Design method of automobile bionic hierarchical thin-walled tube

Abstract

The invention provides a design method of a bionic hierarchical thin-walled tube, which solves the problems of complexity and low efficiency of the design method of the bionic hierarchical thin-walled tube in the prior art, and comprises the following steps of: calculating energy absorbed by a hierarchical hexagonal thin-walled tube theoretically according to a standard impact condition; establishing a prediction formula, and calculating theoretical average crushing force; a hierarchical thin-wall energy absorption pipe design scheme is provided according to a natural bionic prototype; calculating actual average crushing force; establishing a finite element model and carrying out a simulation experiment; carrying out a physical compression test to verify the reliability of the finite element model; verifying the reliability of the prediction formula; and the design target is checked according to the principle that the actual average crushing force should be larger than the theoretical average crushing force, and finally the target energy absorption structure meeting the design requirement is obtained. The design method is scientific and efficient, the design time can be effectively shortened, the collision resistance of the thin-walled pipe is improved, and the design cost is reduced.

Description

Technical Field

[0001] The present invention relates to the field of automotive energy absorption device design, and particularly to a design method for a bionic hexagonal hierarchical structure. Background Art

[0002] In the modern engineering field, especially in the automotive industry, the design of energy absorption devices is of great significance for vehicle collision safety. A good energy absorption device can protect the occupants during a collision. The design of multi-cell thin-walled energy absorption tubes changes the force and deformation modes by embedding different cells in the cross-section of the cylindrical energy absorption tube, improves the energy absorption efficiency, optimizes the energy absorption effect in a limited space, and has become an important design direction.

[0003] Currently, the design method of energy absorption devices mainly relies on the "empirical design - optimization analysis" process. This method is usually carried out after the overall layout of the vehicle chassis is completed. Engineers set the design parameters of the energy absorption device, including length, cross-sectional dimensions, material, wall thickness, etc., according to design experience and requirements. Subsequently, the performance of the energy absorption device is verified through simulation optimization analysis. If the energy absorption device fails to meet the expected design goals, engineers need to go back and redesign until the requirements are met. However, this design method mainly relies on design experience and requirements, and it is often difficult to achieve the expected goals in the initial design, resulting in a cumbersome design process, low efficiency, and high costs. Summary of the Invention

[0004] In order to provide a high-performance energy absorption structure, the present application applies bionic design concepts such as honeycombs and snowflakes to the energy absorption structure to optimize its performance; meanwhile, the present invention discloses a design method for a bionic hexagonal hierarchical structure, which uses simulation software to improve design efficiency and is helpful for subsequent simulation optimization.

[0005] Technical Solution

[0006] A design method for an automotive bionic hierarchical thin-walled tube, characterized in that the cross-sectional configuration of the automotive bionic hierarchical thin-walled tube is designed based on the hexagonal hierarchical structures of honeycombs, snowflakes or radiolarians, and includes a multi-level hexagonal cell array. Specifically,

[0007] The hexagonal cells are centered at the hexagonal geometric center and radiate and expand along six symmetric directions to form a filling structure; adjacent cells are topologically connected by sharing sides or corners to form a honeycomb-like network that fractals step by step from the center outwards; the radius D of the circumscribed circle of the cross-section of the thin-walled tube is a constant value and does not change with the increase in the number of levels n;

[0008] The design method includes the following steps:

[0009] Step 1, calculate the theoretically absorbed energy E of the hierarchical thin-walled tube according to the standard impact situation t , according to E tObtain the theoretical average crushing force MCF of the hierarchical thin-walled energy-absorbing tube;

[0010] Step 2, design a hierarchical thin-walled energy-absorbing tube model, which is a multi-level columnar configuration based on biological bionics, and the cross-sectional configuration is an n-order hexagonal hierarchical structure, where n≥2;

[0011] Step 3, derive the cross-sectional length formula based on the hierarchical thin-walled energy-absorbing tube model, extract the basic unit for analysis, and calculate the actual average crushing force MCFt of the model based on the length formula and the basic unit;

[0012] Step 4, establish a finite element model of the hierarchical thin-walled energy-absorbing tube, conduct impact simulation experiments, record the theoretical and actual average crushing force data, and determine the optimal design parameters.

[0013] Preferably, in step 1, the energy E theoretically absorbed by the hierarchical thin-walled tube t is expressed as: E t = E a ·α, where E a is the total vehicle collision energy, expressed as m is the impact mass, v is the speed, and α is the energy absorption ratio.

[0014] Preferably, in step 1, the theoretical average crushing force MCF = Et / h, where h is the crushing length.

[0015] Preferably, in step 3, extract the basic unit E m and calculate its membrane deformation energy respectively. The basic unit includes a corner unit and an X-shaped angle unit, where

[0016] the membrane deformation energy of the corner unit is expressed as:

[0017] the membrane deformation energy of the X-shaped angle is expressed as:

[0018] where M0 is the fully plastic moment, t is the initial wall thickness of the thin-walled tube, γ is the angle of the inflection point, h is the folding half-wavelength, is the angle of the intersection point, and a is the boundary width of the original model.

[0019] Preferably, in step 3, derive the formula f(n) for the number function of the membrane unit:

[0020]

[0021] where the side length of the cross-section of the thin-walled tube the wall thickness of the thin-walled tube

[0022] Preferably, in step 3, the actual average crushing force is expressed as:

[0023]

[0024] In the formula, λ is the dynamic factor, η is the effective crushing distance coefficient, σ0 is the material flow stress, and L T is the sum of the side lengths of all sides of the cross-section.

[0025] Preferably, in step 4, the established finite element model includes three parts: a fixed plate, a thin-walled tube, and a moving plate. Among them, the bottom of the thin-walled tube is connected to the fixed plate, and the top of the thin-walled tube is crushed by the moving plate; based on this finite element model, an impact simulation experiment is carried out, the crushing force and energy absorption data are recorded, the numerical values of the actual average crushing force and the theoretical average crushing force are compared. If the actual average crushing force > the theoretical average crushing force, then each level is compared, the level with the best performance is selected, and finally the target energy-absorbing structure that meets the design requirements is obtained. Otherwise, the parameters are corrected and recalculated until the conditions are met, or the bionic hierarchical structure is redesigned.

[0026] Preferably, the parameter correction rule is: when the difference between the actual average crushing force and the average crushing force is less than 10%, the wall thickness t is adjusted; when the difference is greater than or equal to 10%, the bionic hierarchical structure is redesigned and the wall thickness is adjusted.

[0027] The present invention also discloses an automotive bionic hierarchical thin-walled tube designed by the above method. The cross-sectional configuration is designed based on the hexagonal hierarchical structure of honeycombs, snowflakes or radiolarians, and includes a multi-level hexagonal cell array. The hexagonal cells are centered on the hexagonal geometric center and radiate and expand along six symmetric directions to form a filling structure; adjacent cells are topologically connected by sharing sides or corners to form a honeycomb-like network that fractals step by step from the center outwards; the radius D of the circumscribed circle of the cross-section of the thin-walled tube is a constant value and does not change with the increase of the number of levels n, and the circumscribed circle radius is constant; the longitudinal direction of the thin-walled tube is direct tension.

[0028] Preferably, the number of levels n of the hexagonal cells is 5.

[0029] Beneficial effects

[0030] (1) The bionic design of the present invention based on the hexagonal hierarchical structure has achieved remarkable improvement in mechanical properties: the hexagonal hierarchical structure realizes uniform stress distribution through the topological arrangement of cells with corner-to-corner arrangement, effectively reducing local stress concentration. The actual average crushing force of the 5-level structure (n = 5) reaches 87.14 kN, which is 2.31 times higher than the actual average crushing force of 37.67 kN of the traditional hexagonal structure (n = 1).

[0031] (2) The bionic design of the present invention based on the hexagonal hierarchical structure has achieved remarkable improvement in impact resistance stability: the fractal characteristics of the hexagonal honeycomb make the crushing process show a progressive folding mode (such asFigure 2 Schematic diagram after collision); At the same time, the bionic design of the hexagonal hierarchical structure disclosed in the present invention significantly improves the energy absorption capacity of its planned energy absorption box, and its prediction formula can adaptively adjust the parameters of each hexagon according to the size results obtained from the design of specific vehicle models, accurately predicting whether its design meets the usage requirements (comparing theoretical MCF and actual MCF);

[0032] (3) The present invention adopts the mass equivalent design criterion to achieve topology optimization. Its lightweight advantage needs to be indirectly characterized by the structural efficiency improvement coefficient (i.e., the energy absorption efficiency per unit mass), rather than the traditional direct mass reduction path; Under the constraint of constant mass, gradient thin-wall design is realized through multi-level topology reconstruction. At the same time, the multi-level structure improves the energy absorption efficiency through two mechanisms: increased density (increase in the number of levels) and strain rate strengthening. Experimental data shows that when n = 5, the increase in the initial peak force is relatively small, less than 25%, while the specific energy absorption (SEA) increases by more than 100%;

[0033] (4) The design method of the present invention uses the simplified super-folded unit theory and the average crushing force formula to guide the improvement design. Therefore, it is more efficient than the existing design method based on experience, and also helps with later simulation optimization, providing new insights and theoretical support for designing engineering structures with stronger energy absorption capacity and impact resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The present patent will be further described below in conjunction with the drawings and embodiments.

[0035] Figure 1 Schematic diagram of the bionic hierarchical thin-walled tube before collision for an embodiment of the present invention;

[0036] Figure 2 Schematic diagram of the bionic hierarchical thin-walled tube after collision for an embodiment of the present invention;

[0037] Figure 3 is Flow chart of the bionic hierarchical thin-walled tube design in the specific implementation manner of an embodiment of the present invention;

[0038] Figure 4 Schematic diagram of the example structure for an embodiment of the present invention (the hierarchy increases from left to right);

[0039] Figure 5 Graph showing the relationship between the crushing force and the compression distance during the compression of MT and HHMT for an embodiment of the present invention.

[0040] Reference numerals: 1 - corner basic unit, 2 - X-shaped basic unit. DETAILED DESCRIPTION OF THE INVENTION

[0041] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0042] Embodiment 1

[0043] The present invention discloses a bionic hierarchical thin-walled tube for an automobile, as Figure 1 and Figure 2 shown. The bionic hierarchical thin-walled tube is a columnar structure composed of hexagonal cells, and its cross-sectional configuration is designed based on the hexagonal hierarchical structures of honeycombs, snowflakes or radiolarians, including a multi-layer hierarchical hexagonal cell array. The hexagonal cells radiate and expand along six symmetric directions with the hexagonal geometric center as the origin to form a filling structure; adjacent cells are topologically connected by sharing sides or corners to form a honeycomb network that fractals step by step from the center to the outside; the radius D of the circumscribed circle of the cross-section of the thin-walled tube is a constant value and does not change with the increase of the number of layers n. The design parameters mainly include materials, the number of layers n of the multi-cell tube, the wall thickness t of the multi-cell tube, the total mass m of the structure, the axial length H of the multi-cell tube, the crushing length h; the radius D of the circumscribed circle. In this embodiment, considering the manufacturing cost, etc., the longitudinal direction of the hierarchical thin-walled tube is a direct stretching structure.

[0044] Embodiment 2

[0045] As as shown in Figure 3 shown, the present invention discloses a design method for a bionic hierarchical thin-walled tube for an automobile, including the following steps:

[0046] 1) Calculate the energy E theoretically required to be absorbed by the hierarchical hexagonal thin-walled tube according to the standard impact situation t .

[0047] In this embodiment, it is set that the impact mass received by the vehicle body is m = 500 kg, the speed is 8 m / s, and the collision angle is 0°. Then the total collision energy E a of the whole vehicle is:

[0048]

[0049] The energy absorption ratio α of the thin-walled energy-absorbing tube to the total collision energy is generally obtained according to engineering experience. In this embodiment, the calculation is carried out according to the energy absorption ratio α = 50%. Thus, the energy E t absorbed by the energy-absorbing structure under this collision condition is calculated as:

[0050] E t = E a ×50% = 16 kJ × 50% = 8 kJ.

[0051] 2) Establish a prediction formula to obtain the theoretical average crushing force MCF from the ratio of the energy E to be absorbed by the thin-walled energy-absorbing tube to its crushing length h. t The theoretical average crushing force MCF is obtained from the ratio of the energy E to be absorbed by the thin-walled energy-absorbing tube to its crushing length h.

[0052] The length H and crushing ratio γ of the thin-walled energy-absorbing tube can be given by the engineer according to experience or by referring to the target vehicle. In this embodiment, it is set that H = 200 mm and γ = 60%.

[0053] It can be obtained that the crushing length L = γh = 200 mm × 60% = 120 mm. Then the theoretical average crushing force MCF is:

[0054] MCF = Et / h = 8 KJ / 120 mm ≈ 66.7 KJ.

[0055] 3) Propose a design scheme for a hierarchical thin-walled energy-absorbing tube based on a bionic prototype in nature.

[0056] The hierarchical thin-walled energy-absorbing tube is designed as a multi-level columnar configuration based on biological bionics, including polygon units arranged diagonally. In this embodiment, the bionic prototype is a structure with hierarchical hexagonal features such as honeycombs and snowflakes. The cross-section of the model contains n-order hexagonal hierarchies, with the order increasing and the circumradius D remaining constant. The circumradius is set according to specific engineering requirements. In this example, it is set that D = 120 mm.

[0057] The increase in order means that the hexagonal cells are further subdivided into smaller hexagons inside.

[0058] In this embodiment, the order n = 2, 3, 4, 5. As Figure 4 shown, the leftmost model structure is a simple hexagonal frame (n = 1). This hexagon is composed of six equilateral triangles, forming a basic hexagonal cell. The hierarchical thin-walled energy-absorbing tube of this application is composed based on this hexagonal cell. Figure 4 Shown as the second, third, fourth, and fifth from the left are the second-order, third-order, fourth-order, and fifth-order hierarchical thin-walled energy-absorbing tubes respectively. Second-order hierarchical thin-walled energy-absorbing tube: Multiple such hexagonal cells are connected together through shared edges to form a two-dimensional honeycomb grid. Each unit is still an independent hexagon, but they are closely connected to each other, enhancing the overall structural stability. Third-order to fifth-order hierarchical thin-walled energy-absorbing tubes: Inside each hexagonal cell, it is further subdivided into smaller hexagons respectively, forming a denser and more complex multi-order honeycomb-like structure. The structure of each level maintains the basic shape of the hexagon, only increasing gradually in quantity and complexity. Through gradual refinement and optimization in this application, the maximum of the structural performance is achieved while maintaining the lightweight feature.

[0059] 4) Extract the basic unit E according to the hierarchical design structure m Calculate its thin-film deformation energy.

[0060] The basic unit includes a corner unit and an X-shaped angle unit. Among them,

[0061] The film deformation energy of the corner unit is expressed as:

[0062] The film deformation energy of the X-shaped angle is expressed as: In the formula, M0 is the fully plastic moment, which is expressed as: is the flow stress of the material, σ y and σ u represent the yield stress and the ultimate stress respectively; r is the power-law index of the material, t is the initial wall thickness of the thin-walled tube, γ is the angle of the inflection point, h is the folding half-wavelength, is the angle of the intersection point, and a is the boundary width of the original model.

[0063] In this example, there are two types of basic units: a 120° corner and an X-shaped 60° angle. Among them, the calculation formula for the 120° corner unit is:

[0064]

[0065] The calculation formula for the X-shaped 60° angle unit is:

[0066]

[0067] 5) Derive the cross-section length formula f(n) based on the number of basic units of each order.

[0068] Derive the cross-section length formula by calculating the number of each basic unit and combining the side length of each unit:

[0069] The side length of the cross-section of the thin-walled tube The wall thickness of the thin-walled tube

[0070] According to the specific structure of the bionic hierarchical thin-walled tube, the side length a n and the wall thickness t n , derive the function f(n) of the number of basic film energy units at each level:

[0071] In this example, from Figure 4 it can be seen that are the corner unit and the X-shaped unit respectively, and f(n1) and f(n2) are the numbers of the corner unit and the X-shaped unit respectively.

[0072]

[0073] Thus, the function f(n) of the number of basic film energy units at each level is obtained as:

[0074]

[0075] 6) Calculate the actual average crushing force of the bionic hierarchical thin-walled tube according to the basic unit derivation formula and the cross-sectional length derivation formula;

[0076] In this embodiment, the material is selected as AA6061 O, λ is the dynamic factor, and it takes 1.3, 1.35, 1.4, 1.5 respectively as the number of layers increases (n = 2, 3, 4, 5). η is the effective crushing distance coefficient, and its value is usually taken in the range of 0.7 - 0.75. In this embodiment, η is taken as 0.73. The power-law index r of this material ranges from 0.21 to 0.23. In this embodiment, r is set to 0.23, and the material flow stress σ y and σ u represent the yield stress and the ultimate stress respectively. L T is the sum of the lengths of all flanges, which needs to be derived according to the designed cross-section. For the AA6060 O material selected in this embodiment, these parameters are: σ y = 80 MPa, σ u = 173 MPa, n = 0.23. The actual average crushing force MCFt is calculated by the following formula, and the calculation results are shown in the MCF column of Table 1 below:

[0077]

[0078] 7) Establish a finite element model and conduct simulation experiments:

[0079] In this embodiment, a finite element software is used to establish a model of the hierarchical thin-walled tube and conduct impact simulation experiments, recording the crushing force and energy absorption data. Among them, the finite element model consists of a fixed plate, a thin-walled tube, and a moving plate. The bottom of the thin-walled tube is connected to the fixed plate, and the top of the thin-walled tube is crushed by the moving plate. The model design parameters include material properties, number of layers, wall thickness distribution, axial and radial geometric dimensions, crushing response length, boundary constraint conditions, and overall mass control parameters. The finite element simulation is carried out using the explicit nonlinear finite element software LS-DYNA.

[0080] 8) Conduct a physical compression test, compare the simulation experiment data with the experimental data to verify the reliability of the finite element simulation experiment. If the error does not meet the requirements, re-model the experiment until it meets the requirements;

[0081] In this embodiment, the results of the physical compression test show that the error between the simulation experiment data and the experimental data is within 10%, meeting the requirements.

[0082] 9) Finite element simulation verification was carried out on all models. By comparing the theoretical values with the simulation values, the reliability of the prediction formula was verified. In this embodiment, the mass m and the circumscribed circle radius D of all models were designed as customized values, taking m = 0.5 kg and D = 120 mm respectively. The error between the simulated value and the theoretical value of the crushing force was within 3%, verifying the reliability of the prediction formula.

[0083] Table 1: Calculation and simulation results of the average crushing force MCFt of the hierarchical thin-walled energy-absorbing tube in this example

[0084]

[0085] 10) Structural design verification and optimization were carried out: Design verification was carried out based on the criterion that the actual average crushing force needs to exceed the theoretical value (the theoretical value was obtained by calculating with the basic formula ). If the standard was not met, the design parameters needed to be adjusted to re-perform the simulation calculation or reconstruct the bionic structure, and the cycle was iterated until the design requirements were met. After passing the verification, performance comparison was carried out on the multi-level structure, and the hierarchical configuration with the best mechanical properties and economic balance was selected. It should be noted during this iterative optimization process: When an abnormal situation where the theoretical value is higher than the measured value occurs, parametric adjustment should be carried out; for the compliant solutions, the energy absorption efficiency can be improved by appropriately increasing the number of structural levels, but a Pareto optimal relationship needs to be established between the mechanical gain and the cost increment. Generally, it is recommended to control the number of levels within the range allowed by the material processing technology.

[0086] In this embodiment, according to the calculation results in Table 1, it can be seen that the 3rd-order, 4th-order, and 5th-order structures all meet the design goals. Since the mass and the outer interface radius of each structure are the same, considering the crashworthiness performance, the 5th-order structure design is the best. The finally determined optimal design parameters are: the number of levels n = 5, the wall thickness t = 0.55 mm, and the circumscribed circle radius D = 120 mm.

[0087] In summary, the final design of the target hierarchical thin-walled energy-absorbing tube of the present invention is completed.

[0088] To further illustrate the excellent mechanical properties of the target hierarchical thin-walled energy-absorbing tube with a hexagonal hierarchical structure disclosed by the present invention, Table 2 presents the data comparison of the structural performance of traditional circles, squares, triangles, and hexagons. For some traditional structures, when the default wall thickness is set to 1.5 mm and the crushing speed is 100 m / s, the initial peak force IPF and the average crushing force MCF are shown in Table 2 below. It can be seen from Table 2 that the regular hexagonal structure has better comprehensiveness and can have the smallest initial peak force and a larger MCF under the same other parameters.

[0089] Table 2 Comparison table of traditional structure performance data

[0090]

[0091] FromFigure 5 It can be seen that as the compression distance increases, the required compression force also gradually increases. The curve shapes and slopes of each material are different, indicating that there are differences in their behavioral characteristics when being compressed. Among them, the curve of MT looks the steepest among all the curves, meaning that a greater force is required to compress it at the same compression distance; while the curve of HHMT5 is the gentlest among all the curves, meaning that it is relatively softer or more elastic, more prominent in mechanical properties, and has a greater energy absorption advantage.

[0092] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A design method for a bionic hierarchical thin-walled tube of an automobile, characterized in that, The cross-sectional configuration of the automotive bionic hierarchical thin-walled tube is based on the hexagonal hierarchical structure design of honeycombs, snowflakes or radiolarians, and includes a multi-level hexagonal cell array. Specifically, the hexagonal cells are radiated and expanded along six symmetric directions with the geometric center of the hexagon as the origin to form a filling structure; adjacent cells are topologically connected by sharing edges or angles to form a honeycomb network that is fractalized step by step from the center to the outside; the radius D of the circumscribed circle of the cross-sectional area of the thin-walled tube is a constant value and does not change with the increase of the number of levels n; The design method includes the following steps: Step 1, calculate the energy E theoretically absorbed by the hierarchical thin-walled tube according to the standard impact condition t , according to E t obtain the theoretical average crushing force MCF of the hierarchical thin-walled energy-absorbing tube; Step 2, designing a hierarchical thin-walled energy-absorbing tube model, wherein the model is a multi-level columnar configuration based on biomimetic, and the cross-sectional configuration is an n-order hexagonal hierarchical structure, where n≥2; Step 3, deriving a cross-sectional length formula based on the hierarchical thin-walled energy absorbing tube model, extracting basic units for analysis, and calculating the actual average crushing force MCFt of the model based on the length formula and the basic units; Step 4: Establish a finite element model of the layered thin-walled energy-absorbing tube, conduct impact simulation experiments, record theoretical and actual average crushing force data, and determine the optimal design parameters.

2. The method according to claim 1, wherein In Step 1, the energy E theoretically absorbed by the hierarchical thin wall t is expressed as: E t = E a ·α, where E a is the total vehicle collision energy, expressed as m is the impact mass, v is the speed, and α is the energy absorption ratio.

3. The method according to claim 2, characterized in that, In step 1, the theoretical average crushing force MCF = Et / h, where h is the crushing length.

4. The method according to claim 3, wherein In step 3, the basic unit E is extracted m The film deformation energy thereof is calculated respectively. The basic unit includes a corner unit and an X-shaped included angle unit, where The thin-film deformation energy of the corner unit is expressed as: The film deformation energy of the X-shaped angle is expressed as: Where M0 is the fully plastic bending moment, t is the initial wall thickness of the thin-walled tube, γ is the angle of the inflection point, h is the folded half wavelength, is the angle of the intersection point, and a is the boundary width of the original model.

5. The method according to claim 4, wherein In step 3, the formula for the number of membrane units f(n) is derived: In the formula, the side length of the thin-walled tube cross-section The wall thickness of the thin-walled tube 6. The method according to claim 5, wherein In step 3, the actual average crushing force is expressed as: where λ is the dynamic factor, η is the effective crushing distance coefficient, σ0 is the material flow stress, and L T is the sum of the side lengths of all sides of the cross-section.

7. The method according to any one of claims 1-6, characterized in that, In step 4, the established finite element model includes three parts: a fixed plate, a thin-walled tube and a moving plate, wherein the bottom of the thin-walled tube is connected to the fixed plate, and the top of the thin-walled tube is passively crushed by the plate; an impact simulation experiment is carried out based on the finite element model, and the crushing force and energy absorption data are recorded, and the numerical values of the actual average crushing force and the theoretical average crushing force are compared. If the actual average crushing force > the theoretical average crushing force, each level is compared, and the level with the best performance is selected to finally obtain the target energy absorption structure that meets the design requirements. Otherwise, the parameters are corrected and recalculated until the conditions are met, or the bionic hierarchical structure is redesigned.

8. The method according to claim 7, characterized in that The parameter correction rule is: when the difference between the actual average crushing force and the average crushing force is less than 10%, adjust the wall thickness t; when the difference is greater than or equal to 10%, redesign the bionic hierarchical structure and adjust the wall thickness.

9. An automotive bionic hierarchical thin-walled tube, characterized in that, Designed according to any one of the methods of claims 1-8, the cross-sectional configuration is based on the hexagonal hierarchical structure design of honeycombs, snowflakes or radiolarians, including a multi-level hexagonal cell array, the hexagonal cells take the geometric center of the hexagon as the origin, and radiate and expand along six symmetric directions to form a filling structure; adjacent cells are topologically connected by sharing edges or angles to form a honeycomb network that is fractalized step by step from the center to the outside; the radius D of the circumscribed circle of the cross-section of the thin-walled tube is a constant value, which does not change with the increase of the number of levels n, and the radius of the circumscribed circle is constant; the longitudinal direction of the thin-walled tube is directly stretched.

10. The thin-walled tube according to claim 9, wherein, The number of hexagonal cell levels n=5.

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