Structure with bidirectional zero Poisson's ratio effect and its loading method

Abstract

The present invention discloses a novel structure with bidirectional zero Poisson's ratio effect and a loading method, which relates to the technical field of structural design and manufacturing. The novel structure includes a structural unit, which includes: a connecting wall assembly, including 4 connecting wall units, the cross-sectional profile of the connecting wall unit is square, and the 4 connecting wall units are arranged in a rectangular array; a connecting assembly, including 4 connecting units, and the 4 connecting units are arranged in a circular array with the center of the connecting wall assembly as the center of the circle, each connecting unit is located between two adjacent connecting wall units, and the two ends of each connecting unit are respectively connected to the two adjacent connecting wall units. The novel structure can provide a zero Poisson's ratio effect in two directions of a two-dimensional plane; the novel structure is composed of a plurality of structural unit rectangular arrays, and the Poisson's ratio effect of the novel structure has no correlation with the Poisson's ratio of the material; the novel structure has the characteristics of simple structure, no complex curve design, and can simplify the production process.

Description

Technical Field

[0001] The invention relates to the technical field of structural design and manufacturing, and in particular to a structure with bidirectional zero Poisson's ratio effect and a loading method thereof. Background Art

[0002] Porous cellular material structures are lightweight and multifunctional, and have been used in insulation, packaging, structural, flotation and other fields. Poisson's ratio mainly reflects the elastic constant of the lateral deformation of the material and the negative ratio of the lateral strain to the axial strain when subjected to unidirectional tension or compression. For a zero Poisson's ratio structure, the ratio of the absolute value of the lateral positive strain to the axial positive strain is 0 when subjected to unidirectional tension or compression, that is, the structure does not produce lateral strain when subjected to longitudinal load. This type of structural material is suitable for fields that are sensitive to deformation in non-load-bearing directions. In existing structural designs, the zero Poisson's ratio effect is only applicable to one direction, and there are relatively few structures in two-dimensional structures that have both lateral and longitudinal zero Poisson's ratio effects. Summary of the invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a structure with a bidirectional zero Poisson's ratio effect.

[0004] The invention also provides a loading method for a structure with bidirectional zero Poisson's ratio effect.

[0005] The structure with bidirectional zero Poisson's ratio effect of the first aspect of the embodiment of the present invention includes structural units, which include: a connecting wall component, including 4 connecting wall units, the cross-sectional profile of the connecting wall unit is a hollow square, and the 4 connecting wall units are arranged in a rectangular array; a connecting component, including 4 connecting units, the 4 connecting units are arranged in a circular array with the center of the connecting wall component as the center, each of the connecting units is located between two adjacent connecting wall units, and the two ends of each connecting unit are respectively connected to the two adjacent connecting wall units; the connecting unit includes hypotenuse one, hypotenuse two, hypotenuse three and hypotenuse four, the hypotenuse one is parallel to the hypotenuse two, the hypotenuse three is parallel to the hypotenuse four, the lengths of the hypotenuse one, the hypotenuse two, the hypotenuse three and the hypotenuse four are equal, one end of the hypotenuse one is connected to one end of the hypotenuse three, and the connecting unit is folded toward the center of the connecting wall component.

[0006] According to an embodiment of the present invention, the side length of the connecting wall unit is H, the length of the hypotenuse 1 is L, and the ratio of H to L is ɑ, which satisfies: α>0.2.

[0007] According to an embodiment of the present invention, α=0.5.

[0008] According to an embodiment of the present invention, the thickness of the connecting wall unit is t, and the ratio of t to L is β, which satisfies: β<0.1.

[0009] According to an embodiment of the present invention, β=0.05.

[0010] According to an embodiment of the present invention, the angle between the first hypotenuse and the third hypotenuse is 2θ, which satisfies: 90°<2θ<180°.

[0011] According to an embodiment of the present invention, the angle is equal to 120°.

[0012] According to an embodiment of the present invention, the structure with bidirectional zero Poisson's ratio effect is formed by a rectangular array of structural units.

[0013] According to an embodiment of the present invention, the structure with bidirectional zero Poisson's ratio effect can be prepared by a sheet stacking method, a mold casting method, a rapid prototyping method, an extrusion molding method or a photocuring method.

[0014] The loading method of the second aspect of the present invention is to load the structure with bidirectional zero Poisson's ratio effect as described above, comprising the following steps:

[0015] Apply uniaxial stress to the structural unit, and the stress acts on the edges of the connecting wall units on the left and right sides of the square structural unit;

[0016] or

[0017] The structural unit is subjected to bidirectional loading, and the stress acts on the edges of the connecting wall unit on the left, right and top of the structural unit.

[0018] The structure with bidirectional Poisson's ratio effect of the embodiment of the present invention has at least the following beneficial effects: the embodiment of the present invention proposes a structure with bidirectional zero Poisson's ratio effect, which can provide zero Poisson's ratio effect in two directions of a two-dimensional plane; the structure is composed of a plurality of rectangular arrays of structural units, and the Poisson's ratio effect of the structure has no correlation with the Poisson's ratio of the material; the structure with bidirectional zero Poisson's ratio effect of the embodiment of the present invention has the characteristics of simple structure, no complicated curve design, and can simplify the production process, thereby achieving the purpose of reducing production costs.

[0019] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0021] Figure 1It is a schematic diagram of the structure of the structural unit in an embodiment of the present invention;

[0022] Figure 2 for Figure 1 Schematic diagram of the left side;

[0023] Figure 3 is a schematic structural diagram of a structure with a bidirectional zero Poisson's ratio effect according to this embodiment;

[0024] Figure 4 It is a schematic diagram of the deformation of the structural unit in this embodiment when subjected to a unidirectional force;

[0025] Figure 5 It is a schematic diagram of the deformation of the structural unit in this embodiment when subjected to bidirectional forces;

[0026] Figure 6a It is a schematic diagram of the force analysis of the second hypotenuse 4 when the structural unit is loaded in mode 1;

[0027] Figure 6b It is a schematic diagram of the force analysis of the first hypotenuse 2 when the structural unit is loaded in the second mode;

[0028] Figure 7 It is a diagram of the overall compression edge when the structure with bidirectional zero Poisson's ratio effect is loaded according to an embodiment of the present invention;

[0029] Figure 8 It is a schematic diagram of the Poisson's ratio stability of a structure with bidirectional zero Poisson's ratio effect and its loading mode under different stresses based on finite element simulation according to an embodiment of the present invention.

[0030] Reference numerals:

[0031] Structure 1 with bidirectional zero Poisson's ratio effect;

[0032] A connecting wall unit 10, a first connecting wall unit 11, a second connecting wall unit 12, a third connecting wall unit 13, and a fourth connecting wall unit 14;

[0033] A connection unit 20, a first connection unit 21, a second connection unit 22, a third connection unit 23, and a fourth connection unit 24;

[0034] Hypotenuse 1 201, first hypotenuse 1 201a, second hypotenuse 1 201b, third hypotenuse 1 201c, fourth hypotenuse 1 201d,

[0035] Hypotenuse 202, first hypotenuse 202a, second hypotenuse 202b, third hypotenuse 202c, fourth hypotenuse 202d,

[0036] Hypotenuse 3 203, first hypotenuse 3 203a, second hypotenuse 3 203b, third hypotenuse 3 203c, fourth hypotenuse 3 203d,

[0037] Hypotenuse four 204, first hypotenuse four 204a, second hypotenuse four 204b, third hypotenuse four 204c, fourth hypotenuse four 204d. DETAILED DESCRIPTION

[0038] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0039] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., and orientations or positional relationships indicated are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0040] In the description of the present invention, "several" means more than one, "many" means more than two, "greater than", "less than", "exceed", etc. are understood to exclude the number itself, and "above", "below", "within", etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0041] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0042] In the description of the present invention, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0043] See also Figures 1 to 3 The structure 1 with bidirectional zero Poisson's ratio effect according to the first aspect of the present invention comprises a structural unit, and the structural unit comprises a connecting wall component and a connecting component.

[0044] Specifically, the connecting wall assembly includes four connecting wall units 10, the cross-sectional profile of the connecting wall unit 10 is a hollow square, and the four connecting wall units 10 are arranged in a rectangular array; the connecting assembly includes four connecting units 20, and the four connecting units 20 are arranged in a circular array with the center of the connecting wall assembly as the center, each connecting unit 20 is located between two adjacent connecting wall units 10, and the two ends of each connecting unit 20 are respectively connected to the two adjacent connecting wall units 10.

[0045] Among them, the connecting unit 20 includes hypotenuse 1 201, hypotenuse 2 202, hypotenuse 3 203 and hypotenuse 4 204, hypotenuse 1 201 is parallel to hypotenuse 2 202, hypotenuse 3 203 is parallel to hypotenuse 4 204, the lengths of hypotenuse 1 201, hypotenuse 2 202, hypotenuse 3 203 and hypotenuse 4 204 are all equal, one end of hypotenuse 1 201 is connected to one end of hypotenuse 3 203, and the connecting unit 20 appears to be folded toward the center of the connecting wall assembly.

[0046] It should be pointed out that, since the connecting wall units 10 in the structural unit are arranged in a rectangular array and the connecting units 20 are arranged in a circular array, the distance between the two ends of each connecting unit 20 is equal, the outer contour of the structural unit is square, and the four connecting units 20 and the four connecting wall units 10 in the structural unit are strictly symmetrically distributed; the hypotenuse 1 201 and the hypotenuse 3 203 in the connecting unit 20 are symmetrical about the symmetry axis of the connecting wall unit 10 connected at both ends of the connecting unit 20; the connecting unit 20 on the left side of the structural unit is symmetrical with the connecting unit 20 on the right side; the connecting unit 20 at the upper end of the structural unit is symmetrical with the connecting unit 20 at the lower end.

[0047] The geometric parameters of the structural unit directly affect the properties of the structure, including but not limited to the elastic modulus, shear modulus and Poisson's ratio effect. In one embodiment of the present invention, the side length of the connecting wall unit 10 is H, the length of the hypotenuse 201 is L, and the ratio of H to L is ɑ, satisfying: α>0.2. When the value of α is too small, the hollow square block formed inside the connecting wall unit 10 tends to be solid, and the function of the connecting wall structure is lost. Therefore, the value of α is set to be greater than 0.2 to ensure the characteristics of the connecting wall unit 10, thereby ensuring that the structural unit has a stable zero Poisson's ratio effect; the larger the value of α, the greater the spatial occupancy of the square connecting wall unit 10.

[0048] It can be understood that the zero Poisson's ratio effect of the structure 1 in the embodiment of the present invention is related to the ratio of α, and the selection of specific parameters of the structural unit does not affect the bidirectional zero Poisson's ratio effect of the structure 1 in this embodiment. Even if the length of the side of the connecting wall unit 10 is different from the length of the hypotenuse 201, due to the structural characteristics of the structure 1 in the embodiment of the present invention itself, the structure 1 in the embodiment of the present invention still has a bidirectional zero Poisson's ratio effect.

[0049] Setting the ratio of the side length H of the connecting wall unit 10 to the length L of the hypotenuse 1 201 to α can better characterize the influence of the geometric parameters of the structural unit on the structure and enhance the connection between the geometric parameters of each structure in the structural unit. In an embodiment of the present invention, α=0.5.

[0050] The thickness of the connecting wall unit 10 is t, and the ratio of t to L is β. Currently, there is no structure with an absolute zero Poisson's ratio effect, so the numerical boundary between zero Poisson's ratio and positive and negative Poisson's ratios is not clear, while the value of β affects the zero Poisson's ratio effect. The smaller the value of β, the better the zero Poisson's ratio effect of the structure 1 in the embodiment of the present invention. The key parameter affecting the Poisson's ratio effect of the structure 1 is the value of β, and the specific value of t is not important in the embodiment of the present invention. In other words, in the embodiment of the present invention, there is no restriction on the specific value of the thickness t of the connecting wall unit 10, and the value of t can be selected according to actual needs.

[0051] In one embodiment of the present invention, β<0.1. When the value of β is small enough, the zero Poisson's ratio effect of the structure 1 of the embodiment of the present invention is better. Setting the value of β to less than 0.1 can ensure that the structure 1 has a good two-way zero Poisson's ratio effect. The value of β includes but is not limited to 0.05 or 0.08.

[0052] It should be pointed out that the ratio of the side length H of the connecting wall unit 10 to the length L of the hypotenuse 201 of the connecting unit 20 is denoted as α, and the ratio of the thickness t of the connecting wall unit 10 to the length L of the hypotenuse 201 is denoted as β, which can realize the dimensionless geometric parameters of the structural unit, thereby achieving the purpose of simplifying experiments or calculations.

[0053] The angle between the first hypotenuse 201 and the third hypotenuse 203 affects the force performance and deformation degree of the structure 1. In some embodiments, the angle between the first hypotenuse 201 and the third hypotenuse 203 is 2θ, which satisfies: 90°<2θ<180°.

[0054] In one embodiment of the present invention, the angle is equal to 120°, so that the structure 1 with bidirectional zero Poisson's ratio effect can have both good force-bearing performance and a large space occupancy rate, which is conducive to saving material costs.

[0055] The structure 1 with bidirectional zero Poisson's ratio effect of the embodiment of the present invention is composed of a rectangular array of structural units, forming a grid structure with bidirectional zero Poisson's ratio effect formed by a linear array of structural units. In practical applications, the parameters of the structural units can be changed to meet the requirements of the in-plane and out-of-plane macroscopic performance of the mesh structure.

[0056] The structure 1 with bidirectional zero Poisson's ratio effect in the embodiment of the present invention has a simple structure and no complicated curve design. It can be prepared by one of the methods of sheet stacking, mold casting, rapid prototyping, extrusion molding or photocuring, which is conducive to simplifying the production process and reducing production costs.

[0057] Since the structure has a bidirectional zero Poisson's ratio effect and is symmetrical, the effects are the same in unidirectional tension and compression.

[0058] See also Figure 4 The four square connecting wall units 10 of the structural unit are respectively the first connecting wall unit 11, the second connecting wall unit 12, the third connecting wall unit 13 and the fourth connecting wall unit 14 in a clockwise direction; the four connecting units 20 of the structural unit are respectively recorded as the first connecting unit 21, the second connecting unit 22, the third connecting unit 23 and the fourth connecting unit 24 in a clockwise direction.

[0059] In this embodiment, the loading method of the structure 1 with bidirectional zero Poisson's ratio effect includes the following two loading methods:

[0060] Method 1: Apply unidirectional load to structure 1, see Figure 4 As shown. The stress acts on the edges of the connecting wall units 10 on the left and right sides of the square structural unit, the distance between the first connecting unit 21 and the third connecting unit 23, the distance between the first connecting wall unit 11 and the second connecting wall unit 12, and the distance between the third connecting wall unit 13 and the fourth connecting wall unit 14 are all shortened; the angle between the second hypotenuse 1 201b and the second hypotenuse 3 203b in the second connecting unit 22, the angle between the second hypotenuse 2 202b and the second hypotenuse 4 204b, and the angle between the fourth hypotenuse 1 201d and the fourth hypotenuse 3 203d, the angle between the fourth hypotenuse 2 202d and the fourth hypotenuse 4 204d in the fourth connecting unit 24 are shortened. The angles are reduced; however, the distance between the first connecting wall unit 11 and the fourth connecting wall unit 14, and the distance between the second connecting wall unit 12 and the third connecting wall unit 13 remain unchanged; the angle between the first hypotenuse 1 201a and the first hypotenuse 3 203a and the angle between the first hypotenuse 2 202a and the first hypotenuse 4 204a in the first connecting unit 21 remain unchanged, and the angle between the third hypotenuse 1 201c and the third hypotenuse 3 203c and the angle between the third hypotenuse 2 202c and the third hypotenuse 4 204c in the third connecting unit 23 remain unchanged, so the grid structure has a zero Poisson's ratio. Since the structure is strictly symmetrical, the structure has a bidirectional zero Poisson's ratio effect.

[0061] Method 2: Bidirectional loading of structural units, see Figure 5As shown. Stress acts on the edges of the connecting wall unit 10 on the left, right and top of the structural unit, the relative distance between the first connecting unit 21 and the second connecting unit 22, the relative distance between the second connecting unit 22 and the fourth connecting unit 24, the distance between the first connecting wall unit 11 and the second connecting wall unit 12, the distance between the third connecting wall unit 13 and the fourth connecting wall unit 14, the distance between the first connecting wall units 11, and the distance between the second connecting wall unit 12 and the third connecting wall unit 13 are all reduced; the angle between the second hypotenuse 1 201b and the second hypotenuse 3 203b in the second connecting unit 22, the second hypotenuse 204a and the second hypotenuse 205b are reduced. The angle between the fourth hypotenuse 202b and the second hypotenuse four 204b, the angle between the fourth hypotenuse 1 201d and the fourth hypotenuse three 203d, and the angle between the fourth hypotenuse 202d and the fourth hypotenuse four 204d in the fourth connecting unit 24, the angle between the first hypotenuse 1 201a and the first hypotenuse three 203a, and the angle between the first hypotenuse 2 202a and the first hypotenuse four 204a in the first connecting unit 21, as well as the angle between the third hypotenuse 1 201c and the third hypotenuse three 203c, and the angle between the third hypotenuse 2 202c and the third hypotenuse four 204c in the third connecting unit 23 all decrease, showing a bidirectional load-bearing type.

[0062] In the first method, the first connection unit 21 and the third connection unit 23 are not affected by the force, and the second connection unit 22 is symmetrical with the fourth connection unit 24, and the lateral force they are subjected to is of the same nature. Therefore, the second hypotenuse 204b in the second connection unit 22 is analyzed, as shown in FIG. Figure 6a As shown:

[0063] (1)

[0064] Where M1 is the bending moment of the second hypotenuse 204b, P is the external force on one end of the second hypotenuse 204b, L is the length of the second hypotenuse 204b, and θ is half of the angle of the oblique side. P can be converted from the horizontal stress:

[0065] (2)

[0066] in Represents horizontal stress. Taking the intersection of the second hypotenuse 4 204b and the second hypotenuse 2 202b as the reference point, the intersection of the second hypotenuse 4 204b and the second hypotenuse 2 202b and the intersection of the second hypotenuse 3 203b and the second hypotenuse 1 201b are displaced downwards by the standard beam theory, and the deflection δ1 is:

[0067] (3)

[0068] Where Es represents the elastic modulus, I represents the second moment of inertia of the oblique edge. In this structure, the hole wall thickness is uniform, so I is taken as:

[0069] (4)

[0070] Where b represents the cell wall depth, and t represents the cell wall thickness. The intersection of the fourth hypotenuse 2 202d and the fourth hypotenuse 4 204d, and the intersection of the fourth hypotenuse 1 201d and the fourth hypotenuse 3 203d are displaced upward, and the deflection δ2 is:

[0071] (5)

[0072] The distance between the first connecting wall unit 11 and the second connecting wall unit 12 and the distance between the third connecting wall unit 13 and the fourth connecting wall unit 14 are reduced by an amount Δ It can be expressed as:

[0073] (6)

[0074] The distance between the first connecting wall unit 11 and the fourth connecting wall unit 14 and the relative displacement between the second connecting wall unit 12 and the third connecting wall unit 13 are both zero.

[0075] In the second method, all the bevels and square connecting wall units in the structural unit will be affected by the force. Due to the symmetry of the structure, the effect of the force on each bevel is the same, and the effect of the force on each square wall is also the same. Take the first bevel 202a in the first connecting unit 21, such as Figure 6b As shown:

[0076] (7)

[0077] Where M2 is the bending moment of the first hypotenuse 202a, P is the lateral force of one end of the first hypotenuse 202a, C is the longitudinal force of one end of the first hypotenuse 202a, L is the length of the first hypotenuse 202a, and θ is half of the angle of the oblique side. P and G can be converted from stress:

[0078] (8)

[0079] (9)

[0080] Wherein σ1 represents the transverse stress, and σ2 represents the longitudinal stress. Taking the intersection of the first hypotenuse 2 202a and the first hypotenuse 4 204a as the reference point, the deflection δ3 of the intersection of the first hypotenuse 2 202a and the first hypotenuse 4 204a and the intersection of the first hypotenuse 1 201a and the first hypotenuse 3 203a can be obtained by the standard beam theory as follows:

[0081] (10)

[0082] Where Es represents the elastic modulus, I represents the second moment of inertia of the oblique edge. In this structure, the hole wall thickness is uniform, so I is taken as:

[0083] (11)

[0084] Wherein b represents the cell wall depth, and t represents the cell wall thickness. The deflection δ4 of the intersection of the fourth hypotenuse 202d and the fourth hypotenuse 4 204d, and the intersection of the fourth hypotenuse 1 201d and the fourth hypotenuse 3 203d is:

[0085] (12)

[0086] The displacement of the intersection of the first hypotenuse 2 202a and the first hypotenuse 4 204a, the first hypotenuse 1 201a and the first hypotenuse 3 203a can be expressed as:

[0087] (13)

[0088] The displacement of the intersection of the third hypotenuse 4 204c and the third hypotenuse 2 202c, the third hypotenuse 3 203c and the fourth hypotenuse 1 201d can be expressed as:

[0089] (14)

[0090] Among them The direction is horizontal to the right, and its magnitude is equal to Δ The values ​​are equal; the direction is vertically downward, and its modulus is equal to the value of δ3. Substituting P with C in formula (6), the distance between the first connecting wall unit 11 and the fourth connecting wall unit 14 and the distance between the second connecting wall unit 12 and the third connecting wall unit 13 can be obtained as follows: for:

[0091] (15)

[0092] The intersection of the second hypotenuse 4 204b and the second hypotenuse 2 202b, the displacement of the second hypotenuse 3 203b and the second hypotenuse 1 201b It can be expressed as:

[0093] (16)

[0094] The intersection of the fourth hypotenuse 202d and the fourth hypotenuse 4 204d, the displacement of the fourth hypotenuse 1 201d and the fourth hypotenuse 3 203d It can be expressed as:

[0095] (17)

[0096] Among them The direction is vertically downward, and its magnitude is equal to Δ The values ​​are equal; The direction is horizontal to the right, and its modulus is equal to the value of δ4. Therefore, after being subjected to forces in two directions at the same time, the overall center of the structure shrinks.

[0097] The structure 1 with bidirectional zero Poisson's ratio effect according to the embodiment of the present invention is composed of a plurality of structural units arranged in a grid shape, and its Poisson's ratio effect has no correlation with the Poisson's ratio of the material.

[0098] In the simulation of this embodiment, the selected matrix material is structural steel, and its performance parameters are: elastic modulus Es = 2 × 105 MPa, Poisson's ratio μ = 0.3, density ρ = 7850 kg / m 3 The geometric parameters of the unit cell model are: hypotenuse length L = 10 mm, angle between hypotenuse and horizontal line θ = 60°, cell wall depth b = 10 mm, length ratio α = 0.5, β = 0.05. The load is applied to the upper end of structure 1, and the lower end is a fixed constraint, see Figure 7 shown.

[0099] Through simulation calculation, it is found that when the applied stress is greater than 250MPa, the structure will experience severe deformation interference. Therefore, within the elastic limit, after the load is applied to the structure 1, the longitudinal force causes the angle between the first hypotenuse 1 201a and the first hypotenuse 3 203a, the angle between the first hypotenuse 2 202a and the first hypotenuse 4 204a, the angle between the third hypotenuse 1 201c and the third hypotenuse 3 203c, and the angle between the third hypotenuse 2 202c and the third hypotenuse 4 204c in the structure 1 to decrease, and the first connecting unit 21 and the third connecting unit 23 fold inward to produce deformation, while the angles of the hypotenuses in the second connecting unit 22 and the fourth connecting unit 24 remain unchanged. Therefore, when the structure 1 is subjected to longitudinal force, it does not produce deformation and contraction in the lateral direction, and the structure 1 presents a zero Poisson's ratio effect.

[0100] Figure 8 The figure shows the stability diagram of Poisson's ratio under different stresses based on finite element simulation. The average lateral strain ε of structure 1 under different stresses is obtained by using finite element analysis software. x and the average longitudinal strain ε y The negative value of the ratio is the Poisson's ratio ν of the structure under the stress, that is:

[0101] (18)

[0102] where ε x is the lateral strain of the structure, ε y is the longitudinal strain of the structure. The strain ε is calculated by the following formula:

[0103] (19)

[0104] in Indicates the amount of elongation (or shortening), In the process of calculating Poisson's ratio, because the structure 1 proposed by the present invention is strictly symmetrical and has a square shape, the length and width of the structural units constituting the structure 1 can be used It is expressed as:

[0105] (20)

[0106] Formula (18) can be transformed into:

[0107] (twenty one)

[0108] in represents the deformation in the horizontal direction, Represents the longitudinal deformation. Therefore, in the finite element simulation analysis process, the horizontal deformation under different stresses is calculated. and longitudinal deformation , the Poisson's ratio under different stresses can be obtained. As shown in Figure 6, within the elastic range, the Poisson's ratio always fluctuates around zero when different stresses are applied during compression, and finally stabilizes around 0.08, which has the characteristic of zero Poisson's ratio, and can still ensure the stability of Poisson's ratio when subjected to large stress changes.

[0109] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

Claims

1. A structure with bidirectional zero Poisson's ratio effect, characterized in that: Comprising a structural unit, the structural unit comprising: A connecting wall assembly, comprising four connecting wall units, wherein the cross-sectional profile of the connecting wall unit is a hollow square, and the four connecting wall units are arranged in a rectangular array; A connection assembly, comprising four connection units, wherein the four connection units are arranged in a circular array with the center of the connection wall assembly as the center, each connection unit is located between two adjacent connection wall units, and both ends of each connection unit are respectively connected to two adjacent connection wall units; The connection unit comprises a first hypotenuse, a second hypotenuse, a third hypotenuse and a fourth hypotenuse, wherein the first hypotenuse is parallel to the second hypotenuse, the third hypotenuse is parallel to the fourth hypotenuse, the first hypotenuse, the second hypotenuse, the third hypotenuse and the fourth hypotenuse are all equal in length, one end of the first hypotenuse is connected to one end of the third hypotenuse, and the connection unit is folded toward the center of the connection wall assembly; Among them, the side length of the connecting wall unit is H, the length of the hypotenuse 1 is L, the ratio of H to L is ɑ, and it satisfies: α>0.2; the thickness of the connecting wall unit is t, the ratio of t to L is β, and it satisfies: β<0.

1.

2. The structure with bidirectional zero Poisson's ratio effect according to claim 1, characterized in that: The α=0.

5.

3. The structure with bidirectional zero Poisson's ratio effect according to claim 1, characterized in that: The β=0.

05.

4. The structure with bidirectional zero Poisson's ratio effect according to claim 1, characterized in that: The angle between the first hypotenuse and the third hypotenuse is 2θ, which satisfies: 90°<2θ<180°.

5. The structure with bidirectional zero Poisson's ratio effect according to claim 4, characterized in that: The angle is equal to 120°.

6. The structure with bidirectional zero Poisson's ratio effect according to claim 1, characterized in that: The structure with bidirectional zero Poisson's ratio effect is formed by a rectangular array of structural units.

7. The structure with bidirectional zero Poisson's ratio effect according to any one of claims 1 to 6, characterized in that: The structure with bidirectional zero Poisson's ratio effect can be prepared by a sheet stacking method, a mold casting method, a rapid prototyping method, an extrusion molding method or a photocuring method.

8. A method for loading a structure having a bidirectional zero Poisson's ratio effect, comprising loading the structure having a bidirectional zero Poisson's ratio effect as claimed in any one of claims 1 to 7, characterized in that: The steps include: Apply uniaxial stress to the structural unit, and the stress acts on the edges of the connecting wall units on the left and right sides of the square structural unit; or The structural unit is subjected to bidirectional loading, and the stress acts on the edges of the connecting wall unit on the left, right and top of the structural unit.

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