A valve seal face defect detection method and system

Abstract

This invention relates to the field of defect detection technology, specifically a method and system for detecting defects in valve sealing surfaces. The method extracts the position coordinates, geometric contours, and depth parameters of each abnormal morphology region from the three-dimensional surface morphology data of the sealing surface of the valve under inspection; determines the theoretical sealing contact area of ​​the sealing surface in the valve-closed state and spatially maps it with the position coordinates of each abnormal morphology region to filter out the abnormal regions to be judged; calculates the effective contact surface geometry after elastic deformation of the sealing surface under working conditions; based on the depth parameters and effective contact surface geometry of each abnormal region to be judged, if it is determined that the abnormal region to be judged is not completely covered by the effective contact surface after elastic deformation compensation, then the abnormal region to be judged is marked as a functional defect region and the detection result is output; accurately determining whether the abnormal morphology regions on the sealing surface constitute functional defects affecting the sealing function improves the accuracy of valve sealing surface defect detection.

Description

Technical Field

[0001] This invention relates to the field of defect detection technology, specifically a method and system for detecting defects in valve sealing surfaces. Background Technology

[0002] Valves are core components in industrial pipeline systems used to control the flow and cut off of media. The integrity of their sealing surfaces directly determines whether the valve can achieve a reliable seal when closed. During the manufacturing, assembly, and long-term service of valves, surface morphology abnormalities such as scratches, pitting, and cracks inevitably occur on the sealing surfaces. If these abnormalities are located within the sealing contact area and reach a certain extent, they will cause media leakage after the valve is closed, leading to safety accidents or production losses. Therefore, defect detection of valve sealing surfaces and accurate identification of functional defects affecting sealing function are important aspects of valve quality control and in-service maintenance.

[0003] However, existing detection methods generally equate abnormal morphological areas on the sealing surface directly with functional defects. That is, any morphological deviation exceeding a certain size threshold is considered a defect. Furthermore, they ignore the fact that in actual operation, the sealing pair undergoes elastic deformation under the combined effects of closing load and operating temperature. The actual contact area and contact morphology of the sealing surface differ significantly from its static geometry. Morphological abnormalities that were not covered by the contact surface under static conditions may be completely compensated for by the effective contact surface after elastic deformation, no longer constituting a defect affecting the sealing function. This leads to a large number of morphological abnormalities located in non-contact areas, which have no substantial impact on the sealing function, being misjudged as functional defects, resulting in over-detection. Summary of the Invention

[0004] (1) Technical problems to be solved

[0005] The purpose of this invention is to provide a method and system for detecting defects on valve sealing surfaces, so as to solve the problem that it is impossible to accurately distinguish whether surface defects actually affect the sealing function in valve sealing surface detection.

[0006] (2) Technical solution

[0007] To achieve the above objectives, in one aspect, the present invention provides a method for detecting defects on a valve sealing surface, the method comprising:

[0008] S1. Acquire images of the sealing surface of the valve to be inspected to obtain three-dimensional surface morphology data of the sealing surface; process the three-dimensional surface morphology data to extract the position coordinates, geometric contours and depth parameters of each abnormal morphology area on the sealing surface.

[0009] S2. Determine the theoretical sealing contact area of ​​the sealing surface in the closed state of the valve based on the structural type and geometric model of the valve to be inspected; spatially map the position coordinates of each abnormal morphology area to the theoretical sealing contact area, and select the abnormal morphology areas located in the theoretical sealing contact area as abnormal areas to be judged.

[0010] S3. Obtain the sealing pair material parameters and operating condition parameters of the valve to be inspected, and calculate the effective contact surface geometry after the sealing surface undergoes elastic deformation under working conditions based on the sealing pair material parameters and operating condition parameters.

[0011] S4. Based on the depth parameters and effective contact surface geometry of each abnormal area to be judged, if it is determined that the abnormal area to be judged is not completely covered by the effective contact surface after elastic deformation compensation, then the abnormal area to be judged is marked as a functional defect area and the detection result is output.

[0012] Furthermore, the method for calculating the effective contact surface geometry of the sealing surface after elastic deformation under working conditions based on the sealing pair material parameters and operating condition parameters includes:

[0013] The three-dimensional geometry of the sealing surface is reconstructed from the three-dimensional surface topography data, and a finite element model of the sealing pair is constructed by combining the three-dimensional geometry of the paired sealing pair. The elastic modulus and hardness of the sealing pair material parameters are used as input parameters for the constitutive relations of the materials of the sealing surface and the paired sealing pair in the finite element model of the sealing pair contact. The valve closing load in the operating condition parameters is applied to the finite element model of the sealing pair contact as a boundary condition. The operating temperature in the operating condition parameters is applied to the finite element model of the sealing pair contact as a temperature field load. The thermal deformation of the sealing surface and the paired sealing pair at the operating temperature is calculated by using the coefficient of thermal expansion.

[0014] In the finite element model of the sealing pair contact, the thermal deformation is superimposed with the mechanical deformation caused by the valve closing load to obtain the deformation displacement distribution of the sealing surface under working conditions. Based on the deformation displacement distribution, the three-dimensional geometry of the sealing surface is corrected, and the area enclosed by the set of nodes where the gap between the corrected sealing surface and the mating sealing pair is lower than the gap judgment threshold is extracted as the effective contact surface geometry.

[0015] Furthermore, the method of reconstructing the three-dimensional geometry of the sealing surface based on the three-dimensional surface topography data and constructing a finite element model of the sealing pair contact based on the three-dimensional geometry of the mating sealing pair of the valve under test includes:

[0016] Point cloud filtering is performed on the three-dimensional surface topography data to obtain effective point cloud data that characterizes the true geometric shape of the sealing surface; the effective point cloud data is then fitted using a surface reconstruction algorithm to generate a parametric surface model of the sealing surface.

[0017] Using the parametric surface model of the sealing surface as the geometric boundary, the sealing surface region is meshed to obtain a finite element mesh model of one side of the sealing surface.

[0018] The three-dimensional geometry of the mating sealing pair is meshed to obtain a finite element mesh model of one side of the mating sealing pair. The finite element mesh model of the sealing surface side and the finite element mesh model of the mating sealing pair side are spatially aligned according to their assembly position relationship when the valve is closed. A contact pair relationship is established between the surface nodes of the two sides that are in contact with each other and the friction coefficient is set to construct the finite element model of the sealing pair contact.

[0019] Furthermore, the method for generating a parametric surface model of the sealing surface by fitting effective point cloud data using a surface reconstruction algorithm includes:

[0020] Using each sampling point in the effective point cloud data as the center, search for the nearest neighboring points in the search space to form a local neighborhood point set; obtain the initial normal vector field of all sampling points through principal component analysis of the local neighborhood point set of each sampling point.

[0021] Taking the orientation of the normal vector at the outer contour boundary of the effective point cloud data as the propagation starting point, the orientation of the normal vector of each sampling point is corrected point by point according to the propagation criterion of minimizing the angle between the normal vectors of neighboring points, so that the initial normal vector field of all sampling points points uniformly points to the same side of the sealing surface, thus obtaining a uniformly oriented normal vector field; using the uniformly oriented normal vector field as a constraint, the effective point cloud data is transformed into an isosurface expressed by an implicit function, and the mesh representation at the zero isosurface is extracted to obtain the initial reconstructed surface.

[0022] The initial reconstructed surface is parametrically mapped according to the sealing surface structure type. The three-dimensional spatial coordinates of each grid vertex are converted into the corresponding two-dimensional parametric coordinates in the parameter domain. The two-dimensional parametric coordinates of each grid vertex are used as independent variables and the corresponding three-dimensional spatial coordinates are used as dependent variables. The mapping function from the parameter domain to the three-dimensional space is established by least squares fitting, and the parametric surface model of the sealing surface is obtained.

[0023] Furthermore, the method of using the parametric curved surface model of the sealing surface as the geometric boundary to mesh the sealing surface region to obtain a finite element mesh model of one side of the sealing surface includes:

[0024] The curvature values ​​at various locations on the parametric surface model of the sealing surface are calculated to obtain the global curvature distribution. The target local mesh size is assigned to each location according to the monotonically decreasing mapping relationship between the curvature value and the target mesh size, thus obtaining the target mesh size distribution. Using the outer contour boundary of the parametric surface model of the sealing surface as the constraint boundary, an initial planar triangular mesh is generated in the parameter domain of the parametric surface model of the sealing surface based on the target mesh size distribution. The parameter coordinates of each vertex of the initial planar triangular mesh are mapped back to the three-dimensional spatial coordinates of the parametric surface model of the sealing surface to obtain the surface mesh.

[0025] The surface mesh is inspected for quality. Mesh elements with aspect ratio or distortion exceeding the preset quality threshold are identified as substandard elements. The node positions of substandard elements are subjected to Laplace smoothing iteration along the tangent plane of the parametric surface model of the sealing surface until the quality index of all mesh elements meets the preset quality threshold. The surface mesh is then stretched along the normal direction of the sealing surface and divided into several layers of solid elements in the thickness direction to obtain the finite element mesh model of one side of the sealing surface.

[0026] Furthermore, the method of correcting the three-dimensional geometry of the sealing surface based on the deformation displacement distribution and extracting the region enclosed by the set of nodes where the gap between the corrected sealing surface and the mating sealing pair is lower than the gap determination threshold as the effective contact surface geometry includes:

[0027] The displacement vectors of each node on the sealing surface in the deformation displacement distribution are superimposed one by one onto the initial coordinates of the corresponding node in the three-dimensional geometry of the sealing surface to obtain the deformed coordinates of each node on the sealing surface under working conditions. The modified three-dimensional geometry of the sealing surface under working conditions is reconstructed from the deformed coordinates. Using the coordinates of each node in the modified three-dimensional geometry of the sealing surface as a reference, the normal gap value between the node and the mating sealing surface is calculated along the normal vector direction of each node to obtain the normal gap distribution map of the entire sealing surface.

[0028] The normal gap distribution map is subjected to threshold segmentation processing. Nodes with normal gap values ​​lower than the gap determination threshold are marked as contact nodes, and nodes with normal gap values ​​higher than the gap determination threshold are marked as non-contact nodes.

[0029] The region enclosed by the outer contour of the set of interconnected contact nodes in space is extracted as a candidate effective contact surface. The node contact pressure distribution of each candidate effective contact surface is verified, and the candidate effective contact surfaces that pass the verification are merged and output as the effective contact surface geometry.

[0030] Furthermore, the method for determining the gap determination threshold includes:

[0031] The compression deformation characteristic parameters of the soft sealing material in the mating sealing pair are extracted from the sealing pair material parameters. The compression deformation characteristic parameters include the correspondence between the compressive stress and compressive strain of the soft sealing material under the corresponding contact pressure of the operating condition parameters. The nominal contact pressure at the sealing surface is calculated based on the valve closing load and the theoretical sealing contact area of ​​the sealing surface in the operating condition parameters. The nominal contact pressure is substituted into the correspondence between the compressive stress and compressive strain to obtain the compressive strain value of the soft sealing material under the nominal contact pressure. The amount of compression deformation of the soft sealing material under the nominal contact pressure is calculated based on the compressive strain value and the initial thickness of the soft sealing material in the thickness direction. The amount of compression deformation is determined as the gap judgment threshold.

[0032] Furthermore, the method for determining the theoretical sealing contact area of ​​the sealing surface in the closed state based on the structural type and geometric model of the valve to be inspected includes:

[0033] Obtain the structural type identifier of the valve to be inspected, and retrieve the standard geometric model corresponding to the structural type of the valve to be inspected from the pre-stored valve geometric model library based on the structural type identifier.

[0034] Based on the sealing contact form corresponding to the structural type of the valve under test, the initial position of the theoretical contact line between the sealing surface and the mating sealing pair is extracted. The initial theoretical sealing contact area is obtained by expanding the preset contact width margin outward from the initial position of the theoretical contact line.

[0035] The projection of the geometric interference region in the valve closed state is calculated based on the nominal geometry of the sealing surface and the mating sealing pair in the standard geometric model. The intersection of the projection of the geometric interference region with the initial theoretical sealing contact area is taken to obtain the area range in which the sealing surface and the mating sealing pair actually make geometric contact in the valve closed state, and this area is recorded as the theoretical sealing contact area.

[0036] Furthermore, the method for calculating the projection of the geometric interference region in the valve-closed state based on the nominal geometric shapes of the sealing surface and the mating sealing pair in the standard geometric model includes:

[0037] The nominal geometry of the sealing surface and the nominal geometry of the mating sealing pair in the standard geometric model are spatially aligned according to their relative assembly positions in the valve closed state to obtain the initial assembly position of the sealing surface and the mating sealing pair. Based on the initial assembly position, the valve closing stroke displacement is applied along the direction in which the sealing surface and the mating sealing pair approach each other. The normal distance between each sampling point on the nominal geometry of the sealing surface and the nominal geometry surface of the mating sealing pair is calculated one by one to obtain the normal distance distribution of the entire sealing surface.

[0038] Sampling points with normal distance values ​​less than zero in the normal distance distribution are marked as interference points to obtain the set of interference points; spatially connected interference points are merged into the same interference region, and the projection range of each interference region on the nominal geometry of the sealing surface is obtained by using the outer contour of each interference region as the boundary; the projection range of all interference regions is merged to obtain the projection of the geometric interference region.

[0039] On the other hand, based on the same inventive concept, this invention also provides a valve sealing surface defect detection system, the system comprising:

[0040] The sealing surface image acquisition and data processing module is used to acquire images of the sealing surface of the valve under inspection to obtain three-dimensional surface morphology data of the sealing surface; and to process the three-dimensional surface morphology data to extract the position coordinates, geometric contours and depth parameters of each abnormal morphology area on the sealing surface.

[0041] The abnormal area screening module is used to determine the theoretical sealing contact area of ​​the sealing surface in the closed state of the valve based on the structural type and geometric model of the valve to be inspected; the position coordinates of each abnormal area are spatially mapped to the theoretical sealing contact area, and the abnormal areas located within the theoretical sealing contact area are screened out as abnormal areas to be judged.

[0042] The effective contact surface geometry calculation module is used to obtain the sealing pair material parameters and operating condition parameters of the valve under test, and calculate the effective contact surface geometry after the sealing surface undergoes elastic deformation under working conditions based on the sealing pair material parameters and operating condition parameters.

[0043] The functional defect area judgment and result output module is used to determine, based on the depth parameters and effective contact surface geometry of each abnormal area to be judged, if the abnormal area to be judged is not completely covered by the effective contact surface after elastic deformation compensation, then mark the abnormal area to be judged as a functional defect area and output the detection result.

[0044] (3) Beneficial effects

[0045] Compared with the prior art, the beneficial effects of the present invention are:

[0046] 1. By determining the theoretical sealing contact area based on the valve structure type and geometric model, and mapping the spatial coordinates of each abnormal morphological area on the sealing surface to the theoretical sealing contact area, the detection target is narrowed from the morphological abnormalities of the entire sealing surface to the abnormal areas to be judged only within the theoretical sealing contact area. This fundamentally eliminates the possibility of morphological deviations in non-contact areas that have no substantial impact on the sealing function being misjudged as functional defects, significantly reducing the over-detection rate and making the detection conclusions closer to the actual needs of the valve sealing function.

[0047] 2. By constructing a finite element model of the sealing pair contact, and comprehensively considering the coupling effect of multiple factors such as the elastic modulus of the sealing pair material, the valve closing load, and the thermal deformation caused by the working temperature, the effective contact surface geometry after elastic deformation of the sealing surface under actual working conditions is calculated. Based on this, it is determined whether the abnormal area to be judged has been completely compensated and covered by the effective contact surface, so that the defect judgment is based on the dynamic contact state consistent with the actual working conditions. Attached Figure Description

[0048] Figure 1 This is a flowchart of a valve sealing surface defect detection method according to the present invention.

[0049] Figure 2 This is a schematic diagram of the module composition of a valve sealing surface defect detection system according to the present invention. Detailed Implementation

[0050] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0051] Example 1: As Figure 1 As shown in the figure, this embodiment provides a method for detecting defects on a valve sealing surface, the method comprising:

[0052] S1. Acquire images of the sealing surface of the valve to be inspected to obtain three-dimensional surface morphology data of the sealing surface; process the three-dimensional surface morphology data to extract the position coordinates, geometric contours and depth parameters of each abnormal morphology area on the sealing surface.

[0053] For example, a 3D laser scanner or other instrument with 3D measurement capabilities is used to scan the sealing surface of the valve under inspection to obtain 3D surface topography data. This 3D surface topography data is then analyzed and processed to extract the position coordinates, geometric contours, and depth parameters of each abnormal area on the sealing surface. Position coordinates refer to the spatial location of the abnormal area in the sealing surface coordinate system; geometric contours refer to the boundary shape of the abnormal area on the sealing surface; and depth parameters refer to the maximum deviation of the abnormal area from the nominal reference surface of the sealing surface, indicating whether it is concave inward or convex outward.

[0054] S2. Determine the theoretical sealing contact area of ​​the sealing surface in the closed state of the valve based on the structural type and geometric model of the valve to be inspected.

[0055] The method for determining the theoretical sealing contact area of ​​the sealing surface in the closed state of the valve based on the structural type and geometric model of the valve to be tested includes:

[0056] Obtain the structural type identifier of the valve to be inspected, and retrieve the standard geometric model corresponding to the structural type of the valve to be inspected from the pre-stored valve geometric model library based on the structural type identifier.

[0057] Based on the sealing contact form corresponding to the structural type of the valve under test, the initial position of the theoretical contact line between the sealing surface and the mating sealing pair is extracted. The initial theoretical sealing contact area is obtained by expanding the preset contact width margin outward from the initial position of the theoretical contact line.

[0058] The projection of the geometric interference region in the valve closed state is calculated based on the nominal geometry of the sealing surface and the mating sealing pair in the standard geometric model. The intersection of the projection of the geometric interference region with the initial theoretical sealing contact area is taken to obtain the area range in which the sealing surface and the mating sealing pair actually make geometric contact in the valve closed state, and this area is recorded as the theoretical sealing contact area.

[0059] The method for calculating the projection of the geometric interference region in the valve closed state based on the nominal geometric shapes of the sealing surface and the mating sealing pair in the standard geometric model includes:

[0060] The nominal geometry of the sealing surface and the nominal geometry of the mating sealing pair in the standard geometric model are spatially aligned according to their relative assembly positions in the valve closed state to obtain the initial assembly position of the sealing surface and the mating sealing pair. Based on the initial assembly position, the valve closing stroke displacement is applied along the direction in which the sealing surface and the mating sealing pair approach each other. The normal distance between each sampling point on the nominal geometry of the sealing surface and the nominal geometry surface of the mating sealing pair is calculated one by one to obtain the normal distance distribution of the entire sealing surface.

[0061] Sampling points with normal distance values ​​less than zero in the normal distance distribution are marked as interference points to obtain the set of interference points; spatially connected interference points are merged into the same interference region, and the projection range of each interference region on the nominal geometry of the sealing surface is obtained by using the outer contour of each interference region as the boundary; the projection range of all interference regions is merged to obtain the projection of the geometric interference region.

[0062] The location coordinates of each abnormal morphology area are spatially mapped to the theoretical sealing contact area. Abnormal morphology areas located within the theoretical sealing contact area are selected as abnormal areas to be judged; other abnormal morphology areas located outside the theoretical sealing contact area are directly excluded.

[0063] For example, taking a gate valve as an example, its sealing contact is a contact between a conical surface and a planar line, and the corresponding standard geometric model includes the nominal geometric parameters of the valve disc conical surface and the valve seat plane; taking a gate valve as an example, its sealing contact is a surface contact between two parallel planes, and the corresponding standard geometric model includes the nominal geometric parameters of the sealing surfaces of the two gates. The value of the contact width margin is determined according to the valve type and the tolerance grade of the sealing surface, and is usually taken in the range of 0.1 mm to 0.5 mm. The purpose is to reserve a certain width on both sides of the theoretical contact line to cover the contact position offset caused by manufacturing errors.

[0064] The valve closing stroke displacement is determined according to the closing stroke value marked in the valve model instruction manual. The normal distance is calculated by projecting the sampling point of the sealing surface along the normal vector direction of that point onto the nominal curved surface of the mating sealing pair. A positive value indicates that the two surfaces have not yet intersected, and a negative value indicates that the two surfaces have geometrically interfered.

[0065] S3. Obtain the sealing pair material parameters and operating condition parameters of the valve to be inspected, and calculate the effective contact surface geometry after the sealing surface undergoes elastic deformation under working conditions based on the sealing pair material parameters and operating condition parameters.

[0066] The method for calculating the effective contact surface geometry of the sealing surface after elastic deformation under working conditions based on the sealing pair material parameters and operating condition parameters includes:

[0067] The three-dimensional geometry of the sealing surface is reconstructed from the three-dimensional surface topography data, and a finite element model of the sealing pair contact is constructed by combining the three-dimensional geometry of the paired sealing pair.

[0068] The method for reconstructing the three-dimensional geometry of the sealing surface based on three-dimensional surface topography data, and constructing a finite element model of the sealing pair contact based on the three-dimensional geometry of the mating sealing pair of the valve under test, includes:

[0069] Point cloud filtering is performed on the three-dimensional surface topography data to obtain effective point cloud data that characterizes the true geometric shape of the sealing surface; the effective point cloud data is then fitted using a surface reconstruction algorithm to generate a parametric surface model of the sealing surface.

[0070] The method for generating a parametric surface model of the sealing surface by fitting effective point cloud data using a surface reconstruction algorithm includes:

[0071] Using each sampling point in the effective point cloud data as the center, search for the nearest neighboring points in the search space to form a local neighborhood point set; obtain the initial normal vector field of all sampling points through principal component analysis of the local neighborhood point set of each sampling point.

[0072] Taking the orientation of the normal vector at the outer contour boundary of the effective point cloud data as the propagation starting point, the orientation of the normal vector of each sampling point is corrected point by point according to the propagation criterion of minimizing the angle between the normal vectors of neighboring points, so that the initial normal vector field of all sampling points points uniformly points to the same side of the sealing surface, thus obtaining a uniformly oriented normal vector field; using the uniformly oriented normal vector field as a constraint, the effective point cloud data is transformed into an isosurface expressed by an implicit function, and the mesh representation at the zero isosurface is extracted to obtain the initial reconstructed surface.

[0073] The initial reconstructed surface is parametrically mapped according to the sealing surface structure type. The three-dimensional spatial coordinates of each grid vertex are converted into the corresponding two-dimensional parametric coordinates in the parameter domain. The two-dimensional parametric coordinates of each grid vertex are used as independent variables and the corresponding three-dimensional spatial coordinates are used as dependent variables. The mapping function from the parameter domain to the three-dimensional space is established by least squares fitting, and the parametric surface model of the sealing surface is obtained.

[0074] Using the parametric surface model of the sealing surface as the geometric boundary, the sealing surface region is meshed to obtain a finite element mesh model of one side of the sealing surface;

[0075] The method of obtaining a finite element mesh model of one side of the sealing surface by meshing the sealing surface region using a parametric curved surface model of the sealing surface as the geometric boundary includes:

[0076] The curvature values ​​at various locations on the parametric surface model of the sealing surface are calculated to obtain the global curvature distribution. The target local mesh size is assigned to each location according to the monotonically decreasing mapping relationship between the curvature value and the target mesh size, thus obtaining the target mesh size distribution. Using the outer contour boundary of the parametric surface model of the sealing surface as the constraint boundary, an initial planar triangular mesh is generated in the parameter domain of the parametric surface model of the sealing surface based on the target mesh size distribution. The parameter coordinates of each vertex of the initial planar triangular mesh are mapped back to the three-dimensional spatial coordinates of the parametric surface model of the sealing surface to obtain the surface mesh.

[0077] The surface mesh is inspected for quality. Mesh elements with aspect ratio or distortion exceeding the preset quality threshold are identified as substandard elements. The node positions of substandard elements are subjected to Laplace smoothing iteration along the tangent plane of the parametric surface model of the sealing surface until the quality index of all mesh elements meets the preset quality threshold. The surface mesh is then stretched along the normal direction of the sealing surface and divided into several layers of solid elements in the thickness direction to obtain the finite element mesh model of one side of the sealing surface.

[0078] The three-dimensional geometry of the mating sealing pair is meshed to obtain a finite element mesh model of one side of the mating sealing pair. The finite element mesh model of the sealing surface side and the finite element mesh model of the mating sealing pair side are spatially aligned according to their assembly position relationship when the valve is closed. A contact pair relationship is established between the surface nodes of the two sides that are in contact with each other and the friction coefficient is set to construct the finite element model of the sealing pair contact.

[0079] The elastic modulus and hardness of the sealing pair material parameters are used as input parameters for the constitutive relations of the sealing surface and the mating sealing pair in the finite element model of the sealing pair contact. The valve closing load in the operating condition parameters is applied to the finite element model of the sealing pair contact as a boundary condition. The operating temperature in the operating condition parameters is applied to the finite element model of the sealing pair contact as a temperature field load. The thermal deformation of the sealing surface and the mating sealing pair at the operating temperature is calculated by the coefficient of thermal expansion.

[0080] In the finite element model of the sealing pair contact, the thermal deformation is superimposed with the mechanical deformation caused by the valve closing load to obtain the deformation displacement distribution of the sealing surface under working conditions. Based on the deformation displacement distribution, the three-dimensional geometry of the sealing surface is corrected, and the area enclosed by the set of nodes where the gap between the corrected sealing surface and the mating sealing pair is lower than the gap judgment threshold is extracted as the effective contact surface geometry.

[0081] The method of correcting the three-dimensional geometry of the sealing surface based on the deformation displacement distribution and extracting the region enclosed by the set of nodes where the gap between the corrected sealing surface and the mating sealing pair is lower than the gap determination threshold as the effective contact surface geometry includes:

[0082] The displacement vectors of each node on the sealing surface in the deformation displacement distribution are superimposed one by one onto the initial coordinates of the corresponding node in the three-dimensional geometry of the sealing surface to obtain the deformed coordinates of each node on the sealing surface under working conditions. The modified three-dimensional geometry of the sealing surface under working conditions is reconstructed from the deformed coordinates. Using the coordinates of each node in the modified three-dimensional geometry of the sealing surface as a reference, the normal gap value between the node and the mating sealing surface is calculated along the normal vector direction of each node to obtain the normal gap distribution map of the entire sealing surface.

[0083] The normal gap distribution map is subjected to threshold segmentation processing. Nodes with normal gap values ​​lower than the gap determination threshold are marked as contact nodes, and nodes with normal gap values ​​higher than the gap determination threshold are marked as non-contact nodes.

[0084] The method for determining the gap determination threshold includes:

[0085] The compression deformation characteristic parameters of the soft sealing material in the mating sealing pair are extracted from the sealing pair material parameters. The compression deformation characteristic parameters include the correspondence between the compressive stress and compressive strain of the soft sealing material under the corresponding contact pressure of the operating condition parameters. The nominal contact pressure at the sealing surface is calculated based on the valve closing load and the theoretical sealing contact area of ​​the sealing surface in the operating condition parameters. The nominal contact pressure is substituted into the correspondence between the compressive stress and compressive strain to obtain the compressive strain value of the soft sealing material under the nominal contact pressure. The amount of compression deformation of the soft sealing material under the nominal contact pressure is calculated based on the compressive strain value and the initial thickness of the soft sealing material in the thickness direction. The amount of compression deformation is determined as the gap judgment threshold.

[0086] The region enclosed by the outer contour of the set of interconnected contact nodes in space is extracted as a candidate effective contact surface. The node contact pressure distribution of each candidate effective contact surface is verified, and the candidate effective contact surfaces that pass the verification are merged and output as the effective contact surface geometry.

[0087] For example, the obtained three-dimensional surface topography data is subjected to point cloud filtering to remove scanning noise and outliers, resulting in effective point cloud data that characterizes the true geometry of the sealing surface. A parameterized surface model of the sealing surface is generated by fitting the effective point cloud data using a surface reconstruction algorithm. The specific process is as follows: Using each sampling point in the effective point cloud data as the center, search for the nearest neighboring points to form a local neighborhood point set. The number of neighboring points is usually 10 to 20 to ensure sufficient description of local geometric features. Principal component analysis is used to obtain the initial normal vector field of all sampling points from the local neighborhood point set of each sampling point. The eigenvector corresponding to the minimum eigenvalue in the principal component analysis is the normal vector estimate at that point. Taking the orientation of the normal vector at the outer contour boundary of the effective point cloud data as the propagation starting point, the orientation of the normal vector of each sampling point is corrected point by point according to the propagation criterion of minimizing the angle between the normal vectors of neighboring points, so that the initial normal vector field of all sampling points uniformly points to the same side of the sealing surface, resulting in a uniformly oriented normal vector field. This step solves the problem of random flipping of the direction of the point cloud normal vector due to independent local estimation. For rotationally symmetric sealing surfaces, the parameter domain is usually selected as a polar coordinate system composed of radial distance and circumferential angle; for planar sealing surfaces, the parameter domain is usually selected as a two-dimensional plane in a rectangular coordinate system.

[0088] The preset quality thresholds used for mesh quality inspection are determined as follows: the aspect ratio threshold is 3, meaning the ratio of the longest side to the shortest side of the mesh element does not exceed 3. This value is determined with reference to the engineering conventions for ensuring the accuracy of contact pressure calculation in general finite element contact analysis; the torsion threshold is 0.7, meaning the normalization index of the deviation between the actual shape and the ideal shape of the mesh element does not exceed 0.7 (where 0 represents the ideal shape and 1 represents complete degradation). This value is determined based on the convergence requirements of the stress concentration region in the finite element analysis of sealing surface contact. The above quality thresholds are verified by mesh generation sensitivity analysis of typical valve sealing surface geometry to ensure that the influence of mesh quality on the effective contact surface calculation results is less than 5%.

[0089] The number of solid unit layers in the thickness direction is determined based on the ratio of the sealing surface thickness to the average side length of the surface mesh, and is no less than 3 layers, to ensure that the stress gradient in the thickness direction can be fully distinguished and that the length-to-thickness ratio of each unit layer meets the quality threshold requirements.

[0090] In terms of finite element mesh generation, the parametric surface model of the sealing surface is used as the geometric boundary. The curvature values ​​at various locations on the parametric surface model of the sealing surface are calculated to obtain the global curvature distribution. Areas with larger curvature exhibit drastic local geometric changes, requiring a denser mesh to accurately describe the surface shape. Therefore, the target local mesh size is assigned to each location according to the monotonically decreasing mapping relationship between curvature values ​​and target mesh size. The three-dimensional geometry of the paired sealing pair is meshed in the same way to obtain the finite element mesh model of one side of the paired sealing pair. The value of the friction coefficient is determined based on the material pairing type of the sealing pair. For example, the friction coefficient between a stainless steel sealing surface and a hard alloy paired sealing pair is typically 0.1 to 0.2; between stainless steel and PTFE soft seals, it is 0.04 to 0.08; and between copper alloys and cast iron, it is 0.15 to 0.25.

[0091] The formula for calculating heat deformation is: ;in, This is the amount of thermal deformation. The coefficient of thermal expansion of the material. These are the initial dimensions of the component at the reference temperature. This is the difference between the operating temperature and the reference temperature.

[0092] Extract the relationship between compressive stress and compressive strain of the soft sealing material in the mating sealing pair under the corresponding contact pressure according to the operating conditions; based on the valve closing load in the operating conditions... Theoretical sealing contact area with the sealing surface The nominal contact pressure at the sealing surface was calculated. : ; to nominally contact pressure Substituting the relationship between compressive stress and compressive strain, we obtain the compressive strain value of the soft sealing material under the nominal contact pressure. Based on the compressive strain value Initial thickness of the soft sealing material in the thickness direction The compressive deformation of the soft sealing material under nominal contact pressure was calculated. : ; to compress deformation The clearance threshold is defined as the maximum compressive deformation that a soft sealing material can produce under nominal contact pressure. This is the upper limit of its ability to fill the local gap between the sealing surface and the mating sealing pair. Areas with normal clearances below the clearance threshold can achieve effective contact under operating conditions through the compressive deformation of the soft sealing material. The verification criteria for the node contact pressure distribution are as follows: the contact pressure of all contact nodes on the candidate effective contact surface is greater than zero, and the area-weighted average of the contact pressures within the candidate effective contact surface is not less than the minimum sealing pressure required by the sealing pair material. The minimum sealing pressure is determined from the sealing material standard based on the type of soft sealing material in the sealing pair. For all-metal sealing pairs without soft seals, the minimum sealing pressure is taken as 0.5 times the nominal contact pressure. Candidate effective contact surfaces that fail the verification (such as a set of isolated nodes with zero contact pressure) are judged as pseudo-contact areas and are eliminated.

[0093] S4. Based on the depth parameters and effective contact surface geometry of each abnormal area to be judged, if it is determined that the abnormal area to be judged is not completely covered by the effective contact surface after elastic deformation compensation, then the abnormal area to be judged is marked as a functional defect area and the detection result is output.

[0094] For example, if the entire geometric contour of a certain abnormal area to be judged is within the coverage of the effective contact surface geometry, it indicates that the abnormal area has been completely compensated by the contact surface after elastic deformation of the sealing pair under working conditions, and does not constitute a defect affecting the sealing function, and is not marked; if any part of a certain abnormal area to be judged exceeds the coverage of the effective contact surface geometry, or although it is within the coverage of the effective contact surface geometry, the depth parameter of the abnormal area exceeds the upper limit of the deformation that the effective contact surface can compensate for, i.e., the gap judgment threshold, it is determined that the elastic deformation compensation is insufficient to completely cover the abnormal area, and it is marked as a functional defect area, and the detection result is output. The detection result includes the location coordinates, geometric contour, depth parameter and relative relationship with the boundary of the effective contact surface of the functional defect area.

[0095] Example 2: Based on the same inventive concept, such as Figure 2 As shown, this embodiment also provides a valve sealing surface defect detection system, the system comprising:

[0096] The sealing surface image acquisition and data processing module is used to acquire images of the sealing surface of the valve under inspection to obtain three-dimensional surface morphology data of the sealing surface; and to process the three-dimensional surface morphology data to extract the position coordinates, geometric contours and depth parameters of each abnormal morphology area on the sealing surface.

[0097] The abnormal area screening module is used to determine the theoretical sealing contact area of ​​the sealing surface in the closed state of the valve based on the structural type and geometric model of the valve to be inspected; the position coordinates of each abnormal area are spatially mapped to the theoretical sealing contact area, and the abnormal areas located within the theoretical sealing contact area are screened out as abnormal areas to be judged.

[0098] The effective contact surface geometry calculation module is used to obtain the sealing pair material parameters and operating condition parameters of the valve under test, and calculate the effective contact surface geometry after the sealing surface undergoes elastic deformation under working conditions based on the sealing pair material parameters and operating condition parameters.

[0099] The functional defect area judgment and result output module is used to determine, based on the depth parameters and effective contact surface geometry of each abnormal area to be judged, if the abnormal area to be judged is not completely covered by the effective contact surface after elastic deformation compensation, then mark the abnormal area to be judged as a functional defect area and output the detection result.

[0100] It should be noted that the specific methods by which each module performs operations in the system described in the above embodiments have been described in detail in the embodiments related to the method, and will not be elaborated here.

[0101] Finally, it should be noted that although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method of detecting defects in a valve sealing surface, characterized by, The method includes: Image acquisition is performed on the sealing surface of the valve under inspection to obtain three-dimensional surface morphology data of the sealing surface; the three-dimensional surface morphology data is processed to extract the position coordinates, geometric contours and depth parameters of each abnormal morphology area on the sealing surface; Based on the structural type and geometric model of the valve to be inspected, the theoretical sealing contact area of ​​the sealing surface in the valve closed state is determined; the position coordinates of each abnormal morphology area are spatially mapped to the theoretical sealing contact area, and the abnormal morphology areas located within the theoretical sealing contact area are selected as abnormal areas to be judged. Obtain the sealing pair material parameters and operating condition parameters of the valve to be inspected, and calculate the effective contact surface geometry after the sealing surface undergoes elastic deformation under working conditions based on the sealing pair material parameters and operating condition parameters; Based on the depth parameters and effective contact surface geometry of each anomaly region to be judged, if it is determined that the anomaly region to be judged is not completely covered by the effective contact surface after elastic deformation compensation, then the anomaly region to be judged is marked as a functional defect region and the detection result is output.

2. The method of claim 1, wherein The method for calculating the effective contact surface geometry of the sealing surface after elastic deformation under working conditions based on the sealing pair material parameters and operating condition parameters includes: The three-dimensional geometry of the sealing surface is reconstructed based on the three-dimensional surface topography data, and a finite element model of the sealing pair is constructed by combining the three-dimensional geometry of the mating sealing pairs. The elastic modulus and hardness of the sealing pair material parameters are used as input parameters for the constitutive relations of the materials of the sealing surface and the mating sealing pairs in the finite element model of the sealing pair contact. The valve closing load in the operating condition parameters is applied to the finite element model of the sealing pair contact as a boundary condition. The operating temperature in the operating condition parameters is applied to the finite element model of the sealing pair contact as a temperature field load. The thermal deformation of the sealing surface and the mating sealing pairs at the operating temperature is calculated by using the coefficient of thermal expansion. In the finite element model of the sealing pair contact, the thermal deformation is superimposed with the mechanical deformation caused by the valve closing load to obtain the deformation displacement distribution of the sealing surface under working conditions. Based on the deformation displacement distribution, the three-dimensional geometry of the sealing surface is corrected, and the area enclosed by the set of nodes where the gap between the corrected sealing surface and the mating sealing pair is lower than the gap judgment threshold is extracted as the effective contact surface geometry.

3. The method of claim 2, wherein The method for reconstructing the three-dimensional geometry of the sealing surface based on three-dimensional surface topography data, and constructing a finite element model of the sealing pair contact based on the three-dimensional geometry of the mating sealing pair of the valve under test, includes: Point cloud filtering is performed on the three-dimensional surface topography data to obtain effective point cloud data that characterizes the true geometric shape of the sealing surface; the effective point cloud data is then fitted using a surface reconstruction algorithm to generate a parametric surface model of the sealing surface. Using the parametric curved surface model of the sealing surface as the geometric boundary, the sealing surface region is meshed to obtain a finite element mesh model of one side of the sealing surface; The three-dimensional geometry of the mating sealing pair is meshed to obtain a finite element mesh model of one side of the mating sealing pair. The finite element mesh model of the sealing surface side and the finite element mesh model of the mating sealing pair side are spatially aligned according to their assembly position relationship when the valve is closed. A contact pair relationship is established between the surface nodes of the two sides that are in contact with each other and the friction coefficient is set to construct the finite element model of the sealing pair contact.

4. The method of claim 3, wherein The method for generating a parametric surface model of the sealing surface by fitting effective point cloud data using a surface reconstruction algorithm includes: Using each sampling point in the effective point cloud data as the center, search for the nearest neighboring points in the search space to form a local neighborhood point set; obtain the initial normal vector field of all sampling points through principal component analysis of the local neighborhood point set of each sampling point; Taking the orientation of the normal vector at the outer contour boundary of the effective point cloud data as the propagation starting point, the orientation of the normal vector of each sampling point is corrected point by point according to the propagation criterion of minimizing the angle between the normal vectors of neighboring points, so that the initial normal vector field of all sampling points points uniformly points to the same side of the sealing surface, thus obtaining a uniformly oriented normal vector field; using the uniformly oriented normal vector field as a constraint, the effective point cloud data is transformed into an isosurface expressed by an implicit function, and the mesh representation at the zero isosurface is extracted to obtain the initial reconstructed surface; The initial reconstructed surface is parametrically mapped according to the sealing surface structure type. The three-dimensional spatial coordinates of each grid vertex are converted into the corresponding two-dimensional parametric coordinates in the parameter domain. The two-dimensional parametric coordinates of each grid vertex are used as independent variables and the corresponding three-dimensional spatial coordinates are used as dependent variables. The mapping function from the parameter domain to the three-dimensional space is established by least squares fitting, and the parametric surface model of the sealing surface is obtained.

5. The method of claim 3, wherein The method of obtaining a finite element mesh model of one side of the sealing surface by meshing the sealing surface region using a parametric curved surface model of the sealing surface as the geometric boundary includes: The curvature values ​​at various locations on the parametric surface model of the sealing surface are calculated to obtain the global curvature distribution. The target local mesh size is assigned to each location according to the monotonically decreasing mapping relationship between the curvature value and the target mesh size, thus obtaining the target mesh size distribution. Using the outer contour boundary of the parametric surface model of the sealing surface as the constraint boundary, an initial planar triangular mesh is generated in the parameter domain of the parametric surface model of the sealing surface based on the target mesh size distribution. The parameter coordinates of each vertex of the initial planar triangular mesh are mapped back to the three-dimensional spatial coordinates of the parametric surface model of the sealing surface to obtain the surface mesh. The surface mesh is inspected for quality. Mesh elements with aspect ratio or distortion exceeding the preset quality threshold are identified as substandard elements. The node positions of substandard elements are subjected to Laplace smoothing iteration along the tangent plane of the parametric surface model of the sealing surface until the quality index of all mesh elements meets the preset quality threshold. The surface mesh is then stretched along the normal direction of the sealing surface and divided into several layers of solid elements in the thickness direction to obtain the finite element mesh model of one side of the sealing surface.

6. The method of claim 2, wherein The method of correcting the three-dimensional geometry of the sealing surface based on the deformation displacement distribution and extracting the region enclosed by the set of nodes where the gap between the corrected sealing surface and the mating sealing pair is lower than the gap determination threshold as the effective contact surface geometry includes: The displacement vectors of each node on the sealing surface in the deformation displacement distribution are superimposed one by one onto the initial coordinates of the corresponding node in the three-dimensional geometry of the sealing surface to obtain the deformed coordinates of each node on the sealing surface under working conditions. The modified three-dimensional geometry of the sealing surface under working conditions is reconstructed from the deformed coordinates. Based on the coordinates of each node in the modified three-dimensional geometry of the sealing surface, the normal clearance value between the node and the mating sealing surface is calculated along the normal vector direction of each node to obtain the normal clearance distribution map of the entire sealing surface. The normal gap distribution map is subjected to threshold segmentation processing. Nodes with normal gap values ​​lower than the gap determination threshold are marked as contact nodes, and nodes with normal gap values ​​higher than the gap determination threshold are marked as non-contact nodes. The region enclosed by the outer contour of the set of interconnected contact nodes in space is extracted as a candidate effective contact surface. The node contact pressure distribution of each candidate effective contact surface is verified, and the candidate effective contact surfaces that pass the verification are merged and output as the effective contact surface geometry.

7. The method of claim 6, wherein The method for determining the gap determination threshold includes: The compression deformation characteristic parameters of the soft sealing material in the mating sealing pair are extracted from the sealing pair material parameters. The compression deformation characteristic parameters include the correspondence between the compressive stress and compressive strain of the soft sealing material under the corresponding contact pressure of the operating condition parameters. The nominal contact pressure at the sealing surface is calculated based on the valve closing load and the theoretical sealing contact area of ​​the sealing surface in the operating condition parameters. The nominal contact pressure is substituted into the correspondence between the compressive stress and compressive strain to obtain the compressive strain value of the soft sealing material under the nominal contact pressure. The amount of compression deformation of the soft sealing material under the nominal contact pressure is calculated based on the compressive strain value and the initial thickness of the soft sealing material in the thickness direction. The amount of compression deformation is determined as the gap judgment threshold.

8. The method of claim 1, wherein The method for determining the theoretical sealing contact area of ​​the sealing surface in the closed state of the valve based on the structural type and geometric model of the valve to be tested includes: Obtain the structural type identifier of the valve to be inspected, and retrieve the standard geometric model corresponding to the structural type of the valve to be inspected from the pre-stored valve geometric model library based on the structural type identifier; Based on the sealing contact form corresponding to the structural type of the valve under test, the initial position of the theoretical contact line between the sealing surface and the mating sealing pair is extracted. The initial theoretical sealing contact area is obtained by expanding the preset contact width margin outward from the initial position of the theoretical contact line. The projection of the geometric interference region in the valve closed state is calculated based on the nominal geometry of the sealing surface and the mating sealing pair in the standard geometric model. The intersection of the projection of the geometric interference region with the initial theoretical sealing contact area is taken to obtain the area range in which the sealing surface and the mating sealing pair actually make geometric contact in the valve closed state, and this area is recorded as the theoretical sealing contact area.

9. The method for detecting defects on a valve sealing surface according to claim 8, characterized in that, The method for calculating the projection of the geometric interference region in the valve closed state based on the nominal geometric shapes of the sealing surface and the mating sealing pair in the standard geometric model includes: The nominal geometry of the sealing surface and the nominal geometry of the mating sealing pair in the standard geometric model are spatially aligned according to their relative assembly positions in the valve closed state to obtain the initial assembly position of the sealing surface and the mating sealing pair. Based on the initial assembly position, the valve closing stroke displacement is applied along the direction in which the sealing surface and the mating sealing pair approach each other. The normal distance between each sampling point on the nominal geometry of the sealing surface and the nominal geometry surface of the mating sealing pair is calculated one by one to obtain the normal distance distribution of the entire sealing surface. Sampling points with normal distance values ​​less than zero in the normal distance distribution are marked as interference points to obtain the set of interference points; spatially connected interference points are merged into the same interference region, and the projection range of each interference region on the nominal geometry of the sealing surface is obtained by using the outer contour of each interference region as the boundary; the projection range of all interference regions is merged to obtain the projection of the geometric interference region.

10. A valve sealing surface defect detection system, characterized in that, The system includes: The sealing surface image acquisition and data processing module is used to acquire images of the sealing surface of the valve under inspection to obtain three-dimensional surface morphology data of the sealing surface; and to process the three-dimensional surface morphology data to extract the position coordinates, geometric contours and depth parameters of each abnormal morphology area on the sealing surface. The abnormal area screening module is used to determine the theoretical sealing contact area of ​​the sealing surface in the closed state of the valve based on the structural type and geometric model of the valve to be inspected; the position coordinates of each abnormal area are spatially mapped to the theoretical sealing contact area, and the abnormal areas located within the theoretical sealing contact area are screened out as abnormal areas to be judged. The effective contact surface geometry calculation module is used to obtain the sealing pair material parameters and operating condition parameters of the valve under test, and calculate the effective contact surface geometry after the sealing surface undergoes elastic deformation under working conditions based on the sealing pair material parameters and operating condition parameters. The functional defect area judgment and result output module is used to determine, based on the depth parameters and effective contact surface geometry of each abnormal area to be judged, if the abnormal area to be judged is not completely covered by the effective contact surface after elastic deformation compensation, then mark the abnormal area to be judged as a functional defect area and output the detection result.

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