JP5785457B2 - Prediction method of tire durability - Google Patents

Description

  The present invention relates to a tire durability prediction method using a computer, and more particularly to a method capable of accurately predicting a damage occurrence location.

  In recent years, various methods for simulating tire durability using a computer have been proposed. In the conventional method, a tire model obtained by discretizing a tire with a finite number of elements is input to a computer, a predetermined load and internal pressure are applied to the tire model, a deformation state is calculated, and a deformed tire model is obtained. For example, a physical quantity such as a distortion of an element of a code model obtained by modeling a code material is obtained, and a portion having a large distortion is predicted as a damage occurrence portion. Related literature includes:

JP 2005-1649 A JP 2006-240540 A

  By the way, in the conventional simulation, a damage occurrence location is predicted based on the value of tensile strain, maximum principal strain or shear strain as strain. However, as a result of various experiments by the inventors, it has been found that the damage occurrence location predicted by such a simulation method and the actual tire damage occurrence location do not match, and there is a large deviation between the two. .

  As a result of intensive studies, the inventors have found that a large bending deformation and load act on the bead portion of the tire during running, and the cord material of the carcass ply and the reinforcing layer that extends in the bead portion, There is a position where the compressive strain along the longitudinal direction of the cord acts locally, and it has been found that the damage is concentrated at a location where the compressive strain is large, and the present invention has been completed.

  As described above, the present invention obtains the compressive strain along the longitudinal direction of each element of the code model obtained by modeling the code material, and predicts the damage occurrence location in the analysis target region based on the size of the compressive strain. The main purpose is to provide a method for predicting the durability of a tire that can accurately predict the location where damage has occurred.

The invention according to claim 1 of the present invention is a method for predicting the durability of a tire reinforced with a cord material by using a computer, wherein the cord material is modeled by a finite number of elements in the computer. A model setting step for inputting a tire model including a coded model, a deformation calculation step for calculating a deformation of the tire model by applying a predetermined internal pressure and load to the tire model, and the computer, An acquisition step of acquiring a compressive strain along the longitudinal direction of each element of the code model included in a predetermined analysis target region from the deformation calculation step, and a temperature of each element of the code model; but multiplied by a coefficient to each of the obtained compressive strain and temperature, main value of the parameter is the maximum containing them The characterized in that it comprises a prediction step of predicting a damage occurrence place of the analysis target area.

  In the present invention, a model setting step for inputting a tire model including a code model in which a code material is modeled by a finite number of elements to the computer, and the computer applies an internal pressure and a load predetermined to the tire model. A deformation calculation step for causing the tire model to perform deformation calculation, and the computer applies a compressive strain along the longitudinal direction of the code of each element of the code model included in the analysis target region predetermined from the deformation calculation step. An acquisition step of acquiring, and a prediction step of predicting a damage occurrence location in the analysis target area based on the acquired magnitude of the compression strain.

  According to such a method, the compressive strain along the longitudinal direction of each element of the code model can be obtained, and the damage occurrence location in the analysis target region can be predicted based on the magnitude of the compressive strain. Can be accurately predicted.

It is a perspective view of the computer apparatus used by this embodiment. It is a flowchart which shows an example of the process sequence of this embodiment. It is a perspective view which visualizes and shows an example of a tire model. FIG. (A) is a partial perspective view of a carcass ply, (b) is a perspective view of a carcass ply model. It is a calculation result about the tire model of an example, and is a graph showing distortion of a code model in each position of a bead part. It is a flowchart which shows the process sequence of a prediction step. It is sectional drawing of the bead part which shows the damage generation | occurrence | production location estimated by the simulation of the Example, and the actual vehicle damage location. It is sectional drawing of the bead part which shows the damage generation | occurrence | production location estimated by the simulation of the prior art example, and the actual vehicle damage location.

  FIG. 1 shows a perspective view of a computer apparatus 1 for carrying out a prediction method using the durability of the tire according to the present embodiment. The computer device 1 includes a main body 1a, a keyboard 1b, a mouse 1c, and a display device 1d. Although not shown, the main body 1a is appropriately provided with an arithmetic processing unit (CPU), a ROM, a working memory, a mass storage device, disk drives 1a1, 1a2, and the like. The mass storage device (storage medium) stores a part of a processing procedure (program) for executing a method to be described later.

  FIG. 2 shows an example of the processing procedure of this embodiment. First, in this embodiment, a tire model is input to the computer apparatus 1 (step S1).

  3 is a perspective view of the tire model 2 visualized, and FIG. 4 is a cross-sectional view including the tire rotation axis. The tire model 2 is modeled three-dimensionally by dividing a pneumatic tire to be analyzed (whether or not it actually exists) into finite and small elements 2a, 2b, 2c. Each of the elements 2a, 2b, 2c,... Is, for example, a triangular or quadrangular membrane element as a two-dimensional plane, and, for example, a tetrahedral to hexahedral solid element is used as a three-dimensional element. The tire model 2 of the present embodiment is modeled so that the two-dimensional cross-sectional shape shown in FIG. 4 is transferred in the tire circumferential direction and the same cross-sectional shape is continuous in the tire circumferential direction.

  The elements 2a, 2b, 2c,... Are composed of numerical data that can be deformed and handled by the computer device 1, and the node numbers, coordinate values, element shapes, material properties, etc. of each element are defined and the computer Input to the device 1.

  Examples of the deformation calculation include a finite element method, a finite volume method, and a difference method. The material characteristics include, for example, the density, complex elastic modulus, and / or loss tangent of the material expressed by the element. In the present embodiment, Lagrange elements that move in space with the deformation of the object (model) are used for the elements 2a, 2b, 2c,.

  As shown in FIG. 4, the tire model 2 includes a tread portion model 2T in which a tire tread portion is modeled and is in contact with a road surface, and a pair of sidewall portion models 2S in which tire sidewalls are modeled, And a bead portion model 2B connected to the inner ends thereof. In order to increase the calculation accuracy, it is desirable that the tread part model 2T of the tire model 2 is modeled with a tread pattern including vertical grooves extending in the tire circumferential direction.

  Further, the tire is reinforced with various cord materials such as a carcass ply constituting the skeleton, a belt ply disposed on the tread portion of the carcass ply in the tire radial direction, and a bead reinforcement ply disposed on the bead portion. The tire model 2 of the present embodiment also includes a carcass ply model 3 and a belt ply model 4 in which at least the carcass ply and the belt ply are modeled. The carcass ply model 3 of the present embodiment is folded around the bead core model 5 that models the bead core from the inner side to the outer side in the tire axial direction.

  FIG. 5 (a) shows a partial perspective view of a carcass ply f constituting a carcass as an example, and FIG. 5 (b) shows a carcass ply model 3 equivalent to the carcass ply model 3 visualized and disassembled. The carcass ply f includes a code array c in which a plurality of carcass cords c1 are arranged in parallel, and a topping rubber t that covers the code array c.

  As shown in FIG. 5B, the carcass ply model 3 in which the carcass ply f is modeled has, for example, a large tensile elastic modulus in the longitudinal direction of the carcass cord c1 and a tensile elastic modulus in a direction perpendicular to the longitudinal direction. The carcass cord model 3a is composed of a shell element in which small anisotropy is defined, and the topping rubber model 3b is composed of, for example, a three-dimensional solid element disposed on both sides thereof. The carcass ply model 3 may be replaced with a single shell element including the topping rubber and the cord array c.

  Although not shown, the belt ply is modeled in the same manner as the carcass ply model 3. In addition, the portions where the cords of the carcass ply model 3 and the belt ply model 4 are modeled may be collectively referred to as a cord model C.

  Next, a road surface model is input to the computer apparatus 1 (step S2). As visualized in FIG. 3, the road surface model 6 is set to have a width and a length with which the tire model 2 can contact. The road surface model 6 of this embodiment is formed of a rigid element that does not deform even when an external force is applied.

  Next, boundary conditions are set in the computer apparatus 1 (step S3). The boundary conditions to be set include various conditions necessary for calculating the deformation by bringing the tire model 2 into contact with the road surface model 4. For example, in the case of static deformation calculation (grounding simulation), the internal pressure condition, rim condition, load load condition, camber angle, etc. of the tire model 2 are included. On the other hand, in the case of dynamic deformation calculation (rolling simulation), in addition to the above conditions, the slip angle of the tire model 2, the traveling speed, and / or the friction coefficient between the tire model 2 and the road surface model 4, etc. Is included.

  Next, as shown in FIG. 3, the computer apparatus 1 performs deformation calculation of the tire model by applying the internal pressure and the load to the tire model 2 and bringing it into contact with the road surface model 6 (step S <b> 4). In the present embodiment, as this deformation calculation, a grounding simulation is performed in which the tire model 2 is statically grounded to the road surface model 6 without rolling. In the deformation calculation, the element mass matrix, stiffness matrix, and damping matrix are created based on the element shape and material properties (eg density, elastic modulus, damping coefficient), etc. Is created. Then, an equation of motion is created by applying the above various conditions, and this is performed by sequentially calculating the equation with a small time increment Δt in the computer device 1.

  Next, the computer apparatus 1 obtains a physical quantity including a compressive strain along the code longitudinal direction of each element of the code model C included in the predetermined analysis target region from the deformation calculation (step S4). (Step S5).

  The analysis target region is a region including a portion where damage is expected to occur with respect to the durability of the tire model 2 (in other words, the pneumatic tire to be evaluated). For example, the bead portion, the sidewall portion, or the tread A region such as a section is preset. This analysis target area is determined according to the internal structure of the tire, the category, the load condition, and the like, and further based on past experiments and empirical rules. In order to reduce the calculation cost, the analysis target region is preferably a partial region of the tire model 2, but the entire tire model 2 may be designated. When a part of the tire model 2 is set as the analysis target area, the target element is specified and input to the computer device 1 in advance. In the present embodiment, a bead portion model 2B is set in the tire model 2 as the analysis target region.

  Further, in the present invention, the computer device 1 causes the code longitudinal direction of each element of the code model C (that is, the carcass ply model 3 of the carcass ply model 3 in this example) included in the bead part model 2B that is the analysis target region. Along the compression strain along.

  FIG. 6 is a graph showing each distortion of the 25 elements of the carcass code model 3a included in the bead part model 2B. In this embodiment, since the simulation is a static simulation, the distortion varies depending on the circumferential position of the element. The distortion in FIG. 6 is at the center position of the grounding portion. In addition, the vertical axis indicates strain (minus indicates compression), and the horizontal axis indicates the distance in the tire radial direction from the inner surface BL of the bead core model 5.

  Further, in FIG. 6, the black plot shows the strain in the inflated state in which the tire model is filled with only the internal pressure, and the white plot shows the strain in the inflated state with a load applied. Each is shown. In the present embodiment, the computer apparatus 1 stores, in the memory or the storage device, the value of the distortion in the longitudinal direction of the code of the element calculated at the time of inflation and load application close to the actual running state for each element.

  Next, in the present invention, the computer device 1 performs a prediction step of predicting a damage occurrence location in the analysis target region based on the acquired magnitude of the compression strain (step S6). In the prediction step, as shown in FIG. 7, the compression distortion of each element of the acquired code model C is examined, the element having the maximum size is identified (step S51), and the identified element is damaged. The occurrence location is displayed on the display device 1d or the like (step S52). Such a prediction step can predict the occurrence of damage in the analysis target area based on the magnitude of the compressive strain along the longitudinal direction of the code of each element of the code model C. Prediction with good correlation becomes possible.

  In FIG. 8, a damage occurrence place generated in the bead portion when the drum endurance test is performed on the pneumatic tire to be analyzed is indicated by reference sign A, and a damage occurrence place predicted in the present embodiment is indicated by reference sign B. Yes. In the method of the present embodiment, it can be confirmed that the prediction having a very good correlation with the damage caused by the actual traveling is possible.

  On the other hand, in FIG. 9, a damage occurrence portion predicted from an element maximizing the tensile strain in a rubber model obtained by modeling rubber is indicated by a symbol B ′. It can be confirmed that the damage occurrence location B ′ is greatly deviated from the actual damage occurrence location A.

  The present invention is not limited to the above embodiment, and various modifications can be made. For example. In the obtaining step (step S5), the temperature of each element of the code model C included in the predetermined analysis target region can be further obtained from the deformation calculation (step S4). In the prediction step (step S6), a damage occurrence location in the analysis target region can be predicted based on the acquired compressive strain and temperature. For example, an element having the maximum sum of compressive strain and temperature, and a parameter obtained by multiplying each physical quantity by a coefficient and adding them can be used to determine the element having the maximum value as a damage occurrence location.

1 Computer device 2 Tire model 3 Carcass ply model 4 Belt ply model C Code model

Claims (1)

A method for predicting the durability of a tire reinforced with a cord material using a computer,
A model setting step of inputting a tire model including a code model in which the code material is modeled by a finite number of elements to the computer;
A deformation calculation step in which the computer applies a predetermined internal pressure and load to the tire model to calculate deformation of the tire model;
The computer acquires the compressive strain along the code longitudinal direction of each element of the code model included in the predetermined analysis target region from the deformation calculation step and the temperature of each element of the code model. When,
The computer, the multiplying the obtained coefficients respectively to the compression Ibitsu及beauty temperature, and characterized in that the value of the parameters including them and a prediction step of predicting the maximum element as damage occurrence place of the analysis target area Of tire durability.

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