Stress-driven lattice porous structure local optimization method

Abstract

The invention discloses a stress-driven lattice porous structure local optimization method, which comprises the following steps of: simulating a stress condition of a lattice porous structure under a corresponding load service condition by adopting finite element simulation software, and acquiring stress distribution; performing structure segmentation treatment on the lattice porous structure to obtain a plurality of small-size structures; all Von Mises stress values on each small-size structure are obtained through the grid units, all Von Mises stress values on each small-size structure are quantified through a statistical analysis method, and the stress level of each small-size structure is obtained; according to the stress level of each small-size structure and a set scaling rule, judging whether each small-size structure is in a scaled-in size or a scaled-out size, and sequentially adjusting the size of each small-size structure based on the type of the dot matrix porous structure; and if the designed dot matrix porous structure does not reach the optimization target, repeating the steps to carry out iterative optimization for multiple times until the optimization target is reached, so that the optimized dot matrix porous structure is obtained.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing technology, and in particular to a stress-driven method for local optimization of lattice porous structures. Background Technology

[0002] Additive manufacturing is a technology that uses high-energy heat sources such as lasers, electric arcs, and ion beams to heat and melt metal powder, then deposits it layer by layer according to a pre-defined two-dimensional pattern to form a three-dimensional solid. This technology can be used to manufacture complex and delicate metal parts, has a wide range of applications, and promising development prospects. However, in actual manufacturing processes, material waste or insufficient performance are inevitable. When the material distribution is unreasonable, excessive material accumulation in local areas can lead to waste, or insufficient filling can result in uneven structure and inconsistent performance of the formed part. This can cause problems such as excessively high production costs, difficulty in controlling the yield rate of finished products, and failure to meet expected performance requirements. Meanwhile, some researchers have proposed a gradient lattice material optimization design approach based on machine learning. This approach uses a random forest model to predict mechanical response and optimizes structural parameters with the goal of increasing peak stress. However, this method relies on historical data statistical prediction and lacks a stress optimization mechanism driven by physical mechanisms and the ability to adjust locally. Summary of the Invention

[0003] Purpose of the invention: In order to overcome the shortcomings of the existing technology, the present invention provides a stress-driven local optimization method for lattice porous structures. Based on the local stress level of the lattice porous structure, the local dimensions of the structure are adjusted by increasing or decreasing, thereby maximizing the improvement of various mechanical properties of the lattice porous structure; achieving the purpose of local optimization, and designing a novel thin-walled lattice porous structure.

[0004] Technical solution: To achieve the above objectives, the present invention provides a stress-driven local optimization method for lattice porous structures, comprising the following steps:

[0005] Step 1: Use finite element simulation software to simulate the stress of the lattice porous structure under the corresponding load service conditions, and obtain the stress distribution of the lattice porous structure under the corresponding load service conditions.

[0006] Step 2: Perform structural segmentation on the lattice porous structure to obtain several small-sized structures;

[0007] Step 3: Use mesh elements to obtain all Von Mises stress values ​​on each small-sized structure, and quantify all Von Mises stress values ​​on each small-sized structure through statistical analysis methods to obtain the stress level of each small-sized structure;

[0008] Step 4: Determine whether each small-sized structure is enlarged or reduced in size based on the stress level and the set scaling rules for each small-sized structure, and adjust the size of each small-sized structure in turn based on the type of lattice porous structure.

[0009] Step 5: Determine whether the designed lattice porous structure has achieved the set optimization target. If not, repeat steps 1 to 4 for multiple iterations of optimization until the designed lattice porous structure achieves the optimization target. If it has, the optimized lattice porous structure is obtained.

[0010] Based on the above-mentioned local optimization method for lattice porous structures, a thin-walled lattice porous structure is analyzed and designed. Then, the size of each small structure of the designed thin-walled lattice porous structure is adjusted by the above-mentioned local optimization method for lattice porous structures to achieve local optimization and obtain the final thin-walled lattice porous structure.

[0011] The final thin-walled lattice porous structure comprises a square-frame-shaped enclosed load-bearing member containing a network of strip-shaped support units interconnected along a planar direction. On this support network, the mesh area increases towards the center and decreases towards the edges. The support network is divided into a first stress zone, a second stress zone, a third stress zone, and a fourth stress zone. The support units in the first and third stress zones are thinner than those in the second and fourth stress zones. Furthermore, based on the optimization objectives of the thin-walled lattice porous structure, support units with low stress levels in the first and third stress zones are removed.

[0012] Furthermore, in step two, the lattice porous structure includes a pillar-type lattice porous structure and a thin-walled lattice porous structure; the structure segmentation process involves equally spaced segments of each pillar in the pillar-type lattice porous structure to obtain several small-sized structures; and equally spaced segments of each thin wall in the thin-walled lattice porous structure to obtain several small-sized structures.

[0013] Furthermore, in step three, for any small-sized structure comprising several mesh elements, based on the position of each mesh element and the corresponding Von Mises stress value, all Von Mises stress values ​​of the small-sized structure are obtained; the average value of all Von Mises stress values ​​of the small-sized structure is calculated as the stress level, and the calculation process is as follows:

[0014]

[0015] In the formula, n represents the number of mesh elements on the small-sized structure, and S m It represents the average of all VonMises stress values ​​for a small-sized structure.

[0016] Furthermore, in step four, the set scaling rules include a phased scaling rule and a linear scaling rule; the phased scaling rule is to compare the stress level of each small-sized structure with a set stress threshold range, and when the stress level of any small-sized structure is higher than the highest stress threshold of the stress threshold range, then the size of the small-sized structure is increased by a set increase size; when the stress level of any small-sized structure is lower than the lowest stress threshold of the stress threshold range, then the size of the small-sized structure is decreased by a set decrease size.

[0017] Furthermore, the linear scaling rule adjusts the size of the small-sized structure linearly according to the stress level of each small-sized structure; the stress level is normalized to obtain S. n Stress range, according to S n The stress range and the set scaling factor linearly increase or decrease the size of small structures. The calculation process is shown below:

[0018]

[0019] In the formula, D i D represents the cross-sectional area before adjustments to the small-sized structure. m Let S represent the adjusted cross-sectional area of ​​the small-sized structure, where 'a' represents the scaling factor of the cross-sectional area of ​​the small-sized structure at the minimum stress level, and 'b' represents the scaling factor of the cross-sectional area of ​​the small-sized structure at the maximum stress level. n S represents the stress range after stress level normalization. n ∈[0,1].

[0020] Furthermore, a thin-walled lattice porous structure is provided, comprising an enclosed load-bearing member with a square frame cross-section; within the enclosed load-bearing member with a square frame cross-section, there is a network of support structures formed by several strip-shaped support units connected to each other along the planar direction, the edge of the support structure network being integrally connected to the inner circle of the enclosed load-bearing member with a square frame cross-section; a mesh group is formed on the support structure network, each mesh group being enclosed by at least three support units, and a load-bearing node is formed at the connection point of any two support units in the support structure network.

[0021] Furthermore, in the central region of the mesh group, there is a mesh that is larger than the other meshes; this mesh is referred to as the central mesh. The closer the mesh is to the central mesh on the support structure network, the larger its mesh area tends to be. The closer the mesh is to the enclosed load-bearing member with a square cross-section on the support structure network, the smaller its mesh area tends to be.

[0022] Furthermore, the enclosed load-bearing member with a square cross-section includes, in a clockwise direction, a first side, a second side, a third side, and a fourth side. Under actual stress, the second and fourth sides are compressed on their outer sides, while the first and third sides are in a free state, unaffected by external forces. The connection between the first and second sides forms a first frame node, the connection between the second and third sides forms a second frame node, the connection between the third and fourth sides forms a third frame node, and the connection between the fourth and first sides forms a fourth frame node. The triangular region formed by the central mesh, the first frame node, and the second frame node is the first stress zone; the triangular region formed by the central mesh, the second frame node, and the third frame node is the second stress zone; the triangular region formed by the central mesh, the third frame node, and the fourth frame node is the third stress zone; and the triangular region formed by the central mesh, the fourth frame node, and the first frame node is the fourth stress zone. The support units in the first and third stress zones of the support structure network are thinner than the support units in the second and fourth stress zones.

[0023] Furthermore, the support unit closest to the central mesh in the first stress zone is removed, so that the mesh area of ​​the mesh closest to the central mesh in the first stress zone is approximately equal to that of the central mesh; the support unit closest to the central mesh in the third stress zone is also removed, so that the mesh area of ​​the mesh closest to the central mesh in the third stress zone is approximately equal to that of the central mesh.

[0024] Furthermore, the support units in the first and third stress zones with stress levels below the set stress threshold are removed, so that the mesh area in the first and third stress zones is approximately equal to that in the central mesh.

[0025] Beneficial Effects: This invention provides a stress-driven local optimization method for lattice porous structures. By simulating the stress distribution of the lattice porous structure under corresponding load service conditions using finite element simulation software, and adjusting the local dimensions of the structure by increasing or decreasing them based on the local stress level, the method achieves refined local optimization of the lattice porous structure, thereby maximizing its mechanical properties. The method also allows for targeted adjustment of the dimensional parameters of each small-sized structure according to the local stress level, increasing the structural size in areas of high stress and decreasing it in areas of low stress, thus achieving local optimization. This method is applicable to both support-type and thin-walled lattice structures, significantly improving the uneven stress distribution problem and greatly enhancing its overall load-bearing capacity. Furthermore, a novel thin-walled lattice porous structure is designed, increasing structural strength while maintaining or reducing structural weight. Attached Figure Description

[0026] Figure 1 A flowchart of a stress-driven local optimization method for lattice porous structures;

[0027] Figure 2 Stress distribution diagram of a cross-section of a novel thin-walled lattice porous structure;

[0028] Figure 3 The stress distribution diagram of the optimized new thin-walled lattice porous structure cross section;

[0029] Figure 4 This is a stress distribution diagram of the cross-section of a novel thin-walled lattice porous structure after a second optimization.

[0030] Figure 5 Stress distribution diagram of a cross-section of a novel thin-walled lattice porous structure after a second optimization;

[0031] Figure 6 To optimize the three-dimensional solid schematic diagram, stress distribution diagram, and force-displacement curve diagram of the front support-type body-centered cubic lattice structure;

[0032] Figure 7 To optimize the three-dimensional solid schematic diagram, stress distribution diagram, and force-displacement curve of the body-centered cubic lattice structure of the support column;

[0033] Figure 8 To optimize the 3D solid model, stress distribution diagram, and force-displacement curve of the front support type random lattice structure;

[0034] Figure 9 This document presents a 3D solid model, stress distribution diagram, and force-displacement curve of the optimized column-type random lattice structure. Detailed Implementation

[0035] The invention will now be further described with reference to the accompanying drawings.

[0036] like Figure 1 As shown, a stress-driven local optimization method for lattice porous structures includes the following steps:

[0037] Step 1: Use finite element simulation software to simulate the stress of the lattice porous structure under the corresponding load service conditions, and obtain the stress distribution of the lattice porous structure under the corresponding load service conditions.

[0038] Step 2: Perform structural segmentation on the lattice porous structure to obtain several small-sized structures;

[0039] Step 3: Use mesh elements to obtain all Von Mises stress values ​​on each small-sized structure, and quantify all Von Mises stress values ​​on each small-sized structure through statistical analysis methods to obtain the stress level of each small-sized structure;

[0040] Step 4: Determine whether each small-sized structure is enlarged or reduced in size based on the stress level and the set scaling rules for each small-sized structure, and adjust the size of each small-sized structure in turn based on the type of lattice porous structure.

[0041] Step 5: Determine whether the designed lattice porous structure meets the set optimization target, which is the design requirement for each lattice porous structure. If not, repeat steps 1 to 4 for multiple iterations until the designed lattice porous structure meets the optimization target. If it does, the optimized lattice porous structure is obtained. Based on the adjusted size of the small-sized structure and its location, the adjusted and optimized lattice porous structure can be obtained by manual modeling using 3D drawing software, or by algorithm modeling using computer language.

[0042] Based on the above-mentioned local optimization method for lattice porous structures, a thin-walled lattice porous structure is analyzed and designed. Then, the size of each small structure of the designed thin-walled lattice porous structure is adjusted by the above-mentioned local optimization method for lattice porous structures to achieve local optimization and obtain the final thin-walled lattice porous structure.

[0043] The final thin-walled lattice porous structure has a square-frame-shaped enclosed load-bearing member 1 containing a network of support units 2 connected along the plane. On this support network, the mesh area of ​​the mesh 3 closer to the center tends to increase, while the mesh area closer to the edges tends to decrease. The support network is divided into a first stress zone 41, a second stress zone 42, a third stress zone 43, and a fourth stress zone 44. The support units 2 in the first and third stress zones 41 and 43 are thinner than those in the second and fourth stress zones 42 and 44. Based on the optimization goals of the thin-walled lattice porous structure, support units 2 with low stress levels in the first and third stress zones 41 and 43 are removed.

[0044] To determine whether the designed lattice porous structure has achieved the set optimization target, the structural strength can be estimated based on the stress distribution of the lattice porous structure after adjusting its size, and the structural weight can be calculated based on the shape of the lattice porous structure after adjusting its size. The obtained structural strength and structural weight are then compared with corresponding thresholds. The structural strength of the lattice porous structure is compared with the strength threshold. If the structural strength is lower than the strength threshold, the optimization target has not been achieved. The structural weight of the lattice porous structure is compared with the weight threshold. If the structural weight is higher than the weight threshold, the optimization target has not been achieved. When the structural strength of the lattice porous structure is equal to or higher than the strength threshold, and the structural weight of the lattice porous structure is equal to or lower than the weight threshold, the lattice porous structure has achieved the optimization target.

[0045] The finite element simulation software includes, but is not limited to, ANSYS, ABAQUS, or COMSOL Multiphysics, and also includes self-developed scripts. The load service conditions include static load service conditions, dynamic load service conditions, and fatigue load service conditions. The specific load service conditions used are selected for each lattice porous structure based on its actual usage. Statistical analysis methods can be employed through manual calculation or self-designed scripts to calculate the maximum, minimum, and average values ​​of all Von Mises stresses for each small-sized structure. The optimization objectives include minimizing structural weight, homogenizing stress distribution, and maximizing structural strength. The materials used in the lattice porous structures include metallic materials, composite materials, and polymer materials, etc.

[0046] In step two, the lattice porous structure includes a pillar-type lattice porous structure and a thin-walled lattice porous structure. The structure segmentation process involves equally spaced segments of each pillar in the pillar-type lattice porous structure to obtain several smaller structures; and equally spaced segments of each thin wall in the thin-walled lattice porous structure to obtain several smaller structures. Specifically, each thin wall is equally spaced along the perpendicular direction of the cross-section of the thin-walled lattice porous structure. The segmented smaller structures contain n grid units, where n > 0, and the recommended segmentation size is 1 to 3 times the average size of the grid units. The equally spaced segmentation of each pillar means segmenting each pillar at the same interval, for example, segmenting each pillar at a interval twice the average size of the grid units. The equally spaced segmentation of each thin wall means segmenting each thin wall at the same interval along the perpendicular direction of the cross-section, for example, segmenting each thin wall at a interval three times the average size of the grid units.

[0047] The equidistant division of each support or thin wall can also be adjusted based on the average Von Mises stress value of all supports or thin walls. A larger average Von Mises stress value results in a smaller division spacing, and vice versa. Specifically, the average Von Mises stress value is normalized and multiplied by the unit spacing value to obtain the division spacing for each support or thin wall. The division spacing for each support is then linearly adjusted. The minimum spacing is one times the average size of the grid cells, and the maximum spacing is three times the average size of the grid cells. The unit spacing value is adjusted according to actual requirements and can be set to three times the average size of the grid cells. The structural division process also includes equal-area division, adaptive division based on stress gradient, or no division, etc., with the division method selected based on the size of the lattice porous structure or other practical considerations.

[0048] In step three, for any small-sized structure comprising several mesh elements, based on the position of each mesh element and the corresponding Von Mises stress value, all Von Mises stress values ​​of the small-sized structure are obtained. Statistical analysis is used to quantify all Von Mises stress values ​​for each small-sized structure, and the average value of all Von Mises stress values ​​is calculated as the stress level. The calculation process is as follows:

[0049]

[0050] In the formula, n represents the number of mesh elements on the small-sized structure, and S mThis represents the average of all Von Mises stress values ​​for a small-sized structure. The stress level can be adjusted based on the specific circumstances, selecting either the maximum or minimum Von Mises stress value for the small-sized structure, or combining two or more of the maximum, minimum, and average values ​​to represent the stress level.

[0051] In step four, the set scaling rules include a phased scaling rule and a linear scaling rule. The phased scaling rule compares the stress level of each small-sized structure with a set stress threshold range. When the stress level of any small-sized structure is higher than the highest stress threshold of the stress threshold range, the size of that small-sized structure is increased by a set increment; when the stress level of any small-sized structure is lower than the lowest stress threshold of the stress threshold range, the size of that small-sized structure is decreased by a set decrement. The increment is set according to the actual situation. For example, if the increment is set to 4 times, then each adjustment will increase the size of the small-sized structure to 4 times its original size. The decrement is set according to the actual situation. For example, if the decrement is set to 1 / 4 times, then each adjustment will increase the size of the small-sized structure to 1 / 4 of its original size.

[0052] The linear scaling rule adjusts the size of the small-sized structure linearly according to the stress level of each small-sized structure; the stress level is normalized to obtain S. n Stress range, according to S n The stress range and the set scaling factor linearly increase or decrease the size of small structures. The calculation process is shown below:

[0053]

[0054] In the formula, D i D represents the cross-sectional area before adjustments to the small-sized structure. m Let S represent the adjusted cross-sectional area of ​​the small-sized structure, where 'a' represents the scaling factor of the cross-sectional area of ​​the small-sized structure at the minimum stress level, and 'b' represents the scaling factor of the cross-sectional area of ​​the small-sized structure at the maximum stress level. n S represents the stress range after stress level normalization. n∈[0, 1]. This refers to the scaling factor 'a' of the cross-sectional area of ​​the small-sized structure at the minimum stress level and the scaling factor 'b' of the cross-sectional area of ​​the small-sized structure at the maximum stress level. When the small-sized structure is a reduced size, 'a' becomes the value corresponding to the reduction factor of the cross-sectional area of ​​the small-sized structure at the minimum stress level; 'b' becomes the value corresponding to the reduction factor of the cross-sectional area of ​​the small-sized structure at the maximum stress level. When the small-sized structure is an enlarged size, 'a' becomes the value corresponding to the enlargement factor of the cross-sectional area of ​​the small-sized structure at the minimum stress level; 'b' becomes the value corresponding to the enlargement factor of the cross-sectional area of ​​the small-sized structure at the maximum stress level.

[0055] Based on the type of lattice porous structure, the dimensions of each small structure are adjusted sequentially. When it is determined whether the size of each small structure is increased or decreased, for the column-type lattice porous structure, the increase or decrease of the size of each column is manifested as an increase or decrease of the cross-sectional area of ​​each column, specifically by increasing or decreasing the diameter of each column. For the thin-walled lattice porous structure, the increase or decrease of the size of each thin wall is manifested as an increase or decrease of the cross-sectional area of ​​each thin wall, specifically by increasing or decreasing the thickness of each thin wall, thereby increasing or decreasing the cross-sectional area of ​​each column.

[0056] The optimization objectives include minimizing structural weight, homogenizing stress distribution, and maximizing structural strength. The segmentation spacing, stress threshold range, scaling factor 'a' (for the cross-sectional area of ​​the smallest structure at the minimum stress level), and scaling factor 'b' (for the cross-sectional area of ​​the smallest structure at the maximum stress level) are adjusted according to different optimization objectives. This allows for more efficient adjustment of the dimensions of each small structure within the lattice porous structure, enabling the lattice porous structure to achieve its optimization objectives more quickly. For example, when the optimization objective is to homogenize stress distribution, the segmentation spacing of each support is equal; the highest and lowest stress thresholds within the stress threshold range are equal; and the scaling factors 'a' and 'b' are adjusted according to actual conditions. For example, when the optimization objective is to maximize structural strength, the spacing between each support column is adjusted according to the average value of all Von Mises stress values ​​on each support column. The larger the average value of all Von Mises stress values ​​on the support column, the smaller the spacing between the columns; the smaller the average value of all Von Mises stress values ​​on the support column, the larger the spacing between the columns. The stress threshold range and scaling factors a and b are adjusted according to the actual situation.

[0057] like Figure 2As shown, the cross-section of a conventional thin-walled lattice porous structure can be composed of several identical rectangular meshes or several identical honeycomb meshes, wherein the honeycomb meshes are hexagonal meshes of the same shape and size. Finite element simulation software was used to simulate the stress conditions of thin-walled lattice porous structures with identical rectangular meshes and those with identical honeycomb meshes under corresponding load service conditions, and the stress distribution of these two types of lattice porous structures under corresponding load service conditions was obtained. The stress distribution revealed that some thin-walled sections of these two types of lattice porous structures have very high stress, while others have very low stress. The thin-walled sections with high stress bear significant pressure, and prolonged exposure to this pressure may cause the corresponding thin-walled sections to bend, rendering them unable to withstand further pressure, thus reducing the structural strength of the lattice porous structure. The thin-walled sections with very low stress bear very little or almost no pressure; therefore, this portion of the thin-walled sections with low stress not only does not enhance the structural strength of the lattice porous structure but also increases its weight. Therefore, the stress distribution of the thin-walled lattice porous structure is obtained by analyzing the method of this invention. Specifically, finite element simulation software is used to simulate the load service conditions of the thin-walled lattice porous structure under pressure applied to the upper and lower sides of the stressed component, and the stress distribution of the lattice porous structure under these load service conditions is obtained. Based on the stress distribution, the connection structure of the thin-walled lattice porous structure is designed and optimized, resulting in a novel thin-walled lattice porous structure. In the stress distribution diagram, the redder the color, the higher the stress; the bluer the color, the lower the stress.

[0058] A thin-walled lattice porous structure includes an enclosed load-bearing member 1 with a square cross-section frame. Within the enclosed load-bearing member 1, several strip-shaped support units 2 are interconnected along a planar direction to form a support structure network. The edges of the support structure network are integrally connected to the inner ring of the enclosed load-bearing member 1. A mesh group is formed on the support structure network, and each mesh 3 is enclosed by at least three support units 2. A load-bearing node 20 is formed at the connection point of any two support units 2 in the support structure network. The strip-shaped support units 2 are thin-walled, and the support structure network composed of these thin walls is integrally connected to the enclosed load-bearing member 1 with the support structure network to obtain the thin-walled lattice porous structure. The enclosed load-bearing member 1 with the square cross-section frame is formed by four thin-walled members.

[0059] In the central region of the mesh group, there is a mesh 3 that is larger than the other meshes 3, and this mesh 3 is referred to as the central mesh 31; the closer the mesh 3 is to the central mesh 31 on the support structure network, the larger its mesh area tends to be; the closer the mesh 3 is to the enclosed force-bearing member 1 with a square cross-section on the support structure network, the smaller its mesh area tends to be.

[0060] In thin-walled lattice porous structures with identical honeycomb mesh cross-sections and those with identical rectangular mesh cross-sections, increasing the structural strength of the thin-walled lattice porous structure can be achieved by reducing the size of the rectangular or honeycomb meshes and increasing the number of thin-walled sections, but this increases the structural weight. Conversely, reducing the structural weight can be achieved by enlarging the rectangular or honeycomb meshes, reducing the number of thin-walled sections, and increasing the length of the thin-walled sections, but this reduces the structural strength. For components with design requirements for both structural strength and weight, it is difficult to meet the design requirements using either thin-walled lattice porous structures with identical honeycomb or rectangular mesh cross-sections. Figure 2 As shown, the present invention redesigns a novel thin-walled lattice porous structure in which the meshes closer to the central mesh 31 tend to be larger, and the meshes closer to the enclosed load-bearing members with a square cross-section tend to be smaller; while reducing the structural weight of the novel thin-walled lattice porous structure, it can maintain or improve the structural strength of the novel thin-walled lattice porous structure.

[0061] Each mesh in the mesh group is enclosed by at least three support units 2. The closer the mesh is to the central mesh 31 on the support structure network, the more sides the mesh shape tends to have; the closer the mesh is to the enclosed load-bearing member 1 with a square cross-section on the support structure network, the fewer sides the mesh shape tends to have. The central mesh 31 is an octagonal mesh, which can be an irregular octagon enclosed by eight support units 2. The other edge meshes include hexagons, pentagons, quadrilaterals, and trilaterals, which can be irregular shapes enclosed by no fewer than three support units, and the support units 2 enclosed by other meshes do not exceed eight.

[0062] In thin-walled lattice porous structures employing several identical honeycomb meshes and several identical rectangular meshes, if the mesh size near the central region is increased while the mesh size near the square-framed load-bearing member 1 is decreased, increasing the mesh size in the central region, while reducing the structural weight, compromises structural strength. This is because the increased mesh size in the central region, under prolonged and significant pressure, could cause the thin walls of the central region to bend, rendering it unable to withstand the pressure. Figure 2 As shown, the shape of several meshes is adjusted by stress distribution in the thin-walled lattice porous structure. The meshes closer to the central mesh 31 tend to have more edges, while the meshes closer to the enclosed load-bearing member 1 with a square cross-section tend to have fewer edges. This allows the structural strength of the new thin-walled lattice porous structure to be reduced as much as possible by minimizing the number of thin walls to reduce structural weight, while maintaining or increasing the corresponding structural strength.

[0063] like Figure 3 As shown, the novel thin-walled lattice porous structure undergoes a first optimization using the stress-driven local optimization method for lattice porous structures described in this invention, resulting in an optimized novel thin-walled lattice porous structure. The stress distribution diagram shows that the stress distribution of the thin-walled structure in the first and third stress regions is smaller compared to other parts, and the pressure it bears is also smaller compared to other thin-walled sections. Therefore, through the method of this invention, refined local optimization is performed. In areas with higher stress, the structural dimensions are increased, specifically in the second and fourth stress regions, increasing the thin-wall dimensions and thickness to bear more pressure. In areas with lower stress, the structural dimensions are reduced, specifically in the first and third stress regions, decreasing the thin-wall dimensions and thickness to reduce the pressure it bears. This further enhances the structural strength of the novel thin-walled lattice porous structure while maintaining or reducing its structural weight.

[0064] like Figure 3As shown, the enclosed load-bearing member 1 with a square cross-section includes, in a clockwise direction, a first side 11, a second side 12, a third side 13, and a fourth side 14. Under actual stress, the second side 12 and the fourth side 14 are compressed on their outer sides, while the first side 11 and the third side 13 are in a free state, unaffected by external forces. The connection between the first side 11 and the second side 12 forms a first frame node 21, the connection between the second side 12 and the third side 13 forms a second frame node 22, the connection between the third side 13 and the fourth side 14 forms a third frame node 23, and the connection between the fourth side 14 and the first side 11 forms a fourth frame node 24. The triangular region formed by the connection of the central mesh 31, the first frame node 21, and the second frame node 22 is the first stress region 41; the triangular region formed by the connection of the central mesh 31, the second frame node 22, and the third frame node 23 is the second stress region 42; the triangular region formed by the connection of the central mesh 31, the third frame node 23, and the fourth frame node 24 is the third stress region 43; and the triangular region formed by the connection of the central mesh 31, the fourth frame node 24, and the first frame node 21 is the fourth stress region 44. The support units 2 in the first stress region 41 and the third stress region 43 of the support structure network are thinner than the support units 2 in the second stress region 42 and the fourth stress region 44.

[0065] In practical applications, the second side 12 and the fourth side 14 of the enclosed load-bearing member 1, which has a square cross-section, are respectively subjected to pressure. The second side 12 acts as the upper pressure-bearing side, and the fourth side 14 acts as the lower pressure-bearing side. Therefore, the outer sides of the second and fourth sides are under pressure, while the first and third sides are in a free state, unaffected by external forces. Thin-walled lattice porous structures are structural units used to fabricate various material structures; several thin-walled lattice structures constitute the corresponding material structure.

[0066] The optimized novel thin-walled lattice porous structure was simulated using finite element simulation software. The simulation examined the load conditions under which pressure was applied to the upper and lower sides of the structural frame, and the stress distribution of the lattice porous structure under these load conditions was obtained. A second optimization was performed based on the stress distribution analysis, resulting in a second optimized novel thin-walled lattice porous structure. According to the stress distribution of the optimized novel thin-walled lattice porous structure, it can be seen that the stress distribution of some thin walls in the first stress region 41 and the third stress region 43 is still relatively low. Therefore, according to the design requirements of the thin-walled lattice porous structure, the structural weight should be reduced as much as possible. Thus, based on the optimization objectives or structural strength requirements of the thin-walled lattice porous structure, the number of thin walls with low stress levels in the optimized novel thin-walled lattice porous structure should be reduced as much as possible to decrease the structural weight, resulting in the second optimized novel thin-walled lattice porous structure.

[0067] like Figure 4 As shown, when the structural strength requirement of the thin-walled lattice porous structure is high, one support unit 2 closest to the central mesh 31 in the first stress region 41 is removed, making the mesh area of ​​the mesh 3 closest to the central mesh 31 in the first stress region 41 approximately equal to that of the central mesh 31; one support unit 2 closest to the central mesh 31 in the first stress region 41 is removed to form a first mesh 32, the mesh area of ​​the first mesh 32 approximately equal to that of the central mesh 31. One support unit 2 closest to the central mesh 31 in the third stress region 43 is removed, making the mesh area of ​​the mesh 3 closest to the central mesh 31 in the third stress region 43 approximately equal to that of the central mesh 31; one support unit 2 closest to the central mesh 31 in the third stress region 43 is removed to form a second mesh 33, the mesh area of ​​the second mesh 33 approximately equal to that of the central mesh 31. The stress distribution obtained again from the finite element simulation software in step one shows that increasing the stress on the thin wall of the mesh closest to the central mesh 31 in the first stress region 41 and the third stress region 43 does not change the fact that the new thin-walled lattice porous structure still achieves the optimization goal after the second optimization, ensuring the structural strength of the lattice porous structure while reducing its weight. This further optimizes the new thin-walled lattice porous structure, bringing it to its optimal state.

[0068] like Figure 5 As shown, when the structural strength requirement of the thin-walled lattice porous structure is not high, the support units 2 in the first stress region 41 and the third stress region 43 whose stress levels are lower than the set stress threshold are removed, so that the mesh area in the first stress region 41 and the third stress region 43 is approximately equal to that in the central mesh 31. Specifically, the average stress value of all stress values ​​in each thin wall in the first stress region 41 and the third stress region 43 is calculated as the stress level of that thin wall. The stress level of each thin wall is compared with the set stress threshold. If the stress level of the thin wall is lower than the set stress threshold, the thin wall is removed; if the stress level of the thin wall is not lower than the set stress threshold, the thin wall is not removed. The set stress threshold is determined according to the structural strength requirement. The higher the required structural strength, the lower the stress threshold is set; the lower the required structural strength, the higher the stress threshold is set. This further optimizes the novel thin-walled lattice porous structure, achieving its optimal state.

[0069] Example 1

[0070] like Figure 6-7As shown, the pillar-type body-centered cubic lattice structure is a novel lightweight and high-strength energy-absorbing lattice material structure, which is optimized based on the traditional body-centered cubic lattice. This structure uses a cubic unit cell as the basic unit, and the eight corner points of the cube are connected to the central node through pillar elements to form a three-dimensional periodic truss structure with high geometric symmetry.

[0071] Step 1: Using ABAQUS finite element simulation software, obtain the stress distribution and force-displacement curves of the support-type body-centered cubic lattice structure under vertical external force before adjustment, such as... Figure 6 As shown;

[0072] Step 2: Use a Python script to divide each support of the lattice structure into multiple smaller structures, with each smaller structure having a spacing of approximately 0.1 mm. Then, use the Python script to perform statistical analysis on the stress level of each smaller support.

[0073] Step 3: Using a Python script, adjust the cross-sectional area of ​​each small support column based on the stress statistics. The specific operation is as follows: adjust the cross-sectional area of ​​the small support column with the lowest stress to 1 / 4 of the original cross-sectional area, and adjust the cross-sectional area of ​​the small support column with the highest stress to 4 times the original cross-sectional area.

[0074] Step 4: Using ABAQUS finite element simulation software, obtain the stress distribution and force-displacement curves of the adjusted column-type body-centered cubic lattice structure under vertical compressive force, such as... Figure 7 As shown;

[0075] pass Figure 6 and Figure 7 The comparison shows that the stress distribution of the pillar-type body-centered cubic lattice structure adjusted by this method is more uniform, the elastic modulus of the force-displacement curve is larger, and the stress peak value is higher. This method significantly improves the mechanical properties of the pillar-type body-centered cubic lattice structure.

[0076] Example 2

[0077] like Figure 8-9 As shown, the pillar-type random lattice structure is a porous structure composed of randomly distributed nodes and pillars connecting these nodes. The arrangement of its nodes and pillars does not follow a fixed periodic pattern but exhibits random distribution characteristics. It is usually prepared by additive manufacturing technology and has the characteristics of lightweight, high specific strength and controllable mechanical properties.

[0078] Step 1: Use ABAQUS finite element simulation software to obtain the stress distribution and force-displacement curves of the column-type random lattice structure under vertical pressure before adjustment, such as... Figure 8 As shown;

[0079] Step 2: Use a Python script to divide each support of the lattice porous structure into multiple smaller structures, with each smaller structure having a spacing of approximately 0.1 mm. Then, use a Python script to perform statistical analysis on the stress level of each smaller support.

[0080] Step 3: Using a Python script, adjust the cross-sectional area of ​​each small support column based on the stress statistics. The specific operation is as follows: adjust the cross-sectional area of ​​the small support column with the lowest stress to 1 / 4 of the original cross-sectional area, and adjust the cross-sectional area of ​​the small support column with the highest stress to 4 times the original cross-sectional area.

[0081] Step 4: Using ABAQUS finite element simulation software, obtain the stress distribution and force-displacement curves of the adjusted column-type body-centered cubic lattice structure under vertical compressive force, such as... Figure 9 As shown;

[0082] pass Figure 8 and Figure 9 The comparison shows that the stress distribution of the column-type random lattice structure adjusted by this method is more uniform, the elastic modulus of the force-displacement curve is larger, and the stress peak value is higher. This method significantly improves the mechanical properties of the column-type random lattice structure.

[0083] The above description is merely a preferred embodiment of the present invention. Those skilled in the art can make several modifications and optimizations based on the above disclosure without departing from the basic principles described above. These modifications and optimizations should be considered within the scope of protection as understood by the present invention.

Claims

1. A stress-driven method for local optimization of a dot-lattice porous structure, characterized by: Comprise the following steps: Step one, using finite element simulation software to simulate the stress of lattice porous structure under the corresponding load service condition, and obtain the stress distribution of lattice porous structure under the corresponding load service condition; Step two, the structure of the lattice porous structure is divided into several small size structures; Step three, using grid unit to obtain all the Von Mises stress value on each small size structure, and quantifying all the Von Mises stress value on each small size structure by statistical analysis method, and obtaining the stress level of each small size structure; Step four, according to the stress level of each small size structure and the set scaling rule, it is judged that each small size structure is enlarged or reduced in size, and the size of each small size structure is adjusted based on the type of lattice porous structure; Step five, it is judged whether the designed lattice porous structure reaches the set optimization target, if not, steps one to four are repeated for multiple iterations until the designed lattice porous structure reaches the optimization target; If so, the optimized lattice porous structure is obtained; Based on the above-mentioned local optimization method of lattice porous structure, a thin-walled lattice porous structure is designed, and then the size of each small size structure of the designed thin-walled lattice porous structure is adjusted by the above-mentioned local optimization method of lattice porous structure to realize local optimization and obtain a final thin-walled lattice porous structure; The final thin-walled lattice porous structure, the surrounding force member (1) with square frame cross section in the thin-walled lattice porous structure has a support structure network formed by a plurality of strip-shaped support units (2) connected to each other in the plane direction, the hole area of the mesh hole (3) near the central region tends to be larger, and the hole area of the mesh hole (3) near the four peripheral edges tends to be smaller; the support structure network is divided into first stress zone (41), second stress zone (42), third stress zone (43) and fourth stress zone (44), the support units (2) in the first stress zone (41) and the third stress zone (43) are thinner than the support units (2) in the second stress zone (42) and the fourth stress zone (44); and the support units (2) with low stress level in the first stress zone (41) and the third stress zone (43) are removed according to the optimization target of the thin-walled lattice porous structure.

2. The stress-driven lattice porous structure local optimization method according to claim 1, wherein: In the step two, the lattice porous structure includes a strut type lattice porous structure and a thin-walled lattice porous structure; the structure cutting processing is carried out on each strut of the plurality of struts in the strut type lattice porous structure to obtain a plurality of small size structures; each thin wall of the plurality of thin walls in the thin-walled lattice porous structure is equally spaced to obtain a plurality of small size structures.

3. The stress-driven lattice porous structure local optimization method according to claim 1, wherein: In the third step, any one small size structure contains a plurality of grid cells, and according to the position of each grid cell and the Von Mises stress value corresponding to each grid cell, all Von Mises stress values of the small size structure are obtained; the average value of all Von Mises stress values of the small size structure is calculated as the stress level, and the calculation process is as follows: In the formula, n represents the number of grid units on the small-size structure, S m The average value of all Von Mises stress values of the small-size structure.

4. The stress-driven lattice porous structure local optimization method of claim 1, wherein: In the fourth step, the set scaling rule includes a phased scaling rule and a linear scaling rule; the phased scaling rule is that the stress level of each small size structure is compared with the set stress threshold range, when the stress level of any one small size structure is higher than the highest stress threshold of the stress threshold range, then a set increasing size of the small size structure is increased; when the stress level of any one small size structure is lower than the lowest stress threshold of the stress threshold range, then a set decreasing size of the small size structure is decreased.

5. The stress-driven lattice porous structure local optimization method according to claim 4, wherein: The linear scaling rule linearly adjusts the size of the small-size structure according to the stress level of each small-size structure; the stress level is normalized to obtain S n The stress range is calculated according to S n The stress range and the set scaling factor linearly increase or decrease the size of the small-size structure, and the calculation process is as follows: where D i denotes the cross-sectional area of the small-size structure before the adjustment, D m denotes the cross-sectional area of the small-size structure after the adjustment, a denotes the scaling factor of the cross-sectional area of the small-size structure at the minimum stress level, b denotes the scaling factor of the cross-sectional area of the small-size structure at the maximum stress level, S n denotes the stress range normalized by the stress level, S n ∈ [0, 1].

6. The stress-driven lattice porous structure local optimization method of claim 1, wherein: A thin-walled lattice porous structure, the lattice porous stress structure includes a surrounding force member (1) with a square frame cross section; the surrounding force member (1) with a square frame cross section has a support structure network formed by a plurality of strip-shaped support units (2) connected to each other in the plane direction, the edges of the support structure network are integrally connected with the inner ring of the surrounding force member (1) with a square frame cross section; a group of mesh holes are formed on the support structure network, each mesh hole (3) on the group of mesh holes is surrounded by at least three support units (2), and the connection between any two support units (2) in the support structure network forms a force node (20).

7. The stress-driven lattice porous structure local optimization method according to claim 6, wherein: The central region of the group of mesh holes has a mesh hole (3) larger than other mesh holes (3), which is referred to as a central mesh hole (31); the closer to the central mesh hole (31) on the support structure network, the larger the hole area of the mesh hole (3) tends to be; the closer to the surrounding force member (1) with a square frame cross section on the support structure network, the smaller the hole area of the mesh hole (3) tends to be.

8. The stress-driven lattice porous structure local optimization method according to claim 7, wherein: The cross-section of the square frame surrounding force member (1) includes a first side (11), a second side (12), a third side (13) and a fourth side (14) in sequence in the clockwise direction; in the actual stress state, the second side (12) and the fourth side (14) are compressed on the outside, and the first side (11) and the third side (13) are in a free state without external force; the connection between the first side (11) and the second side (12) forms a first frame node (21), the connection between the second side (12) and the third side (13) forms a second frame node (22), the connection between the third side (13) and the fourth side (14) forms a third frame node (23), and the connection between the fourth side (14) and the first side (11) forms a fourth frame node (24); the triangular area formed by the central mesh (31), the first frame node (21) and the second frame node (22) is the first stress area (41), the triangular area formed by the central mesh (31), the second frame node (22) and the third frame node (23) is the second stress area (42), the triangular area formed by the central mesh (31), the third frame node (23) and the fourth frame node (24) is the third stress area (43), and the triangular area formed by the central mesh (31), the fourth frame node (24) and the first frame node (21) is the fourth stress area (44); the support unit (2) in the first stress area (41) and the third stress area (43) of the support structure network is thinner than the support unit (2) in the second stress area (42) and the fourth stress area (44).

9. The stress-driven lattice porous structure local optimization method of claim 8, wherein: Remove a support unit (2) closest to the central mesh (31) in the first stress area (41) to make the hole area of a mesh (3) closest to the central mesh (31) in the first stress area (41) tend to be equal to that of the central mesh (31); remove a support unit (2) closest to the central mesh (31) in the third stress area (43) to make the hole area of a mesh (3) closest to the central mesh (31) in the third stress area (43) tend to be equal to that of the central mesh (31).

10. The stress-driven lattice porous structure local optimization method of claim 8, wherein: Remove the support unit (2) in the first stress area (41) and the third stress area (43) whose stress level is lower than the set stress threshold to make the hole area of the mesh in the first stress area (41) and the third stress area (43) tend to be equal to that of the central mesh (31).

Images