Multi-stable-state-based repeatable energy absorption structure

Abstract

The invention belongs to the technical field of multistable structures, and particularly relates to a multistable-based repeatable energy absorption structure. The cell comprises a unit cell, the inner-layer bistable energy absorption structure model comprises a bistable unit body; the outer-layer bistable-state energy absorption structure model is arranged on the outer side of the inner-layer bistable-state energy absorption structure model in a sleeving manner; the outer-layer bistable energy absorption structure model comprises a bistable unit body; the two ends of each half bistable unit are connected to the inner-layer bistable energy absorption structure model and the outer-layer bistable energy absorption structure model respectively; according to the invention, the outer-layer bistable-state energy absorption structure model and the inner-layer bistable-state energy absorption structure model which are enclosed by a plurality of unit cells are mutually sleeved to form the repeatable energy absorption structure, and the outer-layer bistable-state energy absorption structure model and the inner-layer bistable-state energy absorption structure model are connected through the semi-bistable-state unit; and the repeatable energy absorption structure is subjected to buckling jump under the action of an impact load, so that the energy absorption characteristic and the impact resistance of the repeatable energy absorption structure are remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of multi-stable structures, and relates to a repeatable energy-absorbing structure based on multi-stable states. Background Art

[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 a gun barrel, etc. Obviously, if the impact process is not controlled, it will not only reduce the service life of the equipment, but also pose a safety hazard.

[0003] Therefore, those skilled in the art have developed a multi-stable structure formed by a bistable unit array to absorb and dissipate energy through jumping buckling during the transition between (multiple) adjacent stable states. Currently, existing multi-stable energy-absorbing structures usually absorb energy in a single buckling jump process, and the amount of energy absorbed is relatively limited.

[0004] Based on this, there is an urgent need to invent a repeatable energy-absorbing structure based on multi-stable states to solve the aforementioned technical problems. Summary of the invention

[0005] The purpose of the present invention is to provide a repeatable energy absorbing structure based on multi-stable state to solve the technical problem that the energy absorbing characteristics of the repeatable energy absorbing structure are poor during impact resistance.

[0006] To achieve the above-mentioned purpose, the present invention provides a specific technical solution of a multi-stable repeatable energy absorption structure as follows: comprising a unit cell; wherein the unit cell comprises a hyperbolic beam, a connecting rod, two mutually parallel cross bars and a side bar;

[0007] The tail ends of the two side rods are respectively connected to the two ends of one of the cross rods, 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 cross rod; and further comprising:

[0008] The inner layer bistable energy absorption structure model comprises at least one layer of bistable unit cells formed by connecting M unit cells in parallel;

[0009] The outer bistable energy absorbing structure model is sleeved on the outer side of the inner bistable energy absorbing structure model and assembled into a repeatable energy absorbing structure with a concentric ring cross-section; the outer bistable energy absorbing structure model includes at least two layers of bistable unit bodies stacked in sequence, upper and lower, and M is a positive integer;

[0010] The number of the semi-bistable units is N, where N is a positive integer, and both ends of each of the semi-bistable units are respectively connected to the bistable unit body in the inner bistable energy absorption structure model and the bistable unit body in the outer bistable energy absorption structure model.

[0011] In a specific embodiment, the number of bistable unit cells in the inner layer bistable energy absorbing structure model is a single layer, and the number of bistable unit cells in the outer layer bistable energy absorbing structure model is two layers.

[0012] In a specific embodiment, the span height of the hyperbolic beam in the outer bistable energy absorption structure model is h1, the span height of the hyperbolic beam in the inner bistable energy absorption structure model is h2, the span height of the semi-bistable unit is h3, and the relationship among h1, h2 and h3 is: 2h1=h2+h3.

[0013] In a specific embodiment, the thickness of the hyperbolic beam in the outer bistable energy absorption structure model is t1, the thickness of the hyperbolic beam in the inner 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 3.75, the energy absorption characteristics of the repeatable energy absorption structure with multi-stable characteristics during the impact resistance process are significantly enhanced.<h1>

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

[0015] In a specific embodiment, the cross-sectional shapes of the inner bistable energy absorbing structure model and the outer bistable energy absorbing structure model are both circular, polygonal, elliptical, corrugated, or irregular shapes composed of arcs and curves.

[0016] In a specific embodiment, the repeatable energy absorbing structures can be stacked in sequence along their own height direction to form a repeatable energy absorbing structure array.

[0017] In a specific embodiment, the cross-sectional shapes of the inner bistable energy absorption structure model and the outer bistable energy absorption structure model are both circular, and at the circumferential end of the inner bistable energy absorption structure model, the arc length between the same ends of each two adjacent semi-bistable units in N are equal; and / or, at the circumferential end of the outer bistable energy absorption structure model, the arc length between the same ends of each two adjacent semi-bistable units in N are equal.

[0018] In a specific embodiment, the hyperbolic beam is a cosine curved beam, a sine curved beam, a trapezoidal curved beam, an elliptical curved beam, a curved beam with a parabolic cross-section transformation, or a curved beam in a corrugated curved form formed by connecting a plurality of curves in series.

[0019] In a specific embodiment, the bistable structure is formed by a plurality of the unit cells arranged in parallel;

[0020] In the bistable structure of the same layer, 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] At the same time, the surface of one side bar in each unit cell is in contact with the surface of another side bar in an adjacent unit cell; or, one side bar in each unit cell is the same side bar as the other side bar in an adjacent unit cell;

[0022] Between the upper and lower adjacent layers of the bistable structures, a surface of a crossbar in each unit cell fits with a surface of another crossbar in an adjacent unit cell; or, a crossbar in each unit cell and another crossbar in an adjacent unit cell are the same crossbar.

[0023] The beneficial effects of the multi-stable repeatable energy absorption structure provided by the present invention are as follows: an outer bistable energy absorption structure model composed of several unit cell arrays and an inner bistable energy absorption structure model are mutually fitted to form a repeatable energy absorption structure with a concentric ring cross-sectional shape, and the outer bistable energy absorption structure model and the inner bistable energy absorption structure model are connected through a semi-bistable unit (the outer bistable energy absorption structure model, the inner bistable energy absorption structure model and the semi-bistable unit all have bistable characteristics), so that the formed repeatable energy absorption structure has multi-stable characteristics, and the repeatable energy absorption structure undergoes multi-stage elastic buckling jumps during the impact resistance process, resulting in significantly enhanced energy absorption characteristics (compared with traditional structures). BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the structure of a unit cell in one embodiment of the present invention;

[0025] Figure 2 For the present invention Figure 1Schematic diagram of the main view of the middle unit cell;

[0026] Figure 3 It is a structural schematic diagram of an inner layer bistable energy absorption structure model in one embodiment of the present invention;

[0027] Figure 4 It is a structural schematic diagram of an outer layer bistable energy absorption structure model in one embodiment of the present invention;

[0028] Figure 5 For the present invention Figure 1 Schematic diagram of the structure of the medium semi-bistable unit;

[0029] Figure 6 It is a schematic structural diagram of a repeatable energy absorbing structure in one embodiment of the present invention;

[0030] Figure 7 It is a schematic structural diagram of a plurality of repeatable energy-absorbing structures constituting a negative stiffness metamaterial in an embodiment of the present invention in a stacked state;

[0031] Figure 8 It is a schematic structural diagram of a repeatable energy absorbing structure in an embodiment of the present invention in which the repeatable energy absorbing structure is in an interlocking state with an adjacent repeatable energy absorbing structure when the repeatable energy absorbing structure is deformed;

[0032] Fig. 9 is a displacement-force diagram of a semi-bistable unit in one embodiment of the present invention;

[0033] Fig.10 A diagram showing changes in the energy value absorbed by the repeatable energy absorbing structure when the number N of the semi-bistable units in the circumferential end of the repeatable energy absorbing structure takes different values ​​in one embodiment of the present invention;

[0034] Fig.11 A displacement-force diagram of the repeatable energy absorbing structure when the number N of the semi-bistable units in the circumferential end of the repeatable energy absorbing structure takes different values ​​in one embodiment of the present invention;

[0035] Fig.12 A displacement-force diagram of a repeatable energy absorbing structure when the thickness t of a bistable cosine beam unit cell takes different values ​​in one embodiment of the present invention;

[0036] Fig.13 is a displacement-force diagram of a repeatable energy absorbing structure when h1, h2 and h3 take different values ​​in one embodiment of the present invention;

[0037] Fig.14 1 is a graph showing changes in the energy absorbed by the repeatable energy-absorbing structure when the thickness t of the bistable cosine beam unit cell takes different values ​​when L, h1, h2 and h3 are certain values ​​in one embodiment of the present invention.

[0038] Reference numerals: 1. Repeatable energy absorbing structure;

[0039] 2. Outer layer bistable energy absorption structure model; 20. Bistable unit body; 200. Unit cell; 2000. Cross bar; 2001. Side bar; 2002. Connecting rod; 2003. Hyperbolic beam;

[0040] 3. Inner layer bistable energy absorption structure model; 4. Semi-bistable unit. DETAILED DESCRIPTION

[0041] The technical solution in the present application will be described clearly and in detail below in conjunction with the accompanying drawings. Among them, in the description of the embodiments of the present application, unless otherwise specified, " / " means or, for example, A / B can mean A or B: "and / or" in the text is only a description of the association relationship of associated objects, indicating that there can be three relationships, such as A and / or B, which can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, in the description of the embodiments of the present application, "multiple" refers to two or more than two. The following terms "first" and "second" are used for descriptive purposes only and cannot be understood as implying or suggesting relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

[0042] Energy-absorbing materials are widely used in daily production and life, for example, to prevent collisions, protect personnel and precision instruments, etc. At present, researchers have created effective energy-absorbing materials by studying a variety of energy-absorbing methods, including the use of wake-up deformation in metals, the fragmentation of ceramics, and viscous materials. However, the aforementioned energy-absorbing methods all have problems such as being unable to be repeated or the energy-absorbing characteristics being affected by the rates of loading and unloading. For example, a car bumper or a light bicycle helmet absorbs impact mechanical energy based on the destructive deformation of a foam or metal structure. Obviously, absorbing impact mechanical energy by destructive deformation of a foam or metal structure can only be used once. Although some energy-absorbing materials can be reused, their performance in absorbing mechanical energy mainly depends on the duration of loading and unloading (or, on the rate of loading and unloading). For example, rubber soles and gasoline engine piston shock absorbers use viscoelasticity to absorb mechanical energy.

[0043] refer to Figure 1-Figure 6 The present invention provides a multi-stable repeatable energy absorption structure (such as Figure 7As shown in the figure, the negative stiffness metamaterial is composed of a repeatable energy absorbing structure array formed by stacking several repeatable energy absorbing structures. As one of the important branches of multi-stable mechanical metamaterials (mechanical metamaterials are artificial structural materials whose energy absorption characteristics depend on the structural composition rather than the material properties of their components), negative stiffness metamaterials have very good energy absorption characteristics. For example, external force work is stored in the repeatable energy absorbing structure in the form of elastic deformation energy without irreversible damage. Multi-stable negative stiffness metamaterials have good energy absorption characteristics without being affected by loading and unloading rates, and can provide good buffering protection to effectively avoid secondary damage. Afterwards, when a reverse external load is applied, it returns to its initial shape for repeated use. That is, by utilizing the elastic buckling step effect (elastic buckling step is a phenomenon caused by the instability of the elastic stage. In the aforementioned unstable stage, when the applied external force reaches a critical level, the material structure will instantly jump from one buckling mode to another buckling mode, for example, the Euler rod structure jumps from its first-order mode to the second-order or other higher-order mode. When the material structure undergoes a buckling modal step, it will experience other equilibrium states of the material structure. The equilibrium states here include stable equilibrium states and unstable equilibrium states. When the loading or unloading of mechanical energy stops, the material structure may remain in the new stable equilibrium state and cannot automatically return 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 capture mechanism only depends on the reversible change of the geometric shape of the design structure of the repeatable energy absorbing structure), the mechanical energy dissipation of the repeatable energy absorbing structure during the reciprocating loading process is realized.

[0044] The repeatable energy absorption structure 1 includes an inner bistable energy absorption structure model 3, an outer bistable energy absorption structure model 2 and N semi-bistable units 4 (N is a positive integer). The inner bistable energy absorption structure model 3 includes at least a single bistable unit body 20, and the outer bistable energy absorption structure model 2 includes at least two bistable unit bodies 20. The inner bistable energy absorption structure model 3 is set inside the outer bistable energy absorption structure model 2 (see below for details), and the upper circumferential end of the outer bistable energy absorption structure model 2 is connected to the upper circumferential end of the inner bistable energy absorption structure model 3, and the lower circumferential end of the outer bistable energy absorption structure model 2 is connected to the lower circumferential end of the inner bistable energy absorption structure model 3 through the semi-bistable unit 4. In other words, the two ends of the semi-bistable unit 4 are respectively fixed to the upper and lower circumferential ends of the outer bistable energy absorbing structure model 2 and the upper and lower circumferential ends of the inner bistable energy absorbing structure model 3. In this specific embodiment, the number of the bistable structure bodies 20 in the inner bistable energy absorbing structure model 3 is single, and the number of the bistable unit bodies 20 in the outer bistable energy absorbing structure model 2 is two, and they are formed by stacking two bistable unit bodies 20 up and down. Of course, in other specific embodiments, the number of the bistable unit bodies 20 in the inner bistable energy absorbing structure model 3 is not limited, and the number of the bistable unit bodies 20 in the outer bistable energy absorbing structure model 2 is also not limited.

[0045] It should be noted that the cross-sectional shapes of the inner bistable energy absorbing structure model 3 and the outer bistable energy absorbing structure model 2 can be circular, polygonal, elliptical, corrugated, or irregular shapes composed of arcs and curves, or segmented hollow rods or frame structures formed by periodic unit splicing. In this specific embodiment, in order to ensure that the repeatable energy absorbing structure is uniformly stressed, the cross-sectional shapes of the inner bistable energy absorbing structure model 3 and the outer bistable energy absorbing structure model 2 are both circular.

[0046] It should also be noted that in order to form a stable spatial support body when the two ends of the semi-bistable unit 4 are respectively fixed to the inner bistable energy absorbing structure model 3 and the outer bistable energy absorbing structure model 2, the number of the semi-bistable units 4 at the upper circumferential end of the repeatable energy absorbing structure 1 is equal to the number of the lower circumferential end and both are not less than 3. In a specific embodiment, the number of the semi-bistable units 4 at the upper circumferential end and the number of the lower circumferential end of the repeatable energy absorbing structure 1 can be 4. According to the simulation of the repeatable energy absorbing structure in the impact resistance process, when the repeatable energy absorbing structure 1 is subjected to an external force from top to bottom (or, from bottom to top), the semi-bistable unit 4 located at the upper circumferential end of the repeatable energy absorbing structure 1 undergoes an elastic buckling step, while the semi-bistable unit 4 located at the lower circumferential end of the repeatable energy absorbing structure 1 does not undergo an elastic buckling step. Therefore, in the following specific embodiments, only the number of the semi-bistable units 4 located at the upper circumferential end of the repeatable energy absorbing structure 1 is changed, while the number of the semi-bistable units 4 located at the lower circumferential end of the repeatable energy absorbing structure 1 remains unchanged. Obviously, in other specific embodiments, the number of the semi-bistable units 4 at the upper circumferential end of the repeatable energy absorbing structure 1 and the number at the lower circumferential end may also be different, and have other values, for example, the number of the semi-bistable units 4 at the upper circumferential end of the repeatable energy absorbing structure 1 is 5, and the number at the lower circumferential end of the repeatable energy absorbing structure 1 is 3.

[0047] like Figure 8 As shown, it is obvious that, referring to the above, since the negative stiffness material is composed of a number of repeatable energy absorbing structures 1 stacked together, and when the repeatable energy absorbing structure 1 undergoes a buckling jump during the impact resistance process, the upper circumferential end of the repeatable energy absorbing structure 1 forms a protrusion that fits into the groove of the lower circumferential end of the adjacent repeatable energy absorbing structure 1, so as to ensure the rationality of the elastic buckling jump of the negative stiffness material.

[0048] It can be understood that the cross-sectional shapes of the inner bistable energy absorption structure model 3 and the outer bistable energy absorption structure model 2 are both circular, and at the circumferential end of the inner bistable energy absorption structure model 3, the arc length values ​​between the same ends of each two adjacent half bistable units 4 in the N are equal; and / or, at the circumferential end of the outer bistable energy absorption structure model 2, the arc length values ​​between the same ends of each two adjacent half bistable units 4 in the N are equal.

[0049] Specifically, the bistable unit body 20 can be a hollow tubular structure formed by a plurality of unit cells 200 in an array. Each unit cell 200 includes a hyperbolic beam 2003, a connecting rod 2002, two parallel horizontal bars 2000 and two side bars 2001. The two ends of a horizontal bar 2000 are respectively fixed to the tails of the two side bars 2001, while the two ends of the hyperbolic beam 2003 are respectively fixed to the head of the two side bars 2001 and fixed to another horizontal bar 2000 through the connecting rod 2002. It can be understood that the two ends of the connecting rod 2002 are respectively fixed to the middle of another horizontal bar 2000 and the middle of the hyperbolic beam 2003. Figure 5 As shown, it is obvious that the semi-bistable unit 4 is formed by symmetrically dividing the complete unit cell 200.

[0050] Obviously, in order to ensure that the unit cell 200 in the repeatable energy absorption structure has supporting force and can also undergo buckling jump under the action of external force, the stiffness of the connecting rod 2002, the cross rod 2000 and the side rod 2001 is equal to and greater than the stiffness of the hyperbolic beam 2003.

[0051] It can be understood that, with reference to the foregoing, in this specific embodiment, in the bistable unit body 20 of the same layer, the head end of the cross bar 2000 coupled to the hyperbolic beam 2003 in each unit cell 200 is engaged with the tail end of the corresponding cross bar 2000 in the adjacent unit cell 200; at the same time, the surface of one side bar 2001 in each unit cell 200 is in contact with the surface of the other side bar 2001 in the adjacent unit cell 200; or, one side bar 2001 in each unit cell 200 and the other side bar 2001 in the adjacent unit cell 200 are the same side bar 2001. Between the upper and lower adjacent layers of bistable unit bodies 20, the surface of the upper crossbar 2000 in each bistable unit body 20 is in contact with the surface of the lower crossbar 2000 (or another crossbar 2000) in the adjacent bistable unit body 20; or, the upper crossbar 2000 in each bistable unit body 20 and the lower crossbar 2000 in the adjacent bistable unit body 20 are the same crossbar 2000. In other words, the upper crossbar 2000 in each bistable unit body 20 and the lower crossbar 2000 in the adjacent bistable unit body 20 share the same crossbar 2000.

[0052] The span height of the hyperbolic beam is h, and as h increases, the effective crushing distance of the repeatable energy absorbing structure increases. Compared with the hyperbolic beam with a small mid-span height value, the hyperbolic beam with a large mid-span height value can produce a larger plastic deformation space, thereby extending the buffering time of the repeatable energy absorbing structure 1 during the impact resistance process, which is conducive to the smooth dispersion of the impact force on the repeatable energy absorbing structure 1.

[0053] It should also be noted that, in this specific embodiment, the material of the connecting rod 2002, the cross rod 2000 and the side rod 2001 can be PLA material, and the material of the hyperbolic beam 2003 can be TPU material.

[0054] Referring to the public document with the publication number CN117212392A, entitled "A sudden-bounce-changing-level hyperbolic-beam multi-stable metamaterial repeatable energy-absorbing structure", it can be seen that the energy absorption characteristics of the bistable unit body 20 during the impact resistance process are stronger than the energy absorption characteristics of the unit cell 200 during the impact resistance process, and in order to further increase the energy absorption characteristics of the repeatable energy absorption unit during the impact resistance process, the inventor designed the repeatable energy-absorbing structure.

[0055] Implementation Method 1

[0056] The following is a detailed description of how the aforementioned structure enhances the energy absorption characteristics during the impact resistance process (compared to the unit cell 200). The design method of the repeatable energy absorption structure based on multi-stable state is as follows:

[0057] Referring to the above, the repeatable energy absorption structure 1 is composed of inner and outer bistable energy absorption structure models 2 nested with each other and N semi-bistable units 4 overlapped therebetween, and the inner and outer bistable energy absorption structure models 2 and the semi-bistable units 4 are all constructed based on bistable cosine beam unit cells. Figure 2 , each bistable cosine beam unit cell (i.e., unit cell 200, hereinafter referred to as bistable cosine beam unit cell) has a cosine curve shape in geometry. Now, the geometric shape of the bistable cosine beam unit cell is defined.

[0058]

[0059] Where 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] like Fig. 9 As shown in the figure, after abaqus / Standard simulation analysis, the Q value in the force-position diagram of the semi-bistable unit 4 is significantly greater than 2.31, and the semi-bistable unit 4 exhibits bistable characteristics within this range, that is, the semi-bistable unit 4 can form two stable equilibrium states when subjected to external impact force, thereby significantly improving the energy absorption characteristics of the semi-bistable unit 4 during the impact resistance process; define the geometric constants:

[0061] Q = h / t;

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

[0063] At this time, the outer bistable energy absorption structure model 2, the inner bistable energy absorption structure model 3, and the semi-bistable unit 4 all have bistable characteristics. Therefore, the reusable energy absorption structure 1 composed of the outer bistable energy absorption structure model 2, the inner bistable energy absorption 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 absorption characteristics required for the impact-resistant product made of the material with the reusable energy absorption structure 1, the following physical quantities can be adjusted during the design of the reusable energy absorption structure 1 to ensure that the reusable energy absorption structure 1 always has bistable characteristics:

[0065] 1) The number N of the semi-bistable units 4; during the process of the number N of the semi-bistable units 4 at the upper circumferential end of the reusable energy absorption structure 1 changing from 3 to 6, referring to Fig.10 and Fig.11 , the structure of the reusable energy absorption structure 1 always has bistable characteristics, and the energy absorption characteristics of the structure of the reusable energy absorption structure 1 during the impact resistance process are enhanced as the value of N increases;

[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 absorption structure model 2 is t1, the thickness of the bistable cosine beam unit cell in the inner bistable energy absorption structure model 3 is t2, and the thickness of the semi-bistable unit 4 is t3. When t1 = t2 = t3 = t, as Fig.12 shown, by adjusting the thickness t1 of the bistable cosine beam unit cell 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 reusable energy absorption structure 1 has bistable characteristics, thereby significantly improving the energy absorption characteristics of the structure of the reusable energy absorption 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 absorption structure model 2 is h1, the mid-span height of the bistable cosine beam unit cell in the inner bistable energy absorption 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 reusable energy absorption structure 1 is composed of the outer bistable energy absorption structure model 2, the inner bistable energy absorption structure model 3, and N semi-bistable units 4 respectively lapped at both ends on the outer bistable energy absorption structure model 2 and the inner bistable energy absorption structure model 3. Referring to Fig.13, in order to make the structure of the repeatable energy absorbing structure 1 have a bistable characteristic, thereby significantly improving the energy absorption characteristics of the structure of the repeatable energy absorbing structure 1 during the impact resistance process. That is to ensure that the sum of the deformation of the outer bistable energy absorbing structure model 2 and the inner bistable energy absorbing structure model 3 and the semi-bistable unit 4 is consistent, so as to ensure that when the repeatable energy absorbing structure 1 is impacted by external force, the outer bistable energy absorbing structure model 2, the inner bistable energy absorbing structure model 3 and the semi-bistable unit simultaneously reach a stable state, 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 of the outer bistable energy absorbing structure model 2 exceeds the sum of the deformation of the inner bistable energy absorbing structure model 3 and the deformation of the semi-bistable unit 4. In other words, when the outer bistable energy absorbing structure model 2 reaches a stable state during the process of the repeatable energy absorbing structure 1 being subjected to external impact force, the inner bistable energy absorbing structure model 3 and the semi-bistable unit 4 are already in an unstable state. At this time, the structure of the repeatable energy absorbing structure 1 will not have a steady-state characteristic, and the material having the repeatable energy absorbing structure 1 will also experience fatigue fracture. Preferably, 10mm>h2>6mm, 10mm>h3>6mm.

[0070] Implementation Method 2

[0071] The physical quantities in the repeatable energy absorbing structure 1 satisfy the formula Q=h / t, where Q is the energy absorbed by the repeatable energy absorbing structure 1 during the impact resistance process and when 0.6 mm <t1=t2=t3=t<1.6mm,6mm 3.75, the energy absorption characteristics of the repeatable energy absorption structure with multi-stable characteristics during the impact resistance process are significantly enhanced.<h1>

[0072] Implementation 3

[0073] refer to Fig.14 , when the mid-span height h1 of the bistable cosine beam unit cell in the outer bistable energy absorbing structure model 2 is 8mm, the mid-span height h2 of the bistable cosine beam unit cell in the inner 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 unit cell is 40mm, the thickness outside the XY plane 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 unit cell from 0.6 to 1.6, the repeatable energy absorbing structure 1 has a bistable characteristic. At this time, the energy absorption characteristics of the repeatable energy absorbing structure 1 in the impact resistance process are significantly enhanced.

[0074] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims

1. A multi-stable repeatable energy-absorbing structure, comprising a unit cell; wherein: The unit cell includes a hyperbolic beam, a connecting rod, two mutually parallel cross bars and a side bar; The tail ends of the two side rods are respectively connected to the two ends of one of the cross rods, 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 cross rod; it is characterized in that it also includes: An inner layer bistable energy absorption structure model comprises at least one layer of bistable structure surrounded by M unit cells; The outer bistable energy absorbing structure model is sleeved on the outer side of the inner bistable energy absorbing structure model and assembled into a repeatable energy absorbing structure with a concentric ring cross-section; the outer bistable energy absorbing structure model includes at least two layers of bistable structures stacked in sequence, upper and lower, and M is a positive integer; The number of the semi-bistable units is N, where N is a positive integer, and both ends of each of the semi-bistable units are respectively connected to the bistable unit body in the inner bistable energy absorption structure model and the bistable unit body in the outer bistable energy absorption structure model.

2. The repeatable energy absorbing structure according to claim 1, characterized in that: The number of bistable unit cells in the inner layer bistable energy absorbing structure model is a single layer, and the number of bistable unit cells in the outer layer bistable energy absorbing structure model is two layers.

3. The repeatable energy absorbing structure according to claim 2, characterized in that: The span height of the hyperbolic beam in the outer bistable energy absorption structure model is h1, the span height of the hyperbolic beam in the inner bistable energy absorption structure model is h2, the span height of the semi-bistable unit is h3, and the relationship among h1, h2 and h3 is: 2h1=h2+h3.

4. The repeatable energy absorbing structure according to claim 3, characterized in that: The thickness of the hyperbolic beam in the outer bistable energy absorption structure model is t1, the thickness of the hyperbolic beam in the inner 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.

5. The repeatable energy absorbing structure according to claim 1, characterized in that: Two ends of each of the semi-bistable units in a part of the semi-bistable units are respectively overlapped with the upper end of the bistable unit body in the inner bistable energy absorption structure model and the upper end of the bistable unit body in the outer bistable energy absorption structure model; two ends of each of the semi-bistable units in another part of the semi-bistable units are respectively overlapped with the lower end of the inner bistable energy absorption structure model and the lower end of the outer bistable energy absorption structure model, and N is not less than 6.

6. The repeatable energy absorbing structure according to claim 1, characterized in that: The cross-sectional shapes of the inner bistable energy absorbing structure model and the outer bistable energy absorbing structure model are both circular, polygonal, elliptical, corrugated, or irregular shapes composed of arcs and curves.

7. The repeatable energy absorbing structure according to claim 1, characterized in that: The repeatable energy absorbing structures can be stacked in sequence along their own height direction to form a repeatable energy absorbing structure array.

8. The repeatable energy absorbing structure according to claim 5, characterized in that: The cross-sectional shapes of the inner bistable energy absorption structure model and the outer bistable energy absorption structure model are both circular, and at the circumferential end of the inner bistable energy absorption structure model, the arc length between the same ends of each two adjacent semi-bistable units in N are equal; and / or, at the circumferential end of the outer bistable energy absorption structure model, the arc length between the same ends of each two adjacent semi-bistable units in N are equal.

9. The repeatable energy absorbing structure according to any one of claims 1 to 8, characterized in that: The hyperbolic beam is a cosine curved beam, a sine curved beam, a trapezoidal curved beam, an elliptical curved beam, a curved beam with a parabolic cross-section transformation, or a curved beam in a corrugated curved form formed by joining multiple curved sections.

10. The repeatable energy absorbing structure according to any one of claims 1 to 8, characterized in that: The bistable unit body is formed by a plurality of the unit cells arranged in parallel; In the bistable unit bodies of the same layer, 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; At the same time, the surface of one side bar in each unit cell is in contact with the surface of another side bar in an adjacent unit cell; or, one side bar in each unit cell is the same side bar as the other side bar in an adjacent unit cell; Between the upper and lower adjacent layers of the bistable unit bodies, a surface of a crossbar in each unit cell fits with a surface of another crossbar in an adjacent unit cell; or, a crossbar in each unit cell and another crossbar in an adjacent unit cell are the same crossbar.

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