Sensitivity compensation method for ultrasonic testing of welds with coating thickness within 600 μm

Abstract

The present invention relates to a sensitivity compensation method for ultrasonic testing of welds with a coating thickness within 600 μm. The method comprises the following steps: obtaining measurement results of a workpiece with a coating thickness within 600 μm, wherein the measurement results are defect length, defect depth, and defect maximum echo height obtained by performing phased array ultrasonic testing on the workpiece; obtaining defect data; wherein the defect data is obtained by compensating the measurement results according to a relationship curve, wherein the relationship curve is: Y=3.0514ln(X)+13.964; the defect data includes defect length, defect height, and maximum echo height, wherein X is the ratio of coating thickness to the diameter of a standard reflector, and Y is the sensitivity compensation amount corresponding to different X values. The method has the advantage that, when performing defect detection on a coated workpiece, no additional testing is required, and no special test block needs to be made according to on-site conditions. Therefore, when the on-site coating thickness changes, the coating of the special test block does not need to be changed, thereby greatly improving the efficiency of defect detection.

Description

Technical Field

[0001] The present invention relates to the field of phased array ultrasonic nondestructive testing, in particular to a sensitivity compensation calculation method for ultrasonic testing of coated welds. Background Art

[0002] Currently, there is limited research on nondestructive testing methods for coated hulls. The reasons are: 1) In most cases, the coating must be ground off before testing to avoid its impact on the inspection; 2) Some non-contact nondestructive testing methods, such as eddy current and radiography, can ignore the coating's impact on inspection. However, these methods cannot meet all inspection needs. For example, in some cases, grinding the coating can affect the workpiece, such as damaging the workpiece's anti-corrosion layer; eddy current can only detect near-surface weld defects and is not ideal for detecting internal defects; and radiography is also not ideal for thick plates. This leads to the need to perform ultrasonic testing or thickness measurement on welds in some cases without grinding the workpiece surface coating.

[0003] For coated welds, the existing technologies include:

[0004] Method 1: Comparative test block method

[0005] The test surface of a standard test block is treated according to the workpiece's corrosion protection process. A DAC curve is generated on the treated test block. This DAC curve can then be used for ultrasonic testing on workpieces with the same coating. This method can effectively offset the attenuation of the coating on the test block. The sandblasting and coating of the test block must be performed according to the same process requirements as the workpiece, ensuring that the surface roughness of the test block is the same as that of the workpiece after sandblasting and that the thickness of each coating layer on the test block is the same as that on the workpiece surface. The DAC curve generated on the treated test block can then be used for ultrasonic testing on workpieces with the same coating.

[0006] Method 2: Compensation determination method

[0007] Create a test panel with a defect (a short or long horizontal hole can be machined into the panel). First, create a DAC curve using a standard test block. Then, use this curve to detect the defect and record the defect's reflected amplitude A. The defective test panel is then processed according to the workpiece's spraying process. After spraying, use the original curve again to test the panel and record the defect's reflected amplitude B after spraying. Subtract amplitude B from amplitude A to determine the attenuation compensation. This compensation is then used to compensate the original defect signal. The compensation calculated for a single defect will have errors during this process. Multiple defects can be created and the change before and after values for each defect calculated using the above method. Based on this principle, an approximate relationship between coating thickness and defect signal can be derived. This relationship can be used to guide the determination of signal compensation for different coating thicknesses during on-site testing.

[0008] However, both methods have common disadvantages: low efficiency, the need for additional testing, and the need to make special test blocks for on-site conditions. Moreover, when the coating thickness changes on site, the coating of the test block needs to be changed.

[0009] In summary, there is an urgent need for a sensitivity compensation calculation method for ultrasonic testing of coated welds that can achieve coated detection without additional testing and special test blocks. Summary of the Invention

[0010] The object of the present invention is to provide a sensitivity compensation calculation method for ultrasonic testing of coated welds that can achieve coated weld testing without the need for additional testing and special test blocks.

[0011] To achieve the above object, the technical solution adopted by the present invention is:

[0012] A sensitivity compensation method for ultrasonic testing of welds with a coating thickness within 600 μm is provided, wherein measurement results of a workpiece with a coating thickness within 600 μm are obtained, wherein the measurement results are defect length, defect depth, and maximum defect echo height obtained by performing phased array ultrasonic testing on the workpiece; and defect data are obtained; wherein the defect data is obtained by compensating the measurement results according to a relationship curve, wherein the relationship curve is obtained by measuring a standard reflector; the defect data includes defect length, defect height, and maximum echo height.

[0013] As a preferred technical solution, the relationship curve is: Y=3.0514ln(X)+13.964, wherein X is the ratio of the coating thickness to the diameter of the transverse hole of the standard reflector, and Y is the sensitivity compensation corresponding to different X values.

[0014] As a preferred technical solution, obtaining the relationship curve includes: using an ultrasonic probe to detect a standard reflector; spraying a certain coating layer thickness on the standard reflector and recording the reflection amplitude after spraying; obtaining the attenuation compensation amount; obtaining the quantitative relationship between the research compensation amount and the coating thickness, including obtaining the relationship between the sound field intensity and the coating thickness.

[0015] As a preferred technical solution, the ultrasonic probe is a K2 (63.4°) conventional ultrasonic probe, the standard reflector is a test block with a transverse hole (∅3×15), and the reference wave height during testing is 80% of the transverse hole wave height.

[0016] As a preferred technical solution, the calculation method of the sound field intensity is: dB=20log(A / B), where A and B are the echo heights of different reflectors respectively.

[0017] As a preferred technical solution, the film thickness (coating thickness) is dimensionlessly processed, with the ratio of film thickness to aperture as the independent variable and the compensation amount as the dependent variable, to obtain the relationship between the compensation amount and (coating thickness / standard reflector diameter).

[0018] The advantages of the present invention are:

[0019] The sensitivity compensation method for ultrasonic detection of welds with a coating thickness within 600 μm described in the present invention does not require additional testing when performing defect detection on coated workpieces, and does not require the preparation of special test blocks based on on-site conditions. Therefore, when the on-site coating thickness changes, there is no need to change the coating of the special test block, which greatly improves the efficiency of defect detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Attachment Figure 1 This is a flow chart of the sensitivity compensation method for ultrasonic detection of welds with a coating thickness within 600 μm according to the present invention.

[0021] Attachment Figure 2 It is the relationship curve between coating thickness and compensation. DETAILED DESCRIPTION

[0022] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content of the present invention record, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the application's appended claims.

[0023] Example 1

[0024] Please see the attached Figure 1 , attached Figure 1 This is a flow chart of the ultrasonic detection sensitivity compensation method for welds with a coating thickness within 600 μm according to the present invention. The ultrasonic detection sensitivity compensation method for welds with a coating thickness within 600 μm:

[0025] Step S10: obtaining measurement results of a workpiece with an inner coating thickness of 600 μm, wherein the measurement results are defect length, defect depth, and defect maximum echo height obtained by performing phased array ultrasonic testing on the workpiece;

[0026] Use ultrasonic probes to directly perform phased array inspection on coated workpieces such as coated ship hulls, and obtain the defect length, defect depth and maximum defect echo height;

[0027] Step S20: Acquire defect data; wherein the defect data is obtained by compensating the measurement results according to a relationship curve, wherein the relationship curve is: Y = 3.0514ln(X) + 13.964; the defect data includes defect length, defect height, and maximum echo height, wherein X is the ratio of the coating thickness to the diameter of the standard reflector's transverse hole, and Y is the sensitivity compensation corresponding to different X values;

[0028] The relationship curve: Y=3.0514ln(X)+13.964 is used to compensate the measurement results to obtain relatively true defect data of the coated workpiece; that is, by using the relationship curve to perform corresponding compensation calculations on the defect length, defect depth and defect maximum echo height obtained by ultrasonic testing of the coated workpiece, the influence of the coating on the detection can be greatly eliminated.

[0029] It should be noted that the acquisition of the relationship curve includes:

[0030] Step S100: using an ultrasonic probe to detect a standard reflector;

[0031] During on-site inspections, in addition to thickness measurement, ultrasonic measurement of internal defects is a major focus. When ultrasonic testing is performed with coating thicknesses not exceeding 600μm, the coating's influence on defect depth measurement is not significant, so defect data can be obtained by compensating the measurement results. Conventional ultrasonic sensitivity curves are generated using standard reflectors (such as through-holes, flat-bottom holes, and notches). The sensitivity curves generated using standard reflectors are then used to measure actual defects. Therefore, by studying the effect of coating thickness on the equivalent reflected signal from the standard reflector, corresponding compensation curves can be generated, providing compensation recommendations.

[0032] In this embodiment, the standard reflector used to illustrate the process is a test block with a transverse hole (∅3×15), and the ultrasonic probe is a K2 (63.4°) conventional ultrasonic probe. The test block is tested using the conventional ultrasonic probe, and the transverse hole wave height is adjusted to 80% as the reference wave height.

[0033] Step S200: spraying a certain coating thickness on a standard reflector and recording the reflection amplitude after spraying;

[0034] It should be understood that the standard reflector can be sprayed with several layers, and the reflected amplitude after each spraying is recorded. Preferably, two layers of paint are sprayed on the test block, and the coating thickness is measured and recorded respectively. The test block with the sprayed coating is then ultrasonically tested to obtain defect measurement results, including defect length, defect height, and maximum echo height. The following table shows the effect of coating thickness on the standard reflector echo:

[0035]

[0036] Step S300: obtaining an attenuation compensation amount and compensating the entire sensitivity curve using the attenuation compensation amount;

[0037] That is, the deviation (compensation) between the measurement results of different coating thicknesses and the unsprayed measurement results is calculated;

[0038] Step S400: Obtain the quantitative relationship between the compensation amount and coating thickness, and complete supplementary curve fitting, which includes obtaining the relationship between the acoustic field intensity and coating thickness. Specifically, the film thickness (coating thickness) is dimensionlessly processed to characterize the relationship between the acoustic field intensity and coating thickness. The relationship between the compensation amount and (coating thickness / standard reflector diameter) is obtained, using the ratio of film thickness to pore diameter as the independent variable and the compensation amount as the dependent variable.

[0039] Please see the attached Figure 2 , attached Figure 2 It is the relationship curve between coating thickness and compensation. In this embodiment, the compensation amount is in dB, and the specific calculation method of the sound field intensity is dB=20log(A / B), where A and B are the echo heights of different reflectors, respectively. It can be seen that the sound field intensity is a non-equivalent ratio. The unit of coating thickness is mm. In order to characterize the relationship between sound field intensity and coating thickness, the film thickness is dimensionless. Since the higher the defect equivalent, the greater the attenuation under the same thickness of the coating, that is, the compensation value is inversely proportional to the equivalent of the defect itself. Therefore, the logarithm of the ratio of film thickness to aperture is used as the independent variable, the compensation amount dB is used as the dependent variable, and the data in the table are logarithmically fitted. The relationship between the compensation dB value and (coating thickness / standard reflector diameter) can be obtained as follows:

[0040] Y=3.0514ln(X)+13.964···········(1)

[0041] In some preferred embodiments, for ease of use, it can be simplified to:

[0042] Y=3ln(X)+14··············(2)

[0043] Where X is the ratio of the coating thickness to the diameter of the standard reflector's transverse hole; Y is the sensitivity compensation corresponding to different X values.

[0044] It should be noted that the sensitivity compensation method for ultrasonic detection of welds with a coating thickness within 600 μm described in the present invention obtains a relationship curve by performing ultrasonic detection on a standard test block. The relationship curve can compensate for the influence of the coating thickness within 600 μm on the actual defect detection of the weld, and can realize defect detection of coated workpieces. In addition, according to the needs of on-site coated workpiece detection, the corresponding compensation amount can be obtained by changing the relationship curve corresponding to different standard test block specifications, that is, the X value.

[0045] Example 2

[0046] This example aims to verify the natural defects of the ultrasonic detection sensitivity compensation method for welds with a coating thickness within 600 μm described in the present invention:

[0047] (1) Experimental parameters: Probe: 5L64-A2; Host: Olympus Ominiscan MX2; Active chips: 1 to 16 chips; Scanning angle range: 400 to 700.

[0048] (2) Experimental process

[0049] TCG curves were generated using RB test blocks. Test blocks were processed. Test block 1 contained one defect (slag inclusion), and test block 2 contained two defects (slag inclusions).

[0050] When not sprayed, two test blocks were subjected to phased array ultrasonic testing and the original data were recorded;

[0051] 1) Apply the first coat of primer to the test piece, measure the coating thickness, and record it. Perform phased array ultrasonic testing on the sprayed test piece. Obtain defect measurements, including defect length, defect height, and maximum echo height.

[0052] 2) Apply a second coat of paint to the test piece, measure the coating thickness, and record it. Then, perform phased array ultrasonic testing on the test piece after the second coat. Obtain defect measurements, including defect length, defect depth, and maximum echo height.

[0053] 3) The deviation (compensation) between the measurement results at different paint thicknesses and the unsprayed measurement results is calculated to verify the reliability of formula (1).

[0054] (3) Experimental results

[0055] Analyze the test results in OmniPC and obtain the data table of the influence of natural defects on coating thickness verification:

[0056]

[0057] The relative compensation values in the above table are actual measurement results. To verify formula (1), the coating thickness parameters and the standard body diameter in the table are substituted into formula (1) to obtain sensitivity compensation reference values for different coating thicknesses. The error between the calculated results and the measured results is shown in the following table:

[0058]

[0059] For test pieces with coating thicknesses of 600 μm and 700 μm, the compensation value exceeds 12 dB, which does not meet the requirements for acoustic energy loss correction in EN 1714. Therefore, the fitted relationship curve of the present invention is not currently considered for application to coatings thicker than 600 μm. At the same time, this embodiment shows that the compensation effect of the ultrasonic weld detection sensitivity compensation method for coatings within 600 μm of the present invention on coatings below 600 μm meets the requirements for acoustic energy loss correction in EN 1714, thus enabling effective measurement of coated workpieces.

[0060] It should be noted that to investigate the impact of coatings on ultrasonic nondestructive testing (NDT) and provide a reference for the implementation of NDT on coated ship welds, this paper conducted theoretical and experimental research on the effect of coating thickness on ultrasonic testing results. Theoretically, Snell's law was used to qualitatively investigate the effect of coating thickness on ultrasonic positioning. The results showed that the presence of coatings deviates from the accuracy of ultrasonic positioning. Furthermore, due to the attenuation of the acoustic beam in the coating, the intensity of the reflected wave of the defect signal is weakened.

[0061] Experiments investigated the effect of coating thickness on ultrasonic thickness measurement results. Thickness measurements were performed on test blocks of known thickness for various coating thicknesses. Based on these results, a linear relationship between coating thickness and measurement error was established, demonstrating that the error between the measured and true thickness increases with increasing coating thickness. Subsequent experiments on test blocks of varying thicknesses confirmed the reliability of this linear relationship.

[0062] Experiments investigated the effect of coating thickness on ultrasonic inspection of weld defects. Standard hole reflector test blocks were fabricated and, through experiments on these test blocks, a relationship between coating thickness and reference compensation sensitivity was established. Testing on test blocks with natural defects also demonstrated that the error in this formula is small for smaller coating thicknesses. For thicknesses below 600 μm, the error between the theoretically calculated and measured results is within 12%.

[0063] This research finding can be used for ultrasonic testing of ship hulls with coating thicknesses up to 600 μm and relatively uniform surface roughness. The significance of this study lies in its first investigation of the relationship between coating thickness and quantitative sensitivity compensation, providing a feasible solution for rapid ultrasonic testing of large, in-service ships.

[0064] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the principles of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention.

Claims

1. A method for compensating the sensitivity of ultrasonic testing of welds with a coating thickness within 600 μm, characterized in that: Obtaining measurement results of workpieces with the same coating of different coating thicknesses within 600 μm, wherein the measurement results are defect length, defect depth, and defect maximum echo height obtained by phased array ultrasonic testing of the workpiece; Obtain defect data; wherein the defect data is obtained by compensating the measurement results according to a relationship curve, the relationship curve being obtained by measuring a standard reflector; the defect data includes defect length, defect height, and maximum echo height; the relationship curve is: Y=3.0514ln(X)+13.964, the standard reflector is a test block with a transverse hole having a diameter of 3 mm and a depth of 15 mm, and the reference wave height during testing is 80% of the transverse hole wave height, wherein X is the ratio of the coating thickness to the diameter of the standard reflector transverse hole, and Y is the sensitivity compensation corresponding to different X values, where the coating thickness is in millimeters and the reflector diameter is in millimeters.

2. The method for compensating the sensitivity of ultrasonic detection of welds with a coating thickness within 600 μm according to claim 1, characterized in that: The acquisition of the relationship curve includes: Using an ultrasonic probe to detect a standard reflector; Spray a certain coating thickness on the standard reflector and record the reflection amplitude after spraying; Get the attenuation compensation amount; The quantitative relationship between the research compensation amount and the coating thickness is obtained, which includes obtaining the relationship between the acoustic field intensity and the coating thickness.

3. The method for compensating the sensitivity of ultrasonic detection of welds with a coating thickness within 600 μm according to claim 2, characterized in that: The ultrasonic probe is a K2 conventional ultrasonic probe with a refraction angle of 63.4°.

4. The method for compensating the sensitivity of ultrasonic detection of welds with a coating thickness within 600 μm according to claim 3, characterized in that: The calculation method of the sound field intensity is: dB=20log(A / B), where A and B are the echo heights of different reflectors respectively.

5. The method for compensating the sensitivity of ultrasonic detection of welds with a coating thickness within 600 μm according to claim 3, characterized in that: The coating thickness, i.e., the film thickness, is dimensionlessly processed, with the ratio of film thickness to pore diameter as the independent variable and the compensation amount as the dependent variable, to obtain the relationship between the compensation amount and the X value.

Images