Tire pavement contact three-dimensional stress test system and method

Abstract

The invention belongs to the field of tire-road three-dimensional stress testing, and discloses a tire-road contact three-dimensional stress testing system and method, which are characterized in that a plurality of functional modules such as a test piece manufacturing module, a contact testing module, a three-dimensional finite element modeling module, a three-dimensional point cloud generation module, a precision correction module and a three-dimensional stress calculation module are integrated; the accurate measurement of the three-dimensional stress in the contact process of the tire and the road surface is realized; the accuracy and the reliability of a test result are obviously improved; the test piece manufacturing unit ensures authenticity and repeatability of a pavement test piece, the contact test platform simulates a real contact environment, the three-dimensional finite element model generation platform provides an accurate model basis for mechanical analysis, and the three-dimensional point cloud generation platform realizes accurate acquisition of deformation data. The precision correction unit improves the simulation precision by iteratively optimizing the friction coefficient, and finally the three-dimensional stress calculation unit outputs a three-dimensional stress distribution result, so that a scientific basis is provided for tire design, pavement maintenance and vehicle safety performance evaluation.

Description

Technical Field

[0001] The invention belongs to the field of tire-road three-dimensional stress testing, and in particular relates to a tire-road contact three-dimensional stress testing system and method. Background Art

[0002] Tire-road three-dimensional stress refers to the stress distribution in all directions in the contact area between the tire and the road, including: vertical stress (normal stress) and tangential stress. Vertical stress will directly affect the contact area and friction; tangential stress includes longitudinal and transverse shear stress, which respectively lead to different friction behaviors, such as sliding friction and rolling friction. In addition to playing a decisive role in friction, which is closely related to traffic safety, tire-road three-dimensional stress is also the basis for revealing the formation mechanism of tire-road noise and wear microparticles. With the development of surface morphology testing technology, the influence of the subtle roughness of the road surface on contact has gradually received attention, and the study of high-precision stress distribution on a smaller scale is more in line with current usage needs.

[0003] At present, test methods such as pressure films, pressure blankets, and three-way sensor arrays can be used to test the contact stress between tires and roads. However, these methods require placing materials with high deformation resistance, such as film paper and sensors, between the tire and the road. This intervention process inevitably changes the natural state of the contact interface, resulting in a deviation between the stress data obtained from the test and the high-precision three-dimensional true stress when the tire actually acts on the road, making it difficult to fully reflect the true contact mechanical properties. In addition, numerical simulation methods, as another contact stress test method, can avoid the influence of excess media between the tire and the road, but the real contact on the rough road surface is difficult to verify, making the reliability of the simulation results questionable.

[0004] It can be seen that the existing tire-road three-dimensional stress testing methods usually use medium intervention testing and numerical simulation methods, which have certain limitations and cannot guarantee the accuracy and reliability of the test results in practical applications. Summary of the invention

[0005] The present invention provides a tire-road contact three-dimensional stress testing system and method to solve the technical problem that the existing tire-road three-dimensional stress testing methods usually adopt medium intervention testing and numerical simulation methods, which have certain limitations and cannot guarantee the accuracy and reliability of the test results in actual applications.

[0006] In order to achieve the above object, the present invention adopts the following technical contents: A tire-road contact three-dimensional stress testing system, comprising: A test specimen making unit, used for making a road test specimen according to the three-dimensional topography point cloud data of the road surface; A contact test platform is used to simulate the contact environment between the tire and the road test piece and to collect the rubber deformation image of the tire during the contact process between the tire and the road test piece; A three-dimensional finite element model generation platform, used to generate a three-dimensional finite element model of a tire based on a tire profile geometry model after assigning material properties, and to generate a three-dimensional finite element model of a road surface based on model parameters assigned to road surface materials; A 3D point cloud generation platform, used to generate a 3D point cloud of measured tread deformation based on the tire's rubber deformation image, and to obtain a 3D point cloud of simulated tread deformation based on the tire's 3D finite element model and the road's 3D finite element model; The precision correction unit is used to update and iterate the initial value of the friction coefficient between the tire and the road test piece according to the comparison result of the measured tread deformation three-dimensional point cloud and the simulated tread deformation three-dimensional point cloud until the preset conditions are met, so as to output the final initial value of the friction coefficient; The three-dimensional stress calculation unit is used to calculate the three-dimensional stress result between the tire and the road surface according to the three-dimensional finite element model of the tire, the three-dimensional finite element model of the road surface and the initial value of the final friction coefficient.

[0007] Furthermore, the road surface three-dimensional topography point cloud data is collected from the road surface area to be evaluated by a contact or non-contact three-dimensional topography scanning device; the road surface test piece is made of transparent material and 3D printing technology to replicate a road surface with real roughness.

[0008] Furthermore, the contact test platform includes a light source, a binocular camera, a speckle image layer and a transparent plate arranged in sequence from bottom to top, and a loading device for providing a pattern load; during the simulated contact process, the tire and the road test piece are placed on the transparent plate.

[0009] A tire-road contact three-dimensional stress testing method, comprising: Prepare road test specimens based on the road surface three-dimensional topography point cloud data; Simulating the contact environment between the tire and the road test piece, and collecting the rubber deformation image of the tire during the contact process between the tire and the road test piece; Generate a three-dimensional finite element model of the tire according to the tire cross-section geometric model after assigning material properties, and generate a three-dimensional finite element model of the road surface according to the model parameters assigned to the road surface material; Generating a three-dimensional point cloud of measured tread deformation according to the rubber deformation image of the tire, and obtaining a three-dimensional point cloud of simulated tread deformation according to the three-dimensional finite element model of the tire and the three-dimensional finite element model of the road surface; According to the comparison result of the measured tread deformation three-dimensional point cloud and the simulated tread deformation three-dimensional point cloud, the initial value of the friction coefficient between the tire and the road test piece is updated and iterated until the preset conditions are met, so as to output the final initial value of the friction coefficient; The three-dimensional stress result between the tire and the road is calculated based on the three-dimensional finite element model of the tire, the three-dimensional finite element model of the road, and the initial value of the final friction coefficient.

[0010] Furthermore, a contact or non-contact three-dimensional topography scanning device is used to collect the road surface area to be evaluated to obtain three-dimensional topography point cloud data of the road surface; the three-dimensional topography point cloud data of the road surface is leveled, abnormal points are removed, non-test points are repaired, and filtering pre-processed, and 3D printing technology is used to replicate a road surface with real roughness according to the pre-processed three-dimensional topography point cloud data of the road surface, and a road test specimen is obtained by combining transparent materials; the modulus of the transparent material after curing is ≥3000 MPa; the resolution of 3D printing is ≥0.5 mm.

[0011] Furthermore, in the process of simulating the contact between the tire and the road test piece, the baseline distance of the binocular camera is controlled at 50-100 mm and the visual axis is kept parallel.

[0012] Furthermore, the specific steps of generating a tire three-dimensional finite element model according to the tire cross-section geometric model after assigning material properties are as follows: The tire profile geometry model is established in AutoCAD based on the collected geometry data of each tire structure layer, material type information and tread pattern; at the same time, the constitutive parameters of each tire structure layer material are tested through mechanical experiments; Import the tire section geometry model into HyperMesh software and mesh each tire structure layer; Import the meshed tire section geometry model into ABAQUS software, and assign material properties to each structural layer based on the constitutive parameters of the tested tire structural layer materials; Generate a three-dimensional finite element model of the tire using the tire cross-section geometry model after assigning material properties; The specific steps for generating a three-dimensional finite element model of a pavement according to the model parameters assigned to the pavement material are as follows: Import the 3D road surface model into the HyperMesh software to divide the mesh; The gridded 3D pavement topography model is imported into ABAQUS software, the model parameters of the pavement material are assigned, and the 3D finite element model of the pavement is generated.

[0013] Furthermore, the specific steps of generating the measured tread deformation three-dimensional point cloud according to the tire rubber deformation image are as follows: The rubber deformation image is corrected according to the calibration results of the camera parameters, and image registration is performed based on the feature points in the rubber deformation image to ensure that the left and right images are aligned; For the corrected and aligned rubber deformation images, the disparity map is calculated using the stereo matching algorithm of OpenCV; Calculate the depth map based on the disparity map, camera focal length and baseline distance, and use the depth map to generate and save the measured tread deformation three-dimensional point cloud; The specific steps of obtaining the simulated tread deformation 3D point cloud based on the tire 3D finite element model and the road 3D finite element model are as follows: The parameters of the tire 3D finite element model and the road 3D finite element model are set, and the mixed penalty function and Lagrange multiplier method are used to solve the 3D deformation during tire-road contact to obtain the 3D point cloud of simulated tread deformation.

[0014] Furthermore, the steps for obtaining the comparison result between the measured tread deformation three-dimensional point cloud and the simulated tread deformation three-dimensional point cloud are as follows: Loading the measured tread deformation 3D point cloud and the simulated tread deformation 3D point cloud; The measured tread deformation 3D point cloud is used as the target point cloud, and the simulated tread deformation 3D point cloud is used as the source point cloud, and feature point matching is performed, and the root mean square error between the measured tread deformation 3D point cloud and the simulated tread deformation 3D point cloud is calculated; Compare the RMS error with the preset threshold and output the comparison result.

[0015] Furthermore, if the comparison result shows that the root mean square error is greater than the preset threshold, the initial value of the friction coefficient between the tire and the road test piece is iteratively updated using the binary method until the root mean square error is within the preset threshold; the final initial value of the friction coefficient is substituted into the tire three-dimensional finite element model and the road three-dimensional finite element model to calculate the normal stress and the transverse and longitudinal tangential stresses; Otherwise, the current initial value of the friction coefficient is substituted into the three-dimensional finite element model of the tire and the three-dimensional finite element model of the road surface to calculate the normal stress and the transverse and longitudinal tangential stresses.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a tire-road contact three-dimensional stress test system, which realizes accurate measurement of three-dimensional stress during tire-road contact by integrating multiple functional modules such as specimen production, contact test, three-dimensional finite element modeling, three-dimensional point cloud generation, precision correction and three-dimensional stress calculation. The use of this system not only improves the automation and intelligence level of the test, but also significantly improves the accuracy and reliability of the test results; the specimen production unit ensures the authenticity and repeatability of the road test specimen, the contact test platform simulates the real contact environment, the three-dimensional finite element model generation platform provides an accurate model basis for mechanical analysis, the three-dimensional point cloud generation platform realizes the accurate acquisition of deformation data, the precision correction unit improves the simulation accuracy by iteratively optimizing the friction coefficient, and the final three-dimensional stress calculation unit outputs the three-dimensional stress distribution result, which provides a scientific basis for tire design, road maintenance and vehicle safety performance evaluation.

[0017] Preferably, in the present invention, a contact or non-contact three-dimensional topography scanning device is used to obtain the three-dimensional topography point cloud data of the road surface, ensuring the comprehensiveness and high accuracy of the data. The road test specimen is made by combining 3D printing technology with transparent materials, and the road surface with real roughness is successfully replicated, which not only retains the microscopic characteristics of the road surface, but also facilitates subsequent non-contact measurement; this not only improves the preparation efficiency of the specimen, but also ensures a high degree of consistency between the specimen and the real road surface, providing a reliable basis for subsequent mechanical testing.

[0018] Preferably, in the present invention, the contact test platform constructs a test system capable of simulating the contact environment between the tire and the road test piece by rationally arranging components such as the light source, binocular camera, speckle image layer, transparent plate and loading device; the light source provides sufficient lighting conditions to ensure the clarity of image acquisition; the high resolution and high frame rate of the binocular camera ensure the real-time and accuracy of the deformation data; the speckle image layer, as a deformation mark, enhances the deformation recognition and tracking effect of the tire and improves the accuracy of deformation measurement; the transparent plate isolates the camera from the test piece to avoid the influence of camera lens contamination on the measurement results; the loading device provides a controllable pattern load to simulate the stress of the tire during actual driving. The entire platform is reasonably designed and fully functional, providing strong support for subsequent deformation data acquisition and mechanical analysis.

[0019] The present invention also provides a tire-road contact three-dimensional stress test method, which forms a complete test process from specimen preparation, contact environment simulation, deformation data collection, three-dimensional finite element modeling to stress calculation; the method not only realizes the accurate measurement of the three-dimensional stress during the tire-road contact process, but also improves the simulation accuracy by iteratively optimizing the friction coefficient, ensuring the accuracy and reliability of the test results. The method also has the advantages of simple operation, high degree of automation, and short test cycle, and provides an efficient and accurate test means for tire design, road maintenance, and vehicle safety performance evaluation.

[0020] Preferably, in the present invention, the accuracy and reliability of the data are ensured by pre-processing operations such as leveling, removing abnormal points, repairing non-test points and filtering the road surface three-dimensional topography point cloud data. When using 3D printing technology combined with transparent materials to make road test specimens, the modulus and printing resolution of the material are strictly controlled to ensure the authenticity and durability of the specimens; through refined data processing and specimen production processes, high-quality basic data and reliable test objects are provided for subsequent mechanical tests.

[0021] Preferably, in the present invention, the baseline distance of the binocular camera is controlled between 50-100 mm and the visual axes are kept parallel. This layout requirement ensures that the binocular camera can capture sufficient overlapping areas, thereby improving the accuracy and stability of image registration. At the same time, it also avoids measurement errors and data distortion problems caused by improper camera position. This refined camera layout design provides a strong guarantee for subsequent deformation data acquisition and three-dimensional point cloud generation.

[0022] Preferably, in the present invention, by collecting geometric data, material type information, tread pattern and other information of each structural layer of the tire, a tire profile geometric model is established in AutoCAD, and the constitutive parameters of the materials of each structural layer are tested through mechanical experiments, thereby providing an accurate model basis for subsequent finite element modeling; after meshing in HyperMesh software, the model is imported into ABAQUS software and assigned material properties, and finally a three-dimensional finite element model of the tire is generated; in this way, the accuracy and reliability of the model are ensured, providing strong support for subsequent mechanical analysis and stress calculation.

[0023] Preferably, in the present invention, after the rubber deformation image is corrected and registered according to the calibration results of the camera parameters, the disparity map is calculated using the stereo matching algorithm of OpenCV, and the measured tread deformation three-dimensional point cloud is generated accordingly; at the same time, a simulation solution is performed based on the three-dimensional finite element model of the tire and the road surface to obtain a simulated tread deformation three-dimensional point cloud; these two point cloud generation methods complement and verify each other, thereby improving the comprehensiveness and accuracy of the deformation data; by comparing the measured and simulated point cloud data, the accuracy of the simulation results can be evaluated and parameters such as the friction coefficient can be optimized, thereby further improving the accuracy and reliability of the test.

[0024] Preferably, in the present invention, by loading the measured and simulated tread deformation three-dimensional point cloud data and performing feature point matching and root mean square error calculation, the similarity and difference between the two point cloud data can be intuitively evaluated. This method of obtaining the comparison results provides an important reference for subsequent precision correction and parameter optimization; at the same time, by comparing the root mean square error with the preset threshold and outputting the comparison results, the accuracy and reliability of the simulation results can be easily judged, providing strong support for subsequent mechanical analysis and stress calculation.

[0025] Preferably, in the present invention, when the root mean square error between the measured tread deformation three-dimensional point cloud and the simulated tread deformation three-dimensional point cloud is greater than a preset threshold, the binary search method is used to iteratively update the initial value of the friction coefficient between the tire and the road test piece until the preset conditions are met. The above-mentioned iterative optimization method can gradually approach the actual friction coefficient value and reduce the simulation error, thereby improving the accuracy and reliability of the test; finally, the optimized friction coefficient is substituted into the three-dimensional finite element model of the tire and road surface to perform stress calculation to obtain results such as normal stress and transverse and longitudinal tangential stresses. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram of the structure of a contact test platform of a tire-road contact three-dimensional stress test system provided by the present invention; Figure 2 A cross-sectional view of a tire provided by an embodiment of the present invention; Figure 3 A tire cross-section mesh division diagram provided by an embodiment of the present invention; Figure 4 A road surface grid division diagram provided by an embodiment of the present invention; wherein (a) is a three-dimensional model diagram of the road surface; (b) is a partial enlarged diagram of (a); Figure 5 A schematic diagram of a tire-road contact situation of a numerical simulation provided by an embodiment of the present invention; Figure 6 The stress cloud diagram of the tire in contact with the road surface provided in the embodiment of the present invention; wherein (a) is the normal stress cloud diagram in the X-axis direction; (b) is the normal stress cloud diagram in the Y-axis direction; (c) is the normal stress cloud diagram in the Z-axis direction; Figure 7 A structural block diagram of a tire-road contact three-dimensional stress testing system provided by the present invention.

[0027] Reference numerals: 1. Tire; 2. Road test piece; 3. Speckle image layer; 4. Transparent plate; 5. Binocular camera; 6. Equipment box; 7. Light source. DETAILED DESCRIPTION

[0028] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail in the following specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0029] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0030] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0032] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0033] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0034] In the description of the embodiments of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0035] Example 1 As mentioned in the background technology, the existing tire-road three-dimensional stress test methods usually adopt medium intervention testing and numerical simulation methods, which have certain limitations, mainly reflected in: First, the test methods such as pressure film, pressure blanket, three-way sensor array, etc. can be used to test the contact stress between the tire and the road. However, these methods require placing materials with high deformation resistance such as film paper, sensors, etc. between the tire and the road. This intervention process inevitably changes the natural state of the contact interface, resulting in a deviation between the stress data obtained from the test and the high-precision three-dimensional real stress when the tire actually acts on the road, making it difficult to fully reflect the real contact mechanical properties; Second, as another contact stress test method, the numerical simulation method can avoid the influence of excess media between the tire and the road, but the real contact on the rough road surface is difficult to verify, making the reliability of the simulation results questionable.

[0036] In order to solve the above problems, the present invention provides a tire-road contact three-dimensional stress testing system and method. The system and method can avoid the influence of excess medium between the tire and the road, ensure the accuracy and reliability of the simulation results, and test the high-precision tire-road contact three-dimensional stress.

[0037] The present invention is further described in detail below with reference to the accompanying drawings and embodiments: like Figure 7 As shown, this embodiment provides a tire-road contact three-dimensional stress test system, which includes a specimen production unit, a contact test platform, a three-dimensional finite element model generation platform, a three-dimensional point cloud generation platform, a precision correction unit and a three-dimensional stress calculation unit. The specific functions and structures are as follows: Specimen production module: Based on the three-dimensional topographic data of the road surface (obtained through high-precision scanning equipment), a road specimen 2 with real road roughness is produced using transparent materials and 3D printing technology.

[0038] Contact test platform: simulates the contact environment between a real tire 1 and a road test piece 2. The contact test platform is provided with a light source 7, a binocular camera 5, a speckle image layer 3, a transparent plate 4, and a device for applying a standard load; the tire 1 and the road test piece 2 are placed on the transparent plate 4, and the binocular camera 5 captures the rubber deformation image of the tire 1 during the contact process.

[0039] Three-dimensional finite element modeling platform: First, a three-dimensional finite element model of the tire 1 is established according to its geometric structure and material properties; at the same time, a three-dimensional finite element model of the road surface is generated according to the characteristics of the road surface material.

[0040] 3D point cloud generation platform: Based on the rubber deformation image taken by the binocular camera 5, the measured tread deformation 3D point cloud is generated through image processing and 3D reconstruction technology; in addition, the simulated tread deformation 3D point cloud is obtained through finite element method analysis.

[0041] Precision correction unit: Compares the measured tread deformation 3D point cloud with the simulated tread deformation 3D point cloud, and continuously optimizes the friction coefficient between the tire and the road until the preset accuracy requirements are met, and finally determines the most accurate friction coefficient value.

[0042] Three-dimensional stress calculation unit: Calculates the three-dimensional stress distribution when the tire contacts the road using the final determined friction coefficient, the three-dimensional finite element model of the tire and the three-dimensional finite element model of the road.

[0043] This embodiment also provides a tire-road contact three-dimensional stress testing method, which specifically includes the following steps: Step 1: Specimen preparation: Use 3D scanning equipment to obtain road surface topography data, and after processing, use 3D printing technology to produce road test specimens.

[0044] Step 2: Contact test: simulate the contact between the tire and the road on the contact test platform, and capture the rubber deformation image of the tire through a binocular camera.

[0045] Step 3: Modeling and simulation: According to the material properties of the tire and the road, their three-dimensional finite element models are established respectively. At the same time, the measured tread deformation three-dimensional point cloud is generated according to the camera image, and the simulated point cloud is obtained through finite element simulation.

[0046] Step 4: Accuracy verification: By comparing the measured and simulated point cloud data, the friction coefficient is continuously adjusted until the difference between the two is within an acceptable range.

[0047] Step 5: Stress calculation: Use the corrected friction coefficient and finite element model to calculate the three-dimensional stress when the tire contacts the road, including normal stress and transverse and longitudinal tangential stress.

[0048] In this embodiment, a high modulus transparent material is selected to ensure the strength and authenticity of the specimen, and the 3D printing resolution reaches or exceeds 0.5 mm to accurately replicate the roughness of the road surface.

[0049] In this embodiment, the baseline distance and the visual axis parallelism of the binocular camera are strictly controlled to improve the accuracy of image registration and three-dimensional reconstruction.

[0050] In this embodiment, advanced image registration and stereo matching algorithms are used to ensure that the generated point cloud data is accurate and reliable.

[0051] In this embodiment, the three-dimensional stress distribution when the tire contacts the road surface is comprehensively calculated by using advanced finite element analysis technology in combination with the precise correction of the friction coefficient.

[0052] The three-dimensional tire-road contact stress test and method provided in this embodiment can evaluate the mechanical properties of the tire in contact with the road with high accuracy and reliability, providing a scientific basis for tire design, road maintenance and vehicle safety performance evaluation.

[0053] Example 2 This embodiment also provides another tire-road contact three-dimensional stress testing method, which specifically includes: Step 1: Obtain high-precision three-dimensional road surface morphology.

[0054] The specific steps include: determining the road surface area to be evaluated; using contact or non-contact three-dimensional topography scanning equipment to obtain three-dimensional topography point cloud data of the road surface, with a resolution of no less than 0.2 mm; performing pre-processing operations such as leveling, removing abnormal points, repairing non-test points, and filtering on the road surface point cloud data.

[0055] Step 2: Use transparent materials and 3D printing technology to replicate a road surface with real roughness to obtain a road test piece 2.

[0056] The specific steps include: establishing a three-dimensional model of the road surface based on the three-dimensional morphological point cloud data obtained in step one; inputting the three-dimensional model of the road surface into a 3D printer to replicate a road test piece with the same surface morphology as the actual road surface, selecting a resolution of not less than 0.5 mm when printing, and selecting a highly transparent material, such as a photocurable resin, and the modulus of the material after curing should be not less than 3000 MPa.

[0057] Step 3: Figure 1 As shown, a contact test platform for the tire-road contact area is built.

[0058] In this embodiment, the contact test platform specifically includes: A light source 7 for providing sufficient lighting during the shooting process, preferably a fill light; A bilaterally symmetrically arranged binocular camera 5 for capturing deformation of the tread rubber in the contact area, wherein the resolution of the binocular camera 5 is not less than 1280*960 and the frame rate is not less than 100FPS; A computer for controlling the binocular camera 5 and receiving data transmitted by the binocular camera 5; A speckle image layer 3 with irregularly distributed spots is sprayed on the surface; A transparent plate 4 for separating the camera from the test piece, preferably a glass cover plate; A transparent road test piece 2 and a tire 1; and a loading device for providing the specified pattern loads.

[0059] The equipment box 6 is used to carry and fix the binocular camera 5 .

[0060] Step 4: Use binocular vision technology to obtain an image pair of the contact area, mainly including correctly connecting the binocular camera 5 to the computer; adjusting and fixing the positions of the two cameras so that the baseline distance of the binocular camera 5 is 50-100mm to ensure that the images captured by the two cameras have an overlap area of ​​more than 60-70%, and the visual axes are parallel; using the camera to capture multiple images containing high-resolution chessboards, and calibrating the camera's internal parameters (focal length, principal point coordinates, distortion coefficient) and external parameters (rotation matrix, translation vector) with the help of OpenCV; placing the 3D printed road test piece on a transparent plate, turning on the fill light, using a loading device to provide a load under the conditions of specified load, loading speed, and slip rate, and at the same time, allowing the two cameras to synchronously capture the rubber deformation image of the tire during the loading process.

[0061] Step 5: Reconstruct the measured tire deformation in the three-dimensional contact area.

[0062] The specific steps include: correcting the images captured by the binocular camera according to the calibration results of the camera parameters, performing image registration based on the feature points in the rubber deformation image to ensure that the left and right images are aligned; using OpenCV's stereo matching algorithm to calculate the disparity map of the corrected and aligned images, calculating the depth map based on the disparity map and the camera focal length and baseline distance, and using the depth map to generate and save the measured tread deformation three-dimensional point cloud.

[0063] Step 6: Create a digital model of the tire and divide the three-dimensional road model into a three-dimensional finite element model.

[0064] The specific steps include: collecting the geometric data of each structural layer of the tire to be tested, the material type information and the tread pattern, and then establishing the tire profile geometric model in AutoCAD, such as Figure 2 As shown in the figure, the constitutive parameters of each structural layer material are tested through mechanical experiments; Figure 3 As shown, the tire section geometry model is imported into the HyperMesh software, and meshes are divided into different structural layers; the meshed tire section geometry model is imported into the ABAQUS software, and material properties of each structural layer are assigned based on the constitutive parameters of the tested material of each structural layer; with the help of rotation and mirroring functions, a tire three-dimensional finite element model is generated from the tire section geometry model after material properties are assigned; like Figure 4 As shown, specifically Figure 4 As shown in (a), the 3D pavement model is imported into the HyperMesh software to divide the mesh, and then imported into the ABAQUS software to assign the model parameters of the pavement material to establish the 3D finite element model of the pavement. The local view is shown in Figure 4 (b) The road surface point cloud file is processed using MATLAB, nodes are written and meshed and written into the inp file, and the road surface is defined as a rigid body property.

[0065] Step 7. Based on the high-precision three-dimensional finite element model of the road surface and the three-dimensional finite element model of the tire, set the boundary between the two as the potential contact area, define the road surface with greater stiffness as the primary surface, and the tire tread as the secondary surface; refine the mesh of the contact surface, and try to match the meshes of the two on the contact surface; select the contact type, and use the Coulomb friction model to define the friction coefficient, and give an initial value of 0.5; set the load used for measuring the contact deformation in step 4, and use the mixed penalty function and Lagrange multiplier method to solve the three-dimensional deformation during tire-road contact, that is, obtain the simulated tread deformation three-dimensional point cloud.

[0066] Step 8: Compare the tire deformation obtained by actual measurement with that obtained by finite element method.

[0067] The specific steps include: using data processing software such as MATLAB to load two sets of tread deformation three-dimensional point clouds obtained by actual measurement and numerical simulation; using the measured tread deformation three-dimensional point cloud as the target point cloud, and the simulated tread deformation three-dimensional point cloud as the source point cloud; extracting feature points and local feature descriptors from the two sets of point clouds, using feature descriptors to match feature points, and using a robust estimation algorithm to estimate the initial transformation matrix based on the matched feature point pairs, and applying the transformation matrix to the source point cloud; updating the source point cloud, and calculating the root mean square error of the two sets of point clouds.

[0068] Step 9: Figure 5 As shown in , when the root mean square error of the two sets of point cloud data is greater than the preset threshold, the binary method is used to update the initial value of the friction coefficient preset in step seven, and the finite element method is used to calculate the numerical simulation deformation result of the tire tread on the rough road surface, and the root mean square error of the tread deformation point cloud data is within the preset threshold range as the iteration termination condition of the friction coefficient; Figure 6 As shown in the figure, the friction coefficient that reaches the termination condition is substituted into the ABAQUS road surface three-dimensional finite element model and the tire three-dimensional finite element model to obtain the normal stress and the transverse and longitudinal tangential stresses, as shown in the figure. Figure 6 As shown in (a), (b) and (c).

[0069] In summary, the present invention provides a tire-road contact three-dimensional stress testing system and method, which has the following advantages over existing testing measures: First, high precision and authenticity: Road surface data is obtained through high-precision three-dimensional scanning equipment, and 3D printing technology is used to produce road test specimens with real roughness, ensuring a high degree of restoration of the test environment and accuracy of the data.

[0070] Second, comprehensive stress analysis: The system not only focuses on the normal stress between the tire and the road, but also deeply analyzes the transverse and longitudinal tangential stresses, providing comprehensive three-dimensional stress distribution results, which helps to more accurately evaluate the interaction between the tire and the road.

[0071] Third, intelligent friction coefficient correction: By comparing the measured tread deformation 3D point cloud with the simulated point cloud, the friction coefficient is automatically updated and iterated until the preset conditions are met, greatly improving the accuracy and reliability of the test results.

[0072] Fourth, advanced image processing and 3D reconstruction technology: using binocular cameras and advanced image processing algorithms (such as OpenCV's stereo matching algorithm) to generate high-precision 3D point clouds of measured tread deformation, ensuring the accuracy and efficiency of data processing.

[0073] Fifth, integrated testing platform: The entire testing system integrates multiple functional modules such as specimen production, contact testing, 3D modeling, point cloud generation, precision correction and stress calculation, realizing full-chain automated processing from data acquisition to result output, thus improving testing efficiency.

[0074] Sixth, flexibility and scalability: The system supports testing of different tires and road materials. It can adapt to different testing requirements by modifying material properties and model parameters, and has high flexibility and scalability.

[0075] Seventh, scientificity and practicality: Based on the method combining finite element analysis and experimental verification, it provides scientific basis and practical tools for tire design, road maintenance and vehicle safety performance evaluation, and has high application value.

[0076] The above embodiment is only one of the implementation methods that can realize the technical solution of the present invention. The scope of protection claimed by the present invention is not limited only to this embodiment, but also includes changes, replacements and other implementation methods that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed by the present invention.

Claims

1. A tire-road contact three-dimensional stress testing system, characterized in that: include: A test specimen making unit, used for making a road test specimen (2) according to the three-dimensional topography point cloud data of the road surface; A contact test platform, used to simulate the contact environment between the tire (1) and the road test piece (2), and to collect a rubber deformation image of the tire during the contact process between the tire and the road test piece; A three-dimensional finite element model generation platform, used to generate a three-dimensional finite element model of a tire based on a tire profile geometry model after assigning material properties, and to generate a three-dimensional finite element model of a road surface based on model parameters assigned to road surface materials; A 3D point cloud generation platform, used to generate a 3D point cloud of measured tread deformation based on the tire's rubber deformation image, and to obtain a 3D point cloud of simulated tread deformation based on the tire's 3D finite element model and the road's 3D finite element model; The precision correction unit is used to update and iterate the initial value of the friction coefficient between the tire and the road test piece according to the comparison result of the measured tread deformation three-dimensional point cloud and the simulated tread deformation three-dimensional point cloud until the preset conditions are met, so as to output the final initial value of the friction coefficient; The three-dimensional stress calculation unit is used to calculate the three-dimensional stress result between the tire and the road surface according to the three-dimensional finite element model of the tire, the three-dimensional finite element model of the road surface and the initial value of the final friction coefficient.

2. The tire-road contact three-dimensional stress testing system according to claim 1, characterized in that: The road surface three-dimensional topography point cloud data is collected from the road surface area to be evaluated by contact or non-contact three-dimensional topography scanning equipment; the road surface test piece (2) is made of transparent material and is produced by 3D printing technology, and is used to replicate a road surface with real roughness.

3. The tire-road contact three-dimensional stress testing system according to claim 1, characterized in that: The contact test platform comprises a light source (7), a binocular camera (5), a speckle image layer (3) and a transparent plate (4) which are arranged in sequence from bottom to top, and a loading device for providing a pattern load; during a simulated contact process, the tire (1) and the road test piece (2) are placed on the transparent plate (4).

4. A tire-road contact three-dimensional stress testing method, characterized in that: include: Prepare road test specimens based on road 3D topography point cloud data (2); Simulating a contact environment between a tire (1) and a road test piece (2), and collecting a rubber deformation image of the tire during the contact process between the tire (1) and the road test piece (2); Generate a three-dimensional finite element model of the tire according to the tire cross-section geometric model after assigning material properties, and generate a three-dimensional finite element model of the road surface according to the model parameters assigned to the road surface material; Generating a three-dimensional point cloud of measured tread deformation according to the rubber deformation image of the tire, and obtaining a three-dimensional point cloud of simulated tread deformation according to the three-dimensional finite element model of the tire and the three-dimensional finite element model of the road surface; According to the comparison result of the measured tread deformation three-dimensional point cloud and the simulated tread deformation three-dimensional point cloud, the initial value of the friction coefficient between the tire and the road test piece is updated and iterated until the preset conditions are met, so as to output the final initial value of the friction coefficient; The three-dimensional stress result between the tire and the road is calculated based on the three-dimensional finite element model of the tire, the three-dimensional finite element model of the road, and the initial value of the final friction coefficient.

5. The tire-road contact three-dimensional stress testing method according to claim 4, characterized in that: A contact or non-contact three-dimensional topography scanning device is used to collect data on the road surface area to be evaluated, and three-dimensional topography point cloud data of the road surface is obtained; the three-dimensional topography point cloud data of the road surface is leveled, abnormal points are removed, non-test points are repaired, and filtering is performed before processing, and a 3D printing technology is used to replicate a road surface with real roughness based on the pre-processed three-dimensional topography point cloud data of the road surface, and a road test specimen (2) is obtained by combining with a transparent material; the modulus of the transparent material after curing is ≥3000 MPa; and the resolution of the 3D printing is ≥0.5 mm.

6. The tire-road contact three-dimensional stress testing method according to claim 4, characterized in that: During the process of simulating the contact between the tire (1) and the road test piece (2), the baseline distance of the binocular camera (5) is controlled within 50-100 mm and the visual axes are kept parallel.

7. The tire-road contact three-dimensional stress testing method according to claim 4, characterized in that: The specific steps for generating a tire three-dimensional finite element model based on the tire cross-section geometry model after assigning material properties are as follows: The tire profile geometry model is established in AutoCAD based on the collected geometry data of each tire structure layer, material type information and tread pattern; at the same time, the constitutive parameters of each tire structure layer material are tested through mechanical experiments; Import the tire section geometry model into HyperMesh software and mesh each tire structure layer; Import the meshed tire section geometry model into ABAQUS software, and assign material properties to each structural layer based on the constitutive parameters of the tested tire structural layer materials; Generate a three-dimensional finite element model of the tire using the tire cross-section geometry model after assigning material properties; The specific steps for generating a three-dimensional finite element model of a pavement according to the model parameters assigned to the pavement material are as follows: Import the 3D road surface model into the HyperMesh software to divide the mesh; The gridded 3D pavement topography model is imported into ABAQUS software, the model parameters of the pavement material are assigned, and the 3D finite element model of the pavement is generated.

8. The tire-road contact three-dimensional stress testing method according to claim 4, characterized in that: The specific steps for generating the measured tread deformation three-dimensional point cloud based on the tire rubber deformation image are as follows: The rubber deformation image is corrected according to the calibration results of the camera parameters, and image registration is performed based on the feature points in the rubber deformation image to ensure that the left and right images are aligned; For the corrected and aligned rubber deformation images, the disparity map is calculated using the stereo matching algorithm of OpenCV; Calculate the depth map based on the disparity map, camera focal length and baseline distance, and use the depth map to generate and save the measured tread deformation three-dimensional point cloud; The specific steps of obtaining the simulated tread deformation 3D point cloud based on the tire 3D finite element model and the road 3D finite element model are as follows: The parameters of the tire 3D finite element model and the road 3D finite element model are set, and the mixed penalty function and Lagrange multiplier method are used to solve the 3D deformation during tire-road contact to obtain the 3D point cloud of simulated tread deformation.

9. The tire-road contact three-dimensional stress testing method according to claim 4, characterized in that: The steps for obtaining the comparison results of the measured tread deformation three-dimensional point cloud and the simulated tread deformation three-dimensional point cloud are as follows: Loading the measured tread deformation 3D point cloud and the simulated tread deformation 3D point cloud; The measured tread deformation 3D point cloud is used as the target point cloud, and the simulated tread deformation 3D point cloud is used as the source point cloud, and feature point matching is performed, and the root mean square error between the measured tread deformation 3D point cloud and the simulated tread deformation 3D point cloud is calculated; Compare the RMS error with the preset threshold and output the comparison result.

10. The tire-road contact three-dimensional stress testing method according to claim 9, characterized in that: If the comparison result shows that the root mean square error is greater than the preset threshold, the initial value of the friction coefficient between the tire and the road test piece is updated and iterated using the binary method until the root mean square error is within the preset threshold; Substituting the initial value of the final friction coefficient into the three-dimensional finite element model of the tire and the three-dimensional finite element model of the road surface, the normal stress and the transverse and longitudinal tangential stresses are calculated; Otherwise, the current initial value of the friction coefficient is substituted into the three-dimensional finite element model of the tire and the three-dimensional finite element model of the road surface to calculate the normal stress and the transverse and longitudinal tangential stresses.

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