judged as a damaged packet; otherwise, it is judged as a non-damaged packet. The threshold setting is determined by the error level during detection. The larger the error, the larger the threshold.

[0052] (6) Extract the moment corresponding to the amplitude of the first damage wave packet in the bending mode signal, calculate the distance from the damage to the excitation end based on the group velocity of the axisymmetric mode and the bending mode, and determine the axial position of the damage.

[0053] The calculation method for the distance from the damage to the excitation end in step (6) is as follows:

[0054]

[0055] in The distance from the excitation end to the damage point. It has the same meaning as in formula (3).

[0056] Based on the different characteristics of weld seam and damage reflection echo, namely, weld seam reflection echo is an axisymmetric wave and damage reflection echo contains bending mode wave, in steps (3) to (4), by extracting axisymmetric mode and bending mode signals and calculating the amplitude ratio of bending mode to axisymmetric mode, the influence of weld seam reflection echo signal can be effectively avoided, thus solving the problem of difficult detection of weld seam area proposed in the background art.

[0057] To verify the correctness of this application, the applicant conducted numerical simulations, the specific methods of which are as follows:

[0058] (1) A numerical simulation model of the pipeline was established using ABAQUS software (see the instruction manual appendix). Figure 2 The pipe is 2m long, with an inner diameter of 90mm and an outer diameter of 100mm. Its wall thickness is 5mm, and its elastic modulus, density, and Poisson's ratio are 201GPa, 7800kg / m³, and 100mm respectively. 3 And 0.3.

[0059] (2) A ring of exciters and receivers is installed at the left end of the pipeline, with 16 exciters and 16 receivers, evenly distributed along the circumference of the pipeline (see the instruction manual appendix). Figure 3 The receivers are numbered sequentially from 1 to 16. In this embodiment, the receiver directly facing the damage center is numbered 1. In the numerical simulation, both the exciter and the receiver are represented by nodes. A slotted through-damage is set on the weld at a distance of 1m from the excitation end, with a damage length of 20mm and a width of 5mm. The excitation signal is a 10-cycle sinusoidal signal modulated by a Hanning window, with a signal center frequency of 50kHz. The time-domain plot and normalized frequency-domain plot of the excitation signal are shown below. Figure 4 and Figure 5 As shown. Since the axisymmetric L(0,2) mode has a faster propagation speed, the L(0,2) mode is selected as the damage detection mode in this embodiment.

[0060] (3) An axisymmetric loading method is adopted, and the same excitation signal is simultaneously input into all exciters to excite axisymmetric L(0,2) mode ultrasonic guided waves. Each receiver receives the ultrasonic guided wave signal separately, and is numbered as follows: The signal received by the receiver of number is denoted as There are a total of 16 groups of signals. At non-axisymmetric damage sites, the axisymmetric L(0,2) mode undergoes mode transformation, generating first-order bending F(1,3) and second-order bending F(2,3) modes. In this embodiment, the F(1,3) mode is selected as the basis for damage identification.

[0061] (4) Based on the signal received by the receiver, extract the L(0,2) mode signal contained therein according to formulas (1) and (2) respectively. and F(1,3) mode signals At this point, both formulas (1) and (2) take... , taken from formula (2) The envelopes of the L(0,2) mode and F(1,3) mode signals are obtained using the Hilbert transform, respectively. The extracted F(1,3) mode signals and their envelopes are shown below. Figure 6 As shown. The extracted L(0,2) mode signal and its envelope are as follows. Figure 7 As shown in the diagram, two distinct wave packets are visible in the envelope diagram of the F(1,3) mode signal, appearing at 400~600μs and 800~1000μs respectively. The L(0,2) mode signal has four distinct wave packets, among which the wave packets at 400~600μs and 800~1000μs correspond to the two wave packets in the F(1,3) mode signal. That is, the second and fourth wave packets of the L(0,2) mode signal correspond to the two wave packets in the F(1,3) mode signal.

[0062] (5) Based on the signal envelope diagram, the amplitude of the first wave packet of the F(1,3) mode signal is 0.000156 mm, and the amplitude of the second wave packet of the corresponding L(0,2) mode signal is 0.000426 mm. Therefore, the amplitude ratio of the F(1,3) mode to the L(0,2) mode is... Set threshold ,at this time Therefore, it can be determined that the first wave packet in the F(1,3) mode signal is the first damage scattering wave.

[0063] (6) According to the signal envelope diagram, the time corresponding to the maximum value of the first wave packet in the F(1,3) mode signal is 504.2μs. At the current frequency, the group velocities of L(0,2) and F(1,3) modes are 5241m / s and 4920m / s, respectively. Substituting these values ​​into formula (5), the damage distance from the excitation end is calculated to be 1.026m, which is 2.6% less than the actual damage location. The positioning is relatively accurate.

[0064] This ultrasonic guided wave damage detection method for welded pipes based on mode conversion identifies damage scattering signals by comparing extracted axisymmetric and bending mode ultrasonic guided wave signals. It can achieve real-time damage detection across the entire pipe area, including both non-weld and welded zones, effectively avoiding the influence of pipe welds on damage detection. It is particularly suitable for the needs of non-destructive testing of welded pipes.

Claims

1. An ultrasonic guided wave damage detection method for welded pipes based on mode conversion, characterized in that: The ultrasonic guided wave damage detection method includes the following steps: (1) Two rings of piezoelectric sensors are evenly arranged at the same end of the welded pipe to be tested. Each ring has M piezoelectric sensors, which are used as exciters and receivers to excite and receive ultrasonic guided wave signals. (2) One ring of piezoelectric sensors at the end of the welded pipe acts as an exciter to excite axisymmetric mode ultrasonic guided waves in the welded pipe, and the other ring of piezoelectric sensors at the end of the welded pipe acts as a receiver to receive ultrasonic guided wave signals separately. (3) Based on the ultrasonic guided wave signal received by the receiver, extract the axisymmetric modes contained therein and the modes generated due to mode conversion. Bending mode signal; (4) Use the Hilbert transform to find the axisymmetric modes and The envelope of the bending mode signal is obtained, the corresponding wave packets of the bending mode signal and the axisymmetric mode signal are identified, and the amplitude ratio of the corresponding wave packets in the bending mode signal and the axisymmetric mode signal is calculated. (5) Set the threshold to 0.2 and determine whether the bending mode signal packet is caused by damage. The packet with the amplitude ratio of the bending mode to the axisymmetric mode is greater than the set threshold is judged as a damaged packet; otherwise, it is judged as a non-damaged packet. (6) Extract the moment corresponding to the amplitude of the first damage wave packet in the bending mode signal, calculate the distance from the damage to the excitation end based on the group velocity of the axisymmetric mode and the bending mode, and determine the axial position of the damage; In step (4), the wave packet determination criteria for the axisymmetric mode and bending mode signals are that the peak values ​​of the wave packets correspond to the time that the wave packets meet the following conditions. (3) in and These are the times corresponding to the peak values ​​of the wave packets of the axisymmetric and bending modes, respectively. and These are the axisymmetric and bending mode group velocities, respectively. Indicates the center frequency of the excitation signal. This indicates the number of excitation signal cycles.

2. The ultrasonic guided wave damage detection method for welded pipes based on mode conversion according to claim 1, characterized in that: In step (2), when exciting the axisymmetric mode ultrasonic guided wave, the same signal is simultaneously input into all exciters, and the input signal is modulated using a Hanning window. Periodic sinusoidal signal.

3. The ultrasonic guided wave damage detection method for welded pipes based on mode conversion according to claim 1, characterized in that: In step (3), the axisymmetric mode and The method for extracting bending mode signals is as follows: (1) (2) in Represents an axisymmetric modal signal. express First-order bending mode signal, It is a positive integer. Indicates the number is The signal received by the receiver This indicates the number of receivers. The receiver numbering method is to select one receiver and number it 1, and then number the remaining sensors sequentially from 2 to M along the circumference of the pipe in a clockwise or counterclockwise direction.

4. The ultrasonic guided wave damage detection method for welded pipes based on mode conversion according to claim 1, characterized in that: The method for calculating the amplitude ratio of the bending mode and the axisymmetric mode wave packet in step (4) is as follows: (4) in and These represent the amplitudes of the wave packets in the axisymmetric mode and the bending mode, respectively. This represents the amplitude ratio of the wave packet for the bending mode and the axisymmetric mode.

5. The ultrasonic guided wave damage detection method for welded pipes based on mode conversion according to claim 1, characterized in that: The calculation method for the distance from the damage to the excitation end in step (6) is as follows: (5) in The distance from the excitation end to the damage point. , , , , It has the same meaning as in formula (3).

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