A defect depth calculation method for TOFD detection of unequal thickness butt welds

Abstract

The present application relates to a kind of unequal thickness butt weld TOFD detection defect depth calculation method, comprising the following steps: (1) the thickness direction partition of weld is carried out;(2) the center distance of probe PCS is calculated;(3) the center distance of partition virtual PCS is calculated;(4) making contrast test block, contrast test block is partitioned along the thickness direction;(5) the depth display of specific signal on contrast test block on TOFD image is calculated using equivalent sound path rule;(6) the relationship between image virtual depth and defect actual depth is calculated using equivalent sound path rule.The present application has the advantages that: the present application is based on the premise of current TOFD instrument module for unequal thickness butt weld TOFD detection, proposes scientific setting method, especially proposes depth calibration under the setting, and proposes the concept of "equivalent sound path rule", which is applied to defect depth calculation;This method can be effectively applied to engineering practice, and solves the problem that unequal thickness butt weld TOFD cannot be widely applied.

Description

Technical Field

[0001] This invention relates to a method for calculating the defect depth in butt welds of unequal thickness plates, and particularly to a method for calculating the defect depth in TOFD (Transient Detection and Analysis) of butt welds of unequal thickness plates. Background Technology

[0002] Time-of-flight diffraction (TOFD) is a method based on the interaction between ultrasonic waves and the defect tip. This interaction results in the emission of diffracted waves over a considerable angular range. Detecting these diffracted waves allows for the determination of the defect's presence, depth, and length. In practical testing, the detection range is defined as the through wave (near-surface creeping wave) and the first bottom echo to ensure complete coverage of the workpiece. This method is suitable for inspecting welded seams on flat plates of a certain thickness.

[0003] Existing TOFD (Time-of-Flight Diffraction) technology is mainly designed for butt welds of equal thickness. There is little information available on the inspection setup for butt welds of unequal thickness, and even less detailed information on depth calibration and defect depth calculation methods based on specific setups. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a method for calculating the defect depth of unequal thickness butt welds by TOFD detection. The invention details the detection settings and depth calibration of unequal thickness butt welds using TOFD technology and proposes the concept of the "equivalent sound path rule". The method is used to calculate the depth based on the TOFD detection settings and the equivalent sound path rule.

[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is: a method for calculating the defect depth of unequal thickness butt welds using TOFD detection, the innovation of which is: including the following steps:

[0006] (1) In accordance with the ASME standard, the thickness of the workpiece base material is divided into the first zone and the second zone in the thickness direction for a thickness of 50mm < T < 100mm.

[0007] (2) The first zone uses a combination of probe wedges with a frequency of 5MHz-7.5MHz, a wafer size of φ3mm-φ6mm, and a refraction angle of 60°-70° for detection. The placement of the left and right probe wedges in each group is calculated using geometric knowledge based on the refraction angle of the main sound beam, the focusing depth, and the thinning angle and width of the thick plate. The beam center is focused at the weld center at a depth of d1. The horizontal distance L1 from the weld centerline to the actual incident point of the probe wedge on the thick plate side slope and the horizontal distance L2 from the weld centerline to the actual incident point of the probe wedge on the thin plate side are calculated. Then the probe center spacing PCS = L1 + L2.

[0008] (3) For the first section of the unequal thickness structure, the center distance of the probes on the scanning frame is calculated and assembled as described above. However, when setting up the instrument, virtual angles and virtual PCS are introduced to describe the wedge angles and PCS values ​​input to the instrument. Assumption The left probe needs to be placed on the thinned bevel. The thinning angle is calculated as a. The virtual angle on the left side of the first zone, that is, the angle between the weld center line and the actual main beam, should be b = 70° - a. The virtual angle on the right side is 70°, which is consistent with the actual angle. The calculated value is L3 = d1tan(70° - a). Then the virtual PCS of the first zone is L2 + L3.

[0009] (4) Prepare a comparison test block according to the ASME standard requirements. The comparison test block is divided into two sections along the thickness direction. Each section has two holes. The transverse holes are made by electrical discharge machining at 1 / 4 and 3 / 4 depth of each section. The 1 / 4 depth of the first section is recorded as H1 and the 3 / 4 depth of the second section is recorded as H2 for calibration.

[0010] (5) Analyze the value of depth H1 displayed on the image when the direct wave H0 = 0. Label the virtual incident point of the left sound beam as point A, the focal point of the beam center as point O, and the point where a vertical line drawn from point O intersects the horizontal line containing point A as point D. Label the incident point of the right probe sound beam as point B, and the actual incident point of the left probe sound beam as point C. Set the path of the direct wave to ADB = L3 + L2, and the actual path of the direct wave to CDB = CD + L2. Clearly, CDB > ADB. Therefore, the direct wave in the image... If the displayed depth is greater than 0, and half of the actual direct-pass wave path is CDB / 2, draw circles with centers A and B and a radius of CDB / 2. The intersection of these two circles is denoted as E. The measured depth at point E is d2. Therefore, the path of point E in the virtual setting is equivalent to the actual direct-pass wave path, i.e., AE + BE = CD + DB. Thus, the displayed depth value of the virtual point E is the same as the displayed depth H1 of the direct-pass wave H0 = 0 on the image. Similarly, the displayed depth values ​​of the tips of holes H1 and H2 on the image can be derived using the same method.

[0011] (6) When the virtual depth information of a defect is obtained on the image, its actual depth is determined; the weld thickness is calculated into the depth information on the TOFD image in increments of millimeters, and the calculation function of the Excel spreadsheet is utilized to obtain the actual depth of the defect corresponding to the depth value displayed in each image; in addition, the actual depth of the defect in the second zone is calculated according to the calculation steps (3) to (6).

[0012] Furthermore, in step (6), when the required image display depth value is not available in the Excel spreadsheet, the actual depth value corresponding to the required image display depth value is obtained by interpolation.

[0013] Furthermore, in step (6), when the required image display depth value is not available in the Excel spreadsheet, the step value is changed from 1 mm to 0.5 mm or 0.25 mm or smaller. The Excel spreadsheet is used to calculate the actual depth of the defect corresponding to each image display depth value.

[0014] The advantages of this invention are as follows: For TOFD detection of butt welds with unequal thickness, this invention proposes a scientific setting method based on the existing TOFD instrument modules, especially the depth calibration under this setting, and proposes the concept of "equivalent sound path rule" for defect depth calculation; this method can be effectively applied to engineering practice, solves the problem that TOFD for butt welds with unequal thickness cannot be widely applied, and expands the structural range of TOFD detection. Attached Figure Description

[0015] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0016] Figure 1 This is a schematic diagram of TOFD inspection of unequal thickness butt welds in an example.

[0017] Figure 2 This is a schematic diagram of the structure of the comparative test block in the embodiment.

[0018] Figure 3 This is a TOFD image of an unequal thickness butt weld as an example. Detailed Implementation

[0019] The following embodiments are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the invention to the scope of the embodiments described.

[0020] Example

[0021] The defect depth calculation method for TOFD inspection of unequal thickness butt welds in this embodiment includes the following steps:

[0022] (1) Establish as follows Figure 1 The finite element model of the stepped defect test block shown was used for TOFD detection of the butt weld with unequal thickness. The stepped defect test block has a high plane thickness T1 of 144 mm, a bottom plane thickness T2 of 78 mm, and an outer thickness difference ΔT of 19 mm.

[0023] (2) In accordance with the requirements of ASME specifications, the weld of the stepped defect test block in (1) is divided into sections in the thickness direction. The sections are divided according to the thickness of the bottom plane of the stepped defect test block. The first section is 0-30mm and the second section is 30-78mm.

[0024] (3) Taking the first zone as an example, the first zone uses a combination of probe wedges with a frequency of 5MHz, a wafer size of φ6mm and a refraction angle of 70° for detection. The placement of the left and right probe wedges in each group is calculated using geometric knowledge based on the refraction angle of the main sound beam, the focusing depth, and the thinning angle and width of the thick plate. The sound beam incident point of the left probe is recorded as point C, and the sound beam incident point of the right probe is recorded as point B. The beam center is focused at the weld center at a depth of d1 = 25mm, and this depth point is recorded as point O. A vertical line is drawn from point O and is perpendicular to the horizontal line where point A is located. The point where the two perpendicular lines intersect is recorded as point D. The horizontal distance from point C to point D is calculated to be L1 = 65mm, and the horizontal distance from point B to point D is L2 = 69mm. Then the probe center spacing PCS = 65 + 69 = 134mm.

[0025] (4) For the first section of the unequal thickness structure, the center distance of the probes on the scanning frame is assembled according to the above calculation. However, when setting up the instrument, virtual angle and virtual PCS are introduced to describe the wedge angle and PCS value input to the instrument. The left probe needs to be placed on the thinned inclined edge. The calculated thinning angle is 7°. The virtual angle on the left side of the first section should be 63°, and the virtual angle on the right side should be 70°, which is consistent with the actual value. The horizontal distance from point A to point D is calculated to be L3 = 49mm. Then the virtual PCS of the first section is 69 + 49 = 118mm.

[0026] (5) Prepare comparative test blocks according to ASME standard requirements, such as... Figure 2 As shown, the comparison test block is divided into two sections along the thickness direction, referring to the stepped defect test block. Each section has two holes, and the transverse holes are made by electrical discharge machining at 1 / 4 and 3 / 4 depths of each section. The 1 / 4 depth of the first section is recorded as H1 = 7.5 mm, and the 3 / 4 depth of the section is recorded as H2 = 22.5 mm, which are used for calibration.

[0027] (6) Analyze the value of depth H1 displayed on the image when the through wave H0 = 0, such as Figure 3 As shown, the set path of the direct-through wave is ADB = L3 + L2 = 49 + 69 = 118 mm, and the actual path of the direct-through wave is CDB = CD + L2 = 65.5 + 69 = 134.5 mm. Obviously, CDB > ADB, so the depth displayed by the direct-through wave on the image is greater than 0. Half of the actual path of the direct-through wave is 67.25 mm. Draw circles with A and B as centers and 67.25 mm as radius, and denote the intersection of the two circles as E. The measured depth of point E is 32 mm. Therefore, the path of point E in the virtual setting is equivalent to the actual path of the direct-through wave, i.e., AE + BE = CD + DB. Thus, the depth displayed at the virtual point E is the value of the depth H1 displayed on the image when the direct-through wave H0 = 0. Similarly, the depth values ​​displayed on the image for the tips of holes H1 and H2 can be obtained using the same method.

[0028] (7) When the virtual depth information of a defect is obtained on the image, its actual depth is determined; the weld thickness is calculated into the depth information on the TOFD image in increments of millimeters, and the calculation function of the Excel spreadsheet is used with the formula, as shown in the table below, to obtain the actual depth of the defect corresponding to the depth value displayed in each image; when the instrument TOFD detects and collects data after calibration according to this setting, if a defect is found at the first partition of the display depth of 35mm, the value of 35 is found in column M of the table below, and then moved to column K in parallel, to obtain the corresponding actual depth of 10mm; if the display depth is at 37mm, there is no value of 37 in column M, which can be solved by the following two methods: (1) Use interpolation to obtain the actual depth value of column K when column M is 37mm; (2) Change the step value of column K from 1mm to 0.5mm or 0.25mm, or even smaller step value, and use the calculation function of the Excel spreadsheet with the formula to obtain the actual depth of the defect corresponding to the depth value displayed in each image.

[0029] In addition, the actual depth of the defect in the second zone is calculated according to the calculation steps (3) to (7).

[0030]

[0031] The foregoing has shown and described the basic principles and main features of the present invention, as well as its advantages. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for calculating the defect depth of a butt weld with unequal thickness detected by TOFD, characterized in that: Includes the following steps: (1) According to the ASME standard, the thickness of the workpiece base material is divided into the first zone and the second zone in the thickness direction for a thickness of 50mm < T < 100mm; (2) The first zone uses a combination of probe wedges with a frequency of 5MHz-7.5MHz, a wafer size of φ3mm-φ6mm, and a refraction angle of 60°-70° for detection. The placement of the left and right probe wedges in each group is calculated using geometric knowledge based on the refraction angle of the main sound beam, the focusing depth, and the thinning angle and width of the thick plate. The beam center is focused at the weld center at a depth of d1. The horizontal distance L1 from the weld centerline to the actual incident point of the probe wedge on the thick plate side slope and the horizontal distance L2 from the weld centerline to the actual incident point of the probe wedge on the thin plate side are calculated. Then the probe center spacing PCS = L1 + L2. (3) For the first section of the unequal thickness structure, the center distance of the probes on the scanning frame is calculated and assembled as above. However, when setting up the instrument, virtual angle and virtual PCS are introduced to describe the wedge angle and PCS value input to the instrument. Assuming that the left probe needs to be placed on the thinning bevel, the thinning angle is calculated as a. The virtual angle on the left side of the first section, that is, the angle between the weld center line and the actual main beam, should be b=70°-a. The virtual angle on the right side is 70°, which is consistent with the actual angle. L3=d1tan(70°-a) is calculated. Then the virtual PCS of the first section is L2+L3. (4) Prepare a comparison test block according to the ASME standard requirements. The comparison test block is divided into two sections along the thickness direction. Each section has two holes. Horizontal holes are made by electrical discharge machining at 1 / 4 and 3 / 4 depth of each section. The hole at 1 / 4 depth of the first section is designated as hole H1, and the hole at 3 / 4 depth of the first section is designated as hole H2, for calibration. (5) Analyze the value of depth H1 displayed on the image when the direct wave H0=0. Record the beam center focus point as point O, the incident point of the right probe beam as point B, and the actual incident point of the left probe beam as point C. Record the intersection of the horizontal line passing through point B and the line connecting OC as the virtual incident point A of the left beam. Record the point where the vertical line drawn through point O is perpendicular to the horizontal line where point A is located and the two perpendicular lines intersect as point D. Set the sound path of the direct wave to ADB=L3+L2, and the sound path of the actual direct wave to CDB=CD+L2. Obviously, CDB>A If DB is the actual path length of the through wave, then the depth displayed on the image is greater than 0. Half of the actual path length of the through wave is CDB / 2. Draw circles with A and B as centers and CDB / 2 as radii, and denote the intersection of the two circles as E. The measured depth of point E is d2. Therefore, the path length of point E in the virtual setting is equivalent to the actual path length of the through wave, i.e., AE + BE = CD + DB. Thus, the depth displayed value of the virtual point E is the value of the depth H1 displayed on the image when the through wave H0 = 0. Similarly, the display depth values ​​of the tips of holes H1 and H2 on the image can be obtained. (6) When the virtual depth information of a defect is obtained on the image, its actual depth is determined; the weld thickness is calculated into the depth information on the TOFD image in increments of millimeters, and the calculation function of the Excel spreadsheet is utilized to obtain the actual depth of the defect corresponding to the depth value displayed in each image. (7) Calculate the actual depth of the defect in the second zone according to steps (3) to (6).

2. The method for calculating the defect depth of unequal thickness butt welds using TOFD detection according to claim 1, characterized in that: In step (6), when the required image display depth value is not available in the Excel spreadsheet, the actual depth value corresponding to the required image display depth value is obtained by interpolation.

3. The method for calculating defect depth in TOFD inspection of unequal thickness butt welds according to claim 1, characterized in that: In step (6), if the required image display depth value is not available in the Excel spreadsheet, the step value is changed from 1 mm to 0.5 mm or 0.25 mm or smaller. The Excel spreadsheet is used to calculate the actual depth of the defect corresponding to each image display depth value.

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