JP6298356B2 - Tire simulation method - Google Patents

Description

  The present invention relates to a tire simulation method capable of evaluating the durability performance of a tire.

  In recent years, a simulation method for predicting the durability performance of a tire using a computer has been proposed (see, for example, Patent Document 1 below). In this type of tire simulation method, first, a tire model in which a tire to be evaluated is modeled with a finite number of elements is set. And about the tire model, the durable performance of a tire is evaluated from the log | history of the distortion which arises by one rotation.

Japanese Patent Laid-Open No. 2003-200722

  In the simulation method as described above, the evaluation accuracy of the durability performance is not sufficient, and there is room for further improvement.

  As a result of intensive studies, the inventors have found that it is effective to evaluate the durability performance based on both the strain amplitude, which is an index indicating deformation, and the Mises stress, which is an index indicating heat generation. did.

  The present invention has been devised in view of the above circumstances, and has as its main object to provide a simulation method capable of evaluating the durability performance of a tire with high accuracy.

The present invention, using a computer, a simulation method for evaluating the durability of the tire, to the computer, the tire, the step of inputting the modeled tire model using a finite number of elements, the A step of inputting a road surface model obtained by modeling a road surface on which the tire contacts the ground using a finite number of elements; and a step of calculating a ground contact state of the tire model based on a predetermined condition. A physical quantity calculating step in which the computer calculates a physical quantity including a strain amplitude and a Mises stress acting on at least one of the predetermined elements from the ground contact state of the tire model; and the computer based on the amplitude and the Mises stress, look including an evaluation step of evaluating the durability of the element The physical quantity calculating step calculates the Mises stress of the first element, and calculates the Mises stress of the second element at the same position in the tire meridian section and at a different position in the tire circumferential direction. A step of calculating a difference Δσ between the Mises stress of the first element and the Mises stress of the second element, and a step of evaluating the durability performance higher as the difference Δσ is smaller. The first element is on a ground surface side where the tire model is in contact with the road surface model, and the second element is at a position shifted by 180 degrees in the tire circumferential direction from the first element. It is characterized by that.

In the simulation method of the tire according to the present invention, the physical quantity calculating step includes calculating a strain amplitude of said first element, and calculating the strain amplitude of the second element, wherein the evaluation step, It is desirable to include a step of calculating the difference Δa between the strain amplitude of the first element and the strain amplitude of the second element, and a step of evaluating the durability performance higher as the difference Δa is smaller.

In the tire simulation method according to the present invention, the physical quantity calculation step includes a step of calculating strain amplitudes of all elements in the tire circumferential direction at the same position in a tire meridian cross section, and the evaluation step includes , strain and amplitude of the first element, wherein the step of calculating the difference Δa between the strain amplitude of the second element, and includes the step who appreciate higher durability as the difference Δa is small desirable.

  In the tire simulation method of the present invention, the durability performance of an element is evaluated based on the strain amplitude and Mises stress acting on at least one of the predetermined elements in the ground contact state of the tire model.

  Strain amplitude is an indicator related to deformation due to tension and compression occurring in an element. The Mises stress is an index related to the shear strain energy generated in the element, that is, heat generation. These deformations and heat generation are major factors that damage the tire. Therefore, in the present invention, the durability performance of the elements of the tire model is evaluated based on both the index indicating deformation and the index indicating heat generation. Therefore, the tire performance can be evaluated with high accuracy.

It is a perspective view of the computer for performing the simulation method of the tire of this embodiment. It is sectional drawing of the tire evaluated by the simulation method of this embodiment. It is a flowchart which shows an example of the process sequence of the simulation method of this embodiment. It is sectional drawing of the tire model of this embodiment. It is a perspective view of a tire model and a road surface model. It is a flowchart which shows an example of the process sequence of the grounding process of this embodiment. It is a flowchart which shows an example of the process sequence of the physical quantity calculation process of this embodiment. It is a figure explaining the process of calculating the history of distortion of a tire model statically. It is a flowchart which shows an example of the process sequence of the Mises stress calculation process of this embodiment. It is a flowchart which shows an example of the process sequence of the evaluation process of this embodiment. It is a graph which shows the relationship of the difference of the distortion amplitude of an Example, the difference of Mises stress, and drum durability performance. It is a graph which shows the relationship between the difference of the distortion amplitude of the comparative example 1, and drum durability performance. It is a graph which shows the relationship between the difference of Mises stress of the comparative example 2, and drum durable performance.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
The tire simulation method of the present embodiment (hereinafter sometimes simply referred to as “simulation method”) is a method for evaluating the durability performance of a tire using a computer.

  FIG. 1 is a perspective view of a computer 1 for executing the simulation method of the present embodiment. The computer 1 includes a main body 1a, a keyboard 1b, a mouse 1c, and a display device 1d. The main body 1a is provided with an arithmetic processing unit (CPU), a ROM, a working memory, a storage device such as a magnetic disk, and disk drive devices 1a1, 1a2. Note that a processing procedure (program) for executing the simulation method of the present embodiment is stored in the storage device in advance.

  FIG. 2 is a cross-sectional view of a tire evaluated by the simulation method of the present embodiment. The tire 2 is configured as a passenger car tire, for example. The tire 2 according to this embodiment includes a rubber portion 3 including a tread rubber, a carcass 6 and a belt layer 7.

  The carcass 6 is composed of at least one carcass ply 6A in this embodiment. The carcass ply 6A includes a main body portion 6a extending from the tread portion 2a through the sidewall portion 2b to the bead core 5 of the bead portion 2c, and a turn around the bead core 5 connected to the main body portion 6a from the inner side to the outer side in the tire axial direction. Part 6b. A bead apex rubber 3b extending from the bead core 5 to the outer side in the tire radial direction is disposed between the main body portion 6a and the folded portion 6b. In the carcass ply 6A, for example, carcass cords arranged at an angle of 80 degrees to 90 degrees with respect to the tire equator C are overlapped so as to cross each other.

  The belt layer 7 is disposed on the outer side in the tire radial direction of the carcass 6 and inside the tread portion 2a. The belt layer 7 of the present embodiment includes an inner belt ply 7A and an outer belt ply 7B disposed on the outer side in the tire radial direction of the inner belt ply 7A. These belt plies 7A and 7B are arranged such that the belt cords are inclined at an angle of, for example, 10 degrees to 35 degrees with respect to the tire circumferential direction. The belt cords of the belt plies 7A and 7B are overlapped in a direction intersecting with each other.

  FIG. 3 is a flowchart illustrating an example of a processing procedure of the simulation method of the present embodiment. In the simulation method of the present embodiment, first, a tire model obtained by modeling the tire 2 shown in FIG. 2 is input to the computer 1 (step S1). FIG. 4 is a cross-sectional view of the tire model 10 of the present embodiment.

  The tire model 10 is set by modeling (discretizing) the tire 2 shown in FIG. 2 with a finite number of elements F (i) (i = 1, 2,...) That can be handled by a numerical analysis method. ing. As the numerical analysis method, for example, a finite element method, a finite volume method, a difference method, or a boundary element method can be appropriately employed. In this embodiment, the finite element method is adopted.

  In step S1, the rubber part 3, the carcass ply 6A, and the belt plies 7A and 7B shown in FIG. 2 are modeled by an element F (i). Thereby, the rubber model 11, the carcass ply model 12A, and the belt ply models 13A and 13B are set. Such model setting (modeling) can be easily performed by using, for example, design data (for example, CAD data) of a vulcanization mold and meshing software, as in the conventional method. it can. Further, it is desirable that the actual tire finish value be reflected in the setting of each model. Thereby, a highly accurate model can be set. The tire model 10 is set by sequentially setting the rubber model 11, the carcass ply model 12A, and the belt ply models 13A and 13B.

  Each element F (i) is provided with a plurality of nodes 14. Each element F (i) includes numerical values such as an element number, a node 14 number, a coordinate value of the node 14, and material properties (for example, density, Young's modulus, damping coefficient, loss tangent tan δ, etc.). Data is defined. The tire model 10 is stored in the computer 1.

  Next, in the simulation method of the present embodiment, a road surface model in which the road surface (not shown) on which the tire 2 (shown in FIG. 2) contacts is modeled with a finite number of elements is input to the computer 1 (step S2). ). FIG. 5 is a perspective view of the tire model 10 and the road surface model 15.

  The road surface model 15 is modeled by, for example, a rigid surface element G constituting a single plane. Thereby, the road surface model 15 is defined so as not to be deformed even when an external force is applied. The road surface model 15 may be formed on a cylindrical surface like a drum tester, for example. Further, the road surface model 15 may be provided with steps, depressions, undulations, ridges, or the like as necessary. The road surface model 15 is stored in the computer 1.

  Next, in the simulation method of the present embodiment, boundary conditions are defined in the tire model 10 and the road surface model 15 in the computer 1 (step S3). The boundary condition is a condition for bringing the tire model 10 shown in FIG. In the present embodiment, as in the conventional simulation method, for example, the internal pressure, the load (including the longitudinal load and the lateral load), the camber angle, the static friction coefficient, and the like of the tire model 10 are appropriately set. Further, as a boundary condition, a rim model 18 in which the rim 17 assembled to the tire 2 shown in FIG. 2 is modeled (discretized) with a finite number of elements (not shown) is set. Such a condition is stored in the computer 1.

  Next, in the simulation method of the present embodiment, the computer 1 calculates the ground contact state of the tire model 10 based on a predetermined condition (ground contact step S4). FIG. 6 is a flowchart illustrating an example of a processing procedure of the grounding step S4 of the present embodiment.

  In the ground contact step S4 of the present embodiment, first, the shape after the internal pressure filling of the tire model 10 (shown in FIG. 4) is calculated (step S41). In step S41, first, the bead portion 10c of the tire model 10 is restrained by the rim model 18 so that it cannot be deformed. Next, in the tire model 10, an equally distributed load w corresponding to the internal pressure condition is defined on the tire cavity surface. Based on this equally distributed load w, deformation calculation of the tire model 10 is performed. Thereby, in process S41, tire model 10 after internal pressure filling is calculated.

  In the deformation calculation of the tire model 10, a mass matrix, a stiffness matrix, and a damping matrix of each element F (i) are created based on the shape and material characteristics of each element. Furthermore, each of these matrices is combined to create a matrix for the entire system. Then, the computer 1 applies the above-mentioned various conditions to create an equation of motion, which is transformed into the tire model 10 every unit time T (x) (x = 0, 1,...) (For example, every 1 μsec). Perform the calculation. Such deformation calculation can be performed using, for example, commercially available finite element analysis application software such as LS-DYNA manufactured by LSTC.

  Next, in the ground contact step S4 of the present embodiment, the shape after the load is applied is calculated in the tire model 10 after filling with internal pressure (step S42). In step S42, as shown in FIG. 5, a state in which the tire model 10 after filling with the internal pressure is deformed is calculated based on a load T predetermined as a boundary condition. Thereby, in the step S42, the tire model 10 in a stationary state in contact with the road surface model 15 is calculated. A camber angle may be set in the tire model before the deformation of the tire model 10 after the internal pressure filling is calculated based on the load T. Thereby, in process S42, the tire model 10 can be approximated to the stationary state of the tire 2 with which the actual vehicle was mounted | worn.

  Next, in the simulation method of the present embodiment, the computer 1 calculates a physical quantity including strain amplitude and Mises stress acting on at least one of the predetermined elements F (i) from the ground contact state of the tire model 10. (Physical quantity calculation step S5).

  In the physical quantity calculation step S5 of the present embodiment, an element (hereinafter, simply referred to as “evaluation target element”) 21 for calculating the strain amplitude and the Mises stress is a plurality of models (for example, the tire model 10). , Carcass ply model 12A or belt ply models 13A, 13B, etc.) can be appropriately selected from elements F (i). As the evaluation target element 21 of the present embodiment, the element F (i) constituting the outer end portion 13At in the tire axial direction of the belt ply model 13A is selected. The evaluation target element 21 is continuously provided in the tire circumferential direction in the tire model 10. For this reason, each evaluation object element 21 is arranged at the same position in each tire meridian cross section. FIG. 7 is a flowchart illustrating an example of a processing procedure of the physical quantity calculation step S5 of the present embodiment.

  In the physical quantity calculation step S5 of the present embodiment, first, a history of strain generated by one rotation in the tire model 10 in a stationary state is calculated (step S51). In the present embodiment, the tire model 10 in the stationary state is assumed to be substantially equal to the dynamic strain that is received in a moment when the tire is rolling, so that the tire model 10 in the stationary state rotates once. A history of distortion caused by the calculation is calculated. Note that the strain history is calculated for all elements F (i) constituting the tire model 10.

  FIG. 8 is a diagram illustrating a process of statically calculating the strain history of the tire model 10. In FIG. 8, the elements F (1) and F (2) of the rubber model 11 and a part of the element F (i) constituting the outer end portion 13At of the belt ply model 13A are shown. Each strain acts on the elements F (1) and F (2) adjacent on one side in the tire circumferential direction. The tire model 10 is modeled so that elements having equal tire circumferential lengths are equally distributed and the same tire meridian cross-sectional shape is continuous. For this reason, for example, as for the distortion which the element F (2) in the state of FIG. 8 receives, the element F (1) moved to the position of the element F (2) by the tire model 10 rotating by one element. It can be assumed that it is substantially equal to the strain experienced. Based on such an assumption, by referring to the distortion of each element F (i) that is continuous in the tire circumferential direction, the history of the distortion of each element F (i) that is caused by one rotation of the tire model 10 is obtained. It can be calculated in a pseudo manner. Such strain history calculation can also be performed using the above-described finite element analysis application software.

  Next, in the physical quantity calculation step S5 of the present embodiment, the strain amplitude of the evaluation target element 21 is calculated (step S52). The strain amplitude (Epcilon All Total: EAT) is calculated by the sum of the vertical strain variation Δε and the shear strain variation Δγ in each element F (i). The vertical strain change Δε and the shear strain change Δγ are calculated based on the strain history of the tire model 10 calculated in step S52.

Variation [Delta] [epsilon] of vertical distortion, x-axis, in the global coordinate system composed of a y-axis and z-axis, x-axis direction of the normal strain of variation [Delta] [epsilon] _x, y-axis direction of the normal strain of variation [Delta] [epsilon] _y, and , The amount of change Δε _{z in} the vertical strain in the z-axis direction is included. For example, the amount of change Δε _{x in} the vertical strain in the x-axis direction can be defined by the following equation. The vertical strain changes Δε _y and Δε _z can also be defined in the same manner as the vertical strain changes Δε _x .
Δε _x = (L−L ₀ ) / L ₀ = ΔL / L ₀
Here, each variable is as follows.
L ₀ : length before deformation (x-axis direction)
L: Length after deformation (x-axis direction)
ΔL: Length change (x-axis direction)

The change amount Δγ of the shear strain indicates a change amount when a force is applied in a direction different from the normal strain (for example, simultaneously in the x-axis direction and the y-axis direction). The amount of change Δγ in the shear strain of the present embodiment is the amount of change in shear strain Δγ _xy in the x-axis direction and the y-axis direction, the amount of change in shear strain Δγ _yz in the y-axis direction and the z-axis direction, and the z-axis direction and The change amount Δγ _zx of the shear strain in the x-axis direction is included. For example, the change amount Δγ _xy of the shear strain in the x-axis direction and the y-axis direction can be defined by the following equation. In addition, the change amounts Δγ _yz and Δγ _{zx of} each shear strain can be defined in the same manner as the change amount Δγ _xy of the shear strain.
Δγ _xy = ΔL _x / L _y + ΔL _y / L _x
Here, each variable is as follows.
L _x : length in the x-axis direction L _y : length in the y-axis direction ΔL _x : displacement in the x-axis direction with respect to the length L _{y in the y-} axis direction ΔL _y : y-axis direction with respect to the length L _{x in} the x-axis direction Displacement

Based on the change amounts Δε _x , Δε _y , Δε _x of each vertical strain and the change amounts Δγ _xy , Δγ _yz , Δγ _zx of the respective shear strains as described above, the strain amplitude EAT is expressed by the following equation (1). Can be defined. Such strain amplitude EAT can be used as an index related to deformation caused by tension and compression occurring in the element F (i).

  In step S52 of the present embodiment, the strain amplitude EAT is calculated in all the evaluation target elements 21 in the tire circumferential direction. The strain amplitude EAT of each element 21 is stored in the computer 1.

Next, in the physical quantity calculation step S5 of the present embodiment, the Mises stress of the evaluation target element 21 is calculated (Mises stress calculation step S53). The Mises stress is one of the equivalent stresses used to indicate, with a single value, a stress state in which a load is applied in a complex manner from multiple directions inside the object. This Mises stress is proportional to the shear strain energy per unit volume. For this reason, Mises stress can be used as a parameter | index relevant to heat_generation | fever. The Mises stress σ ² _Mises is defined by the following formula (2). Each principal stress σ ₁ , σ ₂ , σ ₃ is selected from the principal stress in the x-axis direction, the principal stress in the y-axis direction, or the principal stress in the z-axis direction that acts on the element.

Here, each variable is as follows.
σ ₁ : Maximum principal stress σ ₂ : Intermediate principal stress σ ₃ : Minimum principal stress

In the Mises stress calculation step S53 of the present embodiment, the Mises stress σ ² _Mises is calculated in the first element 25a and the second element 25b selected from all the evaluation target elements 21. The first element 25a and the second element 25b are located at the same position in the tire meridian cross section and are arranged at different positions in the tire circumferential direction. FIG. 9 is a flowchart illustrating an example of the processing procedure of the Mises stress calculation step S53 of the present embodiment.

  In the Mises stress calculation step S53 of this embodiment, first, the Mises stress of the first element 25a is calculated (step S531). As shown in FIG. 8, the first element 25 a of the present embodiment is arranged on the side of the contact surface 27 where the tire model 10 is in contact with the road surface model 15 among all the evaluation target elements 21 in the tire circumferential direction. One element 21 to be selected is selected.

Here, the element 21 on the ground contact surface 27 side is arranged in a region 28 of an imaginary line 27 s extending from the outer periphery 27 o (shown in FIG. 5) of the ground contact surface 27 to the inside in the tire radial direction among all the evaluation target elements 21. Element 21. Such a region 28 where the first element 25a is disposed is a portion where a relatively large force acts on the outer end portion 13At of the belt ply model 13A during tire rolling. Accordingly, the first element 25a has a larger Mises stress σ ² _Mises than the evaluation target element 21 that is not arranged on the ground contact surface 27 side. The Mises stress σ ² _Mises of the first element 25 a is stored in the computer 1.

Next, in the Mises stress calculation step S53, the Mises stress σ ² _Mises of the second element 25b is calculated (step S532). As the second element 25b of the present embodiment, one element 21 that is not arranged on the ground contact surface 27 side is selected from all the evaluation target elements 21 in the tire circumferential direction. For this reason, the Mises stress σ ² _Mises of the second element 25b is smaller than the Mises stress σ ² _Mises of the first element 25a. The Mises stress σ ² _Mises of the second element 25 ^b is stored in the computer 1.

Next, in the simulation method of the present embodiment, the computer 1 evaluates the durability performance of the tire (evaluation target element 21) based on the strain amplitude EAT and the Mises stress σ ² _Mises (evaluation step S6). FIG. 10 is a flowchart illustrating an example of a processing procedure of the evaluation step S6 of the present embodiment.

  In the evaluation step S6 of the present embodiment, first, a difference Δa between the strain amplitude EAT of the first element 31a and the strain amplitude EAT of the second element 31b is calculated (step S61).

  As the first element 31a of the present embodiment, the element 21 having the largest strain amplitude EAT is selected from all the evaluation target elements 21. As the second element 31b, the element 21 having the smallest strain amplitude EAT is selected from all the evaluation target elements 21. The first element 31a and the second element 31b are arranged at different positions in the tire circumferential direction. Accordingly, the difference Δa between the strain amplitude EAT of the first element 31a and the strain amplitude EAT of the second element 31b is a range (range) of the strain amplitude EAT generated at the outer end portion 13At of the belt ply model 13A formed by the evaluation target element 21. ) Such a distortion amplitude difference Δa is stored in the computer 1.

Next, evaluation step S6 in the present embodiment, the difference between the Mises stress sigma ² _Mises first element 25a and the Mises stress sigma ² _Mises of the second element 25b .DELTA..sigma is calculated (step S62). As described above, the Mises stress σ ² _Mises of the first element 25a is larger than the Mises stress σ ² _Mises of the element F (i) not arranged on the ground plane 27 side. On the other hand, the Mises stress σ ² _Mises of the second element 25b is smaller than the element F (i) arranged on the contact surface 27 side, that is, the Mises stress σ ² _Mises of the first element 25a. Therefore, the difference Δσ between the Mises stress sigma ² _Mises Mises stress sigma ² _Mises first element 25a and the second element 25b is Mises stress generated in the outer end portion 13At belt plies model 13A the evaluation target element 21 constitutes sigma ² Approximate to the _Mises range. Such Mises stress difference Δσ is stored in the computer 1.

Next, in the evaluation step S6 of the present embodiment, the difference Δa between the strain amplitude EAT of the first element 31a and the strain amplitude EAT of the second element 31b, the Mises stress σ ² _Mises of the first element 25a, and the second element 25b. The durability performance of the tire (evaluation target element 21) is evaluated based on the difference Δσ from the Mises stress σ ² _Mises (step S63).

  As described above, the strain amplitude EAT is an index related to deformation caused by tension and compression generated in the element. The larger the difference Δa (that is, the range) between the strain amplitude EAT of the first element 31a and the strain amplitude EAT of the second element 31b, the greater the difference of the belt ply model 13A that the evaluation target element 21 constitutes while the tire 2 rotates once Deformation due to tension and compression occurring in the outer end portion 13At is large. On the other hand, the smaller the strain amplitude difference Δa (ie, the range), the smaller the deformation of the outer end portion 13At of the belt ply model 13A. Such deformation of the outer end portion 13At of the belt ply model 13A is a major factor that damages the tire 2. Therefore, it can be considered that the durability performance of the tire (evaluation target element 21) becomes better as the strain amplitude difference Δa is smaller.

The Mises stress σ is an index related to shear strain energy generated in the element, that is, heat generation. First differential element 25a Mises stress sigma ² _Mises and the Mises stress sigma ² _Mises of the second element 25b .DELTA..sigma (i.e., range) the larger, while the tire rotates once, a belt evaluated element 21 constitute Heat generation at the outer end 13At of the ply model 13A is large. On the other hand, the smaller the Mises stress difference Δσ, the smaller the heat generation at the outer end 13At of the belt ply model 13A. Such heat generation at the outer end portion 13At of the belt ply model 13A is also a major factor that damages the tire 2. Therefore, it can be considered that the durability performance of the tire (evaluation target element 21) becomes better as the Mises stress difference Δσ is smaller.

  And in process S63 of this embodiment, it is evaluated that the durability performance of a tire (evaluation object element 21) is so high that both the difference delta a of distortion amplitude and the difference delta-sigma of Mises stress are small. On the other hand, if one of the strain amplitude difference Δa or the Mises stress difference Δσ is large, or if both the strain amplitude difference Δa and the Mises stress difference Δσ are large, the tire durability performance is evaluated to be low. ing. As described above, in the present embodiment, the durability performance of the tire is evaluated based on both the index indicating deformation and the index indicating heat generation. For this reason, the durability performance of a tire can be evaluated with high accuracy.

In the present embodiment, in the physical quantity calculation step S5, the strain amplitude EAT and Mises stress σ ² _Mises acting on the element F (i) are calculated by a static simulation for calculating the ground contact state of the tire model 10. For this reason, for example, compared with the case where the dynamic simulation which rolls the tire model 10 to the road surface model 15 is implemented, calculation time can be shortened significantly.

As shown in FIG. 8, as the first element 25a for which the Mises stress σ ² _Mises is calculated, the evaluation target element 21 having the largest Mises stress σ ² _Mises is selected from all the evaluation target elements 21. Is desirable. The evaluation target element 21 having the largest Mises stress σ ² _Mises includes a straight line 30 extending from the center position 29 in the tire circumferential direction of the ground contact surface 27 and the tire axial direction to the tire radial direction among all the evaluation target elements 21. It is the evaluation target element 21 that intersects. Thus, the first element 25a, as compared to the other evaluation target element 21, it is possible to calculate the largest Mises stress sigma ² _Mises, Mises stress sigma ² _Mises first element 25a and the second element 25b the difference Δσ between the Mises stress sigma ² _Mises, the scope of the Mises stress sigma ² _Mises occurring outer end 13At belt ply model 13A (range), it is possible to further approximate. Therefore, the durability performance of the tire (evaluation target element 21) can be evaluated with higher accuracy.

In addition, as the second element 25b for which the Mises stress σ ² _Mises is calculated, among all the evaluation target elements 21, the element 21 disposed at a position shifted by 180 degrees in the tire circumferential direction from the first element 25a. It is desirable to be selected. Such a second element 25b is a portion where the force acting at the time of tire rolling is the smallest in the outer end portion 13At of the belt ply model 13A formed by the evaluation target element 21. In such a second element 25b, as compared to the other evaluation target element 21, it is possible to calculate the smallest larger Mises stress sigma ² _Mises, Mises stress sigma ² _Mises and the second element 25b of the first element 25a the difference Δσ between the Mises stress sigma ² _Mises of, the scope of the Mises stress sigma ² _Mises occurring outer end 13At belt ply model 13A (range), can be further approximated. Therefore, the durability performance of the tire (evaluation target element 21) can be evaluated with higher accuracy.

  Next, in the simulation method of the present embodiment, it is determined whether or not the durability performance of the tire (evaluation target element 21) is good (step S7). In step S7, when it is determined that the durability performance of the tire is good (“Y” in step S7), the tire 2 is manufactured based on the tire model 10 (step S8). On the other hand, when it is determined that the durability performance of the tire is not good (“N” in step S7), the design factor of the tire 2 is changed (step S9), and steps S1 to S7 are executed again. Thus, in the simulation method of the present embodiment, it is possible to reliably design the tire 2 with good durability performance.

  In the physical quantity calculation step S5 of the present embodiment, the example in which the strain amplitude EAT is calculated in all the evaluation target elements 21 in the tire circumferential direction is not limited to this. For example, the strain amplitude EAT may be calculated in two elements 21 (first element 31a and second element 31b) selected from all the evaluation target elements 21.

The first element 31a is preferably the same as the first element 25a for which the Mises stress σ ² _Mises is calculated. Since the first element 31a has a larger strain at the time of tire rolling than the other evaluation target elements 21, a large strain amplitude EAT is calculated.

The second element 31b is preferably the same as the second element 25b for which the Mises stress σ ² _Mises is calculated. Since the second element 31b has a smaller strain at the time of rolling of the tire than the other evaluation target elements 21, a small strain amplitude EAT is calculated.

  The strain amplitude EAT difference Δa is calculated on the basis of each strain amplitude EAT of the first element 31a and the second element 31b, and the strain amplitude difference Δa is calculated as the outer end portion of the belt ply model 13A. It can be approximated to the range (range) of the strain amplitude EAT occurring at 13 At. Therefore, in such an embodiment, since it is not necessary to calculate the strain amplitude EAT in all the evaluation target elements 21 in the tire circumferential direction, the calculation time can be greatly shortened.

In the present embodiment, the Mises of one first element 25a and one second element 25b are calculated in the tire meridian cross section, but the present invention is not limited to this. For example, the Mises stress σ ² _Mises may be calculated for the plurality of first elements 25a and the plurality of second elements 25b in the tire meridian cross section.

In this case, in the tire meridian cross section, for each of the plurality of first element 25a, to Mises stress sigma ² _Mises may be calculated, by averaging the Mises stress sigma ² _Mises of the plurality of first element 25a, one of the The Mises stress σ ² _Mises may be calculated. The second element 25b is the same as the first element 25a. Thereby, the durability performance can be evaluated over a wide range of the elements F (i) constituting the tire model 10. As for the strain amplitude EAT, similarly to the Mises stress σ ² _Mises , the strain amplitude EAT may be obtained for a plurality of first elements 25a and a plurality of second elements 25b in the tire meridian cross section.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

  Twelve tires (tire 1 to tire 12) having the basic structure shown in FIG. 2 and having different carcass ply or belt ply structures were manufactured. Twelve tire models in which these 12 tires were modeled with a finite number of elements were set. Then, based on the strain amplitude difference Δa and Mises stress difference Δσ measured according to the processing procedure shown in FIG. 3, the durability performance of the tire was evaluated (Example). Note that the strain amplitude difference Δa and the Mises stress difference Δσ are indicated by an index with the tire 1 as 100. The smaller the value, the better.

  For comparison, a method for evaluating the durability of a tire based only on the difference Δa in strain amplitude (Comparative Example 1) and a method for evaluating the durability of a tire based only on the difference Δσ of Mises stress (Comparative Example 2) was similarly carried out.

  Twelve tires were assembled on the following rim, filled with the following internal pressure, loaded with the following load, and run on the drum tester at a speed of 80 km / h. Then, the travel distance until the tire broke was examined (experimental example). In the evaluation of the drum durability performance, the travel distance was expressed as an index with the tire 1 as 100. The larger the value, the better.

The strain amplitude difference Δa or Mises stress difference Δσ measured in the example, comparative example 1 and comparative example 2 and the evaluation of the drum durability performance of the experimental example are shown in FIG. 11 (Example) and FIG. The results are shown in the graphs of Comparative Example 1) and FIG. 13 (Comparative Example 2). The common specifications are as follows.
Tire size: 265 / 35R18
Rim size: 18 × 9.5J
Internal pressure: 200 kPa
load:
Longitudinal load: 3kN
Lateral load: 3kN

  As a result of the test, in the example, it was confirmed that the drum durability performance was better as the tire had smaller strain amplitude difference Δa and Mises stress difference Δσ. Therefore, it was confirmed that the simulation method of the example can evaluate the durability performance of the tire with high accuracy.

  On the other hand, in Comparative Example 1, the range of strain amplitude difference Δa that can be taken by a tire having the same drum durability performance overlaps with each range of strain amplitude difference Δa that other tires having the same drum durability performance can take. . Similarly, in Comparative Example 2, each range of Mises stress difference Δσ that a tire with the same drum durability performance can take and each range of Mises stress difference Δσ that a tire with the same drum durability performance can take Duplicate. Therefore, in the simulation methods of Comparative Example 1 and Comparative Example 2, the durability performance of the tire could not be evaluated with sufficient accuracy.

1 Computer 10 Tire model F (i) Element

Claims (3)

A simulation method for evaluating the durability performance of a tire using a computer,
Inputting to the computer a tire model obtained by modeling the tire using a finite number of elements;
Inputting to the computer a road surface model obtained by modeling the road surface on which the tire contacts the ground using a finite number of elements;
The computer calculating a ground contact state of the tire model based on a predetermined condition;
A physical quantity calculating step in which the computer calculates a physical quantity including a strain amplitude and a Mises stress acting on at least one of the predetermined elements from the ground contact state of the tire model; and and based on the von Mises stress, look including an evaluation step of evaluating the durability of the element,
The physical quantity calculation step includes:
Calculating the Mises stress of the first element;
Calculating the Mises stress of the first element and the second element at the same position in the tire meridian cross section and at different positions in the tire circumferential direction,
The evaluation step includes calculating a difference Δσ between the Mises stress of the first element and the Mises stress of the second element;
Including a step of evaluating the durability performance higher as the difference Δσ is smaller,
The first element is on a contact surface side where the tire model is in contact with the road surface model,
The tire simulation method according to claim 1, wherein the second element is located 180 degrees away from the first element in the tire circumferential direction . The physical quantity calculation step includes:
Calculating a strain amplitude of the first element;
Calculating a strain amplitude of the second element;
The evaluation step calculates a difference Δa between the strain amplitude of the first element and the strain amplitude of the second element;
The tire simulation method according to claim 1 , further comprising the step of evaluating the durability performance higher as the difference Δa is smaller . The physical quantity calculation step includes:
Calculating the strain amplitude of all the elements in the tire circumferential direction at the same position in the tire meridian section,
The evaluating step calculating a difference Δa between the strain amplitude of the first element and the strain amplitude of the second element;
The tire simulation method according to claim 1, further comprising a step of evaluating the durability performance higher as the difference Δa is smaller .