An ultrasonic evaluation method for material differences in structures with variable curvature and thickness

Abstract

This invention proposes an ultrasonic evaluation method for the material differences in structures with variable curvature and thickness. This method employs ultrasonic testing, selecting appropriate testing methods, frequencies, and probe types based on the ultrasonic detectability of the material. Automatic imaging testing is performed on both a comparison test block and the part under test, and the images are homogenized. Using the comparison test block image as a benchmark, the corresponding data points in the image of the part under test are normalized. The amplitude and area information of the normalized data points are used to evaluate the material differences in the part under test. This invention effectively eliminates the complex sound beam path and sound energy loss problems caused by the longitudinal and transverse wave conversion introduced by oblique beams when sound waves propagate in complex-shaped parts. It also eliminates the differences in sound attenuation and sound velocity in different sound propagation directions of anisotropic materials, enabling rapid and accurate determination of the material attenuation coefficient in a specific direction. The test results have been verified to be accurate and reliable.

Description

Technical Field

[0001] This invention is an ultrasonic evaluation method for material differences in structures with variable curvature and thickness, belonging to the field of nondestructive testing technology. Background Art

[0002] Ultrasonic testing is a commonly used non-destructive testing technique in industry. It can detect internal defects by utilizing the reflection, scattering, and attenuation of sound waves during propagation within materials without damaging them. Furthermore, for parts with parallel surfaces, the intensity of the reflected echo from the bottom surface of the tested part, along with the degree of material attenuation during sound wave propagation, allows for the evaluation of material uniformity. This includes assessing localized coarse grains, grain distribution, porosity, and the content of certain elements. Material uniformity significantly impacts the mechanical properties of materials; therefore, evaluating material uniformity using non-destructive testing methods is of great importance and has numerous engineering applications.

[0003] However, for parts with non-parallel surfaces, variable curvature, and variable thickness, the propagation law of sound waves inside them is more complex. Affected by the deformed surface, sound waves may undergo refraction, scattering, and waveform conversion at multiple interfaces. Sound attenuation is no longer solely caused by material uniformity. It is difficult to simply judge the material uniformity by the degree of sound attenuation of the bottom surface reflected echo. Therefore, this patent proposes an ultrasonic evaluation method for the material differences of structures with variable curvature and variable thickness. Summary of the Invention

[0004] This invention addresses the aforementioned existing technical situation by providing an ultrasonic evaluation method for the material differences of structures with variable curvature and thickness. Its purpose is to address the lack of non-destructive evaluation methods for the material uniformity of parts with complex surfaces. This invention proposes a method that can achieve non-destructive evaluation of the material uniformity of parts with complex surfaces without damaging the part, thus providing non-destructive testing technology support for the reliability of material quality.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] The ultrasonic evaluation method for material differences in structures with variable curvature and thickness employs the following steps for detection and evaluation:

[0007] Step 1: The testing system consists of an ultrasonic flaw detector, an ultrasonic probe, and a comparison test block;

[0008] Step 2: Based on the ultrasonic detectability of the material, select the appropriate ultrasonic testing method, testing frequency, and probe type to test the comparison test block. Collect the bottom surface reflected echo or transmitted wave signal amplitude of each test part for imaging and record it as image C1.

[0009] The sensitivity adjustment method during the detection process is as follows: Adjust the gain of the ultrasonic flaw detector so that the maximum value of the amplitude of the imaging acoustic signal displayed on the ultrasonic flaw detector screen is equal to 80%, and ensure that the amplitude of all acquired acoustic signals displayed on the ultrasonic flaw detector screen is within the range of 30% to 80%. If the above requirements cannot be met, the detection method, detection frequency, probe type, water distance parameter should be adjusted, or zonal detection should be adopted until the amplitude of the acoustic signal of the comparative test block ultrasonic detection is within the range of 30% to 80% displayed on the ultrasonic flaw detector screen.

[0010] Step 3: Use the same ultrasonic testing method, testing frequency, and probe type as the comparison test block testing in Step 2 to test the part under test. Collect the bottom surface reflected echo or transmitted wave signal amplitude of each test part of the part under test and record it as image C2.

[0011] Step 4: Perform homogenization on the detected images C1 and C2 to obtain the corrected images C1′ and C2′;

[0012] Step 5: Using the data points of image C1′ as a reference, normalize the corresponding data points in image C2′. The normalization method is shown in equation (1).

[0013] D=[20lg(80% / A2)-20lg(80% / A1)] / T (1)

[0014] Where: A1——Amplitude of single-point imaging signal in image C1′ (unit: %);

[0015] A2—Amplitude of single-point imaging signal in image C2′ (unit: %);

[0016] T—Sound path at the signal acquisition point (unit: mm);

[0017] D — Normalized amplitude of the single-point imaging signal in image C2′ (unit: dB)

[0018] Step 6: Reconstruct the detection image C3 using the normalized amplitude D, and use the amplitude and area information of the data points in image C3 to evaluate the differences in the material of the detected part.

[0019] During implementation, the structural form, curvature change, and thickness change of the comparison test block in step one are the same as those of the part being tested. The material composition and uniformity of the comparison test block meet the material technical requirements, and the internal porosity is considered to be zero.

[0020] In practice, the ultrasonic testing methods in step two include two types: ultrasonic pulse reflection testing and ultrasonic pulse penetration testing.

[0021] In practice, the selection of ultrasonic testing method, testing frequency and probe type in step two is based on the type of material of the part being tested, material attenuation, part thickness, structural form and the size of the defect to be tested.

[0022] Furthermore, for metallic materials, parts with low material attenuation, small thickness, and small required defect size, pulse reflection method, higher detection frequency, and focusing probe are selected for detection.

[0023] For non-metallic materials, parts with high material attenuation, large thickness, or parts requiring large defect sizes, pulse penetration testing, lower detection frequencies, and flat probes are often used for inspection.

[0024] In practice, the amplitude of the bottom surface reflected echo or transmitted wave signal collected in step two for each detection location is selected by choosing the first positive peak value in the bottom surface reflected echo or transmitted wave signal that triggers the imaging signal gate.

[0025] In practice, the homogenization process for the detected image in step four starts from the initial sampling point. The average value of the sampled values ​​of the four vertices of a quadrilateral with a side length equal to the scanning interval is used to replace the original sampled values ​​of the four vertices of the quadrilateral. This process is repeated to homogenize the data in the image.

[0026] In implementation, the sound path T of the signal acquisition point in step five is calculated based on the sound beam propagation angle, the curvature and thickness of the inspected part, and the waveform change to obtain the propagation path of the sound wave of the first positive peak of the trigger signal gate, or it can be calculated using sound field simulation software.

[0027] The features and beneficial effects of the technical solution of this invention are as follows:

[0028] 1. The use of non-destructive testing methods to evaluate the material uniformity of parts with complex shapes expands the application range of existing non-destructive testing of material uniformity for part structures.

[0029] 2. It can detect the material uniformity of the entire volume of the part without damaging it;

[0030] 3. The detection method is simple and easy to operate;

[0031] 4. The accuracy of the test results meets the requirements for material use. Detailed Implementation

[0032] The technical solution of the present invention will be further described in detail below with reference to the embodiments:

[0033] Example 1

[0034] The porosity of an engine fan blade was tested. The fan blade is made of carbon fiber reinforced resin matrix composite material and is manufactured using 3D weaving + RTM process. The blade body is hyperboloid and the thickness gradually changes from 1mm to 3mm.

[0035] The steps for detection and evaluation using the ultrasonic evaluation method for material differences in structures with varying curvature and thickness, as described in this invention, are as follows:

[0036] Step 1: Prepare two comparison test blocks with the same material, shape, and manufacturing process as the fan blades;

[0037] Step 2: The control block is tested using a water-jet ultrasonic penetration method. The probe frequency is 5MHz, the crystal diameter is 12mm, the water jacket diameter is 6mm, and the water distance is 50mm. The acoustic energy signal incident on the control block and propagated within it is collected and received by the ultrasonic probe. The gain of the ultrasonic flaw detector is adjusted so that the maximum amplitude of the acoustic energy signal displayed on the ultrasonic flaw detector screen is equal to 80%, and all collected acoustic energy signals are displayed within the range of 30% to 80% on the ultrasonic flaw detector screen. C-scan imaging is performed to obtain the ultrasonic C-scan image C1.

[0038] Two comparison test blocks were tested under the same ultrasonic testing method and testing parameters to obtain ultrasonic C-scan images. The difference in acoustic energy signal amplitude at corresponding positions in the two C-scan images was no greater than 5% of the full-screen scale of the ultrasonic testing instrument display.

[0039] The internal porosity of the aforementioned comparison block was measured. For the locations in the comparison block where the curvature or thickness variation was greater than ±10%, and for the locations in the C-scan image where the acoustic energy amplitude variation was greater than ±10%, three cubic samples with a center-to-center distance of no more than 20 mm along the thickness direction were selected. The projected area of ​​each cubic sample along the thickness direction was 10 mm × 10 mm, and the thickness of the cubic sample was equal to the thickness of the corresponding comparison block. Micro-nano CT was then performed on the cubic samples, and image processing software was used to statistically analyze the internal porosity. The porosity value obtained from the sampling measurement of this zero-porosity sample was 0.11%. Since the amplitude difference between corresponding points in the ultrasonic detection images of the two zero-porosity samples under the same detection conditions was no greater than 5%, the internal porosity of the other comparison block was considered to be approximately 0.11%, and this was used as the comparison block for subsequent fan blade porosity testing.

[0040] Step 3: The fan blades are tested using ultrasonic testing. The fan blade clamping method, detection gain value and other detection parameters are the same as those of the above-mentioned comparative test block. The ultrasonic C-scan image C2 of the tested fan blade is obtained.

[0041] The detected images C1 and C2 are homogenized to obtain the corrected images C1′ and C2′.

[0042] Using the data points of image C1′ as a reference, the corresponding data points in image C2′ are normalized. The normalization method is shown in equation (1).

[0043] D=[20lg(80% / A2)-20lg(80% / A1)] / T (1)

[0044] Where: A1——Amplitude of single-point imaging signal in image C1′ (unit: %);

[0045] A2—Amplitude of single-point imaging signal in image C2′ (unit: %);

[0046] T—Sound path at the signal acquisition point (unit: mm);

[0047] D — Normalized amplitude of the single-point imaging signal in image C2′ (unit: dB)

[0048] The normalized amplitude D is used to reconstruct the detection image C3, and the amplitude and area information of the data points in image C3 are used to evaluate the porosity of the blade.

[0049] Example 2

[0050] The uniformity of internal grains of an L-shaped metal part was tested. The L-shaped part was made of TC17 titanium alloy, with a radius of curvature of 9mm and a thickness that gradually increased from 2mm to 4mm.

[0051] The steps for detection and evaluation using the ultrasonic evaluation method for material differences in structures with varying curvature and thickness, as described in this invention, are as follows:

[0052] Step 1: Prepare two comparative test blocks with the same material, shape, and manufacturing process as the L-shaped TC17 titanium alloy part;

[0053] Step 2: The comparison test block is tested using the water immersion ultrasonic reflection method. The detection probe frequency is 5MHz, the crystal diameter is 12mm, the probe focal length is 90mm, and the detection water distance is 90mm. The bottom surface reflected acoustic energy signal is collected after being incident on the comparison test block and propagating within the comparison test block and received by the ultrasonic probe. The gain of the ultrasonic flaw detector is adjusted so that the maximum amplitude of the acoustic energy signal displayed on the ultrasonic flaw detector screen is equal to 80%, and it is ensured that the amplitude of all collected acoustic energy signals displayed on the ultrasonic flaw detector screen is within the range of 30% to 80%. C-scan imaging detection is performed to obtain ultrasonic C-scan image C1.

[0054] Two comparison test blocks were tested under the same ultrasonic testing method and testing parameters to obtain ultrasonic C-scan images. The difference in acoustic energy signal amplitude at corresponding positions in the two C-scan images was no greater than 5% of the full-screen scale of the ultrasonic testing instrument display.

[0055] The internal porosity of the aforementioned comparison block was measured. For areas in the comparison block where curvature or thickness changes were greater than ±10%, and for areas where acoustic energy amplitude changes were greater than ±10% in the C-scan image, three cubic samples with a center-to-center distance of no more than 20 mm along the thickness direction were selected. The projected area of ​​each cubic sample along the thickness direction was 10 mm × 10 mm, and the thickness of the cubic sample was equal to the thickness of the corresponding comparison block. Micro-nano CT was then performed on the cubic samples, and image processing software was used to statistically analyze the internal grain size. The difference in internal grain size obtained from the sample measurements was no greater than 10%. Since the amplitude difference between corresponding points in the ultrasonic images of the two blocks under the same testing conditions was no greater than 5%, the internal grain size difference of the other comparison block was considered to be approximately 10%, and it was used as the comparison block for subsequent grain size testing of the L-shaped TC17 titanium alloy parts.

[0056] Step 3: The L-shaped TC17 titanium alloy part is tested using ultrasonic testing. The clamping method, detection gain value and other detection parameters of the L-shaped TC17 titanium alloy part are the same as those of the above-mentioned comparative test block. The ultrasonic C-scan image C2 of the L-shaped TC17 titanium alloy part is obtained.

[0057] The detected images C1 and C2 are homogenized to obtain the corrected images C1′ and C2′.

[0058] Using the data points of image C1′ as a reference, the corresponding data points in image C2′ are normalized. The normalization method is shown in equation (1).

[0059] D=[20lg(80% / A2)-20lg(80% / A1)] / T (1)

[0060] Where: A1——Amplitude of single-point imaging signal in image C1′ (unit: %);

[0061] A2—Amplitude of single-point imaging signal in image C2′ (unit: %);

[0062] T—Sound path at the signal acquisition point (unit: mm);

[0063] D — Normalized amplitude of the single-point imaging signal in image C2′ (unit: dB)

[0064] The normalized amplitude D is used to reconstruct the detection image C3, and the amplitude and area information of the data points in image C3 are used to evaluate the internal grain size of the L-shaped TC17 titanium alloy part.

Claims

1. An ultrasonic evaluation method for material differences in structures with variable curvature and thickness, characterized in that: The evaluation method employs the following steps for detection and judgment: Step 1: The testing system consists of an ultrasonic flaw detector, an ultrasonic probe, and a comparison test block; Step 2: Based on the ultrasonic detectability of the material, select the appropriate ultrasonic testing method, testing frequency, and probe type to test the comparison test block. Collect the bottom surface reflected echo or transmitted wave signal amplitude of each test part for imaging and record it as image C1. The sensitivity adjustment method during the detection process is as follows: Adjust the gain of the ultrasonic flaw detector so that the maximum value of the amplitude of the imaging acoustic signal displayed on the ultrasonic flaw detector screen is equal to 80%, and ensure that the amplitude of all acquired acoustic signals displayed on the ultrasonic flaw detector screen is within the range of 30% to 80%. If the above requirements cannot be met, the detection method, detection frequency, probe type, water distance parameter should be adjusted, or zonal detection should be adopted until the amplitude of the acoustic signal of the comparative test block ultrasonic detection is within the range of 30% to 80% displayed on the ultrasonic flaw detector screen. Step 3: Use the same ultrasonic testing method, testing frequency, and probe type as the comparison test block testing in Step 2 to test the part to be tested. Collect the bottom surface reflected echo or transmitted wave signal amplitude of each test part of the part to be tested and record it as image C2. Step 4: Perform homogenization on the detected images C1 and C2 to obtain the corrected images C1′ and C2′; Step 5: Using the data points of image C1′ as a reference, normalize the corresponding data points in image C2′. The normalization method is shown in equation (1). D=[20lg(80% / A2)-20lg(80% / A1)] / T (1) In the formula: A1—amplitude of single-point imaging signal in image C1′, unit: %; A2—Amplitude of a single-point imaging signal in image C2′, in %; T—Sound path at the signal acquisition point, unit: mm; D—Normalized amplitude of single-point imaging signal in image C2′, unit: dB; Step 6: Reconstruct the detection image C3 using the normalized amplitude D, and use the amplitude and area information of the data points in image C3 to evaluate the differences in the material of the detected part.

2. The ultrasonic evaluation method for material differences in structures with variable curvature and thickness according to claim 1, characterized in that, In step one, the structural form, curvature change, and thickness change of the comparison test block are the same as those of the tested part. The material composition and uniformity of the comparison test block meet the material technical requirements, and the internal porosity is considered to be zero.

3. The ultrasonic evaluation method for material differences in structures with variable curvature and thickness according to claim 1, characterized in that, The ultrasonic testing methods in step two include two types: ultrasonic pulse reflection testing and ultrasonic pulse penetration testing.

4. The ultrasonic evaluation method for material differences in structures with variable curvature and thickness according to claim 1, characterized in that, In step two, the selection of ultrasonic testing method, testing frequency, and probe type is based on the type of material of the part being tested, material attenuation, part thickness, structural form, and the size of the defect to be tested.

5. The ultrasonic evaluation method for material differences in structures with variable curvature and thickness according to claim 4, characterized in that, For metallic materials, parts with low material attenuation, small thickness, and small required defect size, pulse reflection method, higher detection frequency, and focusing probe are selected for detection. For non-metallic materials, parts with high material attenuation, large thickness, or parts requiring large defect sizes, pulse penetration testing, lower detection frequencies, and flat probes are often used for inspection.

6. The ultrasonic evaluation method for material differences in structures with variable curvature and thickness according to claim 1, characterized in that, In step two, the amplitude of the bottom surface reflected echo or transmitted wave signal of each detection location is collected by selecting the first positive peak value in the bottom surface reflected echo or transmitted wave signal that triggers the imaging signal gate.

7. The ultrasonic evaluation method for material differences in structures with variable curvature and thickness according to claim 1, characterized in that, In step four, the homogenization process for the detected image starts from the initial sampling point. The average value of the sampled values ​​of the four vertices of a quadrilateral with a side length equal to the scanning interval is used to replace the original sampled values ​​of the four vertices of the quadrilateral. This process is repeated to homogenize the data in the image.

8. The ultrasonic evaluation method for material differences in structures with variable curvature and thickness according to claim 1, characterized in that, In step five, the sound path T at the signal acquisition point is calculated based on the sound beam propagation angle, the curvature and thickness of the inspected part, and the waveform change to obtain the propagation path of the sound wave of the first positive peak value of the trigger signal gate, or it can be calculated using sound field simulation software.