CN117153302A - Mechanical superstructure of poisson's ratio different number under transverse expansion type stretching and compression state - Google Patents
Mechanical superstructure of poisson's ratio different number under transverse expansion type stretching and compression state Download PDFInfo
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- CN117153302A CN117153302A CN202311092315.9A CN202311092315A CN117153302A CN 117153302 A CN117153302 A CN 117153302A CN 202311092315 A CN202311092315 A CN 202311092315A CN 117153302 A CN117153302 A CN 117153302A
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Abstract
The invention relates to a mechanical superstructure of Poisson's ratio different numbers in a transverse expansion type stretching and compression state, wherein four outer diagonal rods and two middle long vertical rods of a transverse expansion type combined hexagonal structural unit form an outer convex hexagon, four inner diagonal rods and two middle long vertical rods form an inner concave hexagon, and hinge points of the two outer diagonal rods at the upper end and the lower end are respectively connected with hinge points of the two inner diagonal rods through a short vertical rod; the middle parts of the outer diagonal rods and the inner diagonal rods are respectively provided with a composite hinge, each composite hinge comprises four short rods, the four short rods are sequentially hinged end to form a foldable or unfolding quadrilateral, two oppositely arranged hinge points are respectively connected with the outer diagonal rods/the inner diagonal rods, and in an initial state, the composite hinge is in a folded state and perpendicular to the outer diagonal rods/the inner diagonal rods, and at the moment, the composite hinge can only bear pressure but cannot bear tension. The invention can realize the transverse expansion cross section deformation characteristic in the in-plane stretching or compression state, and has higher material utilization rate and larger Poisson ratio absolute value.
Description
Technical Field
The invention relates to the technical field of mechanical superstructures, in particular to a mechanical superstructure with Poisson's ratio difference in a transverse expansion type stretching and compression state.
Background
The mechanical metamaterial/structure is paid attention to by excellent mechanical properties, such as special specific strength, specific rigidity, excellent impact resistance and energy absorption capability and the like. The mechanical superstructure realizes the special mechanical properties which the natural material does not have through the internal structural design rather than the chemical components. The mechanical superstructural design focuses on the mechanical properties of the functional units of the structure, which generally include elastic modulus, shear modulus, bulk modulus, poisson's ratio or coefficient of thermal expansion, etc. According to the different mechanical parameters regulated and controlled by the functional units of the metamaterial structure, the mechanical superstructure can be subdivided into any Poisson ratio metamaterial, shear modulus blanking five-mode inverse expansion metamaterial, negative compressible metamaterial, negative/zero thermal expansion metamaterial and stiffness-adjustable metamaterial. In addition, the material can be deformed in various shapes under the conditions of temperature, force field and the like by carrying out positive, zero and negative modulation on the properties of poisson ratio, compressibility, thermal expansion and the like. Therefore, mechanical superstructures have great potential in precision instruments (e.g., robots, medical devices, aerospace devices, etc.) and other applications.
The negative poisson ratio mechanical superstructure can be expanded transversely when stretched, and contracted transversely when compressed. Because the negative poisson ratio mechanical superstructure has abnormal poisson ratio performance, the negative poisson ratio mechanical superstructure has great attention in the fields of medical appliances, aerospace, impact protection and the like. However, the poisson ratio of the negative poisson ratio mechanical superstructure in both the tensile and compressive states is negative, and transverse constant expansion or constant contraction cannot be achieved. In practical applications, however, there is a need for the structure to expand or contract laterally, whether in tension or in compression. At present, the mechanical superstructure with Poisson's ratio different number characteristics in the stretching and compression state is less, and the material utilization rate is not high or the Poisson's ratio absolute value is less is the general problem of this kind of mechanical superstructure.
Chinese patent CN115163717a discloses a novel composite metamaterial capable of realizing poisson's ratio positive-negative conversion and a design method thereof, which comprises a frame structure with a concave hexagon shape, wherein two sides of the frame structure are provided with outwardly convex folded corner structures, quadrilateral materials are arranged between the frame structure and the folded corner structures, and the quadrilateral materials are made of tensile but non-compressive polymer materials. The novel composite metamaterial can be characterized by positive poisson ratio and negative poisson ratio, and can always shrink inwards when being longitudinally stressed or pulled, so that functions of the metamaterial are enriched, and the practical application range of the metamaterial is expanded. However, the novel composite metamaterial is composed of at least two materials, and has the problems of complex processing procedures and high cost compared with one material. In addition, the first quadrilateral material of the composite metamaterial is a filling material, so that the overall material utilization rate of the composite metamaterial is low. Meanwhile, the Poisson's ratio conversion performance of the composite metamaterial depends on the special performance (namely tensile property but not compressive property) of a certain polymer material, and is limited.
Disclosure of Invention
The invention aims to solve the technical problems of the prior art, and provides a mechanical superstructure of Poisson's ratio different numbers in a transverse expansion type stretching and compression state, which can realize transverse expansion type cross section deformation characteristics in both an in-plane stretching state and a compression state, has higher material utilization rate and has larger Poisson's ratio absolute value.
The technical scheme adopted by the invention for solving the technical problems is as follows:
a mechanical superstructure of Poisson's ratio difference number in a transverse expansion type stretching and compression state comprises a plurality of transverse expansion type combined hexagonal structural units; each transverse expansion type combined hexagonal structure unit comprises four outer inclined rods, four inner inclined rods, two long upright rods, two short upright rods and a plurality of composite hinges, wherein the upper end of the transverse expansion type combined hexagonal structure unit comprises two outer inclined rods, two inner inclined rods and two outer inclined rods, the lower end of the transverse expansion type combined hexagonal structure unit comprises two outer inclined rods, two inner inclined rods, the four outer inclined rods and the middle two long upright rods form an outer convex hexagon, the four inner inclined rods and the middle two long upright rods form an inner concave hexagon, the hinge points of the two outer inclined rods at the upper end are connected with the hinge points of the two inner inclined rods through one short upright rod, the hinge points of the two outer inclined rods at the lower end are connected with the hinge points of the two inner inclined rods through the other short upright rods, and the rods are all hinged; all outer diagonal bars all are equipped with at least one with the middle part of interior diagonal bar compound hinge, compound hinge includes four quarter butt, four quarter butt hinges are articulated in proper order and are linked to each other to form collapsible or expansion's quadrangle, and wherein two hinge points that set up relatively link to each other with outer diagonal bar/interior diagonal bar respectively, under initial condition, compound hinge is folding state and perpendicular to outer diagonal bar/interior diagonal bar, and compound hinge can only bear pressure and can not bear the pulling force this moment.
In the above scheme, when the transverse expansion type combined hexagonal structural unit is pressed, the external load direction points to the inside of the structure along the length direction of the short upright rod, and at the moment, the composite hinges on all the inner inclined rods are unfolded to enable the inner inclined rods to extend, so that the structure expands outwards transversely.
In the above scheme, when the transverse expansion type combined hexagonal structural unit is pulled, the external load direction points to the outside of the structure along the length direction of the short upright rod, and at the moment, the composite hinges on all the external inclined rods are unfolded to enable the external inclined rods to extend, so that the structure expands outwards transversely.
In the scheme, the lengths of the four short rods of the composite hinge are equal, and the composite hinge is in a linear shape when in a folded state.
In the scheme, the middle point of each outer inclined rod and each inner inclined rod is provided with one composite hinge.
In the scheme, a plurality of composite hinges with the same quantity are arranged on each outer inclined rod and each inner inclined rod, and the composite hinges are sequentially distributed along the length direction of the rod piece.
In the above scheme, the composite hinge further comprises four rotatable hinges, and the two short rods are connected through the rotatable hinges.
In the scheme, the composite hinge is made of plastic materials, and the two short rods are connected through the plastic hinge with the self-deformation structure.
In the above scheme, the mechanical superstructure of poisson's ratio under the state of transverse expansion stretching and compression comprises a plurality of transverse expansion type combined hexagonal structural units distributed in a matrix, wherein two adjacent transverse combined hexagonal structural units share a long upright rod; two vertically adjacent combined hexagonal structural units are mutually connected through a short vertical rod.
The invention has the beneficial effects that:
1. according to the mechanical superstructure provided by the invention, by designing the transverse expansion type combined hexagonal structural unit, the structural unit can realize the transverse expansion cross section deformation characteristic in both an in-plane stretching state and a compression state, namely the structure has the characteristic of Poisson ratio different numbers in the stretching state and the compression state. In addition, the transverse expansion type combined hexagonal structural unit designed by the invention adopts the composite hinge with a movable quadrilateral structure, so that the structural unit has the Poisson ratio different number performance under the stretching and compression states, the theoretical utilization rate of the material can be up to 71.4%, and the absolute value of the theoretical Poisson ratio can be up to more than 2.
2. According to the invention, through periodic arrangement and combination of the transverse expansion type combined hexagonal structural units, the mechanical superstructure with Poisson's ratio different number performance in a stretching and compression state is obtained.
3. Compared with the prior art, the invention can be made of one material and has the advantages of simple processing procedure and lower cost. The invention does not adopt a filling structure form, so that the material utilization rate is higher. In addition, the Poisson's ratio convertible property of the invention is completely determined by the structural form and does not depend on the material property.
Drawings
The invention will be further described with reference to the accompanying drawings and examples, in which:
FIG. 1 is a schematic illustration of a mechanical superstructure of Poisson's ratio variation in the transversely expanded stretched and compressed state;
FIG. 2 is a schematic structural view of a laterally expanding composite hexagonal structural element;
FIG. 3 is a schematic structural view of a composite hinge of laterally expanding composite hexagonal structural elements;
fig. 4 is a schematic diagram of lateral deformation of a lateral expansion type combined hexagonal structural unit.
In the figure: 100. a transverse expansion type combined hexagonal structural unit; 10. an outer diagonal bar; 20. an inner diagonal rod; 30. a composite hinge; 31. a short bar; 32. a rotatable hinge; 40. a long upright rod; 50. a short upright;
200. a mechanical superstructure of poisson's ratio in a transversely expanded stretching and compressing state;
300. and (5) external load.
Detailed Description
For a clearer understanding of technical features, objects and effects of the present invention, a detailed description of embodiments of the present invention will be made with reference to the accompanying drawings.
As shown in fig. 1, a mechanical superstructure 200 of poisson's ratio under a transverse expansion type stretching and compression state according to an embodiment of the present invention includes a plurality of transverse expansion type combined hexagonal structural units 100 distributed in a matrix.
As shown in fig. 2, each of the lateral expansion type combined hexagonal structural units 100 includes four outer diagonal rods 10, four inner diagonal rods 20, two long vertical rods 40, two short vertical rods 50, and a plurality of complex hinges 30. The upper end of the transverse expansion type combined hexagonal structural unit 100 comprises two outer diagonal rods 10 and two inner diagonal rods 20, the lower end of the transverse expansion type combined hexagonal structural unit comprises two outer diagonal rods 10 and two inner diagonal rods 20, four outer diagonal rods 10 and two middle long vertical rods 40 form an outer convex hexagon, four inner diagonal rods 20 and two middle long vertical rods 40 form an inner concave hexagon, the hinge points of the two outer diagonal rods 10 and the hinge points of the two inner diagonal rods 20 at the upper end of the structural unit are connected through one short vertical rod 50, the hinge points of the two outer diagonal rods 10 and the hinge points of the two inner diagonal rods 20 at the lower end of the structural unit are connected through another short vertical rod 50, and all rods are hinged. At least one composite hinge 30 is arranged in the middle of each of the outer diagonal rods 10 and the inner diagonal rods 20, as shown in fig. 3, the composite hinge 30 comprises four short rods 31, the four short rods 31 are sequentially hinged end to form a foldable or unfolding quadrilateral, and two oppositely arranged hinge points are respectively connected with the outer diagonal rods 10 and the inner diagonal rods 20. In the initial state, the composite hinge 30 of the lateral expansion type combined hexagonal structural unit 100 is in a folded state and perpendicular to the outer diagonal rods 10/inner diagonal rods 20, and at this time, the composite hinge 30 can only bear a compressive force but cannot bear a tensile force.
As shown in fig. 4, when the transverse expansion type combined hexagonal structural unit 100 is compressed, the outer load 300 is directed toward the inside of the structure along the length direction of the short leg 50, the outer diagonal 10 is compressed, and the inner diagonal 20 is stretched. Since the composite hinge 30 can only bear a compressive force and cannot bear a tensile force at this time, the inner diagonal rod 20 can be freely extended. The structural deformation at this time is similar to that of a convex hexagon, i.e., expands laterally outward.
When the transverse expansion type combined hexagonal structural unit 100 is stretched, the external load 300 is directed to the outside of the structure along the length direction of the short vertical rod 50, the external diagonal rod 10 is stretched, and the internal diagonal rod 20 is compressed. Since the composite hinge 30 can only bear a compressive force and not a tensile force at this time, the outer diagonal member 10 can be freely extended. The structural deformation at this time resembles a concave hexagon, i.e., expands laterally outward.
Therefore, the mechanical superstructure provided by the invention can realize the transverse expansion cross section deformation characteristic in both an in-plane stretching state and a compression state, namely the structure has the characteristic of Poisson's ratio difference between the stretching state and the compression state. In addition, the transverse expansion type combined hexagonal structural unit 100 of the invention adopts the composite hinge 30 with a movable quadrilateral structure, so that the structural unit has the following structureThe theoretical utilization rate of the material is up to 71.4% and the absolute value of the theoretical poisson ratio is up to more than 2 while the poisson ratio different number performance under the stretching and compression states is provided. It should be explained that, the theoretical utilization ratio of the material refers to the ratio of the structural mass participating in resisting deformation to the total mass, and for the present invention, when the outer diagonal member 10 does not participate in resisting deformation during stretching, the material utilization ratio is (14-4)/14=71.4% assuming that the lengths and mass ratios of the outer diagonal member 10, the inner diagonal member 20, the long vertical member 40 and the short vertical member 50 are 1:1:2:1. The theoretical poisson ratio of a material refers to the ratio between the amount of lateral deformation under load and the amount of deformation under load. For the present invention, assuming that the angle between the inner diagonal 20 and the short vertical 50 is θ, the theoretical poisson's ratio is:where d represents a derivative symbol and l is the length of the outer diagonal rod 10. It is apparent that when θ is small, 1/tan θ is greater than 2. In fact, when the inner diagonal rod 20 is equal in length to the outer diagonal rod 10, the smaller θ, the greater the ratio of the length of the short vertical rod 50 to the outer diagonal rod 10, and the greater the material utilization. I.e., the smaller θ, the greater the material utilization versus theoretical poisson's ratio.
Further preferably, the four short bars 31 of the composite hinge 30 have equal lengths, and the composite hinge 30 is in a straight line shape when in a folded state.
Further preferably, a compound hinge 30 is provided at the midpoint of each of the outer 10 and inner 20 diagonal rods. The outer diagonal rods 10 and the inner diagonal rods 20 can be provided with a plurality of composite hinges 30 with the same quantity according to the requirement, and the plurality of composite hinges 30 are sequentially distributed along the length direction of the rod piece.
Further preferably, the composite hinge 30 further comprises four rotatable hinges 32, and the two short rods 31 are connected by the rotatable hinges 32. When the composite hinge 30 is made of plastic material, the composite hinge 30 may not include the rotatable hinge 32, and the two short rods 31 are connected by the plastic hinge which deforms itself.
Further optimizing, two adjacent combined hexagonal structural units in the transverse direction share one long upright 40; vertically adjacent two of the assembled hexagonal structural units are connected to each other by a short upright 50. The two-dimensional mechanical superstructure section shown in fig. 1 is stretched along the direction vertical to the paper surface, so that a honeycomb-like mechanical superstructure can be formed.
In the description of the present invention, it should be understood that the terms "long upright," "short upright," "inner diagonal," "outer diagonal," "short bar," and the like are used to indicate and distinguish structural members, merely to facilitate describing the present invention and to simplify the description, and do not indicate or imply that the indicated members must have the characteristics included in the terms and therefore should not be construed as limiting the invention.
The embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to the above-described embodiments, which are merely illustrative and not restrictive, and many forms may be made by those having ordinary skill in the art without departing from the spirit of the present invention and the scope of the claims, which are to be protected by the present invention.
Claims (9)
1. The mechanical superstructure of poisson's ratio different number under the stretching and compression state of the horizontal expansion type, characterized by, including several horizontal expansion type combined hexagonal structural unit;
each transverse expansion type combined hexagonal structure unit comprises four outer inclined rods, four inner inclined rods, two long upright rods, two short upright rods and a plurality of composite hinges, wherein the upper end of the transverse expansion type combined hexagonal structure unit comprises two outer inclined rods, two inner inclined rods and two outer inclined rods, the lower end of the transverse expansion type combined hexagonal structure unit comprises two outer inclined rods, two inner inclined rods, the four outer inclined rods and the middle two long upright rods form an outer convex hexagon, the four inner inclined rods and the middle two long upright rods form an inner concave hexagon, the hinge points of the two outer inclined rods at the upper end are connected with the hinge points of the two inner inclined rods through one short upright rod, the hinge points of the two outer inclined rods at the lower end are connected with the hinge points of the two inner inclined rods through the other short upright rods, and the rods are all hinged; all outer diagonal bars all are equipped with at least one with the middle part of interior diagonal bar compound hinge, compound hinge includes four quarter butt, four quarter butt hinges are articulated in proper order and are linked to each other to form collapsible or expansion's quadrangle, and wherein two hinge points that set up relatively link to each other with outer diagonal bar/interior diagonal bar respectively, under initial condition, compound hinge is folding state and perpendicular to outer diagonal bar/interior diagonal bar, and compound hinge can only bear pressure and can not bear the pulling force this moment.
2. The mechanical superstructure of poisson's ratio in the extended and compressed state of claim 1, wherein when the said combined hexagonal structure units are compressed, the external load direction is directed into the structure along the length of the short uprights, and the composite hinges on all the inner uprights are unfolded to extend the inner uprights, and the structure is extended laterally outwards.
3. The mechanical superstructure of poisson's ratio in the extended and compressed state of claim 2, wherein when the said combined hexagonal structure units are pulled, the external load direction is directed to the outside of the structure along the length direction of the short uprights, and the composite hinges on all the external diagonal rods are unfolded to extend the external diagonal rods, and the structure is extended laterally outwards.
4. The mechanical superstructure of poisson's ratio in the extended and compressed state of claim 1, wherein the four stubs of the composite hinge are equal in length and in the folded state the composite hinge is in a straight line configuration.
5. The mechanical superstructure of poisson's ratio in the expanded and compressed state of claim 1, wherein one of said compound hinges is provided at the midpoint of each of the outer and inner diagonal rods.
6. The mechanical superstructure of poisson's ratio under the tensile and compressive state of horizontal expansion type according to claim 1, wherein a plurality of the compound hinges with the same number are arranged on each of the outer diagonal rods and the inner diagonal rods, and the compound hinges are sequentially arranged along the length direction of the rod piece.
7. The mechanical superstructure of poisson's ratio in the expanded and compressed state of claim 1, wherein the composite hinge further comprises four rotatable hinges through which two stubs are connected.
8. The mechanical superstructure of poisson's ratio in the extended and compressed state in the transverse direction according to claim 1, wherein the composite hinge is made of plastic material, and the two stubs are connected by a plastic hinge that deforms itself.
9. The mechanical superstructure of poisson's ratio in a transversely expanded stretched and compressed state according to claim 1, wherein the mechanical superstructure of poisson's ratio in a transversely expanded stretched and compressed state comprises a plurality of transversely expanded combined hexagonal structural units distributed in a matrix, wherein two laterally adjacent combined hexagonal structural units share a long upright; two vertically adjacent combined hexagonal structural units are mutually connected through a short vertical rod.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311092315.9A CN117153302A (en) | 2023-08-28 | 2023-08-28 | Mechanical superstructure of poisson's ratio different number under transverse expansion type stretching and compression state |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202311092315.9A CN117153302A (en) | 2023-08-28 | 2023-08-28 | Mechanical superstructure of poisson's ratio different number under transverse expansion type stretching and compression state |
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| CN202311092315.9A Pending CN117153302A (en) | 2023-08-28 | 2023-08-28 | Mechanical superstructure of poisson's ratio different number under transverse expansion type stretching and compression state |
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