Defect detection method for metal code disc without coating

Abstract

The present application provides a defect detection method for a metal code disk that does not require coating, which relates to the field of information technology, including: fusing the external geometric model of the metal code disk obtained by three-dimensional scanning with the internal defect information of the metal code disk obtained by X-ray flaw detection to construct a three-dimensional model of the metal code disk containing internal defects; if there is stress concentration around the defect, the internal defects of the metal code disk are analyzed for stability using fracture mechanics theory, the stress intensity factor at the tip of the defect is calculated, the risk of crack propagation under the action of external force is evaluated, and the critical size and safety margin of the defect are determined; the defect distribution law of the metal code disk is obtained according to the internal defect information of the metal code disk, and the structural layout and key dimensional parameters of the metal code disk are optimized in combination with the defect distribution law of the metal code disk and the safety assessment criteria. Reduce the failure risk of the code disk due to internal defects and improve the reliability and safety of the use of the code disk.

Description

Technical Field

[0001] The present invention relates to the field of information technology, and in particular to a defect detection method for a metal code disk that does not require coating. Background Art

[0002] Metal code discs may have internal defects during the manufacturing and use process, especially for metal code discs that do not require coating. These internal defects include pores, inclusions, cracks, shrinkage cavities and looseness, etc. The spatial distribution and morphological characteristics of these defects directly affect the stress state and safety of use of the code disc. At present, the detection of internal defects of code discs mainly relies on manual observation and simple two-dimensional imaging, which cannot fully and accurately reflect the three-dimensional spatial characteristics of defects. At the same time, due to the complexity and irregularity of the defect morphology, the existing theoretical models are difficult to accurately predict the stress concentration and crack propagation behavior caused by defects, which greatly restricts the optimization of the code disc structure design and the reliability of safety assessment. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides a defect detection method for a metal code disk without coating, which mainly includes:

[0004] The metal code disk is scanned in all directions by using 3D scanning technology to obtain the 3D point cloud data of the metal code disk, and the external geometric model of the metal code disk is reconstructed through the 3D point cloud data of the metal code disk, wherein the external geometric model of the metal code disk includes the geometric shape and size information of the metal code disk; the internal structure of the metal code disk is detected by using X-ray flaw detection technology to obtain the tomographic image data of the inside of the metal code disk, and the tomographic image is segmented and feature extracted by the image processing algorithm to identify the defect area in the image to obtain the internal defect information of the metal code disk, wherein the internal defect information of the metal code disk includes the spatial position, shape and size information of the metal code disk defect; the external geometric model of the metal code disk obtained by 3D scanning is integrated with the internal defect information of the metal code disk obtained by X-ray flaw detection to construct a 3D model of the metal code disk containing internal defects; the 3D model of the metal code disk is meshed and the boundary conditions are set according to the material properties and structural parameters of the metal code disk, and the code disk is simulated in the actual The stress conditions under the actual working state are analyzed, the influence of internal defects on the stress distribution of the code disc is analyzed, and it is determined whether there is stress concentration around the defect; if there is stress concentration around the defect, the stability analysis of the internal defects of the metal code disc is carried out using the fracture mechanics theory, the stress intensity factor at the tip of the defect is calculated, the risk of crack propagation of the defect under the action of external force is evaluated, and the critical size and safety margin of the defect are determined; according to the critical size and safety margin of the defect and the actual working conditions and failure mode of the metal code disc, a safety assessment criterion is formulated, which includes regular inspection and tracking evaluation of the defect status of the code disc, timely discovery of the defect expansion trend, prediction of the remaining service life of the code disc, and providing a decision-making basis for the maintenance and replacement of the code disc; the defect distribution law of the metal code disc is obtained according to the internal defect information of the metal code disc, and the structural layout and key dimensional parameters of the metal code disc are optimized in combination with the defect distribution law of the metal code disc and the safety assessment criterion.

[0005] The technical solution provided by the embodiment of the present invention may have the following beneficial effects:

[0006] The present invention discloses a defect detection method for a metal code disc that does not require coating. In view of the problem that the metal code disc may have internal defects during use, which may lead to safety hazards, the external geometric model and internal defect information of the code disc are obtained through three-dimensional scanning and X-ray flaw detection technology, and the two are integrated to construct a complete three-dimensional model. Based on the model, finite element analysis and fracture mechanics calculations are performed to evaluate the stress concentration phenomenon and crack propagation risk around the defect, and determine the critical size and safety margin of the defect. According to the evaluation results, safety assessment criteria are formulated to realize dynamic monitoring of the defect state of the code disc and life prediction, and guide the structural optimization design of the code disc. The present invention realizes the precise detection, safety assessment and preventive maintenance of the internal defects of the metal code disc, effectively reduces the failure risk of the code disc due to internal defects, and improves the reliability and safety of the use of the code disc. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 The figure is a flow chart of the defect detection method of the metal code disk without coating of the present invention. DETAILED DESCRIPTION

[0008] In order to enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this specification will be clearly and completely described below in conjunction with the drawings in the embodiments of this specification. Obviously, the described embodiments are only part of the embodiments of this specification, not all of the embodiments. Based on the embodiments in this specification, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of this specification.

[0009] like Figure 1 The defect detection method of the metal code disk without coating in this embodiment may specifically include:

[0010] S101. Use three-dimensional scanning technology to perform an all-round scan on the metal code disk to obtain three-dimensional point cloud data of the metal code disk, and reconstruct an external geometric model of the metal code disk through the three-dimensional point cloud data of the metal code disk, wherein the external geometric model of the metal code disk includes geometric shape and size information of the metal code disk.

[0011] A laser line scanning device is used to scan the surface of the metal code disk in the horizontal and vertical directions, and the laser power output is adjusted according to the reflection intensity value of the metal code disk to obtain an original point cloud data file; Gaussian filter parameters are set for the original point cloud data file, and the point cloud noise is determined by local curvature calculation, and the noise points are removed according to the curvature threshold to obtain a filtered point cloud data file; three-dimensional coordinate points are read from the filtered point cloud data file, an initial triangular mesh is constructed according to the mesh edge length parameters, and the initial triangular mesh is divided into four equal parts to obtain an optimized mesh unit; a Poisson surface reconstruction algorithm is used for the optimized mesh unit, and the metal code disk contour curve data is obtained by calculating the mesh vertex coordinates; Bezier curve control points are set according to the metal code disk contour curve data, and the contour curve is fitted by the least squares method, and the curve segment size parameters are calculated according to the fitting error threshold to obtain the metal code disk three-dimensional geometric data file.

[0012] Specifically, a high-definition laser line scanning device is used to alternately scan the surface of the metal code disk at an angle interval of 0.5 degrees in the horizontal and vertical directions. The laser power output is adjusted in the range of 0.2 to 0.8 according to the reflection intensity value of the metal code disk, and the point cloud sampling interval is set to 0.1 mm to generate the original point cloud data file. For the noise points in the original point cloud data file, a Gaussian filter with a size of 5x5 pixels and a standard deviation parameter of 1.5 is set to perform noise reduction operations on the data. The point cloud noise is judged by local curvature calculation, and the curvature threshold is set to 0.05. Points with curvature values ​​greater than the threshold are removed to generate a filtered point cloud data file. The three-dimensional coordinate points are read from the filtered point cloud data file, and the initial triangular mesh is constructed according to the mesh side length parameters of 0.2 to 0.5 mm. The mesh units with a side length greater than 0.5 mm are divided into four equal parts, and the mesh is optimized using Poisson surface reconstruction. The mesh vertex coordinates are calculated to generate the metal code disk contour curve data. According to the contour curve data, 20 Bezier curve control points are set, and the contour curve is fitted using the least squares method. The fitting error threshold is set to 0.05 mm, and the actual size parameters of all curve segments are calculated to generate the three-dimensional geometric data file of the metal code disk. A high-definition laser line scanning device is used to scan the metal code disk from directly above. The vertical and horizontal scanning angles in the scanning parameters are both from 0 degrees to 360 degrees, and the angle interval is set to 0.5 degrees. During the scanning process, the laser output power is adjusted in real time within the range of 50-200 watts. When the reflection intensity value of the metal code disk surface is detected to be in the range of 0.2 to 0.8, the scanning data is recorded. The sampling spacing of the scanning device in the XYZ three-axis direction is set to 0.1 mm, and the original point cloud data obtained by scanning is stored as a PCD format file. After reading the point cloud data from the original PCD format file, a Gaussian filter matrix of 5x5 pixels is constructed, with the standard deviation set to 1.5. The three-dimensional Gaussian distribution is calculated for the spatial position of each scanning point, and the local curvature value in the neighborhood around each point is calculated. When the curvature value is greater than 0.05, the point is determined to be a noise point and deleted, and the obtained data is saved again as a filtered point cloud data file. Based on the filtered point cloud data, a triangular mesh is constructed according to the initial mesh side length of 0.2 mm. The mesh unit uses a quadrilateral mesh. For the units with a mesh side length of more than 0.5 mm, the mesh is subdivided by four equal divisions. The subdivided mesh is used as the input for Poisson surface reconstruction. The Poisson reconstruction parameter configuration with an octree depth of 8 is used to optimize the mesh surface, and the mesh vertices are extracted to generate contour curve data. For the acquired contour curve, 20 Bezier curve control points are arranged at the key feature points of the curve. The spacing between the control points is in the range of 0.5 to 1 mm. The least squares method is used to fit the contour curve. The fitting error threshold is set to 0.05 mm. The fitting result is used to generate the external contour curve equation of the metal code disk and calculate the actual size of all curve segments.

[0013] S102. Use X-ray flaw detection technology to detect the internal structure of the metal code disk, obtain tomographic image data of the inside of the metal code disk, segment and extract features of the tomographic image through an image processing algorithm, identify the defective area in the image, and obtain the internal defect information of the metal code disk, wherein the internal defect information of the metal code disk includes the spatial position, shape and size information of the metal code disk defect.

[0014] A planar array detector X-ray scanning device is used to obtain scanning data of the metal code disk, and a grayscale tomography image is generated according to the scanning data, wherein the grayscale value range of the grayscale tomography image is within a first preset interval; a median filter matrix is ​​constructed for the grayscale tomography image, and a noise reduction process is performed on the grayscale tomography image according to the median filter matrix to obtain a filtered image, and the filtered image is converted into a grayscale data format, wherein the grayscale value range of the grayscale data format is within a second preset interval; image data is read from the grayscale filtered image, and a defect area is extracted according to the image data by using a region growing segmentation operation, and if the grayscale difference of adjacent pixels is less than a preset threshold, the defect area is marked by 8-neighborhood connectivity; a Sobel operator is used to process the marked area to obtain a defect boundary point set, and the defect boundary point set contains the spatial coordinate information of the defect contour; according to the spatial coordinate information of the defect boundary point set, a principal axis direction determination method is used to calculate a minimum bounding rectangle, and defect feature parameters are obtained by using the length parameter and width parameter of the minimum bounding rectangle, and the defect feature parameters include defect position coordinates, defect size and shape feature values.

[0015] Specifically, the metal code disk is scanned by using an array detector X-ray scanning device, the X-ray tube voltage is set to 90 kV, the current is set to 50 mA, the pixel size of the array detector is set to 0.1 mm, the field of view is set to 100x100 mm, the sampling interval is set to 0.2 mm, and the metal code disk is scanned 360 degrees to generate a 16-bit grayscale format tomographic image with a grayscale value range of 0 to 65535. A median filter matrix of 5x5 pixels is constructed for the 16-bit grayscale tomographic image, and the median is selected by sorting the grayscale values ​​in the neighborhood of each pixel point, and the standard deviation parameter of the Gaussian smoothing operation is set to 1.2. The image is subjected to denoising, and the resulting filtered image is converted into an 8-bit grayscale data format with a grayscale value range of 0 to 255. Image data is read from the 8-bit grayscale filtered image, and the defect area is extracted by regional growth segmentation operation. The regional growth threshold range is set between grayscale values ​​20 and 40, and the growth criterion is set to set the grayscale difference of adjacent pixels to be less than 5. The segmented area is marked by 8-neighborhood connectivity, and the edge contour of the marked area is extracted by the Sobel operator to obtain the defect boundary point set. According to the spatial coordinates of the defect boundary point set, the minimum circumscribed rectangle is calculated by the main axis direction determination method, and the defect size parameters are obtained by the length and width of the rectangle. The three shape feature values ​​of the circularity, rectangularity, and eccentricity of the defect area are calculated to generate a detection data file containing the defect position coordinates, size, and shape feature values. When scanning the metal code disk using an array detector X-ray scanning device, a projection image is collected every 1 degree on the rotating platform. The X-ray tube voltage is set to 90 kV and the current is 50 mA. The field of view of the array detector covers an area of ​​100x100 mm. The pixel size of a single detector is 0.1 mm, and the interval between adjacent sampling points is 0.2 mm. The collected 360 projection image data are stored in 16-bit grayscale format, with an image resolution of 1000x1000 pixels and a single pixel grayscale value range of 0-65535. A 5x5 median filter window is constructed for the acquired tomographic image to reduce noise. The window slides pixel by pixel on the image. Each time, the grayscale values ​​of 25 pixels in the window are sorted from small to large. The 13th value after sorting is selected as the new grayscale value of the center pixel. Then, Gaussian smoothing operation is used, with a standard deviation parameter of 1.2 and a smoothing kernel size of 5x5 pixels. The image is subjected to a second denoising. The denoised image data is converted to an 8-bit grayscale format, and the grayscale value range is compressed to 0-255. Select pixels with grayscale values ​​less than 40 as seed points on the 8-bit grayscale image, and expand in 8 directions around the seed point. If the grayscale difference between the adjacent pixel and the center point is less than 5, the point is merged into the current area and continues to expand as a new seed point until all qualified pixels are marked to obtain a complete defect area. The Sobel operator is used to extract the edge contour points of the marked area.The principal axis direction is calculated for the extracted edge contour points. The principal axis direction is defined as the direction that minimizes the sum of the squares of the distances from the contour points to the straight line. The local coordinate system is established with the principal axis direction, and the minimum circumscribed rectangle of the contour points is calculated to obtain the length and width of the defect. At the same time, the circularity parameters of the contour points are calculated. The circularity value is between 0 and 1. The closer the value is to 1, the closer the shape is to a circle. The rectangularity parameter is calculated. The rectangularity value is also between 0 and 1. The closer the value is to 1, the closer the shape is to a rectangle. The eccentricity parameter is calculated to characterize the symmetry of the defect shape.

[0016] S103, the external geometric model of the metal code disk obtained by three-dimensional scanning is integrated with the internal defect information of the metal code disk obtained by X-ray flaw detection to construct a three-dimensional model of the metal code disk including internal defects.

[0017] The coordinate system of the three-dimensional external geometric model of the metal code disk is aligned with the coordinate system of the X-ray tomography image to establish a spatial mapping relationship between the three-dimensional model and the tomography image; according to the spatial position relationship between the three-dimensional external model and the internal defect information in the unified coordinate system, the defect information is mapped to the corresponding position of the three-dimensional external model to achieve the fusion of the defect information and the three-dimensional model; the fused three-dimensional model is meshed and the surface is reconstructed to optimize the size and distribution of the triangular facets; according to the three-dimensional size parameters of the defect information, a three-dimensional entity that matches the size and shape of the defect area is constructed in the three-dimensional model, and the three-dimensional entity is embedded in the corresponding position of the three-dimensional model to obtain a three-dimensional solid model of the metal code disk containing internal defects; the three-dimensional solid model is rendered, the model surface is texture mapped according to the material properties of the metal code disk, and the lighting and material parameters are set to generate a realistic three-dimensional model of the metal code disk.

[0018] Specifically, when aligning the three-dimensional external geometric model of the metal code disk with the X-ray tomography image, the iterative closest point algorithm is used for point cloud alignment, and the maximum number of iterations is set to 100 times, and the convergence error threshold is 0.5 mm. After alignment, the three-dimensional spatial coordinates of the defect information are mapped to the coordinate system of the three-dimensional external model through the affine transformation matrix, and the defect position is accurately corresponded to the three-dimensional model. The fused three-dimensional model is meshed, and the mesh size is adaptively adjusted according to the curvature change. The mesh size of the flat area is set to 1 mm, and the mesh size of the area with large curvature is reduced to 5 mm. For the defect area, the defect size parameters are used to construct a three-dimensional entity with the same shape and size in the three-dimensional model, and the coordinates of the entity vertices are calculated according to the defect position. The NURBS surface is used to fit the surface of the defect entity to obtain a three-dimensional entity model that fits the defect shape. The three-dimensional solid model is realistically rendered, and the surface is textured according to the material parameters of the metal code disk. The ambient light intensity is set to 3, the diffuse reflection coefficient is 6, the highlight coefficient is 7, and the highlight index is 30. The rendering generates a realistic three-dimensional model with metallic luster and surface texture. The number of model vertices is about 500,000, and the number of triangles is about 1 million.

[0019] S104. According to the material properties and structural parameters of the metal code disk, mesh the three-dimensional model of the metal code disk and set boundary conditions to simulate the stress conditions of the code disk under actual working conditions, analyze the impact of internal defects on the stress distribution of the code disk, and determine whether there is stress concentration around the defects.

[0020] The metal code disc model is meshed using twenty-node hexahedral units, and the basic mesh side length obtained through the meshing is the mesh size of the code disc model; the basic mesh is encrypted layer by layer in the defect area, and the mesh quality of the defect area is greater than the preset Jacobian matrix threshold. The code disc boundary conditions are set according to the meshing results, and the node freedom constraints of the code disc model are obtained by applying fixed constraints on the code disc bearing mounting surface; the axial sine load and radial cosine load are applied to the code disc according to the node freedom constraints of the code disc model to obtain the code disc load distribution. The transient response calculation of the code disc load distribution is performed by an explicit integral solver, and the mass damping coefficient and stiffness damping coefficient are set according to the transient response calculation to obtain the calculation step length result of the code disc model. Iterative calculation is performed according to the calculation step length result of the code disc model, and the steady-state response result of the code disc model is obtained by judging the node displacement and stress convergence error. The stress value of the defect edge is extracted based on the steady-state response result of the code disk model. If the stress value of the defect edge simultaneously satisfies the conditions that the stress value is greater than the preset stress threshold, the stress gradient is greater than the preset gradient threshold, and the principal stress ratio is greater than the preset ratio threshold, the grid node number of the stress concentration area is marked to obtain the position coordinates of the maximum stress value in the stress concentration area.

[0021] Specifically, the code disc model is meshed using twenty-node hexahedral units, and the material properties are set to 200 GPa elastic modulus, 0.3 Poisson's ratio, and 250 MPa yield strength. The basic mesh side length is set to 0.5 mm, and the mesh is encrypted layer by layer to 0.1 mm at a ratio of 1:2 within 1 mm outside the defect area. The mesh quality is determined by the Jacobian matrix value being greater than 0.85, and the mesh distortion rate is less than 0.2. Fixed boundary conditions are applied within a radius of 20 mm on the code disc bearing mounting surface, constraining the node displacement in three directions and three angular degrees of freedom, setting the bearing contact area friction coefficient to 0.15, and applying a sinusoidal axial load with an amplitude of 50 Newton and a frequency of 50 Hz on the code disc working surface. The radial load of 500 Newton is distributed on the nodes through a cosine function, and the speed is set to 3000 revolutions per minute. The explicit integral solver is used for transient response calculation, the mass damping coefficient is set to 0.05, the stiffness damping coefficient is set to 0.03, the time step is 0.1 milliseconds, the calculation results are output every 100 steps, and the steady-state response is achieved after 2000 steps. The node displacement convergence error is less than 0.001 mm, and the stress convergence error is less than 0.1 MPa. The node stress values ​​within 1 mm of the defect edge are extracted from the steady-state calculation results, and the principal stress values ​​and Mises stress are calculated. It is judged that the stress concentration area should simultaneously meet the three conditions of stress value greater than 200 MPa, stress gradient greater than 50 MPa per millimeter, and principal stress ratio greater than 2.5. The grid node number of the stress concentration area is marked, and the coordinates of the maximum stress value position are recorded. When the 3D model of the metal code disk with a diameter of 100 mm is meshed using 20-node hexahedral units, three layers of transitional grids are set within a range of 1 mm, based on the basic grid size of 0.5 mm and based on the defect center, with the grid sizes of 0.1 mm, 0.2 mm, and 0.4 mm, respectively, forming a 1:2 progressive size relationship, and a total of 85,426 grid units are generated. The distortion rate of all units calculated by the Jacobian matrix is ​​less than 0.2, and the grid quality is greater than 0.85. The physical parameters of the metal code disk material are set on the grid model, with a central bearing contact radius of 20 mm, an operating temperature of 20 degrees Celsius, an elastic modulus of 200 GPa, a Poisson's ratio of 0.3, a yield strength of 250 MPa, and a density of 7.85 grams per cubic centimeter. The friction contact is defined on the bearing contact surface, with a friction coefficient of 0.15, and the six degrees of freedom of the contact area are constrained. When applying the load, the 50 Newton axial force is applied to the working surface through the sine function f=50sin(2π×50t), and the 500 Newton radial force is distributed at the circumferential nodes according to the cosine function cos(θ). The centrifugal force corresponding to the rotation speed of 3000 revolutions per minute is calculated by the center of mass acceleration. The explicit integral solver is selected to set the mass damping to 0.05, the stiffness damping to 0.03, the time step to 0.1 milliseconds, and the results are output every 100 steps. The calculation reaches a steady state after 2000 steps, and the displacement convergence error is less than 0.001 mm.The node stress within 1 mm of the defect edge is extracted from the calculation results, and the three principal stresses σ1, σ2, σ3 and Mises stress σv are calculated. When the stress value at the node is greater than 200 MPa and the stress gradient exceeds 50 MPa per millimeter, and the principal stress ratio σ1 / σ3 is greater than 2.5, it is determined that stress concentration occurs at this location, and the maximum stress value of 286 MPa is recorded at 0.2 mm at the defect tip.

[0022] S105. If stress concentration exists around the defect, the fracture mechanics theory is used to conduct stability analysis on the internal defects of the metal code disk, calculate the stress intensity factor at the tip of the defect, evaluate the risk of crack propagation under the action of external force, and determine the critical size and safety margin of the defect.

[0023] Degenerate quadrilateral singular units are used to mesh the defect tip area, the midpoint node position coordinates of the degenerate quadrilateral singular unit are offset toward the tip by one quarter of the side length, transition units are arranged around the degenerate quadrilateral singular unit, and the unit size increases gradually from the inside to the outside according to a set ratio; a three-dimensional displacement field is calculated according to the meshing result, displacement sampling points are arranged along the circumferential direction in the three-dimensional displacement field, and a stress intensity factor is obtained by least square fitting of the radial displacement of the displacement sampling points; a crack propagation driving force is calculated according to the stress intensity factor, and the crack propagation direction is obtained by using the maximum circumferential stress criterion through the crack propagation driving force; for the crack propagation direction, the energy release rate is calculated by J-integral on the circumferential path, and the J-integral uses a set integral path radius; a parameterized analysis is performed on the defect size, and a safety margin is obtained by the ratio of the mixed mode stress intensity factor to the critical value. If the safety margin is greater than the set value, it is determined to be a stable state.

[0024] Specifically, an 8-node degenerate quadrilateral singular unit is used to reconstruct the mesh of the defect tip area. The unit size is set to 0.05 mm, the coordinates of the midpoint node position of the singular unit are offset to the tip by one-quarter of the side length, and 4 layers of transition units are arranged around the unit. The unit size increases gradually from 0.1 mm to 0.4 mm from the inside to the outside, and the local encrypted mesh is obtained by 1 / r stress singularity processing. The three-dimensional displacement field is calculated according to the stress field distribution of the defect tip. Displacement sampling points are arranged every 45 degrees along the circumferential direction within the range of 0.1 to 0.3 mm from the tip, with a sampling interval of 0.05 mm. The radial displacement least squares fitting is used to calculate the stress intensity factors under three loading modes, and the calculation results are verified by singular stress field reconstruction. The crack propagation driving force is calculated by the stress intensity factor, the material fracture toughness value is set to the square root of 80 MPa·m, the maximum circumferential stress criterion is used to calculate the crack propagation direction, the propagation direction angle interval is 5 degrees, the energy release rate on the circumferential path is calculated by J integral, and the integral path radius is 0.2 mm. The defect size is parametrically analyzed, starting from the initial value of 0.5 mm, and iterative calculations are performed by increasing 0.2 mm each time. The critical size is recorded when the mixed mode stress intensity factor exceeds the critical value. The safety margin is calculated by the ratio of the actual stress intensity factor to the critical value. A safety margin greater than 1.5 is considered to be a stable state. When fracture mechanics is used to analyze metal code disk defects, an 8-node quadrilateral singular unit is constructed around the defect tip, with a unit size of 0.05 mm. The middle node is moved 0.0125 mm toward the tip to express the stress singularity. Four circles of transition units are arranged around the unit, with sizes of 0.1, 0.2, 0.3, and 0.4 mm, respectively, and the corresponding number of nodes is 32, 40, 48, and 56, respectively. When dealing with 1 / r stress singularity, the singularity is transformed to the integral point through node coordinate transformation. Starting from the position of 0.1 mm from the tip of the singular unit, 8 displacement sampling points are arranged every 45 degrees along the circumference, and a circle is arranged every 0.05 mm outward until a total of 40 sampling points are arranged at 0.3 mm. The radial displacement least squares fitting is used to calculate the stress intensity factors KI, KII, and KIII, and the fitting accuracy error is less than 1%. The three stress intensity factors are calculated to be the square roots of 26, 18, and 12 MPa·m, respectively, and the mixed mode equivalent stress intensity factor is the square root of 32 MPa·m. The J integral value calculated on the circular path with a radius of 0.2 mm around the defect tip is 0.0048 joules per square millimeter. Through parametric analysis, it is found that when the defect size increases from 0.5 mm to 2.3 mm, the equivalent stress intensity factor increases to the square root of 75 MPa·m, which is close to the square root of the material fracture toughness value of 80 MPa·m. At this time, the critical size is determined to be 2.3 mm, and the calculated safety margin is 1.67, which is greater than the safety threshold of 1.5. It is determined that the current defect is in a stable state.

[0025] S106. Safety assessment criteria are formulated based on the critical size and safety margin of defects as well as the actual working conditions and failure modes of the metal code disc. The safety assessment criteria include regular inspection and follow-up assessment of the defect status of the code disc, timely discovery of defect expansion trends, prediction of the remaining service life of the code disc, and providing a decision-making basis for maintenance and replacement of the code disc.

[0026] A Paris crack growth rate curve is constructed according to the fracture toughness value and stress intensity factor of the metal code disk, and the crack growth rate coefficient and crack growth index are obtained through cyclic loading; an internal defect image of the metal code disk is obtained by an X-ray flaw detector, and the internal defect image is processed by Gaussian filtering to obtain a filtered image, and the defect contour features are extracted from the filtered image using the Canny edge detection operator; an exponential function is fitted for the defect contour features, and the functional relationship between the crack growth rate and the stress intensity factor is calculated according to the fitting result, and a defect tip stress intensity factor database is established; the stress state of the defect tip is queried according to the defect tip stress intensity factor database, the critical size of the defect is determined based on the fracture toughness criterion, and the real-time defect size is obtained from the defect contour features; the Monte Carlo method is used to calculate the life distribution probability of the real-time defect size, and a maintenance instruction is triggered if the real-time defect size is greater than a preset threshold or the crack growth rate exceeds a preset rate threshold.

[0027] Specifically, the Paris crack growth rate curve is constructed based on the square root of the fracture toughness of the metal code disk of 80 MPa·m and the square root of the measured stress intensity factor of 32 MPa·m. Cyclic loading is carried out under the conditions of stress ratio 0.1 and frequency 10 Hz to obtain the crack growth rate coefficient of 2.1x10^-12 and crack growth index of 3.2. The corresponding relationship between the crack growth amount and the number of cycles is calculated by numerical integration. An X-ray flaw detector is used to regularly monitor the internal defects of the metal code disk. The monitoring frequency is set to record once every 8 hours, and the scanning resolution is 0.1 mm. Gaussian filtering is used to remove image noise, and the defect contour is extracted by the Canny edge detection operator. The center of gravity position of the defect area and the maximum diameter change are calculated. The exponential function ax^b is used to fit the detection data, the coefficient a is 2.5x10^-5, the exponent b is 1.8, the functional relationship between the crack growth rate and the stress intensity factor is calculated, the safety factor is set to 1.5, the critical size of 2.3 mm is calculated based on the fracture toughness criterion, and a database of stress intensity factors at the defect tip is established. The remaining life is predicted by Monte Carlo simulation, with 10,000 random samplings, and the life distribution probability is obtained at a 95% confidence level. The lower limit of the safe life is calculated in combination with the fatigue damage accumulation criterion, and the maintenance instruction is triggered when the defect size is greater than 1.8 mm or the expansion rate exceeds 0.01 mm per hour. In the safety assessment of metal code disks, the Paris curve is constructed based on the measured stress intensity factor of 32 MPa·m square root. Through cyclic loading with a frequency of 10 Hz and a stress ratio of 0.1, the change in defect length is recorded in real time. When the stress intensity factor changes from 25 to 40 MPa·m square root, the expansion rate coefficient is measured to be 2.1x10^-12 and the expansion exponent is 3.2. The integral calculation shows that the defect expansion amount is 0.5 mm after 1000 hours of operation. An X-ray flaw detector with a resolution of 0.1 mm was used for monitoring. The voltage was set to 90 kV and the current was set to 50 mA during image acquisition. A 5x5 pixel Gaussian filter was used to eliminate random noise. The standard deviation was 1.2. The high and low threshold ratio of Canny edge detection was set to 2:1. The coordinates of the defect boundary points were extracted by sub-pixel interpolation, and the defect area growth rate was calculated to be 0.02 square millimeters per hour. An expansion rate database was established for 720 hours of continuous monitoring data. The exponential fitting function coefficient was 2.5x10^-5 and the exponent was 1.8. The fitting accuracy error was less than 3%, and the time required for the defect size to reach the critical value of 2.3 mm was predicted to be 1500 hours. In the Monte Carlo life prediction, the fatigue load amplitude, frequency, and material parameters were randomly sampled with a sample size of 10,000 times, and the average life was 1200 hours, the standard deviation was 180 hours, and the lower limit of the 95% confidence interval was 900 hours. When the defect size exceeded 1.8 mm or the expansion rate was greater than 0.01 mm per hour, the remaining life prediction value was 200 hours lower than the safety threshold.

[0028] S107. Obtain the defect distribution law of the metal code disk according to the internal defect information of the metal code disk, and optimize the structural layout and key dimensional parameters of the metal code disk in combination with the defect distribution law of the metal code disk and the safety assessment criteria.

[0029] Receive metal code disk defect data, analyze the metal code disk defect data through DBSCAN density clustering algorithm, and obtain coordinate information of high-risk areas; establish a parameterized geometric structure model according to the coordinate information of the high-risk areas, and optimize the geometric structure model by BESO topology optimization method to obtain an initial topological structure; set hub thickness, rim inclination and rib number parameters for the initial topological structure, and obtain stress distribution data through tetrahedral meshing calculation; design an L16 orthogonal test scheme according to the stress distribution data, and obtain Mises stress value and stress gradient value under each parameter combination through orthogonal test; use NSGA-II algorithm to perform multi-objective optimization calculation for the Mises stress value and stress gradient value, and obtain the optimal structural parameters that meet the stress limit and quality targets.

[0030] Specifically, the density clustering algorithm DBSCAN is used to extract the distribution law of the internal defect data of the metal code disk, and the clustering radius is set to 1.5 mm, the neighborhood density threshold is 3 defect points, the number and size distribution of defects in each unit volume of each area are calculated, and a three-dimensional hot spot distribution map is generated. The coordinates of high-risk positions are marked in areas where the defect density is greater than 5 per cubic centimeter. A parametric geometric structure is established according to the high-risk area, and the bidirectional progressive structure optimization BESO is used to generate the topological structure. The unit size is set to 0.2 mm, the evolution rate is 0.02, the filter radius is 2 mm, and the transition fillet is set at the stress concentration position. The fillet radius changes adaptively with the stress gradient, and the maximum fillet radius is limited to 5 mm. The L16 (4^4) orthogonal test is used to arrange the parameter combination, the hub thickness is set to 20, 23, 26, and 29 mm, the rim inclination is set to 15, 18, 21, and 24 degrees, and the number of ribs is set to 8, 9, 10, and 11. The stress distribution is calculated by tetrahedral meshing, the unit size is 0.5 mm, and the maximum Mises stress and stress gradient are recorded. The NSGA-II multi-objective optimization algorithm is used to optimize the structural parameters. The objective function includes stress level and quality. The constraints include stress limit of 200 MPa, stress gradient limit of 50 MPa per millimeter, displacement limit of 0.1 mm, initial population size of 100, crossover probability of 0.8, mutation probability of 0.1, iteration of 200 times, and the optimal solution is selected through the Pareto front. In the optimization design of metal code disks, when the density clustering algorithm DBSCAN is used to process defect distribution data, the clustering radius is set to 1.5 mm and the neighborhood density threshold is 3 points. The 156 detected defect points are clustered to form 12 defect clusters. The defect density at the hub connection is calculated to be 8 per cubic centimeter, and the defect density in the stress concentration area is 6 per cubic centimeter. The hot spot distribution map is generated through three-dimensional grid statistics. The BESO algorithm was used to optimize the structure of high-risk areas, starting from the initial solid unit volume fraction of 0.9, removing 2% of the material each time, filtering the radius of 2 mm to eliminate the checkerboard phenomenon, setting the transition fillet at the position where the stress is greater than 150 MPa, and the fillet radius changes linearly with the stress gradient. The stress gradient of 40 MPa per millimeter corresponds to a 5 mm fillet. According to the L16 orthogonal table, 16 groups of tests were arranged, and the stress distribution was calculated by tetrahedral meshing. The unit mass matrix used a concentrated mass matrix, and the stiffness matrix used a linear tetrahedron unit. The boundary conditions set the bearing seat to be fixed, and applied a speed of 3000 rpm and a radial load of 500 Newtons. It was found that the optimal stress distribution was obtained by combining a hub thickness of 26 mm, a rim inclination of 21 degrees, and 10 ribs. This combination was input into the NSGA-II algorithm as the initial solution with a population size of 100. During 200 iterations, the crossover probability was 0.8 and the mutation probability was 0.1, and the Pareto optimal solution set was obtained, from which the optimization scheme with a stress level of 185 MPa, a mass reduction of 15%, and a stress gradient of 45 MPa per millimeter was selected.

[0031] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A defect detection method for a metal code disc without coating, characterized in that: The method comprises: The metal code disk is scanned in all directions by using 3D scanning technology to obtain the 3D point cloud data of the metal code disk, and the external geometric model of the metal code disk is reconstructed through the 3D point cloud data of the metal code disk, wherein the external geometric model of the metal code disk includes the geometric shape and size information of the metal code disk; the internal structure of the metal code disk is detected by using X-ray flaw detection technology to obtain the tomographic image data of the inside of the metal code disk, and the tomographic image is segmented and feature extracted by the image processing algorithm to identify the defect area in the image to obtain the internal defect information of the metal code disk, wherein the internal defect information of the metal code disk includes the spatial position, shape and size information of the metal code disk defect; the external geometric model of the metal code disk obtained by 3D scanning is integrated with the internal defect information of the metal code disk obtained by X-ray flaw detection to construct a 3D model of the metal code disk containing internal defects; the 3D model of the metal code disk is meshed and the boundary conditions are set according to the material properties and structural parameters of the metal code disk, and the code disk is simulated in the actual The stress conditions under the actual working state are analyzed, the influence of internal defects on the stress distribution of the code disc is analyzed, and it is determined whether there is stress concentration around the defect; if there is stress concentration around the defect, the stability analysis of the internal defects of the metal code disc is carried out using the fracture mechanics theory, the stress intensity factor at the tip of the defect is calculated, the risk of crack propagation of the defect under the action of external force is evaluated, and the critical size and safety margin of the defect are determined; according to the critical size and safety margin of the defect and the actual working conditions and failure mode of the metal code disc, a safety assessment criterion is formulated, which includes regular inspection and tracking evaluation of the defect status of the code disc, timely discovery of the defect expansion trend, prediction of the remaining service life of the code disc, and providing a decision-making basis for the maintenance and replacement of the code disc; the defect distribution law of the metal code disc is obtained according to the internal defect information of the metal code disc, and the structural layout and key dimensional parameters of the metal code disc are optimized in combination with the defect distribution law of the metal code disc and the safety assessment criterion.

2. The method according to claim 1, characterized in that The three-dimensional scanning technology is used to perform an all-round scanning on the metal code disk to obtain the three-dimensional point cloud data of the metal code disk, including: Use a laser line scanning device to scan the surface of the metal code disk in the horizontal and vertical directions, and adjust the laser power output according to the reflection intensity value of the metal code disk to obtain the original point cloud data file; Gaussian filter parameters are set for the original point cloud data file, point cloud noise is determined by local curvature calculation, and noise points are removed according to a curvature threshold to obtain a filtered point cloud data file.

3. The method according to claim 2, characterized in that The external geometric model of the metal code disk is reconstructed through the three-dimensional point cloud data of the metal code disk, and the external geometric model of the metal code disk includes the geometric shape and size information of the metal code disk, including: Reading three-dimensional coordinate points from the filtered point cloud data file, constructing an initial triangular mesh according to a mesh side length parameter, and dividing the initial triangular mesh into four equal parts to obtain optimized mesh units; A Poisson surface reconstruction algorithm is used for the optimized grid unit to obtain the metal code disk contour curve data by calculating the grid vertex coordinates; Bezier curve control points are set according to the metal code disk contour curve data, the contour curve is fitted by the least square method, and the curve segment size parameters are calculated according to the fitting error threshold to obtain the metal code disk three-dimensional geometric data file.

4. The method according to claim 1, characterized in that The X-ray flaw detection technology is used to detect the internal structure of the metal code disk, to obtain the tomographic image data inside the metal code disk, to segment and extract features of the tomographic image through an image processing algorithm, to identify the defect area in the image, and to obtain the internal defect information of the metal code disk, the internal defect information of the metal code disk includes the spatial position, shape and size information of the metal code disk defect, including: Using an area array detector X-ray scanning device to acquire scanning data of the metal code disk, generating a grayscale tomography image according to the scanning data, wherein the grayscale value range of the grayscale tomography image is within a first preset interval; Constructing a median filter matrix for the grayscale tomography image, performing noise reduction processing on the grayscale tomography image according to the median filter matrix to obtain a filtered image, converting the filtered image into a grayscale data format, wherein the grayscale value range of the grayscale data format is within a second preset interval; Reading image data from the grayscale filtered image, extracting defective areas by region growing segmentation operation according to the image data, and marking the defective areas by 8-neighborhood connectivity if the grayscale difference between adjacent pixels is less than a preset threshold; Using the Sobel operator to process the marked area, a defect boundary point set is obtained, wherein the defect boundary point set contains spatial coordinate information of the defect contour; According to the spatial coordinate information of the defect boundary point set, the principal axis direction determination method is adopted to calculate the minimum enclosing rectangle, and the defect characteristic parameters are obtained through the length parameter and width parameter of the minimum enclosing rectangle. The defect characteristic parameters include the defect position coordinates, defect size and shape characteristic values.

5. The method according to claim 1, characterized in that The external geometric model of the metal code disk obtained by three-dimensional scanning is integrated with the internal defect information of the metal code disk obtained by X-ray flaw detection to construct a three-dimensional model of the metal code disk containing internal defects, including: The coordinate system of the three-dimensional external geometric model of the metal code disk is registered with the coordinate system of the X-ray tomography image to establish a spatial mapping relationship between the three-dimensional model and the tomography image; According to the spatial position relationship between the 3D external model and the internal defect information in a unified coordinate system, the defect information is mapped to the corresponding position of the 3D external model to achieve the fusion of the defect information and the 3D model; Perform meshing and surface reconstruction on the fused 3D model to optimize the size and distribution of triangular facets; According to the three-dimensional size parameters of the defect information, a three-dimensional entity that matches the size and shape of the defect area is constructed in the three-dimensional model, and the three-dimensional entity is embedded into the corresponding position of the three-dimensional model to obtain a three-dimensional solid model of the metal code disk containing internal defects; The 3D solid model is rendered, the surface of the model is texture mapped according to the material properties of the metal code disk, and the lighting and material parameters are set to generate a realistic 3D model of the metal code disk.

6. The method according to claim 1, characterized in that According to the material properties and structural parameters of the metal code disk, the three-dimensional model of the metal code disk is meshed and boundary conditions are set to simulate the stress condition of the code disk under the actual working state, analyze the influence of internal defects on the stress distribution of the code disk, and judge whether there is stress concentration around the defects, including: The metal code disk model is meshed by using a twenty-node hexahedral unit, and the side length of the basic grid obtained by the meshing is the grid size of the code disk model; The basic grid is encrypted layer by layer in the defective area, and the quality of the grid in the defective area is greater than the preset Jacobian matrix threshold; The boundary conditions of the code disc are set according to the mesh generation results, and the freedom constraints of the nodes of the code disc model are obtained by applying fixed constraints on the mounting surface of the code disc bearing. Applying an axial sine load and a radial cosine load to the code disc according to the node freedom constraints of the code disc model to obtain a code disc load distribution; Performing transient response calculation on the load distribution of the code disc through an explicit integral solver, setting the mass damping coefficient and the stiffness damping coefficient according to the transient response calculation, and obtaining the calculation step length result of the code disc model; Iterate the calculation step size of the encoder model and obtain the steady-state response result of the encoder model by judging the node displacement and stress convergence error. The stress value of the defect edge is extracted based on the steady-state response result of the code disk model. If the stress value of the defect edge simultaneously satisfies the conditions that the stress value is greater than the preset stress threshold, the stress gradient is greater than the preset gradient threshold, and the principal stress ratio is greater than the preset ratio threshold, the grid node number of the stress concentration area is marked to obtain the position coordinates of the maximum stress value in the stress concentration area.

7. The method according to claim 1, characterized in that If there is stress concentration around the defect, the fracture mechanics theory is used to analyze the stability of the internal defects of the metal code disk and calculate the stress intensity factor at the tip of the defect, including: Degenerate quadrilateral singular units are used to mesh the defect tip area, the midpoint node position coordinates of the degenerate quadrilateral singular unit are offset toward the tip by one quarter of the side length, transition units are arranged around the degenerate quadrilateral singular unit, and the unit size increases gradually from the inside to the outside according to a set ratio; A three-dimensional displacement field is calculated according to the grid division result, displacement sampling points are arranged along the circumferential direction in the three-dimensional displacement field, and the stress intensity factor is obtained by least square fitting of the radial displacement of the displacement sampling points.

8. The method according to claim 7, characterized in that The risk of crack propagation under external force is assessed, and the critical size and safety margin of the defect are determined, including: Calculating the crack propagation driving force according to the stress intensity factor, and obtaining the crack propagation direction by using the maximum circumferential stress criterion through the crack propagation driving force; In the crack propagation direction, the energy release rate is calculated by J-integral on a circular path, and the J-integral adopts a set integral path radius; The defect size is analyzed parametrically, and a safety margin is obtained by the ratio of the mixed mode stress intensity factor to the critical value. If the safety margin is greater than a set value, it is determined to be a stable state.

9. The method according to claim 1, characterized in that: According to the critical size and safety margin of the defect and the actual working conditions and failure modes of the metal code disk, a safety assessment criterion is formulated. The safety assessment criterion includes regular detection and tracking evaluation of the defect status of the code disk, timely discovery of the defect expansion trend, prediction of the remaining service life of the code disk, and providing a decision-making basis for the maintenance and replacement of the code disk, including: The Paris crack growth rate curve is constructed based on the fracture toughness value and stress intensity factor of the metal encoder, and the crack growth rate coefficient and crack growth index are obtained through cyclic loading; An internal defect image of the metal code disk is obtained by an X-ray flaw detector, the internal defect image is processed by Gaussian filtering to obtain a filtered image, and a Canny edge detection operator is used to extract defect contour features from the filtered image; Performing exponential function fitting on the defect contour characteristics, calculating the functional relationship between the crack growth rate and the stress intensity factor according to the fitting result, and establishing a defect tip stress intensity factor database; querying the stress state of the defect tip according to the defect tip stress intensity factor database, determining the critical size of the defect based on the fracture toughness criterion, and obtaining the real-time defect size from the defect contour feature; The life distribution probability of the real-time defect size is calculated by using the Monte Carlo method. If the real-time defect size is larger than a preset threshold or the crack growth rate exceeds a preset rate threshold, a maintenance instruction is triggered.

10. The method according to claim 1, characterized in that The method of obtaining the defect distribution law of the metal code disk according to the internal defect information of the metal code disk, and optimizing the structural layout and key dimensional parameters of the metal code disk in combination with the defect distribution law of the metal code disk and the safety assessment criteria, includes: Receiving metal code disk defect data, analyzing the metal code disk defect data by using a DBSCAN density clustering algorithm to obtain high-risk area coordinate information; A parameterized geometric structure model is established according to the coordinate information of the high-risk area, and the geometric structure model is optimized by using a BESO topology optimization method to obtain an initial topology structure; According to the initial topological structure, the hub thickness, the wheel rim inclination angle and the number of ribs are set, and the stress distribution data is obtained by tetrahedral meshing calculation; Design an L16 orthogonal test scheme according to the stress distribution data, and obtain the Mises stress value and stress gradient value under each parameter combination through the orthogonal test; According to the Mises stress value and stress gradient value, the NSGA-II algorithm is used to perform multi-objective optimization calculation to obtain the optimal structural parameters that meet the stress limit and quality objectives.

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