Abstract:
An objective of the present invention is to provide a method for creating a finite element model for a filler compounded rubber that can reduce the time and effort involved in creating the model. Provided is a method of using a computer to create a finite element model for a filler compounded rubber wherein a filler is dispersed in a rubber matrix, said method comprising a first step of defining a filler model wherein filler is discretized using a finite number of elements, a second step of defining, separately from the filler model, a rubber matrix model wherein at least the space occupied by the rubber matrix is discretized using a finite number of elements, and a model embedding step of overlaying the rubber matrix model and the filler model and imparting a constraint to at least a boundary between the filler model and the rubber matrix model to define a filler compounded rubber model.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a method for creating a finite element model of a filler compounded rubber that can save the time and effort for creating thereof. 
       BACKGROUND ART 
       [0002]    In recent years, various computer simulations using a finite element method have been conducted. In these simulations, a finite element model is created by discretizing an object to be analyzed using a finite number of elements that can be handled by a computer. The finite element model is inputted a characteristic representing the stiffness and viscosity thereof. In the computer simulation using the finite element method, displacement of each node is calculated based on the predetermined deformation condition or the like. 
         [0003]    In recent years, a computer simulation using the finite element method is used in not only a mechanical structure but also in a development of a rubber material. For example, in order to streamline the development of a filler for reinforcing rubber, the following Patent Documents 1 and 2 have proposed a method for creating a finite element model of a filler compounded rubber including the filler dispersed in the matrix rubber with a computer. 
         [0004]    In Patent Document 1 and Patent Document 2, the respective portions occupied by the matrix rubber and the filler, for example, are identified based on a microscopic cross-section photograph of the filler compounded rubber. The respective portions, for example, are modeled into a matrix rubber model and a filler model using two-dimensional elements such as a triangle or quadrilateral. 
         [0000]    Patent document 1: Japanese Unexamined Patent Application Publication No. 2012-185733
 
Patent document 2: Japanese Unexamined Patent Application Publication No. 2012-198654
 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0005]    When the filler profile is complicated, in order to model accurately it, it is necessary to discretize the filler using a small sized element. Meanwhile, in order to reduce the computational cost, it is desirable to reduce the number of elements by discretizing the matrix rubber using a large sized element. Unfortunately, in the above conventional method, the nodes of each element were shared at a boundary between the matrix rubber model and the filler model. Therefore, there was a problem where the resolution of one of the models is restricted by the resolution of the other model. 
         [0006]    For example, in order to increase the calculation accuracy, when the matrix rubber model is discretized to fit the resolution of the filler, the computational cost tends to increase. On the other hand, in order to reduce the computational cost, when the filler model is discretized to fit the resolution of the matrix rubber model, the calculation accuracy tends to decrease. 
         [0007]    The present invention has been made in view of circumstances described above, and has a main object to provide a method for creating a finite element model of a filler compounded rubber that may prevent an increase in the computational cost. 
       Solution to Problem 
       [0008]    The present invention provides a method for creating a finite element model of a filler compounded rubber comprising a filler dispersed in a matrix rubber using a computer, the method comprising a first step of defining a filler model in which the filler is discretized using a finite number of elements, a second step of defining a matrix rubber model independently of the filler model, the matrix rubber model being created by discretizing a space in which at least the matrix rubber occupies using a finite number of elements, and a model-embedded step of embedding the filler-model in the matrix rubber model. The model-embedded step comprises a step of overlapping the filler-model with the matrix rubber model without considering sharing of the respective nodes of the filler model and the matrix rubber model, and a step of defining a filler compounded rubber model by providing a constraint condition to at least a boundary between the filler model and the matrix rubber model. 
         [0009]    In the method for creating a finite element model of a filler compounded rubber according to the invention, preferably, the matrix rubber model is obtained by discretizing a space that comprises a first space in which the matrix rubber occupies and a second space in which the filler occupies, and the model-embedded step comprises the step of defining the constraint condition between the filler model and the matrix rubber model to the second space. 
         [0010]    In the method for creating a finite element model of a filler compounded rubber according to the invention, preferably, the filler comprises an aggregate of a plurality of primary particles, and the first step comprises a step of defining a plurality of primary particle models each obtained by discretizing each primary particle of the filler using a finite number of elements independently of the matrix rubber model and a step of overlapping the primary particle models one another partially without considering sharing of the respective nodes of the primary particle models. 
         [0011]    In the method for creating a finite element model of a filler compounded rubber according to the invention, preferably, the filler compounded rubber model comprises a three-dimensional model, the matrix rubber model is obtained by discretizing the space using a three-dimensional element, and each primary particle model is obtained by discretizing only an outer surface of each primary particle using a two-dimensional element. 
         [0012]    In the method for creating a finite element model of a filler compounded rubber according to the invention, preferably, the filler compounded rubber model comprises a three-dimensional model, and the matrix rubber model and the primary particle models are obtained by discretizing using the elements of three-dimensional. 
         [0013]    In the method for creating a finite element model of a filler compounded rubber according to the invention, preferably, the elements of the matrix rubber model have different size to the elements of the primary particle models. 
         [0014]    In the method for creating a finite element model of a filler compounded rubber according to the invention, preferably, the method further comprises a third step of defining an interface layer model obtained by modeling at least one interface layer surrounding the filler independently of the filler model and the matrix rubber model, the third step comprises a step of discretizing the interface layer using a finite number of elements, and the model-embedded step comprises the step of overlapping the interface layer model with the matrix rubber model without considering sharing of the respective nodes of the inter face layer model and the matrix rubber model. 
         [0015]    In the method for creating a finite element model of a filler compounded rubber according to the invention, preferably, the model-embedded step comprises the step of defining a constraint condition to at least a boundary between the interface layer model and the matrix rubber model. 
         [0016]    In the method for creating a finite element model of a filler compounded rubber according to the invention, preferably, the interface layer model is obtained by discretizing the interface layer using the elements of three-dimensional. 
         [0017]    In the method for creating a finite element model of a filler compounded rubber according to the invention, preferably, matrix rubber model is obtained by discretizing a space that comprises a first space in which the matrix rubber occupies, a second space in which the filler occupies and a third space in which the interface layer occupies, and the model-embedded step comprises the step of defining a constraint condition between the interface layer model and the matrix rubber model to the third space. 
       Advantageous Effects of Invention 
       [0018]    According to the invention of claim  1 , in the first step and the second step, the respective filler model and matrix rubber model are discretized independently one another. Furthermore, the invention of claim  1  includes the model-embedded step where the matrix rubber model and the filler model are overlapped one another without considering the sharing of each node of the models, and the constraint condition is given to at least a boundary between the filler model and the matrix rubber model to define the filler compounded rubber model. 
         [0019]    Thus, according to the invention of claim  1 , it is possible to define the filler model and the matrix rubber model by discretizing the filler and the matrix rubber using an element having a size and a shape which are suitable for shapes and accuracy requirements thereof. Accordingly, it is possible to define the filler model discretized using a smaller element as well as the matrix rubber model discretized using a larger and simplized element, for example. In such an embodiment, it may be achieved reduction of calculation cost due to the matrix rubber model while maintaining calculation accuracy due to the filler model having a more detailed shape. 
         [0020]    The invention according to claim  7  includes the third step of defining the interface layer model obtained by modeling at least one interface layer surrounding the filler independently of the filler model and the matrix rubber model. The third step includes a step of discretizing the interface layer using a finite number of elements. The model-embedded step includes a step of overlapping the interface layer model in the matrix rubber model without considering shearing nodes of the respective models. 
         [0021]    According to the invention of claim  7 , it is possible to define the filler model, the matrix rubber model and the interface layer model by discretizing the filler, the matrix rubber and the interface layer respectively using an element having a size and a shape which are suitable for shapes and accuracy requirements thereof. Accordingly, it is possible to define the filler model and the interface layer model discretized using a smaller element, while discretizing the matrix rubber model using a larger and simplized element, for example. In such an embodiment, it may be achieved the suppression of calculation cost due to the matrix rubber model while maintaining calculation accuracy due to the filler model and the interface layer model having a more detailed shape. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0022]      FIG. 1  is a perspective view of a computer that executes a creation method according to the present invention. 
           [0023]      FIG. 2  is a partial enlarged cross-sectional view of a filler compounded rubber. 
           [0024]      FIG. 3  is a flowchart illustrating an embodiment of a processing procedure of a method for creating a finite element model according to the present embodiment. 
           [0025]      FIG. 4  is a plan view of a visualized filler model. 
           [0026]      FIG. 5  is a plan view of a visualized matrix rubber model. 
           [0027]      FIG. 6  is a plan view of a filler compounded rubber model of the present embodiment. 
           [0028]      FIG. 7  is an enlarged view of a portion A of  FIG. 6 . 
           [0029]      FIG. 8  is a flowchart illustrating an embodiment of a processing procedure of model-embedded step according to the present embodiment. 
           [0030]      FIG. 9  is a diagram illustrating a constraint condition of a boundary. 
           [0031]      FIG. 10A  is a partial perspective view illustrating an example of the filler compounded rubber of the present embodiment. 
           [0032]      FIG. 10B  is a cross-sectional view taken along lines A-A of  FIG. 10A . 
           [0033]      FIG. 11  is a flowchart illustrating an example of a processing procedure of the first step (step of defining a filler model). 
           [0034]      FIG. 12A  is a perspective view illustrating a visualized primary particle model, and  FIG. 12B  is an enlarged view of a portion B of  FIG. 12A . 
           [0035]      FIG. 13  is a perspective view of a visualized filler model. 
           [0036]      FIG. 14  is a cross-sectional view taken along lines C-C of  FIG. 13 . 
           [0037]      FIG. 15  is a perspective view illustrating a visualized matrix rubber model. 
           [0038]      FIG. 16  is a perspective view illustrating an example of a visualized filler compounded rubber model. 
           [0039]      FIG. 17  is a partial enlarged view of the filler compounded rubber model. 
           [0040]      FIG. 18  is a perspective view illustrating an example of the primary particle model in accordance with another embodiment of the present invention. 
           [0041]      FIG. 19  is a cross-sectional view illustrating a filler compounded rubber models defined using the primary particle model in  FIG. 18 . 
           [0042]      FIG. 20  is a partial enlarged cross-sectional view of the filler compounded rubber in accordance with another embodiment of the present invention. 
           [0043]      FIG. 21  is a flowchart illustrating a processing procedure of the creation method in accordance with another embodiment of the present invention. 
           [0044]      FIG. 22  is a plan view of a visualized interfacial layer model. 
           [0045]      FIG. 23  is a flowchart illustrating an example of a processing procedure of model-embedded step. 
           [0046]      FIG. 24  is a plan view of the filler compounded rubber model. 
           [0047]      FIG. 25  is a partial enlarged cross-sectional view of the filler compounded rubber in accordance with another embodiment of the present invention. 
           [0048]      FIG. 26  is a cross-sectional view illustrating the filler compounded rubber model. 
           [0049]      FIG. 27  is a cross-sectional view of the interface layer model. 
           [0050]      FIG. 28  is a diagram illustrating strain distribution after deformation of the filler compounded rubber model of Example 1. 
           [0051]      FIG. 29  is a diagram illustrating strain distribution after deformation of the filler compounded rubber model of Comparative Example 1. 
           [0052]      FIG. 30  is a diagram illustrating strain distribution after deformation of the filler compounded rubber model of Example 2. 
           [0053]      FIG. 31  is a diagram illustrating strain distribution after deformation of the filler compounded rubber model of Comparative Example 2. 
       
    
    
     REFERENCE SIGNS LIST 
       [0000]    
       
         
           
               2 ,  25  Filler compounded rubber 
               2 M,  25 M Filler compounded rubber model 
               3  Matrix rubber 
               3 M Matrix rubber model 
               4  Filler 
               4 M Filler model 
               28  Interface layer 
               28 M Interface layer model 
               9  Boundary 
               32  First boundary 
               33  Second boundary 
           
         
       
     
       DESCRIPTION OF EMBODIMENTS 
       [0065]    Hereinafter, an embodiment of the present invention will be explained based on the drawings. A method for creating a finite element model of a filler compounded rubber according to the present invention (hereinafter, it may be simply referred to as “creation method”.) is a method for creating a finite element model of the filler compounded rubber (hereinafter, it may be simply referred to as “filler compounded rubber model”) which includes a filler dispersed in a matrix rubber with a computer. 
         [0066]      FIG. 1  is a perspective view of a computer  1  that executes the creation method according to the present invention. The computer  1  is configured to include a main body  1   a , a keyboard  1   b , a mouse  1   c , and a display unit  1   d . The main body  1   a , for example, is provided with an arithmetic processing unit (CPU), a ROM, a working memory, a storage device such as a magnetic disk, and disk drive units  1   a   1  and  1   a   2 . In addition, the storage device is stored a software for performing the creation method of the embodiment and the like (a generic meshing software (e.g., ANSYS, Inc. “ICEM CFD”)), in advance. 
         [0067]      FIG. 2  is a partial enlarged cross-sectional view of an example of a filler compounded rubber  2  in accordance with the present embodiment. The filler compounded rubber  2  includes a matrix rubber  3  constituting the major part of the rubber and a filler  4  of a substantially circular particle disposed therein. The filler  4  is typically a carbon black, silica and other fillers may be used either alone or in combination with others. 
         [0068]    In this embodiment, the finite element model is created based on the filler compounded rubber  2 . The finite element model may also be called as a mesh model or the like. The finite element model is created using the computer  1 , and then is stored in the computer  1 . The computer  1  executes a numerical simulation using the finite element model. In the numerical simulation, various conditions are given to the finite element model, a physical quantity such as displacement or stress of the finite element model of that time is calculated by the computer  1 . 
         [0069]    In the following embodiments, although an example defined in the two-dimensional coordinate system of x-y will be explained. However, the present invention can be applied to three-dimensional model in the same manner. 
         [0070]      FIG. 3  is a flowchart illustrating an embodiment of a processing procedure of a method for creating a finite element model according to the present embodiment. This processing procedure is a procedure for creating the finite element model (filler compounded rubber model) of the filler compounded rubber  2  illustrated in  FIG. 1 . 
         [0071]    As illustrated in  FIG. 3 , in the creation method of the present embodiment, a first step S 1  is performed. In the first step S 1 , a filler model in which the filler  4  is discretized using a finite number of elements is defined. 
         [0072]    In  FIG. 4 , the filler model  4 M is visualized. The filler model  4 M is one in which a space that is approximately equal to a two-dimensional space in which the filler  4  occupies in the filler compounded rubber  2  is divided (discretized) using a plurality of elements  5 . In other words, the filler model  4 M is modeled not only the surface of the filler  4  but also the inside of the filler  4 . 
         [0073]    For the elements  5 , when the two-dimensional model of the present embodiment, for example, a quadrilateral element or a triangular element is suitably used. The filler  4  according to the present embodiment has a circular contour. The central portion of the filler model  4 M is used a simple quadrilateral elements  5   a . The peripheral portion of the filler model  4 M is used triangle elements  5   b  and quadrilateral elements  5   b . In this manner, by using elements  5  having different in size and the number of sides, the filler model  4 M having a smooth circular contour can be defined. 
         [0074]    The coordinate values of nodes and the element numbers of each element  5  of the filler model  4 M are stored in the computer  1 . In addition, a physical quantity such as elastic modulus and damping factor based on a physical quantity of the filler  4  is inputted in each element  5 . The physical quantity is available to calculate deformation of each element  5  (i.e., deformation simulation using the filler compounded rubber model  2 M). 
         [0075]    Then, in the creation method of the present embodiment, as illustrated in  FIG. 3 , a second step S 2  is performed. In the second step S 2 , a matrix rubber model  3 M is defined. Alternatively, the second step S 1  may be performed before the first step S 1 . Furthermore, the first step S 1  and second step S 2  may be performed in parallel. 
         [0076]    In  FIG. 5 , the matrix rubber model  3 M is visualized. The matrix rubber model  3 M is defined by being discretized a space in which at least the matrix rubber  3  occupies in the filler compounded rubber  2  using a finite number of elements  6 . In a preferred embodiment, in the second step, a total space of the first space T 1  in which the matrix rubber  3  occupies and a second space T 2  in which the filler  4  occupies is discretized as the matrix rubber model  3 M. That is, according to the present embodiment, the entire region of the filler compounded rubber to be analyzed is discretized by elements  6 . 
         [0077]    For the elements  6 , when the two-dimensional model of the present embodiment, for example, a quadrilateral element or a triangular element is suitably used. Since the matrix rubber model  3 M of the present embodiment has a rectangular contour shape, only a simple quadrilateral element  6   a  is used. In a preferred embodiment, as shown in  FIG. 5 , the elements  6  of the matrix rubber model  3 M are all set to the same size. In another preferred embodiment, the elements  6  of the matrix rubber model  3 M may be set larger than or the same as the size of the elements  5  of the filler model  4 M (illustrated in  FIG. 4 ). Thus, the matrix rubber model  3 M can easily be created in less number of elements than the filler model  4 M. 
         [0078]    If necessary, the matrix rubber model  3 M may be varied the length of the elements  6  in the x-direction or the y-direction. For example, when it is previously understood that a portion to be analyzed is deformed greatly in the x-direction based on the rule of thumb, the length of the element  6  in the x-direction may preferably be set smaller than the length in the y-direction. 
         [0079]    The matrix rubber model  3 M is defined independently of the filler model  4 M. Here, the expression “be defined independently” means that the respective matrix rubber model  3 M and filler model  4 M are uniquely defined without being associated with one other. For example, nodes of the matrix rubber model  3 M may be defined at any positions without sharing the nodes of the filler model  4 M. 
         [0080]    Thus, in the present embodiment, the matrix rubber  3  and the filler  4  can be discretized elements of size or shape appropriate for each. In a preferred embodiment, by discretizing the filler  4  using a smaller element  5 , it is possible to define a filler model  4 M that may reproduce outline or shape of the filler  4  accurately. Therefore it is possible to maintain the calculation accuracy. 
         [0081]    In another preferred embodiment, the matrix rubber  3  is discretized using a larger element with a simple shape. Since the matrix rubber model  3 M is defined with a small number of elements, it is possible to reduce the computational cost. Thus, it is possible to maintain the calculation accuracy while reducing the calculation cost by setting in different size the elements  6  of the matrix rubber model  3 M and the elements  5  of the filler models  4 M. 
         [0082]    The coordinate values of nodes and the element numbers of each element  6  of the matrix model  3 M are stored in the computer  1 . In addition, a physical quantity such as elastic modulus and damping factor based on a physical quantity of the matrix rubber  3  is inputted in each element  6 . The physical quantity is available to calculate deformation of each element  6  (i.e., deformation simulation using the filler compounded rubber model  2 M). 
         [0083]    Then, the creation method of the present embodiment, as shown in  FIG. 3 , the model-embedded step S 3  is performed. In the model-embedded step S 3 , the filler-model  4 M is embedded in the matrix rubber model  3 M as illustrated in  FIG. 6  and  FIG. 7  which is an enlarged view of the portion A of  FIG. 6 .  FIG. 8  is a flowchart illustrating an example of a processing procedure of the model-embedded step S 3  of the present embodiment. 
         [0084]    In model-embedded step S 3  according to the present embodiment, firstly, the matrix rubber model  3 M and the filler model  4 M are overlapped one another without considering sharing of the respective nodes of the filler model  4 M and the matrix rubber model  3 M (step S 31 ). That is, in the model-embedded step S 3 , mutual two or more models are allowed to overlap one another. The position of the filler model  4 M to the matrix rubber model  3 M is determined based on the filler compounded rubber  2  to be analyzed. 
         [0085]    In the model-embedded step S 3  according to the present embodiment, then, a constraint condition to prohibit the relative deformation is given to at least a boundary (to the boundary in this embodiment) between the filler model and the matrix rubber model (step S 32 ). With this, the filler compounded rubber model  2 M is defined in the computer  1 . 
         [0086]    The constraint condition is a condition for constraining a translational degrees of freedom between nodes of the filler model  4 M and the matrix rubber model  3 M. The constraint condition is stored in the computer  1 .  FIG. 9  is a diagram illustrating a part of the visualized filler compounded rubber model  2 M. 
         [0087]    In  FIG. 9 , one of the elements  6  is illustrated as the matrix rubber model  3 M. The element  6  includes a node i, j, k and l. In addition, in  FIG. 9 , the element  5  of filler model  4 M which is embedded (overlapped) within the matrix rubber model  3 M is illustrated. The node S of the element  5  of the filler model  4 M is located in the interior of the element  6  of the matrix rubber model  3 M. 
         [0088]    In step S 32 , first, it is determined whether the node of the elements  5  of the filler models  4 M is present within the region of the element  6  of the matrix rubber model  3 M. This determination is performed for all the elements  6  of the matrix rubber model  3 M. 
         [0089]    Then, in step S 32 , when it is determined that the node S of the elements  5  of the filler model  4 M is present in the element  6  of the matrix rubber model  3 M, the weighting factor of the node S is determined based on the geometry position of the node S to the element  6  of the matrix rubber model  3 M. The weighting factor has a relationship of inversely proportional to distances from the node of the element  5  of the filler model  4 M to each node i, j, k and  1  of the element  6  of the matrix rubber model  3 M that surrounds the node S. The closer the node S is to the node i, j, k or l, the more strongly the node S is restricted. In this example, the node S is bound strongly to the node i. Thus, the degree of freedom of the node S (translational degrees of freedom) is restrained based on the weighting factor. 
         [0090]    The weighting factor is calculated with respect to all the nodes S of the elements  5  of the filler model  4 M. Thus, relative movement between the matrix rubber model  3 M and the filler model  3 M can be restrained at the boundary  9  between the matrix rubber model  3 M and the filler model  3 M. 
         [0091]    As described above, in the creation method of the present embodiment, since the matrix rubber model  3 M and the filler model  4 M are defined independently each other, it is unnecessary to consider not only the sizes but also sharing the respective nodes of elements  5  and  6 . Therefore, time and effort of modeling is reduced. Furthermore, the creation method of the present embodiment can be reproduced the contours of the filler  4  in precisely to the simulation while preventing an increase in the number of elements. Furthermore, since the constraint condition is given to the boundary  9  between the matrix rubber model  3 M and the filler models  4 M which are defined independently, even if no node is shared, force and displacement is accurately transmitted through the boundary  9 . Thus, the creation method of the present embodiment prevents reduction of calculation precision. 
         [0092]    In step S 32  of the present embodiment, it has been explained that the constraint condition is given to only the boundary portion  9  between the matrix rubber model  3 M and the filler model  4 M. However, the present invention is not limited to such an embodiment. In step  32 , for example, the constraint condition between the filler model  4 M and the matrix rubber model  3 M may be defined in a region corresponding to the second space T 2  (shown in  FIG. 2 ) in which the filler  4  occupies. Thus, the relative movement between the filler model  4 M and the matrix rubber model  4 M can be constrained more strongly, and it may help to improve the calculation accuracy. 
         [0093]    Although the filler compounded rubber model  2 M according to the present embodiment has been exemplified to be created as a two-dimensional model, it may be created as a three-dimensional model. In this case, the matrix rubber model  3 M and the filler model  4 M, for example, are preferably discretized using a three-dimensional elements composed of a hexahedral element or a tetrahedral elements, etc. (not shown). 
         [0094]    In the creation method according to the present embodiment, it has been explained that the total space of the first space T 1  in which the matrix rubber  3  occupies and the second space T 2  in which the filler  4  occupies, as shown in  FIG. 2 , is discretized as the matrix rubber model  3 M. However, the present invention is not limited to such an embodiment. For example, a total space of the first space T 1  and a part of the second space T 2  in which the surface of the filler model overlaps with the first space may be discretized as the matrix rubber model  3 M. Such a matrix rubber model  3 M may reduce the number of elements  6  as compared to a matrix rubber model  3   m  which is formed by discretizing the total space of the first space T 1  and the second space T 2 , and therefore computational cost can be reduced. 
         [0095]    In this embodiment, although a solid filler model  4  in which the inside of the filler is also discretized using a finite number of elements  5  has been explained, it is not limited to such an embodiment. For example, a hollow filler model  4 M (not shown) in which only the surface of the filler  4  is discretized using a finite number of elements  5  may be available. Such a hollow filler model  4 M is possible to reduce the number of elements  5  as compared with the solid filler model  4 M, thereby reducing the computation time. 
         [0096]    In the creation method according to the present embodiment, it has been exemplified that the filler model  4  is defined by discretizing each filler  4  of the filler compounded rubber  2 , but it is not limited to such an embodiment.  FIG. 10A  is a partial perspective view illustrating another example of the filler compounded rubber  2  of the present embodiment, and  FIG. 10B  is a cross-sectional view taken along lines A-A of  FIG. 10A . 
         [0097]    The filler  4  according to the present embodiment includes an aggregate of a plurality of primary particles  14 . Such a filler  4  has a complicated surface shape thereof owing to the aggregate of a plurality of primary particles  14 . Therefore, it is difficult to discretized the filler  4  along the surface shape thereof. The creation method of the present embodiment, the filler model  4 M is defined based on each primary particle model  14 M in which each primary particle  14  is modeled. 
         [0098]    The processing procedure of the creation method of the present embodiment is carried out in the same procedure as the prior embodiment shown in  FIG. 3 . Furthermore, the filler compounded rubber model  2 M in this embodiment is created as a three-dimensional model.  FIG. 11  is a flowchart illustrating an example of the processing procedure of the first step S 1 ,  FIG. 12A  is a perspective view illustrating a visualized primary particle model  14 M, and  FIG. 12B  is an enlarged view of a portion B of  FIG. 12A . 
         [0099]    In the first step S 1  of the present embodiment, each primary particle model  14 M is defined by discretizing each primary particle  14  of the filler  4  shown in  FIG. 10  using a finite number of elements (step S 11 ). The primary particle model  14 M of the present embodiment is one in which only the surface  14   s  of the primary particle  14  shown in  FIG. 10  is divided (discretized) using a finite number of elements  15 . Thus, the primary particle model  14 M is defined as a hollow shape having a void  14 Mi therein. 
         [0100]    For the elements  15  in accordance with the three-dimensional model as in the present embodiment, two-dimensional elements (surface elements) are used. The two-dimensional elements  15 , for example, quadrilateral or triangular elements are suitably used. In step S 11 , the surface  14   s  of the primary particle  14  (shown in  FIG. 10 ) can be discretized using a plurality of elements  15 . Such a primary particle model  14 M, for example, may reduce the computational cost because the number of elements  15  is small as compared with a solid model in which not only the surface but also the inside of the primary particle are discretized. 
         [0101]    In step S 11  of the present embodiment, since the two-dimensional elements  15  are used, it can discretize easily the primary particles  14  along the surface  14   s  having the convex or concave portions (shown in  FIG. 2 ). Thus, it is possible to define a primary particle model  14 M that are faithfully reproduced the shape of the surface  14   s  of the respective primary particles  14 . When the unevenness of the surface  14   s  of the primary particles  14  is large, it is preferable that elements  15  are set to be small. 
         [0102]    The primary particle model  14 M is defined independently of the matrix rubber model  3 M. Thus, the nodes  17  of the primary particle model  14 M may be defined at any positions because there is no necessity to share with the nodes  12  of the matrix rubber model  3 M (shown in  FIG. 15 ). Accordingly, the primary particle model  14 M may represent accurately the surface shape of the filler  4  (shown in  FIG. 10 ). 
         [0103]    The lengths of elements  15  of the primary particle model  14 M in the x-axis direction, y-axis direction and z-axis direction can be varied as required. As a result, the elements  15  of the primary particle model  14 M can be formed in different size to the elements  6  of the matrix rubber model  3 M (shown in  FIG. 15 ). Furthermore, it is preferable that a length in each direction of the elements  15  of the primary particle model  14 M is set smaller than a length of each direction of the elements  6  of the matrix rubber model  3 M. Thus, it is possible that the primary particle model  14 M represents the shape of the surface  14   s  accurately even when the primary particle  14  has large unevenness of the surface  14   s  shown in  FIG. 10 , and therefore the calculation accuracy can be maintained. 
         [0104]    The coordinate values of nodes  17  and the element numbers of each element  15  of the respective primary particle models  14 M are stored in the computer  1 . In addition, a physical quantity such as elastic modulus and damping factor based on a physical quantity of the primary particles  14  (shown in  FIG. 10 ) is inputted in each element  15 . The physical quantity is available to a deformation simulation using the filler compounded rubber model  2 M (shown in  FIG. 16 ). 
         [0105]    As described above, since each primary particle model  14 M is defined as a hollow shape having a void therein, there is a tendency that the rigidity would be defined smaller as compared to the solid shape model. Thus, it is preferable that the physical quantity to be inputted to each element  15  is set greater than the physical quantity based on the primary particles  14  which is to be set to a solid shape model. With this, it is possible to offer the overall rigidity of each primary particle model  14 M close to the physical quantity of the primary particle  14 , thereby improving the calculation accuracy. 
         [0106]    Then, in the first step S 1  of the present embodiment, a plurality of primary particle models  14 M are partially overlapped (step S 12 ).  FIG. 13  is a perspective view of a visualized filler model  7 M.  FIG. 14  is a cross-sectional view taken along lines C-C of  FIG. 13 . In  FIG. 4 , elements  15  of the primary particle models  14 M are not illustrated. 
         [0107]    In step S 12  of the present embodiment, a plurality of primary particle models  14 M are set to overlap one another partially without considering sharing of the respective nodes  17  of the elements  15  of the primary particle models  14 M. The position of the primary particle models  14 M are set based on the filler compounded rubber  2  shown in  FIG. 10 . Thus, in step S 12 , the filler model  4 M including an aggregate of a plurality of primary particle models  14 M is set. 
         [0108]    In step S 12 , the filler model  4 M with a faithful surface shape of the filler  4  shown in  FIG. 10B  can be easily defined by only overlapping a plurality of primary particle models  14 M partially. Accordingly, step S 12  of the present embodiment can reduce the creating time of the filler compounded rubber model  2 M (shown in  FIG. 16 ). The position information of the primary particle models  14 M are stored in the computer  1 . 
         [0109]      FIG. 15  is a perspective view showing a visualized matrix rubber model. In the second step S 2  of the present embodiment, the total space of the first space T 1  in which the matrix rubber  3  occupies and the second space T 2  in which the filler  4  occupies, shown in  FIG. 10B , is discretized using three-dimensional elements  6 . As a result, the matrix rubber model  3 M is defined. For the three-dimensional elements  6 , for example, a hexahedron element or a tetrahedral element is preferably used. 
         [0110]    The matrix rubber model  3 M according to the present embodiment has a contour formed in a rectangular shape. For the elements  6 , only a simple hexahedron elements  6   b  are used. Furthermore, each element  6  is all set to the same size. In addition, it is preferable that each element  6  is equal to or greater than the elements  15  of the primary particle models  14 M. Thus, in the second step S 2 , the matrix rubber model  3 M can be created in less elements. 
         [0111]    Lengths of the elements  6  of the matrix rubber model  3 M in the x-axis direction, y-axis direction or z-axis direction can be varied as required. For example, when it is previously understood that a portion to be analyzed is deformed greatly in the x-direction based on the rule of thumb, the length of the elements  6  in the x-direction may preferably be set smaller than the length in the y-direction. In such a matrix rubber model  3 M, since the number of elements  6  in the x-axis direction is relatively increased, the deformation in the x-axis direction can be calculated accurately. 
         [0112]    The coordinate values of nodes  12  and the element numbers of each element  6  of the matrix rubber model  3 M are stored in the computer  1 . In addition, a physical quantity such as elastic modulus and damping factor based on the physical quantity of the matrix rubber  3  is inputted in each element  6 . The physical quantity is available to calculate deformation simulation using the filler compounded rubber model  2 M. 
         [0113]      FIG. 16  is a perspective view illustrating an example of a visualized filler compounded rubber model. In  FIG. 16 , some of the elements  6  of the matrix rubber model  3 M is omitted. 
         [0114]    In model-embedded step S 3  of the present embodiment, similarly to the model-embedded step S 3  of the previous embodiment shown in  FIG. 8 , the matrix rubber model  3 M and the filler model  4 M are arranged so as to overlap without considering sharing of the respective nodes of the filler model and the matrix rubber model (step S 31 ). In step S 31  according to the present embodiment, as shown in  FIG. 16 , the filler model  4 M is positioned inside the matrix rubber model  3 M without considering sharing between the nodes  12  of the elements  5  of the matrix rubber model  3 M and the nodes  17  of the elements  15  of the primary particle models  14 M. That is, in step S 31 , the mutual two or more models are allowed to overlap. The position of the filler model  4 M (primary particle models  14 M) to the matrix rubber model  3 M is determined based on the filler compounded rubber  2  to be analyzed. The number of primary particle models  14 M are identical to the number of primary particles  14  (shown in  FIG. 2 ). 
         [0115]    Then, in the model-embedded step S 3  of the present embodiment, a constraint condition is given to at least the boundary between the filler model  4 M and the matrix rubber model  3 M (step S 32 ).  FIG. 17  is a partial enlarged view of the filler compounded rubber model  2 M. The constraint condition in the present embodiment, as with the previous embodiment, is defined to the boundary  9  between each primary particle model  14 M and the matrix rubber model  3 M (shown in  FIG. 7 ). The constraint condition in the present embodiment, as with the previous embodiment, is a condition for constraining the translational degree of freedom of a node  12  of the matrix rubber element  3 M and a node  17  of the primary particle model  14 M. Such a constraint condition is calculated by the computer  1 . 
         [0116]      FIG. 17  illustrates two elements  6  and  6  as the matrix rubber model  3 M. Each element  6  includes nodes  12   a ,  12   b ,  12   c ,  12   d ,  12   e ,  12   f ,  12   g  and  12   h . Furthermore, an element  15  of the primary particle model  14 M is overlapped with one of the elements  6  of the matrix rubber model  3 M. The elements  15  include nodes  17   a ,  17   b ,  17   c  and  17   d . These nodes  17   a  to  17   d  are located inside one of the elements  6  of the matrix rubber model  3 M. 
         [0117]    In step S 32 , first, it is determines whether each node  17   a  to  17   d  of the element  15  of the primary particle model  14 M is present in the region of the element  6  of the matrix rubber model  3 M. The determination is performed for all the elements  6  of the matrix rubber model  3 M. 
         [0118]    Then, in step S 32 , when it is determined that one of the nodes  17   a  to  17   d  of the element  15  of the primary particle model  14 M is present in the elements  6  of the matrix rubber model  3 M, the weighting factors of the concerned node  17   a  to  17   d  is determined based on the geometry positions of the concerned node  17   a  to  17   d  to the element  6  of the matrix rubber model  3 M. 
         [0119]    The weighting factors, as with the previous embodiment, has a relationship of inversely proportional to distances from the concerned node  17   a  to  17   d  of the element  15  of the primary particle model  14 M to each node  12   a  to  12   d  of the element  6  of the matrix rubber model  3 M that surrounds the node thereof. The concerned node  17   a  to  17   d  of the element  15  of the primary particle model  14 M is constrained strongly closer to each node  12   a  to  12   f  of the element  6  of the matrix rubber model  3 M. For example, the node  17   b  of the element  15  of the primary particle model  14 M is most strongly constrained to the node  12   d  of the element  6  of matrix rubber model  3 M. Thus, the degree of freedom of all the nodes  17   a  to  17   d  (translational degrees of freedom) is restrained based on weighting factors. 
         [0120]    In the model-embedded step S 3 , by defining the constraint condition between the matrix rubber model  3 M and filler model  4 M, the filler compounded rubber model  2 M (shown in  FIG. 16 ) can be set. 
         [0121]    Although the nodes  12  of the elements  6  of the matrix rubber model  3 M are not shared with the nodes  17  of the elements  15  of the primary particle model  14 M in the filler compounded rubber model  2 M, force and displacement is accurately transmitted through the boundary  9  because the constraint condition is given to the boundary  9  between the matrix rubber model  3 M and the primary particle models  14 M. Accordingly, the filler compounded rubber model  2 M of the present embodiment may prevent deterioration of the calculation accuracy in a deformation simulation. The filler compounded rubber model  2 M is stored in the computer  1 . 
         [0122]    It is preferable that the weighting factor is calculated for all the nodes  17   a  to  17   d , which include nodes  17  of elements  15  located within an overlapped region  16  (shown in  FIG. 14 ) between the primary particle models  14 M and  14 M, of each element  15  of the primary particle models  14 M. Thus, since the constraint condition is given to each element  17  of the primary particle models  14 M without considering the presence of other primary particle models  14 M, relative movement between each primary particle model  14 M and the matrix rubber model  3 M tightly constrained. Accordingly, the filler compounded rubber model  2 M may maintain the surface shape of the filler model  4 M and may increase the calculation accuracy. 
         [0123]    In the creation method according to the present embodiment, it has been exemplified an aspect where the filler model  4  is previously modeled by overlapping the primary particle models  14 M partially and then is positioned inside the matrix rubber model  3 M. However, the present invention is not limited to the aspect. For example, it may be possible to be set the filler model  4 M including an aggregate of a plurality of primary particles  14 M by arranging the respective primary particle models  14 M directly within the matrix rubber model  3 M. Furthermore, in the present embodiment, it has been exemplified an aspect where one filler model  4 M is disposed in the matrix rubber model  3 M, but the present invention is not limited to such an aspect. For example, a plurality of filler models  4 M may be arranged dispersely in the interior of the matrix rubber model  3 M. 
         [0124]    It has been exemplified that the filler compounded rubber model  2 M according to the present embodiment is modeled as a three-dimensional model, but it may be created as a two-dimensional model. In this case, it is preferable that the filler model  4 M is such that only the surface  4   s  of the filler  4  is discretized using a line element (not shown) of one-dimension. Furthermore, it is preferable that the matrix rubber model  3 M is created by discretizing using a quadrilateral element or a triangular element (not shown). 
         [0125]    In the creation method of the present embodiment, it has been exemplified an aspect where each primary particle model  14 M is set by discretizing only the surface  14   s  of each primary particle  14  using two-dimensional elements  15 . However, the present invention is not limited to such an aspect.  FIG. 18  is a perspective view of a primary particle model  14 M in accordance with another embodiment of the present invention. 
         [0126]    The primary particle model  14 M, as with the matrix rubber model  3 M, may be created by discretizing a primary particle  14  using three-dimensional elements  22 . For the three-dimensional elements  22 , as with the elements  6  of the matrix rubber model  3 M, for example, a hexahedron element or a tetrahedral elements are preferably used. Thus, the primary particle model  14 M is set as a solid model which is modeled not only the surface  14   s  of the primary particle  14  but also the inside of the primary particle  14 . Such a solid primary particle model  14 M may be set a large rigidity as compared with the hollow primary particle model  14 M illustrated in  FIG. 12 . Thus, the physical quantity of the primary particle model  14 M in a solid shape may be set close to that of the primary particle  14  illustrated in  FIG. 10 , thereby improving the calculation accuracy. 
         [0127]      FIG. 19  is a cross-sectional view showing the filler compounded rubber models  2 M defined using the primary particle model  14 M in  FIG. 18 . The filler model  4 M (the primary particle model  14 M), in step S 31 , is made to arrange in the matrix rubber model  3 M without considering sharing of the nodes  12  of the elements  6  of the matrix rubber model  3 M and the node  23  of the elements  22  of the primary particle model  14 M. 
         [0128]    In step S 32 , a constraint condition between the primary particle models  14 M and the matrix rubber model  3 M is defined to a first region  26  of the matrix rubber model  3 M in which the primary particle model  14 M occupies, i.e., the second space T 2  in which the filler  4  occupies (shown in  FIG. 10B ). 
         [0129]    The constraint condition in the present embodiment, as with the constraint condition of the previous embodiment illustrated in  FIG. 17 , a weighting factor of each node  23  is determined based on the geometrical location of each node  23  of the primary particle model  14 M with respect to an element  6  of the matrix rubber model  3 M, when it has been determined that each node  23  of the primary particle model  14 M is present in the element  6  of the matrix rubber model  3 M. By using such a weighting factor, the constraint condition between the matrix rubber model  3 M and the filler model  4 M is defined to create the filler compounded rubber model  2 M. 
         [0130]    Even such a filler compounded rubber model  2 M where the nodes  12  of the matrix rubber model  3 M are not shared with the nodes  23  of the primary particle model  14 M may offer a transmission of force and displacement through the first region  26  since the constraint condition is set to the first region  26  of the first matrix rubber model  3 M in which the primary particle model  14 M occupies. Accordingly, the filler compounded rubber model  2 M of the present embodiment may maintain the calculation accuracy of the deformation simulation. 
         [0131]    Furthermore, in the filler compounded rubber model  2 M of the present embodiment, relative movement between the primary particle model  14 M and the matrix rubber model  3 M is firmly restrained as compared with the filler compounded rubber model which is defined the constraint condition only at the boundary  9  (shown in  FIG. 17 ) according to the prior embodiment, since the constraint condition is define to the first region  26  of the matrix rubber model  3 M in which the entire region of each primary particle model occupies. Therefore, the filler compounded rubber model  2 M in accordance with the present embodiment can improve the calculation accuracy. 
         [0132]    As illustrated in  FIG. 19 , it is preferable that the weighting factor is calculated for all the nodes  23  of the elements  22  of the primary particle models  14 M which include a region  27  where primary particle models  14 M are overlapped one another. Thus, the relative movement between each primary particle model  14 M and the matrix rubber model  4 M can be constrained more strongly, since the constraint condition is set to all of the elements  22  without considering the presence of other primary particle models  14 M. Accordingly, it may help to improve the calculation accuracy. 
         [0133]    It has been exemplified that the filler compounded rubber model  2 M according to the present embodiment is also created as a three-dimensional model, but it may be created as a two-dimensional model. In this case, it is preferable that the matrix rubber model  3 M and the primary particle model  14 M are created by discretizing using a quadrilateral element or a triangular element (not shown). 
         [0134]    In the creation method explained through the previous embodiments, it has been explained that the filler compounded rubber model  2 M which includes the matrix rubber model  3 M and the filler model  4 M is set based one the filler compounded rubber  2  (shown in  FIG. 2  and  FIG. 10 ) containing a matrix rubber  3  and the filler  4 , but it is not limited thereto.  FIG. 20  is a partial enlarged cross-sectional view of an example of the filler compounded rubber  25  in accordance with the present embodiment. 
         [0135]    The filler compounded rubber  25  in accordance with the present embodiment is expressed in more detailed configuration than the filler compounded rubber  2  illustrated in  FIG. 2 . The filler compounded rubber  25  is configured to include the matrix rubber  3 , the filler  4  and at least one interface layer  28  surrounding the filler  4 . In this embodiment, one interfacial layer  28  is exemplified. 
         [0136]    Through various experimental results, it has been known that a thin layers exhibiting different mechanical properties from the bulk portion of the matrix rubber  3  is formed around the filler  4 . It may also be referred to as the glass layer. The creation method according to the embodiment is suitable to create a finite element model including the interface layer  28  (the filler compounded rubber model). 
         [0137]      FIG. 21  is a flowchart illustrating a processing procedure of the creation method in accordance with the present embodiment. Through the processing procedure, the computer  1  may create the finite element model (the filler compounded rubber models) of the filler compounded rubber  25  having an interface layer  28  shown in  FIG. 20 . The filler compounded rubber model of the embodiment is exemplified as a two-dimensional model. 
         [0138]    As illustrated in  FIG. 21 , in the creation method of the embodiment, as with the creation method of the previous embodiments, includes the first step S 1  and the second step S 2 . Thus, the filler model  4 M as illustrated in  FIG. 4  and the matrix rubber model  3 M as illustrated in  FIG. 5  are defined. The processing procedure of the steps S 1  and S 2  are as described in the previous embodiments. 
         [0139]    Preferably, in the matrix rubber model  3 M according to the present embodiment, as illustrated in  FIG. 20 , the total space of the first space T 1  in which the matrix rubber  3  occupies, the second space T 2  in which the filler  4  occupies and a third space T 3  in which the interface layer  28  occupies is discretized using elements  6  as illustrated in  FIG. 5 . That is, in this embodiment, the entire region of the filler compounded rubber  25  to be analyzed is discretized using the elements  6 . 
         [0140]    Then, the creation method of the present embodiment, the third step S 30  is performed. In the third step S 30 , at least one interface layer  28  surrounding the filler  4  is discretized using a finite number of elements to define an interfacial layer model  28 M. 
         [0141]      FIG. 22  is a plan view of a visualized interfacial layer model. The interfacial layer model  28 M is a model obtained by discretizing the space which is approximately equal to a two-dimensional space in which the interface layer  28  occupies in the filler compounded rubber  25 , i.e., the third space T 3  ( FIG. 20 ) using a plurality of elements  31 . Thus, the interface layer model  28 M is created in a hollow shape having a void  28 Mi therein. The void  28 Mi has approximately equal to a volume as the second space T 2  in which the filler  4  occupies. 
         [0142]    For the elements  30 , in case of the two-dimensional model of the present embodiment, for example, a quadrilateral element or a triangular element are suitably used. The interface layer  28  of the present embodiment has an annular circular contour shape. The interface layer model  28 M includes a quadrilateral element  30   a  and a triangular element  30   b . It may be possible to define the interface layer model  28 M with a smooth circular contour by employing elements  30  having different size and the number of edges thereof. 
         [0143]    In the third step S 30 , the interface layer model  28 M is defined independently of the filler model  4 M and the matrix rubber model  3 M. Here, the expression “be defined independently” in the third step S 30  means that the interface layer model  28 M is uniquely defined without being associated with the filler model  4 M as well as the matrix rubber model  3 M. For example, nodes of the interface layer model  28 M may be defined at any positions without sharing the nodes of the filler model  4 M and the matrix rubber model  3 M, thereby improving the degree of freedom of model creation. 
         [0144]    Thus, in the creation method of the present embodiment, the filler  4 , the matrix rubber  3  and the interfacial layer  28  can be discretized using elements in size or shape appropriate for each. Preferably, the interface layer  28  may be discretized using elements smaller than that of the matrix rubber  3 . Thus, the interfacial layer model that reproduces accurately the contour or shape of the interface layer  28  may be defined, and then it would be possible to maintain the calculation accuracy. 
         [0145]    The coordinate values of nodes and the element numbers of each element  30  of the interface layer model  28 M are stored in the computer  1 . In addition, a physical quantity, which may be harder than that of the matrix rubber  3 , such as elastic modulus and damping factor based on the physical quantity of the interface layer  28  is inputted in each element  5 . The physical quantity is available to calculate deformation of each element  30  (i.e., deformation simulation using the filler compounded rubber model  2 M). 
         [0146]    In the model-embedded step S 40  to be described later, the interface layer model  28 M is disposed so as to overlap with the matrix rubber model  3 M. The respective values of the physical quantity of the interface layer model  28 M correspond to the sum of physical quantity defined in the third step S 30  and the physical quantity of the matrix rubber model  3 M. Preferably, each value of the physical quantity defined in the interface layer model  28 M is set as a value obtained by subtracting each value of the physical quantity of the matrix rubber model  3 M from each actual value of the physical quantity of the interfacial layer  28  (shown in  FIG. 20 ). Thus, it may be possible to approach the physical quantity of the interface layer models  28 M in the filler compounded rubber model  25 M to the actual interfacial layer  28 . 
         [0147]    Then, in the creation method of the present embodiment, as illustrated in  FIG. 21 , the model-embedded step S 40  is performed. In the model-embedded step S 40 , the filler model  3 M and the interface layer model  28 M are arranged so as to be embedded into the matrix rubber model  3 M.  FIG. 23  is a flowchart showing an example of a processing procedure of the model-embedded step S 40  of the present embodiment.  FIG. 24  is a plan view of the filler compounded rubber model  25 M of the present embodiment. 
         [0148]    In the model-embedded step S 40  in accordance with the present embodiment, as with the previous embodiments, the matrix rubber model  3 M and filler models  4 M are arranged so as to overlap one another without considering sharing of the respective nodes of the models one another (step S 31 ). 
         [0149]    Next, in the model-embedded step S 40 , the interface layer model  28 M is arranged so as to be embedded into the matrix rubber model  3 M without considering sharing of the respective nodes of the models one another (step S 33 ). In step S 33 , the interface layer model  28 M is arranged inside the matrix rubber model  3 M. The position of the interface layer model  28 M to the matrix rubber model  3 M is set based on the filler compounded rubber  25  to be analyzed shown in  FIG. 20 . 
         [0150]    Next, in the model-embedded step S 40 , a constraint condition is given to at least the boundary between the interface layer model  28 M and the matrix rubber model  3 M (step S 34 ). In step S 34  of the present embodiment, the constraint condition is defined to a first boundary  32  between the filler model  4 M and the interface layer model  28 M as well as a second boundary  33  between the interface layer model  28 M and the matrix rubber model  3 M. As a result, the filler compounded rubber model  25 M is defined. The method for setting the constraint condition is identical to the embodiment described above. 
         [0151]    In the creation method according to the present embodiment, it is possible to save the time and effort for sharing the respective nodes since the matrix rubber model  3 M, the filler model  4 M and the interfacial layer model  28 M are independently defined each other. The creation method of the present embodiment may reproduce accurately the contour or the like of the filler model  4 M and the interface layer model  28 M while preventing an increase in the number of elements. 
         [0152]    Furthermore, the constraint condition is defined to each boundary  32  and  33  of the matrix rubber model  3 M, the filler model  4 M and the interfacial layer model  28 M which are defined independently. In the creation method of the present embodiment, although each node of the matrix rubber model  3 M, the filler model  4 M and the interface layer model  28 M are not shared one another, force and displacement is surely transmitted through each boundary  32  and  33 , thereby maintaining the calculation accuracy. 
         [0153]    Preferably, the physical quantity defined in the interface layer model  28 M are set larger than that of the matrix rubber model  3 M and smaller than that of the filler the model  4 M. Thus, relative movement of the interface layer model  28 M to the matrix rubber model  3 M may be allowed partially even when the weighting factor of each node of the element  30  of the interfacial layer model  28 M is set same as the weighting factor of the nodes of the elements  5  of the filler model  4 M. According to such a filler compounded rubber model  25 M, it is possible to effectively reproduce the behavior of the interface layer  28 . 
         [0154]    Furthermore, the weighting factors of the elements  30  of the interface layer model  28 M may be set smaller than that of each node  23  of the element  5  of the filler model  4 M. Thus, it is possible to further permit the relative movement of the interface layer model  28 M to the matrix rubber model  3 M. When the weighting factors of each node of the interface layer model  28 M is too small, it may be difficult to constrain sufficiently between the matrix rubber model  3 M and the interface layer model  28 M. Thus, the overlapping portion between the matrix rubber model  3 M and the interface layer model  28 M may be forced out from the interface layer model  28 M, i.e., the matrix rubber model  3 M increases. 
         [0155]    It has been exemplified that the filler compounded rubber models  25 M of the present embodiment is created as a two-dimensional model, but it may be created as a three-dimensional model. In this case, the matrix rubber model  3 M, the fillers model  4 M and the interface layer model  28 M are preferably created using three-dimensional elements such as a hexahedron element or a tetrahedral element, for example. 
         [0156]      FIG. 25  is a partial enlarged cross-sectional view of the filler compounded rubber  25  in accordance with another embodiment of the present invention.  FIG. 26  is a cross-sectional view illustrating a filler compounded rubber model in accordance with another embodiment of the present invention. 
         [0157]    The filler compounded rubber  25  according to the present embodiment is configured to include the matrix rubber  3 , the filler  4  including a plurality of primary particles  14  and a single layer of the interface layer  28  surrounding around the filler  4 . In the creation method of the embodiment, the finite element model of the filler compounded rubber  25  as illustrated in  FIG. 25  (a filler compounded rubber model) is created. The filler compounded rubber model of the embodiment is created as a three-dimensional model. 
         [0158]    In this embodiment, the processing procedure of the creation method is carried out in the same steps of the prior embodiment as illustrated in  FIG. 21 . In the creation method of the embodiment, the first step S 1  is performed. The first step S 1  is carried out based on the processing procedure as illustrated in  FIG. 11  to create the filler model  4 M as illustrated in  FIG. 13 . In this embodiment, the primary particles  14  are modeled by discretizing using a plurality of three-dimensional elements  22  as illustrated in  FIG. 18 , but it is not limited thereto. For example, as illustrated in  FIG. 12 , only the surface  14   s  of the primary particles  14  may be discretized using a plurality of two-dimensional elements  15 . 
         [0159]    Furthermore, the creation method of the present embodiment, the second step S 2  is performed to create the matrix rubber model  3 M as illustrated in  FIG. 15 . The procedure of the step S 2  is the same as described in the previous embodiment. Preferably, the total space of the first space T 1  in which the matrix rubber  3  occupies, the second space T 2  in which the filler  4  occupies and the third space T 3  in which the interface layer  28  occupies is discretized using elements  6  as the matrix rubber model  3 M, as illustrated in  FIG. 25 . That is, according to the present embodiment, the entire region of the inside of the rubber to be analyzed is discretized using the elements  6 , as illustrated in  FIGS. 15 and 26 . 
         [0160]    Then, the creation method of the embodiment, the third step S 30  is performed.  FIG. 27  is a cross-sectional view of the interface layer model. In the third step S 30  of the embodiment, the space which is approximately equal to a three-dimensional space in which the interface layer  28  occupies in the filler compounded rubber  25  (the third space T 3  as illustrated in  FIG. 20 ) is discretized using a plurality of elements  30 . Thus, a hollow interface layer model  28 M having an inner void  28 Mi is set. The void  28 Mi has a volume almost equal to the second space T 2  in which the filler  4  occupies, as shown in  FIG. 25 . 
         [0161]    For the elements  30  of the interface layer model  28 M, in case of the three-dimensional model as in the present embodiment, for example, three-dimensional elements are used. For the three-dimensional elements  30 , for example, a hexahedron element or a tetrahedral element is preferably used. In this embodiment, both the hexahedral elements and tetrahedral elements are used. For this reason, the interface layer model  28 M having a smooth outline can be defined. 
         [0162]    The coordinate values of nodes  36  and the element numbers of each element  30  of the interface layer model  28 M are stored in the computer  1 . Preferably, each value of the physical quantity to be set in the interface layer model  28 M, as with the prior embodiments, is defined as a value obtained by subtracting each value of the physical quantity of the matrix rubber model  3 M from each actual value of the physical quantity of the interfacial layer  28  (illustrated in  FIG. 25 ). 
         [0163]    The interface layer model  28 M is created independently of the matrix rubber model  3 M and the primary particle model  14 M. Thus, each node  36  of the interface layer model  28 M may be defined at any arbitrary positions since each node is not necessary to be shared with any nodes  12  of the matrix rubber model  3 M as well as nodes  23  of the primary particle model  14 M. 
         [0164]    Then, in the creation method of the present embodiment, as illustrated in  FIG. 21 , the model-embedded step S 40  is performed. The model-embedded step S 40  of the embodiment is performed in the same procedure as the model-embedded step S 40  in accordance with the previous embodiment shown in  FIG. 23 . 
         [0165]    In the model-embedded step S 40  of the embodiment, as with the previous embodiments, the matrix rubber model  3 M and the filler model  4 M are placed so as to overlap one another without considering sharing of the respective nodes of the filler model and the matrix rubber model (step S 31 ). 
         [0166]    Next, in the model-embedded step S 40 , the matrix rubber model  3 M and the interface layer model  28 M are overlapped one another without considering sharing of the respective nodes of the interface layer model and the matrix rubber model (step S 33 ). In step S 33 , the interface layer model  28 M is arranged in the matrix rubber model  3 M. The position of the interface layer model  28 M to the matrix rubber model  3 M is set based on the filler compounded rubber  25  to be analyzed as illustrated in FIG.  25 . 
         [0167]    Next, in the model-embedded step S 40 , a constraint condition is given to at least the boundary between the interfacial layer model  28 M and the matrix rubber model  3 M (step S 34 ). In step S 34  of the embodiment, similarly to the prior embodiment illustrated in  FIG. 19 , the constraint conditions between the matrix rubber model  3 M and the primary particle model  14 M is defined to the first area  26  of the matrix rubber model  3 M in which the primary particle model  14 M occupies (i.e., second space T 2  in which the filler  4  occupies as shown in  FIG. 25 ). The constraint condition is defined same as described above. 
         [0168]    Then, in step S 34 , the constraint condition between the matrix rubber model  3 M and the interface layer model  28 M is defined into the second region  38  of the matrix rubber model  3 M in which the interface layer model  28 M occupies (i.e., the third space T 3  in which the interface layer  28  occupies as shown in  FIG. 25 ). 
         [0169]    Regarding constraint condition in accordance with the embodiment, as with the constraint condition of the previous embodiments, when the computer  1  is determined that each node  36  of the element  30  of the interface layer model  28 M is present in the element  6  of the matrix rubber model  3 M, the weighting factor of the concerned node  22  is determined based on the geometry position of the node  36  of the element  30  of the interface layer model  28 M to the element  6  of the matrix rubber model  3 M. By setting such a weighting factor, the constraint condition between the matrix rubber model  3 M and the interface layer model  28 M is defined, and then the filler compounded rubber model  25 M is created. 
         [0170]    Even such a filler compounded rubber model  25 M where the nodes  12  of the elements  6  of the matrix rubber model  3 M are not shared with the nodes  23  of the primary particle model  14 M may offer accuracy a transmission of force and displacement through the first region  26  since the constraint condition is set to the first region  26  of the first matrix rubber model  3 M in which the primary particle model  14 M occupies. Furthermore, the filler compounded rubber model  25 M where the nodes  12  of the elements  6  of the matrix rubber model  3 M are not shared with the node  36  of the elements  30  of the interface layer model  28 M may offer accuracy a transmission of force and displacement through the second region  38  since the constraint condition is set to the second region  38  of the first matrix rubber model  3 M in which the interface layer model  28 M occupies. Accordingly, the filler compounded rubber model  25 M in accordance with the present embodiment also maintains the calculation accuracy of the deformation simulation. 
         [0171]    Furthermore, since the matrix rubber model  3 M, the primary particle model  14 M and the interfacial layer model  28 M are independently defined one another, it can save the time and effort for sharing the respective nodes of models. In the creation method of the embodiment, it is possible to reproduce accurately the surface shape of the primary particle model  14 M and the interfacial layer model  28 M while preventing an increase in the number of elements. 
         [0172]    Preferably, each value of the physical quantity of the interfacial layer model  28 M is set larger than that of the matrix rubber model  3 M, and is set smaller than that of the primary particle model  14 M. Thus, relative movement of the interface layer model  28 M to the matrix rubber model  3 M may be allowed partially even when the weighting factor of each node  36  of the interface layer model  28 M is set same as the weighting factor of the nodes  23  of the primary particle model  14 M. According to such a filler compounded rubber model  25 M, it is possible to effectively reproduce the behavior of the interface layer  28 . 
         [0173]    Furthermore, the weighting factor of each node  36  of the interface layer model  28 M may be set smaller than that of each node  23  of the primary particle model  14 M. Thus, it is possible to further permit the relative movement of the interface layer model  28 M to the matrix rubber model  3 M. When the weighting factor of each node  36  of the interface layer model  28 M is too small, it may be difficult to constrain sufficiently between the matrix rubber model  3 M and the interface layer model  28 M. 
         [0174]    The filler compounded rubber model  25 M in accordance with the present embodiment is also exemplified as a three-dimensional structure, but it may be created as a two-dimensional model. In this case, the matrix rubber model  3 M, the primary particle model  14 M and the interface layer model  28 M are preferably discretized using a quadrilateral element or a triangular element (not shown). 
         [0175]    While particularly preferred embodiments of the present invention have been described in detail, the present invention is not limited to the embodiments as illustrated, but it may be carried out by modifying to various aspects. 
       EXAMPLE 
     Example 1 
       [0176]    According to the procedure illustrated in  FIG. 3 ,  FIG. 8  and  FIG. 11 , the filler compounded rubber model as shown in  FIG. 16  (Example 1) was defined by modeling the filler compounded rubber as shown in  FIG. 10 . The primary particle model of Example 1 was obtained by discretizing only the surface of the primary particles of the filler using two-dimensional elements. Then, using the simulation software LS-DYNA, deformation calculation with a 4% elongation in the y-axis direction of the filler compounded rubber model of Example 1 was performed. 
         [0177]    The result of strain distribution of the filler compounded rubber model of Example 1 is illustrated in  FIG. 28 . 
         [0178]    For comparison, on the basis of the conventional method, a filler model was obtained by discretizing an aggregation of primary particles as shown in  FIG. 10  along surface thereof using two-dimensional elements, and then the filler compounded rubber model that contains the filler model was defined (Comparative Example 1). Then, in the same manner as Example 1, the deformation calculation of the filler compounded rubber model of Comparative Example 1 was carried out. The result of strain distribution of the filler compounded rubber model of Comparative Example 1 is illustrated in  FIG. 29 . 
         [0179]    From the test results, it was confirmed that the time required to model the filler compounded rubber model of Example 1 was 83% of the time required to model the filler compounded rubber model of Comparative Example 1. Accordingly, the creation method of Example 1 can create a filler compounded rubber model in a short time as compared with the create method of Comparative Example 1. 
         [0180]    Furthermore, as illustrated in  FIG. 28  and  FIG. 29 , it was confirmed that the strain distribution of the filler compounded rubber model of Example 1 was substantially the same as the strain distribution of the filler compounded rubber model of Comparative Example 1. Accordingly, the filler compounded rubber model of Example can maintain the calculation accuracy. 
       Example 2 
       [0181]    According to the procedure illustrated in  FIG. 3 ,  FIG. 8  and  FIG. 11 , the filler compounded rubber model as shown in  FIG. 19  (Example 2) was defined by modeling the filler compounded rubber as shown in  FIG. 10 . The primary particle model of Example 2 was obtained by discretizing using three-dimensional elements. Then, using the simulation software described above, deformation calculation with a 50% elongation in the y-axis direction of the filler compounded rubber model of Example 2 was performed. The result of strain distribution of the filler compounded rubber model of Example 2 is illustrated in  FIG. 30 . 
         [0182]    For comparison, on the basis of the conventional method, a filler model was obtained by discretizing an aggregation of primary particles as shown in  FIG. 10  along surface thereof using three-dimensional elements, and then the filler compounded rubber model that contains the filler model was defined (Comparative Example 2). Then, in the same manner as Example 2, the deformation calculation of the filler compounded rubber model of Comparative Example 2 was carried out. The result of strain distribution of the filler compounded rubber model of Comparative Example 2 is illustrated in  FIG. 31 . 
         [0183]    From the test results, it was confirmed that the time required to model the filler compounded rubber model of Example 2 was 55% of the time required to model the filler compounded rubber model of Comparative Example 2. Accordingly, the creation method of Example 2 can create a filler compounded rubber model in a short time as compared with the create method of Comparative Example 2. 
         [0184]    Furthermore, as illustrated in  FIG. 30  and  FIG. 31 , it was confirmed that the strain distribution of the filler compounded rubber model of Example 2 was substantially the same as the strain distribution of the filler compounded rubber model of Comparative Example 2. Accordingly, the filler compounded rubber model of Example 2 can maintain the calculation accuracy.