JP7401355B2 - Tire simulation method, device and program - Google Patents

Description

The present invention relates to a tire simulation method, an apparatus, and a program for reproducing the behavior of a tire running on a snowy road surface.

It is now possible to predict tire performance through simulation by analyzing the load applied to the rigid road surface and rolling motion of the tire. For road surfaces covered with snow, that is, snow road surfaces, prediction of tire performance using such simulations has been proposed (see Patent Documents 1 and 2).

The method described in Patent Document 1 incorporates a step of stratifying the snow model in advance in order to improve the prediction accuracy of tire performance on snowy roads, taking into account that snow is compacted by tire surface pressure. I'm here. In the step of stratifying, a tomographic image of the snow by an internal three-dimensional image analyzer and three-dimensional information as a processing result of the tomographic image are used as the microscopic structure of the snow. However, such a stratification method using tomographic images requires very high equipment and measurement costs.

Patent No. 5808744 Japanese Patent Application Publication No. 2019-040559

In view of the above points, the embodiments of the present invention have an object to provide a tire simulation method, an apparatus therefor, and a program thereof, which can improve the prediction accuracy of tire performance on snowy road surfaces using a cheaper method. do.

A first aspect of the present invention is a tire simulation method for reproducing the behavior of a tire running on a snowy road surface, which includes the step of setting a tire model modeled with a finite number of elements that can be numerically analyzed; The dynamic analysis includes the steps of: setting an Eulerian element model including a snow model as an analysis model in which snow is placed; and performing a dynamic analysis by rolling the tire model on the snow model. The steps include calculating the deformation of the tire model and the snow model, calculating the snow density distribution in the snow model from the results of the deformation calculation, and calculating the snow density distribution according to the snow density from the obtained density distribution. This tire simulation method includes the steps of setting plastic properties in a snow model, and calculating deformation of the tire model and the snow model using the snow model having the set elastic-plastic properties.

A second aspect of the present invention is a tire simulation device that reproduces the behavior of a tire running on a snowy road surface, the tire model setting unit that sets a tire model modeled with a finite number of elements that can be numerically analyzed. an Eulerian element model setting for setting an Eulerian element model including a snow model as an analysis model with snow placed inside; and a dynamic analysis section for performing a dynamic analysis by rolling the tire model on the snow model. , the dynamic analysis unit calculates the deformation of the tire model and the snow model, calculates the snow density distribution in the snow model from the result of the deformation calculation, and calculates the snow density from the obtained density distribution. A tire simulation device characterized in that the snow model is set with elastic-plastic characteristics corresponding to the above-mentioned snow model, and deformation calculations of the tire model and the snow model are performed using the snow model having the set elastic-plastic characteristics. It is.

A third aspect of the present invention is a program for reproducing the behavior of a tire running on a snowy road surface, the tire model setting a tire model modeled with a finite number of elements that can be numerically analyzed in a computer. a setting function, an Euler element model setting function that sets an Euler element model including a snow model as an analysis model with snow placed inside, and a dynamic analysis function that performs dynamic analysis by rolling the tire model on the snow model. The analysis function calculates the deformation of the tire model and the snow model, calculates the snow density distribution in the snow model from the result of the deformation calculation, and calculates the elastic-plasticity according to the snow density from the obtained density distribution. A tire simulation program for realizing a dynamic analysis function that sets properties to the snow model and calculates deformation of the tire model and the snow model using the snow model having the set elastic-plastic properties. be.

The first to third aspects described above may further include a step, a static analysis section, or a static analysis function of performing a static analysis in which the tire model is brought into contact with the snow model without rolling. When performing the static analysis, the deformation of the tire model and the snow model is calculated, the snow density distribution in the snow model is calculated from the result of the deformation calculation, and the density distribution is calculated according to the snow density from the obtained density distribution. Elastoplastic characteristics may be set in the snow model, and deformation calculations of the tire model and the snow model may be performed using the snow model having the set elastic-plastic characteristics.

In the first to third aspects described above, the elastic-plastic properties may include at least one selected from the group consisting of Young's modulus, adhesive force, and friction angle.

According to an embodiment of the present invention, the density distribution of deformed snow is determined while performing dynamic analysis, and elastic-plastic properties are given to the snow model according to the density of the snow, and deformation calculations of the tire model and the snow model are performed. Therefore, it is possible to improve the reproducibility of the actual phenomenon of a snowy road surface, which is compacted by tire surface pressure, etc., using a cheaper method, and it is possible to improve the prediction accuracy of tire performance on a snowy road surface.

FIG. 1 is a block diagram of a simulation device according to an embodiment. It is a flowchart of the same simulation device. It is a flowchart of a static analysis part and a dynamic analysis part. FIG. 2 is a perspective view showing a state in which a tire model and an Euler element model are combined. FIG. 3 is a schematic cross-sectional diagram showing the density distribution of snow when a tire is brought into contact with snow. It is a graph showing the relationship between snow density and Young's modulus. It is a graph showing the relationship between vertical stress and shear stress of snow. (A) is a perspective view showing the state before the tire model is brought into contact with the snow model, and (B) is a perspective view showing the state after it is brought into contact with the snow model.

Embodiments of the present invention will be described below based on the drawings.

A tire simulation device 10 according to one embodiment is a simulation device that reproduces the behavior of a pneumatic tire running on a snowy road surface, and as shown in FIG. It has a setting section 16, an Euler element model setting section 18, a static analysis section 20, a dynamic analysis section 22, an evaluation value acquisition section 24, a tire performance prediction section 26, and an output section 28.

This simulation device 10 can also be realized using, for example, a general-purpose computer having a mouse and a keyboard as the basic hardware. That is, the input section 12, the tire model setting section 14, the road surface model setting section 16, the Euler element model setting section 18, the static analysis section 20, the dynamic analysis section 22, the evaluation value acquisition section 24, the tire performance prediction section 26, and The output unit 28 can be realized by causing a processor installed in the computer described above to execute a program. At this time, the simulation device 10 may be realized by pre-installing the above program on a computer, storing the above program in a storage medium such as a CD-ROM, or distributing the above program via a network. This may be realized by appropriately installing this program on a computer.

Hereinafter, the configuration and functions of each of the above sections will be explained in order.

[1] Input section 12
The input unit 12 acquires model creation conditions necessary for modeling the pneumatic tires and snowy road surfaces to be analyzed, and analysis conditions for performing analysis using these models.

Model creation conditions include model shape, mesh division number, etc.For example, tire model creation conditions include various data about tires (tire design information) including tire cross-sectional shape, and specific Specifically, various dimensional specifications such as the external shape and internal structure of the tire, and material properties such as Young's modulus, Poisson's ratio, and specific gravity of each member such as the tread, belt, and carcass that constitute the tire are input.

The conditions for creating the Euler element model include the size of the model according to the size of the tire model, the number of mesh divisions, the area where the mesh is subdivided and the degree of subdivision, the quality of snow on the road surface, the thickness and density of snow, Examples include the thickness of one mesh of snow.

The analysis conditions include the internal pressure and load on the tire model attached to the rim model, the translational speed that determines the dynamic state of the tire model (i.e., the running speed of the tire model), and the conditions related to the movement and ground contact of the tire model, such as the slip angle. In addition, the analysis time for dynamic analysis is input.

This information may be entered using a keyboard, or via a recording medium such as a CD-ROM, a network, or the like.

[2] Tire model setting section 14
The tire model setting unit 14 sets a tire model modeled using a finite number of elements that can be numerically analyzed. For example, a finite element model is created for a tire having a tread pattern based on the model creation conditions input through the input unit 12.

Specifically, a tire shape in a natural equilibrium state is used as a reference shape, and this reference shape is modeled by FEM to create a three-dimensional tire model divided into a large number of finite elements by mesh division. Such elements include tetrahedral solid elements, pentahedral solid elements, hexahedral solid elements, and the like, and these elements are identified one by one using three-dimensional coordinates. An example of a patterned tire model is shown as 50 in FIG.

The method of creating such a tire model itself is well known, and the tire can be modeled using such a well-known method. Note that a tire model created in advance may be input from the input unit 12, and in that case, the tire model setting unit 14 sets the input tire model as an analysis target.

[3] Road surface model setting section 16
The road surface model setting unit 16 sets a road surface model that reproduces the road surface. Specifically, based on the model creation conditions input through the input unit 12, a road surface model is created in which the road surface is replaced with elements that can be numerically analyzed.

The road surface model may be constructed of flat rectangular rigid surface elements that do not deform even when external forces are applied, as shown by reference numeral 52 in FIG. You may. In the road surface model, for example, a surface friction coefficient substantially similar to that of an asphalt road surface is defined as a boundary condition.

In this embodiment, in order to reproduce the behavior of a tire running on a snowy road surface, the tire model runs on a snow model of an Euler element model. Therefore, if the bottom surface of the Euler element model is fixed as a rigid surface, the road surface model is not essential and may be omitted.

Note that a road surface model created in advance may be input from the input section 12, and in that case, the road surface model setting section 16 sets the input road surface model as an analysis target. Alternatively, one or more road surface models may be stored in advance in a storage means such as a hard disk, and the road surface model selected via a mouse, keyboard, etc. may be set as an analysis target.

[4] Euler element model setting section 18
The Euler element model setting unit 18 creates an Euler element model including a snow model as an analytical model in which snow is arranged, based on the model creation conditions input by the input unit 12.

The Eulerian element model, an example of which is shown by reference numeral 54 in FIG. It has a rectangular parallelepiped shape.

The Euler element model 54 may be provided over the entire movement range of the tire model 50 in the dynamic analysis, but in this example, the Euler element model 54 is moved in accordance with the movement of the rolling tire model 50 in the dynamic analysis. , the Euler element model 54 is created in a range including the overlapping part with the tire model 50 and the vicinity thereof.

The Euler element model 54 is divided into a plurality of rectangular parallelepiped elements by a plurality of vertical planes parallel to the tire axial direction, a plurality of vertical planes parallel to the tire longitudinal direction, and a plurality of horizontal planes having different heights. In the example shown in FIG. 4, the rectangular parallelepiped element is generated so that its volume increases as it moves away from the lower surface of the Euler element model 54 in the height direction, which is arranged in contact with the road surface model 52. In addition, the Euler element model 54 has elements that are subdivided in areas that overlap with the tire model 50, that is, the area corresponding to the ground contact part of the tire model 50 and its vicinity is meshed more densely than the surrounding area. It is set.

A snow model 56 is constructed by disposing snow at a predetermined height inside the Euler element model 54. In the Euler element model 54, an object such as snow moves in space without changing the shape of the element. In the Euler element model 54, a spatial region made of air is secured above the snow model 56 in which snow is arranged.

The snow placed inside the Eulerian element model 54 is placed with a uniform thickness (height) over the entire lower surface area of the Eulerian element model 54 that is in contact with the road surface model 52, and in the example of FIG. The snow (shown in gray in FIG. 4) is filled up to the position of the fourth element, that is, to a thickness of four mesh layers.

The number of mesh layers of the snow model 56 can be determined by dividing the thickness of snow on the snowy road surface to be simulated by the thickness of one mesh of the snow model 56. It is preferable that the thickness of one mesh of the snow model 56 is smaller (thinner) than the thickness of one mesh of the tread of the tire model 50 that contacts the snow model 56, so that snow can be seen on the tire model surface in dynamic analysis and static analysis. It is possible to avoid erroneous calculations that would penetrate the mesh.

The snow model 56 is an elasto-plastic model (for example, a modified Drucker-Prager/Cap plastic model), and includes density, elasto-plastic properties (elastic properties such as Young's modulus and Poisson's ratio, plastic properties such as adhesion force and friction angle), etc. Characterized by

In this embodiment, as the Eulerian element model 54 (in particular, the snow model 56), one whose elastic-plastic properties change depending on the density of snow is used. That is, for each element in the snow model 56 of the Euler element model 54, a value is set as the elastic-plastic property of snow according to the density of the element, and as the density changes, the elastic-plastic property is imparted accordingly. It is composed of In dynamic analysis and static analysis, the reproducibility of actual phenomena can be further improved by setting elastic-plastic characteristics in the Euler element model 54 according to the density distribution of deformed snow.

This point will be explained in detail. There is a correlation between snow density and elastoplastic properties. For example, it is known that there is an approximate exponential relationship between snow density and Young's modulus (S. Shoop, K. Kestler, and R. Haehnel, Finite Element Modeling of Tireson Snow. Science and Technology, TSTCA, Vol.34, No.1, January - March2006, pp.2-37). Furthermore, there is a linear approximate relationship between the adhesive force and friction angle, which are plastic properties, and the density. In general, changes in snow density are related to changes in snow quality (Toshio Oda, Kiyoshi Kudo, Snow Quality and Density, Nisetsu Monthly Report 2, 1945, pp. 19-24, 43-45), and snow quality is related to changes in snow quality. The density increases as the snow undergoes isothermal transformation from fresh snow to compact snow to compact snow to rough snow (Katsutoshi Yano, Snow Coverage in Japan, Journal of the Japanese Society of Hydrology and Water Resources, Vol. 6, No. 2, 1993). .

When tires touch the snowy road surface, the surface pressure causes the snow to undergo isothermal transformation, changing the quality of the snow and increasing its density. FIG. 5 is a diagram schematically showing this point. On a snowy road surface where a tire is in contact with the ground, from the surface side near the tire toward the depth, there is a high density area where the density increase is the largest, a medium density area where the density increase is moderate, and a low density area where the density increase is small. , are formed in layers in this order. Further, the tread pattern has unevenness due to land portions and groove portions, and areas pressed by the land portions experience a greater increase in snow density than portions pressed by the groove portions, resulting in a density distribution.

Therefore, based on the density distribution in the snow model that deforms in dynamic analysis and static analysis, by giving the snow model 56 elastic-plastic properties according to the density, changes in snow quality due to snow deformation can be seen more realistically. can be reproduced in a state close to that of the previous model, and calculation accuracy can be improved.

In one embodiment, built-in functions such as the following equations (1) to (4) may be set as the relationship between snow density ρ and elastoplastic properties.

Young's modulus: E=αe ^βρ ...(1)
Poisson's ratio: v=0.3...(2)
Adhesion force: c=γρ+δ…(3)
Friction angle: φ=ερ+η…(4)
In the formula, α, β, γ, δ, ε, and η are material-specific values, and γ, δ, ε, and η vary depending on the tread rubber formulation.

As shown in equation (1), the Young's modulus E, which is an elastic property, has an exponential approximate relationship with the density ρ, and FIG. 6 shows an example of this. On the other hand, among the elastic properties, Poisson's ratio v is constant regardless of the density ρ, as shown in equation (2).

As shown in equations (3) and (4), there is a linear approximate relationship between the adhesive force c, which is a plastic characteristic, and the friction angle φ with the density ρ.

Here, the adhesion force c and the friction angle φ are values calculated using the relationship between normal stress (compressive stress) σ and shear stress τ, τ=c+σtanφ in the Mohr-Coulomb yield model. From the measurement results of a plurality of vertical stresses, it is calculated as the slope tanφ (friction angle φ), with the intercept being the adhesion force c. FIG. 7 shows an example of the relationship between normal stress σ and shear stress τ.

Table 1 below shows an example of the relationship between density ρ and elastic-plastic properties for four types of snow: fresh snow, compact snow, compact snow, and rough snow.

Note that the Euler element model described above may be created in advance and input from the input unit 12. In that case, the Euler element model setting unit 18 sets the input Euler element model as an analysis target. Alternatively, one or more Euler element models may be stored in advance in a storage means such as a hard disk, and the Euler element model selected via a mouse, keyboard, etc. may be set as an analysis target.

[5] Static analysis section 20
The static analysis unit 20 performs a static analysis in which the tire model 50 is brought into contact with the snow model 56 under a predetermined load or displacement without rolling. In this example, in the static analysis, the Euler element model 54 is combined with the road surface model 52 set above, and the tire model 50 is brought into contact with the snow model 56 of the Euler element model 54.

Specifically, the tire model 50 obtained by the tire model setting unit 14 is mounted on a rim model (not shown), and static analysis is performed using the finite element analysis method. That is, an internal pressure filling process is performed to calculate the deformation of the tire model 50 while filling the tire model 50 with a predetermined internal pressure, and while the tire model 50 is stationary without rolling, Euler elements on the road surface model 52 are filled. While the model 54, specifically the snow model 56, is in contact with the ground with a predetermined load or displacement, the deformation of the tire model 50 and the snow model 56 is calculated (i.e., the deformation calculation of the tire model 50 and the deformation of the snow in the Euler element model 54). Performs ground contact analysis processing (behavior calculation). Such static analysis itself can be performed by a static implicit method using a general-purpose analysis program, and examples of the general-purpose analysis program include Abaqus/Standard manufactured by Dassault Systèmes.

FIG. 8(A) shows a state before the tire model 50 is brought into contact with the snow model 56 of the Euler element model 54. From this state, the tire model 50 is brought into contact with the snow model 56 with a predetermined load or displacement. The grounded state is shown in 8(B). In this grounded state, the snow model 56 of the Euler element model 54 is deformed, and a portion of the tire model 50 enters the snow model 56. In addition, in FIG. 8, the tire model 50 is shown with the mesh omitted.

In one embodiment, the static analysis unit 20 includes a deformation calculation unit that calculates deformation of the tire model 50 and the snow model 56, and a density distribution calculation unit that calculates the density distribution of snow in the snow model 56 from the results of the deformation calculation. , an elasto-plastic property updating unit that sets, in the snow model 56, elasto-plastic properties according to the snow density from the obtained density distribution, that is, updates the elasto-plastic properties. In this manner, each time a static analysis deformation calculation is performed, the deformation calculation is performed while updating the elastoplastic properties according to the density distribution obtained as a result, until the ground contact is made with a predetermined load or displacement.

[6] Dynamic analysis section 22
The dynamic analysis unit 22 performs dynamic analysis by rolling the tire model 50 on the snow model 56. In this example, in a dynamic state in which the tire model 50 is rolled on the snow model 56 and the Euler element model 54 is moved on the road surface model 52 in accordance with the movement of the rolling tire model 50, the tire model 50 and Dynamic analysis (more specifically, traction analysis) is performed to calculate the deformation of the snow model 56 (that is, calculate the deformation of the tire model 50 and calculate the behavior of snow in the Euler element model 54).

The dynamic analysis unit 22 causes the tire model 50 to roll (that is, rotate) so as to translate forward, that is, in the direction indicated by arrow D1 in FIG. 4 at a predetermined acceleration, and as the tire model 50 moves, A dynamic analysis is performed in which the above deformation calculation is performed while moving the Euler element model 54 forward with the same acceleration. In this case, the tire model 50 and the Euler element model 54 may be moved at a predetermined acceleration from a stationary state to a final velocity (target translational velocity) during the analysis time input by the input unit 12, or , the desired dynamic state may be achieved by instantaneously inputting the target translation speed.

The dynamic analysis itself can be performed by the method described in Patent Document 2, or by a dynamic explicit method using a general-purpose analysis program. Examples of the general-purpose analysis program include Abaqus/Explicit manufactured by Dassault Systèmes. It will be done. More specifically, the analysis can be carried out using Eulerian-Lagrangian (CEL) analysis using Abaqus/Explicit, in which the tire model is a Lagrangian element and the air/snow model is an Eulerian element.

In this embodiment, the dynamic analysis unit 22 includes a deformation calculation unit that calculates the deformation of the tire model 50 and the snow model 56, and a density distribution calculation unit that calculates the snow density distribution in the snow model 56 from the results of the deformation calculation. , an elasto-plastic property updating unit that sets, in the snow model 56, elasto-plastic properties according to the snow density from the obtained density distribution, that is, updates the elasto-plastic properties. Each time the deformation calculation is performed in this way, the deformation calculation is performed until a predetermined analysis time is reached while updating the elastic-plastic properties according to the density distribution obtained as a result.

[7] Evaluation value acquisition unit 24
The evaluation value acquisition unit 24 acquires an evaluation value for evaluating tire performance on a snowy road surface, for example, traction performance, from the above dynamic analysis. For example, the contact shape, contact area, ground pressure distribution, etc. of the tire model 50 with respect to the Euler element model 54; the snow volume content, reaction force, etc. included in each element of the Euler element model 54; the axial force of the tire model 50, etc. Obtain as evaluation value.

[8] Tire performance prediction unit 26
The tire performance prediction unit 26 predicts traction performance on a snowy road surface based on the evaluation value obtained by the evaluation value acquisition unit 24, and evaluates its quality.

[9] Output section 28
The output unit 28 outputs the tire performance prediction results obtained above. Output can be performed by displaying on a display or printing using a printer.

Next, the simulation method according to this embodiment will be explained based on the flowcharts of FIGS. 2 and 3.

In step S1, the tire model setting unit 14 creates a tire model 50 based on the model creation conditions input from the input unit 12. A tire model 50 created in advance may be input from the input unit 12, and the input tire model may be set as an analysis target. Then, the process advances to step S2.

In step S2, the road surface model setting section 16 creates the road surface model 52 based on the model creation conditions input from the input section 12. A road surface model 52 created in advance may be input from the input unit 12, and the input road surface model may be set as an analysis target. Then, the process advances to step S3.

In step S3, the Euler element model setting unit 18 creates the Euler element model 54 based on the model creation conditions input from the input unit 12. Specifically, the mesh generation unit creates an Eulerian element model 54 that divides the spatial region on the road surface using an Eulerian mesh of eight nodes. Next, the object placement unit places snow inside the Euler element model 54 to form a snow model 56. At this time, the snow density is set according to the snow quality to be analyzed, and elastic-plastic characteristics corresponding to the density are set for the entire snow model 56. Then, the process advances to step S4.

In step S4, the static analysis unit 20 performs a finite element analysis using the tire model 50 obtained in step S1, the road surface model 52 obtained in step S2, and the Euler element model 54 obtained in step S3. A static analysis is performed using the method, and the tire model 50 is brought into contact with the snow model 56.

Specifically, after the tire model 50 is mounted on a rim model (not shown), an internal pressure filling process is performed in which the tire model 50 is filled with a predetermined internal pressure and the deformation of the tire model 50 is calculated. Next, while the tire model 50 is in a stationary state without rolling and is brought into contact with the snow model 56 on the road surface model 52 until a predetermined load or displacement is reached, the deformation calculation of the tire model 50 and the snow model 56 ( That is, ground contact analysis processing is performed to calculate the deformation of the tire model 50 and to calculate the behavior of snow in the Euler element model 54.

In this example, each step shown in FIG. 3 is executed in the ground contact analysis process. The predetermined load or displacement applied to the tire model 50 is divided into a plurality of stages, and deformation calculations of the tire model 50 and the snow model 56 are performed at each stage until the predetermined load or displacement is reached.

In step S11, a first stage load or displacement is applied to the tire model 50, and deformation calculations of the tire model 50 and the snow model 56 are performed by a static implicit method using, for example, Abaqus/Standard.

Next, in step S12, the density distribution of snow in the snow model 56 is calculated from the result of the above deformation calculation. That is, the density of snow in each element of the deformed snow model 56 is calculated. Calculation of such density distribution can be performed using a general-purpose analysis program such as Abaqus/Standard.

Next, in step S13, elastic-plastic characteristics are set for each element of the snow model 56 according to the density of snow from the obtained density distribution. Specifically, in each element of the deformed snow model 56, the elastic-plastic properties of the snow corresponding to the snow density calculated above are determined. For example, the elastic-plastic properties corresponding to the snow density are determined from the built-in functions expressed by the above equations (1) to (4). Then, the snow model 56 is updated by replacing the elastic-plastic characteristics of each element of the snow model 56 with the elastic-plastic characteristics obtained in this way.

Next, in step S14, using the updated snow model 56, the next stage of load or displacement is applied to the tire model 50, and deformation calculations of the tire model 50 and the snow model 56 are performed by a static implicit method.

Then, in step S15, it is determined whether or not the predetermined load or displacement is applied to the tire model 50. If the predetermined load or displacement is not applied, the process returns to step S12, and the predetermined load or displacement is applied. Steps S12 to S15 are repeated until the If it is determined in step S15 that a predetermined load or displacement has been applied, the ground contact analysis process of the static analysis ends. Then, the process advances to step S5.

In step S5, the dynamic analysis unit 22 uses the tire model 50 in the ground contact state and the Euler element model 54 to perform a dynamic analysis (more specifically, traction analysis). In the dynamic analysis, the tire model 50 is rolled on the snow model 56 and the Euler element model 54 is moved on the road surface model 52 in accordance with the movement of the rolling tire model 50. Then, a deformation calculation of the snow model 56 (that is, a deformation calculation of the tire model 50 and a behavior calculation of the snow in the Euler element model 54) is performed.

In detail, deformation calculations of the tire model 50 are sequentially performed at predetermined time intervals based on the boundary conditions that the snow model 56 gives to the tire model 50, and the boundary conditions that the tire model 50 gives to the snow model 56. Based on this, snow behavior calculations are performed sequentially at predetermined time intervals. More specifically, first, the tire model 50 and the Euler element model 54 are moved in predetermined time steps, and the boundary surface between the tire model 50 and the snow model 56 is calculated. Next, the force acting on the tire model 50 from the snow model 56 is set as a boundary condition, and based on this, the deformation of the rolling tire model 50 is calculated, and the displacement and stress of the tire model 50 are calculated. On the other hand, velocity components accompanying deformation and rolling of the tire model 50 are set as boundary conditions for the snow model 56, and snow behavior calculations are performed based on this. Next, mapping processing of the physical quantities of snow within the Eulerian element model 54 is performed. The above steps are repeated until a predetermined analysis time has elapsed, and when the predetermined analysis time has elapsed, the dynamic analysis is completed.

In this embodiment, in this dynamic analysis, each step shown in FIG. 3 is performed similarly to the static analysis described above. In the dynamic analysis, in step S11, deformation calculations of the tire model 50 and the snow model 56 during movement of the tire model 50 at the predetermined time interval are performed by a dynamic explicit method using, for example, Abaqus/Explicit. Next, in step S12, the snow density distribution in the snow model 56, that is, the snow density in each element is calculated from the result of the deformation calculation using a general-purpose analysis program such as Abaqus/Explicit. Next, in step S13, from the obtained density distribution, the elastic-plastic properties according to the snow density for each element of the snow model 56 are determined from the built-in functions expressed by the above formulas (1) to (4), for example. The snow model 56 is updated by setting the obtained elastic-plastic properties to each element of the snow model 56. Next, in step S14, using the updated snow model 56, a dynamic explicit method is used to calculate the deformation of the tire model 50 and the snow model 56 when the tire model 50 moves at the next step size. Then, in step S15, it is determined whether or not a predetermined analysis time has elapsed, and if the predetermined analysis time has not elapsed, the process returns to step S12, and steps S12 to S15 are repeated until the predetermined analysis time has elapsed. . In step S15, if it is determined that the predetermined analysis time has elapsed, the dynamic analysis is ended.

After the dynamic analysis is completed in this manner, in step S6, the evaluation value acquisition unit 24 acquires an evaluation value for evaluating tire performance on a snowy road surface from the result of the dynamic analysis. Then, the process advances to step S7.

In step S7, the tire performance prediction unit 26 predicts whether the tire performance on a snowy road surface is good or bad based on the evaluation value obtained in step S6, and the output unit 28 outputs the result.

[Action/Effect]
In this embodiment, the density distribution of deformed snow is determined while performing static analysis and dynamic analysis, and elastic-plastic properties are given to the snow model according to the snow density to calculate the deformation of the tire model and snow model. conduct. That is, by utilizing the fact that there is a correlation between snow density and elastoplastic properties, the snow model is given elastoplastic properties according to the density distribution of snow obtained through analysis. Therefore, it is possible to simulate the actual phenomenon of a snowy road surface, where density distribution occurs due to compaction due to tire surface pressure, etc., without having to stratify the snow model in advance using tomographic images as in the conventional method. can. Therefore, although it is a cheaper method, it is possible to improve the reproducibility of actual phenomena and improve the prediction accuracy of tire performance on snowy road surfaces.

In addition, regarding the difference in snow density caused by unevenness of the tread pattern, it is possible to calculate the deformation of the tire model and snow model by adding elastic-plastic properties according to the density difference, so during traction on snowy roads, The sipes and lateral grooves on the tread surface can bite snow more firmly, and the contribution of the tread pattern can be predicted with high accuracy.

[Other embodiments]
In the above embodiment, in the dynamic analysis, the Euler element model 54 is moved in accordance with the movement of the tire model 50, but the tire model 50 may be moved without moving the Euler element model 54. .

In the above embodiment, in the static analysis, the elastic-plastic properties of the snow model 56 are updated according to the flowchart shown in FIG. 3, but in the static analysis, the elastic-plastic properties are not updated according to the density distribution. Ground contact analysis processing may be performed while keeping the plastic properties constant.

In the above embodiment, prior to the dynamic analysis, a static analysis was performed in which the tire model 50 was brought into contact with the snow model 56 without rolling, but the dynamic analysis was performed without performing the static analysis. May be implemented.

Although several embodiments have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and gist of the invention, as well as within the scope of the invention described in the claims and its equivalents.

DESCRIPTION OF SYMBOLS 10... Simulation device, 14... Tire model setting part, 16... Road surface model setting part, 18... Eulerian element model setting part, 22... Dynamic analysis part, 50... Tire model, 54... Eulerian element model, 56... Snow model

Claims (5)

A tire simulation method that reproduces the behavior of a tire running on a snowy road surface,
a step of setting a tire model modeled with a finite number of elements that can be numerically analyzed;
a step of setting an Eulerian element model including a snow model as an analysis model with snow placed inside;
performing a dynamic analysis by rolling the tire model on the snow model;
including;
The step of performing the dynamic analysis includes a step of calculating the deformation of the tire model and the snow model, a step of calculating the snow density distribution in the snow model from the result of the deformation calculation, and a step of calculating the snow density distribution from the obtained density distribution. the snow model, and the step of calculating the deformation of the tire model and the snow model using the snow model having the set elastic-plastic properties.
How to simulate tires. further comprising the step of performing a static analysis in which the tire model is brought into contact with the snow model without rolling;
The step of performing the static analysis includes a step of calculating the deformation of the tire model and the snow model, a step of calculating the snow density distribution in the snow model from the result of the deformation calculation, and a step of calculating the snow density distribution from the obtained density distribution. The method further comprises the steps of: setting elastic-plastic properties in the snow model according to the density of the snow model; and calculating deformation of the tire model and the snow model using the snow model having the set elastic-plastic properties. The simulation method according to item 1. The simulation method according to claim 1 or 2, wherein the elastoplastic property includes at least one selected from the group consisting of Young's modulus, adhesive force, and friction angle. A tire simulation device that reproduces the behavior of tires running on snowy roads,
a tire model setting unit that sets a tire model modeled with a finite number of elements that can be numerically analyzed;
Euler element model settings that set up an Euler element model that includes a snow model as an analysis model with snow placed inside;
a dynamic analysis unit that performs dynamic analysis by rolling the tire model on the snow model;
Equipped with
The dynamic analysis section calculates the deformation of the tire model and the snow model, calculates the density distribution of snow in the snow model from the result of the deformation calculation, and calculates the snow density distribution according to the snow density from the obtained density distribution. setting plastic properties in the snow model, and calculating deformation of the tire model and the snow model using the snow model having the set elastic-plastic properties;
A tire simulation device characterized by: A program for reproducing the behavior of tires running on snowy roads,
to the computer,
A tire model setting function that sets a tire model modeled with a finite number of elements that can be numerically analyzed;
Euler element model setting function that sets an Euler element model including a snow model as an analysis model with snow placed inside;
A dynamic analysis function that performs dynamic analysis by rolling the tire model on the snow model, calculates the deformation of the tire model and the snow model, and calculates the amount of snow in the snow model from the result of the deformation calculation. A density distribution is calculated, and elastic-plastic characteristics corresponding to the snow density are set in the snow model based on the obtained density distribution, and the snow model having the set elastic-plastic characteristics is used to create the tire model and the snow model. A dynamic analysis function that calculates the deformation of
A tire simulation program to realize this.

Images