Method for analyzing the pre-stress of a finished tire carcass cord

Abstract

The application provides a kind of finished tire carcass cord prestress analysis method, comprising the following steps: S1, obtaining the machine head width value in tire forming process and the carcass cord length of finished tire;S2, separately modeling the carcass and inner liner part between the left and right bead centerline in material distribution diagram, establishing the first finite element model;S3, using simulation analysis software to divide finite element grid for the first finite element model, and performing inflation finite element analysis;S4, according to the inflation finite element analysis result, the stress size of each cord unit between the left and right bead is extracted in turn;S5, establishing the second finite element model, the carcass cord unit stress obtained in the first finite element model is applied to the second finite element model of finished tire as prestress, then the tire performance simulation analysis is carried out on the second finite element model, the tire performance analysis result under different cord prestress is obtained, and the subsequent product design and production process are adjusted accordingly.

Description

Technical Field

[0001] This invention relates to the field of tire finite element simulation technology, and in particular to an analysis method for the prestress of the cords in a finished tire carcass. Background Technology

[0002] In tire manufacturing, changes in the width of the forming machine head directly affect the cord length and wrapping height between the left and right steel wire rings. Assuming the tire's outer dimensions and rubber thickness remain constant, adjusting the forming machine head width influences the cord length between the left and right steel wire rings during the forming process. After vulcanization, the finished tire's cord will exhibit varying prestress, impacting the tire's external dimensions, imprint shape, ground pressure distribution, rolling resistance, and other performance characteristics. Therefore, accurately determining the magnitude and distribution of prestress in the finished tire's cord is crucial for guiding subsequent product design improvements and production process adjustments.

[0003] Taking semi-steel radial tires as an example, their internal cords mainly consist of carcass polyester fiber cords, belt layer steel wire cords, and crown belt nylon fiber cords. The adjustment of the width of the forming machine head mainly affects the stress distribution of the carcass polyester fiber cords, which in turn affects the outer dimensions of the finished tire, the distribution of ground pressure on the tire tracks, the shape parameters of the tire tracks, and other tire performance. Therefore, obtaining the prestress of the carcass cords has practical guiding significance for tire production. However, there is no analytical method for testing the prestress of the cords in the currently published patent documents and technical data.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The present invention addresses the shortcomings of the aforementioned technologies by providing an analytical method for the prestress of the cords in a finished tire carcass. This analytical method allows for the determination of the magnitude of the prestress in the cords of a finished tire carcass, improving the accuracy of tire performance prediction. Structural designers can then effectively adjust process parameters based on simulation analysis results to improve the stress distribution on the tire carcass and the tire's ground contact pressure, thereby enhancing tire wear resistance and other related properties.

[0006] The specific details of the technical solution provided by this invention are as follows:

[0007] A method for analyzing the prestress of the cords in a finished tire carcass includes the following steps:

[0008] S1. Obtain the width LC of the die head and the length LM of the tire carcass cord during the tire forming process;

[0009] S2. Model the tire body and inner liner between the center lines of the left and right steel wire rings in the material distribution diagram separately. The length of the tire body and inner liner is equal to the width value LC of the machine head in step S1. Based on this, establish the first finite element model.

[0010] S3. Use simulation analysis software to divide the first finite element model obtained in step S2 into finite element meshes and perform air-filling finite element analysis.

[0011] S4. Based on the results of the inflation finite element analysis, extract the stress magnitude of each cord unit between the steel wire coils from left to right. The unit numbers are unit 1, unit 2, unit 3... unit n, and the stress magnitudes of each unit are σ1, σ2, σ3... σ n , where n is a positive integer;

[0012] S5. Based on the original material distribution diagram, establish a second finite element model. Apply the stress of each unit of the tire carcass cord obtained in the first finite element model as prestress to the second finite element model of the finished tire. Then, perform tire performance simulation analysis on the second finite element model to obtain tire performance analysis results under different cord prestresses.

[0013] Furthermore, the length of the carcass cord in the finished tire is the length of the carcass cord between the center lines of the left and right steel wire rings in the material distribution diagram of the finished tire.

[0014] Furthermore, the inflation pressure during the inflation simulation process in step S3 is equal to the internal pressure of the capsule during the vulcanization process.

[0015] Furthermore, the stress magnitudes of each cord unit obtained in step S4 satisfy the formula:

[0016]

[0017] The tire cord is a linear elastic material. The elastic modulus E of each unit is obtained by obtaining the stress-strain curve of the cord based on the tensile test results, and then calculating the elastic modulus E.

[0018] Furthermore, the cord stress is a vector, and the cord stress includes tensile stress and / or compressive stress. Tensile stress is used to characterize the tensile state of the cord, and compressive stress is used to characterize the compressive state of the cord.

[0019] Furthermore, the methods for adjusting the tire cord length LM include:

[0020] In the material distribution diagram, with the center lines of the left and right steel wire rings as the reference, the length of the tire cord inside the two center lines is LM;

[0021] Adjust the length LM of the inner cords of the two center lines according to the width of the tread head. Using the outermost tire body outline as the boundary, shift the tire cords inward by a corresponding distance so that the tire body length between the left and right steel wire rings is close to the width value LC of the tread head. This completes the adjustment of the cord length.

[0022] Furthermore, the first finite element model construction process includes: separately modeling the tire body and inner liner between the center lines of the left and right steel wire rings to establish the first model, which includes: the first tire body layer, the second tire body layer and the inner liner layer inside the two center lines of the steel wire rings;

[0023] The first model is meshed into elements, and element parameters, material properties and boundary conditions are defined. The element parameters include at least one or more of the following: element shape, node coordinates and node number. The material properties include at least one or more of the following: elastic modulus, Poisson's ratio and material density. The boundary conditions include at least one or more of the following: pressure boundary conditions inside the vulcanized capsule and displacement boundary conditions. Based on this, the first finite element model is constructed.

[0024] Furthermore, simulation analysis was performed on the first finite element model to obtain the simulation analysis results, which included the stress cloud diagram of the tire cord and the stress value of each cord unit.

[0025] Furthermore, the second finite element model construction process includes: establishing a second model based on the material distribution diagram of the finished tire; the second model includes at least multiple tire components such as tread rubber, base rubber, crown belt layer, belt layer, carcass layer, sidewall rubber, bead rubber, gusset rubber, steel wire ring, and inner liner.

[0026] Furthermore, the second model is meshed, and element parameters, material properties, and boundary conditions are defined. Element parameters include at least: element shape, node coordinates, and node number; material properties include at least: elastic modulus, Poisson's ratio, material density, and cord parameters; boundary conditions include: pressure boundary conditions and displacement boundary conditions.

[0027] Compared with the prior art, the present invention has the following beneficial technical effects:

[0028] The numerical analysis method of this invention can obtain the magnitude of the prestress of the tire carcass cord, solving the problem that the magnitude of the prestress of the tire carcass cord cannot be tested. By applying the extracted cord stress to the finite element model of the finished tire and performing simulation analysis on the tire finite element model, the prediction accuracy of tire performance can be significantly improved, such as the tire's inflation outer diameter, cross-sectional width, imprint shape, ground pressure distribution and other performance parameters and their influencing laws.

[0029] By comparing the simulation analysis results with and without cord prestress, it can be found that the finite element model considering cord prestress in the tire carcass has higher simulation accuracy. It can accurately predict parameters such as tire outer dimensions and imprint shape, adjust actual process parameters, and effectively guide developers to make reasonable adjustments to product design and construction processes. Attached Figure Description

[0030] Figure 1 This represents the arc length and radius of each segment of the tire carcass cord in the tire material distribution diagram.

[0031] Figure 2 Adjust the position of the front tire carcass and inner liner to adjust the tire length;

[0032] Figure 3 To adjust the position of the tire body and inner liner according to the width of the engine head;

[0033] Figure 4 This is a material distribution diagram of the tires after adjustment based on the width of the engine head;

[0034] Figure 5 This is the first model;

[0035] Figure 6 This is the first finite element model;

[0036] Figure 7 The element numbering of the fetal body in the first finite element model;

[0037] Figure 8 The stress cloud diagram of the cord extracted from the first finite element model;

[0038] Figure 9 This is a partial view of the second finite element model for applying cord prestress;

[0039] Figure 10 (a), (b), (c), and (d) show the comparison between simulated and measured imprints.

[0040] Figure label:

[0041] 1. First body layer; 2. Second body layer; 3. Inner liner layer. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below with reference to the accompanying drawings. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0043] In the description of this invention, it should be noted that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0044] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0045] As attached Figure 1-8 As shown, this invention discloses a method for analyzing the prestress of the cords in a finished tire carcass, comprising the following steps:

[0046] S1. Obtain the width LC of the die head and the length LM of the tire carcass cord during the tire forming process;

[0047] S2. Model the tire body and inner liner between the center lines of the left and right steel wire rings in the material distribution diagram separately. The length of the tire body and inner liner is equal to the width value LC of the machine head in step S1. Based on this, establish the first finite element model.

[0048] S3. Use simulation analysis software to divide the first finite element model obtained in step S2 into finite element meshes and perform air-filling finite element analysis.

[0049] S4. Based on the results of the inflation finite element analysis, extract the stress magnitude of each cord unit between the steel wire coils from left to right. The unit numbers are unit 1, unit 2, unit 3... unit n, and the stress magnitudes of each unit are σ1, σ2, σ3... σ n , where n is a positive integer;

[0050] S5. Based on the original material distribution diagram, establish a second finite element model. Apply the stress of each unit of the tire carcass cord obtained in the first finite element model as prestress to the second finite element model of the finished tire. Then, perform tire performance simulation analysis on the second finite element model to obtain tire performance analysis results under different cord prestresses.

[0051] Traditional tire simulations often assume that the tire cords initially have no stress or uniform stress, failing to accurately reflect the non-uniform prestress distribution caused by the difference between the die head width and the finished tire carcass length during actual vulcanization. The second finite element analysis model established in this application, compared to conventional tire finite element models, incorporates prestress in the tire carcass cords, effectively improving the accuracy of finite element simulation modeling and solving the problem of neglecting the initial prestress of the cords in traditional simulations. Furthermore, by applying the actual cord stress obtained from the first model as prestress to the second model, the mechanical response of the finished tire (such as stiffness, durability, and rolling resistance) becomes closer to reality, improving the accuracy of tire performance simulation.

[0052] This application realizes closed-loop analysis from process parameters (head width) to finished product performance, improves the modeling accuracy of the initial state of tire carcass cords in tire finite element simulation, thereby improving the accuracy of tire performance prediction and providing reliable technical support for tire structure optimization and process parameter adjustment.

[0053] As an embodiment of this application, the length of the carcass cord of the finished tire is the length of the carcass cord between the center lines of the left and right steel wire rings in the material distribution diagram of the finished tire.

[0054] Furthermore, the inflation pressure during the inflation simulation process in step S3 is equal to the internal pressure of the capsule during the vulcanization process.

[0055] In the above technical solution, the limitation of the tire carcass cord length and inflation pressure can ensure the consistency between the first model and the actual structure as much as possible, realistically restore the mechanical environment of the tire from molding, vulcanization to finished tire, and ensure that the first finite element model can accurately reflect the prestress distribution of the cord in the actual tire manufacturing process.

[0056] As an implementation method of this application, the stress magnitude of each cord unit obtained in step S4 satisfies the formula:

[0057]

[0058] The tire cord is a linear elastic material. The elastic modulus E of each unit is obtained by obtaining the stress-strain curve of the cord based on the tensile test results, and then calculating the elastic modulus E.

[0059] The verification of the above formulas enhances the physical realism of the simulation model and improves the reliability of the prestress value acquisition.

[0060] Furthermore, the cord stress is a vector, including tensile stress and / or compressive stress. Tensile stress characterizes the tensile state of the cord, while compressive stress characterizes the compressive state of the cord. In conventional methods, compressive stress is typically ignored. The cord stress in this application includes both tensile and / or compressive stress, which can more comprehensively describe the stress state of the cord and identify potential defects such as cord buckling and delamination.

[0061] As an embodiment of this application, the method for adjusting the length of the tire cord includes:

[0062] In the material distribution diagram, with the center lines of the left and right steel wire rings as the reference, the length of the tire cord inside the two center lines is LM;

[0063] Adjust the length LM of the inner cords of the two center lines according to the width of the tread head. Using the outermost tire body outline as the boundary, shift the tire cords inward by a corresponding distance so that the tire body length between the left and right steel wire rings is close to the width LC of the tread head. This completes the adjustment of the cord length.

[0064] Adjusting the length of the tire cord solves the modeling problem of matching the cord length with the width of the die head during the molding stage, ensuring that the geometric parameters of the first finite element model are consistent with the actual molding state, and laying the foundation for accurately simulating the stress distribution during the inflation process.

[0065] Furthermore, the first finite element model construction process includes: separately modeling the tire body and inner liner between the center lines of the left and right steel wire rings to establish the first model, which includes: the first tire body layer 1, the second tire body layer 2 and the inner liner layer 3 on the inner side of the two center lines of the steel wire rings.

[0066] The first model is meshed into elements, and element parameters, material properties and boundary conditions are defined. The element parameters include at least one or more of the following: element shape, node coordinates and node number. The material properties include at least one or more of the following: elastic modulus, Poisson's ratio and material density. The boundary conditions include at least one or more of the following: pressure boundary conditions inside the vulcanized capsule and displacement boundary conditions. Based on this, the first finite element model is constructed.

[0067] The first finite element model is mainly based on the fact that during the molding and vulcanization process, the tire carcass cords will expand and stretch due to the molding pressure and the pressure of the vulcanizing bladder. This results in the tire carcass cord length between the widths of the die head being unequal to the tire carcass cord length between the left and right steel wire rings in the material distribution diagram of the finished tire, which causes the tire carcass cords of the finished tire to have prestress.

[0068] Furthermore, the first model is meshed into elements, and element parameters, material properties, and boundary conditions are defined. The element parameters include element shape, node coordinates, and node number. The material properties include elastic modulus, Poisson's ratio, and material density. The boundary conditions include pressure boundary conditions inside the vulcanized capsule and displacement boundary conditions. Based on this, the first finite element model is constructed.

[0069] The construction elements of the first finite model are detailed to ensure the model's integrity and feasibility. The boundary conditions are made to fit the actual vulcanization process, thereby improving the realism of the simulation.

[0070] Furthermore, simulation analysis was performed on the first finite element model to obtain the simulation analysis results, including stress cloud diagrams of the tire carcass cords and stress values ​​of each cord unit. The stress cloud diagrams of the tire carcass cords show the overall distribution trend of cord stress, and the stress values ​​of each cord unit provide accurate stress data for local units, providing multi-dimensional data support for the performance analysis of the second finite element model.

[0071] As an embodiment of this application, the second finite element model construction process includes: establishing a second model based on the material distribution diagram of the finished tire; the second model includes at least multiple tire components among: tread rubber, base rubber, crown belt layer, belt layer, carcass layer, sidewall rubber, bead rubber, gusset rubber, steel wire ring, and inner liner layer 3.

[0072] The second model is meshed, and element parameters, material properties, and boundary conditions are defined. Element parameters include at least: element shape, node coordinates, and node number; material properties include at least: elastic modulus, Poisson's ratio, material density, and cord parameters; boundary conditions include: pressure boundary conditions and displacement boundary conditions.

[0073] Furthermore, the second model includes multiple tire components such as tread rubber, base rubber, crown belt layer, belt layer, carcass layer, sidewall rubber, bead rubber, triangle rubber, steel wire ring, and inner liner layer.

[0074] The second model is meshed, and element parameters, material properties, and boundary conditions are defined. Element parameters include element shape, node coordinates, node number, etc.; material properties include elastic modulus, Poisson's ratio, material density, cord parameters, etc.; boundary conditions include pressure boundary conditions and displacement boundary conditions.

[0075] It should be noted that the pressure and displacement boundary conditions must meet the requirements of international tire performance testing standards such as "GB / T 521-2003 Method for Measurement of Outer Dimensions of Tires" and "GB / T 22038-2018 Test Method for Static Pressure Distribution of Automobile Tires", thereby constructing the second finite element model.

[0076] The constructed second finite element model has the following characteristics: the tire cords in the model have prestress magnitude, which is applied using Abaqus software with the following keywords: *initial conditions,type=stress,rebar.

[0077] The cord stress extracted from the first finite element model is applied as prestress to the second finite element model of the finished tire, and simulation analysis is performed on the second finite element model to obtain tire performance analysis results under different cord prestresses, including: tire outer dimensions, tire imprint shape, ground pressure distribution, rolling resistance and other properties.

[0078] Furthermore, by comparing the simulation analysis results with and without cord prestress, it can be found that the finite element model considering cord prestress has higher simulation accuracy and can accurately predict parameters such as tire outer dimensions and imprint shape, which can effectively guide developers to make reasonable adjustments to product design and construction processes.

[0079] For example, the following detailed explanation will be given using the calculation of the prestress of the cord in a 205 / 55R16 semi-steel radial tire as an example.

[0080] A numerical analysis method for the prestress of tire carcass cords is proposed, based on the material distribution diagram of the finished tire and the radius and central angle of each arc segment of the carcass cord between the left and right steel wire rings. The arc radii are denoted as R1, R2...Rn, and the central angles of each arc segment are denoted as α1, α2...αn. n Taking a half of the tire material distribution diagram as an example, as shown in the attached diagram. Figure 1 .

[0081] The analytical method specifically includes the following steps:

[0082] S1. The width of the forming machine head is LC. The length between the left and right steel wire loops in the material distribution diagram is LM. Calculate the difference between the two, LM-LC, to obtain the length of the tire cord that needs to be adjusted in the material distribution diagram. Using the outermost tire carcass outline as the reference, use the offset command in CAD to offset the tire carcass inwards, so that the length of the tire carcass between the center lines of the left and right steel wire loops after the offset is close to LC. The calculation of the offset amount needs to follow the following relationship:

[0083] The relationship between the central angle, arc radius, and arc length in the tire material distribution diagram is: α1∗R1+α2∗R2+…+α n *Rn=LM,

[0084] The relationship between the central angle, arc radius, and arc length after offset is: α1∗R1'+α2∗R2'+…+α n *Rn'=LC

[0085] Δ=|R1'−R1|=|R2'−R2|=…=|Rn'−Rn|

[0086] In the formula, ∆ represents the magnitude of the offset. The error between the tire carcass length and the LC length before and after the offset should be less than 0.5%. The remaining tire carcass layers and the inner liner layer 3 are offset sequentially. Figure 2 , Figure 3 , Figure 4 As shown;

[0087] S2. Separate the tire body and inner liner 3 between the adjusted steel wire ring centerlines from the material distribution diagram to establish the first model, such as... Figure 5 As shown;

[0088] S3. Perform element mesh generation on the first model to obtain the first finite element model, as follows: Figure 6 As shown;

[0089] S4. Define element parameters, material properties, and boundary conditions for displacement and inflation pressure. Perform numerical analysis on the first finite element model using simulation software, ensuring the outer contour of the first finite element model matches the contour of the outermost tire carcass before offset. At this point, stress exists within the tire carcass cords. Extract the stress from the tire carcass cords at this stress level. Figure 7 As shown;

[0090] S5. Apply the cord stress extracted in step S4 to the second finite element model, so that the tire cords in the second finite element model have prestress before inflation loading, such as... Figure 8 As shown; based on this, a 3D simulation analysis of the second finite element model can be performed to obtain the tire's inflation outer dimensions, imprint shape, and ground imprint parameters under the condition of cord prestress.

[0091] Extending the simulation method in this application, the distribution law of tire carcass cord stress under different nose widths can be obtained. Simultaneously, it can greatly improve the prediction accuracy of the tire finite element simulation model. The comparison results of tire external dimensions, imprint shape, and ground contact imprint parameters before and after applying prestress to the tire carcass cord are shown in [reference needed]. Figure 9-10 As shown in Tables 1 and 2, tire structure design engineers can effectively guide design and production, make construction decisions quickly, and improve product development efficiency based on the high-precision finite element simulation analysis results.

[0092] Table 1 compares the measured tire contact patch parameters under different conditions: with and without tire prestress.

[0093] plan Major axis / mm Short axis / mm Left shoulder length / mm Right shoulder length / mm Rectangularity <![CDATA[Grounding area / mm 2 > a Actual measurement 158.2 168.5 144.7 146.9 1.09 20110.5 b has prestress 156.1 167.1 145.2 145.2 1.08 20145.8 c No prestress 163.3 171.7 132.2 131.8 1.24 20191.4

[0094] Table 2 compares the measured external dimensions of tires with and without carcass prestress.

[0095] plan Outer diameter / mm Cross-section width / mm a Actual measurement 634.3 214.2 b has prestress 633.2 215.5 c No prestress 638.9 210.9

[0096] By comparing the simulation analysis results with and without cord prestress in Tables 1 and 2, it can be found that the finite element model considering cord prestress in the tire carcass has higher simulation accuracy and can accurately predict parameters such as tire outer dimensions and imprint shape, which can effectively guide developers to make reasonable adjustments to product design and construction processes.

[0097] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-described technical content to create equivalent embodiments without departing from the scope of the present invention. The implementation schemes in the above embodiments can also be further combined or replaced. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for analyzing the prestress of the cords in a finished tire carcass, characterized in that, Includes the following steps: S1. Obtain the width LC of the die head and the length LM of the tire carcass cord during the tire forming process; S2. Model the tire body and inner liner between the center lines of the left and right steel wire rings in the material distribution diagram separately. The length of the tire body and the inner liner is equal to the head width value LC in step S1. Based on this, establish the first finite element model. S3. Use simulation analysis software to divide the first finite element model obtained in step S2 into finite element meshes and perform inflatable finite element analysis. S4. Based on the results of the inflation finite element analysis, extract the stress magnitude of each cord unit between the steel wire coils from left to right; the stress magnitude of each cord unit satisfies the formula: ； The tire cord is a linear elastic material. The elastic modulus E of each unit is obtained by calculating the elastic modulus E based on the stress-strain curve of the cord obtained from tensile tests. i Let i represent the stress magnitude of each cord unit, where i represents the unit number, and the unit numbers are unit 1, unit 2, unit 3... unit n, where n is a positive integer; S5. Based on the original material distribution diagram, establish a second finite element model. Apply the stress of each unit of the tire carcass cord obtained in the first finite element model as prestress to the second finite element model of the finished tire. Then, perform tire performance simulation analysis on the second finite element model to obtain tire performance analysis results under different cord prestresses.

2. The method for analyzing the prestress of the cord in a finished tire carcass according to claim 1, characterized in that, The length of the carcass cord in the finished tire is the length of the carcass cord between the center lines of the left and right steel wire rings in the material distribution diagram of the finished tire.

3. The method for analyzing the prestress of the cord in a finished tire carcass according to claim 1, characterized in that, The inflation pressure in the inflation simulation process in step S3 is equal to the internal pressure of the capsule in the vulcanization process.

4. The method for analyzing the prestress of the cord in a finished tire carcass according to claim 1, characterized in that, The cord stress is a vector, and the cord stress includes tensile stress and / or compressive stress, wherein the tensile stress is used to characterize the stretched state of the cord, and the compressive stress is used to characterize the compressed state of the cord.

5. The method for analyzing the prestress of the cord in a finished tire carcass according to any one of claims 1-4, characterized in that, The method for adjusting the length of the tire cords includes: In the material distribution diagram, with the center lines of the left and right steel wire rings as the reference, the length of the tire cord inside the two center lines is LM; Adjust the length LM of the inner cords of the two center lines according to the width of the tread head. Using the outermost tire body outline as the boundary, shift the tire cords inward by a corresponding distance so that the tire body length between the left and right steel wire rings is close to the width LC of the tread head. This completes the adjustment of the cord length.

6. The method for analyzing the prestress of the cord in a finished tire carcass according to claim 5, characterized in that, The first finite element model construction process includes: modeling the tire body and inner liner between the center lines of the left and right steel wire rings separately to establish the first model, wherein the first model includes: the first tire body layer, the second tire body layer and the inner liner layer on the inner side of the two center lines of the steel wire rings. The first model is meshed into elements, and element parameters, material properties and boundary conditions are defined. The element parameters include at least one or more of the following: element shape, node coordinates and node number. The material properties include at least one or more of the following: elastic modulus, Poisson's ratio and material density. The boundary conditions include at least one or more of the following: pressure boundary conditions inside the vulcanized capsule and displacement boundary conditions. The first finite element model is constructed based on this.

7. The method for analyzing the prestress of the cord in a finished tire carcass according to claim 6, characterized in that, The first finite element model is subjected to simulation analysis to obtain the simulation analysis results of the model. The simulation analysis results include the stress cloud diagram of the tire cord and the stress value of each cord unit.

8. The method for analyzing the prestress of the cord in a finished tire carcass according to claim 7, characterized in that, The second finite element model construction process includes: establishing a second model based on the material distribution diagram of the finished tire; the second model includes at least multiple tire components such as tread rubber, base rubber, crown belt layer, belt layer, carcass layer, sidewall rubber, bead rubber, gusset rubber, steel wire ring, and inner liner.

9. The method for analyzing the prestress of the cord in a finished tire carcass according to claim 8, characterized in that, The second model is meshed into elements, and element parameters, material properties, and boundary conditions are defined. The element parameters include at least: element shape, node coordinates, and node number; the material properties include at least: elastic modulus, Poisson's ratio, material density, and cord parameters; the boundary conditions include: pressure boundary conditions and displacement boundary conditions.

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