Pre-folded thin-walled tube structure filled with density gradient honeycombs

Abstract

The invention relates to a pre-folded thin-walled tube structure filled with density gradient honeycombs. Comprising a pre-folded thin-wall square tube and a density gradient honeycomb filling structure filled in the pre-folded thin-wall square tube, the inner diameter and the outer diameter of the pre-folded thin-wall square pipe in the axial direction are not changed, the side wall face of the pre-folded thin-wall square pipe is a corrugated plate, the thickness of the corrugated plate is gradually increased from the near-impact side to the far-impact side in the axial direction of the pipe, the corrugated shape of the corrugated plate is a triangle, and the span of the triangle is gradually increased from the near-impact side to the far-impact side in the axial direction of the pipe. The density gradient honeycomb filling structure is formed by a plurality of thin-wall cell elements through a coincident boundary array, the cross section of each cell element is in a regular polygon shape, arc-shaped reinforced cell walls are arranged in all vertexes of the regular polygons, and the arc-shaped reinforced cell walls are gradually increased from the near-impact side to the far-impact side in the axial direction of the cell elements. The collision load transfer characteristic is remarkably improved, local damage and overall instability of the thin-wall structure are avoided, and the energy absorption efficiency of the thin-wall structure is improved.

Description

Technical Field

[0001] The invention belongs to the field of energy absorbing materials, in particular to a pre-folded thin-wall tube structure filled with a density gradient honeycomb. Background Art

[0002] With the rapid development of the automobile industry in recent years, the miniaturization, lightweight, electrification and intelligence of automobiles have brought greater technical challenges to the design of automobile collision safety. In the upgrading and application of automobile lightweight technology, metal thin-walled structures are widely used in the design of automobile crashworthy body structures due to their light weight, high specific strength and excellent energy absorption characteristics. When a collision occurs, the thin-walled tube structure in the automobile body is crushed and deformed under the instantaneous increase in impact force, effectively absorbing most of the energy, thereby achieving the purpose of protecting the driver. Therefore, the crashworthiness design and optimization of thin-walled tubes has 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 crash resistance of metal thin-walled tubes, including thin-walled tube cross-section configuration design, variable-section thin-wall, bionic multi-cell tube design, material filling and strengthening design, etc. Among them, patent CN108099829A discloses a functional gradient multi-cell thin-walled tube, including a thin-walled tube body, which is a hollow structure composed of at least one plate member three; the hollow structure includes a cell region or a plurality of cell regions equally divided by a second structural member composed of a plate member two, and a first structural member composed of a plate member one arranged in a "M" shape is arranged in the cell region, and the thickness of each plate member increases as a function from the collision head end to the fixed end of the thin-walled tube. Patent CN115289161A provides a new bionic energy-absorbing tube structure based on the characteristics of beetle elytra. The energy-absorbing tube structure is a multi-cell thin-walled tube obtained from the microstructure of beetle elytra, with pore columns, reinforcing ribs and heterogeneous material arrangement characteristics. The purpose of improving the energy absorption performance of the thin-walled tube is achieved through the reasonable configuration and cross-sectional form of two materials with different characteristics obtained by bionics.

[0004] The best solution currently available is to improve the impact energy absorption characteristics of thin-walled structures by changing the cross-section of thin-walled tubes and setting up structures such as partitions inside the thin-walled tubes. However, an ideal thin-walled structure should absorb as much energy as possible in a stable and controllable deformation mode. Secondly, its average collision force should be maximized to increase energy absorption, while its maximum peak crushing force should be minimized as much as possible to ensure the structural integrity of the rear-end protected passenger compartment. Although the above technical solution can improve the collision crushing force of thin-walled tubes, the peak collision force is also significantly increased at the same time. In addition, the thin-walled tube may buckle and become unstable during axial and oblique impacts due to its own excessive strength, and cannot maintain progressive deformation, resulting in poor energy absorption during the collision process. Summary of the invention

[0005] The object of the present invention is to provide a pre-folded thin-walled tube structure filled with a density gradient honeycomb.

[0006] The technical solution to achieve the purpose of the present invention is: a pre-folded thin-walled tube structure filled with a density gradient honeycomb, comprising a pre-folded thin-walled square tube and a density gradient honeycomb filling structure filled in the pre-folded 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 along the axial direction are unchanged. The side wall of the pre-folded thin-walled square tube is a corrugated plate. The thickness of the corrugated plate gradually increases from the near impact side to the far impact side along the tube axial direction. The corrugation shape of the corrugated plate is a triangle, and the span of the triangle is l v It gradually increases along the tube axis from the side close to the impact to the side far from the impact;

[0008] The density gradient honeycomb filling structure is formed by a plurality of thin-walled cells through an overlapping boundary array. The cross-sectional shape of the cell is a regular polygon, and each vertex of the regular polygon is provided with an arc-shaped strengthening cell wall, which gradually increases along the cell axis from the near impact side to the far impact side; the plurality of thin-walled cells are interconnected at the vertices to form a gradient strengthening region at the internal end points of the honeycomb structure.

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

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

[0011] Furthermore, the cross-sectional shape of the cell is a regular hexagon, and the radius of the arc-shaped strengthening cell wall gradually changes from L to Where L is the length of the side inside 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 pre-folded thin-walled tube structure filled with a density gradient honeycomb comprises the following steps:

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

[0015] Step (2): forming a density gradient honeycomb filling structure by strengthening the thin-walled cell structure designed by the polygonal cross-section vertex;

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

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

[0018] Compared with the prior art, the present invention has the following significant advantages:

[0019] When the density gradient honeycomb filled pre-folded thin-walled tube structure of the present invention is subjected to axial and oblique impact, the external pre-folded thin-walled tube will form a fixed plastic hinge deformation at the vertex of the triangle, presenting a wrinkle deformation mode of orderly folding inwards, and will not invade inwards or outwards during deformation. The buckling mode and energy absorption performance of the thin-walled tube under the action of axial and oblique external forces can be regulated, so that the thin-walled tube has a lower initial peak force and a more uniform compression process; at the same time, the density gradient honeycomb inside the thin-walled tube absorbs energy through cell wall buckling and in-plane deformation, forming an internal support strengthening effect on the wrinkled thin-walled tube, avoiding local instability deformation of the thin-walled tube, dispersing the impact force through overall deformation, and better realizing load transfer and energy absorption. The folding failure deformation of the existing thickness gradient honeycomb structure when subjected to impact is still concentrated at the vertex connection position of the cell wall, and the main stress concentration position is still at the vertex position of the honeycomb, and there is no stress induction function when receiving an impact, and it is impossible to continuously and stably absorb energy.

[0020] The present invention designs arc-shaped strengthening cell walls at each vertex position of the thin-walled cell, thereby forming a strengthening area at the internal end points of the honeycomb structure, which helps to form an axisymmetric progressive buckling deformation mode for ideal energy absorption. At the same time, the axial series strengthening design of the honeycomb structure is performed by changing the thickness of the arc-shaped cell walls of the thin-walled cell. The impact resistance is guided by the design without changing the macroscopic size of the honeycomb structure, and a density gradient honeycomb structure with different energy absorption characteristics is obtained.

[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.), has a high level of structural lightweight, can be filled into the internal cavity of a thin-walled beam by gluing or the like, and has a simple manufacturing and assembly process. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The figure is a schematic diagram of the design process of the pre-folded thin-walled tube structure filled with density gradient honeycomb of the present invention.

[0023] Figure 2 Schematic diagram of the structure of the pre-folded thin-walled tube of the present invention; (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 variable wall thickness of the pre-folded thin-walled tube of the present invention.

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

[0026] Figure 5 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 is a result diagram of the effectiveness verification of the pre-folded thin-walled tube structure filled with density gradient honeycomb of the present invention; wherein (a) is the impact force simulation result, and (b) is the energy absorption simulation result. DETAILED DESCRIPTION

[0029] The present invention is further described in detail below in conjunction with the accompanying drawings

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

[0031] Step 1, designing a triangular pre-folded thin-walled square tube structure according to the structural characteristics of the thin-walled tube;

[0032] Step 2, forming a density gradient honeycomb filling structure by using a thin-walled cell structure designed by reinforcing the vertices of a polygonal cross section;

[0033] Step 3, forming a pre-folded thin-walled tube structure filled with a density gradient honeycomb based on steps 1 and 2;

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

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

[0036] The pre-folded thin-walled tube structure has triangular folds with continuously changing heights within a fixed period prefabricated on the surface of the thin-walled tube, that is, a mountain shape with varying heights. Within the same period, the lower the peak value, the more sufficient the energy absorption characteristics of the corresponding triangular corrugation, and the corresponding contact stiffness is also greater. The combination of triangular corrugations with different peak values ​​can make the structure maintain a controllable overall collapsed shape when subjected to axial impact loads, and at the same time have the characteristics of high energy absorption and a smooth impact process, which can induce a specific folding deformation mode, so that the overall thin-walled tube and honeycomb structure has a lower initial peak force and a more uniform compression process.

[0037] Design a density gradient honeycomb filling structure: the thin-walled cell structure has the same shape, cross-sectional size and length, and multiple thin-walled cells form a honeycomb filling structure by overlapping boundaries. The cross-sectional shape of the cell can be a regular hexagon, a regular triangle, and similar polygons. Each vertex position of the polygon is provided with an arc-shaped strengthening cell wall with increased thickness. Multiple thin-walled cells are connected to each other at the vertices to form a strengthening area at the end point inside the honeycomb structure.

[0038] The thickness of the arc-shaped strengthening cell wall at the vertex of the thin-walled cell can be designed by changing the arc radius. The length of the inner side 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. The range of r is The front end is a regular hexagonal vertex-strengthened cell. The arc of the vertex reinforcement is used as the starting point. The radius of the arc is reduced from front to back, and the thickness of the vertex-strengthened cell wall gradually increases, and finally ends 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 change continuously along the axial direction, thereby forming an axially series-strengthened cell. Multiple cells can be connected to form an axially series-strengthened honeycomb, such as Figure 4 As shown in the figure, the cross-sectional dimensions of the honeycomb filling structure match those of the pre-folded thin-walled square tube. Compared with the uniform honeycomb, the collision force and energy absorption curve can be guided without changing the structural mass and macroscopic dimensions. Compared with other gradient honeycomb structures of the same mass, the serially reinforced honeycomb structure can reduce the initial collision load while ensuring the total energy absorption, and the contact load gradually increases and exceeds the same type of gradient honeycomb structure.

[0039] Based on the above content, a pre-folded thin-walled tube structure filled with a density gradient honeycomb is formed: 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) and At this time, the inner wall side length of the thin-walled tube is the same as the outer dimensions of the honeycomb structure, and the pre-folded thin-walled tube in step 1 is combined with the density gradient honeycomb filling structure in step 2 to form an integrated structure. The pre-folded thin-walled square tube can be prepared by thin plate bending and welding process; the corresponding corrugated shapes are cut out on both sides of the rolled differential thickness flat plate, and then the flat plate is bent into a corrugated plate along the length direction, and then the edges of the four corrugated plates are welded by laser welding technology to form a pre-folded thin-walled square tube; the density gradient honeycomb filling structure is injection molded with high-performance engineering plastics (such as PA66, PBE / PET, PPE / PA, etc.), and the honeycomb structure is connected to the inner wall of the thin-walled tube by gluing.

[0040] A 6×6 density gradient honeycomb filled pre-folded thin-walled tube structure model and a thickness gradient honeycomb structure model were respectively 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 the upper rigid wall downward. The downward pressing distance was 70% of the overall height of the honeycomb structure. CAE simulation calculations were run, and the superiority of the pre-folded thin-walled tube structure with density gradient honeycomb filling of the present invention was verified by comparison.

[0041] The density gradient honeycomb filled pre-folded thin-walled tube structure described in the present invention undergoes axial buckling deformation under the action of axial and oblique impact loads, forms fixed plastic hinge deformation in the corrugated section, presents an inward folding wrinkle deformation mode, and then enters a steady-state progressive buckling stage until it enters densification. At the same time, the density gradient honeycomb inside the thin-walled tube absorbs energy through cell wall buckling and in-plane deformation, forming an internal support strengthening effect on the wrinkled thin-walled tube. For the series gradient strengthened honeycomb structure, the front end honeycomb wall thickness that is subjected to collision is smaller and the local stiffness is lower, while the rear end honeycomb wall thickness is larger and the local stiffness is larger. Therefore, the load curve is lower at the initial stage of the collision and then gradually increases, which has a significant effect on protecting the rear end structure (such as Figure 7 shown).

Claims

1. A pre-folded thin-walled tube structure filled with a density gradient honeycomb, characterized in that: It comprises a pre-folded thin-walled square tube and a density gradient honeycomb filling structure filled in the pre-folded thin-walled square tube and bonded to the inner wall surface of the square tube; The inner diameter a and outer diameter b of the pre-folded thin-walled square tube along the axial direction are unchanged. The side wall of the pre-folded thin-walled square tube is a corrugated plate. The thickness of the corrugated plate gradually increases from the near impact side to the far impact side along the tube axial direction. The corrugation shape of the corrugated plate is a triangle, and the span of the triangle is l v It gradually increases along the tube axis from the side close to the impact to the side far from the impact; The density gradient honeycomb filling structure is formed by a plurality of thin-walled cells through an overlapping boundary array. The cross-sectional shape of the cell is a regular polygon, and each vertex of the regular polygon is provided with an arc-shaped strengthening cell wall, which gradually increases along the cell axis from the near impact side to the far impact side; the plurality of thin-walled cells are interconnected at the vertices to form a gradient strengthening region at the internal end points of the honeycomb structure.

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

3. The pre-folded thin-walled tube structure filled with a density gradient honeycomb 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 filled with a density gradient honeycomb according to claim 2, characterized in that: The cross-section of the cell is a regular hexagon, and the radius of the arc-shaped strengthening cell wall gradually changes from L to Where L is the length of the side inside the cell, and the thickness t of the regular hexagonal matrix remains unchanged.

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

6. A design method for a pre-folded thin-walled tube structure filled with a density gradient honeycomb as claimed in any one of claims 1 to 4, characterized in that: The steps include: Step (1): designing a triangular pre-folded thin-walled square tube structure; Step (2): forming a density gradient honeycomb filling structure by strengthening the thin-walled cell structure designed by the polygonal cross-section vertex; Step (3): filling the density gradient honeycomb filling structure of step (2) into the triangular pre-folded thin-walled square tube to form a pre-folded thin-walled tube structure filled with a density gradient honeycomb; Step (4): A three-dimensional model is established based on the structure in step (3), and CAE is used to verify the effectiveness of the pre-folded thin-walled tube structure filled with density gradient honeycomb.

Images