Knocking detection method and device for aircraft blade defects

Abstract

The invention provides a knock detection method and device for aircraft blade defects, and the method comprises the steps: carrying out the knock detection of a to-be-detected blade through knock points in an array form, so as to obtain a knock value matrix; interpolating the knocking numerical value matrix to obtain an interpolated knocking numerical value matrix; obtaining the deviation between each element in the interpolated knock value matrix and the reference knock value of the reference block; obtaining a two-dimensional matrix according to the deviation of each element in the interpolated knock value matrix and a preset deviation; when the deviation of the elements is greater than the preset deviation, the value of the element in the two-dimensional matrix is 1, otherwise, the value of the element in the two-dimensional matrix is 0; and according to the two-dimensional matrix, obtaining the defect position of the blade to be detected. And providing a defect boundary evaluation basis for guiding helicopter blade knocking detection work.

Description

Technical Field

[0001] The present invention belongs to the technical field of aviation detection, and particularly relates to a percussion detection method and device for defects of aircraft propeller blades. Background Art

[0002] During the model test and mass production process of helicopter propeller blades, in order to ensure whether the product quality meets the technical requirements, non-destructive testing work is an indispensable process. Due to its advantages such as portability and easy operation, percussion detection has become an essential detection technology in the non-destructive testing of propeller blades. Percussion detection is carried out by using light hard objects such as coins and small hammers, or a percussion detection device to strike the surface of the material. Based on the analysis of acoustic feedback and vibration signals, the internal damage or quality of the object is detected through the sound, touch or vibration generated by the percussion. Therefore, whether the percussion detection method is correct will directly affect the discrimination of the defect nature and the determination of the defect size and location.

[0003] In non-destructive testing, reference blocks are mainly used to determine the detection parameters and compare defect information. Therefore, the manufacturing quality of the reference blocks will directly affect the detection of defects and the qualitative and quantitative determination of defects.

[0004] Currently, the conventional percussion detection is manual percussion detection, and the defect determination depends relatively on the subjectivity of people, and the accuracy and precision are relatively poor.

[0005] It is relatively difficult to make the propeller blade reference block, especially in simulating the nature of the defect and the difference of the percussion signal.

[0006] The existing percussion detection methods mainly have the following defects:

[0007] 1) The method for making the reference block is single. The conventional method for making the reference block is to pre-place a release cloth or film, and it cannot ensure that the fabricated prefabricated defects meet the established goals, and there is a lack of relevant evaluation methods;

[0008] 2) The accuracy of the reference block lacks verification. After data collection of the fabricated reference block, there is a lack of collection and correction of data on actual defects. Therefore, there will be a deviation in guiding daily percussion detection;

[0009] 3) The determination of the defect boundary is not accurate enough. During the actual detection process, the detected defects often lack verification. Summary of the Invention

[0010] The present invention provides a percussion detection method and device for defects of aircraft propeller blades, and solves the problems existing in the existing percussion detection methods.

[0011] In a first aspect of the present invention, a percussion detection method for defects of aircraft propeller blades is provided, including:

[0012] For the blade to be measured, it is struck and detected at the striking points in the form of an array to obtain a striking value matrix.

[0013] Interpolate the striking value matrix to obtain the interpolated striking value matrix.

[0014] Obtain the deviation between each element in the interpolated striking value matrix and the reference striking value of the reference test block.

[0015] According to the deviation of each element in the interpolated striking value matrix and the preset deviation, obtain a two-dimensional matrix; when the deviation of the element is greater than the preset deviation, the value of the element in the two-dimensional matrix is 1, otherwise it is 0.

[0016] According to the two-dimensional matrix, obtain the defect position of the blade to be measured.

[0017] Optionally, the method further includes:

[0018] Perform a CT scan on the defective blade to obtain the actual defect area S T and the number of ply layers at the defect.

[0019] Strike and detect the defective blade at the striking points in the form of an array to obtain a striking value matrix; interpolate the striking value matrix to obtain the interpolated striking value matrix.

[0020] Obtain the deviation between the value of each element in the interpolated striking value matrix and the reference striking value of the same ply layer number of the reference test block.

[0021] According to the deviation and the initial preset deviation, obtain an initial two-dimensional matrix; when the deviation of the element is greater than the initial preset deviation, the value of the element in the initial two-dimensional matrix is 1, otherwise it is 0; obtain the estimated defect area S according to the elements with a value of 1 in the initial two-dimensional matrix 估计 , judge the estimated defect area S 估计 and the actual defect area S T Whether the deviation is within 5%, if not, increase the initial preset deviation, and obtain the initial two-dimensional matrix and the estimated defect area S again 估计 , until the deviation between the estimated defect area S 估计 and the actual defect area S T is within 5%; take the initial preset deviation at this time as the final preset deviation.

[0022] Optionally, the method further includes:

[0023] Perform a CT inspection on the reference test block to determine the intact area and the number of ply layers in the intact area.

[0024] Collect the knocking detection data for the intact areas of the reference test block according to different ply numbers, sum and average the knocking detection values for different ply numbers to obtain the reference knocking values for different ply numbers.

[0025] Optionally, the method further includes:

[0026] Perform CT detection on the reference test block to determine the prefabricated defect area of the reference test block, the preset ply number of the preset defect area, the intact area, and the ply number of the intact area;

[0027] Collect the knocking detection data for the intact areas of the reference test block according to different ply numbers, sum and average the knocking detection values for different ply numbers to obtain the reference values for different ply numbers;

[0028] Equidistantly divide the prefabricated defect area to obtain m·n knocking points, perform knocking detection, and obtain the knocking detection values;

[0029] Compare the knocking detection value of each knocking point with the reference value corresponding to the preset ply number at the knocking point to obtain the number n of abnormal data points where the difference is greater than the preset range 异 ;

[0030] Judge the number n of abnormal data points 异 Whether the ratio to the total number m·n of knocking points is less than 80%;

[0031] If so, determine that the area of the prefabricated defect of the reference test block is unqualified and prepare a new reference test block;

[0032] If not, obtain the variance of the m·n knocking detection values. If the variance is greater than 1, determine that the knocking detection values within the prefabricated defect of the reference test block are discrete; prepare a new reference test block.

[0033] Optionally, the number of collected points is greater than 100.

[0034] Optionally, the method further includes:

[0035] Select the rigid sandwich foam of the same material used for actual blade production and shape the foam according to the Z200-Z600 area of the actual blade;

[0036] Perform array hole digging on the upper and lower surfaces of the shaped foam, with the hole depth being 1 mm, the hole spacing being 60 mm, and the hole diameter specifications including at least Φ4 mm, Φ8 mm, Φ12 mm, Φ16 mm, Φ20 mm;

[0037] Cover the outer surface of the foam after hole digging with a thermoplastic / hot melt material for film isolation;

[0038] Place the prepreg of the actual blade on the foam after film covering and perform corresponding layering. The prepreg completely wraps the foam and is molded to obtain a comparison test block.

[0039] Optionally, the method further includes:

[0040] Select a rigid sandwich foam of the same material used for manufacturing the actual blade, and modify the shape of the foam according to the Z200 - Z600 area of the actual blade;

[0041] Perform corresponding layering on the upper and lower surfaces of the shaped foam, cut in the middle layer of the prepreg to obtain array holes, and use a thermoplastic / thermally fusible material to isolate the array holes between the middle layer and the top layer prepreg; the hole spacing is 60 mm, and the diameter specifications of the holes at least include Φ2 mm, Φ6 mm, Φ10 mm, Φ14 mm, Φ18 mm; the prepreg completely wraps the foam;

[0042] Mold the layered foam and prepreg to obtain a comparison test block.

[0043] The second aspect of the present invention provides a percussion detection device for aircraft blade defects, which is used to execute the method described in any one of the first aspects.

[0044] The present invention provides a percussion detection method and device for aircraft blade defects, designs a set of comparison test blocks for blade percussion detection, and proposes a method for evaluating the rationality of prefabricated defect preparation. Taking the percussion detection data of the comparison test block as a benchmark, perform percussion detection on the defect test pieces naturally formed during the test process, collect the percussion detection values, use relevant algorithms to classify and identify the data, compare with the actual size of the defect, and finally obtain the defect boundary evaluation basis for guiding the percussion detection work of helicopter blades. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 is the imaging of the original percussion detection data;

[0046] Figure 2 is the imaging of the data after interpolation with k = 1;

[0047] Figure 3 is the imaging of the data after normalization with k = 1 and α = 0.2;

[0048] Figure 4 3D view of the blade segment comparison test block;

[0049] Figure 5 is the layout diagram of the prefabricated defects of the blade segment comparison test block;

[0050] Figure 6 is the specific flow chart of the defect boundary evaluation method. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0051] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0052] The features and illustrative embodiments of various aspects of the present invention will be described in detail below. In the following detailed description, many specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without some of these specific details. The following description of the embodiments is only intended to provide a better understanding of the present invention by showing examples of the present invention. The present invention is in no way limited to any specific arrangements and methods set forth below, but covers any improvements, substitutions, and modifications of structures, methods, and devices without departing from the spirit of the present invention. Well-known structures and technologies are not shown in the drawings and the following description to avoid unnecessarily obscuring the present invention.

[0053] It should be noted that, without conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other, and the various embodiments may refer to and cite each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0054] The present invention will be further described in detail below in combination with the embodiments and the accompanying drawings, but the implementation manners of the present invention are not limited thereto.

[0055] As Figures 1-6 shown, the present invention provides a percussion detection method and device for defects of aircraft propeller blades, which are divided into three parts. The first part is the manufacturing method of the percussion detection comparison test block, the second part is the comparison of the manufacturing effects of the percussion detection comparison test block, and the third part is the use of the comparison test block in the actual percussion detection process and the determination method of the defect boundary.

[0056] Part 1: Manufacturing method of the percussion detection comparison test block

[0057] Defect prefabrication is mainly carried out by manual material removal. The general method is to design information such as the size specifications of the propeller blade sample section comparison test block, prepare relevant materials, prefabricate two types of prefabricated defects respectively. The method of digging holes in the propeller blade sandwich core is used to simulate the debonding defect between the skin and the foam, and the method of digging holes in the middle layer of the skin is used to simulate the delamination defect between the skins. The prefabricated defects are circular defects with specifications of Φ2mm to Φ18mm.

[0058] The relevant steps are as follows:

[0059] NO.1.A1: Preparation of comparison test blocks for debonding defect blade sections:

[0060] NO.1.A1001: 1) Debonding defect prefabrication

[0061] Use the same hard sandwich foam material as that used for blade production, and modify the shape according to the actual blade Z200~Z600 area; Figure 5 As shown, dig holes with a depth of 1mm, specifications of Φ4mm, Φ8mm, Φ12mm, Φ16mm, Φ20mm, and a hole spacing of 60mm;

[0062] NO.1.A1002:2) Thermoplastic / hot melt edge sealing

[0063] To avoid damage or filling of the foam holes during the subsequent molding process, the excavated foam holes of different specifications are sealed with thermoplastic / hot-melt materials. The sealing includes the upper and lower skin surfaces of the holes, the foam surface, and the surrounding area of the foam.

[0064] NO.1.A1003:3) Composite skin layup

[0065] Composite prepreg is cut and blanked according to the blade production process guide, and is placed on the foam core for corresponding layering, with a certain margin reserved for the outermost skin to directly cover both sides of the foam section to form a whole;

[0066] NO.1.A1004:4) Comparative test block molding

[0067] The blade sample comparison test block is formed using the same molding process as the actual blade. The molding method is autoclave molding, which generally involves bagging, vacuuming, and heating molding.

[0068] NO.1.A2: Preparation of comparison test blocks for blade sections with delamination defects:

[0069] NO.1.A2001:1) Sandwich foam molding

[0070] Select the same hard sandwich foam material as that used for blade production, and shape it according to the actual blade Z200~Z600 area;

[0071] NO.1.A2002:2) Composite skin layer

[0072] According to the blade production process guide, the composite material prepreg is cut and blanked, and the prepreg is placed on the foam core for corresponding layering. Figure 1As shown, perform cutting. The hole depth is 1 layer of skin thickness, and the specifications are Φ2mm, Φ6mm, Φ10mm, Φ14mm, Φ18mm. A certain margin is reserved for the outermost skin to directly cover both sides of the foam section to form a whole;

[0073] NO.1.A2003: The same as NO.1.A1004.

[0074] Second part: Evaluation of the production effect of prefabricated defects in the comparison test block

[0075] To evaluate the production effect of the comparison test block of the blade sample section, it is necessary to conduct percussion detection and inspection on the prefabricated defects. By processing and analyzing the data sampled from the detection, indirectly evaluate the production quality of the prefabricated defects, and rework the prefabricated defects that do not meet the requirements.

[0076] NO.2.B001: Conduct CT detection on the comparison test block of the blade sample section, use CT imaging technology to accurately locate the prefabricated defects, and measure the area of the defects as S m ;

[0077] NO.2.B002: Collect percussion detection data for the intact area of the comparison test block of the blade sample section. Collect data in segments according to different ply thicknesses. The number of collected points should be at least greater than 100. For the data points collected at different plies, collect N1 points in the area with ply number 1, N2 points in the area with ply number 2,..., and Nn points in the area with ply number n. Sum up and average the percussion detection values according to the plies, and define them as T N1 , T N2 , ……, T Nn , This value is defined as the reference value for different ply numbers;

[0078] NO.2.B003: Divide the prefabricated defect area in the comparison test block of the blade sample section that has been made into equal distances, and plan to divide it into m rows and n columns (m ≥ 2, n ≥ 2);

[0079] Exemplarily, percussion is performed using... equipment.

[0080] NO.2.B004: Conduct percussion detection on the prefabricated defect area in the form of an array. Represent the percussion detection value of the i-th row and the j-th column in the form of (x i , y j , T (i,j) ) as T (i,j) , where i ≤ m and j ≤ n;

[0081] NO.2.B005: Compare the percussion detection value T (i,j) with the reference value collected at the corresponding ply number in NO.2.B002, collect and record the number of abnormal data points, and record it as n异 ;

[0082] NO.2.B006: Compare the number of abnormal data points n 异 , with the total number of points m·n, and S 检 =(n 异 / m·n)·S m ;

[0083] NO.2.B007: If S 检 / S m is less than 80%, it is determined that the area of the prefabricated defect is unqualified;

[0084] NO.2.B008: Calculate the sample variance of the percussion detection values at the defect, if the variance is greater than 1, the percussion detection values within the prefabricated defect are relatively discrete, and it is determined that the adhesion within the prefabricated defect is relatively large;

[0085] NO.2.B009: The prefabricated defects determined to be non - compliant through the above NO.2.B007 and NO.2.B008 should be remade.

[0086] Part Three: Defect Boundary Evaluation Method

[0087] During the percussion detection process, the most crucial thing is to find out how to distinguish the boundary of the defect once the defect is identified. The actual defect boundary is not like that of the prefabricated defect, which directly transitions from intact to the defect area with a direct jump in percussion values. The percussion detection values of the actual defect will have a corresponding transition zone. Therefore, during the actual percussion detection process, the number of points collected is often limited, which is not conducive to the determination of the defect boundary. By using the method of multiple interpolations, the percussion data can be enlarged, and normalized iterative processing can be carried out with the reference value, which can accurately determine the defect boundary and thus accurately image the defect.

[0088] NO.3.C001: Select a blade that has shown delamination / debonding defects after the test. Through CT scanning, obtain the actual size of the defect here, defined as S T ;

[0089] NO.3.C002: Conduct percussion detection on the blade that has shown delamination / debonding defects in the form of an array. Represent the percussion detection value of the i - th row and j - th column in the form of (x i ,y j ,T (i,j) ) as T (i,j) , where i ≤ m and j ≤ n;

[0090] NO.3.C003: Collect and summarize the percussion detection values into the following data matrix:

[0091]

[0092]

[0093] NO.3.C004: Interpolate between the data in the NO.3.C003 data matrix pairwise. The inserted value is the mean between the two values, and the number of interpolations is k (k≥1); the data matrix after interpolation is roughly listed as follows:

[0094]

[0095] NO.3.C005: Compare the interpolated percussion data matrix in NO.3.C004 with the reference values T N1 , T N2 , ……, T Nn of the blade segments of the same layer.

[0096] NO.3.C006: The specific comparison method is that the deviation α between the value in the data matrix and the reference value

[0097] NO.3.C007: The deviation α is assigned a value starting from 0.01, and the assignment interval is 0.01;

[0098] NO.3.C008: When the deviation in the data matrix is greater than the assigned value, the data matrix value is set to 1, and when it is less, the matrix value is set to 0.

[0099] Therefore, a new data matrix is produced, roughly listed as follows:

[0100]

[0101] NO.3.C009: Count the number of 1s in the NO.3.C005. For example, the row count is g and the column count is h, then the defect size is (g / m)·length, (h / m)·width;

[0102] NO.3.C010: Perform imaging processing on the normalized data matrix in NO.3.C005 to generate a percussion detection data map of the entire blade, and the defect size can be measured in the map; calculate the percussion detection area S α ;

[0103] NO.3.C011: Compare the percussion area S α with S T . The deviation value β = ((S α - S T ) / S T )·100%, and the deviation value β is obtained;

[0104] NO.3.C012: Repeated iteration, steps NO.3.C006 to NO.3.C011, finally it is obtained that β should be within 5%, and the reference value deviation α is obtained;

[0105] NO.3.C013: Subsequently, during the daily inspection of the blade, numerical evaluation is carried out with the reference value deviation α to define the defect boundary.

[0106] The technical effects of the present invention are as follows:

[0107] NO.3.C001: Conduct CT inspection on the blade with delamination / debonding defects that have already occurred, and finally determine that the defect area is S T ;

[0108] NO.3.C002: Mesh division is carried out on the blade with delamination / debonding defects that have already occurred, and finally it is determined that the number of rows is 16 and the number of columns is 61;

[0109] NO.3.C003: Conduct percussion inspection on the blade and collect relevant data. The specific data table is shown in Table 1;

[0110] Table 1 Percussion inspection values

[0111]

[0112]

[0113] NO.3.C004: Interpolation processing is carried out on the data table 1, and the insertion of k = 1 is listed, and the others are similar in turn;

[0114]

[0115]

[0116]

[0117] NO.3.C005, NO.3.C006, NO.3.C007, NO.3.C008 only list the numerical values with the reference value deviation α of 0.2, that is, the deviation of 20%. After normalization, the data table

[0118]

[0119]

[0120]

[0121]

[0122] Iterate NO.3.C009, NO.3.C010, NO.3.C011, NO.3.C012, and NO.3.C013, change the values of the k value and the reference value deviation α, and finally determine the optimal parameters to guide subsequent blade knocking detection.

[0123] As described above, this is only a further embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the scope disclosed by the present invention, according to the technical solution and concept of the present invention, makes equivalent substitutions or changes, and all belong to the protection scope of the present invention.

Claims

1. A percussion detection method for defects of an aircraft blade, characterized in that Including: For the blade to be measured, use tapping points in an array form to perform tapping detection on the blade to be measured to obtain a tapping value matrix; Interpolate the tapping value matrix to obtain an interpolated tapping value matrix; Obtain the deviation between each element in the interpolated tapping value matrix and the reference tapping value of the reference test block; According to the deviation of each element in the interpolated tapping value matrix and the preset deviation, obtain a two-dimensional matrix; when the deviation of the element is greater than the preset deviation, the value of the element in the two-dimensional matrix is 1, otherwise it is 0; According to the two-dimensional matrix, obtain the defect position of the blade to be measured.

2. The knocking detection method for the defect of the aircraft blade according to claim 1, characterized in that The method further includes: Perform a CT scan on the defective blade to obtain the actual defect area S T and the number of ply layers at the defect Use tapping points in an array form to perform tapping detection on the blade with defects to obtain a tapping value matrix; interpolate the tapping value matrix to obtain an interpolated tapping value matrix; Obtain the deviation between the value of each element in the interpolated tapping value matrix and the reference tapping value of the same ply number of the reference test block; Obtain an initial two-dimensional matrix according to the deviation and the initial preset deviation; when the deviation of an element is greater than the initial preset deviation, the value of the element in the initial two-dimensional matrix is 1, otherwise it is 0; obtain the estimated defect area S according to the elements with a value of 1 in the initial two-dimensional matrix 估计 , and judge the estimated defect area S 估计 and the actual defect area S T whether the deviation is within 5%, if not, increase the initial preset deviation, and obtain the initial two-dimensional matrix and the estimated defect area S again 估计 , until the deviation between the estimated defect area S 估计 and the actual defect area S T is within 5%; take the initial preset deviation at this time as the final preset deviation.

3. The percussion detection method for defects of an aircraft blade according to claim 1, wherein The method further includes: Perform CT detection on the reference test block to determine the intact area and the ply number of the intact area; Collect tapping detection data for the intact area of the reference test block according to different ply numbers, sum and average the tapping detection values of different ply numbers to obtain the reference tapping values of different ply numbers.

4. The knocking detection method for defects of an aircraft blade according to claim 3, characterized in that The method further includes: Perform CT detection on the reference test block to determine the prefabricated defect area of the reference test block and the preset ply number of the preset defect area, the intact area and the ply number of the intact area; Collect tapping detection data for the intact area of the reference test block according to different ply numbers, sum and average the tapping detection values of different ply numbers to obtain the reference values of different ply numbers; Equidistantly divide the prefabricated defect area to obtain m·n tapping points, perform tapping detection to obtain tapping detection values; Compare the tapping detection value of each tapping point with the reference value corresponding to the preset number of ply layers at the tapping point to obtain the number n of abnormal data points where the difference is greater than the preset range 异 ; Determine the number of abnormal data points n 异 Whether the ratio to the total number of tapping points m·n is less than 80%; If so, it is determined that the prefabricated defect area of the reference test block is unqualified, and a new reference test block is prepared; If not, obtain the variance of the m·n tapping detection values. If the variance is greater than 1, it is determined that the tapping detection values in the prefabricated defect of the reference test block are discrete; prepare a new reference test block.

5. The percussion detection method for defects of an aircraft blade according to claim 4, wherein The number of collected points is greater than 100.

6. The percussion detection method for defects of an aircraft blade according to claim 4, characterized in that, The method further includes: Select a rigid sandwich foam of the same material used for manufacturing the actual blade, and shape the foam according to the Z200-Z600 area of the actual blade; Perform array hole digging on the upper and lower surfaces of the shaped foam, the hole depth is 1 mm, the hole spacing is 60 mm, and the hole diameter specifications at least include Φ4 mm, Φ8 mm, Φ12 mm, Φ16 mm, Φ20 mm; Use a thermoplastic / heat-melting material to perform film covering and isolation on the outer surface of the foam after hole digging; Place the prepreg of the actual blade on the film-covered foam for corresponding layup, and the prepreg completely wraps the foam and is formed to obtain a reference test block.

7. The knocking detection method for defects of the aircraft blade according to claim 4, wherein The method further includes: Select a rigid sandwich foam of the same material used for manufacturing the actual blade, and shape the foam according to the Z200-Z600 area of the actual blade; Corresponding layering is carried out on the upper and lower mold surfaces of the repaired foam, cutting is performed on the prepreg intermediate layer to obtain array holes, and between the middle layer and the top layer prepreg, a thermoplastic / heat-meltable material is used to cover and isolate the array holes; the hole spacing is 60 mm, and the hole diameter specifications at least include Φ2 mm, Φ6 mm, Φ10 mm, Φ14 mm, Φ18 mm; the prepreg completely wraps the foam; The layered foam and prepreg are formed to obtain a comparison test block.

8. A percussion detection device for defects of an aircraft blade, characterized in that, For performing the method according to any one of claims 1-7.

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