Multi-tube telescopic energy-absorbing device and processing method of paper-folding energy-absorbing tube

Abstract

The application discloses a multi-tube telescopic energy-absorbing device and a processing method of a folding paper energy-absorbing tube. The device comprises the folding paper energy-absorbing tube and end plates. The folding paper energy-absorbing tube is at least provided with two, and a single folding paper energy-absorbing tube is a hollow quadrilateral tube, which comprises two mirror image sawtooth straight plate surfaces and two mirror image folding paper bent plate surfaces. The sawtooth straight plate surface is a straight plate with uniform thickness, and the left and right sides of the sawtooth straight plate surface are bending curves coinciding with the folding paper bent plate surface. The folding paper bent plate is a wave-shaped bent plate provided with a plurality of pre-folding creases arranged horizontally. The folding paper energy-absorbing tubes are vertically arranged between the two end plates and fixedly connected with the end plates. The method comprises the following steps: S1, processing the sawtooth straight plate; S2, processing the folding paper bent plate; and S3, welding. The folding paper energy-absorbing tube is provided with pre-folding creases on the folding paper bent plate surface, so that the folding paper energy-absorbing tube can actively control the folding time sequence generated in the deformation of the energy-absorbing tube, and the energy absorption of the device is more stable.

Description

Technical Field

[0001] This invention relates to the field of buffer technology, and in particular to a multi-tube stacked energy-absorbing device and a method for processing a paper-folding energy-absorbing tube. Background Technology

[0002] The development of high-performance energy-absorbing structures is a crucial theme in the field of safety protection. Energy-absorbing devices are the core of passive safety protection for rail vehicles and automobiles, and also important components for the landing buffer phase of various aircraft in the aerospace field. Currently, a wide variety of energy-absorbing structures based on the deformation principles of metal structures, such as stacking, expansion, necking, tearing, and cutting, have been extensively developed, providing safety protection for the lives of vehicle occupants and the core components of engineering machinery. Generally, an ideal energy-absorbing structure includes the following aspects: high energy absorption and specific energy absorption, low peak impact force, stable energy absorption capacity, and low production cost. Stacked energy-absorbing structures based on the progressive plastic stacking deformation mode of thin-walled metal tubes are a widely used and relatively ideal energy-absorbing structure. Thin-walled metal tubes themselves are very lightweight, and their plastic deformation of strands and flow extension can absorb high amounts of energy, thus possessing ideal specific mass mechanical properties. Meanwhile, compared to other energy-absorbing structures, the stacked energy-absorbing structure is relatively simple to construct. It only requires a thin-walled tube and a few basic structures such as upper and lower pressure plates to complete the entire energy absorption task, thus resulting in low production costs.

[0003] However, conventional thin-walled tube stacked energy-absorbing structures have two main drawbacks: First, the impact force required to overcome the yield strength of the tube and transform it from elastic deformation to plastic deformation to form the first fold during impact is relatively large, meaning the energy absorption process has a high peak impact force. Second, during the plastic deformation stage, when achieving the progressive folding deformation mode, the thin-walled tube will generate several clearly defined folds. The formation of these folds will cause a corresponding number of distinct peaks and valleys in the stress of the structure, making the energy absorption stability of conventional thin-walled tube stacked energy-absorbing structures very limited. These two defects can pose significant risks to the safety of occupants and protected core components in practical applications and should be avoided as much as possible. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a multi-tube stacked energy absorption device and a processing method for paper-folding energy absorption tube.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a multi-tube stacked energy absorption device, comprising origami energy absorption tubes and end plates, wherein there are at least two origami energy absorption tubes, each of which is a hollow tetrahedral tube, comprising two mirror-arranged serrated straight plates and two mirror-arranged origami curved plates; the serrated straight plates are straight plates of uniform thickness, and the left and right sides of the serrated straight plates are bending curves that coincide with the origami curved plates; the origami curved plates are wavy curved plates with several pre-made creases arranged horizontally, and each origami energy absorption tube is placed vertically between the two end plates and fixedly connected to the end plates.

[0006] As a further improvement to the above technical solution:

[0007] The height of each origami energy-absorbing tube is the same.

[0008] The independent segments of the origami bending plate are straight plates or curved plates.

[0009] The origami energy-absorbing tube is divided into an induction zone, a main energy-absorbing zone, and a tail zone. The origami energy-absorbing tube is divided into segments by pre-made creases. The induction zone is the first segment at the top of the origami energy-absorbing tube, with a height of h1. The tail zone is the last segment at the bottom of the origami energy-absorbing tube, with a height of h2. The main energy-absorbing zone consists of the remaining segments in the middle of the origami energy-absorbing tube, with a height of h3 for each segment. The induction zone heights of each origami energy-absorbing tube are at least two different, and the sum of h1 and h2 in each origami energy-absorbing tube is equal.

[0010] The maximum width of the serrated straight plate surface in the induction zone is set to L1, and the maximum width of the serrated straight plate surface in the main energy absorption zone segment is set to L2, where L1 < L2.

[0011] When the number of origami energy-absorbing tubes is greater than 2, the height h1 of the induction zone of each origami energy-absorbing tube is arranged in an arithmetic sequence.

[0012] The origami bending plate is a vertically oriented straight plate in the tail section.

[0013] A method for manufacturing an origami energy-absorbing tube, wherein the serrated straight surface is composed of serrated straight plates and the origami curved surface is composed of origami curved plates, specifically including the following steps:

[0014] S1: Processing the serrated straight plate: Based on the designed shape of the origami energy-absorbing tube, determine the serrated curve shape on both sides of the serrated straight plate, cut it from the board, and process the serrated straight plate.

[0015] S2: Processing paper bending plates: Based on the sawtooth curve shape of the straight plate, select a suitable straight plate and bend it into a shape corresponding to the sawtooth curve;

[0016] S3: Welding: Weld two serrated straight plates to two folded paper curved plates to form a folded paper energy-absorbing tube.

[0017] Compared with existing technologies, the advantages of this invention are as follows: The origami energy-absorbing tube of this invention, by providing pre-made creases on the origami bending plate surface, actively controls the timing of folds generated during the deformation of the energy-absorbing tube, resulting in more stable energy absorption. Compared with some conventional corrugated tubes, the origami energy-absorbing tube of this invention includes two serrated straight plates, which improves the specific energy absorption of the device and makes the parts of the device easier to process and store, reducing production costs. Furthermore, by setting the induction zone heights of the different crease energy-absorbing tubes at equal intervals, the energy absorption is significantly increased while the peak force is significantly reduced, further improving the energy absorption stability of the device. Attached Figure Description

[0018] Figure 1 This is a three-dimensional schematic diagram of the overall structure of Embodiment 1 of the device of the present invention.

[0019] Figure 2 This is a schematic front view of the overall structure of Embodiment 1 of the device of the present invention.

[0020] Figure 3 This is a right view illustrating the overall structure of the device in Embodiment 1 of the present invention.

[0021] Figure 4 This is an exploded view of the origami energy-absorbing tube structure in Embodiment 1 of the present invention.

[0022] Figure 5 Compression characteristic curve of conventional square tube.

[0023] Figure 6 This is a compression characteristic curve of the origami energy-absorbing tube in Embodiment 1 of the present invention.

[0024] Figure 7 This is a compression characteristic curve of Embodiment 1 of the present invention.

[0025] Figure 8 This is a schematic front view of the straight plate structure of Embodiment 2 of the present invention.

[0026] The labels in the diagram represent:

[0027] 1. Origami energy-absorbing tube; 11. Serrated straight plate surface; 12. Origami curved plate surface; 13. Pre-made crease; 14. Inducing zone; 15. Main energy-absorbing zone; 16. Tail zone; 2. End plate. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] Device Example 1:

[0030] Figures 1 to 7 The first embodiment of the present invention is shown, a multi-tube stacked energy absorption device, including origami energy absorption tubes 1 and end plates 2. There are at least two origami energy absorption tubes 1. Each origami energy absorption tube 1 is a hollow tetrahedral tube, including two mirror-arranged serrated straight plate surfaces 11 and two mirror-arranged origami curved plate surfaces 12. The serrated straight plate surface 11 is a straight plate with uniform thickness, and the left and right sides of the serrated straight plate surface 11 are bending curves that coincide with the origami curved plate surface 12. The origami curved plate is a wavy curved plate with several pre-made creases 13 arranged horizontally. All the origami energy absorption tubes 1 are placed vertically together between the two end plates 2 and are fixedly connected to the end plates 2.

[0031] Please refer to details. Figure 5 In the diagram, the arrows indicate the load direction. When a conventional square tube is subjected to axial compression, it generates several wrinkles, undergoing progressive shrinkage deformation. The stress-strain curve sequentially shows three stages: a large peak stress, several small stress fluctuations, and a rapid increase in stress after densification. Each wrinkle in the square tube corresponds to one fluctuation in the stress-strain curve. The first wrinkle is generated when the square tube transitions from elastic deformation to plastic deformation, and therefore has the largest stress value, known as the peak stress. Subsequent fluctuations are all generated by the plastic deformation of the square tube, with approximately equal stress values. From a macroscopic perspective, all parts of the square tube are identical, but from a microscopic perspective, different locations within the square tube have different subtle defects. Defective areas have lower yield strength and are more prone to wrinkle formation. Therefore, the strand positions that generate each wrinkle in the square tube are relatively random, making it difficult to actively control the timing, and the phases of the peaks and troughs of the stress-strain curve are also difficult to predict accurately. Furthermore, each fold in the compression of the square tube requires the creation of strands from the straight wall, resulting in drastic changes in the amplitude of the corresponding stress-strain curve, i.e., violent fluctuations in the curve. Since the integral of the curve corresponds to energy absorption, this means that the energy absorption of the square tube is very unstable.

[0032] Please refer to details. Figure 4 and Figure 6The origami energy-absorbing tube 1 of this invention includes two origami-shaped curved surfaces 12, which are bent into several creases like origami. During the compression process of the structure, the pre-set crease locations have a lower yield strength than other locations on the tube, thus transforming into horizontal strands. This achieves two goals: firstly, during the stacking deformation, the folds of the tube only occur at the crease locations, providing a prerequisite for controlling the fold generation location; secondly, the compression force required to generate each fold is lower, and the subsequent stress fluctuations are smoother than those of conventional square tubes because each crease acts as a strand. Energy absorption is more stable. Since the interval corresponding to each crease on the origami tube is transformed into a fold in the tube during compression, the timing of folds generated during deformation can be actively controlled by actively controlling the position of the creases on the energy-absorbing tube. Furthermore, since each fold corresponds to a fluctuation in the compressive stress-strain curve, a control method is provided for the phase of each fluctuation in the stress-strain curve. Finally, the integral of the curve corresponds to the energy absorption of the tube, thus achieving precise control of the energy absorption performance of the tube through origami design.

[0033] Furthermore, the origami energy-absorbing tube 1 of the present invention includes two serrated straight plates 11. These serrated straight plates 11 are straight plates of uniform thickness, ensuring that the two opposite surfaces of the origami energy-absorbing tube 1 maintain the straight walls of a square tube. The serrated straight plates 11 have added serrations at their edges, corresponding to the bending shape of the origami curved plates 12, thus forming a tetrahedral tube. Compared to some conventional corrugated tubes, the straight plates in this invention have a higher specific energy absorption. The linkage design of the two curved plates and two straight plates in the tube not only induces initial buckling and guides the deformation development path but also maintains the overall energy absorption and specific energy absorption of the structure at a higher level. Compared to additive manufacturing tubes, this invention maintains the excellent elasticity and plasticity of the metal sheet, allowing for stable progressive shrinkage deformation during energy absorption without easily becoming brittle. In addition, straight plates can be cut and processed from metal sheets, resulting in a simple structure; straight plates themselves are easy to store and process; when a single tube uses a serrated straight plate, the two opposite sides remain flat, which is easier to modularly store than curved structures, and also facilitates subsequent multi-tube assembly operations. Therefore, compared to some complex additive manufacturing structures, it achieves a similar energy absorption effect but has a lower processing cost.

[0034] The origami energy-absorbing tube 1 can be made by pre-folding and welding a metal sheet with good plasticity. The main view of the serrated straight plate 11 contains most of the external features of the origami energy-absorbing tube 1, which facilitates more external design. It can be cut from the sheet and easily controls the shape of the entire origami energy-absorbing tube 1. The origami curved plate 12 embodies the pre-folding concept of origami structure. It is made by bending a whole straight plate and plays a role in customizing and pre-controlling the deformation mode of the energy-absorbing tube.

[0035] End plate 2 consists of an upper end plate and a lower end plate, both made of rigid metal sheets. There are no specific requirements regarding shape or thickness; the shape can be freely modified according to the application scenario, provided the strength and rigidity requirements are met. For example, anti-climbing teeth can be added to the upper end plate, and mounting bases can be added to the lower end plate. During device operation, the lower end plate remains relatively stationary, acting as a base plate, while the upper end plate applies axial loading to the folding energy-absorbing tube 1, acting as a pressure plate.

[0036] In this embodiment, all the origami energy-absorbing tubes 1 have the same height. This identical structure ensures that each origami energy-absorbing tube 1 is simultaneously subjected to load and can deform according to a preset deformation mode, while also facilitating modular production and installation.

[0037] In this embodiment, the independent segments of the origami bending plate 12 are straight plates. This structure makes the origami energy-absorbing tube 1 easier to process and produce, thereby reducing manufacturing costs.

[0038] In this embodiment, the origami energy-absorbing tube 1 is divided into an induction zone 14, a main energy-absorbing zone 15, and a tail zone 16. The origami energy-absorbing tube 1 is divided into segments by pre-made creases 13. The induction zone 14 is the first segment at the top of the origami energy-absorbing tube 1, and its height is set to h1. The tail zone 16 is the last segment at the bottom of the origami energy-absorbing tube 1, and its height is set to h2. The main energy-absorbing zone 15 consists of the remaining segments in the middle of the origami energy-absorbing tube 1. At least two origami energy-absorbing tubes 1 have different heights h1 in their induction zones 14, and the sum of h1 and h2 in each origami energy-absorbing tube 1 is equal.

[0039] The origami energy-absorbing tube 1 is divided into three functional zones: an induction zone 14, a main energy-absorbing zone 15, and a tail zone 16, laying the foundation for multi-tube combinations. By controlling the different heights of the induction zones 14 of different tubes, the timing and phase of the initial wrinkle triggering of different tubes are misaligned. Based on this, the timing of the occurrence of all subsequent wrinkles can be further controlled, thus providing a basis for accurately controlling the fluctuations of the stress-strain curve of tube compression.

[0040] The main energy-absorbing zone 15 is the primary energy-absorbing part of the origami energy-absorbing tube 1. Because the sum of h1 and h2 in each origami energy-absorbing tube 1 is equal, the total height of the main energy-absorbing zone 15 is the same for origami energy-absorbing tubes 1 of different specifications. Based on the pre-set number and position of creases, plastic compression deformation occurs during compression, generating a corresponding number of folds, thereby absorbing a large amount of energy. Although the stress-strain curve ranges corresponding to the main energy-absorbing zones of different origami energy-absorbing tubes 1 exhibit almost identical fluctuations, the different heights h1 of the upper induction zone 14 lead to a misalignment in the fold triggering sequence.

[0041] The tail section 16 is not the main energy absorption area. Because it is located at the tail of the origami energy-absorbing tube 1, it may not participate in energy absorption due to the compressible stroke of the tube. The height h2 of the adaptive tail section changes with the height h1 of the top induction section, its main function being to ensure that the total height of each energy-absorbing tube is the same. The combination of the induction section 14 and the tail section 16 ensures that tubes of different specifications are of equal length, thus allowing multiple tubes to be loaded simultaneously, but the deformation sequence of paper energy-absorbing tubes 1 of different specifications varies.

[0042] In this embodiment, the maximum width of the serrated straight plate surface 11 in the induction zone 14 is set to L1, and the maximum width of the serrated straight plate surface 11 in the main energy absorption zone 15 segment is set to L2, where L1 < L2.

[0043] This structure ensures that the yield strength of the induction zone 14 is lower than that of the main energy absorption zone 15, thereby guaranteeing that the deformation of the entire pipe always starts from the induction zone 14, which plays the role of inducing initial wrinkles. The domino effect generated by the initial wrinkles ensures the subsequent gradual shrinkage of the pipe.

[0044] In this embodiment, the segments of the origami energy-absorbing tube located in the main energy-absorbing zone are at the same height. This structure makes the stress-strain curve of the origami energy-absorbing tube 1 more stable, ensuring the stability of the device's energy absorption.

[0045] In this embodiment, four origami energy-absorbing tubes 1 are provided, and the heights of the induction zones 14 of each origami energy-absorbing tube 1 are in an arithmetic progression. In this structure, based on a single origami energy-absorbing tube 1, multiple origami energy-absorbing tubes 1 are further combined in a modular design, so that the height h1 of the top induction zone 14 of each origami energy-absorbing tube 1 is different in an arithmetic progression. This allows each origami energy-absorbing tube 1 to undergo elastic deformation simultaneously under the action of the upper end plate 2, but the total time required for the initial wrinkles to form through folding plastic deformation is different, thus causing a misalignment in the initial peak stress of the stress-strain curve. Since the subsequent main energy-absorbing zones 15 of different tubes are completely identical, the misalignment of the initial wrinkles and initial peak stress is further reflected in the misalignment of all subsequent wrinkles and stress peaks.

[0046] like Figure 7As shown, the origami energy-absorbing tube 1 first undergoes plastic deformation, producing wrinkles 1.1. Subsequently, energy-absorbing tubes 2-4 deform sequentially, producing wrinkles 2.1-4.1. Similarly, the second and third wrinkles of each origami tube undergo temporal misalignment, resulting in four stress-strain curves with misaligned peaks and troughs. Taking two sinusoidal function curves as an example, if their phase difference is π, their superposition results in the peaks and troughs canceling each other out, forming a straight line. Similarly, by superimposing the stress-strain curves of several sets of origami energy-absorbing tubes 1 with their misaligned peaks and troughs, the stress-strain curve of the entire energy-absorbing structure becomes a very smooth curve. The integral of this curve, i.e., the area enclosed by the horizontal axis of the coordinate system, corresponds to the energy absorption of the structure. It can be seen that the energy absorption of this invention reaches the sum of the four tubes, while the peak impact force is not a linear superposition of the four tubes, but rather has an impact force peak with an amplitude close to that of a single tube and a non-sharp change, achieving a significant increase in energy absorption while significantly reducing the peak force. More importantly, the stress in the subsequent platform stage of this invention is very stable, with a very stable energy absorption capacity, which can provide maximum safety protection for occupants and protected objects, making it an energy absorption device with ideal performance.

[0047] In this embodiment, the origami bending plate 12 is a vertically oriented straight plate in the tail section 16. Because the tail section 16 is not the main energy absorption area, and due to its location at the bottom of the origami energy-absorbing tube 1, it may not participate in energy absorption due to the compressible stroke of the tube. The height h3 of the tail section 16 varies with the height h1 of the induction zone 14, its main function being to ensure that the total height of each energy-absorbing tube is the same. Therefore, setting the tail section 16 of the origami bending plate 12 as a vertical straight plate facilitates the production and processing of the origami energy-absorbing tube 1. On the other hand, it also increases the cross-sectional area of ​​the tail section 16, which is beneficial to enhancing the structural stability of the device.

[0048] Device Example 2:

[0049] A second embodiment of a multi-tube stacked energy absorption device is basically the same as that in embodiment 1, except that the independent segments of the folded bending plate surface 12 in this embodiment are curved plates. The shape of the single-tube structure of the present invention is not limited to that in embodiment 1. Figure 4 The combination shown is a serrated straight plate surface 11 with triangular teeth and a folded paper-bent plate surface 12 of a straight plate segment. For example... Figure 8As shown, the serrations of the serrated straight plate surface 11 can be further designed. For example, the triangular teeth on the edge of the serrated straight plate surface 11 can be changed into sine curves with equal amplitude. Furthermore, it can be designed into various shapes such as sine curves with gradually changing amplitude, double-layer sine curves, and petal-shaped teeth. At the same time, the origami bent plate surface 12 is also bent into a corresponding shape. Each segment is bent into a curved plate with a corresponding curve shape, while still maintaining the simple combination design structure of two straight plates and two bent plates of the single origami energy-absorbing tube 1. Thus, a more suitable tube shape for the energy-absorbing curve can be selected according to the actual engineering application.

[0050] Method Implementation Examples:

[0051] A method for processing a paper-folding energy-absorbing tube 1, used to process the paper-folding energy-absorbing tube 1 as described in Embodiment 1 of the manufacturing apparatus, wherein the serrated straight plate surface 11 is composed of a serrated straight plate and the paper-folding curved plate surface 12 is composed of a paper-folding curved plate, specifically including the following steps:

[0052] S1: Processing the serrated straight plate: Based on the designed shape of the origami energy-absorbing tube 1, determine the serrated curve shape on both sides of the serrated straight plate, cut it from the board, and process the serrated straight plate.

[0053] S2: Processing paper bending plates: Based on the sawtooth curve shape of the straight plate, select a suitable straight plate and bend it into a shape corresponding to the sawtooth curve.

[0054] S3: Welding: Weld two serrated straight plates to two folded paper curved plates to form a folded paper energy-absorbing tube 1.

[0055] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the scope of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the present invention, should fall within the protection scope of the present invention.

Claims

1. A multi-tube stacked energy absorption device, characterized in that: It includes a paper-folding energy-absorbing tube (1) and an end plate (2). The paper-folding energy-absorbing tube (1) has at least two tubes. Each paper-folding energy-absorbing tube (1) is a hollow tetrahedral tube, including two mirror-arranged serrated straight plate surfaces (11) and two mirror-arranged paper-folding curved plate surfaces (12). The serrated straight plate surface (11) is a straight plate with uniform thickness. The left and right sides of the serrated straight plate surface (11) are bending curves that coincide with the paper-folding curved plate surface (12). The paper-folding curved plate surface (12) is a wavy curved plate with several pre-made creases (13) set horizontally. The paper-folding energy-absorbing tubes (1) are placed vertically between the two end plates (2) and are fixedly connected to the end plates (2). The origami energy-absorbing tubes (1) are all the same height; The independent segments of the origami bending plate surface (12) are straight plates or curved plates; The origami energy-absorbing tube (1) is divided into an induction zone (14), a main energy-absorbing zone (15), and a tail zone (16). The origami energy-absorbing tube (1) is divided into segments by pre-made creases (13). The induction zone (14) is the first segment at the top of the origami energy-absorbing tube (1) and its height is set to h1. The tail zone (16) is the last segment at the bottom of the origami energy-absorbing tube (1) and its height is set to h2. The main energy-absorbing zone (15) is the remaining segments of the origami energy-absorbing tube (1) located in the middle. At least two of the origami energy-absorbing tubes (1) have different heights h1 in their induction zones (14), and the sum of h1 and h2 in the origami energy-absorbing tube (1) is equal. The origami energy-absorbing tube (1) has the same height in each segment of the main energy-absorbing area (15); The maximum width of the sawtooth straight plate surface (11) in the induction zone (14) is set to L1, and the maximum width of the sawtooth straight plate surface (11) in the main energy absorption zone (15) is set to L2, where L1 < L2.

2. The multi-tube stacked energy absorption device according to claim 1, characterized in that: When the number of origami energy-absorbing tubes (1) is greater than 2, the height h1 of the induction zone (14) of the origami energy-absorbing tubes (1) is arranged in an arithmetic sequence.

3. The multi-tube stacked energy absorption device according to claim 2, characterized in that: The origami bending plate surface (12) is a straight plate with a vertical direction in the tail area (16) segment.

4. A method for processing a paper-folding energy-absorbing tube, characterized in that: For processing and manufacturing the multi-tube stacked energy absorption device according to any one of claims 1-3, the sawtooth straight plate surface (11) is composed of a sawtooth straight plate, and the folded paper curved plate surface (12) is composed of a folded paper curved plate, specifically including the following steps: S1: Processing the sawtooth straight plate: Based on the shape of the designed origami energy-absorbing tube (1), determine the sawtooth curve shape on both sides of the sawtooth straight plate, cut it from the plate, and process the sawtooth straight plate. S2: Processing paper bending plates: Based on the sawtooth curve shape of the straight plate, select the straight plate to bend into a shape corresponding to the sawtooth curve; S3: Welding: Weld two serrated straight plates to two folded paper curved plates to form a folded paper energy-absorbing tube (1).

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