CN112582035A - Recoverable six-way buffering energy-absorbing metamaterial and design method thereof - Google Patents
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Abstract
The invention discloses a recoverable six-way buffering energy-absorbing metamaterial and a design method thereof, and relates to the technical field of metamaterials. The metamaterial is formed by periodically arranging the unit cells, the mechanical properties of the metamaterial in all directions can be adjusted by compiling the mechanical properties of the crossed curved beams in the unit cells, the metamaterial is wide in application range and simple to process, can be directly manufactured by using a 3D printing technology, and is convenient to popularize and use on a large scale.
Description
Technical Field
The invention relates to the technical field of metamaterials, in particular to a recoverable six-way buffering energy-absorbing metamaterial and a design method thereof.
Background
"metamaterial" refers to some composite materials that have artificially designed structures and exhibit extraordinary physical properties not possessed by natural materials. "metamaterials" are a new class of materials that have emerged since the 21 st century that possess specific properties not possessed by natural materials, and these properties are derived primarily from artificial, specialized structures. Through the ordered structure design on the key physical scale of the material, the limit of certain natural laws can be broken through, and the extraordinary material with the inherent property exceeding the nature can be obtained.
At present, the existing buffer energy-absorbing structure design mostly utilizes the plastic deformation of structural materials to realize good buffer energy-absorbing effects (such as honeycomb structural materials, automobile anti-collision beams and the like), but the structural materials do not have the characteristic of repeated use, and after bearing one-time impact, the structural materials must be replaced to deal with the next impact working condition. In addition, a mechanical device can also achieve a good buffering effect, for example, a retractable automobile collision buffering energy-absorbing device disclosed in CN2016204327055 mainly uses the deformation of a damping spring to absorb impact energy, but the buffering energy-absorbing device can only achieve single axial buffering basically, has many parts and a complex structure, and is difficult to process and not easy to popularize and use on a large scale.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a recoverable six-way buffering energy-absorbing metamaterial and a design method thereof.
The invention adopts the following technical scheme:
the invention provides a recoverable six-direction buffering energy-absorbing metamaterial which comprises a plurality of identical unit cells which are arranged periodically, wherein each unit cell is composed of a rectangular frame (1), a crossed curved beam (2) and a connecting rod (3), the rectangular frame (1) provides an installation space for the crossed curved beams (2), and the rectangular frame (1) is composed of 10 straight beams; the crossed curved beams (2) are composed of two curved beams (2-1), 6 groups of crossed curved beams (2) are respectively installed on 6 surfaces of the cuboid framework (1), the end parts of the crossed curved beams (2) are fixedly connected with the cuboid framework (1), the connecting rods (3) are fixedly connected with the middle parts of the crossed curved beams (2), the middle parts of the crossed curved beams (2) with different single cells are sequentially connected through the connecting rods (3), and the single cells are connected to form a multi-cell metamaterial structure.
Furthermore, the bending directions of the crossed curved beams (2) arranged in opposite planes of the rectangular frame (1) are the same, and the crossed curved beams (2) in the opposite planes can be overlapped through translation.
Further, the curved beam (2-1) has a buckling step property according to
Constructing the structural shape of the curved beam (2-1); wherein the content of the first and second substances,
the shortest length of a horizontal line is determined by any point on the central line of the single curved beam (2-1) and two end points of the curved beam (2-1), h is the arc height of the curved beam (2-1), x is the distance from a connecting line of the two end points of the curved beam (2-1) to one end point, and l is the span of the single curved beam;
when the ratio of the arc height h of the curved beam (2-1) to the in-plane thickness t is larger than 2.31, the curved beam is bistable, and when the ratio of the arc height h of the curved beam (2-1) to the in-plane thickness t is smaller than 2.31, the curved beam is monostable.
Further, the curved beam (2-1) is monostable.
Further, the rigidity change of the crossed curved beam (2) is divided into three sections: a first positive stiffness section, a negative stiffness section, and a second positive stiffness section.
The invention also provides a design method of the recoverable six-way buffering energy-absorbing metamaterial, which comprises the following steps:
s1: given a cuboid frame (1) of a unit cell and its geometrical dimensions, the cuboid frame (1) provides a mounting surface for mounting a cross curved beam (2);
s2: according to the formula
Drawing the structural shape of a single curved beam (2-1) and defining
Q represents the ratio of the arc height h of a single curved beam (2-1) in the crossed curved beam (2) to the in-plane thickness t of the curved beam (2-1), when Q is larger than 2.31, the designed single curved beam (2-1) is bistable, and when Q is smaller than 2.31, the designed curved beam (2-1) is monostable;
wherein the content of the first and second substances,
the shortest length of a horizontal line is determined by any point on the central line of a single curved beam (2-1) and two end points of the curved beam (2-1), h is the arc height of the curved beam (2-1), x is the distance from a connecting line of the two end points of the curved beam (2-1) to one end point, and l is the effective span of the curved beam (2-1); l is determined by the geometric dimension of the cuboid frame (1);
s3: according to the formula
Estimating the acting force threshold of the curved beam (2-1), and establishing the relation between the acting force threshold of the curved beam (2-1) and the structural parameters I, h and l of the curved beam (2-1), wherein ftopThe threshold value of the acting force of the curved beam (2-1), E is the elastic modulus of the material, I is the inertia moment of a single curved beam, and the two curved beams (2-1) are arranged in a crossed manner to form a crossed curved beam (2);
s4: constructing a single cell, wherein the crossed curved beams (2) are arranged in 6 planes of the rectangular frame (1), and in the rectangular frame (1) of the single cell, the bending directions of the crossed curved beams (2) arranged in the opposite mounting planes of the rectangular frame (1) are consistent;
s5: constructing a metamaterial, sequentially connecting the middle parts of the crossed curved beams (2) of different unit cells end to end through a connecting rod (3), connecting a plurality of unit cells to form a multi-cell metamaterial structure, processing the metamaterial by utilizing a 3D printing technology, taking three mutually perpendicular edges in the unit cell structure as x and y respectively,z three axes, the acting force threshold of the designed and processed metamaterial in any one direction of +/-x, +/-y and +/-z directions passes through a formula Ft＝2n1ftopTo obtain n1For the number of cells connected in parallel in a given direction, FtThe macroscopic acting force threshold value of the metamaterial in any one direction of +/-x, +/-y and +/-z is estimated.
The technical principle of the invention is as follows: the cross curved beams are arranged in six mounting surfaces of the rectangular frame, the end parts of the cross curved beams are fixedly connected with the rectangular frame, the bending directions of the cross curved beams arranged in the opposite mounting surfaces are consistent, two groups of curved beams arranged in the opposite surfaces can be overlapped after translation, then the middle parts of the cross curved beams of different unit cells are connected by using connecting rods to form a multi-cell metamaterial structure, three mutually perpendicular edges in the unit cell structure are respectively used as an x axis, a y axis and a z axis, and the energy absorption and buffering in +/-x, +/-y and +/-z directions can be realized by depending on the buckling step property of the curved beams and the reasonable design of the unit cells. The transmission path of the force in the unit cell is a connecting block, a crossed curved beam in a side mounting surface, a cuboid frame, a crossed curved beam in an opposite mounting surface and another connecting block, the acting force acting on the unit cell is subjected to deformation buffering of two groups of crossed curved beams from input to output to absorb energy, and after the absorbed energy is dissipated, the unit cell structure has good restorability and is convenient to reuse. The arrangement forms of the unit cell structures in the directions of the x axis, the y axis and the z axis are completely the same, so the automatic return buffering energy absorption principle of the y axis and the z axis is the same as that of the x axis. The key of the multi-cell metamaterial performance design is the performance design of a single cell, the mechanical performance of the single cell determines the mechanical performance of the multi-cell metamaterial structure, the single cell has buffering and energy absorption in the directions of +/-x, +/-y and +/-z, and the multi-cell metamaterial formed by periodically arranging the single cell also has buffering and energy absorption capacity in the directions of +/-x, +/-y and +/-z.
Compared with the prior art, the invention has the advantages and beneficial effects that:
1. the invention breaks through the limitation of the traditional buffering energy-absorbing design, innovatively uses the crossed curved beam with buckling step property, and successfully constructs the multi-cell metamaterial structure with six-direction buffering energy-absorbing capability and reusability through reasonable design of a single-cell structure. Theoretically, the deformation of the unit cell structure in one axial direction does not affect the deformation in other directions, namely the designed unit cell has the characteristic of a super-elastic material. The multi-cell metamaterial structure formed by the single cells inherits the mechanical property of the single cells and has the characteristic of a super-elastic material, and when the multi-cell metamaterial structure is stressed and loaded in one direction, the multi-cell metamaterial structure cannot cause deformation in other directions.
2. The reversible six-direction buffering energy absorption device disclosed by the invention realizes reversible six-direction buffering energy absorption based on the metamaterial, the related structure is simple, the processing is easy, the 3D printing technology can be directly utilized for manufacturing, related steps are basically completed by a machine, and the mass production can be realized.
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In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a schematic three-dimensional structure of a cell according to an embodiment of the present invention;
FIG. 2 is a front view of a recoverable six-way buffering energy-absorbing metamaterial structure in an embodiment of the present invention;
FIG. 3 is an axial view of a recoverable six-way energy-absorbing metamaterial structure in an embodiment of the present invention;
FIG. 4 is a schematic view of a rectangular parallelepiped frame of a unit cell according to an embodiment of the present invention;
FIG. 5 is a schematic structural view of a cross curved beam of an embodiment of the present invention;
FIG. 6 is a schematic view of the geometry of a curved beam of an embodiment of the present invention;
FIG. 7 is a graph of stiffness versus displacement for a cross curved beam under static load in accordance with an embodiment of the present invention;
FIG. 8 is an acceleration-time response curve of a set of intersecting curved beams under a standard half sine wave shock load in a unit cell according to an embodiment of the present invention;
FIG. 9 is an acceleration-time response curve of two sets of intersecting curved beams arranged in opposite mounting faces of a unit cell under a standard half sine wave impact load in an embodiment of the invention;
the device comprises a rectangular frame 1, a rectangular frame 2, a cross curved beam 3, a connecting rod 2-1 and a curved beam.
Detailed Description
In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that the terms "comprises" and "comprising," and any variations thereof, in the description and claims of the present invention and the above-described drawings, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
"metamaterial" refers to some composite materials that have artificially designed structures and exhibit extraordinary physical properties not possessed by natural materials. The key to the "metamaterials" to exhibit extraordinary physical properties lies in the unit cell design. For the present invention, the key to the unit cell design is the design of the curved beam. Through the reasonably designed curved beam, when the middle part of the curved beam bears impact load, the curved beam with buckling step property can play a role in buffering and energy absorption, and the response peak value is attenuated, so that the aims of reducing impact force and protecting important parts are fulfilled. The steady-state property of the curved beam can be changed by designing the ratio of the arc height to the beam thickness of the curved beam, and the curved beam can be designed to be monostable and bistable.
In the embodiment, the monostable curved beam is used as the optimal embodiment, and after the curved beam with buckling step property experiences one-time impact load, the curved beam has good recovery capability, can recover to an initial configuration and is convenient to reuse. The single curved beam can only buffer and absorb energy for impact load in one direction, and a single cell structure which can buffer and absorb energy in six directions and can recover an initial configuration is designed by reasonably arranging a plurality of curved beams. Furthermore, a multi-cell metamaterial structure can be constructed through periodic arrangement of single-cell structures, the multi-cell metamaterial structure inherits the mechanical property of single cells, the metamaterial macroscopically shows the capacity of buffering and absorbing impact loads in six directions, and after the externally input impact energy is dissipated, the metamaterial has the capacity of recovering the initial configuration.
As shown in FIG. 1, a schematic diagram of a unit cell three-dimensional structure of a recoverable six-way buffering energy-absorbing metamaterial is shown. The unit cell capable of recovering the six-direction buffering and energy-absorbing metamaterial comprises a rectangular frame 1, crossed curved beams 2 and connecting rods 3.
The rectangular frame 1 provides an installation space for the crossed curved beams 2, and the rectangular frame 1 consists of 10 straight beams; the crossed curved beams 2 in the unit cell have the property of buckling step, 6 groups of crossed curved beams 2 are respectively arranged on 6 surfaces of the cuboid framework 1, each crossed curved beam 2 consists of two curved beams 2-1, one group of crossed curved beams 2 are arranged in each installation surface, the end part of each group of crossed curved beams 2 is fixedly connected with the cuboid framework 1, the connecting rod 3 is fixedly connected with the middle part of each crossed curved beam 2, the bending directions of the crossed curved beams 2 arranged in the cuboid framework 1 opposite to the installation surfaces are consistent, the two groups of crossed curved beams 2 arranged in the opposite installation surfaces can be coincided after being translated, and the arrangement form of the two groups of crossed curved beams 2 in the unit cell can realize the same axial positive and negative two-way buffering.
As shown in FIG. 2, a three-dimensional structure diagram of the recoverable six-way buffering energy-absorbing metamaterial is shown. The recoverable six-direction buffering energy-absorbing metamaterial is formed by periodically arranging a plurality of identical unit cells, and is sequentially connected with the middle parts of crossed curved beams 2 of different unit cells through connecting rods 3, so that the unit cells which are periodically arranged are mutually connected to form a multi-cell metamaterial structure. The recoverable six-direction buffering energy-absorbing metamaterial structure can be printed and manufactured by using a 3D printing technology (such as an FDM (fused deposition modeling) process, an SLS (selective laser sintering) process, an SLA (layered structure) process and the like), and the materials can be conventional printing materials with high elongation, such as ABS (acrylonitrile butadiene styrene) plastics, PLA (polylactic acid) plastics, nylon, photosensitive resin and the like.
As shown in fig. 3, it shows an axonometric view of a recoverable six-way energy-absorbing metamaterial three-dimensional structure formed by 3 × 3 × 3 unit cells. Each unit cell can be connected to the surrounding six unit cells by means of six connecting rods 3 at the most.
As shown in fig. 4, a schematic view of the structure of a rectangular parallelepiped frame 1 of a unit cell is shown. 12 straight beams are spliced into a cuboid frame 1, 6 installation surfaces are built, and crossed curved beams 2 are conveniently arranged in the installation surfaces.
As shown in fig. 5, there is shown a set of intersecting curved beams 2, the intersecting curved beam 2 being formed by two curved beams 2-1 intersecting.
As shown in fig. 6, which shows a single curved beam 2-1 constituting the intersecting curved beam 2. The structural design of the curved beam 2-1 is the key of single cell performance design. In fig. 6, the ratio of the arc height h to the beam thickness t of a single curved beam 2-1 is Q, in this embodiment, when Q is less than or equal to 2.31, the curved beam 2-1 is monostable, and when Q is greater than 2.31, the curved beam 2-1 is bistable, where l is the effective span of the curved beam 2-1, b is the out-of-plane thickness of the curved beam, the span l and the out-of-plane thickness b of the curved beam 2-1 do not affect the steady-state property of the curved beam 2-1, h is the arc height of the curved beam 2-1, and t represents the in-plane thickness of the curved beam 2-1.
In this embodiment, the specific structural parameters of a single curved beam are that the thickness t is 0.5mm, the arc height h is 1.15mm, the effective span 1 of the beam is 23.5mm, the out-of-plane thickness b of the curved beam is 2mm, and the ratio Q of the arc height to the beam thickness is 2.3.
In the embodiment of the invention, the limitation of the traditional buffering and energy-absorbing design is broken through, the crossed curved beam with the buckling step property is innovatively used, and the multi-cell metamaterial structure with six-direction buffering and energy-absorbing capacity and reusability is successfully constructed through the reasonable design of the single-cell structure. Theoretically, the deformation of the unit cell structure in one axial direction does not affect the deformation in other directions, namely the designed unit cell has the characteristic of a super-elastic material. The multi-cell metamaterial structure formed by the single cells inherits the mechanical property of the single cells and has the characteristic of a super-elastic material, and when the multi-cell metamaterial structure is stressed and loaded in one direction, the multi-cell metamaterial structure cannot cause deformation in other directions.
The specific steps of the recoverable six-way buffering energy-absorbing metamaterial designed based on the crossed curved beam 2 are described in detail as follows:
s1: given a rectangular parallelepiped frame 1 of a unit cell and its geometrical dimensions, the rectangular parallelepiped frame 1 provides a mounting surface for mounting a crossed curved beam 2;
s2: according to the formula
The structural shape of the curved beam 2-1 is drawn,
q represents the ratio of the arc height h of the curved beam 2-1 to the in-plane thickness t of the curved beam 2-1; when Q is larger than 2.31, the designed single curved beam 2-1 is bistable, and when Q is smaller than 2.31, the designed curved beam 2-1 is monostable;
wherein the content of the first and second substances,
the shortest length of a horizontal line is determined by any point on the central line of the curved beam 2-1 and two end points of the curved beam 2-1, h is the arc height of the curved beam 2-1, x is the distance from one end point on the connecting line of the two end points of the curved beam 2-1, and l is the span of the curved beam 2-1; l is determined by the geometric dimension of the rectangular frame 1;
s3: according to the formula
Estimating the acting force threshold of the curved beam 2-1, establishing the relation between the acting force threshold of the curved beam 2-1 and the structural parameters (I, h and l) of the curved beam 2-1,
wherein f istopThe threshold value of the acting force of the curved beam 2-1 is shown, E is the elastic modulus of the material, I is the inertia moment of a single curved beam, and the two curved beams 2-1 are arranged in a crossed manner to form a crossed curved beam 2;
s4: constructing a single cell, wherein the crossed curved beams 2-1 are arranged in 6 installation surfaces provided by the rectangular frame 1, and in the rectangular frame 1 of the single cell, the bending directions of the crossed curved beams 2 arranged in the opposite installation surfaces of the rectangular frame 1 are consistent;
s5: constructing a metamaterial, sequentially connecting the middle parts of different single-cell cross curved beams 2 through connecting rods 3, connecting a plurality of single cells to form a multi-cell metamaterial structure, processing the metamaterial by using a 3D printing technology, and designing the maximum acting force threshold of the processed metamaterial in any one direction of +/-x, +/-y and +/-z directions according to a formula F by taking three mutually perpendicular edges in the single cells as three axes of x, y and z respectivelyt＝2n1ftopTo obtain n1For the number of cells connected in parallel in a given direction, FtThe macroscopic acting force threshold of the metamaterial in any one direction of +/-x, +/-y and +/-z is estimated.
As shown in fig. 7, which shows a graph of stiffness versus displacement of a curved beam under a displacement load. In simulation calculation, the two ends of the crossed curved beam 2 shown in fig. 5 are fixedly constrained, and a displacement load of 2.6mm is applied to the middle of the crossed curved beam 2, so that a rigidity-displacement change curve of the crossed curved beam 2 is obtained as shown in fig. 6, it can be seen that the rigidity of the curved beam 2-1 under the static load is changed in three sections, the rigidity of the curved beam 2-1 during initial loading is a positive value, a negative rigidity section appears along with the increase of the displacement load, and finally the rigidity is changed into the positive value along with the further increase of the displacement load, a positive rigidity section appears, and the negative rigidity section of the curved beam 2-1 enables the curved beam to have good buffering performance.
As shown in fig. 8, which shows the acceleration-time response curve of a cross curved beam 2 arranged in one mounting plane of a unit cell under a standard half sine wave shock load. In the simulation calculation, a total of 0.06kg mass point was added to the end portions of the intersecting curved beam 2, and an amplitude of 40m/s was applied to the center portion of the intersecting curved beam 22The output acceleration after being buffered by a group of crossed curved beams 2 in the simulation result is extracted. The solid line in FIG. 8 indicates an applied amplitude of 40m/s2The dotted line represents the acceleration response curve of the input impact load output after being attenuated by a group of crossed curved beams 2 in a unit cell, and the curve is output from the graph of fig. 8Compared with the input acceleration curve, the impact peak value appearing in the response curve for the first time is obviously reduced, the impact transmission rate is almost 0.5, but an amplified impact peak value appears in the opposite direction, which shows that the curved beam 2 arranged in one mounting surface can only buffer the impact load in one direction. The curved beams 2 in all mounting surfaces in this embodiment have the same properties, and furthermore the material in the simulation calculation is nylon, since the impact load has a short action time, the damping of the material is not considered here.
As shown in fig. 9, which shows the acceleration-time response curves of two sets of intersecting curved beams 2 arranged in opposite mounting faces of a unit cell under a standard half sine wave shock load. In the simulation calculation, a total of 0.06kg mass point was added to the end portions of the intersecting curved beam 2, and an amplitude of 40m/s was applied to the center portion of the intersecting curved beam 22The response acceleration of the output end in the simulation result is extracted. The solid line in FIG. 9 indicates that the applied amplitude is 4X 104mm/s2The dotted line represents a response acceleration curve output after the input impact load is attenuated by the two groups of crossed curved beams 2 arranged in the opposite mounting surface of the single cell, and the output response acceleration curve obtained from fig. 9 has an output acceleration peak value obviously reduced and an impact transfer rate almost reaches 0.5, which shows that the two groups of crossed curved beams 2 arranged in the opposite mounting surface of the single cell can realize bidirectional buffering. In the embodiment, the curved beams arranged in each axial direction of the unit cell have buckling step property, and the arrangement form of the crossed curved beams in each axial direction is the same, so that each axial direction of the unit cell has bidirectional buffering capacity. In addition, the material in the simulation calculation is nylon, and the damping of the material is not considered here because the action time of the impact load is short.
In the embodiment of the invention, the recoverable six-way buffering energy absorption is realized based on the metamaterial, the related structure is simple, the processing is easy, the 3D printing technology can be directly utilized for manufacturing, the related steps are basically completed by a machine, and the mass production can be realized.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (6)
1. The recoverable six-direction buffering energy-absorbing metamaterial is characterized by comprising a plurality of identical unit cells which are arranged periodically, wherein each unit cell is composed of a rectangular frame (1), a crossed curved beam (2) and a connecting rod (3), the rectangular frame (1) provides an installation space for the crossed curved beams (2), and the rectangular frame (1) is composed of 10 straight beams; the crossed curved beams (2) are composed of two curved beams (2-1), 6 groups of crossed curved beams (2) are respectively installed on 6 surfaces of the cuboid framework (1), the end parts of the crossed curved beams (2) are fixedly connected with the cuboid framework (1), the connecting rods (3) are fixedly connected with the middle parts of the crossed curved beams (2), the middle parts of the crossed curved beams (2) with different single cells are sequentially connected through the connecting rods (3), and the single cells are connected to form a multi-cell metamaterial structure.
2. A recoverable six-way buffering energy absorbing metamaterial according to claim 1, wherein the cross curved beams (2) arranged in opposite planes of the rectangular parallelepiped frame (1) have the same bending direction, and the cross curved beams (2) in the opposite planes can be overlapped through translation.
3. A recoverable six-way buffer energy absorbing metamaterial according to claim 1, wherein the curved beams (2-1) have the property of a buckling step according to
Constructing the structural shape of the curved beam (2-1); wherein the content of the first and second substances,
is arranged in a single curved beam (2-1)The shortest length of a horizontal line is determined by any point on the center line and two end points of the curved beam (2-1), h is the arc height of the curved beam (2-1), x is the distance between the connecting line of the two end points of the curved beam (2-1) and one end point, and l is the span of a single curved beam;
when the ratio of the arc height h of the curved beam (2-1) to the in-plane thickness t is larger than 2.31, the curved beam is bistable, and when the ratio of the arc height h of the curved beam (2-1) to the in-plane thickness t is smaller than 2.31, the curved beam is monostable.
4. A recoverable six-way energy-absorbing metamaterial according to claim 3, wherein the curved beam (2-1) is monostable.
5. A recoverable six-way energy-absorbing metamaterial according to claim 3, wherein the variation in stiffness of the intersecting curved beams (2) is divided into three sections: a first positive stiffness section, a negative stiffness section, and a second positive stiffness section.
6. A design method of a recoverable six-way buffering energy-absorbing metamaterial according to any one of claims 1 to 5, wherein the design method comprises the following steps:
s1: given a cuboid frame (1) of a unit cell and its geometrical dimensions, the cuboid frame (1) provides a mounting surface for mounting a cross curved beam (2);
s2: according to the formula
Drawing the structural shape of a single curved beam (2-1) and defining
Q represents the ratio of the arc height h of a single curved beam (2-1) in the crossed curved beam (2) to the in-plane thickness t of the curved beam (2-1), when Q is larger than 2.31, the designed single curved beam (2-1) is bistable, and when Q is smaller than 2.31, the designed curved beam (2-1) is monostable;
wherein the content of the first and second substances,
the shortest length of a horizontal line is determined by any point on the central line of a single curved beam (2-1) and two end points of the curved beam (2-1), h is the arc height of the curved beam (2-1), x is the distance from a connecting line of the two end points of the curved beam (2-1) to one end point, and l is the effective span of the curved beam (2-1); l is determined by the geometric dimension of the cuboid frame (1);
s3: according to the formula
Estimating the acting force threshold of the curved beam (2-1), and establishing the relation between the acting force threshold of the curved beam (2-1) and the structural parameters I, h and l of the curved beam (2-1), wherein ftopThe threshold value of the acting force of the curved beam (2-1), E is the elastic modulus of the material, I is the inertia moment of a single curved beam, and the two curved beams (2-1) are arranged in a crossed manner to form a crossed curved beam (2);
s4: constructing a single cell, wherein the crossed curved beams (2) are arranged in 6 planes of the rectangular frame (1), and in the rectangular frame (1) of the single cell, the bending directions of the crossed curved beams (2) arranged in the opposite mounting planes of the rectangular frame (1) are consistent;
s5: constructing a metamaterial, sequentially connecting the middle parts of cross curved beams (2) of different unit cells end to end through a connecting rod (3), connecting the plurality of unit cells to form a multi-cell metamaterial structure, processing the metamaterial by utilizing a 3D printing technology, and designing an acting force threshold value of the processed metamaterial in any one direction of +/-x, +/-y and +/-z directions through a formula F by taking three mutually perpendicular edges in the unit cell structure as three axes of x, y and z respectivelyt＝2n1ftopTo obtain n1For the number of cells connected in parallel in a given direction, FtThe macroscopic acting force threshold value of the metamaterial in any one direction of +/-x, +/-y and +/-z is estimated.
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