Tire simulation method

Abstract

To provide a tire simulation method capable of easily calculating a physical quantity acting along a tire surface.SOLUTION: A method of simulating a tire. The simulation method includes a step of inputting a tire model 2A obtained by discretizing a tire with a finite number of elements to a computer 1, and a step of calculating a physical quantity of the elements when the tire model 2A is deformed under a predetermined condition by the computer 1. The tire model 2A includes a composite surface portion 7 including, as elements, three dimensional elements F (i) having first surfaces 6 corresponding to the surfaces of the tire and film elements G (i) disposed on the first surfaces 6. The film element G (i) is deformed together with the first surface 6 and has a small thickness at which the stress in the thickness direction is negligible.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a tire simulation method. [Background technology]

[0002] Patent Document 1 below discloses a tire model for simulation. In this tire model, rubber portions corresponding to the tire surface, such as tread rubber and sidewall rubber, are modeled using three-dimensional solid elements. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-216167 Summary of the Invention [Problem to be solved by the invention]

[0004] When evaluating the damage resistance and crack resistance of tires, it is important to know the magnitude and direction of the physical quantities (strain and stress) acting on the tire surface. If these physical quantities could be calculated using computer simulation, the amount of man-hours required for prototyping and testing could be significantly reduced.

[0005] Generally, the surface of a tire model used in simulations is composed of three-dimensional elements (e.g., three-dimensional solid elements) with a certain thickness that mimics rubber. The maximum principal stress and maximum principal strain calculated from such three-dimensional elements do not necessarily act along the tire surface, so the maximum principal stress and maximum principal strain acting on the tire surface must be calculated separately after the simulation calculation.

[0006] The present invention has been devised in view of the above circumstances, and its main object is to provide a tire simulation method that can easily calculate physical quantities acting along the tire surface. [Means for solving the problem]

[0007] The present invention is a tire simulation method comprising the steps of inputting a tire model, in which the tire is discretized into a finite number of elements, into a computer, and calculating, by the computer, physical quantities of the elements when the tire model is deformed under predetermined conditions, wherein the tire model includes, as the elements, a composite surface portion including a three-dimensional element having a first surface corresponding to the surface of the tire and a membrane element arranged on the first surface, and the membrane element deforms together with the first surface and has a thickness so thin that stress in the thickness direction can be ignored. [Effects of the Invention]

[0008] By employing the above-described configuration, the tire simulation method of the present invention can easily calculate physical quantities acting along the tire surface. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view of a computer device that implements a tire simulation method according to an embodiment of the present invention. [Figure 2] 1 is a flowchart illustrating an example of a processing procedure of a tire simulation method. [Figure 3] 10 is a flowchart showing an example of a processing procedure of a tire model input step. [Figure 4] FIG. 1 is a cross-sectional view illustrating a visualization of an example of a tire model. [Figure 5] FIG. 1 is a partial perspective view of a tire model showing visualization of three-dimensional elements and membrane elements. [Figure 6] FIG. 1 is a perspective view showing a visualization of three-dimensional elements and membrane elements. [Figure 7] 10 is a flowchart showing an example of a processing procedure of a physical quantity calculation step. [Figure 8](a) is a diagram showing a tire model deformed under internal pressure conditions, (b) is a diagram showing a tire model deformed under load conditions, and (c) is a diagram showing a tire model deformed under rolling conditions. [Figure 9] FIG. 10 is a partial perspective view of a tire simulation model including analysis target portions of Example 2 and Comparative Example 2. [Figure 10] FIG. 10 is a contour diagram showing the maximum principal stress (tensile) vector acting on the surface of part X in FIG. 9 as a calculation result of Example 2. [Figure 11] FIG. 10 is a contour diagram showing the maximum principal stress (tensile) vector acting on the surface of part X in FIG. 9 as a calculation result of Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the present invention will now be described with reference to the drawings. The tire simulation method of this embodiment (hereinafter, sometimes simply referred to as the "simulation method") can calculate physical quantities acting along the tire surface using a computer device.

[0011] Fig. 1 is a perspective view of a computer 1 for executing the simulation method of this embodiment. As shown in Fig. 1, 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 a central processing unit (CPU), ROM, working memory, storage devices such as magnetic disks, and disk drive devices 1a1 and 1a2. The storage device stores in advance a processing procedure (program) for executing the simulation method of this embodiment.

[0012] Fig. 2 is a flowchart showing an example of the processing procedure of the simulation method of this embodiment. As shown in Fig. 2, the simulation method of this embodiment includes a tire model input step S1 and a physical quantity calculation step S2. In the tire model input step S1, a tire model obtained by discretizing a tire to be analyzed into a finite number of elements is input to the computer 1. In the physical quantity calculation step S2, the computer 1 calculates the physical quantities of each element when the tire model is deformed. Each of these steps will be described in detail below.

[0013] [Tire model input step] Fig. 3 is a flowchart showing an example of the processing procedure of the tire model input step S1. As shown in Fig. 3, in the tire model input step S1, first, a tire model without film elements on its surface (hereinafter referred to as "first tire model") is defined (S11). This first tire model may be newly created, or a previously created one may be used.

[0014] FIG. 4 is a cross-sectional view visualizing such a first tire model 2. As shown in FIG. 4, the first tire model 2 is configured by discretizing the tire to be analyzed into a finite number of elements F(i) (i = 1, 2, ...) that can be handled by a numerical analysis method. Examples of the numerical analysis method that can be used include the finite element method, the finite volume method, the difference method, and the boundary element method. In this embodiment, the finite element method is used. Numerical data such as element number, node number, node coordinate values ​​in the global coordinate system XYZ, and material properties (e.g., density, Young's modulus, and / or damping coefficient) are defined for each element F(i) and stored in the computer 1. In this embodiment, the surfaces of the first tire model 2 (e.g., the surfaces of the tread portion 3, the sidewall portion 4, and the bead portion 5) are configured with three-dimensional solid elements to simulate rubber.

[0015] In the first tire model 2 of this embodiment, the entire tire is modeled based on the shape of the tire to be analyzed. In another aspect, the first tire model 2 may be a partial tire model in which only a portion of the tire, for example, a portion in the tire circumferential direction, is modeled. Even with such a partial model, predetermined physical quantities can be calculated from it.

[0016] Next, in the tire model input step S1, the first surface 6 of the three-dimensional element F(i) is specified as the portion for which surface strain, surface stress, etc. are to be analyzed (S12), as shown in Fig. 3. This step S12 can be performed by the user by appropriately specifying the portion to be analyzed.

[0017] FIG. 5 is a partial perspective view of the first tire model 2. For example, if a user wants to calculate physical quantities such as stress and strain acting on the surface of the sidewall portion 4 of the tire, the first surface 6 is defined as a predetermined outer surface of the sidewall portion 4 of the first tire model 2. For ease of understanding, in FIG. 5, the first surface 6 is represented as a white portion of the first tire model 2. In this example, the first surface 6 is the outer surface of a plurality of three-dimensional solid elements arranged on the sidewall portion 4 of the first tire model 2. In other examples, the first surface 6 may be continuous in the tire circumferential direction, or conversely, may be a single surface. Furthermore, any surface can be identified as the first surface 6 as long as it is the outer surface of a three-dimensional element F(i) arranged on the surface of the first tire model 2. The element number and other information of the identified first surface 6 are stored in the computer 1.

[0018] Next, as shown in FIG. 3, in the tire model input step S1 of this embodiment, membrane elements are arranged on the first surface 6 to form a composite surface portion 7 (S13). FIG. 5 visualizes such membrane elements G(i) (i = 1, 2, ...). For ease of understanding, the membrane elements G(i) are separated from the first surface 6. Numerical data such as element number, node number, node coordinate values ​​in the global coordinate system XYZ, and material properties (e.g., density, Young's modulus and / or damping coefficient) are defined for each membrane element G(i) and stored in the computer 1. The material properties of the membrane element G(i) are defined to be the same as those of the three-dimensional element F(i) having the first surface 6.

[0019] Furthermore, the membrane element G(i) of this embodiment has a thickness so thin that stress in the thickness direction can be ignored. That is, the membrane element G(i) of this embodiment is formed with a thickness such that only in-plane tensile stress or compressive stress acts on it, and shear force or bending force does not substantially act on it. From this viewpoint, the thickness of the membrane element G(i) may be, for example, 0.001 mm or less.

[0020] FIG. 6 is a perspective view visualizing each of the three-dimensional elements F(i) and the membrane elements G(i). As shown in FIG. 6, the membrane elements G(i) of this embodiment are arranged on the first surface 6 so that each node 8 of the first surface 6 of the three-dimensional element F(i) and each node 9 of the membrane element G(i) are shared. This allows the membrane elements G(i) to deform together with the first surface 6 of the three-dimensional element F(i) when the tire model deforms. In other words, the stress and strain acting on the first surface 6 of the three-dimensional element F(i) can be obtained as the in-plane stress and in-plane strain of the membrane elements G(i).

[0021] In another embodiment, when a boundary condition is set that prohibits relative movement between the first surface 6 of the three-dimensional element F(i) and the membrane element G(i), the membrane element G(i) and the first surface 6 do not have to be shared with each other.

[0022] Through the above processing, as shown in Figure 5, a membrane element G(i) is placed on the first surface 6 of the three-dimensional element F(i) to define a composite surface portion 7, and a second tire model 2A including the composite surface portion 7 is created.

[0023] In this embodiment, an example has been shown in which the composite surface portion 7 is formed on the sidewall portion 4 of the tire, but in other embodiments, the composite surface portion 7 may form the surface of the bead portion 5 and / or the tread portion 3. Furthermore, when the composite surface portion 7 is formed on the surface of the tread portion 3, the composite surface portion 7 may be formed on the surface of the grooves 10 and / or sipes 11 in the tread portion 3, which are prone to cracks and the like.

[0024] [Physical quantity calculation step] In the physical quantity calculation step S2, the second tire model 2A is deformed under predetermined conditions, and predetermined physical quantities are calculated from each element. Fig. 7 is a flowchart showing an example of the processing procedure of the physical quantity calculation step S2 of this embodiment. As shown in Fig. 7, in the physical quantity calculation step S2 of this embodiment, first, the deformation of the second tire model 2A is calculated (S21).

[0025] In step S21 of this embodiment, the computer 1 executes a calculation to deform the second tire model 2A under predetermined conditions. The predetermined conditions include, for example, an internal pressure condition, a load condition, or a rolling condition of the second tire model 2A, and the deformation calculation of the second tire model 2A is performed according to one or more of these conditions.

[0026] When an internal pressure condition is given, as shown in FIG. 8(a), a uniformly distributed load w equivalent to the internal pressure is applied to the inner cavity surface of the second tire model 2A. This makes it possible to calculate the deformation state of the second tire model 2B when the tire is inflated and deformed. When a load condition is given, as shown in FIG. 8(b), the second tire model 2B is brought into contact with a road surface model 12 defined by a rigid surface, and then a vertical load P is applied to the rotation axis of the second tire model 2B. This makes it possible to calculate the deformation state of the second tire model 2C when the second tire model 2C receives a certain vertical load P and comes into contact with the road surface. When a rolling condition is given, for example, after the load condition of FIG. 8(b) is given, an angular velocity ω is defined for the rotation axis of the second tire model 2C as shown in FIG. 8(c). This makes it possible to calculate the deformation state of the second tire model 2D rolling on the road surface model 12.

[0027] The deformation calculation of the second tire model 2D can be performed using commercially available finite element analysis application software such as ABAQUS by Dassault Systèmes. The unit time T(x) for the calculation can be set appropriately depending on the required simulation accuracy. This software can automatically calculate the maximum principal strain and maximum principal stress of each element.

[0028] Next, in the physical quantity calculation step S2 of this embodiment, the maximum principal strain and maximum principal stress of the membrane element G(i) of the deformed second tire model 2D are calculated (S22, S23) as shown in Fig. 7. The maximum principal strain and maximum principal stress of the membrane element G(i) can be calculated by the computer 1 based on the nodal coordinate positions of the membrane element G(i) before and after deformation. The calculated maximum principal strain and maximum principal stress of the membrane element G(i) are stored in the computer 1.

[0029] The membrane elements G(i) of the composite surface portion 7 of this embodiment have a small thickness such that stress in the thickness direction is negligible, and therefore only in-plane stress occurs in the membrane elements G(i). Therefore, the maximum principal strain and maximum principal stress of the membrane elements G(i) can be automatically calculated by finite element analysis application software. Furthermore, because the membrane elements G(i) deform together with the first surfaces 6 of the three-dimensional elements F(i), the maximum principal strain and maximum principal stress of the membrane elements G(i) are equal to the maximum surface stress and surface strain acting on the first surfaces 6 of the three-dimensional elements F(i). Therefore, the simulation method of this embodiment makes it possible to easily calculate the physical quantities acting along the surfaces (i.e., the first surfaces 6) of the three-dimensional elements F(i) arranged on the tire surface.

[0030] Next, in the physical quantity calculation step S2 of this embodiment, the maximum principal strain and maximum principal stress of the membrane element G(i) are displayed (S24). In this embodiment, the maximum principal strain and maximum principal stress of the membrane element G(i) are displayed on the display device 1d as a maximum principal strain vector and a maximum principal stress vector, respectively. This visualizes the magnitude and direction of the maximum principal strain and maximum stress (physical quantities) acting along the tire surface, making it possible to easily evaluate the damage resistance and crack resistance of the tire surface.

[0031] Next, the computer 1 determines whether a predetermined end time has elapsed (S25). In step S25, if the computer 1 determines that the end time has elapsed, it terminates the physical quantity calculation step S2. On the other hand, if it determines that the end time has not elapsed, it advances the unit time T(x) by one (S26) and performs steps S21 to S24 again. This enables the computer 1 to calculate the physical quantities (maximum principal strain and / or maximum principal stress) acting along the tire surface from the start to the end of rolling and store them as time-series data for each unit time T(x). The end time is determined appropriately depending on the simulation to be executed.

[0032] While the present invention has been described above in detail with respect to a particularly preferred embodiment thereof, the present invention is not limited to the illustrated embodiment and can be practiced in various modified forms. In the above embodiment, a tire simulation method has been described, but various articles and structures other than tires may also be used as the object of simulation. [Example]

[0033] Examples for confirming the effects of the present invention will be described below. [Example 1, Comparative Example 1] First, in Example 1 and Comparative Example 1, the groove bottom of the tread portion was identified as the tire surface location to be analyzed. In Example 1, a membrane element was placed on the surface (first surface) of the identified groove bottom to define a composite surface portion, and the maximum principal strain of the membrane element was calculated. The thickness of the membrane element was set to 0.001 mm. In Comparative Example 1, no membrane element was placed, and the maximum principal strain of the three-dimensional element forming the surface of the groove bottom was calculated. Then, for Example 1 and Comparative Example 1, the calculation time of the maximum principal strain acting along the tire surface was evaluated. The test results are shown in Table 1.

[0034] [Table 1]

[0035] As shown in Table 1, the time required to display (calculate) the maximum principal strain of the three-dimensional element in Comparative Example 1 was 5 minutes. However, in Comparative Example 1, the user had to check whether the maximum principal strain of the three-dimensional element was aligned with the tire surface. Furthermore, if the maximum principal strain of the three-dimensional element was not aligned with the tire surface, it was necessary to calculate the maximum principal strain acting on the surface of the groove bottom from the change in the nodal coordinates of the three-dimensional element before and after deformation. The time required for these checks and calculations was 15 minutes. Thus, in Comparative Example 1, the calculation time for the maximum principal strain acting along the surface of the groove bottom was 20 minutes. On the other hand, in Example 1, the calculation time was 5 minutes because the maximum principal strain acting along the surface of the groove bottom was calculated as the maximum principal strain of the membrane element. Therefore, Example 1 was able to calculate the physical quantity acting along the tire surface more easily than Comparative Example 1.

[0036] [Example 2, Comparative Example 2] FIG. 9 is a partial perspective view of a tire simulation model including the analysis target portion of Example 2 and Comparative Example 2. As shown in FIG. 9, in Example 2 and Comparative Example 2, a design portion 13 formed in a bead portion of a pneumatic tire was identified as the analysis target. This design portion 13 includes a plurality of first ribs 14 extending in the tire radial direction and a second rib 15 extending in a zigzag pattern in the tire circumferential direction, and the area surrounded by each rib 14, 15 is defined as a recess 16. In Example 2, a membrane element (not shown) was arranged on the surface of this design portion 13 to define a composite surface portion. In Comparative Example 2, no membrane element was arranged on the design portion 13, and the maximum principal stress of the three-dimensional element forming the analysis target portion was calculated. Then, for Example 2 and Comparative Example 2, the maximum principal stress acting along the surface of the design portion 13 was calculated.

[0037] 10 and 11 are contour diagrams showing the maximum principal stress (tensile) vector acting on the surface of part X in Fig. 9 as calculation results for Example 2 and Comparative Example 2, respectively. The reason for examining the maximum principal stress (tensile) is that it is considered to be a physical quantity that has a large effect on surface cracks in the bead portion.

[0038] Generally, when a pneumatic tire is loaded, the bead portion on the contact surface side is compressed in the tire radial direction, and strain that expands in the tire axial direction can occur due to the Poisson effect. Such strain generates compressive stress (not shown) in the recess 16 of the design portion 13. Consistent with this theory, the calculation results of Example 2 in Figure 10 confirm that the maximum principal stress (tensile) vector is almost absent in the recess 16 of the design portion 13.

[0039] On the other hand, as shown in Figure 11, in Comparative Example 2, the principal stress of the three-dimensional elements on the surface of the bead portion was evaluated, and therefore the maximum principal stress (tensile) vector was displayed for both the ribs 14, 15 and the recess 16, and it was found that the surface stress of the recess in the design portion 13 could not be evaluated as it was.

[0040] [Note] The present invention includes the following aspects.

[0041] [Invention 1] 1. A tire simulation method, comprising: a step of inputting a tire model obtained by discretizing the tire into a finite number of elements into a computer; and a step by the computer calculating a physical quantity of the element when the tire model is deformed under a predetermined condition, the tire model includes, as the elements, a composite surface portion including a three-dimensional element having a first surface corresponding to the surface of the tire and a membrane element disposed on the first surface; the membrane element deforms together with the first surface and has a small thickness such that stress in the thickness direction is negligible; How to simulate tires. [Invention 2] A tire simulation method according to claim 1, wherein the thickness of the membrane element is 0.001 mm or less. [Invention 3] 3. The tire simulation method according to claim 1 or 2, wherein the physical quantity includes a maximum principal strain and / or a maximum principal stress of the membrane element. [Invention 4] 4. The tire simulation method according to any one of claims 1 to 3, wherein the conditions include an internal pressure condition, a load condition, or a rolling condition of the tire model. [Invention 5] 5. The tire simulation method according to any one of claims 1 to 4, wherein the composite surface portion constitutes the surface of a tread portion, a sidewall portion and / or a bead portion of the tire. [Invention 6] 6. A tire simulation method according to any one of claims 1 to 5, wherein the composite surface portion constitutes the surface of a groove and / or a sipe formed in a tread portion of the tire. [Invention 7] A method for creating a tire model in which a tire is discretized into a finite number of elements, comprising: identifying a three-dimensional element having a first surface corresponding to a surface of the tire; forming a composite surface portion by disposing, on the first surface, a membrane element that deforms together with the first surface and has a small thickness such that stress in the thickness direction is negligible; How to create a tire model, including: [Explanation of symbols]

[0042] 2A Tire Model 3 Tread section 4 Sidewall 5 Bead section 6 Front page 7 Composite surface section 8 nodes 9 nodes 10 grooves 11 Sipe F(i) 3D element G(i) Membrane element

Claims

1. 1. A tire simulation method, comprising: a step of inputting a tire model obtained by discretizing the tire into a finite number of elements into a computer; and a step by the computer calculating a physical quantity of the element when the tire model is deformed under a predetermined condition, the tire model includes, as the elements, a composite surface portion including a three-dimensional element having a first surface corresponding to a surface of the tire and a membrane element disposed on the first surface; the membrane element is deformed together with the first surface and has a small thickness such that stress in the thickness direction is negligible; How to simulate tires.

2. 2. The tire simulation method according to claim 1, wherein the thickness of the membrane element is 0.001 mm or less.

3. The tire simulation method according to claim 1 , wherein the physical quantity includes a maximum principal strain and / or a maximum principal stress of the membrane element.

4. The tire simulation method according to claim 1 , wherein the conditions include an internal pressure condition, a load condition, or a rolling condition of the tire model.

5. 5. The tire simulation method according to claim 1, wherein the composite surface portion constitutes the surface of a tread portion, a sidewall portion, and / or a bead portion of the tire.

6. The tire simulation method according to claim 1 , wherein the composite surface portion constitutes a surface of a groove and / or a sipe formed in a tread portion of the tire.

7. A method for creating a tire model in which a tire is discretized into a finite number of elements, comprising: identifying a three-dimensional element having a first surface corresponding to a surface of the tire; forming a composite surface portion by disposing, on the first surface, a membrane element that deforms together with the first surface and has a thickness that is small enough that stress in the thickness direction is negligible; How to create a tire model, including:

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