A method for measuring the height of internal defects of a fillet weld

Abstract

The present application relates to a kind of measurement methods of the height of internal defect of fillet weld, belong to nondestructive testing field, install two parallel probes on wedge, and the two probes are respectively connected with the transmitting port and receiving port of A-mode ultrasonic detector using signal line;A-mode ultrasonic detector is set to depth display, calibrate instrument;Using A-mode ultrasonic detector to detect workpiece, find the wave peak position of front signal in the obtained defect echo signal, that is, determine the diffraction signal of defect upper edge;Similarly, find the trough position of trailing signal in defect echo signal, that is, determine the diffraction signal of defect lower edge;Read the wave front depth value m of defect upper edge diffraction signal, the depth value n of the first wave peak of defect upper edge diffraction signal, the depth value p of the first wave peak of defect lower edge diffraction signal, and calculate the defect height;The present application aims to solve the existing TOFD detection technology suitable for flat butt weld detection, but cannot be used for fillet weld detection.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of non-destructive testing, in particular to a method for measuring the height of an internal defect of an angle weld. BACKGROUND

[0002] An angle weld refers to a weld along the intersection line of two orthogonal or nearly orthogonal parts. The angle weld is a common welding structure, which generally has concentrated stress and thus requires greater carrying capacity, and the welding quality must be ensured. The determination of the defect height in the welding effect evaluation is particularly important for safety performance evaluation.

[0003] At present, the relatively mature method for measuring the height of a defect in the field of non-destructive testing is the TOFD detection technology. The TOFD detection technology is a method for realizing defect detection and defect quantification by obtaining a diffraction signal from an internal defect (structure) of a workpiece to be detected. The TOFD detection technology has the advantages of convenient operation of the detection equipment, convenient detection of plate butt welds, and high precision of defect quantification. However, the TOFD detection technology has limitations, such as difficult image recognition and interpretation, the need for rich experience for data analysis, difficulty in detecting workpieces with complex combined shapes, and inability to detect angle welds and measure the height of internal defects of angle welds.

[0004] In the prior art, the Chinese patent application with the application number 201611200865.8 discloses an ultrasonic detection method for an incomplete weld. The target object of the method is an incomplete weld, i.e., a non-full penetration welding weld. The method is an improvement based on the TOFD detection, using a TOFD detection device, a TOFD detection probe, and a TOFD detection probe arrangement method, and adding upper wave climbing detection and root transverse wave detection. The TOFD scans the middle part, the transverse wave scans the root, and the wave climbing scans the surface, solving the problem of existing TOFD detection technology that there are upper and lower surface blind areas in the detection process and that the detection cannot be fully covered. However, the existing TOFD detection technology still cannot realize the detection of angle welds, and there is no technical solution for measuring the height of an angle weld. The existing TOFD detection is only suitable for convenient detection of plate butt welds, but it is difficult to detect workpieces with complex combined shapes. Therefore, it is impossible to realize the detection of angle welds by using the existing TOFD detection. The full-focus phased array technology in the field can be used to measure the angle weld, but the process is too complex, and the measurement precision is about 1 mm. SUMMARY

[0005] The present application provides a kind of fillet weld internal defect self height measurement method for the above problems existing in prior art, and its technical problems are as follows: the existing TOFD detection technology is suitable for plate butt weld detection, but it is difficult to detect complex combined shape workpieces, and it cannot be applied to the detection of fillet weld, and the method steps are simple, and the operability is strong.

[0006] The technical scheme for solving the above technical problems is as follows: a kind of fillet weld internal defect self height measurement method, characterized in that, comprising the following steps:

[0007] Two parallel probes are installed on the wedge, and the two probes are connected to the transmitting (T) port and receiving (R) port of the A-mode ultrasonic detector respectively;

[0008] Among them, the two probes are longitudinal wave straight probes, which can cover a larger detection area in detection, especially can reduce the surface blind area, by using the same size of probe wafer; The two probes are connected in parallel because the probe can only be placed on the same side of the weld to achieve the detection of the fillet weld; In detection, the angle and focusing position of the main sound beam are reasonably determined according to the thickness of the workpiece to be detected, and different depths of focus are realized by selecting different angles and selecting probe wedges;

[0009] The A-mode ultrasonic detector is set to depth display, and the instrument is calibrated;

[0010] The A-mode ultrasonic detector is used to detect the workpiece, and the peak position of the front signal in the obtained defect echo signal is found, that is, the diffraction signal of the upper edge of the defect is determined, and the trough position of the rear signal in the defect echo signal is also found, that is, the diffraction signal of the lower edge of the defect is determined;

[0011] The wavefront depth value m of the defect upper edge diffraction signal, the depth value n of the first peak of the defect upper edge diffraction signal, and the depth value p of the first peak of the defect lower edge diffraction signal are read out;

[0012] Then the wavelength = 4*|m-n|,

[0013] The defect self height h =|n-p|-2*|m-n| is calculated.

[0014] Further, the wedge is made of organic glass wedge.

[0015] Further, the installation angle of the two probes in the wedge is set to a preset angle according to the thickness of the workpiece to be detected, and the set angle and the installation angle of the probe are determined according to the workpiece to be detected and the reference TOFD detection standard. Further, the angle range is 45°-70°.

[0016] Further, a medium is provided between the two probes to avoid the formation of echo in the wedge.

[0017] Further, the working mode of the A-type ultrasonic detector is set as a transmitting-receiving mode, the frequency band width is selected as a narrow band, the detection mode is selected as a radio frequency mode, and the probe is adjusted as a longitudinal wave oblique probe.

[0018] Further, during the calibration of the instrument, the probe incident point, the sound speed and the probe refraction angle are measured by using the CSK-1A test block: the probe incident point and the sound speed are measured at the R50 and R100 arc positions at the front end of the CSK-1A test block, and the probe refraction angle is measured at the 50mm hole position at the rear end of the CSK-1A test block.

[0019] Further, the device delay is set as the ratio of the double of the distance from the probe incident point to the center line of the fillet weld and the sound speed of the material, and the detection range is set as the full thickness detection time of the workpiece minus the delay time.

[0020] Further, the detection sensitivity is measured before the workpiece is detected, and the determination of the measurement sensitivity is performed by using the CSK-IIA series test block.

[0021] Further, the transverse hole in the CSK-IIA series test block which is closest to the defect depth is selected according to the depth of the defect in the fillet weld, the highest reflection echo of the transverse hole is found, the gain is adjusted to 6dB to 10dB at the height of 80% of the full screen amplitude of the device.

[0022] The method has the advantages that the longitudinal wave straight probes are connected in parallel, different focusing depths are realized by selecting different probe wedge blocks, the probes are connected in parallel for realizing the single-side detection of the fillet weld (the two probes can only be placed on the same side of the fillet weld), the transmitting-receiving function is realized in the detection process, the near-field blind area of the probe is reduced, the interference signal is reduced, the depth value difference between the shallowest position and the deepest position of the defect is directly read out from the A-type ultrasonic detection device, and thus the height value of the measured defect is directly obtained. The method has the advantages of the high measurement precision of the TOFD detection technology, overcomes the defect that the TOFD technology cannot be applied to the fillet weld, does not need special equipment, test blocks and probes, the ordinary A-type ultrasonic detection equipment and the probe are used, the operation is more convenient, and the method is suitable for the detection of complex structure workpieces. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a structure schematic view of the parallel probe wedge block of the application;

[0024] Figure 2 is a three-view of the wedge block of the application;

[0025] Figure 3 is a principle schematic view of the delay and detection range of the application;

[0026] Figure 4is a schematic diagram of the defect echo signal of the present application;

[0027] In the figure: 1. wedge, 2. probe. DETAILED DESCRIPTION

[0028] The principles and features of the present application are described below, and the examples are used to explain the present application, but not to limit the scope of the present application.

[0029] The measurement method steps of the present embodiment are as follows:

[0030] (1) Production, installation of probe wedge and connection of probe and A-type ultrasonic detection equipment

[0031] The wedge 1 is made of organic glass and is processed into two parallel probes 2. The angle of the probe installed in the wedge is determined according to the thickness of the workpiece to be detected, and the angle is from 45° to 70°. When the thickness of the workpiece to be detected is larger, a wedge with a smaller angle is selected, and when the thickness of the workpiece to be detected is smaller, a wedge with a larger angle is selected. Sound-absorbing material is provided between the two parallel probes to avoid the formation of echo in the wedge. The ordinary straight probe is installed on the wedge, and the two probes are connected to the transmitting (T) and receiving (R) ports of the A-type ultrasonic detection equipment through signal lines.

[0032] (2) Setting of A-type ultrasonic detection instrument and calibration of depth measurement

[0033] Firstly, the working mode of the A-type ultrasonic detection instrument is selected as one transmitting and one receiving mode, the frequency band width is selected as narrow band, the detection mode is selected as radio frequency mode, and the probe is adjusted as longitudinal wave oblique probe.

[0034] The CSK-1A test block is used to measure the probe incident point and sound speed at the R50 and R100 arc positions at the front end. The probe refraction angle is measured at the 50mm circular hole position at the rear end of the CSK-1A test block. The A-type ultrasonic detection instrument is set as depth display, the device delay is set as the ratio of twice the distance from the probe incident point to the center line of the fillet weld and the material sound speed, and the detection range is set as the full thickness detection time of the workpiece minus the delay time.

[0035] (3) Setting of detection sensitivity

[0036] The determination of measurement sensitivity is carried out by using the CSK-IIA series test block. According to the thickness of the workpiece to be detected, the corresponding test block is selected. According to the depth of the fillet weld defect, the horizontal hole closest to the defect depth in the CSK-IIA series test block is selected, the highest reflection echo of the horizontal hole is found, and the gain is adjusted to 80% of the full screen amplitude of the device, and the gain is adjusted to 6dB to 10dB. During actual testing, appropriate adjustment should be made according to the defect echo amplitude. The adjustment basis is to distinguish the upper and lower diffraction signals of the defect.

[0037] (4) Recognition of defect echo signal

[0038] The general defect echo is composed of three signal groups, i.e. defect upper edge diffraction signal, defect reflection echo and defect lower edge diffraction signal. The three signals are superimposed and intertwined as shown in Figure 3 The front end of the upper edge diffraction signal and the end of the lower edge diffraction signal will occupy the front and rear edges of the entire defect echo.

[0039] If the defect height direction is perpendicular or approximately perpendicular to the acoustic beam, the reflection echo in the three signals will be strong, and even may cover the defect lower end diffraction signal, but in any case the defect lower end diffraction signal should appear at the end of the signal, at this time, the end signal can be regarded as the defect lower end diffraction signal.

[0040] If the defect is perpendicular or approximately perpendicular to the detection surface, the reflection echo in the three signals will be low or non-existent, and the diffraction signals of the upper and lower ends of the defect are not affected.

[0041] The peak position of the front edge signal in the complex defect echo signal is found, and the defect upper edge diffraction signal is determined; similarly, the trough position of the rear edge signal in the defect echo signal is found, and the defect lower edge diffraction signal is determined.

[0042] (5) Determination of defect height

[0043] Since the A-type ultrasonic detector is set to depth display, the wave front depth value m of the defect upper edge diffraction signal, the depth value n of the first wave peak of the defect upper edge diffraction signal, and the depth value p of the first wave peak at the end of the defect lower edge diffraction signal can be directly read out.

[0044] Since the defect upper and lower edges are the same positive wave and their wavelengths are equal, the wavelength is four times the difference between the measured wave front depth value of the upper edge diffraction signal and the depth value of the first wave peak of the upper edge diffraction signal, i.e. wavelength = 4*|m-n|; according to the TOFD principle, the depth difference between the two diffraction signals of the defect upper and lower edges is the height h of the defect itself.

[0045] Therefore, the difference between the depth value of the first wave peak of the defect upper edge diffraction signal and the depth value of the first wave peak at the end of the defect lower edge diffraction signal measured by the method is the height of the defect itself plus half the wavelength value, i.e.|n-p|=h+0.5* wavelength.

[0046] Therefore, the difference between the depth value of the first wave peak of the defect upper edge diffraction signal and the depth value of the first wave peak at the end of the defect lower edge diffraction signal measured by the method is the height of the defect itself plus half the wavelength value, i.e.|n-p|=h+0.5* wavelength.

[0047] The defect height is measured by the method of the embodiment, and compared with the actual height of the defect. The data comparison is shown in the following table:

[0048]

[0049] The height in the above table is the height of the defect itself, and the depth is the buried depth.

[0050] From the above table data, it can be seen that the maximum negative deviation of the detection result of the method from the actual size of the defect is -0.7 mm, the maximum positive deviation is 0.7 mm, the detection result has good consistency with the section result, the detection precision reaches within ±1 mm, the method breaks through the barrier that ordinary ultrasonic detection cannot measure the height of the defect, and the measurement precision reaches the measurement precision level of the TOFD technology. However, the method also overcomes the disadvantage that TOFD cannot be used for angle weld detection.

Claims

1. A method of measuring the self-height of an internal defect of a fillet weld, characterized by, It comprises the following steps: Two parallel probes are installed on the wedge to realize single-side detection of the fillet weld, the two probes are longitudinal wave straight probes, and the installation angle of the two probes in the wedge is set to a preset angle according to the thickness of the detected workpiece, the angle ranges from 45° to 70°, and the two probes are respectively connected to the transmitting T port and the receiving R port of the A-mode ultrasonic detector through signal lines; The working mode of the A-mode ultrasonic detector is set to one-transmitting and one-receiving mode, the frequency band width is selected as narrow band, the detection mode is selected as radio frequency mode, and the probe is adjusted as a longitudinal wave oblique probe; The A-mode ultrasonic detector is set to depth display and calibrated; The A-mode ultrasonic detector is used to detect the workpiece, the peak position of the front signal in the obtained defect echo signal is found, that is, the diffraction signal of the upper edge of the defect is determined; Similarly, the trough position of the rear signal in the defect echo signal is found, that is, the diffraction signal of the lower edge of the defect is determined; The wavefront depth value m of the defect upper edge diffraction signal, the depth value n of the first peak of the defect upper edge diffraction signal, and the depth value p of the first peak at the end of the defect lower edge diffraction signal are read out. The defect height h is calculated as h = |n-p| - 2x|m-n|.

2. The method of measuring the height of an internal defect of a weld bead according to claim 1, characterized by, The wedge is made of organic glass wedge.

3. The method of measuring the height of an internal defect of a weld bead according to claim 1, characterized by, A medium is arranged between the two probes to avoid the formation of echo of sound waves in the wedge.

4. The method of measuring the height of an internal defect of a weld bead according to Claim 1, wherein During the calibration process, the probe incident point, sound velocity and probe refraction angle are measured by using the CSK-1A test block: the probe incident point and sound velocity are measured by using the R50 and R100 arc positions at the front end of the CSK-1A test block, and the probe refraction angle is measured at the 50mm hole position at the rear end of the CSK-1A test block.

5. The method of measuring the height of an internal defect of a weld bead according to claim 4, characterized by, The device delay is set as the ratio of twice the distance from the probe incident point to the center line of the fillet weld to the material sound velocity, and the detection range is set as the full-thickness detection time of the workpiece minus the delay time.

6. The method of measuring the height of an internal defect of a weld bead according to Claim 1, wherein Before detecting the workpiece, the detection sensitivity is detected, and the determination of the measurement sensitivity is carried out by using the CSK-IIA series test block, and the corresponding test block is selected according to the thickness of the detected workpiece.

7. The method of measuring the height of an internal defect of a weld bead according to claim 6, wherein According to the depth of the defect in the fillet weld, the horizontal hole in the CSK-IIA series test block closest to the defect depth is selected, the highest reflected echo of the horizontal hole is found, the height is adjusted to 80% of the full-screen amplitude of the device, and the gain is adjusted to 6dB to 10dB.

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