Tire simulation method and tire simulation device

Abstract

To provide a tire simulation method and a tire simulation device capable of shortening a calculation time of crack development.SOLUTION: The tire simulation method includes a tire model acquiring step ST01 of acquiring a tire model including a viscoelastic part in which viscoelastic characteristics are defined and used for analysis of a ground contact state of a tire, a tire model deformation calculating step ST02 of calculating deformation of the tire model in a predetermined analysis section when the tire contacts the ground with a predetermined load in a static state, a tire part model acquiring step ST03 of analyzing a part of the tire model, a tire part model deformation calculating step ST04 of performing calculation based on the deformation of the tire model, a crack growth model generating step ST07 of generating a crack growth model in which a base point of a crack is defined on the tire part model, and a crack growth analyzing step ST08 of calculating deformation of the crack growth model based on the deformation of the tire part model and analyzing growth.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a tire simulation method and a tire simulation device, and more particularly to a tire simulation method and a tire simulation device that can reduce the calculation time for crack growth. [Background technology]

[0002] In recent years, tire simulation methods and tire simulation devices have been proposed for reproducing the progression of cracks in tires. As such a conventional tire simulation method and tire simulation device, the technology described in Patent Document 1 is known. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-1361 Summary of the Invention [Problem to be solved by the invention]

[0004] However, conventional tire simulation methods and tire simulation devices have a problem in that analyzing crack growth requires an extremely long calculation time.

[0005] The present invention has been made in view of the above, and has an object to provide a tire simulation method and a tire simulation device that can reduce the time required to calculate crack growth. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the tire simulation method of the present invention is a tire simulation method for predicting the progression of cracks that occur in a tire, and is characterized by including: a tire model acquisition step for acquiring a tire model that includes a viscoelastic portion having defined viscoelastic properties and is used to analyze the tire's contact state; a tire model deformation calculation step for calculating the deformation of the tire model in a predetermined analysis section when the tire is in a stationary state and contacts the ground under a predetermined load, including creep deformation of the viscoelastic portion; a tire part model acquisition step for acquiring a tire part model that is used to analyze a part of the tire model; a tire part model deformation calculation step for calculating the deformation of the tire part model based on the deformation of the tire model; a crack progression model generation step for generating a crack progression model that defines a base point of a crack on the tire part model; and a crack progression analysis step for calculating the deformation of the crack progression model based on the deformation of the tire part model to analyze crack progression.

[0007] Moreover, a tire simulation device according to the present invention is a tire simulation device that predicts the progression of cracks that occur in a tire, and is characterized by including: a tire model acquisition unit that acquires a tire model that includes a viscoelastic part having defined viscoelastic properties and is used to analyze the ground contact state of the tire; a tire model deformation calculation unit that calculates the deformation of the tire model in a predetermined analysis section when the tire is in a stationary state and contacts the ground under a predetermined load, including creep deformation of the viscoelastic part; a tire part model acquisition unit that acquires a tire part model for analyzing a part of the tire model; a tire part model deformation calculation unit that calculates the deformation of the tire part model based on the deformation of the tire model; a crack progression model generation unit that generates a crack progression model that defines a base point of a crack on the tire part model; and a crack progression analysis unit that calculates the deformation of the crack progression model based on the deformation of the tire part model to analyze crack progression. [Effects of the Invention]

[0008] This tire simulation method and tire simulation device analyze crack progression using a crack progression model that defines the crack's base point on a tire part model, which is a local model. This has the advantage of shortening the calculation time for crack progression compared to a configuration that defines the crack's base point on a tire model, which is a global model, and analyzes crack progression using the tire model. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a functional block diagram showing a tire simulation device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a flowchart showing a tire simulation method. [Figure 3] FIG. 3 is an explanatory diagram showing the tire simulation method described in FIG. [Figure 4] FIG. 4 is an explanatory diagram showing the tire simulation method described in FIG. [Figure 5] FIG. 5 is an explanatory diagram showing the tire simulation method described in FIG. [Figure 6] FIG. 6 is an explanatory diagram showing the tire simulation method described in FIG. [Figure 7] FIG. 7 is an explanatory diagram showing the tire simulation method shown in FIG. [Figure 8] FIG. 8 is an explanatory diagram showing the tire simulation method described in FIG. [Figure 9] FIG. 9 is an explanatory diagram showing the tire simulation method described in FIG. [Figure 10] FIG. 10 is an explanatory diagram showing the tire simulation method described in FIG. [Figure 11] FIG. 11 is an explanatory diagram showing the tire simulation method described in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described in detail below with reference to the drawings. However, the present invention is not limited to these embodiments. Furthermore, the components of these embodiments include those that can be substituted and are obvious substitutes while maintaining the identity of the invention. Furthermore, the multiple modifications described in these embodiments can be arbitrarily combined within the scope obvious to those skilled in the art.

[0011] [Tire simulation device] FIG. 1 is a functional block diagram showing a tire simulation device according to an embodiment of the present invention.

[0012] The tire simulation device 1 is a device that executes a tire simulation for predicting the progression of cracks that occur in a tire, and includes a processing device 2, an input device 3, and a display device 4.

[0013] The processing device 2 is, for example, a PC (Personal Computer), and has a CPU (Central Processing Unit) 21, a RAM (Random Access Memory) 22, and a ROM (Read-Only Memory) 23. The processing device 2 is also connected to an external input device 3 and display device 4 via an input / output unit 24. The ROM 23 stores various programs 23a to 23i, which will be described later. The input device 3 is a device for inputting input data, such as conditions required to execute a tire simulation, into the processing device 2, and is composed of, for example, a keyboard and a mouse. The display device 4 is a device for displaying a condition input screen, created simulation results, and the like, and is composed of, for example, a PC monitor.

[0014] In this tire simulation device 1, the CPU 21 of the processing device 2 temporarily stores input data from the input device 3, various data read from the ROM 23, and the like in the RAM 22. The CPU 21 also reads and executes various programs 23a to 23i stored in the ROM 23 while referring to these data as necessary. The CPU 21 also displays the created simulation results and the like on the display device 4. In this way, various functions of the tire simulation device 1 are realized.

[0015] [Tire simulation method] FIG. 2 is a flowchart showing a tire simulation method. FIGS. 3 to 11 are explanatory diagrams showing the tire simulation method described in FIG. 2. In these figures, FIG. 3 shows a tire model 10, which is a global model; FIG. 4 shows a two-dimensional model 101 of the tire model 10 in a cross-sectional view in the tire meridian direction; FIG. 5 shows a tire part model 11, which is a local model; FIG. 6 shows a two-dimensional model 111 of the tire part model 11 in a cross-sectional view in the tire meridian direction; FIG. 7 shows the difference in logarithmic strain before and after relaxation; FIG. 8 shows the strain of the tire part model 11 in the groove width direction when the tire is stationary; FIG. 9 shows a crack propagation model 12; FIG. 10 shows a base point 122a of a crack 122 defined in the crack propagation model 12; and FIG. 11 shows an example of an analysis result of the propagation of the crack 122. Here, as an example, a tire simulation method for predicting the propagation of a crack occurring at the groove bottom of a circumferential groove 20 formed on a tread surface will be described.

[0016] In the tire model acquisition step ST01, the tire model acquisition unit 23a acquires the tire model 10 (see FIG. 3), which is a global model. At this time, the tire model acquisition unit 23a may acquire the tire model 10 by reading a data file of an existing tire model 10, or may generate and acquire a new tire model 10.

[0017] The tire model 10 is a three-dimensional model constructed using the finite element method (FEM) and includes information such as the tire's geometric shape, material properties (elastic modulus, density, and particularly viscoelastic properties), and groove shape. This tire model 10 is used to numerically analyze the physical behavior of the tire (e.g., stress, strain, displacement, particularly creep deformation) when the tire is stationary. The tire model 10 also includes a viscoelastic portion (reference numeral omitted in the figure) whose viscoelastic properties are defined. This viscoelastic portion is defined using a Prony series or a nonlinear viscoelastic model. The viscoelastic portion is located in a region where cracks develop due to creep deformation when the tire is in contact with the ground under a constant load. To ensure uniform stress distribution, the tire model 10 is preferably composed of hexahedral elements. For example, a two-dimensional model 101 (see FIG. 4) of the tire model 10 in a cross-sectional view taken along the tire meridian is generated, and then this two-dimensional model 101 is rotated around the tire rotation axis to generate a three-dimensional tire model 10 representing the entire tire.

[0018] In tire model deformation calculation step ST02, the tire model deformation calculation unit 23b calculates the deformation of the tire model 10 (see FIG. 3) in the analysis section T described below when the tire is in stationary contact with the ground under a predetermined load. The deformation of the tire model 10 particularly includes the displacement at each point on the tire, the stress and strain of the rubber material caused by the tire deformation, and the overall shape of the tire before and after deformation. The deformation of the tire model 10 also includes the creep deformation of the viscoelastic portion described above. Specifically, the tire deformation may be calculated based on test results obtained by actually contacting a test tire with the ground under a predetermined load in a stationary state, or by recreating a virtual contact state based on coordinate information in tire contact analysis.

[0019] In the tire part model acquisition step ST03, the tire part model acquisition unit 23c acquires the tire part model 11 (see FIG. 5), which is a sub-model. At this time, the tire part model acquisition unit 23c may acquire the tire part model 11 by reading a data file of an existing tire part model 11, or may acquire the tire part model 11 by generating a new tire part model 11.

[0020] The tire part model 11 is a three-dimensional model representing a specific tire part, and includes information such as the geometric shape and material properties (elastic coefficient, density, and viscoelastic properties of rubber) of the tire part. This tire part model 11 is used for detailed numerical analysis of a portion of the physical behavior of the tire model 10 (e.g., stress, strain, displacement, and particularly creep deformation). The tire part model 11 also includes a viscoelastic portion (reference numeral omitted in the figure) whose viscoelastic properties are defined. To ensure uniform stress distribution, the tire part model 11 is preferably composed of hexahedral elements. For example, a two-dimensional model 111 (see FIG. 6 ) of the tire part model 11 in a cross-sectional view in the tire meridian direction is generated, and the three-dimensional tire part model 11 is generated by expanding this two-dimensional model 111 in the tire circumferential direction. The tire part model 11 also preferably reproduces portions made of the same rubber material. This prevents a decrease in the calculation accuracy of crack propagation at the interface between different rubber components.

[0021] In this embodiment, each of the tire model 10 and the tire part model 11 includes the above-described viscoelastic portion. However, this is not limiting, and the viscoelastic portion may be defined in at least a part of the above-described tire model 10, and the tire part model 11 may not include a viscoelastic portion.

[0022] The mesh size of the tire part model 11 is smaller than the mesh size of the tire model 10. The mesh size of the tire part model 11 is preferably in the range of 0.0001 mm to 0.20 mm. The lower limit prevents an increase in analysis costs, and the upper limit prevents adverse effects when modeling the base points of cracks, which will be described later.

[0023] For example, in this embodiment, the tire part model 11 reproduces the rubber portion constituting the groove wall and groove bottom of the circumferential groove 20 (see FIG. 3) formed on the tread surface, more specifically, a portion of the cap rubber forming the tread surface. The groove length Lp (see FIG. 5) of the tire part model 11 is in the range of 3 mm to 30 mm. The lower limit ensures the groove length Lp of the tire part model 11, ensuring the analytical accuracy of the crack propagation described below. The upper limit prevents an increase in calculation time due to excessive model size. The groove gauge Gp (see FIG. 6) of the tire part model 11 is preferably in the range of 0.7 mm or greater and thinner than the thickness of a portion made of the same rubber material. The lower limit prevents the model from being divided before the crack propagates, resulting in a decrease in calculation accuracy. The upper limit prevents an increase in calculation time due to excessive model size.

[0024] The groove length Lp of the tire part model 11 is measured as the maximum length of the tire part model 11 in the groove length direction.

[0025] The groove bottom gauge Gp of the tire part model 11 is measured as the thickness of the groove bottom of the tire part model 11 on the groove center line.

[0026] In this embodiment, as described above, the tire part model 11 reproduces the rubber portions that form the groove walls and groove bottoms of the circumferential grooves 20 (see FIG. 3) formed on the tread surface. This configuration is preferable because it can shorten the analysis time for cracks at the groove bottoms, which take time to propagate. However, the present invention is not limited to this. The tire part model 11 may also reproduce the rubber portions that form the groove walls and groove bottoms of lug grooves (not shown) formed on the tread surface, or may reproduce bead fillers (not shown), which are rubber members that reinforce the bead portions of the tire.

[0027] In tire part model deformation calculation step ST04, tire part model deformation calculation unit 23d calculates the deformation of tire part model 11 (see FIG. 5) based on the deformation of tire model 10 (see FIG. 3). Specifically, the deformation data of tire model 10 calculated in step ST02 is used to match boundary conditions and map stress and deformation data, thereby calculating the deformation of tire part model 11, particularly creep deformation. The deformation of tire part model 11 also includes, in particular, the displacement at each point of the tire part, the stress and strain of the rubber material caused by the deformation of the tire part, and the shape of the entire tire part before and after deformation.

[0028] For example, in this embodiment, as shown in FIG. 5, the tire part model 11 is a rubber portion constituting the groove wall and groove bottom of a circumferential groove 20 (see FIG. 3) formed on the tread surface, and has a uniform cross section in the groove length direction. Therefore, the deformation of the tire part model 11 when the circumferential groove 20 creeps while the tire is stationary is calculated, and the logarithmic strain in at least the groove width direction is calculated. In addition, the logarithmic strain difference in the groove width, i.e., the difference between the logarithmic strain before and after stress relaxation in the groove width direction, is calculated. FIG. 7 shows the logarithmic strain in the groove width direction of the tire part model 11 before and after stress relaxation (i.e., the end and start points of the analysis section T) when the tire is pressed against the ground contact patch with a constant load while in a stationary state and a predetermined analysis section T has elapsed. As shown in the figure, the logarithmic strain difference is maximum at a circumferential angle of 180°, so it is preferable to calculate the logarithmic strain difference in a region including at least the circumferential angle of 180°. The circumferential angle is defined as the position around the tire circumferentially, with the center of the tire contact patch when the tire is in contact with the ground as 0°, and a position with a circumferential angle of 180° corresponds to the vertical peak of the tire.

[0029] In the analysis interval determination step ST05, the analysis interval determination unit 23e determines an analysis interval T for analyzing crack propagation. When the creep deformation of the viscoelastic portion described above is periodically repeated, the analysis interval T is defined as a section of one or more cycles of the creep deformation. Furthermore, from the viewpoint of providing physical meaning, the analysis interval T is preferably a multiple integer number of cycles. Furthermore, the analysis interval T is determined taking into consideration the driving state of the vehicle equipped with the tire. For example, when considering a so-called "Sunday driver" who drives a car only on weekends, the analysis interval T is set to one week. Furthermore, as long as the deformation of the tire part model 11, particularly the creep deformation, is the same, the analysis interval T may differ from the actual elapsed time. Furthermore, the analysis interval T is selected from a stable section obtained by analyzing a certain number of preliminary sections, as shown in FIG. 8. Note that FIG. 8 shows the vertical position coordinates of a predetermined point on the tire circumference, and also shows multiple extracted sections from after stress relaxation to before stress relaxation when the creep deformation of the viscoelastic portion described above is periodically repeated.

[0030] In initial shape extraction step ST06, initial shape extraction unit 23f extracts the initial shape of tire part model 11 in the analysis section T determined in step ST05. In this embodiment, as described above, tire part model 11 is the rubber portion that constitutes the groove wall and groove bottom of circumferential groove 20 (see FIG. 3 ) formed on the tread surface, and therefore the initial shape of circumferential groove 20 in the analysis section T is extracted.

[0031] In the crack propagation model generating step ST07, the crack propagation model generating unit 23g generates the crack propagation model 12 (see FIG. 9).

[0032] As shown in FIG. 9, the crack propagation model 12 is a three-dimensional model that defines a base point 122a (see FIGS. 9 and 10) of a crack 122 on the tire part model 11 (see FIG. 5), which is a local model. The crack propagation model 12 is used to numerically analyze the propagation of the crack 122 when the tire is stationary. The base point 122a of the crack 122 reproduces an initial crack that occurs in the tire and is defined using the extended finite element method. This allows the crack propagation to be modeled independently of the mesh shape of the crack propagation model 12, and also reduces the time required for creating the model and for analysis. The base point 122a of the crack 122 may be defined, for example, by (1) directly modeling the crack, (2) setting the elastic modulus of some elements of the crack propagation model 12 to be greater than the elastic modulus of other elements, or (3) setting the failure criterion of some elements of the crack propagation model 12 to be smaller than the failure criterion of other elements.

[0033] Furthermore, the ratio R of the maximum to minimum mesh sizes of the elements constituting the crack propagation model 12 is in the range of 1.0≦R≦1.5. The mesh size of the crack 122, i.e., the mesh size of the base point 122a of the crack 122 and the area where the propagation of the crack 122 is predicted, is set to be approximately the same as the mesh size of the other elements in the area surrounding the crack 122. Specifically, the mesh size of the crack 122 is in the range of 0.67 to 1.5 times, and preferably in the range of 0.90 to 1.10 times, the mesh size of the other elements in the area surrounding the crack 122. This configuration is preferable in that it shortens the modeling time compared to conventional configurations in which the mesh size of the crack is set small.

[0034] The mesh size of an element is measured as the average length of each side. The mesh size of a hexahedral element is also measured as the average length of each side.

[0035] Furthermore, the base point 122a of the crack 122 is placed in the center of the crack propagation model 12, and is also placed at a position where the strain amplitude is large when the tire is stationary. This makes it easy to evaluate the propagation of the crack. Furthermore, multiple base points 122a of the crack 122 may be set (not shown).

[0036] For example, in the configuration of Fig. 6, the crack propagation model 12 is used to analyze the propagation of cracks on the groove walls and groove bottoms of the circumferential grooves 20 (see Fig. 3) formed on the tread surface as described above. Also, the base point 122a of the crack 122 is located at the center of the crack propagation model 12 in the groove length direction.

[0037] Furthermore, positions on the surfaces of the groove wall and groove bottom where the strain amplitude is large are selected as follows: That is, in step ST04 described above, the deformation of the tire part model 11 in the analysis section T is calculated, and based on this calculation result, the logarithmic strain difference in the groove width direction before and after stress relaxation (see FIG. 7) is calculated. Positions P1 and P2 where the logarithmic strain difference in the groove width direction in FIG. 7 is maximized are then selected as positions on the surfaces of the groove wall and groove bottom where the strain amplitude is large. In particular, it is preferable to locate the base point 122a of the crack 122 at position P1 where the strain amplitude is maximized on the compression side.

[0038] Furthermore, in modeling the crack propagation model 12, material parameters for reproducing the speed of crack propagation are determined so as to be able to reproduce experiments using test tires or test specimens, thereby enabling evaluation of groove bottom cracks based on strain amplitude.

[0039] For example, material parameters for reproducing the rate of crack propagation are determined as follows: First, a test method conforming to standards such as ASTM E647 is applied to a test specimen made of a rubber material to determine the stress intensity factor. Alternatively, the tear energy is calculated as the product of the energy (corresponding to the area of ​​the stress-strain diagram) and the strain when the test specimen is pulled vertically, and the test specimen is modeled using the finite element method to match the test results, and the stress intensity factor is determined. Alternatively, material parameters may be set so that crack propagation based on the cumulative inelastic hysteresis energy can be evaluated.

[0040] In crack propagation analysis step ST08, the crack propagation analysis unit 23h numerically analyzes the propagation of the crack 122 when the tire is stationary, using the crack propagation model 12 (see FIG. 9) generated in step ST06. Specifically, boundary conditions and stress and deformation conditions that affect the propagation of the crack 122 are extracted from the deformation data of the tire part model 11 (see FIG. 5) calculated in step ST04. Then, based on these conditions, the deformation of the crack propagation model 12 is calculated and the propagation of the crack 122 is analyzed. In addition, the extended finite element method is used to calculate the propagation of the crack 122. This makes it possible to efficiently and accurately analyze the behavior of the crack 122 without regenerating a mesh as the crack 122 propagates.

[0041] Furthermore, one or more analysis intervals T are defined as one cycle, and the crack propagation model 12 is deformed for a predetermined number of cycles according to a predetermined failure criterion, and the propagation of the crack 122 is analyzed. The direct cyclic analysis method is also used. The direct cyclic analysis method is a computationally efficient modeling technique for determining the stable response of a structure subjected to repeated loads, and is suitable for performing low-cycle fatigue calculations on large-scale structures. This direct cyclic analysis method combines Fourier series and time integration of nonlinear material behavior to directly determine the stable response of the structure.

[0042] In analyzing the propagation of the crack 122, the length, shape, etc. of the crack 122 are calculated. For example, in this embodiment, the deformation of at least the rubber portion constituting the groove wall and groove bottom of the circumferential groove 20 (see FIG. 3) in the groove width direction is calculated, and the propagation of the crack 122 is analyzed using a linear elastic material.

[0043] FIG. 11 is a diagram showing an example of the analysis results of the propagation of crack 122. Here, tire models 1 to 3 having cap rubbers with different physical properties are created. The creep deformation is calculated when a tire with a tire size of 205 / 60R16 is mounted on a 16x6.5 rim and placed in contact with the ground in a static state under a load of 250 kPa and 4.34 kN. The analysis section T, which is equivalent to the case where the tire is placed in contact with the ground for one week and the stress is relaxed, is defined as one cycle, and the amount of crack propagation after 100 cycles is calculated. As the analysis results show, it can be confirmed that the amount of crack propagation differs due to the difference in the viscoelastic properties of the cap rubbers.

[0044] In tire evaluation step ST09, the tire evaluation unit 23i evaluates the quality of the tire based on the analysis results of the propagation of the crack 122 obtained in step ST08. This evaluation may be performed based on the length of the crack 122 after a predetermined number of cycles have been completed, or may be performed based on the number of cycles required for the crack 122 to propagate to a predetermined length. Furthermore, when base points 122a of multiple cracks 122 are set, the evaluation may be performed based on the total length or maximum length of the cracks 122, or may be performed based on the number of cycles required for the total length of the cracks 122 to propagate to a predetermined length.

[0045] [effect] As explained above, [1] this tire simulation method (see FIG. 2) predicts the progression of cracks that occur in tires. The tire simulation method also includes a tire model acquisition step ST01 of acquiring a tire model 10 (see FIG. 3) that includes a viscoelastic portion having defined viscoelastic properties and is used to analyze the tire's contact state with the ground; a tire model deformation calculation step ST02 of calculating the deformation of the tire model, including the creep deformation of the viscoelastic portion, in a predetermined analysis section when the tire is stationary and contacts the ground with a predetermined load; a tire part model acquisition step ST03 of acquiring a tire part model 11 (see FIG. 5) for analyzing a portion of the tire model 10; a tire part model deformation calculation step ST04 of calculating the deformation of the tire part model 11 based on the deformation of the tire model 10; a crack propagation model generation step ST07 of generating a crack propagation model 12 (see FIG. 9) that defines a base point 122a of a crack 122 on the tire part model 11; and a crack propagation analysis step ST08 of calculating the deformation of the crack propagation model 12 based on the deformation of the tire part model 11 to analyze the propagation of the crack 122.

[0046] In this configuration, the propagation of the crack 122 is analyzed using a crack propagation model 12 that defines the base point 122a of the crack 122 on a tire part model 11, which is a local model. This has the advantage of shortening the calculation time for the propagation of the crack compared to a configuration (not shown) that defines the base point of the crack on a tire model, which is a global model, and analyzes the propagation of the crack using the tire model.

[0047] [2] In this tire simulation method (see FIG. 2), in the tire simulation method described in [1] above, in crack propagation analysis step ST08, the crack propagation model 12 is deformed for a predetermined number of cycles according to a predetermined fracture criterion using a direct cyclic analysis method, thereby analyzing the propagation of the crack 122. This has the advantage of enabling efficient analysis of the propagation of the crack 122.

[0048] [3] In this tire simulation method (see FIG. 2), in the tire simulation method described in [1] or [2] above, the tire part model 11 is a model of grooves 20 (see FIG. 3) formed on the tread surface, and the crack propagation model 12 is a model of cracks that occur at the bottom of the grooves 20. This has the advantage of shortening the analysis time for cracks at the bottom of the grooves, which take time to propagate.

[0049] [4] In addition, in this tire simulation method (see FIG. 2), in the tire simulation method described in any one of the above [1] to [3], base point 122a of crack 122 is placed at a position where strain amplitude is maximum on tire part model 11. This has the advantage of making it easier to evaluate the progress of crack 122.

[0050] [5] In addition, this tire simulation method (see FIG. 2) is the tire simulation method according to any one of the above [1] to [4], in which the extended finite element method is used to define the base point 122a (see FIG. 9) of the crack 122. This allows the mesh size of the crack 122 in the crack propagation model 12 to be increased, which has the advantage of shortening the calculation time and modeling time in analyzing the propagation of the crack 122.

[0051] [6] In addition, in this tire simulation method (see FIG. 2), in the tire simulation method described in [5] above, the ratio R of the maximum to minimum mesh sizes of the elements constituting the crack propagation model 12 is in the range of 1.0≦R≦1.5, which has the advantage of being able to reduce the calculation time and modeling time in analyzing the propagation of the crack 122.

[0052] [7] In addition, in this tire simulation method (see FIG. 2), in the tire simulation method according to any one of the above [1] to [6], material parameters for reproducing the speed of propagation of the crack 122 are determined based on experiments using a test tire or a test piece. This has the advantage of enabling evaluation of the crack based on the strain amplitude.

[0053] [8] The tire simulation method (see FIG. 2) is the tire simulation method according to any one of the above items [1] to [7], and includes a tire evaluation step ST09 (see FIG. 2) in which, when creep deformation of the viscoelastic portion is periodically repeated, one or more analysis sections T of the creep deformation are defined as one cycle, and the tire is evaluated based on the length of the crack 122 after a predetermined number of cycles have ended. This has the advantage of enabling the propagation of the crack 122 to be evaluated with high accuracy.

[0054] [9] The tire simulation method (see Fig. 2) is the tire simulation method according to any one of the above [1] to [7], further comprising a tire evaluation step ST09 (see Fig. 2) of defining one or more analysis intervals of creep deformation as one cycle when creep deformation of the viscoelastic portion is repeated periodically, and evaluating the tire based on the number of cycles when the crack 122 has progressed to a predetermined length. This has the advantage of enabling accurate evaluation of the progress of the crack 122.

[0055]

[10] This tire simulation device 1 (see FIG. 1) also predicts the progression of cracks that occur in tires (see FIG. 2). The tire simulation device 1 also includes: a tire model acquisition unit 23a that acquires a tire model 10 (see FIG. 3) that includes a viscoelastic portion having defined viscoelastic properties and is used to analyze the tire's contact state; a tire model deformation calculation unit 23b that calculates the deformation of the tire model in a predetermined analysis section when the tire is stationary and contacts the ground under a predetermined load, including creep deformation of the viscoelastic portion; a tire part model acquisition unit 23c that acquires a tire part model 11 (see FIG. 5) for analyzing a portion of the tire model 10; a tire part model deformation calculation unit 23d that calculates the deformation of the tire part model 11 based on the deformation of the tire model 10; a crack propagation model generation unit 23g that generates a crack propagation model 12 (see FIG. 9) that defines a base point 122a of a crack 122 on the tire part model 11; and a crack propagation analysis unit 23h that calculates the deformation of the crack propagation model 12 based on the deformation of the tire part model 11 to analyze the propagation of the crack 122.

[0056] In this configuration, the propagation of the crack 122 is analyzed using a crack propagation model 12 that defines the base point 122a of the crack 122 on a tire part model 11, which is a local model. This has the advantage of shortening the calculation time for the propagation of the crack compared to a configuration (not shown) that defines the base point of the crack on a tire model, which is a global model, and analyzes the propagation of the crack using the tire model. [Explanation of symbols]

[0057] 1 tire simulation device; 2 processing device; 21 CPU; 22 RAM; 23 ROM; 24 input / output unit; 3 input device; 4 display device; 10 tire model; 101 two-dimensional model; 11 tire part model; 111 two-dimensional model; 12 crack progression model; 122 crack; 122a base point; 20 groove

Claims

1. A tire simulation method for predicting the progression of a crack occurring in a tire, comprising: a tire model acquisition step of acquiring a tire model including a viscoelastic portion having defined viscoelastic properties and used to analyze a tire contact state; a tire model deformation calculation step of calculating deformation of the tire model in a predetermined analysis section when the tire is in a stationary state and comes into contact with the ground under a predetermined load, the deformation including creep deformation of the viscoelastic portion; a tire part model acquisition step of acquiring a tire part model used for analyzing a part of the tire model; a tire part model deformation calculation step of calculating a deformation of the tire part model based on the deformation of the tire model; a crack propagation model generating step of generating a crack propagation model by defining a crack origin on the tire part model; a crack propagation analysis step of calculating the deformation of the crack propagation model based on the deformation of the tire part model and analyzing the propagation of a crack.

2. 2. The tire simulation method according to claim 1, wherein the crack propagation analysis step analyzes the propagation of the crack by deforming the crack propagation model for a predetermined number of cycles according to a predetermined failure criterion using a direct cyclic analysis method.

3. 2. The tire simulation method according to claim 1, wherein the tire part model is a model of a groove formed on a tread surface, and the crack propagation model is a model of a crack occurring at the bottom of the groove.

4. The tire simulation method according to claim 1 , wherein the base point of the crack is positioned at a position on the tire part model where the strain amplitude is maximum.

5. The tire simulation method of claim 1 , wherein an extended finite element method is used to define the origin of the crack.

6. 6. The tire simulation method according to claim 5, wherein a ratio R of a maximum value to a minimum value of mesh sizes of elements constituting the crack propagation model is in the range of 1.0≦R≦1.

5.

7. 2. The tire simulation method according to claim 1, wherein the material parameters for reproducing the speed of crack growth are determined based on experiments using a test tire or a test piece.

8. 2. The tire simulation method according to claim 1, further comprising a tire evaluation step of defining one or more analysis intervals of the creep deformation of the viscoelastic portion as one cycle when the creep deformation of the viscoelastic portion is repeated periodically, and evaluating the tire based on the length of the crack after a predetermined number of cycles have ended.

9. 2. The tire simulation method according to claim 1, further comprising a tire evaluation step of defining one or more analysis sections of the creep deformation of the viscoelastic portion as one cycle when the creep deformation of the viscoelastic portion is repeated periodically, and evaluating the tire based on the number of cycles when the crack has progressed to a predetermined length.

10. A tire simulation device for predicting the progression of cracks occurring in a tire, a tire model acquisition unit that acquires a tire model including a viscoelastic part in which viscoelastic properties are defined and that is used to analyze a tire contact state; a tire model deformation calculation unit that calculates the deformation of the tire model, including the creep deformation of the viscoelastic portion, in a predetermined analysis section when the tire is in a stationary state and comes into contact with the ground under a predetermined load; a tire part model acquisition unit that acquires a tire part model for analyzing a part of the tire model; a tire part model deformation calculation unit that calculates a deformation of the tire part model based on the deformation of the tire model; a crack propagation model generation unit that generates a crack propagation model by defining a base point of a crack on the tire part model; a crack propagation analysis unit that calculates the deformation of the crack propagation model based on the deformation of the tire part model and analyzes the propagation of a crack.

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