Nondestructive testing method and system for PE pipeline hot melt joint based on microwave imaging

Abstract

The application discloses a kind of based on microwave imaging's PE pipeline hot melt joint nondestructive testing method and system, it is related to nondestructive testing technical field.The method includes: to each to-be-measured point of PE pipe, emit multiple frequency microwave signals, receive the echo signal reflected back by each to-be-measured point;The echo signal includes the time-domain signal and the frequency-domain signal corresponding to each frequency microwave signal;The frequency-domain signal greater than the microwave characteristic response value of matrix in the echo signal reflected back by each to-be-measured point is deleted to obtain the correction echo signal of each to-be-measured point;The minimum value in the maximum value in the frequency-domain signal corresponding to each frequency microwave signal in the correction echo signal of each to-be-measured point is as the multi-frequency microwave characteristic response value corresponding to each to-be-measured point;According to the multi-frequency microwave characteristic response value corresponding to each to-be-measured point and threshold range, determine the abnormal area of the PE pipe.The application can improve the precision of detection result.

Description

Technical Field

[0001] This invention relates to the field of nondestructive testing technology, and in particular to a nondestructive testing method and system for PE pipe thermofusion joints based on microwave imaging. Background Technology

[0002] PE pipes are widely used in buried gas pipelines and water supply and drainage pipelines due to their advantages such as high strength, lightweight, and good resistance to moisture and corrosion. However, various defects can easily occur during the production, transportation, installation, and use of these pipes. During on-site installation and welding, defects at the weld joint are particularly severe due to complex site conditions, and most PE pipe failures occur at the joint location. Therefore, it is crucial to use non-destructive testing techniques to ensure the integrity and safety of PE pipes in a timely manner to detect internal defects at the joints.

[0003] Currently, non-destructive testing technologies applied to PE pipe hot-melt joints include infrared, X-ray, and ultrasonic testing. However, these methods all have many shortcomings. For example, infrared imaging technology has low image resolution, X-ray testing has low detection accuracy due to the absorption of X-rays by PE material, and ultrasonic testing relies on changes in the acoustic impedance of the material for detection. However, many defects in PE pipes, such as cold welding, do not cause changes in acoustic impedance. Therefore, ultrasonic testing can lead to some defects being missed, resulting in low detection accuracy. Thus, a non-destructive testing technology is needed to improve the accuracy of the test results. Summary of the Invention

[0004] The purpose of this invention is to provide a non-destructive testing method and system for PE pipe hot-melt joints based on microwave imaging, which can improve the accuracy of the test results.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] A non-destructive testing method for PE pipe thermofusion joints based on microwave imaging includes:

[0007] Multiple microwave signals of various frequencies are emitted to each test point of the PE tube, and the echo signals reflected back from each test point are received; the echo signals include the time domain signal and the frequency domain signal corresponding to each frequency microwave signal.

[0008] The corrected echo signal of each test point is obtained by removing the frequency domain signal that is greater than the microwave characteristic response value of the base material from the echo signal reflected back from each test point.

[0009] The minimum value among the maxima of the microwave signal at each frequency in the corrected echo signal of each test point is taken as the multi-frequency microwave characteristic response value corresponding to each test point.

[0010] The abnormal region of the PE tube is determined based on the multi-frequency microwave characteristic response value and threshold range corresponding to each test point.

[0011] Optionally, multiple microwave signals of various frequencies are transmitted to each test point on the PE tube, and the echo signals reflected back from each test point are received, specifically including:

[0012] For any one of the test points in the PE pipe, a multi-frequency microwave signal generator is used to simultaneously transmit microwave signals of multiple frequencies to the test point.

[0013] The echo signal is obtained by using a detector to receive the time-domain and frequency-domain signals corresponding to the microwave signals of each frequency reflected back from the point under test.

[0014] Optionally, the minimum value among the maxima of the microwave signal corresponding to each frequency in the corrected echo signal of each test point is taken as the multi-frequency microwave characteristic response value corresponding to each test point, specifically including:

[0015] For any one of the test points in the PE pipe, determine the maximum value of the frequency domain signal corresponding to each frequency of the microwave signal in the corrected echo signal of the test point.

[0016] With frequency as the horizontal axis and echo signal as the vertical axis, a characteristic curve is plotted based on the maximum value of the frequency domain signal corresponding to each frequency of the microwave signal in the corrected echo signal of the test point.

[0017] The minimum value in the characteristic curve is taken as the multi-frequency microwave characteristic response value corresponding to the test point.

[0018] Optionally, the process for determining the microwave characteristic response value of the parent material includes:

[0019] The minimum value among the maxima of the microwave signals at each frequency in the echo signal of the set measurement point of the base material is taken as the microwave characteristic response value of the base material.

[0020] A non-destructive testing system for PE pipe thermofusion joints based on microwave imaging, comprising:

[0021] The echo signal acquisition module is used to transmit microwave signals of multiple frequencies to each test point of the PE tube and receive the echo signals reflected back from each test point; the echo signals include time-domain signals and frequency-domain signals corresponding to the microwave signals of each frequency.

[0022] The correction module is used to remove frequency domain signals that are greater than the microwave characteristic response value of the base material from the echo signals reflected back from each test point to obtain the corrected echo signals of each test point.

[0023] The multi-frequency microwave characteristic response value determination module is used to take the minimum value of the maximum value of the frequency domain signal corresponding to the microwave signal of each frequency in the correction echo signal of each test point as the multi-frequency microwave characteristic response value corresponding to each test point.

[0024] The detection module is used to determine the abnormal area of ​​the PE tube based on the multi-frequency microwave characteristic response value and threshold range corresponding to each test point.

[0025] Optionally, the echo signal acquisition module specifically includes:

[0026] The transmitting unit is used to transmit microwave signals of multiple frequencies to any one of the test points in the PE tube simultaneously using a multi-frequency microwave signal generator.

[0027] The data acquisition unit is used to receive the time-domain and frequency-domain signals corresponding to the microwave signals of each frequency reflected back from the point under test using a detector, and to obtain the echo signal.

[0028] Optionally, the multi-frequency microwave characteristic response value determination module specifically includes:

[0029] The maximum value determination unit is used to determine the maximum value of the frequency domain signal corresponding to each frequency of the microwave signal in the corrected echo signal of any one of the test points of the PE pipe.

[0030] The characteristic curve plotting unit is used to plot a characteristic curve with frequency as the horizontal axis and echo signal as the vertical axis, based on the maximum value of the frequency domain signal corresponding to each frequency of the microwave signal in the corrected echo signal of the test point.

[0031] A multi-frequency microwave characteristic response value determination unit is used to take the minimum value in the characteristic curve as the multi-frequency microwave characteristic response value corresponding to the test point.

[0032] Optionally, the microwave imaging-based non-destructive testing system for PE pipe thermofusion joints further includes:

[0033] The matrix microwave characteristic response value determination module is used to take the minimum value among the maxima of the frequency domain signal corresponding to the microwave signal at each frequency in the echo signal of the set measurement point of the matrix as the matrix microwave characteristic response value.

[0034] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0035] Multiple microwave signals of various frequencies are emitted to each test point of the PE pipe, and the echo signals reflected back from each test point are received. The echo signals include time-domain signals and frequency-domain signals corresponding to each frequency of microwave signal. The frequency-domain signals of the echo signals reflected back from each test point that are greater than the microwave characteristic response value of the base material are deleted to obtain the corrected echo signals of each test point. The minimum value among the maxima of the frequency-domain signals corresponding to each frequency of microwave signal in the corrected echo signals of each test point is taken as the multi-frequency microwave characteristic response value corresponding to each test point. Based on the multi-frequency microwave characteristic response value corresponding to each test point and the threshold range, the abnormal area of ​​the PE pipe is determined. This invention uses microwave signals to detect defects by detecting changes in the dielectric constant of the material, realizing non-destructive testing and improving the accuracy of the test results. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 A flowchart of a non-destructive testing method for PE pipe hot-melt joints based on microwave imaging provided in an embodiment of the present invention;

[0038] Figure 2 This is a graph of the echo signal in an embodiment of the present invention;

[0039] Figure 3 This is a feature curve diagram in an embodiment of the present invention;

[0040] Figure 4 This is a structural diagram of a PE pipe;

[0041] Figure 5 This is a diagram illustrating the working process of the microwave imaging-based non-destructive testing system for PE pipe hot-melt joints, provided in an embodiment of the present invention. Detailed Implementation

[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0044] Microwave testing works by detecting changes in the dielectric constant of materials to identify defects. During welding, any defect will cause changes in the material structure, even microscopic ones, leading to variations in the dielectric constant. Therefore, microwave testing is a novel and effective non-destructive testing method for PE pipe welds. Based on this, this invention provides a microwave imaging-based non-destructive testing method for PE pipe hot-melt joints using the principle of frequency sweeping microwave imaging. Figure 1 As shown, the method includes:

[0045] Step 101: Emits microwave signals of multiple frequencies to each test point on the PE tube and receives the echo signals reflected back from each test point; the echo signals include the time-domain signal and frequency-domain signal corresponding to each frequency of microwave signal. The transmitted signal is a set of microwave signals of different frequencies, which, after being absorbed by an object or undergoing an action, return a set of echo signals. The principle is as follows: A multi-frequency microwave signal generator emits continuously adjustable multi-frequency microwave signals into a PE tube. The non-uniform interface in the PE tube reflects the microwaves, and the reflected signals interfere with the emitted signals, forming standing waves. The detector receives the echo signals. The echo signal is a three-dimensional tensor, a collection of time-domain and frequency-domain signals corresponding to microwave signals of various frequencies. Based on the time-domain signal corresponding to each frequency, the characteristic values ​​of that frequency component can be obtained. Therefore, each signal can acquire a set of characteristic values ​​based on the changes in its frequency components. Each frequency of emitted signal corresponds to a set of echo time-domain signals that vary over time. Since the frequencies are multi-frequency, these are array time-domain signals based on frequency variations. The echo signal is a three-dimensional data set, with the X-axis representing time, the Y-axis representing frequency, and the Z-axis representing the echo response. The echo signal appears as a curve varying over time at different frequencies, as shown in the figure. Figure 2 As shown.

[0046] Step 102: Remove frequency domain signals from the echo signals reflected from each test point that are higher than the microwave characteristic response value St0 of the base material. Correct the echo signals to obtain the corrected echo signals for each test point. The correction process involves filtering out frequency domain signals higher than the microwave characteristic response value of the base material. The purpose is to remove the influence of weld beads inside and outside the weld on the test results. This eliminates the need for mechanical removal of weld beads, greatly simplifying the on-site testing process and making on-site testing easier.

[0047] Step 103: Take the minimum value of the maximum value of the frequency domain signal corresponding to each frequency of the microwave signal in the correction echo signal of each test point as the multi-frequency microwave characteristic response value St corresponding to each test point. It is not necessary to record the frequency of the echo signal. Since the material response is different for microwaves of different frequencies, the echo signal of any point is related to the frequency. In this case, only the multi-frequency microwave characteristic response value St is recorded.

[0048] Step 104: Based on the multi-frequency microwave characteristic response value and threshold range corresponding to each test point, determine the abnormal area of ​​the PE tube. The abnormal area is the defective area. The test point corresponding to the multi-frequency microwave characteristic response value that is not within the threshold range is the abnormal area.

[0049] In practical applications, multiple microwave signals of various frequencies are emitted to each test point on the PE tube, and the echo signals reflected back from each test point are received. Specifically, this includes:

[0050] For any one of the test points in the PE pipe, a multi-frequency microwave signal generator is used to simultaneously transmit microwave signals of multiple frequencies to the test point.

[0051] The echo signal is obtained by using a detector to receive the time-domain and frequency-domain signals corresponding to the microwave signals of various frequencies reflected back from the point under test. Assuming the axial direction of the PE pipe diameter is the Y-direction and the direction along the weld seam is the X-direction, as follows... Figure 4 As shown, the detector's operation is as follows: scanning along the X-axis and stepping along the Y-axis. The scanning speed and step size are selected based on the scanning probe and the microwave signal focusing size. Since most objects under test are non-uniform, meaning the material at different locations within the object responds differently to the microwave signal, the microwave signal detection path must cover the entire detection area during the detection process. The focusing size can be adjusted by adjusting the focuser. After focusing, it typically appears as a circular or elliptical spot, similar to a light spot. The scanning step size is determined based on the radius of the focused circle, ensuring the scanning process covers the entire area to be detected.

[0052] In practical applications, the minimum value among the maxima of the microwave signal at each frequency in the corrected echo signal of each test point is taken as the multi-frequency microwave characteristic response value corresponding to each test point, specifically including:

[0053] For any one of the test points in the PE pipe, determine the maximum value of the frequency domain signal corresponding to each frequency of the microwave signal in the corrected echo signal of the test point. Figure 2 Each curve in the diagram corresponds to a frequency domain signal of a microwave signal of a specific frequency. According to... Figure 2 The maximum value of the frequency domain signal (echo response) corresponding to each curve can be obtained (e.g. Figure 2 (S1, S2 and S3).

[0054] Plot a characteristic curve with frequency on the x-axis and echo signal on the y-axis, based on the maxima of the frequency domain signals corresponding to the microwave signals at each frequency in the corrected echo signal of the test point. For example... Figure 3 As shown, characteristic curves are obtained based on S1, S2, and S3 and their corresponding frequencies.

[0055] The minimum value S3 in the characteristic curve is taken as the multi-frequency microwave characteristic response value St corresponding to the point to be tested.

[0056] In practical applications, the process of determining the microwave characteristic response value of the base material includes:

[0057] The minimum value among the maxima of the microwave signals at each frequency in the echo signal of the set measurement point of the base material is taken as the microwave characteristic response value of the base material.

[0058] In practical applications, the abnormal regions of the PE tube are determined based on the multi-frequency microwave characteristic response values ​​and threshold ranges corresponding to each test point, specifically as follows:

[0059] A multi-frequency echo signal image is plotted based on the multi-frequency microwave characteristic response value St corresponding to the point and the coordinate value of the point. The image is a three-dimensional image, with the X and Y axes corresponding to the position coordinates and the Z axis corresponding to the multi-frequency microwave characteristic response value St, which can also be regarded as the depth position coordinate.

[0060] Based on the multi-frequency echo signal image, the region corresponding to the multi-frequency microwave characteristic response value St that is outside the threshold range can be intuitively selected as the abnormal region. For example, the multi-frequency echo signal image can be sliced ​​perpendicular to the Z-axis (the horizontal axis is the Y-axis of the multi-frequency echo signal image, and the vertical axis is the X-axis of the multi-frequency echo signal image). The abnormal region can be obtained based on the St value of the sliced ​​image. By comparing the multi-frequency microwave characteristic response value St of the abnormal region with that of the defect-free region, it can be concluded that there is a defect if it is outside the threshold range. Therefore, the welding abnormal region can be intuitively selected based on the multi-frequency echo signal image and the threshold range. The size of the threshold range is related to the base material, thickness, pipe diameter, etc., and can be determined by making standard samples.

[0061] The present invention also provides a microwave imaging-based non-destructive testing system for PE pipe thermofusion joints corresponding to the above method, comprising:

[0062] The echo signal acquisition module is used to transmit microwave signals of multiple frequencies to each test point of the PE tube and receive the echo signals reflected back from each test point; the echo signals include time-domain signals and frequency-domain signals corresponding to the microwave signals of each frequency.

[0063] The correction module is used to remove frequency domain signals that are greater than the microwave characteristic response value of the base material from the echo signals reflected back from each test point to obtain the corrected echo signal of each test point.

[0064] The multi-frequency microwave characteristic response value determination module is used to take the minimum value among the maxima of the frequency domain signal corresponding to each frequency of the microwave signal in the corrected echo signal of each test point as the multi-frequency microwave characteristic response value corresponding to each test point.

[0065] The detection module is used to determine the abnormal areas of the PE pipe based on the multi-frequency microwave characteristic response values ​​and threshold ranges corresponding to each test point. Based on the threshold range settings, defects such as inclusions, voids, delamination, and cold welding can be identified. The calibration module, the multi-frequency microwave characteristic response value determination module, and the detection module constitute the data processing and analysis module.

[0066] As an optional implementation, the echo signal acquisition module specifically includes:

[0067] The transmitting unit is used to transmit microwave signals of multiple frequencies to any one of the test points in the PE pipe simultaneously using a multi-frequency microwave signal generator. The multi-frequency microwave signal generator must be able to transmit continuous multi-frequency microwave signals, and the resolution of the microwave signals is related to the detection accuracy.

[0068] The data acquisition unit is used to receive the time-domain and frequency-domain signals corresponding to the microwave signals of various frequencies reflected back from the point under test using a detector, thereby obtaining the echo signals. It can be a vector network analyzer used to measure the microwave signals.

[0069] As an optional implementation, it also includes a microwave signal focusing module and a scanning movement module. The microwave signal focusing module focuses the microwave signal and slices the sample along the Z-axis in space, providing depth resolution and layered imaging of the slices along the depth direction. The scanning movement module needs to be able to determine the stepping and scanning speed based on the size of the focused signal, and achieve full coverage of the detection area; given that the pipe is generally circular, the data acquisition unit needs to meet the characteristics of circular motion. The data acquisition unit operates according to the stepping and scanning speed determined by the scanning movement module.

[0070] As an optional implementation, the multi-frequency microwave characteristic response value determination module specifically includes:

[0071] The maximum value determination unit is used to determine the maximum value of the frequency domain signal corresponding to each frequency of the microwave signal in the corrected echo signal of any one of the test points of the PE tube.

[0072] The characteristic curve plotting unit is used to plot characteristic curves with frequency as the horizontal axis and echo signal as the vertical axis, based on the maximum values ​​of the frequency domain signals corresponding to the microwave signals of each frequency in the corrected echo signal of the test point.

[0073] A multi-frequency microwave characteristic response value determination unit is used to take the minimum value in the characteristic curve as the multi-frequency microwave characteristic response value corresponding to the test point.

[0074] As an optional implementation, the microwave imaging-based non-destructive testing system for PE pipe thermofusion joints further includes:

[0075] The matrix microwave characteristic response value determination module is used to take the minimum value among the maxima of the microwave signals corresponding to each frequency in the echo signal of the matrix set measurement point as the matrix microwave characteristic response value.

[0076] The working process of the system provided in this embodiment of the invention is as follows: Figure 5 As shown, the scanning and moving module sends a scanning and moving command to itself. The scanning and moving module drives the probe of the multi-frequency microwave signal generator to move in steps according to the set moving distance. After the multi-frequency microwave signal generator moves into position, it transmits a signal and starts scanning synchronously. The microwave signal focusing module focuses the transmitted signal onto the sample (PE tube). The data acquisition signal collects the echo signal reflected by the sample and sends the echo signal to the data processing and analysis module. At the same time, the scanning and moving module sends the position information to the data processing and analysis module. The data processing and analysis module processes the collected position information and echo information to generate a three-dimensional image for non-destructive testing. Every time the scanning and moving module changes position, it first records the position, transmits a signal, receives the echo signal, analyzes and records the signal, and then moves the position again... and so on.

[0077] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to the method section.

[0078] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A non-destructive testing method for PE pipe thermofusion joints based on microwave imaging, characterized in that, include: Multiple microwave signals of various frequencies are emitted to each test point of the PE tube, and the echo signals reflected back from each test point are received; the echo signals include the time domain signal and the frequency domain signal corresponding to each frequency microwave signal. The corrected echo signal of each test point is obtained by removing the frequency domain signal that is greater than the microwave characteristic response value of the base material from the echo signal reflected back from each test point. The minimum value among the maxima of the microwave signal at each frequency in the corrected echo signal of each test point is taken as the multi-frequency microwave characteristic response value corresponding to each test point. The abnormal region of the PE tube is determined based on the multi-frequency microwave characteristic response value and threshold range corresponding to each test point.

2. The non-destructive testing method for PE pipe thermofusion joints based on microwave imaging according to claim 1, characterized in that, Multiple microwave signals of various frequencies are emitted to each test point on the PE tube, and the echo signals reflected back from each test point are received. Specifically, these include: For any one of the test points in the PE pipe, a multi-frequency microwave signal generator is used to simultaneously transmit microwave signals of multiple frequencies to the test point. The echo signal is obtained by using a detector to receive the time-domain and frequency-domain signals corresponding to the microwave signals of each frequency reflected back from the point under test.

3. The non-destructive testing method for PE pipe thermofusion joints based on microwave imaging according to claim 1, characterized in that, The minimum value among the maxima of the microwave signal at each frequency in the corrected echo signal of each test point is taken as the multi-frequency microwave characteristic response value corresponding to each test point, specifically including: For any one of the test points in the PE pipe, determine the maximum value of the frequency domain signal corresponding to each frequency of the microwave signal in the corrected echo signal of the test point. With frequency as the horizontal axis and echo signal as the vertical axis, a characteristic curve is plotted based on the maximum value of the frequency domain signal corresponding to each frequency of the microwave signal in the corrected echo signal of the test point. The minimum value in the characteristic curve is taken as the multi-frequency microwave characteristic response value corresponding to the test point.

4. The non-destructive testing method for PE pipe thermofusion joints based on microwave imaging according to claim 1, characterized in that, The process for determining the microwave characteristic response value of the parent material includes: The minimum value among the maxima of the microwave signals at each frequency in the echo signal of the set measurement point of the base material is taken as the microwave characteristic response value of the base material.

5. A non-destructive testing system for PE pipe thermofusion joints based on microwave imaging, characterized in that, include: The echo signal acquisition module is used to transmit microwave signals of multiple frequencies to each test point of the PE tube and receive the echo signals reflected back from each test point; the echo signals include time-domain signals and frequency-domain signals corresponding to the microwave signals of each frequency. The correction module is used to remove frequency domain signals that are greater than the microwave characteristic response value of the base material from the echo signals reflected back from each test point to obtain the corrected echo signals of each test point. The multi-frequency microwave characteristic response value determination module is used to take the minimum value of the maximum value of the frequency domain signal corresponding to the microwave signal of each frequency in the correction echo signal of each test point as the multi-frequency microwave characteristic response value corresponding to each test point. The detection module is used to determine the abnormal area of ​​the PE tube based on the multi-frequency microwave characteristic response value and threshold range corresponding to each test point.

6. The non-destructive testing system for PE pipe thermofusion joints based on microwave imaging according to claim 5, characterized in that, The echo signal acquisition module specifically includes: The transmitting unit is used to transmit microwave signals of multiple frequencies to any one of the test points in the PE tube simultaneously using a multi-frequency microwave signal generator. The data acquisition unit is used to receive the time-domain and frequency-domain signals corresponding to the microwave signals of each frequency reflected back from the point under test using a detector, and to obtain the echo signal.

7. The non-destructive testing system for PE pipe thermofusion joints based on microwave imaging according to claim 5, characterized in that, The multi-frequency microwave characteristic response value determination module specifically includes: The maximum value determination unit is used to determine the maximum value of the frequency domain signal corresponding to each frequency of the microwave signal in the corrected echo signal of any one of the test points of the PE pipe. The characteristic curve plotting unit is used to plot a characteristic curve with frequency as the horizontal axis and echo signal as the vertical axis, based on the maximum value of the frequency domain signal corresponding to each frequency of the microwave signal in the corrected echo signal of the test point. A multi-frequency microwave characteristic response value determination unit is used to take the minimum value in the characteristic curve as the multi-frequency microwave characteristic response value corresponding to the test point.

8. The non-destructive testing system for PE pipe thermofusion joints based on microwave imaging according to claim 5, characterized in that, Also includes: The matrix microwave characteristic response value determination module is used to take the minimum value among the maxima of the microwave signals corresponding to each frequency in the echo signal of the matrix set measurement point as the matrix microwave characteristic response value.

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