JP4486105B2 - Tire performance prediction method, ground simulation method, tire design method, recording medium, and tire performance prediction program - Google Patents

Description

  The present invention relates to a tire performance prediction method, a ground simulation method, a tire design method, a recording medium, and a tire performance prediction program. The present invention relates to the performance of a tire having a tread pattern used in an automobile or the like, particularly a fluid including soil. The present invention relates to a tire performance prediction method for predicting tire performance via tires, a ground simulation method for simulating ground behavior around a tire, a tire design method, a recording medium, and a tire performance prediction program.

  Conventionally, in the development of pneumatic tires, tire performance is obtained by actually designing and manufacturing tires, mounting them on automobiles, and performing performance tests. I have taken the steps of starting over. Recently, due to the development of numerical analysis methods such as the finite element method and the computer environment, for example, tire performance for paved road surfaces is predicted by performing load analysis and rolling analysis on tire rigid road surfaces with a computer. It has become possible, and several performance predictions can be made from here.

  Also, with respect to the performance for the road surface on snow, a technique for performing deformation calculation of a snow model while discriminating an elastic region or a plastic region is known (see, for example, Patent Document 1).

  However, for tire performance, consideration is given to fluids and materials such as water and snow, but a field including soil similar to snow can be considered. There is a possibility that the field will be studied in the category of performance on snow using soil as a material, but in reality, the phenomenon handled by the tire traveling on the snow and the tire traveling on the field may be greatly different. That is, it is considered that the on-snow performance is dominated by the shear strength against normal stress. On the other hand, the field performance shows performance after a very large settlement occurs, so the phenomenon cannot be reproduced only by the shear strength against normal stress.

For this reason, techniques for numerical modeling of the field and coupled analysis of the field and the tire have been proposed (see, for example, Patent Documents 2 and 3).
Japanese Patent No. 3305705 JP 2006-51840 A JP 2006-131067 A

  However, in the techniques described in Patent Documents 2 and 3, although it is possible to predict the traction (traction force) performance of a tire used in a field, for example, sand or gravel (hereinafter referred to as coarse grain soil) is used. It was difficult to predict traction performance on the dominant road surface. In Japan, soil materials are classified as (1) coarse-grained soil (for example, sand), (2) fine-grained soil (for example, clay), and (3) highly organic soil, but the fields are (1) to (3) Can be thought of as a mixture.

  And it is difficult to predict the traction generated when traveling on the ground of coarse-grained soil only by considering only the volume elastic behavior and the shear strength of the road surface material as in the techniques described in Patent Documents 2 and 3 above. there were.

  In the case of coarse-grained soil, the influence of friction between the tire and the coarse-grained soil increases, but the traction in the techniques described in Patent Documents 2 and 3 is dominated by the shear force generated by the tread pattern of the tire. However, in reality, traction occurs even if there is no tread pattern. This is because, in the case of the ground of coarse-grained soil, the influence of the shearing force of the coarse-grained soil in traction is relatively smaller than that of ordinary soil due to the low adhesive strength in the shear characteristics.

  The techniques described in Patent Documents 2 and 3 do not consider the influence of friction between the tire and the field, so that the performance of the tire when traveling on the ground of coarse-grained soil such as sand is particularly accurate. There was a problem that it could not be predicted.

  Further, Patent Document 1 describes that a friction coefficient is defined between a snow model and a tire model. However, it is not clear how to define the friction coefficient, and rough sand such as sand is not clearly defined. There has been a problem that it is not always possible to accurately predict the performance of the tire when traveling on the ground of grain soil.

  In view of the above facts, the present invention is a tire performance prediction method, a ground simulation method, and a tire development that can easily and accurately predict tire performance such as tire traction performance when traveling on the ground. It is an object to obtain a tire performance prediction method, a ground simulation method, a tire design method, a recording medium, and a tire performance prediction program capable of obtaining a tire with good performance.

  In order to achieve the above object, the present invention predicts the performance of a tire that is actually used through the ground, in particular, enables analysis of the ground behavior at the time of tire contact and rotation, and also makes the tire development more efficient, This makes it easy to provide tires with good performance.

Specifically, the tire performance prediction method of the present invention includes the following steps (a) to (g).
(A) a tire model having a pattern shape capable of being deformed by at least one of ground contact and rolling, and at least part of the tire model that is partially or entirely filled with an elastic-plastic material or a material including a plastic material. Determining a ground model in contact with the part.
(B) executing deformation calculation of the tire model;
(C) A step of executing deformation calculation of the ground model.
And moisture content of the soil was determined on the basis of the information on density of the ground, including (d) is soil material, based on the ground state information is information representing a relation between the friction coefficient between the tire model and the ground model Calculating the friction force generated between them.
(E) Recognizing a boundary surface between the tire model after the deformation calculation in the step (b) and the ground model after the deformation calculation in the step (c), and determining the boundary condition regarding the recognized boundary surface The calculation of the steps (b) to (d) is repeated for the tire model and the ground model after being applied to the tire model and the ground model and the frictional force is applied to the tire model and the boundary condition is applied. And calculating until deformation of the tire model and the ground model can be regarded as a steady state.
(F) A step of obtaining a physical quantity generated in at least one of the tire model and the ground model in the step (c) or the step (e).
(G) A step of predicting tire performance in the ground based on the physical quantity.

  That is, in the tire performance prediction method of the present invention, first, in order to predict the performance of a tire design plan (change of tire shape, structure, material, pattern, etc.) to be evaluated, the tire design plan is used as a model for numerical analysis. Drop it. That is, a tire model (numerical analysis model) capable of numerical analysis is created. Furthermore, the ground (which can include the road surface) related to the target performance, which is an elastic-plastic material or a material containing at least a plastic body, is modeled, a ground model (numerical analysis model) is created, and the tire and the ground (the road surface are Numerical analysis that considers the target performance at the same time. Whether the tire design plan is acceptable or not is determined from the prediction result. If the result is good, the design plan is adopted, or a tire of this design plan is manufactured and performance evaluation is performed. If the result is satisfactory, the design plan is adopted. If the prediction performance (or actual measurement performance) by the design plan is insufficient, a part or all of the design plan is corrected, and the numerical analysis model is created again. With these procedures, the number of times of manufacturing and evaluating the performance of the tire is extremely small, so that the tire development can be made more efficient.

Therefore, in order to develop a tire based on performance prediction, an efficient and accurate numerical analysis model for predicting tire performance is indispensable. Therefore, in the present invention, in order to predict tire performance, in step (a), at least a tire model having a pattern shape that can be deformed by at least one of ground contact and rolling, and an elastoplastic body or a plastic body is provided. A ground model that is partially or wholly filled with the material to be included and is in contact with at least a portion of the tire model. A road surface model can be further determined. In step (b), deformation calculation of the tire model is executed, and in step (c), deformation calculation of the ground model is executed. In step (d), the water content of the soil was determined on the basis of the information on density of the ground comprising soil material, based on the ground state information is information representing a relation between the friction coefficient, the said tire model Soil Calculate the friction force generated with the model. In step (e), a boundary surface between the tire model after the deformation calculation in step (b) and the ground model after the deformation calculation in step (c) is recognized, and the boundary condition regarding the recognized boundary surface is set as the tire model. And applying the friction force to the tire model and repeating the calculations of steps (b) to (d) for the tire model and the ground model after the boundary condition is applied, Calculate until the deformation of the ground model can be regarded as a steady state. In step (f), a physical quantity generated in at least one of the tire model and the ground model in step (c) or step (e) is obtained, and in step (g), the tire performance is predicted based on the physical quantity.

  In the ground with soil etc., when a load is applied, the internal structure (for example, a structure formed by cavities and water and soil) changes and deforms, but even when unloaded, the deformation recovers and returns to the initial shape is rare Absent. For this reason, for example, in order to express the ground with soil etc. as a numerical model, the ground is made a plastic body, and if necessary, it is also given a characteristic as an elastic body to generate an appropriate reaction force when loaded Turn into. Thus, for example, by modeling the ground having soil or the like as an elastic-plastic body or a plastic body (rigid plastic body), the tire performance can be predicted with high accuracy.

In addition, it occurs between the tire model and the ground model based on the ground condition information that is the information indicating the relationship between the moisture content of the ground and the friction coefficient obtained based on the information on the density of the ground including the soil material. Since the frictional force to be calculated is applied to the tire model, the tire performance can be predicted with higher accuracy.
Even when the moisture content cannot be obtained directly, the moisture content can be estimated from the density of the ground, and the frictional force can be calculated using this.

Thus, the moisture content of the soil was determined on the basis of the information on density of the ground comprising soil material, the tire model the frictional force calculated on the basis of the ground state information is information representing a relation between the friction coefficient Therefore, the tire performance such as the tire traction performance in the ground containing the soil material can be predicted with high accuracy.

According to a second aspect of the present invention, the ground state information includes at least one of an exponential function expression, a logarithmic function expression, and a functional expression using a quadratic or higher order polynomial, representing the relationship between the moisture content of the ground and the friction coefficient. It is a function expression approximated by two.

As described above, the ground state information is the relationship between the moisture content of the ground and the friction coefficient, and is at least one of an exponential function expression, a logarithmic function expression, a linear expression, and a functional expression based on a second or higher order polynomial. By using an approximate function formula, the frictional force can be calculated with higher accuracy.

According to a third aspect of the present invention, the step (f) includes a step of calculating a stress acting on the tire model, and the step (g) performs a traction as the tire performance based on the stress. A step of calculating.

  As described above, since the frictional force between the tire and the ground is considered in the stress obtained in step (f), the traction (traction force) obtained from the stress is a traction in which the frictional force is considered. . Therefore, the traction performance can be predicted with high accuracy.

The ground simulation method of the invention described in claim 4 includes the following steps (a) to (e).
(A) a tire model having a pattern shape capable of being deformed by at least one of ground contact and rolling, and at least part of the tire model that is partially or entirely filled with an elastic-plastic material or a material including a plastic material. Determining a ground model in contact with the part.
(B) executing deformation calculation of the tire model;
(C) A step of executing deformation calculation of the ground model.
(D) the moisture content of the soil was determined on the basis of the information on density of the ground comprising soil material, based on the ground state information is information representing a relation between the friction coefficient between the tire model and the ground model Calculating the friction force generated between them.
(E) Recognizing the boundary surface between the tire model after the deformation calculation in the step (b) and the ground model after the deformation calculation in the step (c), and the boundary condition related to the recognized boundary surface is defined as the tire model and The tire model and the ground model are repeatedly applied to the ground model and the friction force is applied to the tire model, and the tire model and the ground model after the boundary condition is applied, A step of calculating until the deformation of the ground model can be regarded as a steady state.

When simulating the behavior of the fluid around the tire, a tire model having a pattern shape that can be deformed by at least one of grounding and rolling in step (a) and an elastic-plastic body or a material including at least a plastic body are used. A ground model that is partially or wholly filled and in contact with at least a part of the tire model is determined, and the deformation calculation of the tire model is executed in step (b), and the deformation calculation of the ground model is executed in step (c). and, step and moisture content of the soil was determined on the basis of the information on density of the ground comprising soil material in (d), on the basis of the ground state information is information representing a relation between the friction coefficient, the said tire model The frictional force generated between the ground model and the ground model is calculated. Recognizing a boundary surface between the tire model after calculation and the ground model after the deformation calculation in the step (c), the boundary condition regarding the recognized boundary surface is given to the tire model and the ground model, and the frictional force is Repeat steps (b) to (d) for the tire model and ground model after applying the boundary conditions to the tire model, and calculate until the deformation of the tire model and ground model can be regarded as a steady state. By doing so, it is possible to evaluate the ground around the tire, predict the behavior of the ground, and use it for the tire performance prediction.

The tire designing method of the invention of claim 5 includes the following steps (1) to (7).
(1) A tire model having a pattern shape capable of being deformed by at least one of ground contact and rolling, and at least part of the tire model that is partially or entirely filled with an elastic-plastic material or a material including a plastic material. Determining a ground model in contact with the part.
(2) A step of executing deformation calculation of the tire model.
(3) A step of executing deformation calculation of the ground model.
(4) of the ground calculated based on the information on density of the ground comprising soil material and water content, based on the ground state information is information representing a relation between the friction coefficient between the tire model and the ground model Calculating the friction force generated between them.
(5) Recognizing a boundary surface between the tire model after the deformation calculation in the step (2) and the ground model after the deformation calculation in the step (3), the boundary condition relating to the recognized boundary surface is set as the tire model and The tire model and the ground model are applied to the ground model and the frictional force is applied to the tire model, and the calculation of the steps (2) to (4) is repeated for the tire model and the ground model after the boundary condition is applied. A step of calculating until the deformation of the ground model can be regarded as a steady state.
(6) A step of obtaining a physical quantity generated in at least one of the tire model and the ground model in the step (3) or the step (5).
(7) A step of predicting tire performance on the ground based on the physical quantity.
(8) A step of correcting the tire model in consideration of the tire performance.
(9) A step of repeatedly calculating correction of the tire model in consideration of the tire performance as a result of executing the steps (2) to (7) for the tire model after correction in the step (8).
(10) A step of designing a tire based on the tire model calculated in step (9).

When designing a tire, part or all of the tire model having a pattern shape that can be deformed by at least one of ground contact and rolling in step (1), and an elastic-plastic material or a material including at least a plastic material. A ground model that is satisfied and is in contact with at least a part of the tire model is determined, a deformation calculation of the tire model is performed in step (2), a deformation calculation of the ground model is performed in step (3), and a step (4 ) and the moisture content of the soil was determined on the basis of the information on density of the ground comprising soil material, based on the ground state information is information representing a relation between the friction coefficient between the tire model and the ground model In step (5), the boundary surface of the tire model and the ground model after the deformation calculation is recognized, and the recognized boundary surface is The boundary conditions are applied to the tire model and the ground model, the friction force is applied to the tire model, and the calculation of the steps (2) to (4) is repeated for the tire model and the ground model after the boundary condition is applied. Then, calculation is performed until the deformation of the tire model and the ground model can be regarded as a steady state, and a physical quantity generated in at least one of the tire model and the ground model is obtained in step (6). The tire performance is predicted, and in step (8), the tire model is corrected in consideration of the predicted tire performance. In step (9), the result of executing steps (2) to (7) for the corrected tire model. In the step (10), it is repeatedly calculated that the tire model is corrected in consideration of the tire performance. Designing the tire based on the calculated result the tire model at 9).

  In this way, it is possible to design a tire that considers the ground performance as the tire performance while evaluating the ground around the tire and predicting the behavior of the ground.

The invention of claim 6 is a recording medium on which a tire performance prediction program for predicting tire performance by a computer is recorded, and includes the following steps.
(A) a tire model having a pattern shape that can be deformed by at least one of ground contact and rolling, and an elastoplastic body or a material that includes at least a plastic body, and a part or all of the tire model is at least Determining a ground model in contact with the part.
(B) A step of performing deformation calculation of the tire model.
(C) A step of executing deformation calculation of the ground model.
(D) and the moisture content of the soil was determined on the basis of the information on density of the ground comprising soil material, based on the ground state information is information representing a relation between the friction coefficient between the tire model and the ground model Calculating the friction force generated between them.
(E) Recognizing a boundary surface between the tire model after the deformation calculation in the step (B) and the ground model after the deformation calculation in the step (C), the boundary condition regarding the recognized boundary surface is set as the tire model and The tire model and the ground model are applied to the ground model and the frictional force is applied to the tire model, and the calculation of the steps (B) to (D) is repeated for the tire model and the ground model after the boundary condition is applied. A step of calculating until the deformation of the ground model can be regarded as a steady state.

When predicting tire performance by a computer, part of the tire model having a pattern shape that can be deformed by at least one of ground contact and rolling in step (A) and an elastic-plastic material or a material including at least a plastic material Alternatively, a ground model that is completely filled and that contacts at least a part of the tire model is determined, and deformation calculation of the tire model is executed in step (B), and deformation calculation of the ground model is performed in step (C). is executed, on the basis of the ground state information is information indicating the moisture content of the soil was determined on the basis of the information on density of the ground comprising soil material in step (D), the relation between the friction coefficient, and the tire model The frictional force generated between the ground model and the tire model after the deformation calculation in step (B) is calculated in step (E). And the ground surface after the deformation calculation in step (C) is recognized, the boundary condition regarding the recognized boundary surface is applied to the tire model and the ground model, and the friction force is applied to the tire model. And each step of making it calculate until the deformation | transformation of the said tire model and a ground model can be considered as a steady state by repeating the calculation of said step (B)-(D) about the tire model and ground model after providing boundary conditions. If the tire performance prediction program including the program is stored and executed in a storage medium and data is collected, it can be used for comparison with past performance evaluations and for future data accumulation.

  When the tire performance is predicted by a computer, the tire performance can be predicted easily and simply by causing the computer to execute the following program.

The invention according to claim 7 is a tire performance prediction program, and includes the following steps for predicting tire performance by a computer.
(I) a tire model having a pattern shape capable of being deformed by at least one of ground contact and rolling, and at least part of the tire model that is partially or entirely filled with an elastic-plastic material or a material including a plastic material. Determining a ground model in contact with the part.
(II) A step of executing deformation calculation of the tire model.
(III) A step of executing deformation calculation of the ground model.
And moisture content of the soil was determined on the basis of the information on density of the ground comprising (IV) soil material, based on the ground state information is information representing a relation between the friction coefficient between the tire model and the ground model Calculating the friction force generated between them.
(V) Recognizing the boundary surface between the tire model after the deformation calculation in the step (II) and the ground model after the deformation calculation in the step (III), and the boundary condition related to the recognized boundary surface is defined as the tire model and The tire model and the ground model are applied to the ground model and the frictional force is applied to the tire model, and the calculation of the steps (II) to (IV) is repeated for the tire model and the ground model after the boundary condition is applied. A step of calculating until the deformation of the ground model can be regarded as a steady state.

  As described above, according to the present invention, it is possible to easily and accurately predict tire performance such as tire traction performance when traveling on the ground.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  In the present embodiment, the present invention is applied to performance prediction of a pneumatic tire. In the present embodiment, a case where a field model including a soil material including a coarse-grained soil, a fine-grained soil, and a highly organic soil is employed as the ground model will be described, but the present invention is limited to the field model. Instead, the present invention can also be applied to other ground models including the above-mentioned soil materials, and to ground models including, for example, rock materials, stone-soiled soil materials, artificial materials, and the like.

  FIG. 2 shows an outline of a personal computer for performing tire performance prediction in consideration of the field performance of the present invention. The personal computer includes a keyboard 10 for inputting data and the like, a computer main body 12 that predicts tire performance according to a pre-stored processing program, and a CRT 14 that displays calculation results of the computer main body 12 and the like.

  The computer main body 12 includes a flexible disk unit (FDU) into which a flexible disk (FD) as a recording medium can be inserted and removed. Note that processing routines and the like described later can be read from and written to the flexible disk FD using the FDU. Therefore, a processing routine to be described later may be recorded in the FD in advance and the processing program recorded in the FD may be executed via the FDU. Further, a mass storage device (not shown) such as a hard disk device is connected to the computer main body 12, and the processing program recorded on the FD is stored (installed) in the mass storage device (not shown) and executed. Also good. Recording media include optical discs such as CD and DVD, and magneto-optical discs such as MD and MO. When these are used, instead of or in addition to the FDU, a CD-ROM device, a CD-RAM device, a DVD- A ROM device, DVD-RAM device, MD device, MO device, or the like may be used.

  FIG. 1 shows a processing routine of the present embodiment. This process derives the optimum shape of the tire while performing the tire performance prediction evaluation.

  In step 100, a design plan (change of tire shape, structure, material, pattern, etc.) of the tire to be evaluated is determined. In step 100, the field performance measurement results and the relationship regarding the shear strength in the field (for example, represented by an approximate expression) and the relationship regarding the friction coefficient in the field (for example, represented by an approximate expression) are read. As a technique regarding the relationship between the measurement results of the field performance and the shear strength in the field, the technique already applied by the present applicant (Patent Document 2 described above) can be used.

  An example of a technique for obtaining field performance will be described. First, actual field measurement is performed, and a predicted value of field performance is obtained by numerical calculation using the actual field measurement. In the numerical calculation, the field and the tire are coupled, and after obtaining the shear stress distribution corresponding to the contact pressure acting on the tire, the traction is obtained to obtain the predicted value. For example, the field measurement by a soil test is performed, and a measurement result is made into a database. In addition, as a field material characteristic, the relationship between the gap ratio of a field, stress, and shear strength is measured. Further, it may be a field containing soil as a fluid in contact with the tire, or may include an elastic-plastic material or a plastic material. For example, a fluid containing particulate ice blocks, a fluid containing soil or mud, or a fluid containing frosted soil or mud. Each or a combination of these may be used.

  Since it is difficult to reproduce the strength in the depth direction in the field, the shear resistance pile is measured and the penetration resistance is measured in the actual field. The penetration resistance indicates the intensity distribution in the depth direction of the field. In addition, in order to model an agricultural field model so that a several layer may be comprised in the depth direction, the material (material which comprises an agricultural field) of each layer is measured. That is, the shear resistance value is measured by measuring the strength on the field (soil) surface, and the penetration resistance value is measured by measuring the strength distribution in the depth direction of the field (soil). The shear resistance corresponds to the measurement of the relationship between the normal stress and the shear stress as a strength measurement of the field (soil). The penetration resistance corresponds to the measurement of the relationship between the pressure and the amount of settlement as a strength measurement of the field (soil). This measurement result is made into a database. Thereby, the field data can be freely used. As an example of the measurement result, the measurement result of the shear resistance (relation between vertical stress and shear stress, Fig. 3), which is the strength measurement on the field (soil) surface, the measurement result of the penetration resistance (the relationship between the pressure and the amount of settlement) Relationship, Fig. 4).

  Next, a function approximation of the relationship between the gap ratio, pressure, and shear strength of the field is performed. Specifically, fields are related to gap ratio, pressure, and stress. In this case, as a characteristic that the field should have, there is a predetermined relationship among the volume strain, the gap ratio, and the density (FIG. 6), and the log ratio of the field gap ratio and pressure is proportional (FIG. 5). ). Also, pressure and volume strain are not proportional. Since the bulk elastic modulus K is a function of pressure, it can be expressed as a function of density. Therefore, assuming a Poisson's ratio (for example, 0.3), the shear elastic modulus can be determined. FIG. 7 shows the relationship between density and pressure.

  Using the above relationship, a function that relates the density of the field and the gap ratio is derived from the density of the material that constitutes the field, that is, the soil particles and the material that fills the gap, and the change in the gap ratio and the volume distortion of the field A function that relates to is derived. For the pressure increment generated in the field, an exponential function using volumetric strain or the like can be adopted. The bulk modulus and shear modulus can be derived as a function determined according to this pressure. The shear strength can be derived as a function determined by the pressure and plastic strain calculated in these processes. With the above procedure, a function for determining the shear strength of the field can be derived. In other words, since the gap ratio and pressure are expressed in terms of density with respect to the field, the relationship between the shear strength, the gap ratio, and the pressure is an approximate expression using, for example, a polynomial expression according to the following function f as a relational expression between the shear strength and the density. Can be expressed as

t = f (ρ, e (ρ), P (ρ)) = c ₁ + c ₂ ρ + c ₃ ρ ² +... + c _n ρ ⁿ⁻¹ (1)
However, e is a gap ratio, P is a pressure, ρ is a density, and n is a natural number.

  As a result, a field including soil and the like can be modeled based on the above function formula. Specifically, by calculating the shear resistance and penetration resistance by calculation and setting the parameters used in the field model so that the obtained resistance value and measured value match the shear and penetration, the field performance of the tire is predicted. A sufficient field model can be created. That is, it is preferable to calculate a large number of shear resistance values and penetration resistance values in advance for the field model and to construct a database based on the shear resistance values and penetration resistance values.

  Next, an example of a technique for obtaining the relationship regarding the friction coefficient in the field will be described.

  As described above, in the case where the ground is a field such as coarse-grained soil, the influence of friction between the tire and the coarse-grained soil is increased. Therefore, in this embodiment, the friction coefficient of friction generated between the tire and the field is large. And predict the traction performance of the field considering this.

  The coefficient of friction depends on the field conditions such as pressure, moisture content, sliding speed, and temperature. Hereinafter, the dependency of the friction coefficient and the state of the field will be described.

  First, the pressure dependence of the friction coefficient will be described.

  When the ground in contact with the tire is soil, the density changes due to consolidation, and at the same time, the true contact area with the tire changes greatly. When viewed microscopically, the number of soil particles in contact with the tire changes. Therefore, as shown in FIG. 8, it is considered that the friction coefficient increases until the pressure applied to the ground (tire contact pressure of the tire) increases to some extent.

  Next, the moisture content dependency of the friction coefficient will be described.

  If the ground in contact with the tire is soil that contains relatively moisture, if the deformation is faster than the time it takes to drain the moisture contained in the soil, if large pressure is applied, the soil skeleton structure will be destroyed. The force is generated only by the water confined in the gap. At this time, although a large pressure is generated, since the moisture has almost no shear rigidity, the shear strength is lowered. Furthermore, the frictional force between the tire surface and the soil particles decreases due to the lubricating action of the springed water. For this reason, as shown in FIG. 9, it is considered that the friction coefficient decreases as the moisture content increases.

  Usually, when the pressure increases, the porosity decreases, and the moisture content increases accordingly. Thus, the pressure dependency of the friction coefficient is also closely related to the moisture content dependency, and the pressure dependency changes depending on the initial moisture content. For example, as shown in FIG. 10, the relationship between the coefficient of friction and the pressure is different between soil having a low moisture content and soil having a high moisture content.

  Next, the sliding speed dependence of the friction coefficient will be described.

  When the ground in contact with the tire is soil, the influence of the sliding speed (relative speed between the ground and the tire) cannot be ignored. For example, even for a tire without a tread pattern, the traction generated by friction between the ground and the tire increases, for example, according to an increase in slip ratio (or slip shear distance), and then maintains a constant value. As shown in FIG. 11, in the case of soil with a sparse initial state, particles are re-packed by receiving a shearing action due to friction with the tire, and the frictional force increases as the contact area increases. Since the true contact area does not increase when filled, the friction coefficient is constant. On the other hand, when the soil is densely packed in the initial state, a volume increase due to dilation (a volume increase due to shear deformation) is accompanied in the initial stage of shearing. In addition, the peak part of the friction coefficient in the case of the dense soil shown in FIG. 11 represents the pressure increase accompanying the volume increase by dilation.

  Next, the temperature dependence of the friction coefficient will be described.

  For example, in an environment where the temperature is higher than normal temperature, such as a desert, when the moisture in the soil evaporates, the soil (sand) expands and becomes a state with a high gap ratio (fluffy state). Naturally, the moisture content is low. This state itself should be dealt with by a model of the initial state of the soil (sand), and it is necessary to consider the influence of temperature.

  In this embodiment, although details will be described later, the frictional force acting on the tire is calculated by calculating the friction coefficient in consideration of the pressure dependency, the moisture content dependency, the sliding speed dependency, and the temperature dependency, and the tire performance. Predict traction performance as

  When obtaining the relationship regarding the friction coefficient in the field as described above, the field measurement is actually performed and the measurement result is made into a database. In this field measurement, for example, a block sample in which a soil material to be measured for traction performance is made into a block of a predetermined size is used.

  In the field measurement, the relationship between the friction coefficient and the pressure, the relationship between the friction coefficient and the moisture content, the relationship between the friction coefficient and the sliding speed, and the relationship between the friction coefficient and the temperature as shown in FIGS. To do. In addition, here, a field including soil or the like is assumed as a fluid in contact with the tire. However, the field as the fluid may include at least an elastoplastic body or a plastic body, for example, a fluid including particulate ice blocks, a soil Each or a combination of mud, mud, frosted soil or fluid containing mud may be used.

  Then, the measurement results are made into a database. Thereby, the field data can be freely used.

  Next, based on the measurement data stored in the database, a function approximation is performed for the relationship between the friction coefficient and pressure, the relationship between the friction coefficient and moisture content, the relationship between the friction coefficient and sliding velocity, and the relationship between the friction coefficient and temperature. From these functions, a friction function for setting a friction coefficient in consideration of all of pressure, moisture content, sliding speed, and temperature is set.

That is, based on the measurement data, first, a function μ _P (P) for obtaining the friction coefficient from the pressure P, a function μ _w (w) for obtaining the friction coefficient from the moisture content W, and a function μ _V (for obtaining the friction coefficient from the sliding speed V V) and a function μ _T (T) for obtaining a friction coefficient from the temperature T.

  Then, a friction function μ (P, w, V, T) for calculating a friction coefficient from the values of these functions is set as follows.

μ (P, w, V, T) = μ ₀ × μ _P (P) × μ _w (w) × μ _V (V) × μ _T (T) (2)
Here, μ ₀ is a reference friction coefficient in reference conditions (P ₀ , w ₀ , V ₀ , T ₀ ) determined in advance for pressure, moisture content, sliding speed, and temperature.

Each function μ _P (P), μ _w (w), μ _V (V), and μ _T (T) uses a function normalized with respect to the reference friction coefficient μ ₀ . That is, μ _P (P ₀ ) = μ _w (w ₀ ) = μ _V (V ₀ ) = μ _T (T ₀ ) = 1.

  Each function can be a function expression approximated by at least one of an exponential function expression, a logarithmic function expression, a linear expression, and a function expression based on a second or higher order polynomial. When the number of measurement data is insufficient, each function may be derived using an interpolation function represented by a spline function. When at least one parameter of pressure, moisture content, sliding speed, and temperature is not considered, the function of the parameter may be a function that always returns 1. Thereby, the influence of the parameter can be easily ignored.

  In this way, the friction coefficient in the field changes depending on pressure, moisture content, sliding speed, and temperature. Therefore, if the field is modeled by approximating these relationships using a functional equation, the field that is stepped and solidified by the tread pattern In contrast, different stresses and the like can be calculated at each location. As a result, the traction performance generated between the field and the tire can be predicted with high accuracy.

  In the next step 102, a tire model is created in order to drop the tire design proposal into a numerical analysis model. In the present embodiment, the tire model is created by using a finite element method (FEM) as a numerical analysis method. Therefore, the tire model created in step 102 is divided into a plurality of elements by element division corresponding to the finite element method (FEM), for example, mesh division, and the tire is created based on a numerical / analytical method. This is a digitized input data format for computer programs. This element division means dividing an object such as a tire, a field (fluid), and a road surface into several small (finite) small parts. After calculating every small part and calculating all the small parts, the whole response can be obtained by adding all the small parts. Note that a difference method or a finite volume method may be used as a numerical analysis method.

  In the creation of the tire model in step 102, a pattern is modeled after a tire cross-section model is created.

  Specifically, first, a tire radial section model, that is, tire section data is created. The tire cross-section data is obtained by measuring the tire outer shape with a laser shape measuring instrument or the like. Further, an accurate internal structure of the tire may be collected from a design drawing and actual tire cross-section data. The rubber and the reinforcing material in the tire cross section (belt, ply, etc., which is a bundle of reinforcing cords made of iron / organic fibers, etc.) are modeled according to the modeling method of the finite element method, respectively (FIG. 12). (See (A)). Next, the tire cross-section data (the tire radial cross-section model), which is two-dimensional data, is developed by one turn in the circumferential direction to create a three-dimensional (3D) model of the tire (see FIGS. 12B and 12C). ). Next, the pattern is modeled. This pattern is modeled by “modeling part or all of the pattern separately and pasting it as a tread part on the tire model”, “considering rib and lug components when developing tire cross-section data in the circumferential direction. To create a pattern ". FIG. 13 shows a three-dimensional tire model including a pattern.

  After creating the tire model as described above, the process proceeds to step 104 in FIG. 1 to create an agricultural field model. This field model is a fluid containing soil such as soil. The creation of the field model is to divide and model a part (or all) of a tire, a ground contact surface, and a field (fluid region) including a region where the tire moves and deforms. Specifically, the field is configured by laminating layers composed of a plurality of single material models. As described above, the material model of each layer is a function of the relationship between the field gap ratio (or density), pressure, and shear strength combined with exponential functions, logarithmic functions, and polynomials. It is determined as a parameter determined by the penetration test and shear test.

  In this way, when the creation of the agricultural field model is completed, the environment construction that can be evaluated is completed by inputting the road surface state together with the creation of the road surface model. Here, since soil in a field or the like is assumed as an agricultural field, road surface modeling is not particularly necessary.

  In the next step 108, boundary conditions are set. That is, since a part of the tire model is interposed in a part of the field model, it is necessary to simulate the behavior of the tire and the field by giving an analytical boundary condition to the field model and the tire model. Since this procedure may be different between when the tire is rolling and when the tire is not rolling, it is only necessary to select whether the tire is rolling or when the tire is not rolling by input or the like.

  In setting the boundary conditions at the time of tire rolling in step 108, first, boundary conditions relating to inflow / outflow are given to the field model (fluid region). In this boundary condition for inflow / outflow, fluid such as soil and mud flows out freely on the upper surface of the field model (fluid region), and other front, rear, side, and lower surfaces are treated as walls (no inflow / outflow). Next, internal pressure is applied to the tire model, and then, at least one of rotational displacement and linear displacement (displacement may be force or speed) and a predetermined load load are applied to the tire model.

  In step 108, when the boundary condition is set when the tire is not rolling, first, boundary conditions relating to inflow / outflow are given to the fluid model. Here, since the analysis is performed in a steady state, the tire model is stationary in the traveling direction, and a model in which soil, mud, or the like, which is a field material, moves toward the tire model at a traveling speed is considered. That is, the flow velocity is given to fluid such as soil and mud in the field model (fluid region). The boundary conditions related to inflow / outflow are that the front surface of the fluid model (fluid region) flows in at an advancing speed, the rear surface is outflow, and the upper surface, side surface, and lower surface are the same as when rolling. An internal pressure is applied to the tire model to apply a load to the tire model.

  In the next step 110, deformation calculation of the tire model is performed, and in the next step 112, deformation calculation of the field model is performed. In order to obtain a steady state for the deformation of the tire model and the field model, the deformation calculation of the tire model and the deformation calculation of the field model are each performed within a predetermined time (for example, 1 msec), and are performed every fixed time (for example, 1 msec). The boundary conditions between the two are updated.

(Tire model deformation calculation)
Based on the tire model and the given boundary conditions, deformation calculation of the tire model is performed based on the finite element method. In order to obtain a transient state, the tire model deformation calculation is repeated while the elapsed time (single elapsed time) is 1 msec or less, and after 1 msec, the next calculation (fluid) is started.

(Deformation calculation of field model)
Based on the fluid model and given boundary conditions, fluid calculation is performed based on the finite element method or the finite volume method. In order to obtain a transient state, fluid calculation is repeated while the elapsed time (single elapsed time) is 1 msec or less, and when 1 msec elapses, the next calculation (deformation of the tire model) is started. In addition, although mentioned later for details, the fluid is assumed as an elastic-plastic body, and the stress distribution which acts on a tire model can be calculated | required from the stress which arises in a fluid.

  In the deformation calculation of the field model, the stress calculation process shown in FIG. 14 is executed. First, in step 319, for each element of the field model, the density change is obtained from the relationship between the inflow and outflow masses to the fluid element, and the current density is obtained. In step 320, the pressure is determined from the density. In the next step 322, the bulk modulus is determined from the density or the previously determined pressure. In the next step 324, a shear elastic modulus is obtained from the previously obtained bulk elastic modulus and Poisson's ratio. In the next step 325, the deviation strain is obtained from the flow velocity difference in the vicinity of the fluid element, and in the next step 326, the deviation stress is obtained using the shear elastic modulus and deviation strain obtained so far, and in the next step 328, The stress is obtained from the pressure and the deviation stress obtained so far.

  Note that either the tire model deformation calculation or the field model deformation calculation may be performed first or in parallel. In these deformation calculations, the elapsed time (single elapsed time) is not limited to 1 msec, and an elapsed time of 10 msec or less can be employed, preferably 1 msec or less, more preferably 1 μ · sec or less. The elapsed time can be adopted. Also, this elapsed time may be set to a different time.

  In the next step 114, the field pressure P, moisture content w, sliding speed V, and temperature T on the tire surface are obtained by a predetermined method (such as an arithmetic expression).

  These depend on the constitutive law (material model) of the ground material used in the ground model (a field model as an example in the present embodiment). In the deformation analysis of a normal ground model, speed, pressure, and shear stress are used, and the value of the ground model element (ground element) in contact with the tire can be used as the pressure on the tire surface. When the size of the tire model element (tire element) and the size of the ground element are different (usually the ground element is smaller), the pressure P is the pressure of a plurality of ground elements in contact with the tire element as shown by the following equation: The average value of is used.

ここで、Ｓ_ｔｉｒｅは地盤要素と接するタイヤ要素の面積であり、Ｓ^ｉ（ｉは添え字）はタイヤ要素と接する各地盤要素の面積であり、Ｐ_ｓｏｉｌは各地盤要素の圧力である。

Here, S _tire is the area of the tire element in contact with the ground element, S ⁱ (i is a subscript) is the area of the local element in contact with the tire element, and _Psoil is the pressure of the local element.

The sliding speed V is a relative speed between the _tire speed V _tire and the ground element flow velocity _Vsoil, and is expressed by the following equation.

V = V _soil −V _tire (4)
In addition, when it is desired to eliminate the difference in size between the tire element and the ground element, the sliding speed V may be obtained by the following formula using the average value of the flow velocity of the ground element.

なお、すべり速度Ｖについても、上記（３）式のように面積により重みをかけた（積分した）すべり速度を求めるようにしてもよい。これにより、より正確なすべり速度を得ることができる。

As for the sliding speed V, the sliding speed weighted (integrated) by the area may be obtained as in the above equation (3). Thereby, a more accurate sliding speed can be obtained.

  The moisture content w and temperature T can also be directly acquired as analysis data using a predetermined arithmetic expression or the like in the deformation analysis of the ground model, for example.

  In step 116, first, the friction coefficient μ corresponding to the pressure P, the moisture content w, the sliding speed V, and the temperature T obtained in step 114 is obtained by the above equation (2). Then, the frictional force Pμ is calculated by multiplying the friction coefficient μ by the pressure P.

Note that the moisture content and temperature may not be obtained depending on the constitutive law of the soil used as the field. In such a case, the moisture content is first calculated by a predetermined method (arithmetic equation or the like) of the soil density, and the moisture content is calculated (estimated) from the density by a predetermined method (arithmetic equation or the like). You may do it. As for the temperature, since the temperature change before and after running the tire is small, if it can be considered that the temperature does not change from the external ambient temperature, the output value of the function μ _T (T) for obtaining the temperature is set to 1, and the temperature You may make it ignore the influence of.

  When the moisture content w, the gap ratio e, and the temperature T are not directly acquired from the analysis data of the deformation analysis in the deformation analysis of the ground model, these can be estimated from the density as follows, for example.

First, in the ground element, the volume _{v s} of soil particles in the initial state, the water volume _{v w,} the volume ratio of the volume _{v a} of the air _{v s:} v w: _v preset the _a. The volume v of the ground element is a _{v s + v w + v a} .

Assuming that all the volume deformation of the ground element occurs in the air portion, the change in density ρ and the change in volume can be related. For example, the volume strain ε _k is expressed by the following equation.

ここで、ρ_ｒｅｆは参照密度を表わし、通常は初期密度と一致する。

Here, ρ _ref represents the reference density and usually coincides with the initial density.

  Further, the gap ratio e is expressed by the following equation.

従って、間隙比の変化は次式で表わされる。

Therefore, the change in the gap ratio is expressed by the following equation.

ここで、上付き０の値は初期状態での値を表わす。また、体積変化は空気部分でのみ発生していると仮定しているので、以下のようになる。

Here, the value of superscript 0 represents the value in the initial state. Further, since it is assumed that the volume change occurs only in the air portion, the following is obtained.

従って、上記（８）式における間隙比の変化は、次式で表わされる。

Therefore, the change in the gap ratio in the above equation (8) is expressed by the following equation.

また、水分率に代えて空隙中（＝ｖ_ｗ＋ｖ_ａ）に水分がどれだけ占めているかを示す飽和度ｓ_ｒを用いることもできる。この飽和度ｓ_ｒは次式で表わされる。

It is also possible to use a saturation s _r indicating whether moisture in voids instead of moisture content (= _v w ₊ v _a) occupies much. This saturation s _r is expressed by the following equation.

これを用いた飽和度の変化は次式で表わされる。

The change of the saturation using this is expressed by the following equation.

上記（８）式、（１２）式と同様に、飽和度の変化は結局次式で表わされる。

Similar to the above equations (8) and (12), the change in saturation is eventually expressed by the following equation.

次のステップ１１８では、タイヤモデル及び圃場モデルを連成させるため、タイヤモデルの変形に応じて圃場モデルの境界面を認識し、境界条件を更新させ、次のステップ１１９においてタイヤモデルに表面圧を付加する。このとき、ステップ１１６で算出した摩擦力Ｐμを加える。

In the next step 118, in order to couple the tire model and the field model, the boundary surface of the field model is recognized according to the deformation of the tire model, the boundary condition is updated, and the surface pressure is applied to the tire model in the next step 119. Append. At this time, the frictional force Pμ calculated in step 116 is added.

  That is, after the boundary condition update in step 118, the tire model boundary condition (surface force) is obtained by adding the frictional force Pμ calculated in step 116 to the pressure calculated in the deformation calculation of the field model in step 119. It is added to the model, and the deformation of the tire model due to pressure is calculated by the deformation calculation of the next tire model. The field side incorporates the surface shape of the tire model after deformation into the boundary condition as a new wall, and the tire model side incorporates the pressure and frictional force of the field into the boundary condition as surface forces applied to the tire model. By repeating this every 1 msec, a steady state can be created in a pseudo manner for the deformation of the tire model and the field model related to the tire performance prediction. In the above, the repetition time (single elapsed time) taken into the boundary condition is set to 1 msec, but a time of 10 msec or less can be adopted, preferably 1 msec or less, more preferably 1 μ · sec or less. Can be adopted.

  In the next step 120, it is determined whether or not the calculation is completed. If the result in step 120 is affirmative, the process proceeds to step 122. If the result in step 120 is negative, the process returns to step 110, and the tire model deformation calculation and the field model are performed again. Each of the deformation calculations is performed for 1 msec. In addition, as a specific determination method, there are the following examples.

  If the tire model is a non-rolling model or a rolling model with an all-round pattern, the target physical quantity (reaction force from the field, pressure, flow velocity, etc.) can be regarded as a steady state (same as the physical quantity calculated previously) Calculation is repeated until the calculation is completed, and an affirmative determination is made. Or, it is repeated until the deformation of the tire model can be regarded as a steady state. Furthermore, it is also possible to end the process when a predetermined time is reached. The predetermined time in this case is preferably 100 msec or more, more preferably 300 msec or more.

  When the tire model models only a part of the rolling model and the pattern, the calculation is repeated until the deformation of the pattern portion to be analyzed is completed. Deformation of the pattern part means that the pattern part comes into contact with the road surface model due to rolling until it leaves the road surface model, or until it reaches the layer of the material model of the field model where the variation in subsidence is small, and then moves away from it Or deformation until reaching a predetermined amount of settlement after touching the field model. The deformation of the pattern portion may be performed from the time when the tire contacts one of the models after rolling for one or more rotations. Furthermore, it is also possible to end the process when a predetermined time is reached. The predetermined time in this case is preferably 100 msec or more, more preferably 300 msec or more.

  In addition, if the tire model and the field model are partially overlapped and defined, the labor for creating the calculation model can be greatly reduced. In addition, by dividing the elements that are partially hidden in the tire model, the initial mesh can be made larger, and it is possible to prevent the calculation time from increasing due to the increase in material elements such as soil, thereby efficiently predicting performance. Yes.

  As described above, the tire model deformation calculation and the field model deformation calculation, the friction force generated between the tire and the field, and the boundary condition change and boundary condition (surface force ) Is added, and calculation is performed with the changed boundary condition. When this is repeated and the calculation is completed, the result is affirmative in step 120, the process proceeds to step 122, the calculation result is output as the prediction result, and the prediction result is evaluated. In addition, during the repeated calculation, the calculation result at that time may be output, and the output may be evaluated or sequentially evaluated. In other words, output and evaluation may be performed during the calculation.

  When the shear stress is obtained as a prediction result, the traction is obtained by integrating the shear stress. Therefore, the shear stress obtained as a result can be integrated, and the traction can be obtained to obtain the prediction result.

  In this embodiment, the friction coefficient between the tire and the field is obtained and the frictional force is calculated and given as a boundary condition of the tire model, so that the traction performance in the field such as coarse-grained soil can be predicted with high accuracy. Can do. Further, since the friction coefficient takes into account various dependencies such as pressure and moisture content, the traction performance and the like can be predicted with higher accuracy than when the friction coefficient is simply fixed.

  As the output of the prediction result, values or distributions of shear stress, pressure, energy, traction, friction coefficient, friction force, etc. can be adopted. Specific examples of the output of the prediction result include pressure output and visualization, and stress distribution output and visualization. In addition, the evaluation includes an evaluation of whether the traction is an acceptable value, a subjective evaluation (whether it is flowing smoothly, judgment of turbulence depending on the direction of flow, etc.), and pressure / energy is rising locally. Or not. In the case of a pattern, movement in the groove can also be adopted. Further, in the case of a tire model, it is possible to adopt whether the tire rotates and the tire inserts fluid such as soil or mud and pushes it forward. This evaluation of the prediction result is numerically expressed by using the output value of the prediction result and the distribution of the output value, and how well the predetermined allowable value and the allowable characteristic are adapted to each output value and the distribution of the output value. Thus, an evaluation value can be determined.

  Next, in step 124, it is determined from the evaluation of the prediction result whether or not the prediction performance is good. The determination in step 124 may be made by keyboard input, and when the allowable range is set in advance in the evaluation value and the evaluation value of the prediction result is within the allowable range, the prediction performance is good. You may make it judge that there exists.

  As a result of the evaluation of the predicted performance, if the target performance is insufficient, the result is negative in step 124, the design plan is changed (corrected) in the next step 134, the process returns to step 102, and the processing so far is repeated. On the other hand, if the performance is sufficient, an affirmative decision is made in step 124. In the next step 126, a tire having the design plan set in step 100 is manufactured, and performance evaluation is performed on the manufactured tire in the next step 128. . When the result of the performance evaluation in step 128 is satisfactory performance (good performance), the result in step 130 is affirmed, and in the next step 132, the design proposal modified in step 100 or step 134 is improved. Adopt as a thing and end this routine. The adoption of the design plan in step 132 outputs (displays or prints) that the design plan has good performance, and stores the data of the design plan.

  In the above embodiment, a case has been described in which tire performance prediction and evaluation for one design plan are repeated while correcting the design plan, and a design plan to be adopted is obtained. However, a design plan to be adopted from a plurality of design plans is described. You may ask for. For example, tire performance prediction and evaluation may be performed for a plurality of design plans, and the best design plan may be selected from each evaluation result. Further, the best design plan can be obtained by executing the above embodiment for the selected best design plan.

  Next, embodiments of the present invention will be described in detail. In this embodiment, the present invention is applied to performance prediction of a radial tire.

  As a tire standard, the load is a standard load, and the standard load is a maximum load (maximum load capacity) of a single wheel in an application size described in the following standard. The internal pressure at this time is the air pressure corresponding to the maximum load (maximum load capacity) of the single wheel in the applicable size described in the following standard. The rim is a standard rim (or “Approved Rim” or “Recommended Rim”) in an applicable size described in the following standard. The standard is determined by an industrial standard effective in the region where the tire is produced or used. For example, in the United States, "The Tire and Rim Association Inc. Year Book", in Europe "The European Tire and Rim Technical Organization Standards Manual", and in Japan, the Japan Automobile Tire Association "JATMA Year Book". ing.

  After modeling for performance prediction based on this tire, performance prediction of the tire model was performed, and the prediction results and actual measurement results were shown together.

  The tire modeled and prototyped as this example has a tire size of 195 / 65R15, and the tread pattern has a structure without sipes.

  Modeling was done by measuring the outer shape of the tire with a laser profilometer, creating a tire cross-section model from the design drawings and actual tire cross-section data, and developing the tire 3D model (numerical model) in the circumferential direction. . For the tread pattern, a 3D model was created based on the design drawing, and was attached to the tire 3D model as a tread portion. As the tread pattern, “smooth” (no pattern) as shown in FIG. 15A, “pattern A” as shown in FIG. 15B, and “pattern B” as shown in FIG. A model was created.

  In the performance evaluation test, the above tire was assembled to a rim of 6J-15 at an internal pressure of 200 kPa, and the traction force when traveling at a slip rate of 30% was measured by measuring the indoor traction force. The measurement results are shown below.

ここで、「従来法」とは、上記特許文献２記載の方法である。

Here, the “conventional method” is the method described in Patent Document 2.

  As understood from the above table, since the friction force is not considered in the conventional method, the traction in the smooth tire cannot be predicted, whereas the traction can be accurately predicted in the present invention. In the present invention, the difference in traction between “Pattern A” and “Pattern B” can be predicted with high accuracy, and it can be seen that the absolute value is close to the actually measured value.

  Therefore, this performance prediction is effective for the performance prediction of the design plan, and it is possible to replace a part of the tire development cycle of design / manufacturing / performance evaluation with numerical analysis. It is understood that the efficiency of tire development can be improved by utilizing this.

It is a flowchart which shows the flow of a process of the performance prediction evaluation program concerning a tire concerning this Embodiment. It is the schematic of the personal computer for enforcing the tire performance prediction method concerning embodiment of this invention. It is a characteristic view which shows the relationship between a pressure and the amount of subsidence as a measurement result of penetration resistance value. It is a characteristic view which shows the relationship between a normal stress and a shear stress as a measurement result of the shear resistance value which is the intensity | strength of a field (soil). It is a characteristic view which shows the relationship between the gap ratio of a farm field, and the logarithm value of a pressure. It is a conceptual diagram which shows the relationship between a volume distortion, a gap ratio, and a density as a characteristic which an agricultural field should have. It is a characteristic view which shows the relationship between the density of a farm field, and a pressure. It is a diagram which shows the relationship between a pressure and a friction coefficient. It is a diagram which shows the relationship between a moisture content and a friction coefficient. It is a diagram which shows the relationship between a pressure and a friction coefficient for every moisture content. It is a diagram which shows the relationship between a pressure and a sliding speed. A tire model is shown, (A) is a tire radial direction section model (B), a tire three-dimensional model is shown, (C) is a perspective view showing an image which modeled a pattern. It is a perspective view which shows the image of a three-dimensional tire model. It is a flowchart which shows the flow of the stress calculation process which is a deformation | transformation calculation of an agricultural field model. It is a top view which shows the tread pattern of a tire.

Explanation of symbols

10 Keyboard 12 Computer body 14 CRT
30 Tire model FD Flexible disk (recording medium)

Claims (7)

A tire performance prediction method including the following steps.
(A) a tire model having a pattern shape capable of being deformed by at least one of ground contact and rolling, and at least part of the tire model that is partially or entirely filled with an elastic-plastic material or a material including a plastic material. Determining a ground model in contact with the part.
(B) executing deformation calculation of the tire model;
(C) A step of executing deformation calculation of the ground model.
And moisture content of the soil was determined on the basis of the information on density of the ground, including (d) is soil material, based on the ground state information is information representing a relation between the friction coefficient between the tire model and the ground model Calculating the friction force generated between them.
(E) Recognizing a boundary surface between the tire model after the deformation calculation in the step (b) and the ground model after the deformation calculation in the step (c), and determining the boundary condition regarding the recognized boundary surface The calculation of the steps (b) to (d) is repeated for the tire model and the ground model after being applied to the tire model and the ground model and the frictional force is applied to the tire model and the boundary condition is applied. And calculating until deformation of the tire model and the ground model can be regarded as a steady state.
(F) A step of obtaining a physical quantity generated in at least one of the tire model and the ground model in the step (c) or the step (e).
(G) A step of predicting tire performance in the ground based on the physical quantity. The ground state information is a function obtained by approximating the relationship between the moisture content of the ground and the friction coefficient by at least one of an exponential function expression, a logarithmic function expression, a linear expression, and a functional expression using a polynomial of second or higher order. The tire performance prediction method according to claim 1, wherein the tire performance prediction method is an equation.   The step (f) includes a step of calculating a stress acting on the tire model, and the step (g) includes a step of calculating a traction as the tire performance based on the stress. The tire performance prediction method according to claim 1 or 2. A ground simulation method including the following steps.
(A) a tire model having a pattern shape capable of being deformed by at least one of ground contact and rolling, and at least part of the tire model that is partially or entirely filled with an elastic-plastic material or a material including a plastic material. Determining a ground model in contact with the part.
(B) executing deformation calculation of the tire model;
(C) A step of executing deformation calculation of the ground model.
(D) the moisture content of the soil was determined on the basis of the information on density of the ground comprising soil material, based on the ground state information is information representing a relation between the friction coefficient between the tire model and the ground model Calculating the friction force generated between them.
(E) Recognizing a boundary surface between the tire model after the deformation calculation in the step (b) and the ground model after the deformation calculation in the step (c), and determining the boundary condition regarding the recognized boundary surface The calculation of the steps (b) to (d) is repeated for the tire model and the ground model after being applied to the tire model and the ground model and the friction force is applied to the tire model and the boundary condition is applied. And calculating until deformation of the tire model and the ground model can be regarded as a steady state. A tire design method including the following steps.
(1) A tire model having a pattern shape capable of being deformed by at least one of ground contact and rolling, and at least part of the tire model that is partially or entirely filled with an elastic-plastic material or a material including a plastic material. Determining a ground model in contact with the part.
(2) A step of executing deformation calculation of the tire model.
(3) A step of executing deformation calculation of the ground model.
(4) of the ground calculated based on the information on density of the ground comprising soil material and water content, based on the ground state information is information representing a relation between the friction coefficient between the tire model and the ground model Calculating the friction force generated between them.
(5) Recognizing a boundary surface between the tire model after the deformation calculation in the step (2) and the ground model after the deformation calculation in the step (3), the boundary condition relating to the recognized boundary surface is The calculation of the steps (2) to (4) is repeated for the tire model and the ground model after being given to the tire model and the ground model and the frictional force is given to the tire model and the boundary condition is given. And calculating until deformation of the tire model and the ground model can be regarded as a steady state.
(6) A step of obtaining a physical quantity generated in at least one of the tire model and the ground model in the step (3) or the step (5).
(7) Predicting tire performance in the ground based on the physical quantity.
(8) A step of correcting the tire model in consideration of the tire performance.
(9) A step of repeatedly calculating the tire model after the correction in step (8) in consideration of the tire performance as a result of executing steps (2) to (7). .
(10) A step of designing a tire based on the tire model of the calculation result in the step (9). A recording medium recording a tire performance prediction program for predicting tire performance by a computer, the recording medium recording a tire performance prediction program characterized by including the following steps.
(A) a tire model having a pattern shape that can be deformed by at least one of ground contact and rolling, and an elastoplastic body or a material that includes at least a plastic body, and a part or all of the tire model is at least Determining a ground model in contact with the part.
(B) A step of performing deformation calculation of the tire model.
(C) A step of executing deformation calculation of the ground model.
(D) and the moisture content of the soil was determined on the basis of the information on density of the ground comprising soil material, based on the ground state information is information representing a relation between the friction coefficient between the tire model and the ground model Calculating the friction force generated between them.
(E) Recognizing a boundary surface between the tire model after the deformation calculation in the step (B) and the ground model after the deformation calculation in the step (C), and determining the boundary condition regarding the recognized boundary surface The calculation of the steps (B) to (D) is repeated for the tire model and the ground model after being given to the tire model and the ground model and the friction force is given to the tire model and the boundary condition is given. And calculating until deformation of the tire model and the ground model can be regarded as a steady state. A tire performance prediction program comprising the following steps for predicting tire performance by a computer.
(I) a tire model having a pattern shape capable of being deformed by at least one of ground contact and rolling, and at least part of the tire model that is partially or entirely filled with an elastic-plastic material or a material including a plastic material. Determining a ground model in contact with the part.
(II) A step of executing deformation calculation of the tire model.
(III) A step of executing deformation calculation of the ground model.
And moisture content of the soil was determined on the basis of the information on density of the ground comprising (IV) soil material, based on the ground state information is information representing a relation between the friction coefficient between the tire model and the ground model Calculating the friction force generated between them.
(V) Recognizing a boundary surface between the tire model after the deformation calculation in the step (II) and the ground model after the deformation calculation in the step (III), the boundary condition regarding the recognized boundary surface is The calculation of the steps (II) to (IV) is repeated for the tire model and the ground model after being given to the tire model and the ground model and the frictional force is given to the tire model and the boundary condition is given. And calculating until deformation of the tire model and the ground model can be regarded as a steady state.

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