Ultrasonic testing device and method for porosity of resin-based fiber-reinforced composites

Abstract

This invention provides an ultrasonic testing device and method for the porosity of resin-based fiber-reinforced composite materials. First, an ultrasonic probe is used to test a comparison test block. The test data is linearly fitted to establish a relationship between the ultrasonic attenuation rate α and the porosity φ. Then, the ultrasonic probe is used to test the workpiece to obtain its attenuation rate α. Finally, based on the aforementioned relationship and the attenuation rate α, the porosity of the workpiece is obtained. This application can perform regional, in-situ porosity testing on the workpiece, effectively detecting the porosity of different parts of large workpieces. It solves the problem in traditional testing methods where local sampling cannot characterize overall non-uniformity, achieving comprehensive testing of integrally molded large-scale structural fiber composite materials.

Description

Technical Field

[0001] This invention relates to the field of ultrasonic nondestructive testing technology, and more specifically, to an ultrasonic testing device and method for the porosity of resin-based fiber-reinforced composite materials. Background Technology

[0002] Resin-based fiber-reinforced composites possess excellent properties such as lightweight, high strength, high rigidity, fatigue resistance, and corrosion resistance. Fiber-reinforced composites have wide applications in large aircraft, wind turbine blades, automotive parts, oil extraction sucker rods, and power transmission cables. With the maturity of key technologies for domestic fiber manufacturing and breakthroughs in low-cost manufacturing techniques, fiber-reinforced composites are increasingly being used in engineering fields. However, there are various molding processes for fiber-reinforced composites, including RTM, vacuum-assisted molding, and prepreg hot pressing. Different processes result in different defect types, mainly including delamination, bubbles, resin deficiency / richness, and fiber wrinkles. Most of these defects can be effectively detected and evaluated using non-destructive testing methods.

[0003] During the manufacturing process of resin-based fiber-reinforced composites, submillimeter pores can occur due to improper process control. The volume percentage of pores within the resin-based fiber-reinforced composite is defined as its porosity. Porosity directly affects the performance and mechanical properties of resin-based fiber-reinforced composites; as porosity increases, mechanical properties decrease significantly. Therefore, strict requirements are placed on porosity in the quality control of resin-based fiber-reinforced composites. For example, the aerospace industry requires a porosity of ≤2% for carbon fiber-reinforced composites. Currently, the main methods for detecting the porosity of resin-based fiber-reinforced composites include:

[0004] 1. Industrial computer tomography (CT) inspection method: by comparing the density of the test specimen, the density is measured and calibrated using an industrial CT with a density resolution of no more than 0.5%. The test specimen is sliced ​​and scanned, and the porosity percentage is calculated by dividing the pore area by the total area on an image analyzer, such as patent CN107860696A.

[0005] 2. The metallographic method specified in GBT3365-2008, on resin-based fiber-reinforced composite materials, measures the percentage of the total pore area to the cross-sectional area of ​​the sample by using an optical microscope, image analyzer, or transparent graph paper. This percentage is the porosity content of the sample.

[0006] 3. The principle of the fiber-reinforced plastic porosity test specified in JCT287-2010 is to measure the density of resin, fiber and fiber-reinforced plastic respectively, then measure the resin content, calculate the theoretical density of fiber-reinforced plastic, and compare the result with the measured density of fiber-reinforced plastic, as in patent CN102426269A.

[0007] 4. Ultrasonic testing method: The porosity of composite materials is characterized by the attenuation rate of ultrasonic waves in the material or the change in ultrasonic velocity. The methods for ultrasonic testing of the porosity of fiber-reinforced composite materials are mainly found in literature records and theoretical studies, and there are currently no publicly available standards or specifications.

[0008] Existing methods for detecting porosity in fiber composites have the following main problems: Methods 1, 2, and 3 are all sample-level testing methods, which cannot achieve in-situ porosity detection and are not feasible for engineering applications. Furthermore, all tests are local sampling tests, and the test data can only represent the sampling location. They cannot characterize the inhomogeneity of different parts of large-scale integrated fiber composite structures. For example, for molded standard parts, it is impossible to sample and analyze the entire part. Only synchronous samples can be used as test specimens, and the test results differ from the product itself. Summary of the Invention

[0009] In view of this, the present invention aims to propose an ultrasonic testing device and method for the porosity of resin-based fiber reinforced composite materials to solve the problems of existing methods for testing the porosity of resin-based fiber reinforced composite materials, which cannot achieve in-situ porosity testing, are not feasible in engineering applications, and are all local sampling tests, which are not suitable for large-scale structural fiber composite materials with integrated molding.

[0010] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0011] An ultrasonic method for detecting the porosity of resin-based fiber-reinforced composite materials, comprising the following steps:

[0012] S1: Prepare a comparison test block. The comparison test block is made using the same process and materials as the workpiece. Proceed to S2.

[0013] S2: Testing the comparison block. Ultrasonic probes with different center frequencies are used to test the comparison block. Before testing, delay wedges are placed on the comparison block to adjust the propagation path and time of the ultrasonic waves. The test data are linearly fitted segment by segment to establish the relationship between the ultrasonic attenuation rate α and the porosity φ for different segments, i.e., α=kf n φ m +b, enter S3;

[0014] S3: Workpiece inspection. An ultrasonic probe is used to inspect the workpiece. Based on the ultrasonic echo center frequencies X1 and X2 and the anisotropy coefficient of the workpiece, the attenuation rate is obtained. Enter S4;

[0015] S4: Substitute the attenuation rate α of the workpiece into α=kf n φ m +b, to obtain the porosity φ of the workpiece;

[0016] Where f is the probe frequency, k and b are constants, the values ​​of n, m, k and b are determined by linear fitting, F is the anisotropy coefficient of the workpiece, C is the propagation speed of the ultrasonic wave in the workpiece, and X1 and X2 are the center frequencies of the ultrasonic echo.

[0017] This method can perform regional, in-situ porosity detection on workpieces, effectively detecting the porosity of different parts of large workpieces. It solves the problem that local sampling tests cannot characterize the overall non-uniformity in traditional detection methods, and realizes comprehensive detection of integrated molded large structural fiber composite materials.

[0018] Furthermore, in S1, three different stages of comparative test blocks were prepared. The porosity of the first stage comparative test block was 0.5% to 1.5%, the porosity of the second stage comparative test block was 1.5% to 3.5%, and the porosity of the third stage comparative test block was 3.5% to 5%.

[0019] This setup covers a wide porosity range, ensuring the comprehensiveness and versatility of the detection method.

[0020] Furthermore, the comparative test blocks for each stage include at least three different porosities.

[0021] Setting multiple porosities within the comparison test block can enhance the reliability of the detection method.

[0022] Furthermore, in S2, three different frequency ultrasonic probes are used to test the comparison test block.

[0023] By using three ultrasonic probes of different frequencies, comprehensive information on pores of different sizes, shapes, and distributions can be obtained, avoiding the omission of some pore information due to detection at a single frequency, thereby improving the reliability of the detection.

[0024] Furthermore, in S2, the thickness of the delay wedge is H2. Where V2 is the propagation speed of ultrasound within the delay wedge, H3 is the thickness of the control block, and V3 is the propagation speed of ultrasound within the control block.

[0025] Regardless of the materials used for the comparison test block and the delay wedge, this setup allows for the determination of the appropriate delay wedge thickness based on their respective ultrasonic propagation speeds, enhancing the adaptability of the testing method to different material combinations.

[0026] Furthermore, in S1, the workpiece is made of resin-based fiber-reinforced composite material, and the thickness of the workpiece and the control block is T, where 4mm ≥ T ≥ 2mm.

[0027] This setup allows ultrasound to fully interact with the pores within the material, generating signal changes that can be effectively detected and analyzed, facilitating the establishment of an accurate relationship between porosity and ultrasound attenuation rate.

[0028] Furthermore, the thickness of the control block was T ± 0.1 mm.

[0029] This setup ensures that the basic parameters are consistent across different comparison blocks, reduces interference caused by individual differences in comparison blocks, and guarantees the consistency of the testing process and results.

[0030] Furthermore, the resin formulation is ethylene resin: initiator: accelerator = 100:1.6:0.3.

[0031] This setup allows the ethylene resin to fully cure under the action of initiators and accelerators, improving the mechanical properties of the composite material and ensuring that the composite material remains structurally stable and is not easily deformed or damaged when subjected to external forces.

[0032] Furthermore, in S2, the delay wedge is made of an isotropic acoustically transparent material.

[0033] The characteristic of isotropic materials is that their physical properties are the same in all directions. When ultrasonic waves propagate in the delay wedge, the propagation speed and attenuation are relatively consistent regardless of the direction, ensuring that the ultrasonic waves can enter the comparison test block or workpiece in a stable state, thereby improving the detection accuracy.

[0034] An ultrasonic testing device for the porosity of a resin-based fiber-reinforced composite material, used in the aforementioned testing method, comprising:

[0035] An ultrasonic probe is used to emit ultrasonic waves toward a test block or workpiece and to receive the ultrasonic signals reflected by the test block or workpiece.

[0036] The delay wedge, ultrasonic probe, and control block are arranged in sequence from top to bottom;

[0037] The calculation module establishes the relationship between the ultrasonic attenuation rate α and the porosity φ based on the ultrasonic signal, and obtains the attenuation rate α and porosity φ of the workpiece.

[0038] The display module is used to display the output results of the calculation module, as well as the user's input settings;

[0039] The control module controls the working status of the calculation module and the display module based on the signals fed back by the ultrasonic probe.

[0040] This detection device is not only simple in structure and easy to operate, but it also enables stable propagation of ultrasonic waves, reduces signal loss and interference, accurately calculates attenuation rate and porosity, and ensures the accuracy of detection results.

[0041] Compared with existing technologies, the ultrasonic testing device and method for the porosity of resin-based fiber-reinforced composite materials described in this invention have the following advantages:

[0042] 1) This method can perform regional and in-situ porosity detection on workpieces, effectively detect the porosity of different parts of large workpieces, and realize comprehensive detection of integrated molded large structural fiber composite materials.

[0043] 2) It basically covers the range of porosity that may occur in the actual production of resin-based fiber reinforced composite materials. For workpieces with different porosity levels, corresponding comparison test blocks can be found for reference testing, ensuring the comprehensiveness and universality of the testing method. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of ultrasonic testing of the porosity of the resin-based fiber-reinforced composite material according to an embodiment of the present invention;

[0045] Figure 2 for Figure 1 A schematic diagram of the ultrasonic wave reflection signal spectrum.

[0046] Explanation of reference numerals in the attached figures:

[0047] 1. Ultrasonic probe; 2. Delay wedge; 3. Workpiece; 4. Ultrasonic signal. Detailed Implementation

[0048] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0049] Example 1

[0050] like Figures 1-2 As shown, in this embodiment, the porosity of the resin-based glass fiber reinforced composite laminate is measured by ultrasonic wave. The reinforcing material is glass fiber, the layup is 0 / 90, the thickness is 5 mm, and the resin used is ethylene resin with a ratio of ethylene resin: initiator: accelerator = 100:1.6:0.3.

[0051] The layup design is 0 / 90, which indicates the layup method of glass fibers in the composite laminate. Here, "0" and "90" represent the angle between the fiber layup direction and the reference axis. 0° means that the fiber direction is parallel to the reference axis, and 90° means that it is perpendicular to the reference axis. This design can make the composite material have more balanced mechanical properties in different directions.

[0052] Workpiece 3 is manufactured using a vacuum-assisted integrated injection molding process. The actual size of workpiece 3 exceeds 6m. Due to the large area of ​​workpiece 3, there may be local unevenness or areas with excessive porosity during the injection process. An ultrasonic probe 1 with a center frequency of 2.25MHz and a probe diameter of 0.5″ is used to detect the porosity of workpiece 3 in different areas.

[0053] The specific testing methods for resin-based glass fiber reinforced composite laminates are as follows:

[0054] S1: Prepare a comparison test block. The comparison test block is made using the same process and materials as workpiece 3.

[0055] S2: For the comparison test block, ultrasonic probes 1 with center frequencies of 1.0MHz, 2.25MHz, and 3.5MHz were used to test the comparison test block. Before testing, a delay wedge 2 was placed on the comparison test block to adjust the propagation path and time of the ultrasonic waves. The ultrasonic echo signals of the comparison test block were collected, and the ultrasonic echo signals were fitted to obtain the relationship between the ultrasonic attenuation rate α and the porosity φ: α = 0.08f 1.2 φ 2 +0.52;

[0056] S3: Inspect workpiece 3. Use ultrasonic probe 1 to inspect workpiece 3. Based on the ultrasonic echo center frequencies X1 and X2 and the anisotropy coefficient of workpiece 3, obtain the attenuation rate. ;

[0057] S4: Substitute the attenuation rate α of workpiece 3 into α=kf n φ m +b, to obtain the porosity φ of workpiece 3;

[0058] Where f is the probe frequency, k and b are constants, the values ​​of n, m, k and b are determined by linear fitting, F is the anisotropy coefficient of workpiece 3, C is the propagation speed of ultrasonic waves in workpiece 3, and X1 and X2 are the center frequencies of ultrasonic echoes.

[0059] In this application, an ultrasonic probe 1 is first used to test the comparison test block, and the test data is linearly fitted to establish the relationship between the ultrasonic attenuation rate α and the porosity φ. Then, the ultrasonic probe 1 is used to test the workpiece 3 to obtain the attenuation rate α of the workpiece 3. Finally, the porosity of the workpiece 3 is obtained according to the aforementioned relationship and the attenuation rate α of the workpiece. Since the comparison test block and the workpiece 3 are made with the same process and materials, the comparison test block can simulate the actual situation of the workpiece 3 to the greatest extent, making the test results more consistent with the true porosity of the workpiece 3 and reducing the error caused by differences in materials and processes. This method can perform regional and in-situ porosity detection on the workpiece 3, and can effectively detect the porosity of different parts of large workpieces. It solves the problem that local sampling tests cannot characterize the overall non-uniformity in traditional detection methods, and realizes comprehensive detection of integrated molded large structural fiber composite materials, which is suitable for engineering inspection.

[0060] Preferably, not limited to the ultrasonic probe 1 of these frequencies in S2.

[0061] Preferably, a broadband ultrasonic probe with a bandwidth of ≥80% is used.

[0062] As a preferred example of this application, in S1, three different stages of comparative test blocks are prepared respectively. The porosity of the first stage comparative test block is 0.5% to 1.5%, the porosity of the second stage comparative test block is 1.5% to 3.5%, and the porosity of the third stage comparative test block is 3.5% to 5%.

[0063] Specifically, this setup covers a wide porosity range, basically encompassing the porosity range that may occur in actual production of resin-based fiber-reinforced composite materials. For workpieces 3 with different porosity levels, corresponding comparison test blocks can be found for reference testing, ensuring the comprehensiveness and universality of the testing method, reducing testing errors, and at the same time realizing quantitative analysis of the porosity of composite materials in the range of 0.5% to 5%.

[0064] As a preferred example of this application, the comparative test blocks for each stage include at least three different porosities.

[0065] Specifically, increasing the diversity of porosity in the comparison test block can reduce errors caused by a single or small number of porosity samples. If the comparison test block has only one porosity, any manufacturing defects in the comparison test block will affect the reliability of the test results. Setting multiple porosities in the comparison test block can enhance the reliability of the test method.

[0066] Preferably, the porosity of the first stage is selected as 0.5%, 1%, or 1.4%, respectively, but it is not limited to these data.

[0067] As a preferred example of this application, in S2, the thickness of the delay wedge 2 is H2. Where V2 is the propagation speed of the ultrasonic wave within the delay wedge 2, H3 is the thickness of the comparison test block, and V3 is the propagation speed of the ultrasonic wave within the comparison test block.

[0068] Specifically, since different materials have different effects on the propagation speed of ultrasonic waves, this formula takes these factors into account. Regardless of the materials used for the comparison test block and the delay wedge 2, the appropriate thickness of the delay wedge 2 can be determined based on their respective ultrasonic wave propagation speeds. This enhances the adaptability of the detection method to different material combinations and enables the detection method to play an effective role in a variety of practical application scenarios.

[0069] When inspecting workpiece 3, it is also necessary to use delay wedge 2.

[0070] As a preferred example of this application, in S1, the workpiece 3 is made of resin-based fiber-reinforced composite material, and the thickness of the workpiece 3 and the comparative test block is T, 4mm≥T≥2mm.

[0071] Specifically, a thickness of 2mm to 4mm allows ultrasound to have sufficient penetration depth and attenuation when propagating in the material. If the material is too thin, the change in the ultrasonic signal is not obvious, making it difficult to accurately detect porosity. If the material is too thick, the signal will be excessively attenuated, which will also affect the detection accuracy. This setting allows ultrasound to fully interact with the pores in the material, generating signal changes that can be effectively detected and analyzed, making it easier to establish an accurate relationship between porosity and ultrasonic attenuation rate.

[0072] As a preferred example of this application, the thickness of the comparative test block is T±0.1mm.

[0073] Specifically, this setup ensures that the basic parameters of different comparison test blocks are consistent, which helps to reduce interference caused by individual differences in comparison test blocks when establishing the relationship between ultrasonic attenuation rate and porosity, ensuring the consistency of the testing process and results, and facilitating analysis and judgment by testing personnel.

[0074] Preferably, the thickness of the comparison test block is no greater than the thickness of a single layer of carbon fiber fabric. Considering that carbon fiber fabric is a reinforcement of composite materials, its single-layer thickness is relatively stable. Using the thickness of a single layer of carbon fiber fabric as a reference can more accurately control the tolerance of the thickness of the comparison test block, ensuring that the comparison test block is closer to the workpiece in terms of structure and performance, and improving the reliability of the test results.

[0075] As a preferred example of this application, in S2, the delay wedge 2 is made of an isotropic acoustically transparent material.

[0076] Specifically, isotropic materials have the same physical properties in all directions. When ultrasonic waves propagate within the delay wedge, the propagation speed and attenuation are relatively consistent regardless of the direction. The propagation path and waveform of ultrasonic waves will not change due to differences in the material's orientation, ensuring that ultrasonic waves can enter the comparison test block or workpiece 3 in a stable state, thereby improving the detection accuracy.

[0077] This application also provides an ultrasonic testing device for the porosity of resin-based fiber-reinforced composite materials, used in the aforementioned testing method, comprising:

[0078] Ultrasonic probe 1 is used to emit ultrasonic waves to the comparison test block or workpiece 3 and to receive the ultrasonic wave signal 4 reflected by the comparison test block or workpiece 3.

[0079] The delay wedge 2, ultrasonic probe 1, delay wedge 2 and control test block are arranged in sequence from top to bottom, with good coupling between them and maintaining verticality.

[0080] The calculation module establishes the relationship between the ultrasonic attenuation rate α and the porosity φ based on the ultrasonic signal 4, and obtains the attenuation rate α and porosity φ of the workpiece 3.

[0081] The display module is used to display the output results of the calculation module, as well as the user's input settings;

[0082] The control module controls the working status of the calculation module and the display module based on the signal fed back by the ultrasonic probe 1.

[0083] Specifically, this detection device is not only simple in structure and easy to operate, but it also enables stable propagation of ultrasonic waves, reduces signal loss and interference, accurately calculates attenuation rate and porosity, and ensures the accuracy of detection results.

[0084] Preferably, it also includes a power supply module for providing power to the ultrasonic probe 1, the computing module, the display module, and the control module.

[0085] Preferably, the ultrasonic probe 1 is controlled to emit ultrasonic signals 4, and the ultrasonic signals 4 reflected from the upper surface of the comparison test block or workpiece 3 and the ultrasonic signals 4 reflected from the lower surface of the comparison test block or workpiece 3 are collected.

[0086] Table 1 shows the porosity data measured in Example 1 and the porosity data measured by metallographic method.

[0087] Table 1:

[0088] Measurement location Ultrasonic testing porosity data (%) Metallographic verification of porosity data (%) 1 1.22 1.26 2 1.35 1.34 3 1.26 1.28 4 0.55 0.61 5 1.82 1.85

[0089] As shown in Table 1, the ultrasonic testing method for the porosity of resin-based fiber-reinforced composite materials described in this application is not only accurate but also superior to the traditional metallographic method.

[0090] In summary, the ultrasonic testing device and method for the porosity of resin-based fiber-reinforced composite materials described in this application have the following advantages: 1) This method can perform regional, in-situ porosity testing on workpiece 3, effectively detecting the porosity of different parts of large workpieces, and realizing comprehensive testing of integrated molded large-structure fiber composite materials; 2) It basically covers the porosity range that may occur in actual production of resin-based fiber-reinforced composite materials. For workpieces with different porosity levels, corresponding comparison test blocks can be found for reference testing, ensuring the comprehensiveness and universality of the testing method; 3) Setting multiple porosities in the comparison test block can enhance the reliability of the testing method.

[0091] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. An ultrasonic method for detecting the porosity of resin-based fiber-reinforced composite materials, characterized in that, Including the following steps: S1: Make a comparison test block. The comparison test block and the workpiece (3) are made using the same process and materials. Proceed to S2. S2: Test the comparison block. Use ultrasonic probes (1) with different center frequencies to test the comparison block respectively. Before the test, set a delay wedge (2) on the comparison block to adjust the propagation path and time of the ultrasonic wave. Perform linear fitting on the test data in segments to establish the relationship between the ultrasonic wave attenuation rate α and the porosity φ in different segments, that is, α=kf n φ m +b, enter S3; S3: Inspect workpiece (3). Use ultrasonic probe (1) to inspect workpiece (3). Based on the ultrasonic echo center frequencies X1 and X2 and the anisotropy coefficient of workpiece (3), obtain the attenuation rate. Enter S4; S4: Substitute the attenuation rate α of workpiece (3) into α=kf n φ m +b, to obtain the porosity φ of workpiece (3); Where f is the probe frequency, k and b are constants, the values ​​of n, m, k and b are determined by linear fitting, F is the anisotropy coefficient of the workpiece (3), C is the propagation speed of ultrasonic waves in the workpiece (3), and X1 and X2 are the center frequencies of ultrasonic echoes.

2. The ultrasonic testing method for the porosity of resin-based fiber-reinforced composite materials according to claim 1, characterized in that, In S1, three different stages of comparative test blocks were prepared. The porosity of the first stage comparative test block was 0.5% to 1.5%, the porosity of the second stage comparative test block was 1.5% to 3.5%, and the porosity of the third stage comparative test block was 3.5% to 5%.

3. The ultrasonic testing method for the porosity of resin-based fiber-reinforced composite materials according to claim 2, characterized in that, Each stage of the comparative test block includes at least three different porosities.

4. The ultrasonic testing method for the porosity of resin-based fiber-reinforced composite materials according to claim 1, characterized in that, In S2, three different frequency ultrasonic probes (1) were used to test the comparison test block respectively.

5. The ultrasonic testing method for the porosity of resin-based fiber-reinforced composite materials according to claim 1, characterized in that, In S2, the thickness of the delay wedge (2) is H2. Where V2 is the propagation speed of ultrasound in the delay wedge (2), H3 is the thickness of the comparison test block, and V3 is the propagation speed of ultrasound in the comparison test block.

6. The ultrasonic testing method for the porosity of resin-based fiber-reinforced composite materials according to claim 1, characterized in that, In S1, the workpiece (3) is made of resin-based fiber-reinforced composite material, and the thickness of the workpiece (3) and the control block is T, 4mm≥T≥2mm.

7. The ultrasonic testing method for the porosity of resin-based fiber-reinforced composite materials according to claim 6, characterized in that, The thickness of the control block was T ± 0.1 mm.

8. The ultrasonic testing method for the porosity of resin-based fiber-reinforced composite materials according to claim 6, characterized in that, The resin formulation is ethylene resin: initiator: accelerator = 100:1.6:0.

3.

9. The ultrasonic testing method for the porosity of resin-based fiber-reinforced composite materials according to claim 1, characterized in that, In S2, the delay wedge (2) is made of an isotropic acoustic material.

10. An ultrasonic testing device for the porosity of a resin-based fiber-reinforced composite material, used in the testing method according to any one of claims 1 to 9, characterized in that, include: An ultrasonic probe (1) is used to emit ultrasonic waves to the comparison test block or workpiece (3) and receive ultrasonic signals (4) reflected by the comparison test block or workpiece (3). The delay wedge (2), ultrasonic probe (1), delay wedge (2) and comparison test block are arranged in sequence from top to bottom; The calculation module establishes the relationship between ultrasonic attenuation rate α and porosity φ based on ultrasonic signal (4), and obtains the attenuation rate α and porosity φ of workpiece (3); The display module is used to display the output results of the calculation module, as well as the user's input settings; The control module controls the working status of the calculation module and the display module based on the signal fed back by the ultrasonic probe (1).

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