A density gradient honeycomb-filled pre-folded thin-walled tube structure

Abstract

This invention relates to a density gradient honeycomb-filled pre-folded thin-walled tube structure. It includes a pre-folded thin-walled square tube and a density gradient honeycomb filling structure within the pre-folded thin-walled square tube. The inner and outer diameters of the pre-folded thin-walled square tube remain constant along the axial direction. The sidewalls of the pre-folded thin-walled square tube are corrugated plates, with the thickness of the corrugated plates gradually increasing from the near-impact side to the far-impact side along the tube's axial direction. The corrugated shape of the corrugated plates is triangular, and the span of the triangles gradually increases from the near-impact side to the far-impact side along the tube's axial direction. The density gradient honeycomb filling structure is formed by multiple thin-walled cells arrayed with overlapping boundaries. The cross-sectional shape of the cells is a regular polygon, and each vertex of the regular polygon has an arc-shaped reinforcing cell wall, which gradually increases in size from the near-impact side to the far-impact side along the cell's axial direction. This invention significantly improves the impact load transfer characteristics, avoids local damage and overall instability of the thin-walled structure, and improves the energy absorption efficiency of the thin-walled structure.

Description

Technical Field

[0001] The present invention belongs to the field of energy-absorbing materials, and particularly relates to a pre-folded thin-walled tube structure filled with density-gradient honeycombs. Background Art

[0002] With the rapid development of the automotive industry in recent years, the miniaturization, lightweight, electrification, and intelligence of automobiles have posed greater technical challenges to automotive crash safety design. In the upgrade and application of automotive lightweight technologies, metal thin-walled structures have been widely used in the design of crashworthy vehicle body structures due to their light weight, high specific strength, and excellent energy-absorbing characteristics. During a collision, the thin-walled tube structure in the vehicle body undergoes crushing deformation under the instantaneously increased impact force, effectively absorbing most of the energy, thereby achieving the purpose of protecting the driver. Therefore, the design and optimization of the crashworthiness of thin-walled tubes have also become a hot issue in the current automotive research field.

[0003] In recent years, researchers have proposed a series of methods to improve the crashworthiness of metal thin-walled tubes, including the design of thin-walled tube cross-section configurations, variable cross-section thin-walled tubes, bionic multi-cell tube design, material filling and strengthening design, etc. Among them, Patent CN108099829A discloses a functionally graded multi-cell thin-walled tube, which includes a thin-walled tube body. The thin-walled tube body is a hollow structure composed of at least one plate member three; the hollow structure includes a cell region or multiple cell regions equally divided by a second structural member composed of plate member two, and a first structural member composed of plate member one arranged in a "rice" shape is provided in the cell region, and the thickness of each plate member increases in a functional relationship from the collision head end to the fixed end of the thin-walled tube. Patent CN115289161A provides a novel bionic energy-absorbing tube structure based on the characteristics of beetle elytra. This energy-absorbing tube structure is a multi-cell thin-walled tube obtained from the microscopic structure of beetle elytra and having the characteristics of pore columns, ribs, and the arrangement of dissimilar materials. Through the reasonable configuration and cross-section form of two different characteristic materials obtained by bionics, the purpose of improving the energy-absorbing performance of the thin-walled tube is achieved.

[0004] The currently best-performing solution is to improve the impact energy-absorbing characteristics of the thin-walled structure by changing the cross-section form of the thin-walled tube and setting structures such as partitions inside the thin-walled tube. However, an ideal thin-walled structure should absorb as much energy as possible in a stable and controllable deformation manner. Secondly, it should maximize its average collision force to increase the energy absorption, and at the same time, it should minimize its maximum peak crushing force to avoid ensuring the structural integrity of the protected occupant compartment at the rear end. Although the above technical solutions can increase the collision crushing force of the thin-walled tube, the peak collision force also increases significantly. Moreover, the thin-walled tube may undergo buckling instability due to its excessive strength during axial and oblique impact processes, and it cannot maintain progressive deformation, resulting in poor energy absorption effect during the collision process. Summary of the Invention

[0005] The purpose of this invention is to provide a pre-folded thin-walled tube structure with density gradient honeycomb filling.

[0006] The technical solution to achieve the purpose of this invention is: a density gradient honeycomb filled prefolded thin-walled tube structure, including a prefolded thin-walled square tube and a density gradient honeycomb filled structure filled in the prefolded thin-walled square tube and bonded to the inner wall of the square tube.

[0007] The inner diameter *a* and outer diameter *b* of the pre-folded thin-walled square tube remain constant along the axial direction. The sidewall of the pre-folded thin-walled square tube is a corrugated plate. The thickness of the corrugated plate gradually increases from the side near the impact to the side away from the impact along the tube's axial direction. The corrugated shape of the plate is triangular, and the span of the triangle is *l*. v The rate gradually increases along the pipe axis from the side near the impact to the side farther from the impact.

[0008] The density gradient honeycomb filling structure is formed by multiple thin-walled cells arrayed with overlapping boundaries. The cross-sectional shape of the cell is a regular polygon, and each vertex of the regular polygon has an arc-shaped reinforcing cell wall. The arc-shaped reinforcing cell wall gradually increases along the cell axis from the near impact side to the far impact side. Multiple thin-walled cells are connected to each other at the vertices to form a gradient reinforcement region at the endpoints inside the honeycomb structure.

[0009] Furthermore, the pre-folded thin-walled square tube is made of aluminum alloy, while the density gradient honeycomb filling structure is made of plastic.

[0010] Furthermore, the density gradient honeycomb filling structure is made of PA66, PBE / PET, or PPE / PA, through injection molding or 3D printing.

[0011] Furthermore, the cell cross-sectional shape is a regular hexagon, and the value of the arc-shaped reinforced cell wall radius gradually transitions from L to [missing value]. Where L is the inner side length of the cell, and the thickness t of the regular hexagonal matrix remains unchanged.

[0012] Furthermore, it is used in the automotive field.

[0013] A design method for the above-mentioned density gradient honeycomb-filled pre-folded thin-walled tube structure includes the following steps:

[0014] Step (1): Design a triangular pre-folded thin-walled square tube structure;

[0015] Step (2): A density gradient honeycomb filling structure is formed by a thin-walled cell structure reinforced by the vertices of a polygonal cross section;

[0016] Step (3): Fill the triangular pre-folded thin-walled square tube with the density gradient honeycomb filling structure of step (2) to form a density gradient honeycomb filling pre-folded thin-walled tube structure.

[0017] Step (4): Based on the structure in step (3), establish a three-dimensional model and use CAE to verify the effectiveness of the density gradient honeycomb filled pre-folded thin-walled tube structure.

[0018] Compared with the prior art, the significant advantages of this invention are:

[0019] The density gradient honeycomb-filled pre-folded thin-walled tube structure of this invention, when subjected to axial and oblique impacts, exhibits a fixed plastic hinge deformation at the vertices of the triangles, resulting in an inwardly ordered folding deformation pattern. This deformation does not involve intrusion inwards or outwards, allowing for control over the buckling mode and energy absorption performance of the thin-walled tube under axial and oblique external forces. This results in a lower initial peak force and a more uniform compression process. Simultaneously, the density gradient honeycomb inside the thin-walled tube absorbs energy through cell wall buckling and in-plane deformation, creating an internal support and strengthening effect on the folded thin-walled tube. This prevents local instability deformation and disperses the impact force through overall deformation, thus better achieving load transfer and energy absorption. Existing thickness gradient honeycomb structures, when subjected to impact, still concentrate folding failure deformation at the vertices of the cell walls, with the main stress concentration points remaining at the vertices of the honeycomb. Furthermore, they lack stress-inducing function upon impact and cannot continuously and stably absorb energy.

[0020] This invention designs arc-shaped reinforced cell walls at each vertex of thin-walled cells, thereby forming reinforced regions at the internal endpoints of the honeycomb structure. This helps to form an ideal energy-absorbing axisymmetric progressive buckling deformation mode. At the same time, by changing the thickness of the arc-shaped cell walls of the thin-walled cells to carry out axial series reinforcement design of the honeycomb structure, it is possible to achieve a guiding design for impact resistance without changing the macroscopic dimensions of the honeycomb structure, and obtain density gradient honeycomb structures with different energy absorption characteristics.

[0021] The honeycomb structure of the present invention can be injection molded using high-performance engineering plastics (such as PA66, PBE / PET, PPE / PA, etc.), resulting in a high level of lightweight structure. It can be filled into the internal cavity of thin-walled beams by means of adhesive bonding, and the manufacturing and assembly process is simple. Attached Figure Description

[0022] Figure 1 This is a schematic diagram illustrating the design process of the pre-folded thin-walled tube structure with density gradient honeycomb filling according to the present invention.

[0023] Figure 2 This is a schematic diagram of the pre-folded thin-walled tube of the present invention; wherein (a) is a top view, (b) is a front view, and (c) is an axonometric view.

[0024] Figure 3 This is a schematic diagram of the variable wall thickness of the pre-folded thin-walled tube of the present invention.

[0025] Figure 4This is a schematic diagram of the axial series density gradient honeycomb filling structure of the present invention.

[0026] Figure 5 These are schematic diagrams of different cross-sections of the density gradient honeycomb filling structure of the present invention.

[0027] Figure 6 This is a schematic diagram of the density gradient honeycomb filled pre-folded thin-walled tube structure of the present invention.

[0028] Figure 7 The figure shows the effectiveness verification results of the pre-folded thin-walled tube structure with density gradient honeycomb filling of the present invention; where (a) is the impact force simulation result and (b) is the energy absorption simulation result. Detailed Implementation

[0029] The present invention will now be described in further detail with reference to the accompanying drawings.

[0030] like Figure 1 As shown, the design of a pre-folded thin-walled tube structure with density gradient honeycomb filling involves the following steps:

[0031] Step 1: Design a triangular pre-folded thin-walled square tube structure based on the structural characteristics of the thin-walled tube;

[0032] Step 2: A density gradient honeycomb filling structure is formed by a thin-walled cell structure reinforced by the vertices of a polygonal cross-section.

[0033] Step 3: Based on Step 1 and Step 2, a density gradient honeycomb-filled pre-folded thin-walled tube structure is formed;

[0034] Step 4: Based on the structure in Step 3, establish its three-dimensional model and use CAE technology to verify the effectiveness of the density gradient honeycomb filled pre-folded thin-walled tube structure.

[0035] like Figure 2 As shown, the pre-folded thin-walled square tube is a triangular thin-walled structure formed by stamping metal material. The cross-section of the folded section of the structure is a triangle with continuously varying height. The folded section is evenly distributed along the axial direction of the thin-walled tube. The triangular thin-walled structure can achieve continuous variation of axial thickness through flexible rolling technology to form a rolled differential thickness plate. The edges of the four corrugated plates are connected to each other by welding to form the pre-folded thin-walled square tube.

[0036] This pre-folded thin-walled tube structure features triangular creases with continuously varying heights over a fixed period on the surface of the thin-walled tube, resembling undulating mountain peaks. Within the same period, the lower the peak value, the more energy-absorbing the corresponding triangular corrugations are, resulting in greater contact stiffness. By combining triangular corrugations with different peak values, the structure can maintain a controllable overall collapse shape under axial impact loads while simultaneously absorbing more energy and exhibiting a smooth impact process. This induces specific folding deformation modes, resulting in a lower initial peak force and a more uniform compression process for the overall thin-walled tube and honeycomb structure.

[0037] Density gradient honeycomb filling structure design: thin-walled cell structure with consistent shape, cross-sectional size and length, multiple thin-walled cells form a honeycomb filling structure by overlapping boundaries. The cross-sectional shape of the cell can be a regular hexagon, an equilateral triangle or similar polygon. Each vertex of the polygon is provided with an arc-shaped reinforcing cell wall with increased thickness. Multiple thin-walled cells are connected to each other at the vertices to form a reinforced region at the internal endpoints of the honeycomb structure.

[0038] The thickness of the arc-shaped reinforced cell wall at the apex of the thin-walled cell can be designed by changing the radius of the arc. If the side length of the regular hexagonal cell is L, the wall thickness of the six sides of the cell is t, and the radius of the arc-shaped cell wall is r, then the range of r is... The front end is a regular hexagonal vertex-reinforced cell. Starting from the arc of the vertex reinforcement, the radius of the arc decreases sequentially from front to back, thus the thickness of the vertex-reinforced cell wall gradually increases, eventually ending with a circular cross-section, forming a density gradient honeycomb structure based on vertex reinforcement. That is, the thickness of the arc-shaped cell wall of the thin-walled cell can continuously change along the axial direction, thereby forming axially tandem reinforced cells. Multiple cells connected together can form an axially tandem reinforced honeycomb, such as... Figure 4 As shown; the cross-sectional dimensions of the honeycomb filling structure match the cross-sectional dimensions of the pre-folded thin-walled square tube. Compared with uniform honeycomb, it can achieve the guiding design of collision force and energy absorption curve without changing the structural mass and macroscopic dimensions. Compared with other gradient honeycomb structures of the same mass, the series-reinforced honeycomb structure can reduce the initial collision load while ensuring the total energy absorption, and the contact load gradually increases, exceeding that of the same type of gradient honeycomb structure.

[0039] Based on the above, a density gradient honeycomb-filled pre-folded thin-walled tube structure is formed: such as Figure 5 As shown, taking a honeycomb structure with n×m cells as an example, the side length of a single cell is L, and the side length of the honeycomb is nL+(n-1)L). At this point, the inner wall side length of the thin-walled tube is the same as the outer dimensions of the honeycomb structure. The pre-folded thin-walled tube in step 1 and the density gradient honeycomb filling structure in step 2 are combined to form an integrated structure. The pre-folded thin-walled square tube can be prepared by thin plate bending and welding process; the two sides of the rolled differential thickness plate are cut with corresponding corrugated shapes, and then the plate is bent into a corrugated plate along the length direction. Then, the edges of the four corrugated plates are welded by laser welding technology to form the pre-folded thin-walled square tube; the density gradient honeycomb filling structure is injection molded using high-performance engineering plastics (such as PA66, PBE / PET, PPE / PA, etc.), and the honeycomb structure is bonded to the inner wall of the thin-walled tube by adhesive.

[0040] A 6×6 density gradient honeycomb-filled pre-folded thin-walled tube structure model and a thickness gradient honeycomb structure model were established. The static compression condition of the material was used as the test condition. The material of the pre-folded thin-walled tube was set to aluminum alloy, and the honeycomb structure materials were all engineering materials. The boundary condition was to fix the lower surface of the honeycomb structure and press down the upper rigid wall by 70% of the overall height of the honeycomb structure. CAE simulation calculations were run to verify the superiority of the density gradient honeycomb-filled pre-folded thin-walled tube structure of the present invention.

[0041] The density gradient honeycomb-filled pre-folded thin-walled tube structure described in this invention undergoes axial buckling deformation under axial and oblique impact loads, forming fixed plastic hinge deformation in the corrugated section, exhibiting an inward folding wrinkling deformation mode, and then entering a steady-state progressive buckling stage until it reaches compaction. Simultaneously, the density gradient honeycomb inside the thin-walled tube absorbs energy through cell wall buckling and in-plane deformation, forming an internal support and strengthening effect on the wrinkled thin-walled tube. For the series-gradient reinforced honeycomb structure, the front-end honeycomb wall thickness is smaller and the local stiffness is lower, while the rear-end honeycomb wall thickness is larger and the local stiffness is higher. Therefore, the load curve is lower in the initial stage of the impact and then gradually increases, which has a significant effect on protecting the rear-end structure (e.g., Figure 7 (As shown).

Claims

1. A pre-folded thin-walled tube structure filled with density gradient honeycomb, characterized in that, It includes a pre-folded thin-walled square tube and a density gradient honeycomb filling structure that is filled inside the pre-folded thin-walled square tube and bonded to the inner wall of the square tube; The inner diameter *a* and outer diameter *b* of the pre-folded thin-walled square tube remain constant along the axial direction. The sidewall of the pre-folded thin-walled square tube is a corrugated plate. The thickness of the corrugated plate gradually increases from the side near the impact to the side away from the impact along the tube's axial direction. The corrugated shape of the plate is triangular, and the span of the triangle is *l*. v The rate gradually increases along the pipe axis from the side near the impact to the side farther from the impact. The density gradient honeycomb filling structure is formed by multiple thin-walled cells arrayed with overlapping boundaries. The cross-sectional shape of the cell is a regular polygon, and each vertex of the regular polygon has an arc-shaped reinforcing cell wall. The thickness of the arc-shaped reinforcing cell wall gradually increases along the cell axis from the near impact side to the far impact side. Multiple thin-walled cells are connected to each other at the vertices to form a gradient reinforcement region at the endpoints inside the honeycomb structure.

2. The pre-folded thin-walled tube structure with density gradient honeycomb filling according to claim 1, characterized in that, The pre-folded thin-walled square tube is made of aluminum alloy, while the density gradient honeycomb filling structure is made of plastic.

3. The pre-folded thin-walled tube structure with density gradient honeycomb filling according to claim 2, characterized in that, The density gradient honeycomb filling structure is made of PA66, PBE / PET or PPE / PA, by injection molding or 3D printing.

4. The pre-folded thin-walled tube structure with density gradient honeycomb filling according to claim 2, characterized in that, The cell section shape is a regular hexagon, and the radius of the arc-shaped reinforced cell wall gradually transitions from L to [value missing]. Where L is the inner side length of the cell, and the thickness t of the regular hexagonal matrix remains unchanged.

5. The pre-folded thin-walled tube structure with density gradient honeycomb filling according to any one of claims 1-4, characterized in that, Used in the automotive industry.

6. A design method for a pre-folded thin-walled tube structure with density gradient honeycomb filling as described in any one of claims 1-4, characterized in that, Includes the following steps: Step (1): Design a triangular pre-folded thin-walled square tube structure; Step (2): A density gradient honeycomb filling structure is formed by a thin-walled cell structure reinforced by the vertices of a polygonal cross section; Step (3): Fill the triangular pre-folded thin-walled square tube with the density gradient honeycomb filling structure of step (2) to form a density gradient honeycomb filling pre-folded thin-walled tube structure. Step (4): Based on the structure in step (3), establish a three-dimensional model and use CAE to verify the effectiveness of the density gradient honeycomb filled pre-folded thin-walled tube structure.

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