Multi-stable based repeatable energy absorbing structure

Abstract

The present application belongs to the technical field of multi-stable structure, and particularly relates to a repeatable energy absorption structure based on multi-stable state. The present application comprises a unit cell; the inner-layer double-stable energy absorption structure model comprises double-stable unit bodies; the outer-layer double-stable energy absorption structure model is arranged outside the inner-layer double-stable energy absorption structure model; the outer-layer double-stable energy absorption structure model comprises double-stable unit bodies; each half double-stable unit is connected to the inner-layer double-stable energy absorption structure model and the outer-layer double-stable energy absorption structure model at two ends, respectively. The present application provides the repeatable energy absorption structure in which the outer-layer double-stable energy absorption structure model surrounded by a plurality of unit cells is arranged outside the inner-layer double-stable energy absorption structure model, and the half double-stable unit is used to connect the outer-layer double-stable energy absorption structure model and the inner-layer double-stable energy absorption structure model. Under the action of impact load, the repeatable energy absorption structure is subjected to buckling transition, so that the energy absorption characteristics and impact resistance of the repeatable energy absorption structure are significantly improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of multi-stable structure, and relates to a repeatable energy absorption structure based on multi-stable state. BACKGROUND

[0002] Impact phenomena exist in all aspects of daily life and industrial production, such as the impact of a spacecraft landing on the ground, the impact of a fired bullet on the gun barrel, and the like. Obviously, if the impact process is not controlled, not only the service life of the equipment will be reduced, but also safety hazards will be formed.

[0003] Therefore, the person skilled in the art develops a multi-stable structure formed by an array of bistable units for the impact phenomenon, which realizes the absorption and dissipation of energy through a jump buckling in the process of transition between adjacent stable states. At present, the existing multi-stable energy absorption structure usually absorbs energy in a single buckling jump process, and the value of the absorbed energy is relatively limited.

[0004] Therefore, it is urgent to invent a repeatable energy absorption structure based on multi-stable state to solve the above technical problems. SUMMARY

[0005] The application aims to provide a repeatable energy absorption structure based on multi-stable state to solve the technical problem of poor energy absorption characteristics of the repeatable energy absorption structure in the impact resistance process.

[0006] To achieve the above-mentioned purpose, the specific technical scheme of the repeatable energy absorption structure based on multi-stable state provided by the application is as follows: comprising a unit cell; wherein the unit cell comprises a hyperbolic beam, a connecting rod, two mutually parallel crossbars and side rods;

[0007] The tail ends of the two side rods are respectively connected to the two ends of one crossbar, and the head ends are respectively connected to the two ends of the hyperbolic beam; the two ends of the connecting rod are respectively fixed to the middle part of the hyperbolic beam and the middle part of the other crossbar; further comprising:

[0008] An inner-layer bistable energy absorption structure model comprising at least one layer of bistable unit bodies connected in parallel by M unit cells;

[0009] An outer-layer bistable energy absorption structure model, which is sleeved outside the inner-layer bistable energy absorption structure model and assembled into a repeatable energy absorption structure with a concentric ring cross-sectional shape; the outer-layer bistable energy absorption structure model comprises at least two layers of bistable unit bodies stacked in sequence, and M is a positive integer;

[0010] A number of N half-bistable units, N being a positive integer, and two ends of each of the half-bistable units being connected to a bistable unit body in the inner-layer bistable energy-absorbing structure model and a bistable unit body in the outer-layer bistable energy-absorbing structure model, respectively.

[0011] In an embodiment, the number of the bistable unit bodies in the inner-layer bistable energy-absorbing structure model is one layer, and the number of the bistable unit bodies in the outer-layer bistable energy-absorbing structure model is two layers.

[0012] In an embodiment, the span height of the hyperbolic beam in the outer-layer bistable energy-absorbing structure model is h1, the span height of the hyperbolic beam in the inner-layer bistable energy-absorbing structure model is h2, the span height of the half-bistable unit is h3, and the relationship between h1, h2 and h3 is 2h1 = h2 + h3.

[0013] In an embodiment, the thickness of the hyperbolic beam in the outer-layer bistable energy-absorbing structure model is t1, the thickness of the hyperbolic beam in the inner-layer bistable energy-absorbing structure model is t2, and the thickness of the hyperbolic beam in the half-bistable unit is t3; wherein Q = h / t, Q is the energy absorbed by the repeatable energy-absorbing structure during the impact resistance process, and when 0.6mm < t1 = t2 = t3 = t < 1.6mm, 6mm < h1 = h2 = h3 = h < 9mm, Q > 3.75, the energy-absorbing characteristics of the repeatable energy-absorbing structure with multi-stable characteristics during the impact resistance process are significantly enhanced.

[0014] In an embodiment, two ends of each of a part of the half-bistable units are connected to the upper circumferential end of the inner-layer bistable energy-absorbing structure model and the upper circumferential end of the outer-layer bistable energy-absorbing structure model, respectively, two ends of each of another part of the half-bistable units are connected to the lower circumferential end of the inner-layer bistable energy-absorbing structure model and the lower circumferential end of the outer-layer bistable energy-absorbing structure model, respectively, and N is not less than 6.

[0015] In an embodiment, the cross-sectional shape of the inner-layer bistable energy-absorbing structure model and the outer-layer bistable energy-absorbing structure model is circular or polygonal or elliptical or corrugated or irregular shape composed of arcs and curves.

[0016] In an embodiment, the repeatable energy-absorbing structure can be sequentially stacked along the height direction to form an array of repeatable energy-absorbing structures.

[0017] In an embodiment, the cross-sectional shape of the inner-layer bistable energy-absorbing structure model and the outer-layer bistable energy-absorbing structure model is circular, and the arc length between the same end of each two adjacent half bistable units in the N number of half bistable units on the circumferential end of the inner-layer bistable energy-absorbing structure model is equal; and / or the arc length between the same end of each two adjacent half bistable units in the N number of half bistable units on the circumferential end of the outer-layer bistable energy-absorbing structure model is equal.

[0018] In an embodiment, the hyperbolic beam is a cosine curved beam, a sine curved beam, a trapezoidal curved beam, an elliptical curved beam, a parabolic curved beam, or a wave-shaped curved beam formed by a plurality of curved lines in series.

[0019] In an embodiment, the bistable structure is arranged in parallel by a plurality of the unit cells.

[0020] In the same layer of the bistable structure, the head end of the crossbar coupled to the hyperbolic beam in each unit cell is connected to the tail end of the corresponding crossbar in the adjacent unit cell.

[0021] Meanwhile, the surface of the side rod in each unit cell is connected to the surface of the side rod in the adjacent unit cell, or the side rod in each unit cell is the same side rod as the side rod in the adjacent unit cell.

[0022] Between the upper and lower adjacent layers of the bistable structure, the surface of the crossbar in each unit cell is connected to the surface of the crossbar in the adjacent unit cell, or the crossbar in each unit cell is the same crossbar as the crossbar in the adjacent unit cell.

[0023] The multi-stable repeatable energy-absorbing structure provided by the present application has the following advantages: the outer-layer bistable energy-absorbing structure model and the inner-layer bistable energy-absorbing structure model are nested to form a repeatable energy-absorbing structure with a cross-sectional shape of concentric rings, and the outer-layer bistable energy-absorbing structure model and the inner-layer bistable energy-absorbing structure model are connected by half bistable units (all of the outer-layer bistable energy-absorbing structure model, the inner-layer bistable energy-absorbing structure model, and the half bistable units have bistable characteristics). The repeatable energy-absorbing structure has multi-stable characteristics, and its energy-absorbing characteristics are significantly enhanced (compared to traditional structures) during the process of resisting impact due to the multi-stage elastic buckling transition. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The structure diagram of the unit cell in an embodiment of the present application;

[0025] Figure 2 The structure diagram of the unit cell in an embodiment of the present application; Figure 1Front view of a single cell;

[0026] Figure 3 Structure diagram of a double-stable energy-absorbing structure model in an embodiment of the present application;

[0027] Figure 4 Structure diagram of a double-stable energy-absorbing structure model in an embodiment of the present application;

[0028] Figure 5 Structure diagram of a double-stable energy-absorbing structure model in an embodiment of the present application; Figure 1 Structure diagram of a semi-double-stable cell in an embodiment of the present application;

[0029] Figure 6 Structure diagram of a repeatable energy-absorbing structure in an embodiment of the present application;

[0030] Figure 7 Structure diagram of a plurality of repeatable energy-absorbing structures in a stacked state to constitute a negative stiffness metamaterial in an embodiment of the present application;

[0031] Figure 8 Structure diagram of a repeatable energy-absorbing structure in a fitted state with an adjacent repeatable energy-absorbing structure when the repeatable energy-absorbing structure is deformed in an embodiment of the present application;

[0032] Figure 9 Displacement-force diagram of a semi-double-stable cell in an embodiment of the present application;

[0033] Figure 10 Graph of the energy absorbed by a repeatable energy-absorbing structure when the number N of semi-double-stable cells in the circumferential end portion of the repeatable energy-absorbing structure takes different values in an embodiment of the present application;

[0034] Figure 11 Displacement-force diagram of a repeatable energy-absorbing structure when the number N of semi-double-stable cells in the circumferential end portion of the repeatable energy-absorbing structure takes different values in an embodiment of the present application;

[0035] Figure 12 Displacement-force diagram of a repeatable energy-absorbing structure when the thickness t of a double-stable cosine beam single cell takes different values in an embodiment of the present application;

[0036] Figure 13 Displacement-force diagram of a repeatable energy-absorbing structure when h1, h2 and h3 take different values in an embodiment of the present application;

[0037] Figure 14 Graph of the energy absorbed by a repeatable energy-absorbing structure when the thickness t of a double-stable cosine beam single cell takes different values in an embodiment of the present application, when L, h1, h2 and h3 are determined values.

[0038] Reference numerals: 1, repeatable energy-absorbing structure;

[0039] 2. outer layer bistable energy-absorbing structure model; 20, bistable unit; 200, unit cell; 2000, crossbar; 2001, side bar; 2002, connecting bar; 2003, hyperbolic beam;

[0040] 3. inner layer bistable energy-absorbing structure model; 4, semi-bistable unit. DETAILED DESCRIPTION

[0041] The technical solutions in the present application will be described in detail below with reference to the drawings. In the description of the embodiments of the present application, unless otherwise specified, " / " represents the meaning of or, for example, A / B can represent A or B: "and / or" in the text only describes the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which means that there are three cases of A alone, A and B together, and B alone. In addition, in the description of the embodiments of the present application, "multiple" means two or more than two. The following terms "first" and "second" are only for descriptive purposes, and cannot be understood as implying or suggesting relative importance or implicitly indicating the number of indicated technical features. Therefore, the features defined with "first" and "second" can explicitly or implicitly include one or more features.

[0042] Energy-absorbing materials are widely used in daily production and life, for example, anti-collision, protection of personnel and precision instruments, etc. At present, researchers have created effective energy-absorbing materials by studying various energy-absorbing ways, including using the wake-up deformation in metal, the fragmentation of ceramics, and viscous materials, etc. But the foregoing energy-absorbing ways all have problems such as being unable to be repeated or the energy-absorbing characteristics being affected by the loading and unloading rates. For example, the automobile bumper or the light bicycle helmet is based on the destructive deformation of foam or metal structure to absorb impact mechanical energy. Obviously, the way of absorbing impact mechanical energy by the destructive deformation of foam or metal structure can only be used once. While some energy-absorbing materials can be reused, their performance of absorbing mechanical energy mainly depends on the length of time of loading and unloading (or depends on the loading and unloading rates). For example, the rubber sole and the gasoline engine piston shock absorber absorb mechanical energy by using viscoelasticity.

[0043] Reference Figures 1-6 The present application provides a multi-stable-based repeatable energy-absorbing structure (such as Figure 7As shown, the negative stiffness metamaterial is composed of a number of repeatable energy-absorbing structure arrays stacked by repeatable energy-absorbing structures, which is one of the important branches of the multi-stable mechanical metamaterial (a kind of artificial structural material, whose energy-absorbing characteristics depend on the structure rather than the material properties of its components), and has very good energy-absorbing characteristics, such as storing the external force work in the form of elastic deformation energy in the repeatable energy-absorbing structure without irreversible damage. The multi-stable negative stiffness metamaterial has good energy-absorbing characteristics without the influence of loading and unloading rates, and can provide good cushioning protection performance to effectively avoid secondary injury, and then restore to the initial state after the application of the reverse external load to realize recycling. That is, the elastic buckling step effect (a phenomenon caused by the instability of the elastic stage, in the aforementioned unstable stage, when the applied external force reaches the critical level, the material structure will instantaneously jump from one buckling mode to another buckling mode, for example, the process of the Euler rod structure jumping from its first-order mode to the second-order or other high-order mode. When the material structure experiences buckling mode step, it will experience other equilibrium states of the material structure, and the equilibrium states here include stable equilibrium states and unstable equilibrium states. When the loading or unloading mechanical energy is stopped, the material structure may stay in the new stable equilibrium state and cannot automatically recover to the original state. Obviously, in this process, the mechanical energy acting on the material structure is captured in the form of elastic deformation, and this mechanical energy capturing mechanism only depends on the reversible change of the geometry of the repeatable energy-absorbing structure design structure), realizing the mechanical energy dissipation of the repeatable energy-absorbing structure in the loading and unloading process.

[0044] The repeatable energy absorption structure 1 comprises an inner layer bistable energy absorption structure model 3, an outer layer bistable energy absorption structure model 2 and N half-bistable units 4 (N is a positive integer). The inner layer bistable energy absorption structure model 3 comprises at least one bistable unit body 20, and the outer layer bistable energy absorption structure model 2 comprises at least two bistable unit bodies 20. The inner layer bistable energy absorption structure model 3 is sleeved in the inner layer of the outer layer bistable energy absorption structure model 2 (detailed below), and the upper circumferential end of the outer layer bistable energy absorption structure model 2 is connected to the upper circumferential end of the inner layer bistable energy absorption structure model 3, and the lower circumferential end of the outer layer bistable energy absorption structure model 2 is connected to the lower circumferential end of the inner layer bistable energy absorption structure model 3 through the half-bistable unit 4. In other words, the half-bistable unit 4 is fixed to the upper and lower circumferential ends of the outer layer bistable energy absorption structure model 2 and the upper and lower circumferential ends of the inner layer bistable energy absorption structure model 3. In the embodiment, the number of bistable unit bodies 20 in the inner layer bistable energy absorption structure model 3 is one, and the number of bistable unit bodies 20 in the outer layer bistable energy absorption structure model 2 is two, which are stacked up and down. Of course, in other embodiments, the number of bistable unit bodies 20 in the inner layer bistable energy absorption structure model 3 is not limited, and the number of bistable unit bodies 20 in the outer layer bistable energy absorption structure model 2 is also not limited.

[0045] It should be noted that the cross-sectional shape of the inner layer bistable energy absorption structure model 3 and the outer layer bistable energy absorption structure model 2 can be circular or polygonal or oval or corrugated or irregular shape composed of arc lines and curves or segmented hollow rod or frame structure formed by periodic unit splicing. In the embodiment, in order to ensure that the repeatable energy absorption structure is uniformly stressed, the cross-sectional shape of the inner layer bistable energy absorption structure model 3 and the outer layer bistable energy absorption structure model 2 is circular.

[0046] It is also necessary to point out that in order to form a stable space support when the two ends of the semi-dual stable unit 4 are fixed to the inner layer dual stable energy absorption structure model 3 and the outer layer dual stable energy absorption structure model 2 respectively, the number of the semi-dual stable units 4 at the upper circumferential end of the repeatable energy absorption structure 1 is equal to the number of the semi-dual stable units 4 at the lower circumferential end of the repeatable energy absorption structure 1, and both are not less than 3. In a specific embodiment, the number of the semi-dual stable units 4 at the upper circumferential end of the repeatable energy absorption structure 1 can be equal to the number of the semi-dual stable units 4 at the lower circumferential end of the repeatable energy absorption structure 1, both of which can be 4. According to the simulation of the repeatable energy absorption structure in the impact resistance process, when the repeatable energy absorption structure 1 is subjected to an external force from top to bottom (or from bottom to top), the semi-dual stable units 4 at the upper circumferential end of the repeatable energy absorption structure 1 will elastically buckle, while the semi-dual stable units 4 at the lower circumferential end of the repeatable energy absorption structure 1 will not elastically buckle. Therefore, in the following specific embodiments, only the number of the semi-dual stable units 4 at the upper circumferential end of the repeatable energy absorption structure 1 is changed, while the number of the semi-dual stable units 4 at the lower circumferential end of the repeatable energy absorption structure 1 remains unchanged. Obviously, in other specific embodiments, the number of the semi-dual stable units 4 at the upper circumferential end of the repeatable energy absorption structure 1 can be different from the number of the semi-dual stable units 4 at the lower circumferential end of the repeatable energy absorption structure 1, and both can be other values, for example, the number of the semi-dual stable units 4 at the upper circumferential end of the repeatable energy absorption structure 1 can be 5, while the number of the semi-dual stable units 4 at the lower circumferential end of the repeatable energy absorption structure 1 can be 3.

[0047] As shown in Figure 8 Obviously, as mentioned above, since the negative stiffness material is stacked by a plurality of repeatable energy absorption structures 1, and when the repeatable energy absorption structure 1 elastically buckles in the impact resistance process, the upper circumferential end of the repeatable energy absorption structure 1 forms a protrusion embedded in the groove of the lower circumferential end of the adjacent repeatable energy absorption structure 1, so as to ensure the rationality of the elastic buckling of the negative stiffness material.

[0048] It can be understood that the cross-sectional shape of the inner layer dual stable energy absorption structure model 3 and the outer layer dual stable energy absorption structure model 2 is circular, and the arc length value between the same end of each adjacent two semi-dual stable units 4 on the circumferential end of the inner layer dual stable energy absorption structure model 3 is equal; and / or the arc length value between the same end of each adjacent two semi-dual stable units 4 on the circumferential end of the outer layer dual stable energy absorption structure model 2 is equal.

[0049] Specifically, the bistable unit 20 can be formed by a plurality of cells 200 in an array. Each cell 200 includes a hyperbolic beam 2003, a connecting rod 2002, two parallel transverse rods 2000, and two side rods 2001. The two ends of one transverse rod 2000 are fixed to the tail ends of the two side rods 2001, respectively, and the two ends of the hyperbolic beam 2003 are fixed to the head ends of the two side rods 2001, respectively, and are fixed to the other transverse rod 2000 through the connecting rod 2002. It can be understood that the two ends of the connecting rod 2002 are fixed to the middle of the other transverse rod 2000 and the middle of the hyperbolic beam 2003, respectively. As shown in FIG. 2, it is obvious that the semi-bistable unit 4 is symmetrically divided from the complete cell 200. Figure 5

[0050] Obviously, in order to ensure that the cell 200 in the repeatable energy absorption structure has a supporting force while being able to have a buckling jump under the action of an external force, the stiffness of the connecting rod 2002, the transverse rod 2000, and the side rod 2001 is equal and greater than the stiffness of the hyperbolic beam 2003.

[0051] It can be understood that, as described above, in the specific embodiment, in the same layer bistable unit 20, the head end of the transverse rod 2000 coupled to the hyperbolic beam 2003 in each cell 200 is connected to the tail end of the corresponding transverse rod 2000 in the adjacent cell 200; at the same time, the surface of one side rod 2001 in each cell 200 is in contact with the surface of the other side rod 2001 in the adjacent cell 200; or, one side rod 2001 in each cell 200 is the same side rod 2001 as the other side rod 2001 in the adjacent cell 200. Between the upper and lower adjacent two layers of bistable units 20, the surface of the upper transverse rod 2000 in each bistable unit 20 is in contact with the surface of the lower transverse rod 2000 (or the other transverse rod 2000) in the adjacent bistable unit 20; or, the upper transverse rod 2000 in each bistable unit 20 is the same transverse rod 2000 as the lower transverse rod 2000 in the adjacent bistable unit 20. In other words, the upper transverse rod 2000 in each bistable unit 20 shares the same transverse rod 2000 as the lower transverse rod 2000 in the adjacent bistable unit 20.

[0052] The hyperbolic beam has a span-to-depth ratio of h, and as h increases, the effective crushing distance of the repeatable energy absorption structure is lengthened. Compared with the hyperbolic beam with a small span-to-depth ratio, the hyperbolic beam with a large span-to-depth ratio can generate a larger plastic deformation space, thereby prolonging the buffering time of the repeatable energy absorption structure 1 during the impact resistance process, and facilitating the smooth dispersion of the impact force on the repeatable energy absorption structure 1.

[0053] ​It should be further explained that in the present embodiment, the materials of the connecting rod 2002, the cross rod 2000 and the side rod 2001 can be PLA materials, and the material of the hyperbolic beam 2003 can be a TPU material.

[0054] Referring to the disclosure document with the disclosure number CN117212392A and the name of a sudden elastic jump level hyperbolic beam multi-stable metamaterial repeatable energy absorption structure, it can be known that the energy absorption characteristics of the bistable unit body 20 in the impact resistance process are stronger than those of the unit cell 200 in the impact resistance process, and in order to further increase the energy absorption characteristics of the repeatable energy absorption unit in the impact resistance process, the inventor designs the repeatable energy absorption structure.

[0055] Embodiment 1

[0056] The following describes in detail how the foregoing structure enhances the energy absorption characteristics in the impact resistance process (compared to the unit cell 200). The design method of the multi-stable repeatable energy absorption structure is as follows:

[0057] Referring to the foregoing, the repeatable energy absorption structure 1 is composed of mutually nested inner and outer layer bistable energy absorption structure models 2 and N half-bistable units 4 lapped between the two, and the inner and outer layer bistable energy absorption structure models 2 and the half-bistable units 4 are both constructed based on bistable cosine beam unit cells. Referring to the foregoing Figure 2 Each bistable cosine beam unit cell (that is, the unit cell 200, hereinafter referred to as a bistable cosine beam unit cell) has a cosine curve shape in geometry. The bistable cosine beam unit cell is now defined in geometry,

[0058]

[0059] Wherein, ω(x) is the height of the bistable cosine beam unit cell along the y-axis, x is the span of the bistable cosine beam unit cell along the x-axis, h is the mid-span height of the bistable cosine beam unit cell, and L is the span of the bistable cosine beam unit cell.

[0060] As Figure 9 shown, through abaqus / Standard simulation analysis, the Q value in the force-position diagram of the half-bistable unit 4 is significantly greater than 2.31, and the half-bistable unit 4 exhibits bistable characteristics in this range, that is, the half-bistable unit 4 can form two stable equilibrium states when subjected to an impact external force, thereby significantly improving the energy absorption characteristics of the half-bistable unit 4 in the impact resistance process; define the geometric constant:

[0061] Q = h / t;

[0062] Wherein, Q is the energy absorbed by the half-bistable unit in the impact resistance process, h is the mid-span height of the half-bistable unit 4, and t is the thickness of the half-bistable unit 4.

[0063] At this time, the outer bistable energy-absorbing structure model 2, the inner bistable energy-absorbing structure model 3, and the semi-bistable unit 4 all have bistable characteristics. Therefore, the repeatable energy-absorbing structure 1 composed of the outer bistable energy-absorbing structure model 2, the inner bistable energy-absorbing structure model 3, and the semi-bistable unit 4 and reasonably arranged has multi-stable characteristics.

[0064] According to the impact resistance performance and energy-absorbing characteristics required for the impact-resistant product made of the material with the repeatable energy-absorbing structure 1, the following physical quantities can be adjusted during the design of the repeatable energy-absorbing structure 1 to ensure that the repeatable energy-absorbing structure 1 always has bistable characteristics:

[0065] 1) The number N of semi-bistable units 4; during the process where the number N of semi-bistable units 4 at the upper circumferential end of the repeatable energy-absorbing structure 1 changes from 3 to 6, referring to Figure 10 and Figure 11 , the structure of the repeatable energy-absorbing structure 1 always has bistable characteristics, and the energy-absorbing characteristics of the structure of the repeatable energy-absorbing structure 1 during the impact resistance process increase with the increase of the N value;

[0066] 2) The thickness t of the bistable cosine beam unit cell; specifically, the thickness of the bistable cosine beam unit cell in the outer bistable energy-absorbing structure model 2 is t1, the thickness of the bistable cosine beam unit cell in the inner bistable energy-absorbing structure model 3 is t2, and the thickness of the semi-bistable unit 4 is t3. When t1 = t2 = t3 = t, as Figure 12 shown, by adjusting the thickness t1 of the bistable cosine beam unit cell to change from 0.6 mm to 2.0 mm, it can be seen from the figure that when 0.6 mm < t1 < 1.6 mm, the structure of the repeatable energy-absorbing structure 1 has bistable characteristics, thereby significantly improving the energy-absorbing characteristics of the structure of the repeatable energy-absorbing structure 1 during the impact resistance process;

[0067] 3) The mid-span height of the bistable cosine beam unit cell in the outer bistable energy-absorbing structure model 2 is h1, the mid-span height of the bistable cosine beam unit cell in the inner bistable energy-absorbing structure model 3 is h2, and the mid-span height of the semi-bistable unit 4 is h3; referring to the foregoing, since the structure of the repeatable energy-absorbing structure 1 is composed of the outer bistable energy-absorbing structure model 2, the inner bistable energy-absorbing structure model 3, and N semi-bistable units 4 whose two ends are respectively lapped on the outer bistable energy-absorbing structure model 2 and the inner bistable energy-absorbing structure model 3. Referring to Figure 13, in order to make the structure of the repeatable energy-absorbing structure 1 have bistable characteristics, thereby significantly improving the energy-absorbing characteristics of the structure of the repeatable energy-absorbing structure 1 in the process of resisting impact. That is, to ensure that the deformation amount of the outer layer bistable energy-absorbing structure model 2 is consistent with the sum of the deformation amounts of the inner layer bistable energy-absorbing structure model 3 and the semi-bistable unit 4, so as to ensure that the outer layer bistable energy-absorbing structure model 2, the inner layer bistable energy-absorbing structure model 3 and the semi-bistable unit reach a stable state at the same time when the repeatable energy-absorbing structure 1 is impacted by external force, so h1, h2 and h3 satisfy the following formula:

[0068] 2h1 = h2 + h3;

[0069] Obviously, if the above relationship is not satisfied, for example, when 2h1 > h2 + h3, it means that the deformation amount of the outer layer bistable energy-absorbing structure model 2 exceeds the sum of the deformation amount of the inner layer bistable energy-absorbing structure model 3 and the deformation amount of the semi-bistable unit 4. In other words, in the process of the repeatable energy-absorbing structure 1 being impacted by external force, when the outer layer bistable energy-absorbing structure model 2 reaches a stable state, the inner layer bistable energy-absorbing structure model 3 and the semi-bistable unit 4 are already in a non-stable state. At this time, the structure of the repeatable energy-absorbing structure 1 will not have a stable state characteristic, and the material having the repeatable energy-absorbing structure 1 will also have a fatigue fracture phenomenon. Preferably, 10mm > h2 > 6mm, 10mm > h3 > 6mm.

[0070] Embodiment 2

[0071] Regarding the physical quantities in the repeatable energy-absorbing structure 1, the formula Q = h / t is satisfied, Q is the energy absorbed by the repeatable energy-absorbing structure 1 in the process of resisting impact, and when 0.6mm < t1 = t2 = t3 = t < 1.6mm, 6mm < h1 = h2 = h3 = h < 9mm, Q > 3.75, the energy-absorbing characteristics of the repeatable energy-absorbing structure with multi-stable state characteristics in the process of resisting impact are significantly enhanced.

[0072] Embodiment 3

[0073] Reference Figure 14 When the mid-span height h1 of the bistable cosine beam cell in the outer layer bistable energy-absorbing structure model 2 is 8mm, the mid-span height h2 of the bistable cosine beam cell in the inner layer bistable energy-absorbing structure model 3 is 10mm, the mid-span height h3 of the semi-bistable unit 4 is 6mm, the span L of the bistable cosine beam cell is 40mm, the X-Y plane outer thickness is 5mm, the Young's modulus E of the material PLA is 2000MPa, and the Poisson's ratio υ is 0.3; the Young's modulus E of the TPU material is 30MPa, and the Poisson's ratio υ is 0.45, in the process of changing the thickness t of the bistable cosine beam cell from 0.6 to 1.6, the repeatable energy-absorbing structure 1 has bistable characteristics, at this time, the energy-absorbing characteristics of the repeatable energy-absorbing structure 1 in the process of resisting impact are significantly enhanced.

[0074] It is to be understood that the present application is described by way of example only, and that modifications or alterations can be made to the features and embodiments described without departing from the spirit and scope of the application. In addition, modifications can be made to the features and embodiments described to accommodate specific situations and materials without departing from the spirit and scope of the application. Accordingly, the application is not limited to the specific embodiments disclosed herein, but rather, the scope of the application includes all embodiments falling within the scope of the claims.

Claims

1. A multi-stable based re-energizable energy absorbing structure comprising a unit cell; wherein, The cell comprises a hyperbolic beam, a connecting rod, two transverse rods parallel to each other, and a side rod; The tail ends of the two side rods are connected to the two ends of one of the transverse rods, and the head ends are connected to the two ends of the hyperbolic beam; the two ends of the connecting rod are fixed to the middle part of the hyperbolic beam and the middle part of the other transverse rod; characterized in that it further comprises: The inner-layer bistable energy-absorbing structure model comprises at least one layer of bistable unit cells formed by M cells; The outer-layer bistable energy-absorbing structure model is arranged outside the inner-layer bistable energy-absorbing structure model and assembled into a repeatable energy-absorbing structure with a concentric ring cross-sectional shape; the outer-layer bistable energy-absorbing structure model comprises at least two layers of bistable unit cells stacked in sequence, and M is a positive integer; The number of the semi-bistable units is N, N is a positive integer, and the two ends of each semi-bistable unit are connected to the bistable unit cells in the inner-layer bistable energy-absorbing structure model and the bistable unit cells in the outer-layer bistable energy-absorbing structure model; The number of the bistable unit cells in the inner-layer bistable energy-absorbing structure model is one layer, and the number of the bistable unit cells in the outer-layer bistable energy-absorbing structure model is two layers; The span-to-depth ratio of the hyperbolic beam in the outer-layer bistable energy-absorbing structure model is h1, the span-to-depth ratio of the hyperbolic beam in the inner-layer bistable energy-absorbing structure model is h2, and the span-to-depth ratio of the semi-bistable unit is h3, and the relationship between h1, h2, and h3 is 2h1=h2+h3; The two ends of each semi-bistable unit in a part of the semi-bistable units are respectively lapped to the upper end of the bistable unit cell in the inner-layer bistable energy-absorbing structure model and the upper end of the bistable unit cell in the outer-layer bistable energy-absorbing structure model; the two ends of each semi-bistable unit in another part of the semi-bistable units are respectively lapped to the lower end of the inner-layer bistable energy-absorbing structure model and the lower end of the outer-layer bistable energy-absorbing structure model, and N is not less than 6; The bistable unit cell is arranged in parallel by a plurality of cells; In the same layer of the bistable unit cells, the head end of the transverse rod in each cell is connected to the tail end of the corresponding transverse rod in the adjacent cell; Meanwhile, the surface of one side rod in each cell is in contact with the surface of another side rod in the adjacent cell; or, one side rod in each cell is the same as another side rod in the adjacent cell; Between the upper and lower adjacent layers of the bistable unit cells, the surface of one transverse rod in each cell is in contact with the surface of another transverse rod in the adjacent cell; or, one transverse rod in each cell is the same as another transverse rod in the adjacent cell.

2. The re-energizable structure of claim 1, wherein, The thickness of the hyperbolic beam in the outer layer bistable energy absorption structure model is t1, the thickness of the hyperbolic beam in the inner layer bistable energy absorption structure model is t2, and the thickness of the hyperbolic beam in the semi-bistable unit is t3; wherein Q = h / t, Q is the energy absorbed by the repeatable energy absorption structure during the impact resistance process, and when 0.6mm < t1= t2= t3=t <1.6mm, 6mm < h1= h2= h3=h <9mm, Q > 3.75, the energy absorption characteristics of the repeatable energy absorption structure with multi-stable characteristics during the impact resistance process are significantly enhanced.

3. The re-energizable structure of claim 1, wherein, The cross-sectional shape of the inner layer bistable energy absorption structure model and the outer layer bistable energy absorption structure model is circular or polygonal or elliptical or corrugated or irregular shape composed of an arc, a curve.

4. The re-energizable structure of claim 1, wherein, The repeatable energy absorption structure can be stacked in sequence along the height direction to form a repeatable energy absorption structure array.

5. The re-energizable structure of claim 1, wherein, The cross-sectional shape of the inner layer bistable energy absorption structure model and the outer layer bistable energy absorption structure model is circular, and the arc length value between the same end of each adjacent two semi-bistable units in N is equal on the circumferential end of the inner layer bistable energy absorption structure model; and / or the arc length value between the same end of each adjacent two semi-bistable units in N is equal on the circumferential end of the outer layer bistable energy absorption structure model.

6. The re-energizable structure of any one of claims 1-5, wherein, The hyperbolic beam is a cosine curve beam or a sine curve beam or a trapezoidal curve beam or an elliptical curve beam or a parabolic section transformed curve beam or a corrugated curve formed by a plurality of curve joints.

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