CN114330070A - Method for rapidly generating finite element grid model of multiphase material - Google Patents
Method for rapidly generating finite element grid model of multiphase material Download PDFInfo
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Abstract
The invention discloses a method for rapidly generating a finite element grid model of a multiphase material, belonging to the technical field of computer vision, and comprising the following steps of: s1, establishing a multi-phase material CAD model, respectively exporting the models corresponding to the components, and converting the model format into an OBJ model; s2, setting a tangent plane, and acquiring a color slice sequence image of each part model; s3, fusing the color slice images of the models to obtain a color slice sequence image of the whole model; and S4, carrying out three-dimensional reconstruction on the finite element model of the acquired color slice sequence image of the integral model to acquire a high-precision finite element mesh model. The time of complex structure grid division is greatly shortened in the whole process, the quality of the model can be guaranteed, and the grid quantity of the whole structure can be reduced.
Description
Technical Field
The invention belongs to the technical field of computer vision, and particularly relates to a method for rapidly generating a finite element grid model of a multiphase material.
Background
With the development of computer technology and numerical analysis technology, the numerical analysis methods such as finite element have become one of the important means for solving the practical problems of engineering. The basic process of solving the problem by the finite element method mainly comprises the following steps: discretizing an analysis object, solving a finite element, and post-processing a calculation result. Because the quality of the grid after the structure dispersion directly affects the solving time and the correctness of the solving result, a high-precision finite element grid model needs to be established. However, for a complex three-dimensional structure, it is time-consuming and difficult to divide a hexahedral mesh model in the existing commercial software. Especially for a large project, the CAD model is very complex to build, and the division of the grid will take a lot of time for the project. The existing method capable of reducing the mesh division time only can be used for single-phase materials. How to process a CAD model containing multiphase materials and quickly generate a finite element mesh model with high precision still remains an important problem to be solved at present.
Disclosure of Invention
The invention aims to provide a method for rapidly generating a finite element mesh model of a multiphase material, which solves the problem that the conventional mesh division time method cannot act on the multiphase material.
The invention is realized by the following technical scheme:
a method for rapidly generating a multiphase material finite element mesh model, comprising the steps of:
s1, establishing a multi-phase material CAD model, respectively exporting the models corresponding to the components, and converting the model format into an OBJ model;
s2, setting a tangent plane, and acquiring a color slice sequence image of each part model;
s3, fusing the color slice images of the models to obtain a color slice sequence image of the whole model;
and S4, carrying out three-dimensional reconstruction on the finite element model of the acquired color slice sequence image of the integral model to acquire a high-precision finite element mesh model.
Further, the step S1 includes:
s1a, establishing a multi-phase material CAD model composed of a plurality of parts, and respectively exporting each part into an STL model composed of triangular patches;
s1b, redefining the coordinates and the direction of each derived STL model;
s1c, different materials and different colors of STL models assigned to different materials are respectively derived and stored as a plurality of OBJ models containing color information.
Further, the step S2 includes:
s2a, reading the first OBJ model, and setting the size, the direction and the initial position of a section;
s2b, traversing a triangular patch of the height model where the current tangent plane is located, solving an intersection point of the tangent plane and the triangular patch, and obtaining an intersection outline of the intersection plane;
s2c, traversing all three-dimensional points in the tangent plane of the current position, and judging whether the positions of the three-dimensional points are in the model or not; if the three-dimensional point is in the model, filling the interior of the image intersecting contour with the material color corresponding to the model; if the three-dimensional point is not in the model, the filling is white;
s2d, setting the elevation height of the tangent plane, acquiring the intersection plane of the tangent plane and the model layer by layer, defining the conversion relation between the size of the model and the size of the image, and deriving a color slice image until the height of the tangent plane is greater than the height of the model to obtain a color slice image of the first component;
s2e, repeating S2a-S2d, processing all component models in the whole structure model, setting the same image size and slice resolution, acquiring the minimum size of the components along the slice direction, redefining the initial positions of the slices, and acquiring color slice sequence images of all the components.
Further, in S2e, the slice resolution includes a lateral resolution and a longitudinal resolution.
Further, the step S3 includes:
s3a, acquiring the position information of each part in the whole model, and sorting out common slice images with the same height from the color slice sequence images acquired in S2;
s3b, creating a mask for the slice image of each part with the same height, and only reserving the area where the model is located in the image;
s3c, performing bitwise operation, fusing the masks of all the images to obtain a color slice image of the whole model at the current height;
and S3d, repeating the above processes to obtain a color slice sequence image of the whole model.
Further, the step S4 includes:
s4a, importing the obtained color slice sequence image of the integral model into three-dimensional reconstruction software, and calculating the slice resolution according to the resolution of the color slice sequence image and the real size of the model;
s4b, inputting slice resolution, establishing a perspective view of the model, performing threshold segmentation on the image according to different gray values of each region in a three-dimensional view of the perspective view, and establishing a corresponding mask;
and S4c, carrying out three-dimensional reconstruction of the finite element mesh model through masking, adjusting and combining pixels, creating a hexahedral eight-node voxel mesh, and generating a refined finite element mesh model.
Further, in S4a, the three-dimensional reconstruction software used is the mimics software.
Further, the color slice sequence image of the entire model is in jpg format.
Compared with the prior art, the invention has the following beneficial technical effects:
the invention discloses a method for rapidly generating a finite element grid model of a multiphase material, which can obtain a color slice image of an integral structure by independently generating a color slice image for each part and finally fusing the color slice images obtained by each part, simplifies the complex problem, avoids the condition that the grid lines of the model are disordered and cannot be calculated when various parts are assembled, and can generate a complete color slice image without carrying out a large amount of judgment to distinguish the colors of each area in the calculation process; for obtaining the integral color slice of the model, the invention does not need to do a large amount of calculation. The finite element mesh model formed by the method not only can greatly reduce the time of mesh division, but also can process a complex CAD model to form a high-precision finite element mesh model. And the method can independently control the grid quantity of each part by processing each part in batches, thereby reducing the grid quantity of the whole structure, which is very beneficial to subsequent calculation. Therefore, the benefits of this approach are enormous for a project.
Furthermore, by solving the contour of the intersection surface, the position of the three-dimensional point in the surface is judged to fill the inside of the contour, the color slice image of each part is obtained, and a large amount of judgment is not needed in the calculation process to distinguish the color of each area, so that the efficiency of obtaining the color slice is greatly improved.
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FIG. 1 is a flow chart of the present invention for generating a multiphase material refined finite element mesh model;
FIG. 2 is a flow chart of the present invention for generating color slice images;
FIG. 3 is an exemplary created multi-phase material CAD model;
FIG. 4 is an OBJ model containing color information;
FIG. 5 is a color slice image generated by each component;
FIG. 6 is a color slice image of the entire structure;
fig. 7 shows a finite element mesh model obtained by three-dimensional reconstruction.
Detailed Description
The present invention will now be described in further detail with reference to specific examples, which are intended to be illustrative, but not limiting, of the invention.
As shown in FIG. 1, the invention discloses a method for rapidly generating a finite element mesh model of a multiphase material, which comprises the following steps:
first, the component shown in fig. 3 is taken as an example, and includes four components, which are named as component a, component b, component c and component d. A multi-phase material CAD model was created using 3d max, each part was given a different material and color, each part was derived, and an OBJ model containing color information was stored as shown in fig. 4.
The export result includes 4 OBJ files and 4 mtl files (the OBJ file includes information such as a point of the model and a position of a triangular patch, and the mtl file includes color information of the model).
Secondly, setting up a tangent plane, obtaining the intersecting surface contour of the tangent plane and the model, filling the inside of the region by judging the position of the three-dimensional point, wherein the whole slice obtaining process is shown in fig. 2:
1. reading model information including vertex, texture, normal information and the like of the model, establishing a tangent plane, initializing the size, direction and initial position of the slice, adding a cyclic variable, traversing all patches at the current position, and acquiring the intersecting contour of the tangent plane and the triangular patch.
2. Further traversing three-dimensional points in the current position tangent plane, judging whether the positions of the points are in the model, and if so, filling the interior of the image intersecting contour by using the material color of the model; if the three-dimensional point is not in the model, the filling is white;
3. setting the elevation height of a section (setting the elevation height to be 0.05, namely longitudinal resolution), acquiring the intersection surface of the section and the model layer by layer, defining the conversion relation between the size of the model and the size of the image (setting the transverse resolution, setting the transverse resolution to be 0.1), deriving a color slice image (the size of the image is 500 multiplied by 500) until the elevation height of the section is larger than the height of the model, and obtaining the color slice image (totally outputting 101 pieces) of the component a;
4. all parts are then processed identically, with the same image size and slice resolution set, and color slice sequence images of all parts are derived, as shown in fig. 5 (only slice images of parts with a slice height of 4mm are shown here).
The color slice sequence images of the respective members obtained as described above are fused to obtain a color slice sequence image of the entire structural model as shown in fig. 6. The method specifically comprises the following steps:
1. acquiring the position information of each part in the whole model, and sorting out common slice images at the same height from the color slice sequence images acquired in S2;
2. creating a mask for the slice image of each part with the same height, and only reserving the area where the model is located in the image;
3. performing bitwise operation, fusing masks of all images, and acquiring a color slice image of the whole structure at the current height;
4. and repeating the processes to obtain a color slice sequence image of the whole structure model.
And fourthly, carrying out three-dimensional reconstruction on the finite element model of the acquired color slice sequence image to obtain a high-precision finite element mesh model.
1. The acquired color slice sequence images (only images in jpg format) are imported into the mimics software (medical software), and the image resolution, namely the slice resolution mentioned in process two, needs to be defined. It can also be calculated by itself here.
Image resolution, including lateral resolution (the ratio of the true size of the model to the image size) and longitudinal resolution (the ratio of the size of the model in the thickness direction to the number of spaces between the images). Such as: the outer circle of the model had a diameter of 50cm and a thickness of 5cm, and the slice images obtained by the slicing software were 101 (total 100 image intervals) and had an image size of 500 × 500. The transverse resolution is 50/500-0.1, and the longitudinal resolution is 5/100-0.05.
2. Inputting the resolution of a slice, creating a perspective view of a model, performing threshold segmentation on an image according to different gray values of each region in the perspective view, and establishing a corresponding mask;
3. three-dimensional reconstruction of a finite element mesh model is carried out through a mask, a hexahedral voxel mesh with eight nodes is created, smooth options are selected, xy-direction combined pixel values are set to be 3 in voxel grouping, calculation is carried out, a corresponding finite element mesh model (the mesh quantity is about 20 ten thousand) shown in the figure 7 can be obtained, format files such as inp, bmp and the like can be output by the model, and analysis and calculation can be carried out in corresponding finite element software.
Claims (8)
1. A method for rapidly generating a finite element mesh model of a multiphase material is characterized by comprising the following steps:
s1, establishing a multi-phase material CAD model, respectively exporting the models corresponding to the components, and converting the model format into an OBJ model;
s2, setting a tangent plane, and acquiring a color slice sequence image of each part model;
s3, fusing the color slice images of the models to obtain a color slice sequence image of the whole model;
and S4, carrying out three-dimensional reconstruction on the finite element model of the acquired color slice sequence image of the integral model to acquire a high-precision finite element mesh model.
2. The method for rapidly generating a finite element mesh model of a multiphase material as claimed in claim 1, wherein the step S1 comprises:
s1a, establishing a multi-phase material CAD model composed of a plurality of parts, and respectively exporting each part into an STL model composed of triangular patches;
s1b, redefining the coordinates and the direction of each derived STL model;
s1c, different materials and different colors of STL models assigned to different materials are respectively derived and stored as a plurality of OBJ models containing color information.
3. The method for rapidly generating a finite element mesh model of multiphase material as claimed in claim 2, wherein the step S2 comprises:
s2a, reading the first OBJ model, and setting the size, the direction and the initial position of a section;
s2b, traversing a triangular patch of the height model where the current tangent plane is located, solving an intersection point of the tangent plane and the triangular patch, and obtaining an intersection outline of the intersection plane;
s2c, traversing all three-dimensional points in the tangent plane of the current position, and judging whether the positions of the three-dimensional points are in the model or not; if the three-dimensional point is in the model, filling the interior of the image intersecting contour with the material color corresponding to the model; if the three-dimensional point is not in the model, the filling is white;
s2d, setting the elevation height of the tangent plane, acquiring the intersection plane of the tangent plane and the model layer by layer, defining the conversion relation between the size of the model and the size of the image, and deriving a color slice image until the height of the tangent plane is greater than the height of the model to obtain a color slice image of the first component;
s2e, repeating S2a-S2d, processing all component models in the whole structure model, setting the same image size and slice resolution, acquiring the minimum size of the components along the slice direction, redefining the initial positions of the slices, and acquiring color slice sequence images of all the components.
4. The method for rapidly generating a multiphase material finite element mesh model as claimed in claim 3, wherein in S2e, the slice resolution comprises a transverse resolution and a longitudinal resolution.
5. The method for rapidly generating a finite element mesh model of a multiphase material as claimed in claim 1, wherein the step S3 comprises:
s3a, acquiring the position information of each part in the whole model, and sorting out common slice images with the same height from the color slice sequence images acquired in S2;
s3b, creating a mask for the slice image of each part with the same height, and only reserving the area where the model is located in the image;
s3c, performing bitwise operation, fusing the masks of all the images to obtain a color slice image of the whole model at the current height;
and S3d, repeating the above processes to obtain a color slice sequence image of the whole model.
6. The method for rapidly generating a finite element mesh model of a multiphase material as claimed in claim 1, wherein the step S4 comprises:
s4a, importing the obtained color slice sequence image of the integral model into three-dimensional reconstruction software, and calculating the slice resolution according to the resolution of the color slice sequence image and the real size of the model;
s4b, inputting slice resolution, establishing a perspective view of the model, performing threshold segmentation on the image according to different gray values of each region in a three-dimensional view of the perspective view, and establishing a corresponding mask;
and S4c, carrying out three-dimensional reconstruction of the finite element mesh model through masking, adjusting and combining pixels, creating a hexahedral eight-node voxel mesh, and generating a refined finite element mesh model.
7. The method for rapidly generating the finite element mesh model of the multiphase material as defined in claim 6, wherein the three-dimensional reconstruction software adopted in S4a is a mix software.
8. The method of claim 5, wherein the color slice sequence images of the entire model are in jpg format.
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| CN113536617A (en) * | 2021-03-31 | 2021-10-22 | 长安大学 | Rapid generation method of fine finite element model with complex structure |
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| CN102236737A (en) * | 2011-07-14 | 2011-11-09 | 西安交通大学 | Method for reconstructing micro structure finite element of multiphase material based on sequence image |
| US20170148182A1 (en) * | 2015-11-20 | 2017-05-25 | Roland Dg Corporation | Cross-section data generating device and cross-section data generating method |
| CN113536617A (en) * | 2021-03-31 | 2021-10-22 | 长安大学 | Rapid generation method of fine finite element model with complex structure |
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