A three-dimensional discrete element modeling method for carbon fiber toughened ceramic matrix materials

Abstract

The present application belongs to the technical field of discrete element modeling and numerical simulation, and provides a three-dimensional discrete element modeling method for carbon fiber toughened ceramic matrix material, which comprises the following steps: (1) selecting a required modeling area in a carbon fiber toughened ceramic matrix sample cross-section electron microscope photo; (2) pre-processing the selected area photo; (3) performing circle detection on the selected area photo; (4) converting pixel coordinates into length coordinates; (5) determining carbon fiber model axis coordinates and establishing a carbon fiber discrete element model; (6) filling ceramic matrix particles; (7) giving carbon fiber and ceramic matrix model parameters; and (8) generating a carbon fiber toughened ceramic matrix model. The present application uses the carbon fiber toughened ceramic matrix sample cross-section photo under an electron microscope, reads the coordinates of the sample for modeling, and carries out subsequent discrete element numerical simulation of the carbon fiber toughened ceramic sample processing process, so that the material damage degree under different processing conditions can be predicted and the processing strategy can be optimized.

Description

Technical Field

[0001] This invention belongs to the field of discrete element modeling and numerical simulation technology, specifically relating to a three-dimensional discrete element modeling method for carbon fiber toughened ceramic matrix materials. Background Technology

[0002] Fiber-reinforced silicon carbide composites possess a range of advantages, including high strength, high modulus, high temperature resistance, oxidation resistance, corrosion resistance, radiation resistance, and creep resistance. As high-temperature resistant structures, they have broad application prospects in aerospace, nuclear energy, and other fields. Furthermore, the composition of fiber-reinforced silicon carbide composites is tunable, making them highly designable and high-performance high-temperature resistant microwave absorbing materials. Therefore, fiber-reinforced silicon carbide composites have become one of the hot research topics both domestically and internationally in recent years.

[0003] Near-net-shape forming techniques are commonly used to fabricate ceramic matrix composites (CMCs), but secondary processing is still required to meet the dimensional accuracy and geometric tolerances of the final assembly. Due to the anisotropy, high hardness, and brittleness of CMCs, the material removal mechanism during processing differs from that of homogeneous materials, and the influence of surface integrity and fatigue performance also differs between the two. Many scholars both domestically and internationally have conducted extensive research on the processing mechanism, damage detection and characterization, surface integrity, and processing technology of CMCs. They have also incorporated special energy field processing technologies, introducing non-traditional processing techniques such as ultrasonic vibration, lasers, water jets, and electrical discharge machining to improve processing efficiency and quality. However, problems such as severe tool wear, low surface quality and processing efficiency, and difficulty in controlling processing damage still exist.

[0004] By using discrete element method (DEM) modeling software to reconstruct the internal structure of raw materials, various cracks generated during processing can be simulated, and the mechanical properties of the materials can be analyzed. Simulation experiments can significantly improve material utilization and reduce costs. Furthermore, simulations can simulate various types of damage that occur during processing, which is crucial for ensuring that the processed material meets application requirements. Through simulation, the degree of damage under different processing conditions can be predicted, processing strategies can be optimized, damage can be reduced, and material utilization can be improved. Summary of the Invention

[0005] Purpose of the invention: This invention provides a three-dimensional discrete element modeling method for carbon fiber toughened ceramic matrix materials, realizing the transformation from electron micrographs of material cross-sections to three-dimensional discrete element modeling of carbon fiber toughened ceramic matrix materials.

[0006] A three-dimensional discrete element modeling method for carbon fiber toughened ceramic matrix materials includes the following steps:

[0007] (1) Select the area to be modeled based on the electron microscope image of the cross section of the cut carbon fiber toughened ceramic matrix specimen;

[0008] (2) Use the magnetic lasso tool in Photoshop to select the outer contour of carbon fiber in the selected modeling area of ​​the electron microscope image, remove the carbon fiber located at the edge of the selected area, use the mask tool to set the outer contour area of ​​carbon fiber selected by the magnetic lasso to white, and then adjust the levels to make the selected outer contour area of ​​carbon fiber black.

[0009] (3) By calling the opencv library in Python, the Hough circle transform is used to detect the circle and output the center coordinates of the carbon fiber cross section and the radius of the circle in pixel coordinates.

[0010] (4) Use the coordinate transformation function to convert the coordinates in pixel units to coordinates in length units;

[0011] (5) Set the coordinates of the center of the carbon fiber section under the converted length unit as the coordinates of the center of the carbon fiber section of the carbon fiber model, and build the carbon fiber model through the polyhedral particle command in PFC3D software.

[0012] (6) Fill the modeling areas other than the carbon fiber model area with densely contacted ceramic-based spherical particles;

[0013] (7) Assign particle contact parameters to the carbon fiber model and the ceramic matrix model;

[0014] (8) Finally, a discrete element model of carbon fiber toughened ceramic matrix material is generated.

[0015] The beneficial effects of this invention are as follows: Compared with existing simulation methods, the three-dimensional discrete element modeling method for carbon fiber toughened ceramic matrix materials provided by this invention accurately reproduces the size and distribution of carbon fibers inside the raw material by using the cross-section of the carbon fiber toughened ceramic matrix material observed by electron microscopy. By calibrating the parameters of the internal contact of the material, the mechanical properties of the material itself can be simulated more effectively.

[0016] Furthermore: In step (4), a parameter J is defined such that multiplying the pixel coordinates measured and output in OpenCV by this parameter yields the actual length coordinates.

[0017]

[0018] Where J is the actual length scale possessed by a single pixel, m is the number of pixels at the scale observed by the electron microscope, and l is the unit length of the scale observed by the electron microscope.

[0019] The further beneficial effects mentioned above are: it enables the conversion of coordinates in pixels to coordinates in units of electron microscopy observation, which facilitates the calibration and generation of internal material parameters and improves the efficiency of modeling.

[0020] Furthermore, in step (5), the carbon fiber model is formed by bonding multiple polyhedral particles together using a Linear Parallel Bond Model.

[0021] The further beneficial effects mentioned above are that the carbon fiber model, which is made by bonding multiple polyhedral particles together, can effectively simulate the fracture effect and fit the real material.

[0022] Furthermore, in step (6), when filling with ceramic matrix particles, the ceramic matrix particles are prevented from appearing inside the carbon fiber particles by calling the rangefish command in the fish function library in PFC3D. A wall is built at the boundary of the area to be modeled, so that the ceramic matrix particles fill the area to be modeled.

[0023] The further beneficial effects mentioned above are: by building walls at the boundary and combining them with the set porosity parameters, the internal contact of the material can be made denser, which can effectively simulate the tight structure inside the material. It is more realistic that no ceramic particles appear inside the carbon fiber.

[0024] Furthermore, in step (6), when filling ceramic matrix particles, a Linear Parallel Bond contact model is set between ceramic matrix particles and between the ceramic matrix and carbon fiber particles.

[0025] The further beneficial effect mentioned above is that by setting a linear parallel bond contact model between each contacting particle, the bonding and fracture behavior between powder particles inside the material can be effectively simulated. Attached Figure Description

[0026] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0027] Figure 1 This is a flowchart of the discrete element modeling method for carbon fiber toughened ceramic matrix materials provided in this embodiment of the invention;

[0028] Figure 2 This is a schematic diagram of the Photoshop preprocessing process in an embodiment of the present invention;

[0029] Figure 3 This is a schematic diagram of the spatial coordinate system of the carbon fiber model;

[0030] Figure 4 (a) is a cross-sectional view of the carbon fiber toughened ceramic material model;

[0031] Figure 4 (b) is an overall diagram of the carbon fiber toughened ceramic material model;

[0032] Figure 4 (c) is a cross-sectional view of the carbon fiber toughened ceramic material model. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0034] This invention provides a discrete element modeling method for carbon fiber toughened ceramic matrix materials, such as... Figure 1 As shown, it includes the following steps:

[0035] 1. Select the area to be modeled based on the electron microscope images of the cross-section of the cut carbon fiber toughened ceramic matrix specimen;

[0036] 2. Use the Magnetic Lasso Tool in Photoshop to select the outer contour of the carbon fiber within the selected modeling area in the electron microscope image, remove the carbon fiber located at the edge of the selected area, use the mask tool to set the outer contour area of ​​the carbon fiber selected by the Magnetic Lasso Tool to white, and then adjust the levels to make the selected outer contour area of ​​the carbon fiber black.

[0037] 3. By calling the OpenCV library in Python, the Hough circle transform is used to detect the circles and output the center coordinates of the carbon fiber cross-section and the radius of the circle in pixel coordinates.

[0038] 4. Convert pixel coordinates to length coordinates using the coordinate transformation function;

[0039] 5. Set the coordinates of the carbon fiber cross-section center under the converted length unit as the coordinates of the cross-section center of the carbon fiber model, and build the carbon fiber model using the polyhedral particle command in PFC3D software.

[0040] 6. Fill the modeling areas other than the carbon fiber model area with densely contacted ceramic-based spherical particles;

[0041] 7. Assign contact parameters to the particles in the carbon fiber model and the ceramic matrix model;

[0042] 8. Finally, a discrete element model of carbon fiber toughened ceramic matrix material is generated.

[0043] Step 2 of this embodiment of the invention is specifically as follows:

[0044] 2-1, such as Figure 2As shown in (a), the Magnetic Search tool in Photoshop is used to select the outer contour of the carbon fiber in the image, while the outer contour of the carbon fiber located at the edge of the image is not selected.

[0045] 2-2, such as Figure 2 As shown in (b), the mask tool in Photoshop is used to replace the outer contour area of ​​the carbon fiber selected by the magnetic lasso with white.

[0046] 2-3, such as Figure 2 As shown in (c), use the Levels tool in Photoshop to set the selected carbon fiber outer contour area to black.

[0047] Step 3 of this embodiment of the invention is specifically as follows:

[0048] 3-1. Use the OpenCV library in Python to convert the image of the area to be modeled into a grayscale image;

[0049] 3-2. Use the Gaussian blur and Canny edge detection functions from the OpenCV library in Python, and use the Hough circle transform to identify and detect circles in the image and output their coordinates and radii.

[0050] Step 4 of this embodiment of the invention is specifically as follows:

[0051] 4-1. Measure the number of pixels per unit size in the electron microscope image;

[0052] 4-2. By combining the length of a unit dimension in the electron microscope image with the measured number of pixels occupied by that unit dimension, the actual length scale J of a single pixel can be calculated, as shown in the following formula:

[0053]

[0054] Where J is the actual length scale possessed by a single pixel, m is the number of pixels at the scale observed by the electron microscope, and l is the unit length of the scale observed by the electron microscope.

[0055] like Figure 3 As shown, step 5 of this embodiment of the invention specifically includes:

[0056] 5-1, such as Figure 3 As shown in (a), carbon fiber polyhedral particles are generated by inputting the transformed coordinates in the y and z coordinates respectively using the Cylinder command in PFC3D to generate polyhedral particles.

[0057] 5-2, such as Figure 3As shown in (b), multiple contacting polyhedral particles are generated by using a loop on the x-coordinate, and then combined with the Linear Parallel Bond Model to bond the polyhedral particles into a carbon fiber model.

[0058] 5-3. Repeat the above steps to create multiple carbon fiber models.

[0059] In step (6), when filling the ceramic matrix particles, the fish function is called in PFC3D to ensure that the distance between the ceramic matrix particles and the axis of each carbon fiber is not less than the sum of the radius of the ceramic matrix particles and the radius of the carbon fiber axis, and to ensure that the ceramic matrix particles are generated in the area to be modeled. The solve command is used to make the ceramic spherical particles in close contact with each other and with the carbon fiber polyhedral particles.

[0060] Step 6 of this embodiment of the invention is specifically as follows: 6-1. Define a fish function in PFC3D, such that the pointer type is a spherical particle;

[0061] 6-2. Using the rblock.inside instruction in the fish function, detect whether the spherical particles are inside the polyhedral particles, that is, whether the ceramic matrix particles are inside the carbon fiber particles. If the spherical particles are inside the polyhedral particles, the fish function outputs 1.

[0062] 6-3. Using the range fish and box commands in PFC3D sphere generation, the length, width, and height of the box are equal to the length, width, and height of the modeling area. The box is defined outside the area where the fish function is 1 and is filled with ceramic matrix particles.

[0063] In this embodiment, after the initial particles are generated, the excessive contact force of the particles is released by setting the cycle and solve commands, and the internal balance level is reached.

[0064] Step 7 of this embodiment of the invention is specifically as follows:

[0065] All contact models are assigned the Linear Parallel Bond contact model, and the bond gap parameters are assigned respectively to emod, kratio, pb_emod, pb_kratio, pb_ten, pb_coh, dp_nratio, and firc between carbon fiber linear contacts and between ceramic matrix particles, and the internal forces within the model are cleared to zero.

Claims

1. A three-dimensional discrete element modeling method for carbon fiber toughened ceramic matrix materials, the modeling steps of which are as follows: (1) Select the area to be modeled based on the electron microscope image of the cross section of the cut carbon fiber toughened ceramic matrix specimen; (2) Use the magnetic lasso tool in Photoshop to select the outer contour of carbon fiber in the selected modeling area of ​​the electron microscope image, remove the carbon fiber located at the edge of the selected area, use the mask tool to set the outer contour area of ​​carbon fiber selected by the magnetic lasso to white, and then adjust the levels to make the selected outer contour area of ​​carbon fiber black. (3) By calling the opencv library in Python, the Hough circle transform is used to detect the circle and output the center coordinates of the carbon fiber cross section and the radius of the circle in pixel coordinates. (4) Use the coordinate transformation function to convert the coordinates in pixel units to coordinates in length units; (5) Set the coordinates of the center of the carbon fiber section under the converted length unit as the coordinates of the center of the carbon fiber section of the carbon fiber model, and establish the carbon fiber model by using the cylinder command of the polyhedral particles in PFC3D software; in step (5), multiple cylindrical polyhedral particles are bonded together with the Linear Parallel Bond contact model to form a carbon fiber model. (6) Fill the modeling area other than the carbon fiber model area with densely contacted ceramic-based spherical particles; in step (6) filling ceramic-based particles, call the fish function in PFC3D to make the distance between the ceramic-based particles and the axis of each carbon fiber not less than the sum of the radius of the ceramic-based particles and the radius of the carbon fiber axis, and ensure that the ceramic-based particles are generated in the area to be modeled, and use the solve command to make dense contact between the ceramic-based spherical particles and between the ceramic-based spherical particles and the carbon fiber polyhedral particles. (7) Assign particle contact parameters to the carbon fiber model and the ceramic matrix model; (8) Finally, a discrete element model of carbon fiber toughened ceramic matrix material is generated.

2. The three-dimensional discrete element modeling method for carbon fiber toughened ceramic matrix materials according to claim 1, characterized in that: In step (4), a coordinate system is established with the lower left corner of the image as the origin. Based on the number of pixels and the observation scale of the electron microscope, a parameter J is defined so that the actual length coordinates can be obtained by multiplying the pixel coordinates detected and output by the OpenCV library by this parameter. Where m is the number of pixels at the scale observed by the electron microscope, and l is the unit length at the scale observed by the electron microscope.

3. The three-dimensional discrete element modeling method for carbon fiber toughened ceramic matrix materials according to claim 1, characterized in that: The bonded carbon fiber model fractures under stress along the contact interface of the cylindrical particles, which is used to simulate the fracture behavior of carbon fibers.

4. The three-dimensional discrete element modeling method for carbon fiber toughened ceramic matrix materials according to claim 1, characterized in that: Before filling in step (6), a wall is built at the boundary of the area to be modeled.

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