JP5743460B2 - How to create a tire model - Google Patents

Description

  The present invention relates to a tire model creation method for numerical analysis of a pneumatic tire.

  When creating an element model used in numerical analysis such as FEM (finite element method) for a pneumatic tire, a skeleton member such as a carcass ply or a belt in the tire is placed on the layer where the member is disposed. There is a method of arranging a membrane element (defined as a line in the 2D model and defined as a plane in the 3D model) having considerable rigidity and anisotropy (for example, see Non-Patent Document 1), but a solid element (2D How to divide the element itself (defined in a plane by a model and defined by a polyhedron in a 3D model) has a high degree of freedom and depends on the know-how of the model creator. Recently, a model creation processing method in which an element is automatically divided after designating a position of a skeleton member has become common, and various processing software is used.

Edited by Hayashi Hayashi, “Composite Materials Engineering”, Nikka Giren Publisher, 1971, ISBN 4-8171-9008-6

  In general, when performing deformation or stress distribution analysis of a tire, for example, an element coordinate system, a direction substantially perpendicular to the skeleton member is a first direction (hereinafter referred to as R direction), and a direction along the skeleton member (tangential direction) Is a second direction (hereinafter referred to as Z direction), and a direction perpendicular to the two directions is defined as a third direction (hereinafter referred to as C direction).

  However, in modeling with conventional processing software, as shown in FIG. 4, the elements of the tire numerical analysis model are created by random automatic division, and each element is defined (the order of connection of the nodes of each element and In order to perform modeling in which the (link direction) is also random, post-processing after calculation requires processing to convert stress and strain to a coordinate system (RCZ coordinate system) suitable for the tire analysis. Become.

  Furthermore, when an anisotropic material (a material whose principal axis does not coincide with the element principal axis) is used as a material model in the tire, in a model in which element division or element definition is performed at random, the material principal axis is used as the element principal axis, for example. It is almost impossible to align in the post direction by post-processing.

  The present invention has been made to solve the above-described problems, and a tire model creation method capable of creating a tire model capable of reducing the time required for numerical analysis of a tire structure as compared with the prior art. The purpose is to provide.

In order to achieve the above object, the invention of claim 1 is a method for creating a mesh model for numerical analysis of a pneumatic tire and an element defining method, which are orthogonal to the tire circumferential direction of a tire model including a skeleton member model therein. The direction along the shape of the skeleton member model in the region from the center portion to the bead portion in the cross section of the direction is divided by a boundary line orthogonal to or substantially orthogonal to the tangent line of the shape of the skeleton member model of the tire model. By dividing the direction perpendicular to the shape of the skeleton member model by a boundary line parallel or substantially parallel to the tangent line, the region is divided into a plurality of elements, and each of all the divided elements is divided. straight and the other as the one the first direction in a direction perpendicular to the tangential direction and the tangent line in the second direction to the first direction and the second direction at the position of said element The direction in which the third direction, the first direction axis, and the second axis, and elements coordinate system to the coordinate system having the axis of the third direction corresponding to the position of the divided respective elements, In each of the element coordinate systems, when defining the element by sequentially connecting a plurality of nodes among the nodes generated by the division, the first node and the second node are directed in the first direction. Defined as a connected node, a second node and a third node are defined as a node connected in the second direction, and a third node and a fourth node are defined in the first direction. A tire model creation method characterized by defining elements defined as nodes connected in the opposite direction , wherein the material principal axis of the skeleton member model coincides with the element principal axis representing each axis of the element coordinate system Tire using non-anisotropic material A tire model generating method for performing the element definition of the element coordinates system when creating a tire model for the analysis of the model.

  According to such a method, the element coordinate system of each divided element can be matched with a coordinate system suitable for tire analysis, and the time required for numerical analysis of the tire structure can be shortened.

  That is, even when the material principal axis does not coincide with the element principal axis as described above, it is only necessary to rotate the element coordinate system so that the element coordinate system of each element becomes a desired direction such as the material principal axis direction in post-processing, The time required for the numerical analysis of the tire structure can be shortened.

  According to the present invention, the time required for numerical analysis of a tire structure can be shortened as compared with the prior art.

It is a flowchart which shows the processing routine of tire model creation and analysis. It is explanatory drawing explaining the model creation method which concerns on this Embodiment. It is explanatory drawing explaining an example of the definition method of an element. It is explanatory drawing explaining the conventional model creation method.

  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 creation of a tire model (analysis model) for tire behavior analysis.

  As an operation of the present embodiment, a processing routine of tire model creation / analysis processing executed by hardware capable of numerical analysis simulation will be described with reference to a flowchart shown in FIG.

  FIG. 1 shows a processing routine for creating and analyzing a tire model.

  In step 100, a design plan (tire shape, structure, material, etc.) of a tire for which a tire model is to be created is determined. This design plan includes design data of a belt or a carcass as a skeleton member. Based on the design data of the skeleton member, a skeleton member model obtained by modeling the skeleton member can be included in the tire model.

  In the next step 102 and step 104, a tire model is created. Hereinafter, the processing of each step will be described in detail.

  In step 102, element division is performed. Element division refers to dividing a tire model into several (finite) small parts (elements). In the present embodiment, as shown in FIG. 2, the direction along the shape of the skeleton member model in the region from the center portion to the bead portion in the cross section in the direction orthogonal to the tire circumferential direction (rotation direction) of the tire model, The tire model is divided by a boundary line orthogonal to or substantially orthogonal to the tangent of the shape of the skeleton member model of the tire model, and the direction orthogonal to the shape of the skeleton member model in the region is divided by a boundary line parallel to or substantially parallel to the tangent line. By doing so, the region is divided into a large number of elements.

  In step 104, the divided elements are defined. First, a local coordinate system suitable for tire analysis is defined as an element coordinate system. Specifically, as shown in FIG. 2, the direction orthogonal to the tangent of the shape of the skeleton member model is the first direction (hereinafter referred to as R direction), the tangential direction is the second direction (hereinafter referred to as Z direction), and the above two directions. A direction orthogonal to the third direction (hereinafter referred to as C direction) is a local coordinate system having an R axis, a Z axis, and a C axis as an element coordinate system of each element. Since the element coordinate system is defined as described above, the orientation of the element coordinate system depends on the position of each element (see element A and element B in FIG. 2).

  Then, when defining each element by sequentially connecting a plurality of nodes among the nodes generated by the element division in step 102, the first node N1 which is the first node and the second node which is the second node N2 is defined as a node connected along the R direction (side by side), and the second node N2 and the third node N3, which is the third node, are defined as nodes connected side by side in the Z direction. . FIG. 2 shows an element having four nodes. As shown in FIG. 2, the first node N1, the second node N2, the third node N3, and the fourth node N4 are connected in this order, and Each element is defined as a node in which the node N1 and the second node N2 are arranged in the R direction, and the second node N2 and the third node N3 are connected in the Z direction.

  Here, the definition method of each element will be described more specifically with reference to FIG. As shown in FIG. 3, when numbers are assigned to the respective nodes, for element 1, the nodes are connected in the order of (101, 102, 112, 111), and the first node 101 and the second node 102 are connected. Are connected side by side in the R direction, and the second node 102 and the third node 112 are defined as nodes connected in parallel in the Z direction. For the element 2, the nodes are connected in the order of (111, 112, 122, 121), and the first node 111 and the second node 112 are connected side by side in the R direction, and the second node 112 and the third node Node 122 is defined as a node connected side by side in the Z direction.

  In the case where a further three-dimensional tire model is created from the two-dimensional tire model generated by defining each element, the two-dimensional tire model is developed three-dimensionally in the circumferential direction of the tire, and the three-dimensional tire model 3 A two-dimensional tire model is created (not shown). At this time, a large number of three-dimensional elements are generated by element division in the circumferential direction, and each element includes nodes connected side by side in the R direction and Z direction and connected in parallel in the C direction as described above. Defined by multiple nodes.

  After the tire model is created, boundary conditions are set in step 106. The boundary conditions are necessary for analyzing the tire model, that is, for simulating the behavior of the tire, and are various conditions given to the tire model.

  In step 108, based on the numerical model set as described above, calculation such as stress calculation of the tire model by the finite element method is performed, and in step 110, the calculation result is output.

  In addition, since each element is divided by the above method and the definition of each element is regularly defined as described above, distortion / restriction in each direction of the RZC local coordinate system suitable for tire analysis is obtained. It is easy to process when analyzing stress. For example, when it is desired to analyze the strain in the Z direction, the strain in the Z direction is extracted according to the definition for each element, regardless of the orientation of each element in the overall coordinate system of the entire tire. The distortion in the Z direction can be analyzed every time.

With general FEM post-processing software, element coordinates can be displayed, so no special post-processing is required, and strain and stress can be displayed and output in a coordinate system suitable for tire analysis. It is possible to see the calculation results in terms of time and time. In particular, when using anisotropic materials (materials whose material principal axis does not match the element principal axis) as the material model in the tire, as in the past, element division and element definition However, it is almost impossible to align the material principal axis in the direction along the element principal axis by post-processing, and the above analysis is difficult. By dividing and defining elements, analysis can be done without any special post-processing. Here, the material main axis means a direction along a direction of a cord constituting a skeleton member such as a belt or a carcass or a direction of a fiber embedded in rubber and a direction orthogonal to the direction. The element principal axis refers to each axis of the RZC coordinate system.

  Specifically, if the element coordinate system is aligned with the local coordinate system suitable for tire analysis in advance as described above, even if the element principal axis and the material principal axis are different, the element principal axis is shifted from the material principal axis in post-processing. It is possible to display and output each result in the material principal axis direction by simply defining the angle. More specifically, in step 110, for example, when the material principal axis has an inclination of 10 degrees, the element principal axis (element coordinate system) is also rotated by 10 degrees, and in this state, strain and stress in each direction of the element coordinate system Just look at it.

  As in the past, in a model in which element division and element definition (the order in which the nodes of the element are connected and the connection direction when elements are defined) are randomly arranged, the material principal axis and the element principal axis are in the desired orientation. It is almost impossible to arrange them by post-processing, and enormous and complicated processing such as redefining element division once is required. By adopting the method described in this embodiment, such complicated processing is not necessary, and the time required for analysis can be greatly shortened.

In this embodiment, the local coordinate system applied to the element coordinate system is the R direction in the direction orthogonal to the tangent of the shape of the skeleton member model, the Z direction in the tangential direction, and the C direction in the direction orthogonal to the above two directions. However, the present invention is not limited to this, and the definition method of the local coordinate system itself is free, and the element definition method only needs to be regularly defined as described above.
(Example)
Next, examples will be described. For car tires with a tire size of 195 / 65R15, in the form of a carcass ply (hereinafter sometimes referred to as a ply), which is a skeletal member, between layers of reinforcing cross belts with an internal air pressure of 210 kPa and a vertical load of 4 kN The strain and stress in the RZ-C element coordinate system in the R direction perpendicular to the Z direction, the Z direction that is the tangential direction, and the C direction perpendicular to the two directions were predicted by the finite element method. The tire model is a tire model having one carcass ply and two reinforcing cross belts on the outer layer side of the carcass ply. In this example, element division and element definition were performed as described in the above embodiment (see also FIG. 2).

  Although FIG. 2 is a diagram on a two-dimensional plane, the calculation was performed with a model developed three-dimensionally according to the definition of the RZC local coordinate system. The strain / stress values can be extracted by specifying the elements existing between the reinforcing and interlinking belt layers from the calculation results of the finite element method using element numbers (numbers assigned to identify each element). A post-processing method in which only the distortion of each element was taken out was used.

  In Table 1 below, the elements between the reinforcing cross belts are designated by element numbers, and the element division and element definitions are irregularly performed for the time required to check each strain and stress in the element coordinate system. This is shown in comparison with a conventional tire model (see also FIG. 4). Here, the time required in the example is represented by an index when the time required in the conventional example is set to 100. Note that the smaller the value, the shorter the required time.

  In this embodiment, the element number is designated, and it is only necessary to take out the distortion of the element corresponding to the designated element number, and no other special post-processing is required, and the local coordinate system suitable for tire analysis is used. Since distortion can be displayed, post-processing analysis result output after analysis calculation can be obtained with less labor and time. On the other hand, in the conventional example, it is necessary to convert the strain expressed in the coordinate system of the entire tire into the strain expressed in the element coordinate system (RZC local coordinate system). As a result, the processing time increases.

  In addition, here, the comparison is performed using a model to which no pattern is applied. However, the merit of the model creation method can be similarly obtained even in a cross-sectional model with a pattern in which a circumferential groove is provided.

  Further, in the above-described conventional examples and examples, the modeling time of the anisotropic material in which the material principal axis does not coincide with the element principal axis was also compared. A tire model having the same size as the above example was used. The same model was used to compare the time required to model an anisotropic material whose angle was shifted by 30 degrees, which is the inclination of the belt from the equator direction, in the reinforcing cross belt layer. The results are shown in Table 2 below. Here, the time required in the example is represented by an index when the time required in the conventional example is set to 100. Note that the smaller the value, the shorter the required time.

  If the element coordinate system is matched with the local coordinate system suitable for tire analysis in advance as in this embodiment, even if the element principal axis and the material principal axis are different, the angle of the amount of deviation of the material principal axis from the element principal axis is Since it is possible to display and output the result simply by defining it, it is possible to model it with much less labor and time. On the other hand, in the conventional example in which the element division and the element definition are randomly arranged, it is almost impossible to align the material principal axis in a desired direction by post-processing.

  Although an example in which an analysis result is output for strain has been described here, the same applies to the case where other results such as stress are output.

Claims (1)

A method for creating a mesh model for pneumatic tire numerical analysis and an element definition method, wherein the skeleton in a region from a center portion to a bead portion in a cross section in a direction orthogonal to a tire circumferential direction of a tire model including a skeleton member model therein A direction along the shape of the member model is divided by a boundary line orthogonal to or substantially orthogonal to the tangent of the shape of the skeleton member model of the tire model, and the direction orthogonal to the shape of the skeleton member model of the region is defined as the tangent. Dividing the region into a number of elements by dividing at parallel or substantially parallel boundaries,
For each of all the divided elements, one of the direction of the tangent at the position of the element and the direction orthogonal to the tangent is a first direction, the other is a second direction, and the first direction and the second direction. The orthogonal direction is the third direction, and the coordinate system having the first direction axis, the second direction axis, and the third direction axis is an element coordinate system corresponding to the position of each of the divided elements. In each of the element coordinate systems, when defining the element by sequentially connecting a plurality of nodes among the nodes generated by the division, the first node and the second node are directed in the first direction. Defined as connected nodes, the second node and the third node are defined as nodes connected in the second direction, and the third node and the fourth node are defined in the first direction. And nodes connected in the opposite direction Performing the element definition that defines a tire model creation method comprising Te,
When creating a tire model for analyzing a tire model using an anisotropic material in which the material principal axis of the skeleton member model does not coincide with the element principal axis representing each axis of the element coordinate system, the element coordinate system Tire model creation method for defining elements .