A variable stiffness negative Poisson's ratio cell and its design method
By designing the variable stiffness negative Poisson ratio cell, adjusting the material distribution and rotation angle, the problem of the adjustability of the dense point of the negative Poisson ratio material during compression is solved, and the variable stiffness and performance optimization of the structure is achieved, suitable for anti-collision , shock-resistant and buffering applications.
Patent Information
- Application Number
- CN202110039640.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2021-01-13
- Publication Date
- 2024-12-17
- Estimated Expiration
- 2041-01-13
AI Technical Summary
The existing negative Poisson ratio materials are difficult to achieve the controllability of dense points when compressed, limiting their performance optimization in collision-proof, shock-resistant and buffering applications.
By designing variable stiffness negative Poisson's ratio cell, including variable stiffness elliptical and concave hexagonal cell, the material distribution and rotation angle of the design area are adjusted and different variable stiffness proportional factors are set to achieve the negative Poisson's ratio structure. The compactness can be adjusted.
The variable stiffness point controllability of the negative Poisson ratio structure is achieved, which enhances its performance in anti-collision, shock resistance, buffering and sensor devices, and can make various forms of negative Poisson ratio structures, such as tubular and cube structures. .
Smart Images
Figure CN112699589B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of new materials, and in particular to a variable stiffness negative Poisson's ratio cell and a design method thereof. Background Art
[0002] Poisson's ratio ν is named after the French scientist Poisson, also known as the lateral deformation coefficient, which is used to characterize the lateral deformation characteristics perpendicular to the direction of the force. Negative Poisson's ratio materials have opposite deformation characteristics to traditional positive Poisson's ratio materials. They expand laterally when subjected to axial tension and contract laterally when subjected to axial compression. In 1987, Lakes first proposed artificial negative Poisson's ratio materials in Science, making polyurethane foam into tensile and compressive negative Poisson's ratio foam. Since then, a large number of negative Poisson's ratio materials have emerged, such as concave structures, rotated polygonal structures, chiral structures, sheet-like pleated structures, perforated plate structures, etc.
[0003] With the rapid development of negative Poisson's ratio metamaterials in recent years, more and more negative Poisson's ratio structures with specific properties have been designed, such as adjustable negative Poisson's ratio, adjustable stiffness cells, etc. The design method of variable stiffness cells described in this paper is based on the above negative Poisson's ratio cells, controls the material in the deformation area, changes the material distribution in the design area, and makes the density point of the negative Poisson's ratio hole structure adjustable. Summary of the invention
[0004] The present invention proposes a variable stiffness negative Poisson's ratio cell and a design method thereof, wherein a variable stiffness ratio (stiffness proportional factor) is set according to a compression density point required by a designer, and a negative Poisson's ratio cell that meets the requirements is designed on the basis of an original negative Poisson's ratio cell, thereby achieving the controllability of a variable stiffness point (i.e., a density point).
[0005] The technical solution adopted by the present invention is: a variable stiffness negative Poisson's ratio cell, including a variable stiffness negative Poisson's ratio elliptical cell and a variable stiffness negative Poisson's ratio concave hexagonal cell;
[0006] The variable stiffness negative Poisson's ratio cell is divided into a variable stiffness design area and a deformation area; the material distribution in the deformation area is kept unchanged, and different variable stiffness scale factors (VariableScale Factor) are set by increasing the material distribution in the variable stiffness design area to achieve the controllability of the variable stiffness point;
[0007] The major and minor axes of the variable stiffness negative Poisson's ratio elliptical cell are represented by a and b respectively, and the ratio of the minor axis to the major axis satisfies 0.
[0008] The rotation center point of the design area of the variable stiffness negative Poisson's ratio elliptical cell is the center point of the elliptical cell, the midpoint of the short rib between adjacent ellipses, the quarter point at the major axis of the ellipse, and the intersection of the line connecting the quarter points of the major and minor axes of the ellipse and the straight line parallel to the major semi-axis and at a distance of h. The maximum rotation angle θ and the variable stiffness rotation angle θ1 satisfy the following ranges:
[0009]
[0010] The variation range of the variable stiffness scale factor (VSF) value of the design area of the variable stiffness negative Poisson's ratio elliptical cell satisfies:
[0011]
[0012] The relationship between the design area height h1 value of the variable stiffness negative Poisson's ratio concave hexagonal cell and the half value c of the concave cell height satisfies:
[0013] The range of the concave angle θ of the variable stiffness negative Poisson's ratio concave hexagonal cell satisfies: 0≤θ≤90°;
[0014] The range of the variable stiffness rotation angle θ1 of the variable stiffness negative Poisson's ratio concave hexagonal cell satisfies:
[0015]
[0016] The variation range of the variable stiffness scale factor (VSF) value of the design area of the variable stiffness negative Poisson's ratio concave hexagonal cell satisfies:
[0017]
[0018] Preferably, the ratio of the semi-major axis a and the semi-minor axis b of the variable stiffness negative Poisson's ratio elliptical cell is 0.2
[0019] Preferably, the height h of the design area of the variable stiffness negative Poisson's ratio elliptical cell is b / 8 <h<b / 3。
[0020] Preferably, the range of the height h1 value of the design area of the variable stiffness negative Poisson's ratio concave hexagonal cell is
[0021] The variable stiffness negative Poisson's ratio cell design method comprises the following steps:
[0022] 1) According to the type of negative Poisson's ratio cell, determine the geometric construction parameters of the original negative Poisson's ratio cell;
[0023] 2) Determine the deformation modes of different cells during compression and their cell rotation mechanisms;
[0024] 3) Determine the variable stiffness design area and deformation area through the compression and rotation methods of different cells;
[0025] 4) Determine the rotation center point that meets the compression rotation in the design area, and take the ratio of the variable stiffness rotation angle θ1 to the maximum rotation angle θ as VSF, i.e., variable stiffness proportional factor;
[0026] 5) The designed variable stiffness negative Poisson's ratio cells are arranged or rotated in two or three dimensions to form negative Poisson's ratio structures of different forms.
[0027] In the variable stiffness negative Poisson's ratio cell design method, the variable stiffness rotation angle θ1 is applicable to the variable stiffness design of different negative Poisson's ratio cells, the difference is that the deformation area distribution of different cells is different, so the angle position of the variable stiffness rotation angle θ1 is different;
[0028] The variable stiffness design method of the negative Poisson's ratio cell of the present invention is applicable to negative Poisson's ratio cells such as horizontally and vertically crossed elliptical structures, concave structures, chiral structures, and anti-chiral structures.
[0029] Beneficial effects: The design method of a variable stiffness negative Poisson's ratio cell of the present invention divides the above-mentioned cell into a variable stiffness design area and a deformation area according to the deformation mechanism during compression; by changing the material distribution of the variable stiffness design area of the negative Poisson's ratio cell, the density point of the negative Poisson's ratio structure is quantitatively controlled, thereby realizing the variable stiffness of the structure. The variable stiffness negative Poisson's ratio structure of the present invention can be made into anti-collision, anti-seismic, buffer blocks and other buffer energy absorption and sensor devices; the variable stiffness negative Poisson's ratio structure of the present invention can be made into a negative Poisson's ratio tubular structure and a three-dimensional cubic structure. BRIEF DESCRIPTION OF THE DRAWINGS
[0030] Figure 1-4 Schematic diagram of designing different rotation centers for variable stiffness negative Poisson's ratio elliptical cells;
[0031] Figure 5 Schematic diagram of variable stiffness design of concave hexagonal cell with negative Poisson's ratio;
[0032] Figure 6-9 The two-dimensional and three-dimensional circular tube arrangement diagrams of elliptical cells and concave hexagonal cells. DETAILED DESCRIPTION
[0033] The present invention is further described below in conjunction with specific embodiments and accompanying drawings:
[0034] A variable stiffness negative Poisson's ratio cell, including a variable stiffness negative Poisson's ratio elliptical cell and a variable stiffness negative Poisson's ratio concave hexagonal cell;
[0035] The variable stiffness negative Poisson's ratio cell is divided into a variable stiffness design area and a deformation area; the material distribution in the deformation area is kept unchanged, and different variable stiffness scale factors (VariableScale Factor) are set by increasing the material distribution in the variable stiffness design area to achieve the controllability of the variable stiffness point;
[0036] The major and minor axes of the variable stiffness negative Poisson's ratio elliptical cell are represented by a and b respectively, and the ratio of the minor axis to the major axis satisfies 0.2.
[0037] The rotation center point of the design area of the variable stiffness negative Poisson's ratio ellipse cell is taken as the center point of the ellipse cell, the midpoint of the short rib between adjacent ellipses, the quarter point at the major axis of the ellipse, and the intersection point of the line connecting the quarter points of the major and minor axes of the ellipse and the straight line parallel to the major semi-axis and with a distance h (such as Figure 1-4 ), the maximum rotation angle θ and the variable stiffness rotation angle θ1 vary in the range of:
[0038]
[0039] The variation range of the variable stiffness scale factor (VSF) value of the design area of the variable stiffness negative Poisson's ratio elliptical cell satisfies:
[0040]
[0041] like Figure 5 As shown, the relationship between the design area height h1 value of the variable stiffness negative Poisson's ratio concave hexagonal cell and the half value c of the concave cell height satisfies: The range of the concave angle θ of the variable stiffness negative Poisson's ratio concave hexagonal cell satisfies: 0≤θ≤90°; the range of the variable stiffness rotation angle θ1 of the variable stiffness negative Poisson's ratio concave hexagonal cell satisfies:
[0042]
[0043] The variation range of the variable stiffness scale factor (VSF) value of the design area of the variable stiffness negative Poisson's ratio concave hexagonal cell satisfies:
[0044]
[0045] The variable stiffness negative Poisson's ratio cell design method comprises the following steps:
[0046] 1) According to the type of negative Poisson's ratio cell, determine the geometric construction parameters of the original negative Poisson's ratio cell;
[0047] 2) Determine the deformation modes of different cells during compression and their cell rotation mechanisms;
[0048] 3) Determine the variable stiffness design area and deformation area through the compression and rotation methods of different cells;
[0049] 4) Determine the rotation center point that meets the compression rotation in the design area, and take the ratio of the variable stiffness rotation angle θ1 to the maximum rotation angle θ as VSF, i.e., variable stiffness proportional factor;
[0050] 5) Arrange or rotate the designed variable stiffness negative Poisson's ratio cells in two or three dimensions to form different forms of negative Poisson's ratio structures. (e.g. Figure 6-9 )
[0051] It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, any anti-collision, anti-vibration, buffer block and other buffer energy absorption and sensor devices made of any variable stiffness negative Poisson's ratio structure are within the protection scope of this patent; any variable stiffness negative Poisson's ratio structure made into a negative Poisson's ratio tubular structure, a three-dimensional cubic structure, etc. are all within the protection scope of this patent; any negative Poisson's ratio structure designed by the variable stiffness design method and not listed in this article are all within the protection scope of this patent.
Claims
1. A design method for a variable stiffness negative Poisson's ratio cell, characterized by: The following steps are involved: 1) According to the type of negative Poisson's ratio cell, determine the geometric construction parameters of the original negative Poisson's ratio cell; 2) Determine the deformation modes of different cells during compression and their cell rotation mechanisms; 3) Determine the variable stiffness design area and deformation area through the compression and rotation methods of different cells; 4) Determine the rotation center point that meets the compression rotation in the design area, and take the ratio of the variable stiffness rotation angle to the maximum rotation angle as the variable stiffness proportional factor VSF value; 5) Arrange or rotate the designed variable stiffness negative Poisson's ratio cells in two or three dimensions to form negative Poisson's ratio structures of different forms; The variable stiffness negative Poisson's ratio cell includes a variable stiffness negative Poisson's ratio elliptical cell and a variable stiffness negative Poisson's ratio concave hexagonal cell; the variable stiffness negative Poisson's ratio cell is divided into a variable stiffness design area and a deformation area; The major and minor axes of the variable stiffness negative Poisson's ratio elliptical cell are represented by a and b respectively, and the ratio of the minor axis to the major axis satisfies 0. The rotation center point of the design area of the variable stiffness negative Poisson's ratio elliptical cell is the center point of the elliptical cell, the midpoint of the short rib between adjacent ellipses, the quarter point at the major axis of the ellipse, and the intersection of the line connecting the quarter points of the major and minor axes of the ellipse and the straight line parallel to the major axis and at a distance of h. The maximum rotation angle θ of the variable stiffness negative Poisson's ratio elliptical cell and the variable stiffness rotation angle θ1 of the variable stiffness negative Poisson's ratio elliptical cell satisfy the following variation ranges: The variation range of the variable stiffness proportional factor VSF value of the design area of the variable stiffness negative Poisson's ratio elliptical cell satisfies: The range of the concave angle θ2 of the variable stiffness negative Poisson's ratio concave hexagonal cell satisfies: 0≤θ2≤90°; The relationship between the design area height h1 value of the variable stiffness negative Poisson's ratio concave hexagonal cell and the half value c of the concave cell height satisfies: The range of the variable stiffness rotation angle θ1′ of the variable stiffness negative Poisson's ratio concave hexagonal cell satisfies: The variation range of the variable stiffness proportional factor VSF value of the design area of the variable stiffness negative Poisson's ratio concave hexagonal cell satisfies: The ratio of the short semi-axis to the long semi-axis of the variable stiffness negative Poisson's ratio elliptical cell satisfies 0.2 <b / a<0.9。 2. The design method of a variable stiffness negative Poisson's ratio cell according to claim 1, characterized in that: 3. The design method of a variable stiffness negative Poisson's ratio cell according to claim 2, characterized in that: The range of the height h1 value of the design area of the variable stiffness negative Poisson's ratio concave hexagonal cell is