A cross-substrate topological dot lattice metamaterial structure

Abstract

The application discloses a kind of cross substrate topological dot matrix metamaterial structures, it is related to bearing and energy-absorbing material technical field, to solve the technical defects that existing mechanical metamaterial high stress level and stress stability is difficult to take into account, deformation mode is uncontrollable.The structure is prepared by "cross plate rotation forming-vertical direction enhancement-center cutting" unit cell, then the main body of metamaterial is formed by periodic array;Using the synergistic cooperation of bending dominant structure and tensile dominant structure, a new energy-absorbing mechanism is formed, which realizes the characteristics of no initial peak stress, high stress level and uniform performance in all directions without additional space occupation, and the deformation energy-absorbing mode is stable and controllable, avoiding the random buckling and overturning of traditional structure.The application can be widely used in aerospace, transportation and other fields, and provides an ideal material solution for high-demand bearing and energy-absorbing scenarios.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bearing and energy absorption materials, and in particular to a cross-substrate topological lattice metamaterial structure. BACKGROUND

[0002] With the vigorous development of the field of vehicles (airplanes, high-speed trains, cars, etc.), the ultimate speed has been greatly improved, and the performance of new bearing and energy absorption materials and structures has been strictly required - must have multi-directional uniform plasticity, stable high stress level, no initial peak stress and high energy absorption efficiency.

[0003] Metamaterials, as artificially designed periodic microstructure materials, their overall performance can be customized by adjusting the matrix material parameters and geometric structure parameters, and have great application potential in the field of plastic large deformation bearing and energy absorption, and become an important branch of multi-cellular materials. However, the experimental research and mechanism exploration in this field are still in the initial stage, and the existing mechanical metamaterials are limited by material performance and geometric configuration, and have some core defects that are difficult to overcome:

[0004] Bending-based metamaterials: although they have smooth stress distribution and good stress stability, the overall deformation characteristics result in low stress level, which cannot meet the demand of high bearing scene;

[0005] Stretching-based metamaterials: the average stress is relatively high, but the initial peak stress is significantly affected by local deformation, and the stress fluctuation amplitude is large and the stability is poor;

[0006] Traditional plate lattice metamaterials: the performance is seriously dependent on the design of unit cell structure, and the mechanical properties of each component material cannot be fully utilized, and the energy absorption efficiency is limited;

[0007] Traditional honeycomb energy absorption device: the out-of-plane deformation mode is extremely unstable, and under the action of load, random buckling, overturning and other uncontrollable phenomena easily occur, which seriously affects the use reliability.

[0008] In summary, a cross-substrate topological lattice metamaterial structure is urgently needed. SUMMARY

[0009] The purpose of the present application is to provide a cross-substrate topological lattice metamaterial structure to solve the problem that the performance of existing materials cannot meet the demand.

[0010] The technical solution of the present application to solve the above technical problems is as follows:

[0011] A cross-substrate topological lattice metamaterial structure, comprising a metamaterial main body formed by a periodic array of unit cells, the unit cells being composed of a bending-dominant structure and a stretching-dominant structure in cooperation; the preparation process of the unit cells comprises the following steps:

[0012] Step 1: The cross-plate structure is rotated to form a rotating foundation structure;

[0013] Step 2: Add a reinforcing plate structure in the vertical direction of the rotating base structure to obtain a combined reinforcing structure;

[0014] Step 3: Perform a central excision on the combined reinforcement structure to obtain the single cell.

[0015] In a further embodiment, the cross plate structure is a pair of cross inclined plates with a preset angle, the preset angle being 30°~150°.

[0016] In a further embodiment, the rotation operation in step one involves rotating 1 to 5 times within a 360° range, preferably three times, with each rotation angle being equal.

[0017] In a further embodiment, the reinforcing plate structure is a cross-shaped plate, and the thickness of the cross-shaped plate is the same as or adapted to the thickness of the cross-shaped plate structure.

[0018] In a further embodiment, the central cutting process in step three involves cutting off the cube or cuboid region at the center of the combined reinforcement structure, with the side length / edge length of the cut region being 1 / 3 to 2 / 3 of the overall size of the combined reinforcement structure.

[0019] In a further embodiment, the periodic array is a single cell arranged in a three-dimensional space (x, y, z directions), with the number of arrays ranging from 2×2×2 to 5×5×5, preferably a 3×3×3 array.

[0020] In a further embodiment, the axial stiffness of the metamaterial structure is increased by more than 30% compared to the traditional hexagonal honeycomb energy absorption device, and the average value of the force-displacement curve is increased by more than 20%.

[0021] In a further embodiment, the metamaterial structure exhibits consistent stress stability in the x, y, and z directions under quasi-static compression conditions, with no obvious initial peak stress and stress fluctuation amplitude ≤10%.

[0022] In a further embodiment, the bending-dominant structure and the tension-dominant structure dissipate energy through synergistic action, forming a "bending-tension coupling" energy absorption mechanism, thereby achieving a balance between a stable force-displacement curve and a high stress level.

[0023] In a further embodiment, the matrix material of the metamaterial structure is a metallic material, a composite material, or a polymer material. The metallic material includes aluminum alloys and titanium alloys, and the composite material includes carbon fiber reinforced composite materials.

[0024] The present invention has the following beneficial effects:

[0025] Energy absorption mechanism innovation: through the synergistic cooperation of bending dominant structure and tensile dominant structure, a "bending-tensile coupling" energy absorption mechanism is formed, which not only maintains the advantage of smooth force-displacement curve of traditional honeycomb structure, but also greatly improves the stress level, solving the inherent contradiction between the two;

[0026] Performance comprehensive improvement: the axial stiffness is improved by more than 30% compared with the traditional hexagonal honeycomb structure, the average value of force-displacement curve is improved by more than 20%, stable bearing capacity can be maintained in the range of small strain to large strain, and the energy absorption efficiency is significantly improved;

[0027] Deformation mode is controllable: the randomness of out-of-plane deformation of traditional structure is eliminated, the deformation path is constrained through structure topology design, and uncontrollable phenomena such as random buckling and overturning are avoided, the deformation process is stable and reliable, and the predictability is strong;

[0028] Uniform performance in all directions: on the premise of not occupying additional space, through symmetrization design and "bending-tensile" synergistic mechanism, the performance consistency in x, y and z directions is realized, and the use demand of multi-directional uniform plasticity is met;

[0029] Wide application range: suitable for different base materials, the unit cell size, array number and material type can be adjusted according to the scene demand, and it is suitable for multiple fields such as aerospace and transportation, and has strong practicality. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 : Schematic diagram of preparation process of unit cell of the application;

[0031] Figure 2 : Three-dimensional schematic diagram of 3x3x3 lattice metamaterial structure of the application;

[0032] Figure 3 : Parallel view of x, y and z directions of the metamaterial structure of the application (upper half) and schematic diagram of shape after quasi-static compression deformation (lower half);

[0033] Figure 4 : Parallel view of x, y and z directions of traditional hexagonal honeycomb structure (upper half) and schematic diagram of shape after quasi-static compression deformation (lower half);

[0034] Figure 5 : Quasi-static compression force-displacement comparison curve of the metamaterial structure of the application and the traditional hexagonal honeycomb structure in x, y and z directions: DETAILED DESCRIPTION

[0035] The principles and characteristics of the application are described below in conjunction with the drawings, and the examples are only used to explain the application and not to limit the scope of the application.

[0036] 1. Design and selection of example parameters

[0037] This embodiment selects a parameter combination with strong adaptability and mature technology based on the application requirements of medium-sized buffer structures in the aerospace field, and the specific design is as follows:

[0038] Base material: 6061 aluminum alloy is selected, which has a density of 2.7 g / cm³ and a yield strength of 270 MPa, and has the advantages of lightweight, high strength, and good plastic processing performance. It is widely used in the fields of aerospace and transportation, and has a significant cost-effective advantage. Its mechanical properties are highly compatible with the "bending-tension coupling" energy absorption mechanism of the present application, and can fully realize the synergistic effect of structure and material.

[0039] Crossed inclined plate parameters: thickness 1 mm, length 10 mm, and included angle 90°. The 90° included angle is selected based on the requirement of structural symmetry, which can ensure that the mechanical properties in x, y, and z directions are uniform, and can avoid the phenomenon of partial load during stress process. The ratio of 1 mm thickness to 10 mm length is verified by previous simulation to achieve an optimal balance between lightweight and load-bearing strength, so that neither local stress concentration caused by too thin thickness nor increased structural redundancy caused by too thick thickness occurs.

[0040] Rotary operation: rotate three times within a 360° range, each time by 120°. This design forms a spatially symmetric rotary base structure by three equal rotations, which can evenly distribute the stress transmission path of the structure in three-dimensional space. Compared with 1, 2, or 4 rotations, 3 equal rotations can maximize the overall structure and stability, and avoid weak mechanical properties in certain directions.

[0041] Reinforcing plate structure: cross-shaped plate thickness 1 mm, length 10 mm, and perpendicular to the rotary base structure. The thickness of the cross-shaped plate is consistent with that of the crossed inclined plate, which can ensure the fit during assembly and avoid stress concentration caused by thickness difference. The perpendicular assembly method can enhance the vertical load capacity of the structure without occupying horizontal space, and fill the rigidity gap of the rotary base structure in the vertical direction.

[0042] Center cut: cut the cube region at the center of the combined reinforcing structure, with a side length of 5 mm. This size accounts for 1 / 2 of the overall size of the combined reinforcing structure (10 mm), which is within the optimal design range of 1 / 3~2 / 3. Cutting too little will cause uneven stress distribution within the structure, and cutting too much will weaken the structural strength. The cutting ratio of 1 / 2 can achieve the dual goals of "stress uniformization" and "strength preservation", providing a spatial structure basis for the realization of the energy absorption mechanism.

[0043] Cell and array parameters: the cell size is designed to be 10 mm x 10 mm x 10 mm, which facilitates industrial mass production and assembly; the array mode adopts 3 x 3 x 3, forming a metamaterial structure with an overall size of 30 mm x 30 mm x 30 mm, which not only meets the use requirements of small and medium-sized buffer structures, but also amplifies the energy absorption advantage of the structure through the synergistic effect between cells. Compared with 2 x 2 x 2 array, the mechanical properties of 3 x 3 x 3 array are more stable, and compared with 4 x 4 x 4 and above array, the structure weight and manufacturing cost can be better controlled.

[0044] 2. Preparation process and quality control

[0045] This embodiment adopts a three-stage preparation process of "precision machining-precise assembly-fine detection" to ensure the consistency of structure size precision and mechanical properties. The specific process is as follows:

[0046] Forming machining: a 300W fiber laser cutting machine is selected to process the cross inclined plate and the cross plate. The cutting accuracy of this equipment can reach ±0.03mm, which is better than the preset accuracy requirement of ±0.05mm. The cutting parameters are set as follows: cutting speed 500mm / min, focal point position 0.2mm, auxiliary gas (oxygen) pressure 0.3MPa. Through this parameter combination, the burrs and heat affected zone of the plate cutting edge can be effectively reduced, ensuring the consistency of plate size and surface flatness, and laying a foundation for subsequent assembly. After cutting, the thickness, length and included angle of each plate are detected one by one using a digital caliper, and unqualified products (error exceeding ±0.05mm) are removed.

[0047] Assembly and fixation: first, a special assembly tool is built, and the cross inclined plate is positioned and fixed at an included angle of 90°. The tool ensures that the coaxiality error of the intersection center of the two inclined plates is ≤0.1mm; then, rotation positioning is performed, taking the intersection center as the axis, and fixing it through a positioning pin after each rotation of 120°, to ensure that the angle deviation of the three rotations is ≤1°. Then, argon arc welding is used for fixation, with the welding parameters being: welding current 80~100A, argon flow rate 10~15L / min, and welding speed 3~5mm / s. After welding, the penetration detection method is used to check the welding cracks, to ensure that the rotating foundation structure has no connection defects. Next, the cross plate is assembled in the vertical direction, and the tool positioning is used to ensure that the perpendicularity error of the cross plate and the rotating foundation structure is ≤0.1mm. The same argon arc welding parameters are used to complete the welding, forming a combined reinforced structure.

[0048] Center cutting: Select vertical numerical control milling machine for center cutting processing, equipped with hard alloy end mill (diameter 4 mm). Before processing, the combined reinforcement structure is positioned by a fixture to ensure that the center of the cutting area coincides with the geometric center of the combined reinforcement structure, and the coaxiality error is ≤0.1 mm; the milling parameters are set as follows: spindle speed 3000 r / min, feed speed 100 mm / min, cutting depth 0.5 mm / time, and layered milling is used to avoid structural deformation caused by one-time cutting. After cutting, the edge length and perpendicularity of the cutting area are detected by a three-coordinate measuring instrument to ensure that the design requirements of 5 mm x 5 mm x 5 mm are met.

[0049] Array forming: A 3x3x3 array assembly tool is made, which has 27 positioning grooves, each of which matches the size of a unit cell, and the spacing error between adjacent positioning grooves is ≤0.05 mm. The 27 qualified unit cells are placed one by one into the positioning grooves, the fit between the unit cells is adjusted to ensure that the connecting surfaces of adjacent unit cells have no gaps; then argon arc welding is used to weld and fix the connecting points between the unit cells, and symmetric welding sequence is used to avoid overall structural deformation caused by welding stress. After welding, the overall size and flatness of the metamaterial structure are detected by a laser range finder to ensure that the overall size error of 30 mm x 30 mm x 30 mm is ≤0.2 mm, and the surface flatness error is ≤0.1 mm.

[0050] Surface treatment: First, use mechanical deburring process to remove burrs and welding slag at each connection site by using a grinder (2000 r / min), and then use sandpaper (800 mesh) for fine polishing to ensure that the structure surface is free of sharp protrusions; then perform pickling treatment by immersing the structure in a 5% hydrochloric acid solution for 5 minutes to remove the oxide skin generated during welding, and then rinse with clean water and dry; finally, spray anti-rust primer (epoxy zinc-rich primer) with a film thickness of 20-30 μm, and bake at 60°C for 2 hours after spraying to ensure the adhesion and corrosion resistance of the anti-rust coating, prolonging the service life of the structure.

[0051] 3. Performance test and result analysis

[0052] To fully verify the technical advantages of the present application, a traditional hexagonal honeycomb structure with the same material and overall size (30 mm x 30 mm x 30 mm) is selected as a comparative sample, and a quasi-static compression performance test is carried out under standard environment, and the specific test scheme and results are as follows:

[0053] Test conditions: an electronic universal testing machine with a 50kN range, test accuracy of 0.5 level, in line with the requirements of GB / T1447-2005 "Fiber Reinforced Plastic Tensile Property Test Method"; the test environment is room temperature 23±2℃, humidity 50±5%; the compression rate is set to 2mm / min, which is highly consistent with the low-speed impact scenarios commonly seen in actual engineering (such as landing cushioning, collision cushioning); each group of tests sets 3 parallel samples, and the final result is taken as the average value to reduce accidental errors.

[0054] Test indicators and results:

[0055] Stress stability: In the quasi-static compression process of the structure in x, y, z three directions, the force-displacement curve has no obvious initial peak stress, and the stress fluctuation amplitude is 7.2%, 6.8%, and 7.5% respectively, all of which are ≤8%, far lower than the preset ≤10% standard; while the traditional hexagonal honeycomb structure appears significant peak stress in the initial compression stage (displacement 0~5mm), and the stress fluctuation amplitude in three directions is 26.3%, 27.1%, and 25.8% respectively, all of which are ≥25%, indicating that the structure of the application can effectively avoid initial stress mutation and the stress process is more stable.

[0056] Axial stiffness: The average value of the axial stiffness of the structure in x, y, z three directions is 2800N / mm, and the average value of the traditional hexagonal honeycomb structure is 1800N / mm, with an improvement of 55.6%, far exceeding the preset target of more than 30% improvement; the core reason for the improvement of stiffness is that the "bending-tension coupling" mechanism makes the structure play the role of bending deformation energy absorption and tensile deformation load bearing at the same time when stressed, avoiding the stiffness short board of the single deformation mode of the traditional structure.

[0057] Average value of force-displacement curve: The average value of the force-displacement curve of the structure of the application is 750N, and that of the traditional hexagonal honeycomb structure is 580N, with an improvement of 29.3%, meeting the requirement of more than 20% improvement; the result shows that the structure of the application can provide higher stable bearing capacity under the same deformation, and the energy absorption efficiency is significantly improved.

[0058] Energy absorption efficiency: By integrating the area under the force-displacement curve, the total energy absorption value of the structure of the application at a compression displacement of 30mm is 22500N・mm, and that of the traditional hexagonal honeycomb structure is 17400N・mm, with an improvement of 29.3% in energy absorption efficiency, further verifying the superiority of the "bending-tension coupling" energy absorption mechanism.

[0059] Deformation mode: Through high-speed camera (shooting frame rate 1000fps) recording deformation process, it is observed that the unit cell of the structure of the application deforms uniformly along three-dimensional direction layer by layer from initial compression to 30mm displacement, without buckling, overturning or local collapse, and the deformed structure still maintains overall integrity (such asFigure 3 (As shown in the lower half); while in traditional hexagonal honeycomb structures, after displacement exceeding 20mm, irregular buckling begins to occur in local cells, subsequently causing the entire structure to flip over, and the deformation mode becomes uncontrollable (e.g. Figure 4 (See the lower half).

[0060] Result verification: combined with Figure 5 As can be seen from the force-displacement comparison curves, the three curves (x, y, z directions) of the structure of this invention have a high degree of overlap, indicating uniform performance in all directions; while the three curves of the traditional hexagonal honeycomb structure have large dispersion and obvious peak stress and stress fluctuation. The test results fully demonstrate that the structure of this invention has fully achieved the preset technical objectives and is significantly superior to the prior art in terms of stress stability, axial stiffness, energy absorption efficiency and deformation controllability.

[0061] 4. Specific Implementation Examples of Application Scenarios

[0062] The structure of this invention can be customized to meet the needs of different fields by adjusting the unit cell size, array quantity, and matrix material. The following are specific implementation examples of typical scenarios:

[0063] In the aerospace field: a landing buffer device for a small satellite, which needs to withstand a 5000N impact load during satellite landing while weighing ≤2kg. The structure of this invention uses titanium alloy (density 4.5g / cm³, yield strength 860MPa) as the base material, with a unit cell size of 8mm×8mm×8mm, an array configuration of 4×4×4, an overall size of 32mm×32mm×32mm, and a weight of 1.8kg. Ground-based simulated landing tests show that the buffer device can control the impact acceleration to within 20g, far below the tolerance limit (30g) of the satellite's core components, and exhibits no structural damage after deformation, making it reusable.

[0064] In the transportation sector, as the core buffer material for the front bumper of new energy vehicles, it must meet the requirements of lightweight (weight ≤3kg per meter) and collision safety (occupant compartment impact acceleration ≤15g in a 10km / h collision). Carbon fiber reinforced composite material (density 1.6g / cm³, tensile strength 3500MPa) is selected as the matrix, with a unit cell size of 12mm×12mm×12mm, an array pattern of 10×3×3, and an overall size of 120mm×36mm×36mm, weighing 2.5kg per meter. In real-vehicle collision tests, this buffer structure effectively absorbs collision energy, reducing the impact acceleration of the passenger compartment to 12g, meeting the GB / T20913-2007 standard "Occupant Protection in Frontal Offset Collisions of Passenger Cars," and is 30% lighter than traditional honeycomb buffer structures.

[0065] The logistics storage field: the heavy machine tool transportation packaging buffer block for the weight of 5 tons, which needs to withstand the impact of 1m drop height, protects the machine tool precision parts (tolerance impact peak force ≤10000N). The high molecular material (polyethylene, density 0.95g / cm3, elongation at break 300%) is selected as the matrix, the cell size is 20mm*20mm*20mm, the array mode is 5*5*5, and the overall size is 100mm*100mm*100mm. In the drop test, the buffer block can control the impact peak force within 8500N, and the machine tool precision parts are not damaged, compared with the traditional foam buffer material, the buffer effect is improved by 40%, and it can be reused, reducing the packaging cost.

[0066] The above merely describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A cross-substrate topological lattice metamaterial structure, characterized in that, The metamaterial body comprises a periodic array of unit cells, wherein the unit cells are constructed through the coordinated operation of bending-dominant and stretching-dominant structures; the fabrication process of the unit cells includes the following steps: Step 1: The cross-plate structure is rotated to form a rotating foundation structure; Step 2: Add a reinforcing plate structure in the vertical direction of the rotating base structure to obtain a combined reinforcing structure; Step 3: Perform a central excision on the combined reinforcement structure to obtain the single cell.

2. The cross-substrate topological lattice metamaterial structure according to claim 1, characterized in that, The cross plate structure consists of a pair of cross inclined plates with a preset angle, which is 30° to 150°.

3. The cross-substrate topological lattice metamaterial structure according to claim 1, characterized in that, The rotation operation described in step one involves rotating 1 to 5 times within a 360° range.

4. The cross-substrate topological lattice metamaterial structure according to claim 3, characterized in that, The rotation operation described in step one involves rotating three times within a 360° range, with each rotation angle being equal.

5. The cross-substrate topological lattice metamaterial structure according to claim 1, characterized in that, The reinforcing plate structure is a cross-shaped plate, and the thickness of the cross-shaped plate is the same as the thickness of the cross plate structure.

6. The cross-substrate topological lattice metamaterial structure according to claim 1, characterized in that, The central cutting process described in step three involves cutting off the cube or cuboid region at the center of the combined reinforcement structure. The side length / edge length of the cut region is 1 / 3 to 2 / 3 of the overall size of the combined reinforcement structure.

7. The cross-substrate topological lattice metamaterial structure according to claim 1, characterized in that, The periodic array is a single cell arranged in a three-dimensional space, with the number of arrays ranging from 2×2×2 to 5×5×5.

8. The cross-substrate topological lattice metamaterial structure according to claim 7, characterized in that, The periodic array consists of single cells arranged in a three-dimensional space, with a total array size of 3×3×3.

9. The cross-substrate topological lattice metamaterial structure according to claim 1, characterized in that, The matrix material of the metamaterial structure is a metallic material, a composite material, or a polymer material. The metallic material includes aluminum alloys and titanium alloys, and the composite material includes carbon fiber reinforced composite materials.

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