Welded joint ultrasonic phased array detection method and system

Abstract

The invention discloses an ultrasonic phased array detection method and system for a welded joint, and relates to the field of metal welding nondestructive detection.The ultrasonic phased array detection method for the welded joint comprises the steps that a C scanning image of the welded joint is obtained; performing median filtering processing on the C scanning image to remove noise and reserve defect edge features; segmenting the filtered C scanning image by using a K-means clustering algorithm, and separating a defect echo region from a background; and based on the segmentation result, performing three-dimensional reconstruction on defect echoes by adopting a moving cube method, generating a three-dimensional visual image of the defects, and representing the spatial form of the inter-layer incomplete fusion defects of the welding joint. According to the method, the problems of defect and structure echo signal superposition and difficult identification are effectively solved through a finite element simulation method. A proper threshold value is selected through wavelet denoising, signals are decomposed into signals of different scales, then the signals of the needed scale are selected for reconstruction to filter noise, and the quality of an identified image is improved.

Description

Technical Field

[0001] The invention relates to the technical field of nondestructive testing of metal welding, and in particular to a method and system for ultrasonic phased array testing of welded joints. Background Art

[0002] Welded joints are a common connection method in modern industry. Currently, most metal steel plate connections are completed by manual MIG welding or TIG welding. Since welding is mainly done manually, the welding quality is closely related to the operator's technical level. It is very easy to produce unstable welding parameters due to improper operation and poor weld formation caused by insufficient heat input, resulting in welding defects such as tungsten inclusions, pores, lack of fusion and incomplete penetration, which greatly increases the probability of accidents caused by failure of welded joints during service. Therefore, for the quality of stainless steel welded joints, it is necessary not only to ensure the technical level of welders and strictly implement welding procedures at the source, but also to conduct post-weld inspection and evaluation of the quality of welded joints, especially the internal quality, so as to ensure the reliability of the shelf structure.

[0003] At present, the quality assessment of welded joints mainly adopts destructive testing and non-destructive testing methods. Destructive testing requires destructive processing of welded parts and preparation of samples for metallographic analysis of welded joints, or performance tests such as tensile, bending, impact and fatigue. This not only causes a large waste of materials, but also makes it impossible to perform welded joint performance testing on in-service welded structures. Non-destructive testing mainly uses radiographic testing (RT), ultrasonic testing (UT), magnetic particle testing (MT), magnetic memory testing (MMT), penetration testing (PT) and other methods to inspect the quality of welded parts. Among them, ultrasonic testing is a conventional A-scan test on the surface of the workpiece by the staff holding an ultrasonic probe. The judgment of the defect signal characteristics of the plug weld joint depends entirely on the personal experience of the inspector, which is easy to cause false detection and missed detection of defects. Compared with conventional ultrasonic testing methods, phased array ultrasonic testing technology is based on the Huygens-Fresnel principle and the interference and superposition theory of waves. It uses modern electronic and computer technology to control the array elements in the ultrasonic transducer, and transmits and receives ultrasonic waves according to the pre-set delay law, thereby dynamically controlling the deflection and focusing of the ultrasonic beam within a certain spatial range, and realizing an ultrasonic testing method of electronic focusing and scanning. Phased array ultrasound has the advantages of high sensitivity, wide detection range, and the ability to quickly form intuitive detection images. When ultrasonic testing of welded joints, both conventional ultrasound and phased array ultrasound are based on the reflection, refraction, transmission, and attenuation characteristics of sound waves during propagation in the material. Therefore, how to efficiently and accurately detect and monitor the quality of welded joints has become an important issue. Summary of the invention

[0004] In view of the above problems existing in the prior art, the present invention is proposed.

[0005] Therefore, the problem to be solved by the present invention is how to efficiently and accurately detect and monitor the quality of welding joints.

[0006] To solve the above technical problems, in a first aspect, the present invention provides the following technical solutions: a method for ultrasonic phased array detection of welded joints, comprising: obtaining a C-scan image of the welded joint; performing median filtering on the C-scan image to remove noise and retain defect edge features; using a K-means clustering algorithm to segment the filtered C-scan image to separate the defect echo area from the background; based on the segmentation result, using a moving cube method to perform three-dimensional reconstruction of the defect echo to generate a three-dimensional visualization image of the defect, thereby characterizing the spatial morphology of the interlayer unfused defect in the welded joint.

[0007] As a preferred solution of the ultrasonic phased array detection method for welded joints described in the present invention, before performing the C-scan image processing, a region of interest of the welded joint is selected to improve the resolution of defect detection and reduce the amount of calculation; wherein the region of interest includes an effective connection area, an incomplete penetration area, an interlayer unfused defect area, and an unfused area at the edge of the groove.

[0008] As a preferred solution of the ultrasonic phased array detection method for welded joints of the present invention, wherein: adaptive median filtering is performed on the region of interest to enhance the edge features of high-density noise regions and improve the accuracy of defect detection.

[0009] As a preferred solution of the ultrasonic phased array detection method for welded joints of the present invention, the number of clusters of the K-means clustering algorithm is adaptively set according to the structural characteristics of the welded joint to ensure the accuracy of image segmentation.

[0010] As a preferred solution of the ultrasonic phased array detection method for welded joints described in the present invention, the segmented image after K-means clustering is morphologically processed to remove small noise areas and enhance the connectivity of defect edges to improve the quality of three-dimensional reconstruction.

[0011] As a preferred solution of the ultrasonic phased array detection method for welded joints described in the present invention, a dynamic threshold is used in the three-dimensional reconstruction process of the moving cube method to adapt to defects of different sizes and further improve the accuracy of spatial morphology reconstruction.

[0012] As a preferred solution of the ultrasonic phased array detection method for welded joints described in the present invention, the three-dimensional reconstructed defect image is rendered in pseudo color and its transparency is adjusted to intuitively display the depth, size and shape of the defect.

[0013] As a preferred solution of the ultrasonic phased array detection method for welded joints described in the present invention, the defect degree is quantified by comparing the three-dimensional reconstructed image with a preset standard model to evaluate the connection quality of the welded joint.

[0014] As a preferred solution of the ultrasonic phased array detection method for welded joints described in the present invention, a background subtraction algorithm is used to process the ultrasonic fan-scan image of the welded joint to separate the joint interface echo and the near-surface defect echo to improve the accuracy of defect identification.

[0015] On the other hand, the present invention also provides an ultrasonic phased array detection system for welding joints, which is used to implement the above-mentioned ultrasonic phased array detection method. The system includes a walking mechanism, which includes a track and a screw rod, wherein the screw rod is arranged in parallel above the track and the end of the screw rod is connected to the output end of the motor; a detection module, including a detection probe and a moving block, wherein the detection probe is fixedly arranged on the moving block, and the moving block is threadedly matched with the screw rod and slidingly matched with the track; a fixing assembly, which includes a fixed block and a binding chain, wherein the fixed block is fixedly connected to the end of the track, one end of the binding chain is hinged to the fixed block, and the other end is detachably connected to the fixed block; walking wheels are provided on both sides of the fixed block and the binding chain.

[0016] The beneficial effects of the present invention are as follows: the present invention effectively solves the problem of defect and structure echo signal superposition and difficulty in identification through the finite element simulation method. The signal is decomposed into signals of different scales by selecting a suitable threshold through wavelet denoising, and then the noise is filtered out by selecting the required scale signal for reconstruction to improve the quality of the recognition image. The device has a high degree of automation, high detection accuracy, and the results are intuitive and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 This is the principle diagram of defect phased array ultrasonic sector scanning detection.

[0019] Figure 2 This is a flowchart of the ultrasonic phased array detection method for welded joints.

[0020] Figure 3 This is the waveform diagram of ultrasonic phased array detection of welding joints.

[0021] Figure 4 This is the image recognition diagram of ultrasonic phased array inspection of welding joints.

[0022] Figure 5 This is the structural diagram of the ultrasonic phased array detection system for welded joints.

[0023] Figure 6 This is a schematic diagram of the structure of the ultrasonic phased array detection device for welding joints. DETAILED DESCRIPTION

[0024] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings.

[0025] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0026] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor is it an embodiment that is mutually exclusive with other embodiments, either individually or selectively.

[0027] Example 1

[0028] Reference Figure 1 to Figure 4 , which is the first embodiment of the present invention, and this embodiment provides an ultrasonic phased array detection method for welding joints, the ultrasonic phased array detection method for welding joints includes.

[0029] S1: Get a C-scan image of the weld joint.

[0030] Specifically, selecting a region of interest (ROI) can focus on the inspection area and reduce the complexity of calculation and image processing. The detection accuracy and calculation efficiency of defects can be improved by focusing on the area. Especially in the case of complex structures or large areas of welded joints, accurately defining the ROI can effectively reduce the range of data that needs to be processed, thereby improving the algorithm processing speed and real-time performance.

[0031] Preferably, the phased array ultrasonic testing method can adopt longitudinal wave or shear wave mode.

[0032] When using the longitudinal wave detection mode, the ultrasonic probe and the workpiece can be directly or through a 0° wedge coupling contact. Direct coupling detection is mainly used for thicker workpieces and deep defects to shorten the sound path and improve the detection sensitivity of deep defects.

[0033] 0° wedge coupling detection can avoid the near-field detection blind area and is more suitable for defect detection in the near-surface area of ​​thin plates or thick parts.

[0034] The longitudinal wave detection mode usually uses the sound wave to be incident perpendicular to the workpiece surface, which is suitable for defect detection parallel to the workpiece surface.

[0035] The shear wave detection mode uses the same probe as the longitudinal wave mode, and is realized by converting the acoustic wave waveform generated by the inclined wedge and the workpiece coupling interface. Since the shear wave is incident on the workpiece at a specific angle, it is mainly used to detect defects that are perpendicular to the workpiece surface or at a certain angle. The phased array parameters are shown in the following table:

[0036]

[0037] S2: Perform median filtering on the C-scan image to remove noise and retain defect edge features.

[0038] Specifically, the adaptive median filter can dynamically adjust the filter parameters according to the local characteristics of the signal, processing the noise while retaining the edge features. This method is particularly effective for the welding joint area, which usually has high noise and complex echo characteristics. Its introduction ensures that the clarity of the defect edge can be maintained even in a complex noise environment, avoiding the loss of defect signals due to excessive denoising.

[0039] S3: Use K-means clustering algorithm to segment the filtered C-scan image and separate the defect echo area from the background.

[0040] Specifically, the number of clusters of the K-means clustering algorithm is adaptively set according to the structural characteristics of the weld joint to ensure the accuracy of image segmentation.

[0041] It should be noted that for the defects of incomplete penetration and lack of fusion between layers, their projected area in the direction parallel to the workpiece surface will directly affect the quality of the joint;

[0042] For the unfused defect at the groove edge, its equivalent length distributed along the circumference of the joint is an important quality parameter.

[0043] Specifically, for plug welds without defects or with incomplete penetration defects, the area of ​​the fusion zone needs to be calculated.

[0044] For plug welds containing interlayer lack of fusion defects, the defect area needs to be calculated.

[0045] For plug weld joints with incomplete fusion defects at the groove edge, it is necessary to calculate the equivalent length of the defect in the circumference direction of the joint.

[0046] The radiated acoustic field inside the welded joint during phased array ultrasonic testing is visualized and simulated. The echo characteristics of the effective connection area, incomplete penetration area, interlayer unfused defect area and unfused area at the edge of the groove of the plug welded joint are analyzed. The selection method of the echo characteristic value of each area and its influence on the detection accuracy are studied.

[0047] The echo characteristic curve of the welding joint connection area and defects can reflect the size and location information of the defects; when the height of the interlayer unfused defect from the detection surface is less than 1.2mm, the defect echo will interfere with the echo of the workpiece surface, resulting in that its characteristics cannot be effectively extracted;

[0048] The characteristic curve of the partially reflected incomplete penetration area shows a step-down characteristic;

[0049] When the oblique incidence method is used to detect the unfused defects on the groove side edge, the defect features are obvious, there is no strong structural echo influence, and it is easy to identify.

[0050] The characteristic curve is obtained by taking the amplitude of the first echo of ultrasonic A wave as the characteristic value, and the -6dB method is used to analyze the characteristic curve, analyze the acoustic wave characteristics of the fusion zone and defects of the arc plug welding joint, and quantitatively evaluate the connection status and defects of the arc plug welding joint.

[0051] For welded joints with interlayer unfusion defects, the background subtraction algorithm is used to process the ultrasonic sector scan image acoustic wave signal, which can effectively separate the near-surface defect echo from the joint interface echo.

[0052] The sector scan image is preprocessed using delay correction and a linear interpolation algorithm with an interpolation factor of 5, which can effectively control the time delay between the foreground image and the background image within 2ns, greatly reducing the impact of the residual interface echo on the defect echo and improving the detection accuracy.

[0053] The noise signal in the ultrasonic echo characteristic curve is a randomly distributed non-stationary signal. Compared with the traditional filtering method, wavelet denoising has multi-scale resolution, so it has a better filtering effect on this signal. The basic principle of wavelet filtering is to decompose the signal into signals of different scales by performing wavelet transform on the signal, and then filter out the noise by selecting the required scale signal for reconstruction.

[0054] Since the edge characteristic curves of the plug welding joint and defects are discrete data, discrete wavelet transform is used to decompose and reconstruct the signal to improve the accuracy of image recognition. After all positions are detected, the detection data is stored and the next welding joint is detected.

[0055] S4: Based on the segmentation results, the moving cube method is used to reconstruct the defect echo in three dimensions to generate a three-dimensional visualization image of the defect and characterize the spatial morphology of the interlayer unfusion defect in the weld joint.

[0056] The fixed threshold moving cube method can clearly identify the three-dimensional morphology of volume defects. It can better identify volume defects with small aspect ratios, but it is basically difficult to identify narrow and long defects with large aspect ratios.

[0057] Based on reasonable image filtering and segmentation algorithms, the imaging results of volume defects based on C-scan image segmentation moving cube method are used to form ultrasonic three-dimensional visualization images that can accurately express the morphology of volume defects. After all positions are detected and quality evaluated, the detection data is stored and the next welding joint is tested.

[0058] Example 2

[0059] Reference Figure 5 , which is the second embodiment of the present invention, and is based on the previous embodiment. This embodiment provides a welding joint ultrasonic phased array detection system, the system includes a control computer, a phased array ultrasonic transmitting / receiving module, a motion control module, a mechanical scanning mechanism, etc. The control computer is mainly responsible for human-machine interaction, control of the ultrasonic detection module and reception of feedback signals, and communication and coordination control of the motion control module;

[0060] The main functions of the phased array ultrasonic detection module are the excitation, reception, parallel processing of ultrasonic signals, and the storage and upload of signal data. It can communicate with the control computer via the RJ45 network port using the TCP / IP protocol. A 32-element linear phased array probe is selected, with an element spacing of 0.3mm and a center frequency of 10MHz. In order to avoid the near field area, the phased array probe is equipped with 0° and 36° organic glass wedges;

[0061] The motion control module includes a stepper motor control card and a stepper motor driver, wherein the stepper motor control card is an I / O control signal transmitting module, the control computer is connected to it through a USB interface, and transmits control pulses to the stepper motor driver to drive the stepper motor.

[0062] In addition, the human-computer interaction software was developed using the MFC framework in the Visual Studio 2010 platform. The software structure included: ultrasound parameter and mechanical scanning parameter setting module, ultrasound excitation and reception module, motion control module, signal processing and image display module, and data storage module.

[0063] The ultrasonic parameter setting module can automatically calculate the delay of the acoustic beam excitation by setting the sample plate thickness, sound velocity, focal depth and other information, and place the delay data into the phased array detection system;

[0064] The ultrasonic excitation and reception module controls the excitation and reception of ultrasonic signals;

[0065] The motion control module performs mechanical scanning motion control according to the set scanning area, step angle and step speed;

[0066] The signal processing and image display module performs data processing on the collected ultrasonic A echo signal and performs image processing of A scan, S scan and C scan.

[0067] Example 3

[0068] Reference Figure 6 , which is the third embodiment of the present invention, and is based on the first two embodiments. This embodiment provides a welding joint ultrasonic phased array detection system, which can implement the above ultrasonic phased array detection method. The system includes a walking mechanism 100, a detection module 200, and a fixing component 300.

[0069] Specifically, the walking mechanism 100 includes a track 101 and a screw rod 102. The screw rod 102 is arranged above the track 101 in parallel and has a certain distance from the track 101. The two ends of the screw rod 102 are flush with the two ends of the track 101. The output end of the motor 103 is connected to the end of the screw rod 102, and is used to drive the screw rod 102 to rotate.

[0070] The detection module 200 includes a detection probe 201 and a moving block 202. The detection probe 201 is an ultrasonic probe, and the moving block 202 is passed through and threadedly matched with the screw rod 102. When the motor 103 drives the screw rod 102 to rotate, the moving block 202 will move along the track 101, and the detection probe 201 thereon will also detect the welding joint.

[0071] The fixing assembly 300 includes a fixing block 301 and a tying chain 302. There are two fixing blocks 301, which are fixed at both ends of the track 101. The tying chain 302 is formed by connecting blocks in series, and each connecting block and the fixing block 301 is provided with a running wheel 303. In this way, the detection probe 201 can detect not only along the axial direction of the pipeline but also along its circumferential direction.

[0072] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for ultrasonic phased array detection of welded joints, characterized in that: include, Obtain C-scan images of welded joints; Performing median filtering on the C-scan image to remove noise and retain defect edge features; The K-means clustering algorithm is used to segment the filtered C-scan image to separate the defect echo area from the background; Based on the segmentation results, the moving cube method is used to reconstruct the defect echo in three dimensions to generate a three-dimensional visualization image of the defect and characterize the spatial morphology of the interlayer lack of fusion defect in the weld joint.

2. The ultrasonic phased array detection method for welded joints according to claim 1, characterized in that: Before performing the C-scan image processing, an area of ​​interest of the weld joint is selected to improve the resolution of defect detection and reduce the amount of calculation; wherein the area of ​​interest includes an effective connection area, an incomplete penetration area, an interlayer unfused defect area, and an unfused area at the groove edge.

3. The ultrasonic phased array detection method for welded joints according to claim 2, characterized in that: Adaptive median filtering is performed on the region of interest to enhance edge features of high-density noise regions and improve the accuracy of defect detection.

4. The ultrasonic phased array detection method for welded joints according to claim 3, characterized in that: The number of clusters of the K-means clustering algorithm is adaptively set according to the structural characteristics of the weld joint to ensure the accuracy of image segmentation.

5. The ultrasonic phased array detection method for welded joints according to claim 4, characterized in that: Morphological processing is performed on the segmented image after K-means clustering to remove small noise areas and enhance the connectivity of defect edges to improve the quality of 3D reconstruction.

6. The ultrasonic phased array detection method for welded joints according to claim 5, characterized in that: The three-dimensional reconstruction process of the marching cube method adopts a dynamic threshold to adapt to defects of different sizes and further improve the accuracy of spatial morphology reconstruction.

7. The ultrasonic phased array detection method for welded joints according to claim 6, characterized in that: The 3D reconstructed defect image is rendered in pseudo color and its transparency is adjusted to intuitively display the depth, size and shape of the defect.

8. The ultrasonic phased array detection method for welded joints according to claim 7, characterized in that: By comparing the 3D reconstructed image with the preset standard model, the degree of defects can be quantified to evaluate the connection quality of the welded joint.

9. The ultrasonic phased array detection method for welded joints according to claim 8, characterized in that: The background subtraction algorithm is used to process the ultrasonic sector scan image of the welded joint to separate the joint interface echo and the near-surface defect echo to improve the accuracy of defect identification.

10. An ultrasonic phased array detection system for welded joints, characterized in that: Used to implement the ultrasonic phased array detection method according to any one of claims 1 to 9, the ultrasonic phased array detection system comprises: A walking mechanism (100) comprises a track (101) and a screw rod (102), wherein the screw rod (102) is arranged above the track (101) in parallel and an end of the screw rod (102) is connected to an output end of a motor (103); The detection module (200) comprises a detection probe (201) and a moving block (202), wherein the detection probe (201) is fixedly arranged on the moving block (202), and the moving block (202) is threadedly matched with the screw rod (102) and slidably matched with the track (101); A fixing assembly (300) comprises a fixing block (301) and a tying chain (302), wherein the fixing block (301) is fixedly connected to the end of the track (101), one end of the tying chain (302) is hinged to the fixing block (301), and the other end is detachably connected to the fixing block (301); both sides of the fixing block (301) and the tying chain (302) are provided with running wheels (303).

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