JP2017156271A - Structure analyzing device, structure analyzing method, and three-dimensional fiber material manufacturing method - Google Patents

Abstract

A structural analysis apparatus for analyzing the structure of a fiber-reinforced composite material from a three-dimensional image of the fiber-reinforced composite material without using binarization processing. A structural analysis device calculates an eigenvector in a minimum direction of gradation value change at each lattice point of coordinates in a three-dimensional image in which a three-dimensional woven fiber material is photographed, and aligns each lattice point. Lattice point orientation calculator 151 and the orientation of the points in the image are calculated based on the orientations of the lattice points around the points, and the orientation is similarly applied to the new points moved in the calculated orientation direction. A boundary curve calculation unit 152 that calculates a boundary curve that is a drawing direction of the fiber bundle by repeating the calculation. [Selection] Figure 2

Description

  The present invention relates to a structure analysis apparatus, a structure analysis method, and a three-dimensional woven fiber material manufacturing method, and is suitable for application to, for example, inspection of a fiber reinforced composite material.

  In recent years, fiber reinforced composite materials have begun to be used in various fields. A fiber reinforced composite material is a composite material manufactured by combining fibers and a support material, and has superior material characteristics such as light weight and high strength compared to a single material, so it is a component for aircraft, automobiles, etc. Has attracted attention as. Examples of the fiber reinforced composite material include CMC (Ceramic Matrix Composites) and FRP (Fiber Reinforced Plastics), which are appropriately used depending on the environment and purpose of use.

  In such a fiber reinforced composite material, the orientation of the fiber bundle greatly affects the strength. Therefore, the fiber bundle of the part made of the completed fiber reinforced composite material meanders at a place that should be a straight line, deviates from the reference axis that should be originally placed, or is broken in the middle. When doing so, the strength of the fiber-reinforced composite material decreases. Therefore, it is necessary to inspect the orientation of fiber bundles of parts made of finished fiber reinforced composite materials. For example, analysis of internal structure using 3D volume data (CT images) of parts taken by CT (Computed Tomography) scan Is considered to do.

  Patent Document 1 discloses a second step of binarizing an input three-dimensional image to obtain a binary image, and an orientation detection filter having a parameter for giving anisotropy to the shape of a detection section. A third step for estimating the orientation of each foreground pixel in the value image, a fourth step for extracting a center pixel indicating the center of the fiber bundle from the foreground pixel group whose orientation has been estimated, and the extracted center pixel group The fifth step of connecting the central pixels indicating the same fiber bundle with the central pixels indicating the same or similar orientation as the same fiber bundle, and meandering of the central pixel group indicating the connected same fiber bundle And a sixth step of calculating the quantity.

Japanese Patent Laying-Open No. 2015-068752

  However, detailed imaging by CT scan takes time, and in particular, it is not realistic to capture a detailed CT image with a small voxel size for a large part. Also, in the analysis of CT images, binarization processing is often performed, but CT images often contain noise, and when binarization processing is performed, the boundary between the object and the background There are also places where judgment is not appropriate. In particular, low resolution images with a large voxel size have many intermediate tones, and binarization may cause loss of important geometric information that characterizes the fabric structure, making it difficult to recognize fiber bundle orientation. is there.

  The present invention has been made in consideration of the above points, and a structure analysis apparatus and structure capable of analyzing the structure of a fiber-reinforced composite material from a three-dimensional image of the fiber-reinforced composite material without using a binarization process It is intended to provide an analysis method.

  In order to solve such a problem, the structural analysis device of the present disclosure calculates an eigenvector in the minimum direction of change in gradation value at each lattice point of coordinates in a three-dimensional image in which a three-dimensional woven fiber material is photographed, A lattice point orientation calculation unit for making the orientation of each lattice point, and the orientation of the points in the image are calculated based on the orientation of the lattice points around the point, and the orientation direction calculated And a boundary curve calculation unit that calculates a boundary curve that is a drawing direction of the fiber bundle by repeatedly calculating the orientation in the same manner for the new point that has moved to the position.

  Further, the apparatus operating method of the present disclosure is such that, at each grid point of coordinates in a three-dimensional image in which a three-dimensional woven fiber material is photographed, the eigenvector in the minimum direction of gradation value change is set as the orientation of each grid point. Calculating the orientation of the points in the image based on the orientation of the grid points around the point, and similarly for the new point moved in the direction of the calculated orientation This is a structural analysis method for calculating a boundary curve that is a drawing direction of a fiber bundle by repeating calculation of.

  In addition, the three-dimensional woven fiber material manufacturing method of the present disclosure includes a three-dimensional woven fiber material, wherein the three-dimensional woven fiber material is formed, and the formed three-dimensional woven fiber material is inspected using the above-described structural analysis method. It is a manufacturing method.

  According to the present disclosure, the structure of a fiber reinforced composite material can be analyzed from a three-dimensional image of the fiber reinforced composite material without using a binarization process.

It is a figure which shows the hardware constitutions of the structural analysis apparatus which concerns on this embodiment. It is a figure shown about the functional block of the analysis process part of a structural analysis apparatus. It is a flowchart of the structure analysis process which concerns on this Embodiment. It is a figure which shows in simulation about the three-dimensional woven fiber material used as the object of structural analysis in this embodiment. It is a figure which represents typically about the orientation of the lattice point calculated from a gradient vector. It is a flowchart shown about lattice point orientation calculation processing. It is the schematic for demonstrating calculation of a boundary curve. It is CT image which shows the cross section of the three-dimensional woven fiber raw material of a SiC fiber. 9 is an image obtained by superimposing the boundary curve searched by applying the boundary curve calculation process on the CT image of FIG. 8 on the CT image of FIG. It is an image in which different gradation values are assigned for each direction component with respect to the orientation obtained by the boundary curve calculation process. It is an enlarged view of the part enclosed by the square of FIG. FIG. 4 is a diagram showing vector fields u and v and isosurfaces being scalar fields s and t in two dimensions. It is a flowchart of a fiber bundle surface calculation process. It is a figure of an example which represented the isosurface of s, t, and f obtained by the fiber bundle surface calculation process with the three-dimensional image.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the following description, similar elements are denoted by the same reference numerals, and redundant description is omitted.

(1) Configuration of Structural Analysis Device According to this Embodiment FIG. 1 is a diagram illustrating a hardware configuration of a structural analysis device 100 according to this embodiment. As shown in this figure, the structural analysis apparatus 100 includes a CPU (Central Processing Unit) 101, a volatile storage unit 102 such as a RAM (Random Access Memory), a nonvolatile storage unit 103 such as a hard disk and a flash memory, and a network 201. A network connection unit 104 for connecting to an external device, an external device connection unit 105 such as a USB (Universal Serial Bus) connector for connecting an external memory 202, an input device 106 such as a keyboard and a mouse, and a liquid crystal display screen The display device 107 may be configured. Here, the CPU 101, the volatile storage unit 102, and the nonvolatile storage unit 103 constitute an analysis processing unit 150 that is operated by software. The structural analysis apparatus 100 may be configured by a computer system in which computer apparatuses having a hardware configuration as shown in FIG. 1 are connected to a network.

  FIG. 2 is a diagram illustrating the configuration of the analysis processing unit 150 of the structural analysis apparatus 100. As shown in this figure, the analysis processing unit 150 calculates the eigenvector in the minimum direction of the gradation value change at each lattice point of the coordinates in the image where the cross section of the three-dimensional woven fiber material is photographed. Similarly, the lattice point orientation calculation unit 151 to be oriented and the orientation of an arbitrary point in the image are calculated based on the orientation of the surrounding lattice points, and similarly for the new point moved in the direction of the calculated orientation A boundary curve calculation unit 152 that calculates a boundary curve that is an extending direction of the fiber bundle by repeatedly calculating the orientation, and a fiber bundle surface calculation unit 153 that calculates a surface of a layer formed by the family of fiber bundles from the boundary curve. And have.

(2) Structural Analysis Processing FIG. 3 is a flowchart of the structural analysis processing S100 according to the present embodiment. As shown in this flowchart, first, in the structural analysis process S100, in step S110, a three-dimensional image captured by an external CT scanning device or the like is input via the network 201, the external memory 202, or the like. Next, a grid point orientation calculation process S120 by the grid point orientation calculation unit 151 and a boundary curve calculation process S130 by the boundary curve calculation unit 152 are performed using the results of the grid point orientation calculation process. Thereafter, a fiber bundle surface calculation process S140 is performed by the fiber bundle surface calculation unit 153, and the structure analysis process S100 is terminated. Here, the fiber bundle surface calculation process S140 may not be performed. Details of each process will be described below. In the following description, it is assumed that the three-dimensional image is a CT image photographed by a CT scanning device, and the gradation value is referred to as a CT value, but even when a three-dimensional image that is not a CT image is used. A gradation value can be applied as the CT value.

  FIG. 4 is a diagram schematically illustrating a three-dimensional woven fiber material that is a target of structural analysis in the present embodiment. As shown in FIG. 4, the three-dimensional woven fiber material is formed by stacking thin plates of plain woven fibers composed of X yarns 11 and Y yarns 12 and binding a plurality of thin plates with Z yarns 13.

ここで、距離ｒは、δをＣＴ画像のボクセルサイズとし、αを定数とすると、α×δで表される。αは１．５〜３に設定されることが望ましい。ｗ_jは、格子点ｑ_jにおける重みであり、以下の式（２）で定義することとしてもよい。

ここで、ｄ_jは、ｐ_iからｑ_jまでの距離である。勾配ベクトルｇ_jはＣＴ値の変化を示し、最小固有値の固有ベクトルｅ_1iはＣＴ値の最小変化方向を意味する。したがって、分散共分散行列Ｍの最小固有値の固有ベクトルｅ_1iをｐ_iにおける配向とする（Ｓ１２３）。ここで、距離ｒは、繊維束と繊維束との間の距離以下とすることができる。またその中でも最も大きい値とすることが好ましく、繊維束と繊維束との間の距離としてもよい。また格子点の配向の算出では、ハリス（Harris）のコーナー検出法を用いることとしてもよい。 (3) Lattice point orientation calculation processing In the lattice point orientation calculation processing S120 by the lattice point orientation calculation unit 151, in the CT image, it is assumed that the minimum direction of change in CT value is the orientation, and the orientation is calculated using the gradient vector. To do. Figure 5 is a grating in the CT image in which the yarn 31 and 32 is a fiber bundle is reflected, and the gradient vector g _i of the lattice point q _j in the lattice point p _i within the distance r, which is calculated from the gradient vector g _i It is a figure typically expressed about the orientation (eigenvector e _1i ) of the point p _i . FIG. 6 is a flowchart illustrating the lattice point orientation calculation processing S120. The lattice point orientation calculation process S120 will be described with reference to FIGS. The grid point orientation calculation unit 151 first calculates the gradient vector g _i at all grid points in the CT image (S121). Next, for each point p _i whose orientation is to be detected, the variance-covariance matrix M shown in Expression (1) is calculated for the lattice point q _i within the predetermined distance r (S122).

Here, the distance r is expressed as α × δ, where δ is the voxel size of the CT image and α is a constant. α is preferably set to 1.5 to 3. w _j is a weight at the lattice point q _j and may be defined by the following equation (2).

Here, d _j is the distance from p _i to q _j. The gradient vector g _j indicates a change in CT value, and the eigenvector e _{1i of the} minimum eigenvalue means the minimum change direction of the CT value. Therefore, the eigenvector e _1i of the minimum eigenvalue of the variance-covariance matrix M is set as the orientation at p _i (S123). Here, the distance r can be less than or equal to the distance between the fiber bundles. Moreover, it is preferable to set it as the largest value among these, and it is good also as the distance between a fiber bundle and a fiber bundle. In calculating the orientation of the lattice points, a Harris corner detection method may be used.

(4) Boundary Curve Calculation Processing Next, the boundary curve calculation processing S130 performed by the boundary curve calculation unit 152 will be described. FIG. 7 is a schematic diagram for explaining calculation of the boundary curve. In the boundary curve calculation processing S130, firstly, the orientation e _j of the point a _j, calculated by trilinear interpolation of surrounding grid points p _i of eigenvectors {e _1i}. Next, a point b separated from the point a _j by a distance ε in the e _j direction is calculated. Further, the same processing is repeated with the point b as a _{j + 1} , and the process advances by a minute distance according to the orientation. At this time, if the point b satisfies any of the following conditions, the process may be terminated.
Condition 1: The curvature of the boundary curve is not less than a predetermined value.
Condition 2: The eigenvector e _2j of the second eigenvalue at the point b is significantly different from the eigenvector of the second eigenvalue at the point a _j .

The reason why the conditions 1 and 2 are provided is to avoid the influence of noise in the CT image. In particular, the CT value of the air portion at the intersection of the X yarn and the Y yarn becomes higher than expected and becomes unclear. This is because the direction of the gradient does not behave as expected, and when the traveling direction is determined only by e _1i , there is a possibility of tracing on the fiber bundles extending in different directions. In order to avoid such an erroneous search, the next point b is added to the next curve only when there is no significant change in the bending direction. Specifically, the predetermined value of the curvature for condition 1 can be determined based on the assumed curvature and the maximum curvature and its allowable intersection, and for condition 2, the second eigenvector of point a and the second of b Can be determined based on the amount of change in curvature and its allowable intersection.

  FIG. 8 is a CT image showing a cross section of a three-dimensional woven fiber material of SiC fibers. The overlapping portion of the X yarn and the Y yarn has a pillar structure, and an array of 2 × 2 pillars is called a unit cell, and is handled as the minimum structural unit of the three-dimensional woven fiber material. In FIG. 8, the unit cell is observed as a white square. FIG. 9 is an image in which the boundary curve searched by applying the boundary curve calculation process S130 to the CT image of FIG. 8 is superimposed on the CT image of FIG. As shown in this figure, it is confirmed that the boundary between the X yarn and the Y yarn is accurately searched.

10, to the three-dimensional woven fiber material of the cross-section shown CT image of the SiC fibers, perform grid point orientation calculation process S120 and the boundary curve calculation process S130, for each point _{a i e 1i = (e x} , e It is an image in which different gradation values are assigned to _y , _ez ). FIG. 11 is an enlarged view of a portion surrounded by a square in FIG. As shown in these figures, it can be confirmed that the boundary of each yarn is shown. In _{practice, e 1i = (e x,} e y, e z) with respect to by color display by assigning a color (R (red), G (green), B (blue)), each yarn The extending direction can be displayed more clearly.

(5) Fiber Bundle Surface Calculation Processing Uniform and accurate arrangement of unit cells is an important factor in parts molded from three-dimensional woven fiber materials such as CMC. In the fiber bundle surface calculation process S140 of the present embodiment, for the purpose of evaluating the cross shape of the X yarn and Y yarn of each layer, the boundary of the layer is represented as a surface. These planes approximating the yarn family are represented as isosurfaces of a scalar function whose gradient direction coincides with the yarn direction of this family. The scalar fields s, t and f can be considered as X, Y and Z yarns, respectively. These scalar fields can be obtained by solving three independent Poisson equations for the scalar function. FIG. 12 is a diagram showing this concept in two dimensions. Arrows indicate vectors belonging to vector fields u and v corresponding to the X and Y yarns, respectively. The isosurfaces that become the scalar fields s and t are indicated by solid lines. By obtaining the isosurface, the unit cell 50 that is a set of squares appears surrounded by the isosurface.

  FIG. 13 shows a flowchart of the fiber bundle surface calculation process S140. For simplicity, u, v, and w are approximated to the directions of the X, Y, and Z yarns, respectively. The input of this algorithm is a set of a curve resulting from the boundary curve calculation process and two vectors. Two vector sets are provided as u and v target directions.

  As shown in this flowchart, first, the boundary curve is divided into short segments (S141). Next, the direction of the segment is compared with the target direction to determine whether the segment belongs to u or v (S142). For example, the segment orientation is determined so as to coincide with the orientation of the target direction of the vector field specified in step S142, or to be the direction with the highest degree of coincidence among some candidates (S143). In addition, a lattice structure that covers an object in the CT image is generated, and three vectors u, v, and w are assigned to each lattice point (S144). In this assignment, a normalized vector that is an average of a plurality of normalized vectors obtained by normalizing a plurality of segments obtained in step S143 may be assigned. Further, this average may be applied to a segment closer to the grid point than a predetermined distance. If there is no segment that is sufficiently close to the grid point, it may be expanded to another grid point to obtain a vector of the grid point under consideration. The vector field w is defined by the outer product u × v. Finally, the three Poisson equations ∇s = u, ∇t = v and ∇f = w are solved independently (S145) to obtain three scalar fields s, t and f, and so on. The value plane is output (S146).

  FIG. 14 is a diagram showing an example in which the isosurfaces of s, t, and f obtained by the fiber bundle surface calculation process S140 are represented by a three-dimensional image. As shown in this figure, the shape and arrangement of the unit cell can be confirmed.

  In addition, the inspection of the three-dimensional woven fiber material using at least one of the orientation of the lattice points, the boundary curve and the surface of the fiber bundle described above, for example, if it is determined that the strength or the like is insufficient, In other cases, product inspection such as processing as a non-defective product may be performed. The inspection process can be one of the manufacturing processes of the three-dimensional woven fiber material.

(6) Effects of the present embodiment The structural analysis apparatus 100 according to the present embodiment has a minimum direction of change in gradation value at each grid point of coordinates in a three-dimensional image obtained by photographing a three-dimensional woven fiber material. Lattice point orientation calculation unit 151 that calculates eigenvectors and sets the orientation of each lattice point, and calculates the orientation of points in the image based on the orientation of lattice points around the point, and moves in the direction of the computed orientation Since the boundary curve calculation unit 152 that calculates the boundary curve that is the stretching direction of the fiber bundle by repeatedly calculating the orientation in the same manner for the new point is provided, without using a binarization process The structure of the fiber reinforced composite material can be analyzed from the three-dimensional image of the fiber reinforced composite material.

  The present disclosure can be applied to inspection of fiber reinforced composite materials.

100 Structural analysis apparatus 101 CPU
102 volatile storage unit 103 nonvolatile storage unit 104 network connection unit 105 external device connection unit 106 input device 107 display device 150 analysis processing unit 151 lattice point orientation calculation unit 152 boundary curve calculation unit 153 fiber bundle surface calculation unit 201 network 202 external memory

Claims (11)

At each lattice point of coordinates in the three-dimensional image in which the three-dimensional woven fiber material is photographed, a lattice point orientation calculation unit that calculates an eigenvector in the minimum direction of gradation value change and sets the orientation of each lattice point; ,
The orientation of the points in the image is calculated based on the orientation of the grid points around the points, and the orientation is similarly applied to the new points that have moved in the calculated orientation direction. A structure analysis apparatus comprising: a boundary curve calculation unit that repeatedly calculates and calculates a boundary curve that is a drawing direction of the fiber bundle. In the structural analysis apparatus of Claim 1,
The grid the grid point orientation calculation unit, the gradient vector g _j calculated at each lattice point q _j, When the weight w _j in the respective lattice points q _j, at a distance in the r from the lattice point p _i Equation (1) of the following covariance matrix M for point q _j :

, And the eigenvector e _{1i of the} minimum eigenvalue is set as the orientation at p _i . The structural analysis apparatus according to claim 2,
The distance r is represented by α × δ where δ is the length of one side of the pixel of the image, and α is 1.5 to 3. In the structural analysis apparatus according to claim 2 or 3,
The weight w _j is expressed by the following equation (2), where d _j is the distance from the lattice point p _i to the lattice point q _j.

A structural analysis device represented by In the structural analysis apparatus according to claim 2 or 3,
The structure r is a structure analysis device in which the distance r is equal to or less than the distance between the fiber bundles. In the structural analysis apparatus according to any one of claims 1 to 5,
A structure analysis apparatus that performs calculation based on the orientation of the lattice points around the point by triple linear interpolation. In the structural analysis device according to any one of claims 1 to 6,
The repetition is
Condition 1: the curvature of the boundary curve formed by adding the new point is greater than or equal to a predetermined value, and Condition 2: the second eigenvalue vector of the new point and the second of the previous point Is significantly different from the eigenvalue vector of
A structural analysis device that terminates the process if any of the above is satisfied. In the structural analysis apparatus according to any one of claims 1 to 7,
A structural analysis device further comprising a fiber bundle surface calculation unit that calculates a surface of a layer formed by the family of fiber bundles from the boundary curve. The structural analysis apparatus according to claim 8,
The fiber bundle surface calculation unit assigns vectors u, v, and w corresponding to the X, Y, and Z yarns to the lattice points based on the boundary curve, and Poisson's formula ∇s = u, ∇t = V and ∇f = w are independently solved, and the obtained isosurfaces of s, t, and f are output. At each lattice point of coordinates in the three-dimensional image where the three-dimensional woven fiber material is photographed, the eigenvector of the minimum direction of change in gradation value is set as the orientation of each lattice point,
The orientation of the points in the image is calculated based on the orientation of the grid points around the points, and the orientation is similarly applied to the new points that have moved in the calculated orientation direction. A structural analysis method for calculating a boundary curve that is a drawing direction of a fiber bundle by repeating the calculation. Molding three-dimensional woven fiber material,
A method for producing a three-dimensional woven fiber material, wherein the molded three-dimensional woven fiber material is inspected using the structural analysis method according to claim 10.

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