Aircraft titanium-aluminum double-layer bolt hole defect identification and positioning method

Abstract

The present application relates to the technical field of aircraft bolt hole defect identification, in particular to a kind of aircraft titanium-aluminum double-layer bolt hole defect identification positioning method, comprising the following steps: statistical analysis titanium-aluminum double-layer bolt hole wall inside often occurring defect form and kind;According to the statistical titanium-aluminum double-layer bolt hole wall defect form and kind, design defect size and distribution state calibration and evaluation contrast test block, select the same part same material blank, according to the specification of bolt hole at butt strap plate process and assemble test piece;For identification object, clean titanium-aluminum double-layer bolt hole wall dirt;According to the specification of titanium-aluminum double-layer bolt hole, select corresponding scanning probe.The present application compares the size of double-layer bolt hole wall defect of aircraft butt strap plate and other parts by artificial injury of the same material, achieves the purpose of rapid determination of double-layer bolt hole internal defect, internal defect size evaluation, intuitive identification of defect position and defect distribution state identification.

Description

Technical Field

[0001] This invention relates to the field of aircraft bolt hole defect identification technology, specifically a method for identifying and locating defects in aircraft titanium-aluminum double-layer bolt holes. Background Technology

[0002] An aircraft's outer wing and center wing are horizontally connected by bolts, and vertically connected to the center wing by high-strength pins passing through a connecting strip plate. The bolts and high-strength pins pass through bolt holes, which are subjected to radial shear forces, frequently causing cracks and posing a significant threat to flight safety. The connecting strip plate has a variable thickness, consisting of a double-layered structure of aluminum and titanium plates with thicknesses of 3mm to 5mm. Therefore, the bolt holes in this area are also double-layered titanium-aluminum bolt holes, with two outer diameter specifications: φ10mm and φ12mm.

[0003] Currently, the main method for identifying bolt hole defects in aircraft repair is visual inspection. This involves using an explosion-proof lamp to illuminate the inside of the bolt hole, combined with a reflector to observe the reflection from various angles. For small-diameter bolt holes of φ10mm and φ12mm, visual inspection relies heavily on the operator's experience. However, prolonged and repetitive work with a large number of bolt holes can easily lead to visual fatigue, increasing the possibility of missed detections and misjudgments.

[0004] Current research on inspecting internal defects in bolt holes mainly includes: A 2019 master's thesis from Nanchang Aviation University disclosed a rotational scanning method for detecting circumferential cracks in planar multilayer metal riveting structures. This method shows that the rotational scanning method has a significant detection effect on circumferential defects in rivet holes. However, this method is only used for detecting surface defects around rivet holes and cannot identify defects in the internal wall of bolt holes.

[0005] Chinese patent CN 213337450U (authorization announcement date 2021.06.01) discloses a tooling for locating defects in the inner wall of a hole and for quantitative eddy current detection. This method overcomes the influence of edge effects and achieves the purpose of quantitatively locating defects by controlling the probe stepping through the assembly of the shell and scale. The disadvantage is that the defect location accuracy is poor due to the assembly, and the stepping is still subject to the influence of human factors due to the manual observation method. This method is an improvement and optimization of the manual method.

[0006] Chinese patent CN 111474238A (publication date: April 30, 2020) discloses a general method and device for eddy current detection of the inner wall of bolt holes. The method includes an eddy current detection method and a test block substrate with conical bolt holes. The disadvantage is that it can only detect circumferential and circumferential cracks in the inner wall under a single material condition, and cannot identify defects and locate the defect distribution in multi-layer bolt holes with multiple material superposition structures. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention proposes a method for identifying and locating defects in aircraft titanium-aluminum double-layer bolt holes. This method enables rapid determination of internal defects in double-layer bolt holes, assessment of defect size, intuitive identification of defect location, and marking of defect distribution.

[0008] The technical problem to be solved by this invention is achieved by the following technical solution: A method for identifying and locating defects in aircraft titanium-aluminum double-layer bolt holes includes the following steps: Step (1) Statistical analysis of the common defect forms and types occurring inside the walls of titanium-aluminum double-layer bolt holes; Step (II) Based on the statistical data on the types and forms of defects in the double-layer bolt holes of titanium and aluminum, design comparative test blocks for the determination and evaluation of defect size and distribution. Select raw materials of the same material in the same location and process and assemble test pieces according to the specifications of the bolt holes at the butt joint plate. Step (3) Clean the dirt and debris from the walls of the titanium-aluminum double-layer bolt holes for the identified object; Step (iv) Select the corresponding scanning probe according to the specifications of the titanium-aluminum double-layer bolt hole, and connect it to the data acquisition device based on the eddy current detection principle. The data acquisition device includes equipment, scanner, and planar and three-dimensional analysis software built into the equipment. Step (5) Before data acquisition, use the equipment and instruments to control the scanner, so that the scanning coil on the scanner is inserted into the artificial injury calibration test block of titanium-aluminum double-layer bolt hole for calibration to obtain data acquisition parameters. The data acquisition parameters include: equipment and instrument model, scanner model, probe model, excitation mode, rotation speed, gain, sampling rate, frequency mode 1, and frequency mode 2. Step (VI) Collect information data of the titanium-aluminum double-layer bolt holes of the mating strip plate according to the data acquisition parameters calibrated in Step (V), and process the acquired data through planar and three-dimensional analysis software to obtain planar and three-dimensional images; Step (7) Visually determine whether the image contains defects. If not, repeat steps (5) to (6). If yes, identify and locate the location of the defects based on the angle scale of the planar image. Step (8) In the frequency 1 mode of the data acquisition parameters in step (5), the location of the defect is identified according to the angle scale of the planar image. In the frequency 2 mode of the data acquisition parameters in step (5), the titanium alloy layer and aluminum alloy layer are identified according to the planar image. Combining the planar images in the frequency 1 mode and the frequency 2 mode, the material layer and location of the defect are identified. Step (nine) Fix the bolt holes of the aluminum-titanium double-layer structure with the aluminum alloy layer on top and the titanium alloy layer on the bottom. Adjust the equipment and instruments according to the data acquisition parameters obtained in step (five). The scanning coil on the scanner collects interface images in a non-contact state. After collecting the images, adjust the three-dimensional image perspective and rotate to observe and analyze the spatial location, size, distribution, and morphology of the defects.

[0009] Preferably, the process of designing and evaluating the comparative test blocks for defect size and distribution in step (ii) is as follows: Step (A) Select a titanium plate with a thickness of 3mm and an aluminum plate with a thickness of 5mm. The aluminum plate is designated as test block #1 and the titanium plate is designated as test block #2. Step (B) Drill 6 bolt holes in the superimposed state of titanium plate and aluminum plate, wherein holes 1 to 3 have an outer diameter of φ10mm, and holes 4 to 6 have an outer diameter of φ12mm. Step (C) On the aluminum plate test block, drill a through artificial crack at the 12 o'clock position for holes 1 and 4 respectively, and drill a through artificial crack at the 12 o'clock position for holes 2 and 5 respectively. Step (D) On the titanium plate test block #2, a through artificial crack is machined at the 6 o'clock position for holes #1 and #4 respectively, and a through artificial crack is machined at the 6 o'clock position for holes #2 and #5 respectively.

[0010] Preferably, in step (C), the artificial cracks on holes 1 and 4 of the aluminum plate test block 1 are 0.2±0.02mm deep and 13±0.01mm wide; the artificial cracks on holes 2 and 5 are 0.76±0.02mm deep and 0.13±0.01mm wide.

[0011] Preferably, in step (D), the artificial cracks on holes 1 and 4 of the titanium plate test block #2 are 0.2±0.02mm deep and 13±0.01mm wide; the artificial cracks on holes 2 and 5 are 0.76±0.02mm deep and 0.13±0.01mm wide.

[0012] Preferably, in step (iii), WUR-T cleaning agent and lint-free cotton fabric are used to clean the bolt hole walls.

[0013] Preferably, in step (iv), the scanning coil is inserted into the titanium-aluminum double-layer bolt hole and contacts the surface of the titanium-aluminum double-layer bolt hole wall, with a contact gap of less than 0.25 mm.

[0014] Preferably, in step (v), the timing scanning coil is kept horizontal with the central axis of the titanium-aluminum double-layer bolt hole, and the scanning coil passes through the titanium-aluminum double-layer bolt hole at a uniform speed.

[0015] Preferably, in step (v), the data acquisition parameters are as follows: the equipment model is MIZ-21C, the scanner model is ZM-5, the probe model is RSMφ9.8×60mm, the excitation mode is general transceiver, the rotation speed is 1800r / min, the gain is 30dB, and the sampling rate is 12500.

[0016] Preferably, the non-contact state acquisition process of the scanning coil on the scanner in step (nine) is as follows: When scanning hole 3 or hole 6 in aluminum plate test block #1 and titanium plate test block #2, the interface image collected and analyzed is uniform. When scanning hole 1 or hole 4 in aluminum plate test block #1 and titanium plate test block #2 in step (b), the planar image shows crack defects. The defect images on aluminum plate test block #1 and titanium plate test block #2 are diagonally distributed at 180°. The defect peaks in the three-dimensional image are raised. When scanning hole 2 or hole 4 in aluminum plate test block #1 and titanium plate test block #2 in step (c), the planar image shows obvious crack defects. The defect images on aluminum plate test block #1 and titanium plate test block #2 are diagonally distributed at 180°. The defect peaks in the three-dimensional image are towering.

[0017] The beneficial effects of this invention are: This invention compares the size of defects in the walls of double-layer bolt holes in parts such as aircraft docking strips using artificial damage to the same material. It identifies and locates the material layer where the defect is located and precisely positions the defect by using planar and three-dimensional image recognition. It has the advantages of intuitive display of defect distribution and simple defect identification operation. It achieves the purpose of rapid determination of internal defects in double-layer bolt holes, assessment of internal defect size, intuitive identification of defect location, and identification of defect distribution. Attached Figure Description

[0018] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 This is a flowchart of the present invention; Figure 2 This is a schematic diagram of the artificial damage calibration test block for titanium-aluminum double-layer bolt holes of the present invention; Figure 3 This is a schematic diagram of the data acquisition device of the present invention; Figure 4 This is a schematic diagram of the distribution of defects in the wall of the titanium-aluminum double-layer bolt hole according to the present invention. Detailed Implementation

[0019] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0020] like Figure 1As shown, a method for identifying and locating defects in aircraft titanium-aluminum double-layer bolt holes includes the following steps: Step (1) Statistical analysis of the common defect forms and types occurring inside the walls of titanium-aluminum double-layer bolt holes; Step (II) Based on the statistical data on the types and forms of defects in the double-layer bolt holes of titanium and aluminum, design comparative test blocks for the determination and evaluation of defect size and distribution. Select raw materials of the same material in the same location and process and assemble test pieces according to the specifications of the bolt holes at the butt joint plate.

[0021] Specifically, titanium plates (Ta15) and aluminum plates (7B04) were selected, with the titanium plate having a thickness of 3mm and the aluminum plate having a thickness of 5mm. For the titanium-aluminum double-layer bolt holes, two types of depth defects were designed in different orientations on both the aluminum and titanium alloys to verify the defect detection sensitivity and the ability to distinguish defect distribution locations under both material conditions.

[0022] The aluminum plate was designated as test block #1, and the titanium plate as test block #2. Six bolt holes were drilled in the stacked aluminum and titanium alloy configurations, with holes #1 to #3 having an outer diameter of φ10mm, and holes #4 to #6 having an outer diameter of φ12mm. After stacking and assembly, the bolt holes with the same numbering were aligned along their axes.

[0023] For the #1 aluminum alloy test block, a through-crack was machined at the 12 o'clock position of holes #1 and #4, with a depth of 0.2±0.02mm and a width of 0.13±0.01mm. A through-crack was also machined at the 12 o'clock position of holes #2 and #5, with a depth of 0.2±0.02mm and a width of 0.13±0.01mm.

[0024] For the No. 2 titanium alloy test block, a through-crack was machined at the 6 o'clock position on holes No. 1 and No. 4, with a depth of 0.2±0.02mm and a width of 0.13±0.01mm. Similarly, a through-crack was machined at the 6 o'clock position on holes No. 2 and No. 5, with a depth of 0.2±0.02mm and a width of 0.13±0.01mm. The defect design drawing for the test block is shown below. Figure 2 The main technical specifications of the comparative test blocks are shown in Table 1. Table 1. Technical Design Requirements for Artificial Injuries in Double-Layer Bolt Holes

[0025] Step (3) Clean the bolt hole walls of the identified object. Use WUR-T cleaner and lint-free cotton fabric to clean the walls of the titanium-aluminum double-layer bolt holes. There should be no dirt or debris on the inner wall of the hole that would hinder defect identification.

[0026] Step (IV) Select the corresponding scanning probe according to the specifications of the titanium-aluminum double-layer bolt holes. Connect the equipment and instruments based on the eddy current detection principle, such as... Figure 3As shown. The instrument is mainly used to control the scanner, for data acquisition, and for planar and three-dimensional image analysis. The scanning coil at the front of the scanning probe is inserted into the hole and contacts the hole wall surface, with a contact gap of less than 0.25 mm.

[0027] Step (5) Before data acquisition, use the instrument to control the scanner and insert the scanning coil into the artificial injury calibration block of the double-layer bolt hole for calibration. During calibration, keep the scanning coil horizontal with the center axis of the hole. Pass the scanning coil through the titanium-aluminum double-layer bolt hole at a uniform speed. The data acquisition parameters obtained from the calibration are shown in Table 2; Table 2 Data Acquisition Parameters for Double-Layer Bolt Holes

[0028] Step (VI) Following the data acquisition parameters and steps specified in Step (V), collect bolt hole information data for the titanium-aluminum double-layer structure of the mating strip plate. Process the collected data using planar and three-dimensional (3D) analysis software to obtain planar and three-dimensional images.

[0029] Step (7) Visually determine whether the image contains defects. If it does not contain defects, repeat steps (5) and (6). If the image contains defects, locate the location of the defects by using the angle scale of the planar image.

[0030] Step (8) In frequency 1 mode, identify the location of the defect based on the angle scale of the planar image; in frequency 2 mode, identify the titanium alloy layer and aluminum alloy layer based on the planar image; combine the planar images of frequency 1 and frequency 2 to identify the material layer and location of the defect.

[0031] Step (IX) Debug the MIZ-21C array eddy current detector according to the data acquisition parameters in Table 2. Install it with bolt holes for a double-layer aluminum-titanium structure, with the aluminum alloy layer on top and the titanium alloy layer below. Adjust filtering and other parameters, and check that the scanning coil is in a non-contact state to ensure uniform image acquisition at the interface, without any planar or three-dimensional images.

[0032] When scanning and comparing holes 3 or 6 of the artificial specimen, the acquired and analyzed interface image is uniform; when scanning and comparing holes 1 or 4 of the artificial specimen, the planar image shows crack defects, and the images of the aluminum alloy layer defects and titanium alloy layer defects are at a 180° diagonal position, which meets the design specifications for the specimen defects, and the defect peaks in the three-dimensional image are prominent; when the probe scans and comparing holes 2 or 5 of the artificial specimen, the planar image shows obvious crack defects, the images of the aluminum alloy layer defects and titanium alloy layer defects are at a 180° diagonal position, and the defect peaks in the three-dimensional image are high. Figure 4 As shown. After acquiring the images, the 3D image viewpoint is adjusted, and the spatial location, size, distribution, and morphology of defects are observed and analyzed. The reconstructed planar and 3D images, when superimposed on aluminum and titanium materials, exhibit high defect detection sensitivity and strong ability to resolve defect distribution areas.

[0033] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely prisms of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for identifying and locating defects in aircraft titanium-aluminum double-layer bolt holes, characterized in that: Includes the following steps: Step (1) Statistical analysis of the common defect forms and types occurring inside the walls of titanium-aluminum double-layer bolt holes; Step (II) Based on the statistical data on the types and forms of defects in the double-layer bolt holes of titanium and aluminum, design comparative test blocks for the determination and evaluation of defect size and distribution. Select raw materials of the same material in the same location and process and assemble test pieces according to the specifications of the bolt holes at the butt joint plate. Select aluminum plate as test block #1 and titanium plate as test block #2. With the titanium plate and aluminum plate stacked, drill 6 bolt holes. On aluminum plate test block #1, drill a through artificial crack at the 12 o'clock position for holes #1 and #4 respectively, and drill a through artificial crack at the 12 o'clock position for holes #2 and #5 respectively. On titanium plate test block #2, drill a through artificial crack at the 6 o'clock position for holes #1 and #4 respectively, and drill a through artificial crack at the 6 o'clock position for holes #2 and #5 respectively. Step (3) Clean the dirt and debris from the walls of the titanium-aluminum double-layer bolt holes for the identified object; Step (iv) Select the corresponding scanning probe according to the specifications of the titanium-aluminum double-layer bolt hole, and connect it to the data acquisition device based on the eddy current detection principle. The data acquisition device includes equipment, scanner, and planar and three-dimensional analysis software built into the equipment. Step (5) Before data acquisition, use the equipment and instruments to control the scanner, so that the scanning coil on the scanner is inserted into the artificial injury calibration test block of titanium-aluminum double-layer bolt hole for calibration to obtain data acquisition parameters. The data acquisition parameters include: equipment and instrument model, scanner model, probe model, excitation mode, rotation speed, gain, sampling rate, frequency mode 1, and frequency mode 2. Step (5) The timing scanning coil of the winning bidder shall be kept horizontal with the central axis of the titanium-aluminum double-layer bolt hole, and the scanning coil shall pass through the titanium-aluminum double-layer bolt hole at a uniform speed. Step (VI) Collect information data of the titanium-aluminum double-layer bolt holes of the mating strip plate according to the data acquisition parameters calibrated in Step (V), and process the acquired data through planar and three-dimensional analysis software to obtain planar and three-dimensional images; Step (7) Visually determine whether the image contains defects. If not, repeat steps (5) to (6). If yes, identify and locate the location of the defects based on the angle scale of the planar image. Step (8) In the frequency 1 mode of the data acquisition parameters in step (5), the location of the defect is identified according to the angle scale of the planar image. In the frequency 2 mode of the data acquisition parameters in step (5), the titanium alloy layer and aluminum alloy layer are identified according to the planar image. Combining the planar images in the frequency 1 mode and the frequency 2 mode, the material layer and location of the defect are identified. Step (nine) Fix the bolt holes of the aluminum-titanium double-layer structure with the aluminum alloy layer on top and the titanium alloy layer on the bottom. Adjust the equipment and instruments according to the data acquisition parameters obtained in step (five). The scanning coil on the scanner collects interface images in a non-contact state. After collecting the images, adjust the three-dimensional image perspective and rotate to observe and analyze the spatial location, size, distribution, and morphology of the defects.

2. The method for identifying and locating defects in aircraft titanium-aluminum double-layer bolt holes according to claim 1, characterized in that: The process of designing and evaluating the size and distribution of defects using comparative test blocks in step (II) is as follows: Step (A) Select a titanium plate with a thickness of 3mm and an aluminum plate with a thickness of 5mm. The aluminum plate is designated as test block #1 and the titanium plate is designated as test block #2. In step (B), holes 1 to 3 on aluminum plate test block #1 and titanium plate test block #2 have an outer diameter of φ10mm, and holes 4 to 6 have an outer diameter of φ12mm.

3. The method for identifying and locating defects in aircraft titanium-aluminum double-layer bolt holes according to claim 2, characterized in that: In step (C), the artificial cracks on holes 1 and 4 of the aluminum plate test block #1 are 0.2±0.02mm deep and 0.13±0.01mm wide; the artificial cracks on holes 2 and 5 are 0.76±0.02mm deep and 0.13±0.01mm wide.

4. The method for identifying and locating defects in aircraft titanium-aluminum double-layer bolt holes according to claim 2, characterized in that: In step (D), the artificial cracks on holes 1 and 4 of the titanium plate test block #2 are 0.2±0.02mm deep and 0.13±0.01mm wide; the artificial cracks on holes 2 and 5 are 0.76±0.02mm deep and 0.13±0.01mm wide.

5. The method for identifying and locating defects in aircraft titanium-aluminum double-layer bolt holes according to claim 1, characterized in that: In step (3), use WUR-T cleaning agent and lint-free cotton fabric to clean the bolt hole walls.

6. The method for identifying and locating defects in aircraft titanium-aluminum double-layer bolt holes according to claim 1, characterized in that: In step (iv), the scanning coil is inserted into the titanium-aluminum double-layer bolt hole and contacts the surface of the bolt hole wall with a contact gap of less than 0.25mm.

7. The method for identifying and locating defects in aircraft titanium-aluminum double-layer bolt holes according to claim 1, characterized in that: In step (5), the data acquisition parameters are as follows: the equipment model is MIZ-21C, the scanner model is ZM-5, the probe model is RSMφ9.8×60mm, the excitation mode is general transceiver, the rotation speed is 1800r / min, the gain is 30dB, and the sampling rate is 12500.

8. The method for identifying and locating defects in aircraft titanium-aluminum double-layer bolt holes according to claim 2, characterized in that: The non-contact state acquisition process of the scanning coil on the scanner in step (nine) is as follows: When scanning hole 3 or hole 6 in aluminum plate test block #1 and titanium plate test block #2, the interface image collected and analyzed is uniform. When scanning hole 1 or hole 4 in aluminum plate test block #1 and titanium plate test block #2 in step (b), the planar image shows crack defects. The defect images on aluminum plate test block #1 and titanium plate test block #2 are diagonally distributed at 180°. The defect peaks in the three-dimensional image are raised. When scanning hole 2 or hole 4 in aluminum plate test block #1 and titanium plate test block #2 in step (c), the planar image shows obvious crack defects. The defect images on aluminum plate test block #1 and titanium plate test block #2 are diagonally distributed at 180°. The defect peaks in the three-dimensional image are towering.

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