Complex structure blade CT penetration rate characterization method

Abstract

The embodiment of the invention provides a complex structure blade CT penetration rate characterization method, and relates to the field of engine turbine blades. The objective of the invention is to improve the problem of lack of effective transmissivity measurement methods for complex structure blade CT detection. The method comprises the following steps: fixing a to-be-detected blade on a CT detection turntable to obtain an initial position; taking the initial position as a starting point, rotating the CT detection turntable, executing CT detection, and obtaining the transmissivity of the to-be-detected blade at different rotation angles; and according to the transmissivity fitting curve of different rotation angles, reading the minimum transmissivity on the fitting curve as the minimum transmissivity of the blade. According to the method, different angle transmittances are read, the minimum transmittances are obtained according to the different angle transmittances and a fitting curve, and finally real transmittances characterization of complex structure blade CT detection is achieved, so that the defect that the complex structure blade CT detection lacks an effective transmittances measuring method is overcome, and real transmittances characterization of complex structure blade CT detection is achieved. Wide application prospects and popularization values are realized.

Description

Technical Field

[0001] This invention relates to the field of engine turbine blades, and more specifically, to a method for characterizing the CT penetration rate of blades with complex structures. Background Technology

[0002] Complex blade structures, such as turbine blades, are critical components in aero-engines and gas turbines. During manufacturing and service, they require non-destructive testing to ensure they are free of defects and guarantee operational safety. CT (Computed Tomography) testing offers high density contrast, is sensitive to density variations and internal defects, and provides intuitive results, leading to its increasing application in the detection of internal defects in aero-engine and gas turbine blades.

[0003] Due to the high density, complex profile, and large penetration thickness of turbine blades, the penetration thickness varies along different paths during CT inspection. Furthermore, the complex internal structure easily generates X-ray scattering, leading to beam hardening and scattering artifacts, which reduce image quality and affect defect detection capabilities. Therefore, blade penetration capability (transmittance) is an important indicator for evaluating CT image quality. ASTM E1441 states that a transmittance of 13% yields good image contrast and quality; however, this standard does not provide a method for measuring transmittance. Because of the complex profile and internal cavity structure of turbine blades, penetration results vary depending on the angle at which the blade is penetrated. Additionally, transmittance test results are related to the distance between the sample and the X-ray source and detector, resulting in different outcomes depending on the placement position. Therefore, it is impossible to accurately characterize the actual transmittance under the final inspection process conditions. Summary of the Invention

[0004] The following provides a brief overview of one or more aspects to offer a basic understanding of them. This overview is not an exhaustive summary of all conceived aspects, nor is it intended to identify key or decisive elements of all aspects, nor to define the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form to prepare for the more detailed descriptions that follow.

[0005] The present invention aims to provide, for example, a method for characterizing the CT transmittance of complex-structured blades, which can improve the problem of the lack of effective methods for measuring transmittance in CT detection of complex-structured blades.

[0006] The embodiments of the present invention can be implemented as follows:

[0007] Embodiments of the present invention provide a method for characterizing the CT penetration rate of complex-structured blades, comprising:

[0008] The blade to be tested is fixed on the CT inspection turntable to obtain the initial position; starting from the initial position, the CT inspection turntable is rotated to perform CT inspection and obtain the transmittance of the blade at different rotation angles; based on the transmittance at different rotation angles, a curve is fitted, and the minimum transmittance on the fitted curve is read as the minimum transmittance of the blade.

[0009] In addition, the CT penetration characterization method for complex-structured blades provided in the embodiments of the present invention may also have the following additional technical features:

[0010] Optionally, the step of rotating the CT detection turntable from the initial position to perform CT detection and obtain the transmittance of the blade under test at different rotation angles includes: starting from the initial position, rotating the CT detection turntable clockwise and counterclockwise multiple times with a first angle as the step, reading the maximum and minimum gray values ​​of the first frame area of ​​the blade under test at each rotation angle position, calculating the first transmittance corresponding to the rotation angle position by repeatedly reading the maximum and minimum gray values ​​at the same rotation angle position, and taking the rotation angle position with the minimum first transmittance as the minimum illumination angle; starting from the minimum illumination angle, rotating the CT detection turntable clockwise and counterclockwise multiple times within a set angle range with a second angle as the step, reading the maximum and minimum gray values ​​of the second frame area of ​​the blade under test at each rotation angle position, and calculating the second transmittance corresponding to the rotation angle position by repeatedly reading the maximum and minimum gray values ​​at the same rotation angle position;

[0011] The step of fitting a curve based on the transmittance at different rotation angles and reading the minimum transmittance from the fitted curve as the minimum transmittance of the blade includes: fitting a curve using the second transmittance and the rotation angle corresponding to the second transmittance, and reading the minimum second transmittance from the fitted curve as the minimum transmittance of the blade.

[0012] Optionally, before the step of fitting a curve using the second transmittance and the rotation angle corresponding to the second transmittance, and reading the minimum second transmittance as the minimum transmittance of the leaf on the fitted curve, the step of rotating the CT detection turntable clockwise and counterclockwise multiple times within a set angle range, starting from the minimum illumination angle, reading the maximum and minimum gray values ​​of the second frame area of ​​the leaf under test at each rotation angle position, and calculating the second transmittance corresponding to the rotation angle position by repeatedly reading the maximum and minimum gray values ​​at the same rotation angle position, is performed at least once.

[0013] Optionally, the step of fixing the leaf to be tested on the CT inspection turntable to obtain the initial position includes,

[0014] The blade to be tested is fixed on the three-jaw chuck of the CT inspection turntable using a fixture; the blade to be tested is set to a preset condition, and the rotation angle θ of the mechanical axis of the CT inspection turntable is set. R =0° is the zero-degree position; rotating the CT inspection turntable, with the blade under test in the position of minimum transmittance estimation, the rotation angle θ of the mechanical axis of the CT inspection turntable. R =θ-start is the initial position.

[0015] Optionally, the blade to be tested is a turbine blade;

[0016] The blade to be tested is set to a preset condition, and the rotation angle θ of the mechanical axis of the CT detection turntable is... R =0° is the zero-degree position. The steps include: with the extension line of the exhaust edge plate side of the turbine blade perpendicular to the X-ray source end face, the rotation angle θ of the mechanical axis of the CT detection turntable is measured. R =0° is the zero-degree position;

[0017] The rotating CT inspection turntable, when the blade under test is in the position of minimum transmittance estimation, has a rotation angle θ of its mechanical axis. R =θ-start is the initial position step, which includes rotating the CT detection turntable until the intake side of the turbine blade is closest to the X-ray source and the exhaust side of the turbine blade is closest to the detector. At this time, the rotation angle θ of the mechanical axis of the CT detection turntable is... R =θ-start is the initial position.

[0018] Optionally, the blade to be tested is a turbine blade, and the tooling is provided with a first slot and a second slot. The first slot is located below the second slot. The first slot is used to wrap the tenon of the turbine blade, and the second slot is used to engage and fix with the edge plate of the turbine blade. The tooling is used to fix the blade to be tested on the three-jaw chuck of the CT inspection turntable so that the blade to be tested maintains a set angle with the CT inspection platform.

[0019] Optionally, the tooling includes a frustum and a mounting base, the mounting base being fixed to the frustum, the frustum being used to fix it to the three-jaw chuck of the CT inspection turntable, and the mounting base having a first slot and a second slot, the second slot being a parallelogram.

[0020] Optionally, the step of fixing the leaf to be tested on the CT inspection turntable to obtain the initial position further includes:

[0021] The steps following the step of fixing the blade to be tested onto the three-jaw chuck of the CT inspection turntable using tooling are as follows: setting the inspection parameters according to the CT inspection process parameters of the blade to be tested, and adjusting the distance between the X-ray source and the sample and between the sample and the detector; performing bright and dark field correction on the CT detector, and mechanical axis center correction.

[0022] Optionally, the formula for calculating the first transmittance corresponding to the rotation angle position by repeatedly reading the maximum and minimum grayscale values ​​at the same rotation angle position includes:

[0023] Among them, T θi Let θ be the i-th angle. i Corresponding transmittance, T θi-1min T θi-2min T iθ-3min ,…,T θi-kmin The i-th angle θ i The minimum gray level measured k times; T θi-1max T θi-2max T θi-3max ,…,T θi-kmax The i-th angle θ i The maximum grayscale value after k measurements.

[0024] Optionally, the set angle range includes a minimum transmission angle of ±2°.

[0025] The beneficial effects of the CT penetration rate characterization method for complex-structured blades according to embodiments of the present invention include, for example:

[0026] A method for characterizing the CT transmittance of complex-structured blades includes fixing the blade to be tested on a CT detection turntable to obtain an initial position; rotating the CT detection turntable from the initial position to perform CT detection and obtaining the transmittance of the blade at different rotation angles; fitting a curve based on the transmittance at different rotation angles, and reading the minimum transmittance from the fitted curve as the minimum transmittance of the blade.

[0027] The system reads transmittance data from different angles; fits curves based on the transmittance data from different angles to obtain the minimum transmittance; and finally achieves true transmittance characterization for CT detection of complex structure blades. This overcomes the shortcomings of traditional CT detection of complex structure blades, which lacks an effective method for measuring transmittance. It can achieve true transmittance characterization for CT detection of complex structure blades and has broad application prospects and promotional value. Attached Figure Description

[0028] The above-described features and advantages of the present invention will be better understood after reading the following detailed description of embodiments of the present disclosure in conjunction with the accompanying drawings. In the drawings, components are not necessarily drawn to scale, and components having similar related characteristics or features may have the same or similar reference numerals.

[0029] Figure 1 A flowchart illustrating the CT penetration rate characterization method for complex structure blades provided in this embodiment of the invention;

[0030] Figure 2 A schematic diagram of the first tooling structure provided in an embodiment of the present invention;

[0031] Figure 3 This is a schematic diagram of the second tooling structure provided in an embodiment of the present invention;

[0032] Figure 4 A schematic diagram of obtaining the frame region of the blade to be tested in the CT penetration rate characterization method for complex structure blades provided in an embodiment of the present invention;

[0033] Figure 5 The fitting curve of the second transmittance versus the rotation angle in the CT transmittance characterization method for complex structure blades provided in this embodiment of the invention;

[0034] Figure 6 A flowchart of a method for characterizing the CT penetration rate of complex-structured blades provided in an embodiment of the present invention.

[0035] Icons: 100 - Tooling; 110 - Frustum; 120 - Card slot; 121 - First card slot; 122 - Second card slot. Detailed Implementation

[0036] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. It should be noted that the aspects described below with reference to the accompanying drawings and specific embodiments are merely exemplary and should not be construed as limiting the scope of protection of the present invention in any way.

[0037] In the description of this invention, it should be noted that if terms such as "upper," "lower," "inner," "outer," or "vertical" appear, the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this invention is usually placed when in use, and does not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0038] At the same time, it should be noted that the terms "first" and "second" are used only for distinguishing descriptions and should not be interpreted as indicating or implying relative importance.

[0039] In the description of this invention, it should also be noted that, unless otherwise explicitly specified or limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, an integral connection, or a detachable connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or a connection within two components, etc. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0040] The following is combined Figures 1 to 6The CT penetration rate characterization method for complex structure blades provided in this embodiment is described in detail.

[0041] Please refer to Figure 1 The present invention provides a method for characterizing the CT penetration rate of complex-structured blades, comprising:

[0042] Step S1: Fix the leaf to be tested on the CT inspection turntable to obtain the initial position;

[0043] Step S2: Starting from the initial position, rotate the CT detection turntable to perform CT detection and obtain the transmittance of the blade under test at different rotation angles.

[0044] Step S3: Based on the transmittance at different rotation angles, fit the curve, and read the minimum transmittance from the fitted curve as the minimum transmittance of the blade.

[0045] It should be noted that turbine blades are crucial components of the turbine section in engines or gas turbines. High-speed airflow drives the compressor or turbine blades to perform work, providing power to the engine or gas turbine. In this embodiment, a turbine blade is used as the blade under test. CT (x-ray computed tomography) is a computer-aided imaging method. In CT, a CT turntable is positioned between the X-ray source and the detector, and the blade under test is fixed on the turntable. Penetration ratio refers to the ratio of the radiation dose measured when an object is placed in the X-ray beam to when the beam is removed, under specific testing conditions. Characterization is a method for quantitatively describing (representing) information such as the size of defects.

[0046] First, a testing fixture 100 is prepared for blades with different configurations, and the testing reference is marked. Then, the CT system is calibrated. Next, the testing parameters are set according to the actual process of the blade to be tested, and the transmittance test is carried out to read and calculate the transmittance data at different angles. Based on the transmittance data at different angles, a curve is fitted to obtain the minimum transmittance. Finally, the true transmittance characterization of CT detection of blades with complex structures is achieved.

[0047] Reference Figure 1 , Figure 4 and Figure 5 In this embodiment, step S2 involves rotating the CT detection turntable from the initial position to perform CT detection and obtaining the transmittance of the blade under test at different rotation angles.

[0048] Step S21: Starting from the initial position, rotate the CT detection turntable clockwise and counterclockwise multiple times with the first angle as the step. Read the maximum and minimum gray values ​​of the first frame area of ​​the blade under test at each rotation angle position. Calculate the first transmittance corresponding to the rotation angle position by reading the maximum and minimum gray values ​​of the gray values ​​multiple times at the same rotation angle position. Take the rotation angle position with the minimum first transmittance as the minimum illumination angle.

[0049] Step S22: Starting from the minimum transmission angle, within the set angle range, the CT detection turntable is rotated clockwise and counterclockwise multiple times in increments of the second angle. The maximum and minimum gray values ​​of the second frame area of ​​the leaf under test are read at each rotation angle position. The second transmittance corresponding to the rotation angle position is calculated by reading the maximum and minimum gray values ​​of the gray values ​​multiple times at the same rotation angle position.

[0050] Step S3: Based on the transmittance at different rotation angles, fit the curve, and read the minimum transmittance from the fitted curve. The minimum transmittance of the blade includes:

[0051] Step S31: Fit the curve using the second transmittance and the rotation angle corresponding to the second transmittance, and read the minimum second transmittance from the fitted curve as the minimum transmittance of the blade.

[0052] In step S1, the position of the blade to be tested on the CT detection turntable is fixed. During the subsequent rotation, the position of the blade to be tested relative to the CT detection turntable remains unchanged. The obtained initial position is used as the initial position in step S21, and the minimum radiographic angle obtained in step S21 is used as the starting position in step S22.

[0053] In step S21, rotation is performed with a first angle as the step angle. At each rotation angle position, a maximum gray value and a minimum gray value are read from the first frame selection area of ​​the blade under test. After multiple rotations, multiple maximum and minimum gray values ​​can be obtained at the same rotation angle position. The first transmittance at that rotation angle position is calculated using the multiple maximum and minimum gray values. In this way, multiple first transmittances corresponding to multiple rotation angle positions are calculated. The rotation angle corresponding to the smallest first transmittance among the multiple first transmittances is selected as the minimum illumination angle. Refer to Table 1.

[0054] Table 1. Calculation results of grayscale, noise, and minimum identifiable defect for a certain cross section.

[0055]

[0056] In step S22, the second angle is used as the step angle. The second angle is not equal to the first angle, and the second angle is less than the first angle. Starting from the minimum transmission angle, step S21 is repeated to obtain multiple second transmittances, as shown in Table 2. Multiple second transmittances and their corresponding rotation angles are fitted with curves. The minimum second transmittance is read from the fitted curves, as shown in Table 2. Figure 5 .

[0057] Table 2

[0058]

[0059]

[0060] Step S21 performs coarse selection of minimum transmittance, step S22 further refines the minimum transmittance, and step S31 reads the minimum transmittance through fitting curve. This can achieve the characterization of the true transmittance of CT detection of complex structured blades, with a detection accuracy of less than 0.1%, which has great application prospects and promotion value.

[0061] In this embodiment, before step S31, which involves fitting a curve using the second transmittance and the rotation angle corresponding to the second transmittance, and reading the minimum second transmittance as the minimum transmittance of the leaf on the fitted curve, step S22 involves rotating the CT detection turntable multiple times clockwise and multiple times counterclockwise within a set angle range, starting from the minimum illumination angle, and reading the maximum and minimum gray values ​​of the second frame area of ​​the leaf under test at each rotation angle position. The step of calculating the second transmittance corresponding to the rotation angle position by repeatedly reading the maximum and minimum gray values ​​at the same rotation angle position is performed at least once.

[0062] The multiple second transmittances obtained in step S22 can be used to select the rotation angle corresponding to the smallest second transmittance as the next minimum illumination angle. Step S22 is repeated to obtain a new minimum illumination angle. Step S22 is executed at least once, and can be repeated two or three times to obtain the final minimum illumination angle.

[0063] In this embodiment, step S21, the formula for calculating the first transmittance corresponding to the rotation angle position by repeatedly reading the maximum and minimum gray values ​​at the same rotation angle position includes:

[0064] Among them, T θi Let θ be the i-th angle. i Corresponding transmittance, T θi-1min T θi-2min T iθ -3min, ...,T θi-kmin The i-th angle θi The minimum gray level measured k times; T θi-1max T θi-2max T θi-3max ,…,T θi-kmax The i-th angle θ i The maximum grayscale value is measured k times. The second transmittance is also calculated using this formula.

[0065] At each rotation angle position, a minimum and maximum gray value are read. For multiple rotations, multiple minimum and maximum gray values ​​are read. Then, the first transmittance corresponding to a rotation angle is calculated using multiple minimum and maximum gray values.

[0066] It should be noted that in step S22, the step of calculating the second transmittance corresponding to the rotation angle position by repeatedly reading the maximum and minimum grayscale values ​​at the same rotation angle position also uses the above calculation formula.

[0067] In this embodiment, the set angle range in step S22 includes the minimum illumination angle ±2°. This angle range can also be selected manually, choosing a range within the clockwise and counterclockwise directions from the minimum illumination angle.

[0068] Reference Figure 5 In this embodiment, step S31, which involves fitting a curve using the second transmittance and the rotation angle corresponding to the second transmittance, and reading the minimum second transmittance as the minimum transmittance of the blade from the fitted curve, includes fitting a curve with multiple second transmittances as the vertical axis and multiple rotation angles corresponding to the second transmittances as the horizontal axis, and reading the minimum second transmittance as the minimum transmittance of the blade from the fitted curve.

[0069] In this embodiment, step S1, which involves fixing the leaf to be tested on the CT inspection turntable to obtain the initial position, includes the following steps:

[0070] Step S11: Fix the blade to be tested onto the three-jaw chuck of the CT inspection turntable using tooling 100;

[0071] Step S12: Set the blade under test to be in a preset condition, and set the rotation angle θ of the mechanical axis of the CT detection turntable. R =0° is the zero-degree position;

[0072] Step S13: Rotate the CT inspection turntable. When the blade under test is in the position of minimum transmittance estimation, the rotation angle θ of the mechanical axis of the CT inspection turntable is... R =θ-start is the initial position.

[0073] The fixture 100 is designed according to the position of the blade to be tested relative to the CT inspection turntable, ensuring that the blade to be tested is fixed on the fixture 100. After the fixture 100 is fixed on the CT inspection turntable, the position of the blade to be tested relative to the CT inspection turntable is fixed, ensuring that the rotation reference is the same throughout the entire process.

[0074] In this embodiment, the blade to be tested is a turbine blade;

[0075] Step S12: Set the blade under test to be in a preset condition, and set the rotation angle θ of the mechanical axis of the CT detection turntable. R =0° is the zero-degree position. The steps include: step S121, when the extension line of the exhaust edge plate side of the turbine blade is perpendicular to the X-ray source end face, the rotation angle θ of the mechanical axis of the CT detection turntable is measured. R =0° is the zero-degree position;

[0076] Step S13: Rotate the CT inspection turntable. When the blade under test is in the position of minimum transmittance estimation, the rotation angle θ of the mechanical axis of the CT inspection turntable is... R =θ-start is the initial position step, which includes step S131, rotating the CT detection turntable until the air intake side of the turbine blade is closest to the X-ray source and the exhaust side of the turbine blade is closest to the detector, at which time the rotation angle θ of the mechanical axis of the CT detection turntable is... R =θ-start is the initial position.

[0077] In this embodiment, the CT inspection turntable is positioned between the X-ray source and the detector. The "preset condition" refers to "the extension line of the exhaust edge plate side of the turbine blade is perpendicular to the X-ray source end face." Using the exhaust edge plate side of the turbine blade as a reference, the extension line of this reference is made perpendicular to the X-ray source end face, and the rotational position of the mechanical axis (R-axis) is set to θ. R =0°. Rotate the R-axis clockwise until the turbine blade inlet side is closest to the radiation source and the exhaust side is closest to the detector. Record the R-axis rotation angle θ at this point. R =θ-start is the initial position.

[0078] In this embodiment, step S1, which involves fixing the leaf to be tested on the CT inspection turntable to obtain the initial position, further includes:

[0079] The steps following the step of fixing the blade to be tested onto the three-jaw chuck of the CT inspection turntable using tooling 100 are as follows: setting the inspection parameters according to the CT inspection process parameters of the blade to be tested, and adjusting the distance between the X-ray source and the sample and between the sample and the detector; performing bright and dark field correction on the CT detector, as well as mechanical axis center correction.

[0080] When performing CT inspections on blades with complex structures (such as turbine blades), the inspection parameters must be set according to the specified inspection process parameters, and the distances between the X-ray source and the sample, and between the sample and the detector, must be precisely adjusted. The source-to-subject distance (SSD) has a significant impact on transmittance and image quality. Based on the specified process parameters or experimental requirements, mechanical devices (such as lifting platforms, rotating arms, etc.) are used to precisely adjust the distance between the X-ray source and the blade sample. Similarly, the subject-to-image detector distance (SID) also needs to be adjusted according to the process parameters. Brightness-dark field correction aims to eliminate sensitivity inconsistencies between detector channels caused by manufacturing differences, aging, or other factors. These inconsistencies can lead to artifacts or uneven brightness in the image, affecting the accuracy of defect detection. Mechanical axis center correction aims to ensure precise alignment between the rotation center and the detector center during the CT scan.

[0081] Reference Figure 2 and Figure 3 In this embodiment, the tooling 100 is provided with a first slot 121 and a second slot 122. The first slot 121 is located below the second slot 122. The blade to be tested is a turbine blade. The first slot 121 is used to wrap the tenon of the turbine blade, and the second slot 122 is used to engage and fix with the edge plate of the turbine blade. The tooling 100 is used to fix the blade to be tested on the three-jaw chuck of the CT detection turntable so that the blade to be tested maintains a set angle with the CT detection platform.

[0082] "Set angle" refers to the angular relationship between the blade under test and the CT inspection turntable. This setting is based on actual experimental needs. In other words, fixture 100 can be structurally designed according to the set angle requirements, ensuring that the blade under test maintains the set angle during the rotation of the CT inspection turntable. Fixture 100 is made of plexiglass or other thermoplastic materials, ensuring dimensional stability and resistance to deformation. Fixture 100 has two slots: the first slot 121 encloses the tenon of the turbine blade, securing it; the second slot 122 engages with the blade rim plate, securing the rim plate and preventing circumferential slippage of the blade.

[0083] Reference Figure 3 In this embodiment, the tooling 100 includes a frustum 110 and a chuck 120. The chuck 120 is fixed on the frustum 110. The frustum 110 is used to fix on the three-jaw chuck of the CT detection turntable. The chuck 120 has a first chuck groove 121 and a second chuck groove 122. The second chuck groove 122 is a parallelogram.

[0084] The second slot 122 is a parallelogram slot that mates with the blade rim plate to fix the rim plate and prevent the blade from sliding circumferentially. Alternatively, in other embodiments, the tooling 100 is cylindrical, and the cylindrical tooling 100 is provided with the first slot 121 and the second slot 122.

[0085] Reference Figure 6 According to the CT penetration rate characterization method for complex structure blades provided in this embodiment, the working principle of the CT penetration rate characterization method for complex structure blades includes:

[0086] 1. Load the blade into fixture 100 and clamp fixture 100 onto the three-jaw chuck of the CT inspection turntable.

[0087] 2. Set the detection parameters according to the specified CT detection process parameters for the leaf to be tested, and adjust the distance between the X-ray source and the sample and between the sample and the detector. Maintain these settings during subsequent testing.

[0088] 3. Perform bright and dark field correction on the CT detector, as well as mechanical axis center correction.

[0089] 4. Rough selection of radiographic angle, the specific steps are as follows:

[0090] 1) Using the side edge of the turbine blade exhaust edge plate as a reference, make the extension line of this reference perpendicular to the end face of the radiation source, and set the rotation position of the mechanical axis (R axis) to θR = 0°.

[0091] 2) Rotate the R-axis clockwise so that the turbine blade inlet side is closest to the radiation source and the exhaust side is closest to the detector. Record the rotation angle θR = θ - start at this time. Starting from this position, rotate clockwise and counterclockwise by the first angle step (denoted as Δθ1) respectively. Rotate clockwise and counterclockwise N times respectively. After each rotation, read and record the readings according to the reading method in the next step.

[0092] 3) Select the first frame area by drawing a box around the image of the detection area on the leaf blade to be tested. When selecting the frame area, be careful to exclude the influence of non-detection areas.

[0093] Read the CT grayscale of the first selected area, open the grayscale histogram, and read the minimum grayscale value Gmin and the maximum grayscale value Gmax of the first selected area. Gmin represents the flux of the ray after attenuation when the ray passes through the maximum thickness, and Gmax represents the ray flux through the air. The ratio of the two is recorded as T, which is the ray transmittance of the detected part of the leaf blade.

[0094] T = Gmin / Gmax (1);

[0095] Take k readings at the i-th angle θi. Record the k minimum readings as Tθi-1min, Tθi-2min, Tθi-3min, ..., Tθi-kmin; record the k maximum readings as Tθi-1max, Tθi-2max, Tθi-3max, ..., Tθi-kmax. At this point, the transmittance corresponding to the i-th angle θi is:

[0096]

[0097] 4) Calculate sequentially to obtain the transmittance T at N illumination angles. θi (i = 1, 2, ..., N) and their corresponding transmission angles θi. Select the minimum transmittance, denoted as Tmin, and the corresponding angle at this position is denoted as θmin. Mark θmin as the minimum transmission angle.

[0098] 5. Perform a transmittance test as follows to obtain the final transmittance value.

[0099] 1) Using θmin as the new zero point of rotation angle, perform M fine measurements within the range of (-2°, +2°) of this zero point, with a second angle step (denoted as Δθ2). After each rotation angle, perform transmittance measurement according to the method in sections 3)-4) of step 4 above. Obtain the transmittance corresponding to the M rotation angles (i=1,2,…,M).

[0100] 2) Using the M transmittance values ​​obtained in the previous step as the ordinate and the rotation angle as the coordinate, plot the graph and fit the curve. Read the minimum transmittance value on the fitted curve and record it as T_minfinal = 1.773%. This value is recorded as the final measured minimum transmittance of the leaf.

[0101] The CT penetration characterization method for complex-structured blades provided in this embodiment has at least the following advantages:

[0102] First, a testing fixture 100 is prepared for blades with different configurations, and the testing reference is marked. Then, the CT system is calibrated. Next, the testing parameters are set according to the actual blade process, and transmittance tests are carried out to read transmittance data at different angles. Based on the transmittance data at different angles, a curve is fitted to obtain the minimum transmittance. Finally, the true transmittance characterization of CT detection of complex structure blades is achieved, overcoming the shortcomings of traditional CT detection of complex structure blades that lack effective transmittance measurement methods. This method can achieve true transmittance characterization of CT detection of complex structure blades and has broad application prospects and promotional value.

[0103] By using a detection device that can accurately measure transmittance, the true transmittance of the actual testing process for complex blades can be obtained.

[0104] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for characterizing the CT penetration rate of complex-structured blades, characterized in that, The method comprises the following steps: fixing the blade to be tested on a CT detection turntable to obtain an initial position; starting from the initial position, rotating the CT detection turntable to perform CT detection to obtain the transmittance of the blade to be tested at different rotation angles; fitting a curve according to the transmittance at different rotation angles, and reading the minimum transmittance on the fitted curve as the minimum transmittance of the blade.

2. The complex structure blade CT penetrability characterization method of claim 1, wherein, The step of starting from the initial position, rotating the CT detection turntable to perform CT detection to obtain the transmittance of the blade to be tested at different rotation angles comprises: starting from the initial position, rotating the CT detection turntable clockwise and counterclockwise multiple times at a first angle as a step, reading the maximum gray value and the minimum gray value of the first frame selection area of the blade to be tested at each rotation angle position, calculating the first transmittance corresponding to the rotation angle position through the maximum gray value and the minimum gray value read multiple times at the same rotation angle position, and taking the rotation angle position with the minimum first transmittance as the minimum transillumination angle; starting from the minimum transillumination angle, rotating the CT detection turntable clockwise and counterclockwise multiple times at a second angle as a step within a set angle range, reading the maximum gray value and the minimum gray value of the second frame selection area of the blade to be tested at each rotation angle position, and calculating the second transmittance corresponding to the rotation angle position through the maximum gray value and the minimum gray value read multiple times at the same rotation angle position. The step of fitting a curve according to the transmittance at different rotation angles, and reading the minimum transmittance on the fitted curve as the minimum transmittance of the blade comprises: fitting a curve through the second transmittance and the rotation angle corresponding to the second transmittance, and reading the minimum second transmittance on the fitted curve as the minimum transmittance of the blade.

3. The complex structure blade CT penetrability characterization method of claim 2, wherein, Before the step of fitting a curve through the second transmittance and the rotation angle corresponding to the second transmittance, and reading the minimum second transmittance on the fitted curve as the minimum transmittance of the blade, the step of starting from the minimum transillumination angle, rotating the CT detection turntable clockwise and counterclockwise multiple times at a second angle as a step within a set angle range, reading the maximum gray value and the minimum gray value of the second frame selection area of the blade to be tested at each rotation angle position, and calculating the second transmittance corresponding to the rotation angle position through the maximum gray value and the minimum gray value read multiple times at the same rotation angle position is executed at least once.

4. The method of complex structure blade CT permeability characterization according to any one of claims 1-3, characterized in that, The step of fixing the blade to be tested on the CT detection turntable to obtain an initial position comprises: fixing the blade to be tested on a three-jaw chuck of the CT detection turntable through a tooling; The preset condition is set for the blade to be tested, and the CT detection turntable is used to detect the rotation angle θ of the mechanical shaft R = 0° is a zero-degree position The rotary CT detects the rotary angle θ of the mechanical shaft of the rotary table when the blade to be measured is at the position where the transmissivity is the minimum R = θ - start is the initial position.

5. The complex structure blade CT penetrability characterization method of claim 4, wherein, The blade to be tested is a turbine blade. The setting of the blade to be tested under the preset condition, the CT detection turntable mechanical shaft rotation angle θ R = 0 ° is the zero position step includes: In the case of the perpendicular ray source end surface of the extension line of the exhaust edge plate side of the turbine blade, the CT detects the rotation angle θ of the mechanical shaft of the turntable R = 0° is the zero-degree position; The rotating CT detects the rotating angle θ of the mechanical shaft of the rotating table when the blade to be measured is at the position where the transmittance is the minimum R The step of setting the initial position includes, The rotating CT detects that the rotating table is closest to the X-ray source at the air inlet edge of the turbine blade, and the turbine blade is closest to the detector at the air outlet edge. At this time, the rotating angle θ of the mechanical shaft of the rotating CT detection rotating table is detected R = θ - start is the initial position.

6. The complex structure blade CT penetrability characterization method of claim 4, wherein, The blade to be tested is a turbine blade, the tooling is provided with a first clamping groove and a second clamping groove, the first clamping groove is arranged below the second clamping groove, the first clamping groove is used for wrapping a tenon of the turbine blade, the second clamping groove is used for clamping and fixing with a rim plate of the turbine blade, and the tooling is used for fixing the blade to be tested on the three-jaw chuck of the CT detection turntable, so that the blade to be tested and the CT detection platform maintain a set angle.

7. The complex structure blade CT penetrability characterization method of claim 6, wherein, The tooling includes a circular table and a clamping seat, the clamping seat is fixed on the circular table, the circular table is used for fixing on a CT detection rotary table three-jaw chuck, the clamping seat is provided with the first clamping groove and the second clamping groove, and the second clamping groove is a parallelogram.

8. The complex-geometry blade CT penetrability characterization method of any of claims 4, wherein, The step of fixing the blade to be detected on the CT detection rotary table to obtain an initial position further includes: After the step of fixing the blade to be detected on the CT detection rotary table three-jaw chuck through the tooling, the step includes setting detection parameters according to CT detection process parameters of the blade to be detected, adjusting distances between a ray source-sample and the sample-detecting device, performing bright-dark field correction on the CT detecting device, and performing mechanical shaft center correction.

9. The complex-structured blade CT penetrability characterization method of claim 2 or 3, wherein, The calculation formula of the first transmittance corresponding to the rotation angle position calculated by the maximum gray value and the minimum gray value read at the same rotation angle position multiple times includes: wherein, is the i-th angle θ i corresponding transmittance, T θi-1min , T θi-2min , T iθ -3min,..., T θi-kmin is the i-th angle θ i is the minimum gray level measured k times; T θi-1max , T θi-2max , T θi -3max,..., T θi-kmax is the i-th angle θ i is the maximum gray level measured k times.

10. The complex-structured blade CT penetrability characterization method of claim 2 or 3, wherein, The set angle range includes a minimum transillumination angle ± 2°.

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