Method for designing Kelvin tetrakaidecahedron shelling trepanning and multi-cell local cutting lattice structure based on SLM additive manufacturing technology
Through the design of Kelvin tetrahedral shell extraction holes and multicellular local cutting dot matrix structure, the shortcomings of Kelvin tetrahedral dot matrix structure in terms of compression strength and mechanical characterization are solved, and efficient mechanical performance improvement and energy absorption are achieved. It is suitable for aerospace, biomedicine and automobile manufacturing fields.
Patent Information
- Application Number
- CN202510816166.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-18
- Publication Date
- 2025-08-01
AI Technical Summary
The existing Kelvin tetrahedral lattice structure has shortcomings in compression strength and mechanical characterization, especially due to the low load-bearing yield strength caused by obturator cell confinement and single-cell design, and the lack of authenticity of the mechanical characterization of the multicellular lattice model.
By designing the Kelvin tetrahedron shell extraction hole and multicellular element locally cut dot matrix structure, the deformed tetrahedron is constructed using SLM additive manufacturing technology, adjusting the porosity and relative density, constructing three stacking structures of multicellular element, local cutting is performed to form a digital model of the dot matrix, and SLM additive preparation and subsequent heat treatment are carried out.
It significantly improves the compressive strength and energy absorption performance of the lattice structure, optimizes the mechanical response, provides more realistic mechanical characterization, and is suitable for fields such as aerospace, biomedicine and automobile manufacturing.
Smart Images
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Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of fabricating three-dimensional metal lattice structures by selectively melting metal powders with high-energy laser beams, and particularly relates to a method for designing a Kelvin tetrakaidecahedron shelled and perforated and multi-cell locally cut lattice structure based on SLM additive manufacturing technology. Background Art
[0002] Selective Laser Melting (SLM) is an advanced forming technology of selective laser melting. Its core mechanism is to use a high-energy density laser beam to selectively melt a metal powder layer according to a preset three-dimensional model path, and construct a three-dimensional metal part with a complex geometric shape by layer-by-layer stacking. This technology is known for its high forming accuracy, excellent mechanical properties and controllability of microstructure, and can meet the manufacturing requirements of complex structural parts, lightweight components and high-performance customized metal parts.
[0003] The lattice structure prepared based on SLM additive manufacturing technology has the advantages of light weight, high strength and excellent machinability. The unique structure form can provide innovative design ideas and methods for the needs of lightweight and efficient energy absorption, etc. The lattice structure with high efficiency performance can be widely applied to high-tech fields such as aerospace, biomedicine, and automobile manufacturing.
[0004] The lattice structure constructed based on the Kelvin tetrakaidecahedron exhibits excellent performance in terms of compressive strength, which is mainly attributed to its unique high-strength, lightweight geometric configuration and uniform stress distribution characteristics. In recent years, in the research on the design of the lattice structure based on the Kelvin tetrakaidecahedron, due to the limiting factor that the integrated formed metal powder cannot remain in the closed-cell body, most of the single cells are designed to increase the thickness with frame lines. Although this design belongs to a lightweight, hollow and perforated lattice structure, its bearing yield strength is extremely low; and the construction process from a single cell to a multi-cell lattice model is only a body-centered cubic structured periodic cell stacking, ignoring the cell vacancy problem on the outermost surface of the periodic structure, resulting in a decrease in the authenticity of the mechanical characterization of the multi-cell body under the periodic structure. Moreover, the geometric characteristics of the load-bearing contact cross-section of these lattice structures constructed with the Kelvin tetrakaidecahedron are all squares; the multi-cell lattice structures with hexagonal faces and edges as the contact cross-sections have not been designed and studied, resulting in a single load-bearing angle of the Kelvin tetrakaidecahedron lattice structure and the need for structural design optimization.
[0005] Therefore, the lattice structure design method of Kelvin tetrakaidecahedron shelled and perforated and multi-cell locally cut based on SLM additive manufacturing technology has important theoretical and application research values. Summary of the Invention
[0006] To solve the problems existing in the prior art, the present invention provides a method for designing a Kelvin tetrakaidecahedron shelling and opening holes and a multi-cell local cutting lattice structure based on the SLM additive manufacturing technology. By shelling and opening holes, a deformed tetrakaidecahedron is constructed. According to three geometric features, multi-cells under different stacking structures are constructed. After determining the multi-cell multiples, a lattice structure multi-cell model under three ideal topologies is constructed by local cutting, and samples are additively manufactured by the SLM technology for quasi-static compression mechanical tests to characterize the mechanical anisotropy of the periodic deformed tetrakaidecahedron.
[0007] To achieve the above object, the present invention adopts the following technical solutions:
[0008] A method for designing a Kelvin tetrakaidecahedron shelling and opening holes and a multi-cell local cutting lattice structure based on the SLM additive manufacturing technology, comprising the following steps:
[0009] Step 1. Taking the tetrakaidecahedron as the single-cell prototype and setting the specifications of the regular tetrakaidecahedron;
[0010] Step 2. Defining the scaling origin of the single cell, scaling the single cell, adjusting the surface spacing between the outer surfaces of the model before and after scaling, and controlling the target shell thickness;
[0011] Step 3. Subtracting from the tetrakaidecahedron before the original scaling to construct a hollow single cell with the target shell thickness;
[0012] Step 4. Opening circular through holes at the center of each square face of the hollow single cell to obtain the target cell body;
[0013] Step 5. After summarizing the target single cells according to geometric features, stacking them into different structural units to construct corresponding multi-cells;
[0014] Step 6. Designing a local cutting path, cutting the periodic multi-cell stacking structure according to the multi-cell contour and multiples to construct a lattice digital model;
[0015] Step 7. Based on the lattice digital model, adopting SLM additive manufacturing to realize model preparation.
[0016] In Step 1, the tetrakaidecahedron is a Kelvin tetrakaidecahedron; the distance between the centers of the six square faces of the tetrakaidecahedron is twice the length of the diagonal of the square; within the SLM additive manufacturing accuracy range, the length of the diagonal of the square is greater than or equal to 5 mm;
[0017] In Step 2, the scaling process is that each geometric feature in the Kelvin tetrakaidecahedron single cell is scaled proportionally with the Gizmo center as the origin; the scaling ratio is determined by the surface spacing between the outer surfaces of the tetrakaidecahedron before and after the original scaling, and the size of the surface spacing is the thickness of the hole wall of the target model after subtraction;
[0018] In step 3, the thickness of the hollow single-cell shell is less than half of the distance between the symmetry planes of the single-cell prototype.
[0019] In step 4, the diameter of the circular through-hole is greater than or equal to 2 mm.
[0020] In step 5, with the cell cross-section where the geometric characteristics of the target tetrakaidecahedron are located perpendicular to the compression direction as the reference, using the ideal topological inductive stacking structure, the most reasonable cell structure unit - the multi-cell element is constructed.
[0021] During the stacking process, each geometric characteristic of the single cell is always perpendicular to the compression direction as the reference, and using the ideal topological stacking, the multi-cell element with the corresponding special stacking structure is constructed.
[0022] The stacking structure is one of the body-centered cubic structure, the face-centered cubic structure or the close-packed hexagonal structure.
[0023] In step 6, the cutting process is as follows: According to the target model specifications, under an infinitely multiplied and periodically ideal arrangement, according to the required multiple of the multi-cell element, along the outermost surface contour of the multi-cell element, the multi-cell stacking tissue exceeding the contour line is cut, and a local sample model is extracted, which is the lattice digital model of the target model.
[0024] In step 7, the SLM additive manufacturing process flow is as follows: Start the additive manufacturing printer, set the scanning axis contour power to 290 W, the filling power to 425 W, the support power to 340 W, the contour speed to 500 mm / s, the filling speed to 1600 mm / s, and the support speed to 2000 mm / s; the filling spacing is 0.16 mm, the rotation angle is set to 67°, and the metal powder layer thickness is selected to be 30 μm; after the metal sample is prepared, it is separated from the bottom plate by wire cutting, and the support frame, etc. are removed; then the sample is heated to 500 °C in a vacuum tube furnace, held for 3 hours, air-cooled and then water-quenched; then it is held at 230 °C for 2 hours; after taking it out, it is air-cooled and dried in a drying oven for 1 h; finally, the surface of the metal sample is sandblasted with white corundum artificial abrasive using a 6050E type sandblaster for anti-corrosion and antioxidant treatment.
[0025] During the SLM additive manufacturing process, the metal powder is selected according to the target model.
[0026] The innovation and practicality gain effect of the present invention lies in:
[0027] 1. After scaling the single cell through the interactive Gizmo tool in Shapr3D, during the isometric scaling process, as long as the distance between the outer surfaces of the two models is controlled, the thickness of the cell wall can be adjusted. The change in thickness affects the porosity of the single cell, and then the relative density can be adjusted in the multi-cell lattice structure, realizing that the scaled shelling of the deformed tetrakaidecahedron single cell can maintain structural stability and light weight while also facilitating the adjustment of the single cell porosity and the relative density of the multi-cell lattice structure.
[0028] 2. Open a circular micropore at the center of the square face of each deformed tetrakaidecahedron, aiming to extract the metal powder in the closed pores on the basis of restoring the strength of the closed pore structure, and prevent the expansion, melting and cooling caking of the residual powder during the subsequent heat treatment strengthening process of the metal sample;
[0029] 3. Through the three geometric features of the tetrakaidecahedron, construct multi-cells under three stacking structures, providing a new lattice structure design idea for studying the mechanical anisotropy such as compressive energy absorption of the deformed tetrakaidecahedron; the local cutting idea makes up for the vacancy defects of the outer surface cells under simple stacking, solves the problem of the decrease in the authenticity of the mechanical characterization of the lattice structure, and makes the mechanical characterization of the periodic structure more sufficient. BRIEF DESCRIPTION OF THE DRAWINGS
[0030] Figure 1 It is a schematic diagram of the design of the scaled shelling and hole-opening deformed tetrakaidecahedron model provided by the embodiment of the present invention; (a) are the parameter regulations of the front view, top view and left view of the deformed tetrakaidecahedron; (b) is the auxiliary view after the deformed tetrakaidecahedron is shelled and hole-opened;
[0031] Figure 2 It is a schematic diagram of the design of the deformed tetrakaidecahedron BCC multi-cell provided by the embodiment of the present invention; (a) are the front view, top view and left view of the BCC multi-cell; (b) is the auxiliary view of the BCC multi-cell;
[0032] Figure 3 It is a schematic diagram of the design of the deformed tetrakaidecahedron HCP multi-cell provided by the embodiment of the present invention; (a) is the front view of the HCP multi-cell; (b) is the left view of the HCP multi-cell; (c) is the top view of the HCP multi-cell; (d) is the auxiliary view of the HCP multi-cell;
[0033] Figure 4 It is a schematic diagram of the design of the deformed tetrakaidecahedron FCC multi-cell provided by the embodiment of the present invention; (a) is the left view of the FCC multi-cell; (b) are the front view and top view of the FCC multi-cell; (c) is the auxiliary view of the FCC multi-cell;
[0034] Figure 5 It is a schematic diagram of the design of the lattice structure model obtained by local cutting of the BCC multi-cell provided by the embodiment of the present invention; (a) are the front view, top view and left view of the model; (b) is the auxiliary view of the model;
[0035] Figure 6 It is a schematic diagram of the design of the lattice structure model obtained by local cutting of the HCP multi-cell provided by the embodiment of the present invention; (a) is the front view of the model; (b) is the top view of the model; (c) is the left view of the model; (d) is the auxiliary view of the model;
[0036] Figure 7Schematic diagram of the lattice structure model designed by locally cutting the FCC polyhedron in the embodiments of the present invention; (a) is the left view of the model; (b) is the front view and top view of the model; (c) is the auxiliary view of the model;
[0037] Figure 8 Schematic diagrams of three lattice structure metal samples obtained by locally cutting polyhedrons in the embodiments of the present invention; (a) is the sample obtained by locally cutting the BCC polyhedron; (b) is the sample obtained by locally cutting the HCP polyhedron; (c) is the sample obtained by locally cutting the FCC polyhedron;
[0038] Figure 9 Three lattice structure metal samples obtained by locally cutting polyhedrons in the embodiments of the present invention at a strain rate of 1200s -1 Process diagrams of quasi-static compression tests; (a) is the test process of the sample obtained by locally cutting the BCC polyhedron; (b) is the test process of the sample obtained by locally cutting the HCP polyhedron; (c) is the test process of the sample obtained by locally cutting the FCC polyhedron;
[0039] Figure 10 The lattice structure metal sample obtained by locally cutting the FCC polyhedron in the embodiments of the present invention uses a square geometric feature cross-section as the loaded surface at a strain rate of 1200s -1 Process diagrams of quasi-static compression tests;
[0040] Figure 11 Quasi-static compression stress-strain diagrams of three lattice structure metal samples in the embodiments of the present invention;
[0041] Figure 12 Quasi-static compression energy absorption-strain diagrams of three lattice structure metal samples in the embodiments of the present invention;
[0042] Figure 13 Quasi-static compression energy absorption efficiency-strain diagrams of three lattice structure metal samples in the embodiments of the present invention;
[0043] Figure 14 Quasi-static compression specific energy absorption comparison diagrams of three lattice structure metal samples in the embodiments of the present invention;
[0044] Figure 15 The lattice structure metal sample obtained by locally cutting the FCC polyhedron in the embodiments of the present invention uses a square surface geometric feature as the loaded surface at a strain rate of 1200s -1 Process diagrams of quasi-static compression load-displacement; Detailed implementation manners
[0045] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.
[0046] In the method for designing a Kelvin tetrakaidecahedron shell-opening and multi-cell local cutting lattice structure based on the SLM additive manufacturing technology of the present invention, during the SLM additive manufacturing process, the metal powder is selected according to the target model.
[0047] The following describes the specific implementation of the present invention in detail with reference to specific embodiments.
[0048] Examples 1 to 3
[0049] Examples 1 to 3 sequentially prepare three lattice structure multi-cell metal samples of body-centered cubic (BCC), hexagonal close-packed (HCP), and face-centered cubic (FCC), including the following steps:
[0050] Step 1. As Figure 1 shown, first establish six square faces with a diagonal length of 5 mm, rotate them by 45°, occupy the six face centers of the cell body, set the distance between the symmetric square face centers to 10 mm, then connect the diagonals of adjacent faces, and wrap and connect the empty faces with 8 hexagons with a side length of about 3.5 mm to construct the basic constitutive model, the Kelvin tetrakaidecahedron unit cell.
[0051] Step 2. Use the interactive Gizmo tool in Shapr3D to define the center scaling origin, uniformly scale it proportionally to obtain the second model, and control the surface distance between the outermost surfaces of the original model and the second model to be 0.8 mm;
[0052] Step 3. Subtract the two models to construct a hollow unit cell with a uniform cell wall thickness of 0.8 mm.
[0053] Step 4. Open a circular through-hole with a diameter of 2 mm at the center of the six square faces of the hollow unit cell.
[0054] Step 5. As Figures 2 - 4As shown in the figure, it is composed of three geometric features of the tetrakaidecahedron: square faces, hexagonal faces, and edges. When the cell tissue under a large-scale ideal topological structure is subjected to quasi-static compression, in order to ensure that the cross-section of the cell tissue where the geometric features are located serves as the directly loaded contact surface and always maintains a perpendicular angle to the compression direction. First, three types of polycells are constructed: First, taking a certain geometric feature of the single cell perpendicular to the compression direction as the benchmark, using ideal topological stacking, a polycell with a corresponding special stacking structure is constructed to determine the cell multiple of the model. By deforming the square faces, hexagonal faces, and edges among the three geometric features of the tetrakaidecahedron, polycells under three stacking structures of body-centered cubic (BCC), hexagonal close-packed (HCP), and face-centered cubic (FCC) are topologically constructed respectively.
[0055] Step 6. As Figures 5 - 7 shown in the figure, determine the polycell multiple of the required lattice structure model according to the polycells under the three stacking structures, and then form three local cutting logics: Cut the polycell tissue under an infinitely multiplied body and periodic ideal arrangement, extract the local sample model, and obtain three digital polycell models of lattice structures.
[0056] Step 7. Model export: Through computer-aided design software, convert the three constructed digital polycell models into STL format and export the corresponding digital model files for subsequent printing preparation. Printing preparation: Select AlSi 10 Mg component aluminum alloy metal powder raw material, input the digital model file into the printer control system after slicing it with slicing software. SLM additive manufacturing: In the starting metal laser selective melting process parameters, set the scanning axis profile power to 290W, the filling power to 425W, the support power to 340W, the profile speed to 500mm / s, the filling speed to 1600mm / s, the support speed to 2000mm / s; the filling spacing is 0.16mm, the rotation angle is set to 67°, and the metal powder layer thickness is selected as 30μm; According to the sliced digital model file, the laser irradiates the first layer of powder in the forming cavity, melts and sinters the first layer of slices, and then the powder spreading system spreads the second layer of powder on the working platform, making the second layer of powder cover and be exposed to the laser light source, and then performs laser irradiation for melting and sintering again. Repeat this process until the entire model is printed. After the metal sample is prepared, separate it from the bottom plate by wire cutting and remove the support frame, etc. As Figure 8 shown in the figure, after the sample is formed in the forming cavity, the subsequent heat treatment process flow is: Heat it to 500°C in a vacuum tube furnace, hold for 3 hours, cool in oil and then quench in water; then continue to hold at 230°C for 2 hours for age hardening; take it out and air cool and dry it in a drying oven for 1h; then use a 6050E type sandblaster to perform sandblasting anti-corrosion and antioxidant treatment on the surface of the metal sample with white corundum artificial abrasive; obtain three polycell metal samples of lattice structures.
[0057] As Figures 9 - 10As shown, quasi-static compression tests were performed on the prepared different metal samples, and each sample was tested repeatedly once.
[0058] As Figures 11 - 14 shown, the method provided by the embodiment of the present invention for designing a Kelvin tetrakaidecahedron shell-opening and multi-cell local cutting lattice structure based on the SLM additive manufacturing technology has strong repeatability and high controllability; the shell-opening design plays an important role in the lightweight of the lattice structure, and at the same time makes full use of the advantages of the closed-cell structure in energy absorption. Compared with the traditional frame wire thickening stacking and opening structure, this design significantly improves the compressive strength, and its yield bearing strength can reach up to 310 MPa at most. The construction of three types of multi-cells provides a new lattice structure design idea for studying the mechanical anisotropy such as the compressive energy absorption of the deformed tetrakaidecahedron. The lattice structure models obtained by local cutting of the three types of multi-cells have significant differences in the bearing strength and energy absorption efficiency at different deformation stages, and each has its own advantages. This proves that the multi-cell tissue constructed by the deformed tetrakaidecahedron under the ideal topological structure has mechanical anisotropy and has diversity in the actual application direction. In addition, through the lattice construction strategy of local cutting, the vacancy defects of the outer surface cells are effectively filled, making the mechanical characterization of the periodic cell tissue more real and comprehensive, so as to more accurately reflect the mechanical properties of the material. This design not only optimizes the mechanical response of the structure, but also provides important theoretical and technical support for the engineering application of the lattice structure.
[0059] As Figure 15 shown, when the lattice structure metal sample obtained by local cutting of the FCC multi-cell provided by the embodiment of the present invention is subjected to a quasi-static compression test with a square geometric feature as the loaded surface (FCC_B), the curve change trend and the failure collapse form are basically consistent with the test results of the lattice model constructed by the BCC multi-cell; and by observing the two stacking structure models, it can be seen that when the FCC multi-cell model takes the square geometric feature surface as the upper and lower surfaces, after rotating 45° horizontally, the stacking and inlaying rules of the deformed tetrakahedron are the same as those of the BCC multi-cell model. Therefore, combining the test results proves that it is representative and unified to determine the quasi-static compression angle and performance characterization of the periodic cell tissue under the ideal topology through the geometric features of the section where the deformed tetrakahedron is located.
[0060] The above embodiments are only used to illustrate the technical concept and characteristics of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.
Claims
1. A method for designing a Kelvin tetrakaidecahedron shelled and perforated and multi-cell locally cut lattice structure based on SLM additive manufacturing technology, characterized in that, The following steps are involved: Step 1. Take the tetradecahedron as the unit cell prototype and set the specifications of the tetradecahedron; Step 2. Define the unit cell scaling origin, scale the unit cell, adjust the surface spacing of the model before and after scaling, and control the target shell thickness; Step 3. Subtract the original tetradecahedron before scaling to construct a hollow unit cell of target shell thickness; Step 4. Open circular holes at the center of each square face of the hollow unit cell to obtain the target cell body; Step 5. After summarizing the target unit cells according to their geometric features, they are stacked into different structural units to construct corresponding polycells; Step 6. Design a local cutting path, cut the periodic multicellular stacking tissue according to the multicellular outline and multiples, and construct a lattice digital model; Step 7. Based on the lattice digital model, SLM additive manufacturing is used to prepare the model.
2. A method for designing a Kelvin tetrakaidecahedron shelled and perforated and multi-cell locally cut lattice structure based on the SLM additive manufacturing technology according to claim 1, characterized in that, In step 1, the tetradecahedron is a Kelvin tetradecahedron; wherein the distance between the centers of the six square faces of the tetradecahedron is twice the length of the diagonal of the square; Within the accuracy range of SLM additive manufacturing, the diagonal length of the square is greater than or equal to 5 mm.
3. The method for designing Kelvin tetradecahedron shell openings and multi-cell local cutting lattice structures based on SLM additive manufacturing technology according to claim 1, characterized in that: In step 2, the scaling process is to scale each geometric feature in the Kelvin tetradecahedron unit cell with the center of the Gizmo as the origin in equal proportion; The scaling ratio is determined by the surface spacing of the outer surfaces of the tetradecahedron before and after scaling. The surface spacing is the hole wall thickness of the target model after subtraction.
4. The method for designing a Kelvin tetradecahedron shell opening and a multi-cell local cutting lattice structure based on SLM additive manufacturing technology according to claim 1, characterized in that: In step 3, the thickness of the hollow unit cell shell is less than half of the inter-plane spacing of the symmetry surfaces of the unit cell prototype.
5. A method for designing a Kelvin tetrakaidecahedron shell-opening and multi-cell local cutting lattice structure based on SLM additive manufacturing technology according to claim 1, characterized in that In step 4, the diameter of the circular through hole is greater than or equal to 2 mm.
6. A method for designing a Kelvin tetrakaidecahedron shelled and perforated and multi-cell locally cut lattice structure based on the SLM additive manufacturing technology according to claim 1, characterized in that, In step 5, the cell section where the geometric features of the target tetradecahedron are located is perpendicular to the compression direction as a reference, and the ideal topology is used to summarize the stacking structure to construct the most reasonable cell structure unit - the polycell.
7. A method for designing a Kelvin tetrakaidecahedron shell-opening and multi-cell local cutting lattice structure based on the SLM additive manufacturing technology according to claim 6, characterized in that During the stacking process, each geometric feature of the unit cell is always perpendicular to the compression direction as a reference, and ideal topological stacking is used to construct a multi-cell with a corresponding special stacking structure.
8. A method for designing a Kelvin tetrakaidecahedron shelled and perforated and multi-cell locally cut lattice structure based on SLM additive manufacturing technology according to claim 6 or 7, characterized in that The stacking structure is one of a body-centered cubic structure, a face-centered cubic structure or a close-packed hexagonal structure.
9. The method for designing Kelvin tetradecahedron shell openings and multi-cell local cutting lattice structures based on SLM additive manufacturing technology according to claim 1, characterized in that: In step 6, the cutting process is: according to the specifications of the target model, under an infinite multiple, periodic ideal arrangement, according to the required polyhedral multiples, along the outermost surface contour of the polyhedral element, the polyhedral stacking tissue that exceeds the contour line is cut, and a local sample model is extracted, which is the lattice digital model of the target model.