Method for manufacturing out-of-plane form programmable structure based on distributed negative Poisson's ratio

Abstract

The invention discloses a manufacturing method of an out-of-plane form programmable structure based on a distributed negative Poisson's ratio, belongs to the field of intelligent construction and material design, and aims to solve the problems of high forming cost and complex process of a complex curved surface of a building. The method comprises the steps that on the basis of a target three-dimensional form, a functional unit array (a negative Poisson's ratio unit and a positive / negative Poisson's ratio unit combination) with the Poisson's ratio difference larger than or equal to 0.3 is designed in a two-dimensional plane, a two-dimensional plane prefabricated structure is integrally formed through additive manufacturing or mold casting, and materials in connecting areas between the units are continuous; low-friction sliding groove constraint (the friction coefficient is smaller than or equal to 0.1) is transversely applied to the prefabricated structure, the prefabricated structure is longitudinally stretched to the critical strain (epsilon c is larger than or equal to 5%), controllable buckling is induced under constraint through the transverse expansion effect of the negative Poisson's ratio unit, and finally the three-dimensional shape is fixed through adhesive curing or heat setting or mechanical fastening.

Description

Technical Field

[0001] The present invention relates to the field of intelligent materials and structural design, and specifically to a manufacturing method for realizing controllable buckling forming of a two-dimensional planar structure into a three-dimensional target form by regulating the distribution of traction metamaterials. The method is suitable for fields such as rapid prototyping of buildings. Technical Background

[0002] The demand for complex curved surfaces in architecture has evolved from functional needs to aesthetic needs and then to performance needs. In modern society, architectural design has gradually been endowed with uniqueness and iconic significance. Complex curved surfaces, with their unique formal language, have become an ideal choice for landmark buildings. Therefore, the problem of complex curved surface forming in the architectural field has become a key issue. However, the existing complex curved surface forming of buildings relies on prefabricated molds or on-site assembly, which has problems such as high cost, low adaptability (unable to respond to dynamic needs), and cracking caused by material mismatch. Although auxetic metamaterials have the characteristic of lateral expansion under tension, existing technologies only utilize their local deformation characteristics and fail to achieve global morphological programming through material distribution design. Summary of the Invention

[0003] In response to the development trend of the above-mentioned technical field, the present invention provides a method for manufacturing an out-of-plane morphology programmable structure based on a distributed negative Poisson's ratio, which realizes low-cost, high-precision controllable forming of a three-dimensional target morphology through the integrated manufacturing and constrained loading of a two-dimensional planar structure.

[0004] Note that the inclusion of these objectives does not preclude the existence of other objectives. One embodiment of the present invention does not necessarily achieve all of the above objectives. Objectives other than the above objectives may be extracted from the description of the specification, drawings, and claims.

[0005] The present invention achieves the above-mentioned purpose through the following technical means.

[0006] The technical solution of the present invention is:

[0007] Based on the morphology of the target three-dimensional structure, the two-dimensional plane is divided into multiple functional unit areas. The buckling response is controlled by designing the unit type, density, and connection area gradient. High curvature areas are densely packed with negative Poisson's ratio units, while low curvature areas are mixed with positive and negative Poisson's ratio units. The buckling response is controlled by designing the unit type, density, and connection area gradient.

[0008] Adopt additive manufacturing or mold casting to form a two-dimensional plane prefabricated structure to ensure the continuity of the material in the connection area between units;

[0009] The two-dimensional plane prefabricated structure is subjected to a chute constraint (friction coefficient ≤ 0.1) in the transverse direction and stretched longitudinally to a critical strain (ε c ≥5%), using constrained negative Poisson's ratio unit expansion to generate lateral compressive stress and induce controlled buckling;

[0010] Fix the three-dimensional shape after buckling by at least one of adhesive curing, heat setting or mechanical locking.

[0011] In one embodiment of the present invention, the functional unit material is thermoplastic polyurethane elastomer (TPU), and the manufacturing method includes:

[0012] Provide a method for arranging the functional units in the two-dimensional plane according to the three-dimensional target structure.

[0013] Use additive manufacturing means to form the two-dimensional plane prefabricated structure.

[0014] Apply a chute constraint transversely to the two-dimensional plane prefabricated structure, use a polytetrafluoroethylene-coated chute (coefficient of friction ≤ 0.1), and apply a longitudinal tension to the critical strain through a handle.

[0015] Fix the three-dimensional shape after buckling of the two-dimensional plane prefabricated structure by adhesive curing.

[0016] Further preferably, a manufacturing method for an out-of-plane shape programmable structure based on distributed negative Poisson's ratio includes the following steps:

[0017] Step 1, according to the shape of the target three-dimensional structure, obtain a two-dimensional plane through reverse design, and arrange at least two functional units with different Poisson's ratios in the two-dimensional plane in a periodic or non-periodic array. Among them, at least one of the Poisson's ratio υ1 of the first functional unit and the Poisson's ratio υ2 of the second functional unit is negative, and the absolute value difference of the Poisson's ratios of the two functional units is ≥ 0.3, and complete the layout of the two-dimensional plane.

[0018] Step 2, through additive manufacturing or mold forming process, perform integrated forming manufacturing according to the layout of the two-dimensional plane obtained in Step 1 to obtain a two-dimensional plane prefabricated structure.

[0019] Step 3, taking the width of the two-dimensional plane prefabricated structure as the X-axis and the length of the two-dimensional plane prefabricated structure as the Y-axis, apply chute constraints to both sides of the two-dimensional plane prefabricated structure along the X-axis. The chute constraints allow free sliding in the Y-axis direction but restrict displacement in the X-axis direction to obtain a constrained two-dimensional plane prefabricated structure.

[0020] Step 4, apply a tensile displacement load to the constrained two-dimensional plane prefabricated structure along the Y-axis direction to the critical strain ε c , utilize the X-axis direction expansion effect of the negative Poisson's ratio unit to generate a compressive stress in the X-axis direction under the chute constraint, induce the overall structure to buckle and become unstable, and the out-of-plane deformation is the target three-dimensional structure, and a stable three-dimensional structure is obtained through curing, which is an out-of-plane shape programmable structure based on distributed negative Poisson's ratio.

[0021] In Step 1, when the Poisson's ratio υ1 of the first type of functional unit is negative, the first type of functional unit adopts a periodic microstructure, and the periodic microstructure adopts a concave honeycomb, a rotating polygon configuration or a topological configuration.

[0022] In Step 1, when the Poisson's ratio υ2 of the second type of functional unit is negative, the second type of functional unit adopts a periodic microstructure, and the periodic microstructure adopts a concave honeycomb, a rotating polygon configuration or a topological configuration.

[0023] In Step 4, the critical strain ε c satisfies the relation:

[0024]

[0025] where σ cr is the buckling critical stress, E eff is the equivalent Young's modulus of the two-dimensional planar prefabricated structure, and σ cr is obtained by calculating the balance condition between the reaction force of the chute constraint and the lateral expansion stress of the negative Poisson's ratio unit.

[0026] In Step 4, the curing is adhesive curing, heat setting or mechanical locking.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. A building structure provided by the present invention can achieve a tensile buckling mode by utilizing the unique tensile expansion property of the negative Poisson's ratio structure. In addition to the innovation in the force application method, applying the out-of-plane buckling forming method to the building field can save more transportation and manufacturing costs in the early stage.

[0029] 2. The present invention controls the buckling wavelength, direction and wave crest height by changing the arrangement rule of the functional units;

[0030] 3. It supports mainstream additive manufacturing processes such as FDM and stereolithography, reducing the manufacturing cost.

[0031] Note that the description of these effects does not prevent the existence of other effects. One embodiment of the present invention does not necessarily have all the above effects. Other effects than the above can be obviously seen and extracted from the descriptions in the specification, drawings, claims, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a schematic diagram of the functional unit of the two-dimensional planar prefabricated structure according to an embodiment of the present invention.

[0033] Figure 2 is a schematic diagram of the two-dimensional planar prefabricated structure according to an embodiment of the present invention.

[0034] Figure 3Microscopic schematic diagram of the connection of functional units in an embodiment of the present invention (Poisson's ratio changes from -0.8 to 0.0 and Poisson's ratio changes from -0.4 to 0.0).

[0035] Figure 4 Schematic diagram of the principle of lateral buckling in an embodiment of the present invention.

[0036] Figure 5 Flowchart of the buckling forming process in an embodiment of the present invention.

[0037] Figure 6 Finite element simulation diagram in another embodiment of the present invention.

[0038] Figure 7 Application scenario diagram in another embodiment of the present invention.

[0039] In the figure: 1 - Negative Poisson's ratio unit with a Poisson's ratio of -0.8, 2 - Negative Poisson's ratio unit with a Poisson's ratio of -0.4, 3 - Negative Poisson's ratio unit with a Poisson's ratio of 0.0, 4 - Two-dimensional plane prefabricated structure, 5 - Connection of functional units with a negative Poisson's ratio of -0.8 and 0.0, 6 - Connection of functional units with a negative Poisson's ratio of -0.4 and 0.0, 7 - Rigid chute, 8 - Handle for applying longitudinal tensile displacement load. Specific embodiments

[0040] The following describes exemplary embodiments of the present application with reference to the accompanying drawings. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals indicate the same or similar elements or elements with the same or similar functions throughout. The embodiments described below by reference to the accompanying drawings are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

[0041] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "front", "rear", "left", "right", "upper", "lower", "axial", "radial", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying 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 construed as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality" means two or more, unless otherwise specifically defined.

[0042] In the present invention, unless otherwise clearly specified and defined, terms such as "installation", "connection", "linkage", "fixation" shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be a direct connection or an indirect connection through an intermediate medium, and it may be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0043] An embodiment of the present invention provides a manufacturing method for an out-of-plane shape programmable structure based on distributed negative Poisson's ratio.

[0044] As Figure 5 shown, the manufacturing method may include:

[0045] Providing a periodic or non-periodic array arrangement of each functional unit 1, 2, 3 in the two-dimensional planar prefabricated structure 4 as Figure 2 shown.

[0046] Integrally manufacturing the two-dimensional planar prefabricated structure 4 using an additive manufacturing method. Using thermoplastic polyurethane elastomer (TPU) material. Containing three functional units 1, 2, 3 with different Poisson's ratio values, the functional unit size is 5 mm, the functional unit thickness is 1 mm, and their Poisson's ratio values are υ = -0.8, υ = -0.4, υ = 0.0 respectively. The specific distribution method is as Figure 2 shown. The connection methods 5, 6 between the functional units are integrally formed using the same material under additive manufacturing, as Figure 3 shown.

[0047] Applying a constraint to the lateral displacement, installing a polytetrafluoroethylene-coated chute 7 (friction coefficient 0.08); applying a longitudinal tensile displacement load to a strain ε c = 8% through a displacement load application device 8, causing the two-dimensional planar prefabricated structure 4 to undergo lateral buckling and be out-of-plane formed into a target three-dimensional structure.

[0048] After forming, spraying a cyanoacrylate adhesive and ultraviolet curing for 10 seconds to fix the buckled target three-dimensional structure, and the target three-dimensional structure before release can still be maintained after the load is released.

[0049] The following is another embodiment of the present invention, which can be applied to the rapid prototyping of complex curved roofs in the field of house construction. The specific application scenario is as Figure 7 shown. Providing as Figure 6The arrangement of the two-dimensional planar prefabricated structure shown is numerically simulated and analyzed using the commercial finite element software ABAQUS. The material used is high-strength steel with a relative density of 7.9, a Poisson's ratio υ = 0.3, an elastic modulus E = 206 GPa, and a yield stress of 460 MPa. The planar size of the two-dimensional planar prefabricated structure is 4 m × 6 m, and the thickness is 0.068 m. The functional units adopt the configurations shown in Figures 1 and 3, with a unit size of 1 m and a unit thickness of 0.068 m. The specific distribution method is as shown in Figure 6 shown.

[0050] The finite element analysis is divided into two stages: linear buckling analysis and nonlinear buckling analysis. In the linear buckling analysis stage, the buckling mode of this configuration is obtained and applied as a defect to the subsequent nonlinear buckling analysis. In the nonlinear buckling analysis, after applying a tensile displacement load in the Y-axis direction, it is fixed and a Z-direction load is applied in the middle of the formed surface to test the load-bearing capacity of the programmable structure as a roof structure.

[0051] In step one of the ABAQUS finite element analysis, rigid chute constraints are applied to both sides of the X-axis of the finite element model, and the application method is U1 = U3 = UR1 = UR2 = UR3 = 0; constraints and displacement loads of tensile forces in opposite directions are applied to both sides of the Y-axis, and the application method is U1 = U3 = UR1 = UR2 = UR3 = 0, and the displacement loads of tensile forces in opposite directions applied to the bottom and the top are U2 = 1. After performing the linear buckling analysis, the first buckling mode is extracted, and an initial geometric defect is introduced at a ratio of 1 / 300. An 8% tensile strain load in opposite directions is applied to the bottom and the top along the Y-axis. After the application is completed, the target three-dimensional structure is fixed by mechanical locking (fixed boundary conditions), and a Z-direction concentrated load is applied in the middle of the target three-dimensional structure to obtain Figure 6 the load-displacement curve shown in. Among them, the abscissa of the load-displacement curve graph is the mid-span deflection of the plate member, and the ordinate represents the magnitude of the concentrated load applied at the mid-span. According to the "Load Code for Building Structures" GB 50009-2012, the mid-span deflection being below 1 / 250 is the safe use condition; when the mid-span deflection is 1 / 250, the load that can be borne obtained from the load-displacement curve is 14.285 kN, showing good load-bearing capacity. Therefore, this manufacturing method can be well applied in the field of rapid roof manufacturing.

[0052] At present, the processing methods for complex curved surfaces in the field of intelligent construction are not yet perfect, and it is difficult to quickly form a building structure with complex curved surfaces. The present invention combines the unique tensile expansion property of the negative Poisson's ratio structure with the out-of-plane buckling forming technology. By designing the distribution of the negative Poisson's ratio functional units in the two-dimensional plane prefabricated structure of the target three-dimensional structure, a programmable structure manufacturing method based on the distributed negative Poisson's ratio out-of-plane morphology is obtained. In addition to the innovation in the force application method, applying the out-of-plane buckling forming method to the construction field can save more on transportation and manufacturing costs in the early stage. By adopting the design of variable Poisson's ratio and changing the negative Poisson's ratio of the functional units that make up the two-dimensional plane prefabricated structure, a distributed design of different-sized negative Poisson's ratio units in the two-dimensional structure is realized, enabling the building surface to achieve the complex curved surface required by the design under the out-of-plane buckling morphology.

[0053] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention. In addition, it should be understood that although this specification is described according to the embodiments, not every embodiment only contains an independent technical solution. This narrative method of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A manufacturing method for an out-of-plane morphologically programmable structure based on distributed negative Poisson's ratio, characterized in that, It includes the following steps: Step 1: According to the shape of the target three-dimensional structure, a two-dimensional plane is obtained through reverse design. At least two functional units with different Poisson's ratios are arranged in a periodic or non-periodic array within the two-dimensional plane. Among them, at least one of the Poisson's ratio υ1 of the first functional unit and the Poisson's ratio υ2 of the second functional unit is negative, and the absolute value difference of the Poisson's ratios of the two functional units is ≥ 0.3, and the arrangement of the two-dimensional plane is completed; Step 2: Through additive manufacturing or mold forming process, integral forming manufacturing is carried out according to the arrangement of the two-dimensional plane obtained in Step 1 to obtain a two-dimensional plane prefabricated structure; Step 3: Taking the width of the two-dimensional plane prefabricated structure as the X-axis and the length of the two-dimensional plane prefabricated structure as the Y-axis, a chute constraint is applied to both sides of the two-dimensional plane prefabricated structure along the X-axis. The chute constraint allows free sliding along the Y-axis but restricts displacement along the X-axis to obtain a constrained two-dimensional plane prefabricated structure; Step 4: Apply a tensile displacement load to the constrained two-dimensional planar prefabricated structure along the Y-axis direction until the critical strain ε c , utilize the X-axis direction expansion effect of the negative Poisson's ratio unit to generate a compressive stress in the X-axis direction under the constraint of the chute, induce the buckling instability of the overall structure, and the out-of-plane deformation is the target three-dimensional structure. Then, obtain a stable three-dimensional structure through curing, which is the out-of-plane morphology programmable structure based on distributed negative Poisson's ratio.

2. The manufacturing method of the out-of-plane morphology programmable structure based on distributed negative Poisson's ratio according to claim 1, wherein, In Step 1, when the Poisson's ratio υ1 of the first functional unit is negative, the first functional unit adopts a periodic microstructure, and the periodic microstructure adopts a concave honeycomb, a rotating polygon configuration or a topological configuration.

3. The manufacturing method of the out-of-plane shape programmable structure based on distributed negative Poisson's ratio according to claim 1, wherein In Step 1, when the Poisson's ratio υ2 of the second functional unit is negative, the second functional unit adopts a periodic microstructure, and the periodic microstructure adopts a concave honeycomb, a rotating polygon configuration or a topological configuration.

4. The manufacturing method of an out-of-plane morphology programmable structure based on distributed negative Poisson's ratio according to claim 1, wherein In Step 4, the critical strain ε c satisfies the relational expression: Among them, σ cr is the buckling critical stress, E eff is the equivalent Young's modulus of the two-dimensional planar prefabricated structure, and σ cr is obtained by calculating the equilibrium condition between the chute constraint reaction force and the transverse expansion stress of the negative Poisson's ratio unit.

5. The manufacturing method of the out-of-plane morphology programmable structure based on distributed negative Poisson's ratio according to claim 1, wherein, In Step 4, the curing is adhesive curing, heat setting or mechanical locking.

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