A force flow enhanced mesostructure design method based on uniform isomorphic grid

Abstract

The application relates to a force flow enhanced mesostructure design method based on a uniform isomorphic grid, which comprises the following steps: S1: determining the load working condition and constraint boundary of a part, carrying out finite element analysis, combining the generation theory of force flow under different forms of representation, drawing a force flow field visualization graph, and using the force flow field visualization graph for subsequent force flow enhanced filling design; S2: constructing a uniform isomorphic model, initially determining the maximum number of force flow lines, calculating the printing volume of the force flow lines, the volume of the force flow lines in the uniform isomorphic network at the overlapping position in the plane, and the volume fraction of the force flow lines; S3: combining the mechanical performance requirement of the part, adjusting the number of force flow lines, and realizing the efficiency maximization of the uniform isomorphic mesostructure for force flow enhancement; S4: for each layer of the part to be filled after slicing, repeating S1-S3, generating multiple design options, determining the stl model of each layer, merging, and generating a final mesostructure model. Compared with the prior art, the application can improve the rigidity and strength of the part.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of mesostructure design, and particularly to a force flow enhanced mesostructure design method based on a homogeneous isomorphic grid. BACKGROUND

[0002] The slice software of the prior art uses a homogeneous mesoscale structure (HMS) to perform filling design on a part, and the mechanical performance of the part is different for different filling patterns, but the homogeneous mesoscale structure has the following characteristics. First, the homogeneous design strategy can fill the entire design space and maintain the geometric characteristics of the outer wall of the part. Second, the quasi-isotropic function of the homogeneous mesoscale structure can reduce abnormal failure of the part under different working loads. Finally, the mechanical performance requirement can be simply matched by adjusting the density and filling direction of the grid, thereby playing a role in optimizing the design of the part.

[0003] However, the homogeneous design method of the prior art does not propose a perfect optimization strategy for improving the load-carrying capacity of the part. In the printing plane, the stress of the homogeneous model is rarely the same in all directions, and damage often occurs at the stress concentration position under specific working conditions. Therefore, the part mesostructure designed based on the homogeneous design method has insufficient stiffness and strength, and the stiffness and strength performance needs to be further improved to achieve a better balance between shape and performance. SUMMARY

[0004] The purpose of the present application is to overcome the defects of the prior art and provide a force flow enhanced mesostructure design method based on a homogeneous isomorphic grid, which can improve the stiffness and strength of the part.

[0005] The purpose of the present application can be achieved by the following technical solutions:

[0006] The present application provides a force flow enhanced mesostructure design method based on a homogeneous isomorphic grid, comprising the following steps:

[0007] S1: determining the load working condition and constraint boundary of the part, performing finite element analysis to obtain the finite element analysis result, calculating the force flow field direction of each node in combination with the generation theory of force flow in different forms, and drawing a force flow field visualization graph;

[0008] S2: constructing a homogeneous isomorphic model, preliminarily determining the maximum number of force flow lines, calculating the printing volume of the force flow lines, calculating the volume of the overlapping part of the force flow lines and the homogeneous isomorphic network in the plane according to the included angle between the force flow lines and the homogeneous isomorphic network, and calculating the volume fraction of the force flow lines according to the homogeneous isomorphic model, the printing volume of the force flow lines, and the volume of the overlapping part;

[0009] S3: According to the volume fraction of force flow lines, combined with the mechanical performance requirements of the part, adjust the number of force flow lines to realize the efficiency maximization of force flow enhancement of uniform mesostructure;

[0010] S4: For each layer of the part to be filled after slicing, repeat S1-S3, generate multiple design options according to different uniform patterns and force flow representation forms, determine the stl model of each layer, merge, and generate the final mesostructure model.

[0011] Preferably, S1 specifically includes the following steps:

[0012] S101: Determine and perform finite element analysis according to the constraints and load boundaries of the part to be filled, get the coordinates of the finite element grid nodes, the size and direction information of the normal stress of each node, and the size and direction information of the shear stress of each node;

[0013] S102: According to the direction information of the normal stress of each node, determine the principal stress trajectory of the part, according to the size information of the shear stress of each node, determine the load path of the part, and then calculate the direction of the force flow field of each node, and draw the visualization graph of the force flow field.

[0014] Preferably, the force flow lines are generated from the constraint boundary according to the direction of the force flow field. According to the load path theory, the endpoints of each force flow line converge to the load boundary, and the force flow lines generated by the principal stress trajectory line meet outside the load boundary.

[0015] Preferably, S2 specifically includes the following steps:

[0016] S201: Set the layer height, shape entity volume, grid filling density and printing volume of the inner and outer wall contour of the target design layer after model slicing, and then build a uniform model;

[0017] S202: Set the printing width of the uniform grid and the force flow line, set the line interval according to the distribution of the force flow line in the dense place, and preliminarily determine the maximum number of force flow lines;

[0018] S203: Set the length of each force flow line and calculate the printing volume of the force flow line;

[0019] S204: Obtain and calculate the volume of the overlap between the force flow line and the uniform network in the plane according to the angle between the force flow line and the uniform network;

[0020] S205: According to the uniform model obtained in S201, the printing volume of the force flow line obtained in S203, and the volume of the overlap obtained in S204, calculate the volume fraction of the force flow line.

[0021] Preferably, the uniform model VHMS The formula is:

[0022] V HMS = pV = pabh

[0023] In the formula, p is the grid filling density, V is the outer shape solid volume of the part, a and b are the length and width of the part respectively, and h is the layer height of the target design layer after the model is sliced.

[0024] Preferably, the printing volume V FF of the force streamline is described by the formula:

[0025]

[0026]

[0027] In the formula, w is the printing width of the homogeneous grid and the force streamline, h is the layer height of the target design layer after the model is sliced, L is the total length of the N force streamlines, and li i is the length of the i-th force streamline.

[0028] Preferably, the volume V cross at the overlapping place of the in-plane force streamline and the uniform homogenous network is described by the formula:

[0029]

[0030] In the formula, w is the printing width of the homogeneous grid and the force streamline, h is the layer height of the target design layer after the model is sliced, and θ j is the included angle of the j-th intersection point of the force streamline and the two types of lines of the uniform homogenous grid, and there are n intersection points.

[0031] Preferably, the volume fraction V of the force streamline is described by the formula:

[0032]

[0033] In the formula, V cross is the volume at the overlapping place of the in-plane force streamline and the uniform homogenous network, V HMs is the uniform homogenous model, and V FF is the printing volume of the force streamline.

[0034] Preferably, the finite element analysis software in S1 is MSC.Nastran, Ansys, Abaqus, Hypermesh, or COMSOL Multiphysics.

[0035] Preferably, the computer-aided design software in S2 is Autodesk Inventor, SolidWorks, CATIA, Pro / E, AutoCAD, or UG NX.

[0036] Compared with the prior art, the present application has the following advantages:

[0037] (1) The present application provides a force flow enhanced mesoscopic structure design method based on uniform isomorphic grid, which applies the theoretical system of force flow enhancement to improve the internal filling mesoscopic structure of 3D printed parts, changes the design and manufacturing method of parts, and provides the possibility for creating lightweight parts and improving the mechanical properties of parts.

[0038] (2) The present application provides a force flow enhanced mesoscopic structure design method based on uniform isomorphic grid, which adjusts the density of force flow lines to control the degree of mechanical property enhancement and the stability of printing process, and finds a balance point between accuracy and economy.

[0039] (3) The present application provides a force flow enhanced mesoscopic structure design method based on uniform isomorphic grid, which realizes the integrated design of part structure and performance by designing the layer combination (different representation forms of force flow-uniform isomorphic grid layer or single uniform isomorphic grid layer) and layer sequence optimization (multi-working condition), and can also realize the design of metamaterial structure by adjusting the layer height, printing width, uniform isomorphic structure filling rate, force flow line volume fraction and other parameters.

[0040] (4) The present application provides a force flow enhanced mesoscopic structure design method based on uniform isomorphic grid, which uses continuous fiber composite material to well bear the area dominated by tensile stress according to the characteristics of force flow lines under principal stress trajectory and load path, but needs to explore suitable matrix materials to realize good combination with uniform isomorphic grid.

[0041] (5) The present application provides a force flow enhanced mesoscopic structure design method based on uniform isomorphic grid, which realizes 2.5-dimensional customization of part performance based on the slice simplification of two-dimensional plane with variable layer height. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 A flowchart of a force flow enhanced mesoscopic structure design method based on uniform isomorphic grid provided for the present embodiment.

[0043] Figure 2 A working condition setting diagram for the lug part.

[0044] Figure 3 A force flow field visualization diagram of the embodiment shown in Figure 2 Figure 3 (a) is the principal stress trajectory, Figure 3 (b) is the load path.

[0045] Figure 4 ​A schematic diagram for calculating the volume fraction of force flow lines based on a uniform isomorphic grid (taking the principal stress trajectory line and the orthogonal grid as an example).

[0046] Figure 5 A schematic diagram for the combination strategy of force flow lines and uniform isomorphic grid, Figure 5 (a) is the superposition in the layer, Figure 5 (b) is the sequence optimization. DETAILED DESCRIPTION

[0047] The present application will be described in detail below with reference to the accompanying drawings and specific embodiments. The embodiments are implemented on the premise of the technical solutions of the present application, and detailed implementation methods and specific operation processes are given, but the protection scope of the present application is not limited to the following embodiments.

[0048] Reference Figure 1 As shown, according to the first aspect of the present application, the embodiment provides a force flow enhanced mesostructure design method based on a uniform isomorphic grid, comprising the following steps:

[0049] S1: determining and performing finite element analysis according to the constraints and load boundaries of the to-be-filled design part, obtaining the finite element analysis results, combining the generation theory of force flow in different forms, calculating the force flow field direction of each node, and drawing the force flow field visualization graph;

[0050] S1 specifically comprises the following steps:

[0051] S101: determining and performing finite element analysis according to the constraints and load boundaries of the to-be-filled design part, obtaining the coordinates of the finite element grid nodes, the size and direction information of the normal stress of each node, and the size and direction information of the shear stress of each node;

[0052] S102: combining the generation theory of force flow in different forms, determining the principal stress trajectory line of the part according to the direction information of the normal stress of each node, determining the load path of the part according to the size information of the shear stress of each node, and then calculating the force flow field direction of each node, and drawing the force flow field visualization graph.

[0053] S2: constructing a uniform isomorphic model, preliminarily determining the maximum number of force flow lines, calculating the printing volume of the force flow lines, calculating the volume of the overlapping part of the force flow lines and the uniform isomorphic network in the plane according to the included angle between the force flow lines and the uniform isomorphic network, and calculating the volume fraction of the force flow lines according to the uniform isomorphic model, the printing volume of the force flow lines and the volume of the overlapping part.

[0054] S2 specifically comprises the following steps:

[0055] S201: setting the layer height, the shape solid volume, the grid filling density and the printing volume of the inner and outer wall contour of the target design layer after the model slicing, and then constructing a uniform isomorphic model;

[0056] As an optional implementation, the uniform homogenous model V HMS The formula is:

[0057] V HMS = pV = pabh

[0058] In the formula, p is the grid filling density, V is the outer shape solid volume of the part, a and b are the length and width of the part respectively, and h is the layer height of the target design layer after the model is sliced.

[0059] S202: Set the printing width of the uniform homogenous grid and the force flow line, set the line interval according to the distribution of the force flow line in the dense place, and preliminarily determine the maximum number N of the force flow line;

[0060] S203: Set the length of each force flow line, and calculate the printing volume of the force flow line;

[0061] The formula for describing the printing volume V FF of the force flow line is:

[0062]

[0063]

[0064] In the formula, w is the printing width of the uniform grid and the force flow line, h is the layer height of the target design layer after the model is sliced, L is the total length of the N force flow lines, and l i is the length of the i-th force flow line.

[0065] S204: Obtain and calculate the volume of the overlap between the in-plane force flow line and the uniform homogenous grid according to the included angle between the force flow line and the uniform homogenous grid;

[0066] The formula for describing the volume V cross of the overlap between the in-plane force flow line and the uniform homogenous grid is:

[0067]

[0068] In the formula, w is the printing width of the uniform grid and the force flow line, h is the layer height of the target design layer after the model is sliced, and θ j is the included angle of the j-th intersection point of the force flow line and the uniform homogenous grid, and there are n intersection points.

[0069] S205: Calculate the volume fraction of the force flow line according to the uniform homogenous model obtained in S201, the printing volume of the force flow line obtained in S203, and the volume of the overlap obtained in S204.

[0070] The formula for describing the volume fraction V of the force flow line is:

[0071]

[0072] In the formula, V cross is the volume of the overlap between the in-plane force flow lines and the uniform isomorphic network, V HMS is the uniform isomorphic model, V FF is the printed volume of the force flow lines.

[0073] S3: According to the force flow line volume fraction, combined with the mechanical performance requirements of the part, adjust the number of force flow lines, realize the efficiency maximization of the uniform isomorphic mesostructure for force flow enhancement;

[0074] S4: For each layer of the part to be filled after slicing, repeat S1-S3, generate multiple design options according to different uniform isomorphic patterns and force flow representation forms, determine the stl model of each layer, merge, and generate the final mesostructure model.

[0075] The finite element analysis software in S1 is MSC.Nastran, Ansys, Abaqus, Hypermesh or COMSOL Multiphysics.

[0076] The computer-aided design software in S2 is Autodesk Inventor, SolidWorks, CATIA, Pro / E, AutoCAD or UG NX.

[0077] In summary, the adjustable filling rate of the uniform isomorphic grid supports the embedding of non-crossing force flow line paths with different densities, which can optimize the part to bear the load demand transmitted along the force flow line path. If the force flow pipe generated by the force flow line can improve the mechanical performance of the part under the premise of maintaining the basic geometry of the part, a mutually optimized part mesostructure design method can be formed. The force flow enhancement mesostructure design method based on the uniform isomorphic grid provided by the present application uses the force flow theory to convert the uniform isomorphic mesostructure into a non-uniform isomorphic structure, which reduces the unpredictable random factors that cause the failure of the part, and at the same time, the mechanical performance of the overall structure is regulated by the stress field, so that higher strength and stiffness can be obtained under actual working conditions. The part can achieve a better balance between shape and performance, thereby improving the functionality and material utilization efficiency of the structure as a whole.

[0078] Any combination of the above preferred embodiments can result in a more optimal embodiment, and the following will describe an optimal embodiment obtained by combining all the embodiments.

[0079] Reference Figure 2As shown, taking the mesoscopic structure design of the lifting lug part as an example, the external dimensions of the lifting lug part are set as length a = 140, width b = 30mm, and height c = 3mm. The lifting lug part has a circular hole with a diameter of 10mm. The center of the circular hole is 30mm away from the wide side. A three-dimensional model of the sample is established in SolidWorks.

[0080] S101: The load-bearing capacity of this lifting lug component is set. Direction and Cartesian coordinate system With the directions in the same direction, divide the part clamping area A and the load application area A', and determine the constraint boundary B. c and load boundary B f ; Set experimental parameters, perform finite element analysis, and obtain the coordinates (x, y) of the finite element mesh nodes and the normal stress σ of each node. x The magnitude and direction information, and the shear stress τ at each node. xy Size and orientation information.

[0081] S102: Based on the generation theory of force flow under different representation forms, calculate the direction of the force flow field at each node. And draw a visualization of the force flow field;

[0082] The force-flow field visualization includes principal stress trajectory graphs and load path graphs, based on the normal stress σ at each node. x The directional information determines the principal stress trajectory of the lifting lug component. Based on the magnitude of the shear stress at each node, and according to tanθ=τ xy / σ x Determine the load path of the lifting lug parts.

[0083] refer to Figure 3 As shown, from the constraint boundary B c Starting from the force flow field Draw the force streamlines. Generally, under load path theory, the endpoint of each force streamline converges to the load boundary B. f At the point where the force flow lines generated by the principal stress trajectory line can converge outside the load boundary.

[0084] S201: Set the layer height of the target design layer after slicing the model to h, the volume of the external solid to V, the mesh fill density to ρ, and the printing volume of the inner and outer wall contours to V. c ρ = (VV) can be calculated. c ) / V=V HMS / V, thus obtaining the homogeneous isomorphic model V HMS =ρV=ρabh;

[0085] S202: Reference Figure 4As shown, the printing width of the uniform grid and the force flow line is w, the line interval is set according to the distribution of the force flow line in the dense place, the overlap between the force flow lines is ensured to be negligible, and the maximum number N of the force flow lines can be obtained initially;

[0086] S203: The length of the i-th force flow filling line is l i The total length of the N force flow lines is The printing volume of the force flow line is

[0087] S204: The angle between the force flow line and the uniform and isomorphic grid is θ j The volume of the overlap between the two in the plane is

[0088] S205: According to the uniform and isomorphic model obtained in S201, the printing volume of the force flow line obtained in S203, and the volume of the overlap obtained in S204, the volume fraction of the force flow line is calculated:

[0089]

[0090] S3: According to the volume fraction of the force flow line, the number of force flow lines is adjusted to realize the efficiency maximization of the uniform and isomorphic mesostructure for force flow enhancement, combined with the mechanical performance requirements of the part;

[0091] S4: For each layer of the part to be filled after slicing, S1-S3 is repeated, and different uniform and isomorphic patterns and force flow representation forms are generated, such as Figure 5 (a) Multiple design options, including rectangular, triangular and honeycomb;

[0092] The stl model of each layer is determined, combined, and the final mesostructure model is generated. Of course, the selection of the force flow enhancement layer is self-defined and can be optimized in layer sequence, such as Figure 5 (b) As shown, different design patterns in different layers are arranged in different numbers and positions, and a combination strategy that meets the mechanical performance requirements can also be formed according to the actual multi-working condition requirements of the part.

[0093] The above describes the preferred embodiments of the application in detail. It should be understood that those skilled in the art can make many modifications and changes without creative labor according to the concept of the application. Therefore, any technical solution obtained by logical analysis, reasoning or limited experiment based on the prior art according to the concept of the application shall be within the protection scope determined by the claims.

Claims

1. A method for designing a force flow enhanced mesostructure based on a uniform, isomorphic grid, characterized by, It comprises the following steps: S1: determining the load condition and constraint boundary of the part, performing finite element analysis to obtain the finite element analysis result, combining the generation theory of force flow in different forms, calculating the force flow field direction of each node, and drawing the force flow field visualization graph; S2: constructing a uniform isomorphic model, preliminarily determining the maximum number of force flow lines, calculating the printing volume of the force flow lines, calculating the volume of the overlapping part of the force flow lines and the uniform isomorphic network in the plane according to the included angle between the force flow lines and the uniform isomorphic network, and calculating the volume fraction of the force flow lines according to the uniform isomorphic model, the printing volume of the force flow lines and the volume of the overlapping part; S3: adjusting the number of force flow lines according to the volume fraction of the force flow lines, combining the mechanical performance requirements of the part, and realizing the efficiency maximization of the uniform isomorphic mesostructure for force flow enhancement; S4: for each layer of the part to be filled after slicing, repeating S1-S3, generating multiple design options according to different uniform isomorphic patterns and force flow representation forms, determining the stl model of each layer, merging, and generating the final mesostructure model; The S2 specifically comprises the following steps: S201: setting the layer height, shape entity volume, grid filling density and printing volume of the inner and outer wall contour of the target design layer after model slicing, and then constructing a uniform isomorphic model; S202: setting the printing width of the uniform isomorphic grid and the force flow line, setting the line interval according to the distribution of the force flow lines in the dense part, and preliminarily determining the maximum number of force flow lines; S203: setting the length of each force flow line, and calculating the printing volume of the force flow lines; S204: obtaining and calculating the volume of the overlapping part of the force flow lines and the uniform isomorphic network in the plane according to the included angle between the force flow lines and the uniform isomorphic network; S205: calculating the volume fraction of the force flow lines according to the uniform isomorphic model obtained in S201, the printing volume of the force flow lines obtained in S203 and the volume of the overlapping part obtained in S204.

2. The method of claim 1, wherein, The S1 specifically comprises the following steps: S101: determining and according to the constraint and load boundary of the part to be filled design, performing finite element analysis to obtain the coordinates of the finite element grid nodes, the size and direction information of the normal stress of each node, and the size and direction information of the shear stress of each node; S102: combining the generation theory of force flow in different forms, determining the principal stress trajectory of the part according to the direction information of the normal stress of each node, determining the load path of the part according to the size information of the shear stress of each node, and then calculating the force flow field direction of each node and drawing the force flow field visualization graph.

3. The method of claim 2, wherein, The force flow lines are generated from the constraint boundary according to the force flow field direction, and under the load path theory, the endpoints of each force flow line converge to the load boundary, and the force flow lines generated by the principal stress trajectory line meet outside the load boundary.

4. The method of claim 1, wherein, Describing uniform isomorphic models The formula is: In the formula, grid packing density, is the outer shape volume of the part, , are the length and width of the part, respectively, h is the layer height of the target design layer after slicing the model.

5. The method of claim 1, wherein, Printed volume describing force flow lines The formula is: wherein w is the print width of the uniform grid and force flow lines, h is the layer height of the target design layer after slicing the model, L is the N is the total length of the force flow lines, is the length of the force flow line, i is the length of the force flow line.

6. The method of claim 1, wherein, Describing the volume where in-plane force streamlines overlap with a homogeneous isomorphic network The formula is: In the formula, w is the printing width of the uniform grid and force flow line, h is the layer height of the target design layer after the model is sliced, The angle between the two types of lines of the force flow line and the uniform isomorphic grid j There are a total of n intersection points.

7. The method of claim 1, wherein, Describing the volume fraction of force flow lines The formula is: wherein is the volume of the in-plane force flow lines overlapping with the uniform homogenous network, is the uniform homogenous model, is the printed volume of the force flow lines.

8. The method of claim 1, wherein, The finite element analysis software in S1 is MSC.Nastran, Ansys, Abaqus, Hypermesh or COMSOL Multiphysics.

9. The method of claim 1, wherein, The computer-aided design software in S2 is Autodesk Inventor, SolidWorks, CATIA, Pro / E, AutoCAD or UG NX.

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