A low thermal expansion coefficient adjustable Poisson's ratio element based on a triangular arrow structure Invar alloy basic unit and its preparation method and application

Abstract

The present invention discloses a low thermal expansion coefficient and adjustable Poisson's ratio element based on a triangular arrow structure Invar alloy basic unit, as well as its preparation method and application. The element is obtained by forming a plane obtained by a quadruple rotation array of triangular arrow structure Invar alloy basic units, removing the overlapping parts, and then connecting them through spatial curling; the basic unit is composed of a triangle and an inward concave structure located at any vertex thereof, and the whole is an axisymmetric structure. The element uses Invar alloy as a single-component raw material, and realizes the regulation of the Poisson's ratio of the element through the triangular arrow structure design, and finally realizes the integration of low thermal expansion coefficient and adjustable Poisson's ratio, effectively solving the problem of using multi-component materials for low thermal expansion coefficient and adjustable Poisson's ratio elements in the prior art. It can be integrally formed by a laser powder bed melting process, with a simple process, strong overall shape, and convenient industrial production, which can meet the performance requirements of star-sensitive satellite brackets.

Description

Technical Field

[0001] The present invention relates to an adjustable Poisson's ratio element, in particular to a low thermal expansion coefficient adjustable Poisson's ratio element based on a triangular arrow structure Invar alloy basic unit, and a preparation method and application thereof, belonging to the technical field of special alloy design and preparation. Background Art

[0002] Porous structures, as specialized structures composed of a large number of micropores, typically exhibit excellent lightweight properties. Cylindrical shells, a typical type of porous structure, are widely used in engineering applications such as the automotive, aerospace, and biomedical industries due to their excellent mechanical properties and lightweight performance. Systematic design of their microporous structure allows for customized functionality, such as thermal insulation, noise reduction, vibration damping, energy absorption, negative thermal expansion coefficients, and negative Poisson's ratios. The thermal expansion coefficient is often used to assess the deformation of solid materials / structures under temperature fluctuations. Conventional structures / materials typically exhibit a positive thermal expansion coefficient, meaning they expand with heat and contract with cold. This property often negatively impacts structural components in various aerospace applications. For example, star-sensing satellites operate under temperature fluctuations for extended periods of time, and their structural components undergo significant shape changes under temperature fluctuations, affecting the satellite's deflection angle and reducing signal transmission accuracy. Cylindrical shells with low thermal expansion coefficients can minimize thermal deformation of structural components, ensuring their operational accuracy. Furthermore, the Poisson's ratio is a physical parameter that describes the shape change of solid materials / structures in orthogonal directions under mechanical loading. Common materials and structures exhibit a positive Poisson's ratio, meaning they contract and deform transversely when subjected to longitudinal tensile loads. This deformation often affects the assembly accuracy of components in star-sensing satellites. However, cylindrical shell structures with a zero Poisson's ratio maintain dimensional stability in the orthogonal direction when subjected to unidirectional loads, ensuring the dimensional accuracy of structural components to the greatest extent possible. Therefore, cylindrical shell structures with a low thermal expansion coefficient and a zero Poisson's ratio have extremely high application value.

[0003] Existing cylindrical shell structures achieve low thermal expansion coefficients and zero Poisson's ratios by integrating and manipulating the thermal expansion coefficient and Poisson's ratio. However, existing cylindrical shell structures can only achieve this by integrating multiple component materials, which undoubtedly poses significant challenges in fabrication and severely restricts their practical engineering applications. Invar alloy offers an effective solution to these challenges. Invar alloy is an iron-nickel alloy with a nickel content of 36 wt%. Due to the Invar effect, it exhibits an extremely low thermal expansion coefficient (≤2.0 ppm / °C) below the Curie temperature (230°C). Thanks to its low laser reflectivity, the established laser powder bed fusion (PBF-LB) process provides a reliable fabrication process for the integrated fabrication of Invar alloy and its complex structural components. Therefore, using Invar alloy as a component material for cylindrical shell structures inherits Invar alloy's inherent low thermal expansion coefficient while avoiding the extremely low manufacturability associated with multiple component materials. Furthermore, the Poisson's ratio can be manipulated through structural design, ultimately achieving the integration of low thermal expansion coefficient and a controllable Poisson's ratio. The cylindrical shell structure designed in this invention achieves low thermal expansion and a controllable Poisson's ratio from negative to positive while ensuring high manufacturability. This improves the performance of structural components under long-term service conditions involving coupled temperature and force fields. For example, this structure can be used as a support for star-sensing satellites. Under the coupled effects of force and temperature, the low thermal expansion coefficient and zero Poisson's ratio provide the satellite with extremely high dimensional stability, thereby ensuring the accuracy of its information transmission. Summary of the Invention

[0004] In response to the problems existing in the prior art, the first object of the present invention is to provide a low thermal expansion coefficient and adjustable Poisson's ratio element based on the triangular arrow structure Invar alloy basic unit. The element uses Invar alloy as a single-component raw material and realizes the regulation of the Poisson's ratio of the element through the triangular arrow structure design, ultimately realizing the integration of low thermal expansion coefficient and adjustable Poisson's ratio, effectively solving the problem of low thermal expansion coefficient and adjustable Poisson's ratio elements using multi-component materials in the prior art.

[0005] The second object of the present invention is to provide a method for preparing a low thermal expansion coefficient and adjustable Poisson's ratio element based on a triangular arrow structure Invar alloy basic unit. This method utilizes the low laser reflectivity of Invar alloy and adopts a laser powder bed melting process to carry out integrated additive manufacturing of a cylindrical shell porous structure. This method has a simple processing technology, which helps to ensure the integrity of the structure on the one hand, and can also realize large-scale industrial production on the other hand.

[0006] A third objective of the present invention is to provide a low-thermal-expansion-coefficient, adjustable Poisson's ratio component based on a triangular-arrow-shaped Invar alloy unit cell for use in star-sensing satellite mounts. By analyzing the deformation behavior of the unit cell, formed by combining an indented structure and a triangle, a theoretical formula for the adjustable Poisson's ratio was derived. This quantitative correlation between various geometric parameters and the Poisson's ratio was established, enabling precise design of components that meet the requirements of star-sensing satellite mounts based on actual needs.

[0007] To achieve the above technical objectives, the present invention provides a low thermal expansion coefficient and adjustable Poisson's ratio element based on a triangular arrow structure Invar alloy basic unit. The triangular arrow structure Invar alloy basic unit is formed by four-fold rotation of the plane obtained by the array, removing the overlapping parts, and then connecting them by spatial curling.

[0008] The basic unit consists of a triangle and an inward-concave structure located at any vertex thereof, and the overall structure is an axisymmetric structure; the inward-concave structure consists of two inner oblique rods with a length of L1 extending from the vertices of the triangle and two outer oblique rods with a length of L3 connecting the extended end points of the inner oblique rods and the symmetry axis of the basic unit; the triangle consists of two oblique rods of L2 connected to the inward-concave structure and a bottom rod with a length of L4.

[0009] The concave structure contained in the basic unit provided by the present invention has the characteristic of adjustable Poisson's ratio, and is also the basis for realizing adjustable Poisson's ratio of the basic unit and the elements composed of the basic unit; when a tensile / compressive load is applied along the symmetry axis of the basic unit, the concave structure expands / contracts, causing the basic unit as a whole to expand / contract along the orthogonal direction of its symmetry axis; therefore, by adjusting the angle between the above-mentioned oblique rods, the deformation amount of the basic unit along the orthogonal direction of its symmetry axis can be controlled, thereby realizing the control of Poisson's ratio.

[0010] As a preferred solution, the quadruple rotation array is formed by taking the vertex formed by the concave structure in the basic unit as the rotation center, and after quadruple rotation, the vertices are connected to the cells, and then arranged periodically to obtain;

[0011] Alternatively, the base vertex of the triangle in the basic unit is used as the rotation center. After four rotations, the base connecting the cells is obtained, and then the cells are arranged periodically to obtain the result.

[0012] The planes constructed by the above two methods are derived from the same basic unit, and both have the characteristic of adjustable Poisson's ratio. Among them, with the triangular base vertex of the basic unit as the rotation center, the base-connected cell obtained after four-fold rotation can densely pack more cells within the unit area of ​​the plane. Therefore, this method has better dense packing characteristics, and the planar structure obtained after arraying also has higher density and stiffness.

[0013] As a preferred solution, in the concave structure of the basic unit, the angle between the inner oblique rod and the symmetry axis of the basic unit is θ1, the angle between the outer oblique rod and the symmetry axis of the basic unit is θ3, and the angle between the triangular oblique rod and the symmetry axis of the basic unit is θ2.

[0014] As a preferred solution, each diagonal rod and bottom rod in the basic unit is a square cross-section rod with a thickness of t.

[0015] As a preferred solution, the space curling is carried out by curling and connecting using the orthogonal vector of the plane normal vector obtained by the four-fold rotation arrangement as the central axis.

[0016] As a preferred solution, the geometric constraints of the angles θ1 to θ3 are: 45°<θ1<90°, 0°<θ2<θ1, θ3=45°.

[0017] As a preferred solution, the length constraint condition of the inner oblique rod and the triangular oblique rod is: L1cosθ1 <L2cosθ2,t / L1≤0.1。

[0018] The geometric constraints of the basic unit provided by the present invention must be strictly implemented in accordance with the above requirements. If the basic unit structure does not meet the above requirements, it will lead to overlapping and crossing of the rods, and will not be able to perform quadruple rotation and subsequent periodic arrays.

[0019] As a preferred solution, the Poisson's ratio of the element is the inverse of the ratio of radial strain to axial strain when the element is subjected to stress loading. The specific calculation process is:

[0020] Formula 1: ;

[0021] In formula 1: ν represents Poisson's ratio, and denote radial strain and axial strain, respectively.

[0022] As a preferred solution, when the cell is a vertex-connected cell or a bottom-edge-connected cell, the Poisson's ratio calculation process of the resulting element is:

[0023] Formula 2: ;

[0024] Formula 3: ;

[0025] Formula 4: ;

[0026] Formula 5: ;

[0027] Equations 2 to 4 are the calculation process parameters of Equation 5, which are dimensionless coefficients with no actual physical meaning. In Equation 5: and They represent the Poisson's ratio of the components obtained by connecting cells at the vertex and cells at the bottom.

[0028] The present invention also provides a method for preparing a low thermal expansion coefficient and adjustable Poisson's ratio element based on a triangular arrow structure Invar alloy basic unit, the process of which is: Invar alloy powder is integrally formed through a laser powder bed melting process to obtain the element.

[0029] The present invention also provides an application of a low thermal expansion coefficient adjustable Poisson's ratio element based on a triangular arrow structure Invar alloy basic unit, which is used for a star-sensing satellite bracket.

[0030] Compared with the prior art, the beneficial technical effects of the technical solution of the present invention are:

[0031] 1) The element provided by the present invention uses Invar alloy as a single-component raw material, and realizes the regulation of the Poisson's ratio of the element through a triangular arrow structure design, ultimately achieving the integration of a low thermal expansion coefficient and a controllable Poisson's ratio, effectively solving the problem of using multi-component materials in the existing technology for controllable Poisson's ratio elements.

[0032] 2) The preparation method provided by the present invention utilizes the low laser reflectivity of Invar alloy and adopts a laser powder bed melting process to carry out integrated additive manufacturing of cylindrical shell porous structures. This method has a simple processing technology, which helps to ensure the integrity of the structure on the one hand and can also realize large-scale industrial production on the other hand.

[0033] 3) The technical solution provided by the present invention is composed of a concave structure and a triangle to form a basic unit. By analyzing its deformation behavior, a theoretical formula for the adjustable Poisson's ratio is derived, and a quantitative correlation between various geometric parameters and the Poisson's ratio value is established. This allows for the precise design of components that meet the requirements of star-sensing satellite brackets based on actual needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the design method in the content of the invention and the technical solutions in the embodiments, the following briefly describes the drawings required for use in the content of the invention and the embodiments.

[0035] Figure 1 Schematic diagram of the highly manufacturable integrated low thermal expansion coefficient and adjustable Poisson's ratio cylindrical shell structure and design method provided by the present invention.

[0036] Figure 2 Images of the Poisson's ratio of two cylindrical shell structures provided by the present invention changing with angle.

[0037] Figure 3 Six cylindrical shell structures designed in the embodiment of the present invention

[0038] Figure 4This is a numerical verification diagram for achieving a low thermal expansion coefficient provided in an embodiment of the present invention.

[0039] Figure 5 This is a numerical verification diagram for implementing the Poisson's ratio control design provided in an embodiment of the present invention.

[0040] Figure 6 This is an experimental verification diagram of the design for achieving low thermal expansion coefficient and Poisson's ratio control provided in an embodiment of the present invention;

[0041] Reference numerals:

[0042] 1-Triangular arrow basic unit; 2-Type A cell; 3-Type B cell; 4-Type A plane lattice structure; 5-Type B plane lattice structure; 6-AC type configuration; 7-BC type configuration; 8-ACN cylindrical shell structure; 9-ACZ cylindrical shell structure; 10-ACP cylindrical shell structure; 11-BCN cylindrical shell structure; 12-BCZ cylindrical shell structure; 13-BCP cylindrical shell structure. DETAILED DESCRIPTION

[0043] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. It is obvious that the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making any creative ideas are within the scope of protection of the present invention.

[0044] Example 1

[0045] The present invention provides a low thermal expansion coefficient adjustable Poisson's ratio element based on a triangular arrow structure Invar alloy basic unit, which requires a thermal expansion coefficient of α c ≤2.0ppm / °C, Poisson's ratio and The adjustable range is -0.5~+0.5, and the specific process is:

[0046] The element is obtained by quadruple-rotating the plane of the triangular arrow-shaped Invar alloy basic unit, removing the overlapping parts, and then connecting them through spatial curling;

[0047] The basic unit is composed of a triangle and an inward concave structure at any vertex thereof, and the whole is an axisymmetric structure; the inward concave structure is composed of two inner oblique rods with a length of L1 extending from the vertex of the triangle and two outer oblique rods with a length of L3 connecting the end points of the inner oblique rods and the symmetry axis of the basic unit; the triangle is composed of two oblique rods with a length of L2 connected to the inward concave structure and a bottom rod with a length of L4; the thermal expansion coefficient of the Invar alloy is α c ≤2.0ppm / °C.

[0048] According to the differences in the rotation array method during the design process, two types of configuration elements are designed in this embodiment, named AC-type configuration and BC-type configuration respectively. For the AC configuration, taking the vertex of the concave structure of the triangular arrow structure as the rotation center, the vertex-connected cell is obtained through quadruple rotation, and then the corresponding plane is obtained through array, denoted as the A-type plane lattice structure. Finally, spatial curling is performed with the orthogonal vector of the A-type plane normal vector as the central axis, and the common rods of adjacent units are removed to obtain the AC-type configuration element;

[0049] For the BC-type configuration, the bottom-connected cell is obtained through quadruple rotation by connecting the bottom vertices of the triangle end to end, and then the corresponding plane is obtained through array, denoted as the B-type plane lattice structure. Subsequently, with the vertical direction as the central axis, and finally, spatial curling is performed with the orthogonal vector of the B-type plane normal vector as the central axis, and the common rods of adjacent units are removed to obtain the BC-type configuration element.

[0050] The Poisson ratios of the above two types of configuration elements are regulated. According to Equations 2 - 6, two types of 6 elements with different Poisson ratios are designed.

[0051] Equation 2: ;

[0052] Equation 3: ;

[0053] Equation 4:

[0054] Equation 5:<00001];

[0055] Respectively substitute<00]00138>=-0.5, 0, 0.5 and =-0.5, 0, 0.5 into Equation 5 to solve for the remaining unknown geometric parameters; among them, the elements with negative Poisson ratio effects in the AC and BC configurations are denoted as ACN and BCN respectively; the elements with zero Poisson ratio effects in the AC and BC configurations are denoted as ACZ and BCZ respectively; the elements with positive Poisson ratio effects in the AC and BC configurations are denoted as ACP and BCP respectively. The specific parameters of the above 6 elements are shown in Table 1.

[0056]

[0057] Furthermore, it is necessary to check whether the designed geometric parameters meet the constraint conditions. The geometric constraint conditions for the included angles θ1 - θ3 are 45° < θ1 < 90°, 0° < θ2 < θ1, θ3 = 45°; the length constraint conditions for each rod are L1cosθ1 < L2cosθ2, t / L1 ≤ 0.1. If the performance requirements of the design target cannot be achieved, modify the specified and ​value, and repeat the above steps until all design requirements and geometric parameter constraints are met.

[0058] The present invention also verifies the thermal expansion coefficient and Poisson's ratio of the above six components. The specific results are as follows: Figure 4 and Figure 5 As shown. Figure 4 It can be seen that all components produce minimal thermal deformation along their axial and radial directions during the heating process from 20°C to 200°C, and the thermal expansion coefficient calculated by simulation is 1.95ppm / °C, which fully verifies its low thermal expansion coefficient performance. Figure 5 It can be seen that the components ACN and BCN shrink in the radial direction during the axial compression process, showing a negative Poisson's ratio characteristic, and the Poisson's ratio calculated by numerical simulation is -0.5; the components ACZ and BCZ only produce extremely small dimensional changes in the radial direction during the axial compression process, showing a zero Poisson's ratio characteristic, and the Poisson's ratio calculated by numerical simulation is 0.0; the components ACP and BCP expand in the radial direction during the axial compression process, showing a positive Poisson's ratio characteristic, and the Poisson's ratio calculated by numerical simulation is 0.5.

[0059] In order to better illustrate that the components provided by the present invention can meet the performance requirements of the star-sensitive satellite bracket, the present invention also carried out relevant macroscopic experimental verification. Since the preparation cycle of the components is long, the cost is high, and the experimental test is destructive, the representative component ACZ is selected for experimental verification. The component ACZ is prepared by a laser powder bed melting process. A muffle furnace is used to heat the prepared component from room temperature to 200°C, and an industrial camera is used to take real-time photos during the heating process of the component, and the thermal expansion coefficient is calculated by calculating the shape change during the heating process. An electronic universal testing machine is used to axially compress the prepared component, and an industrial camera is used to take real-time photos during the compression process of the component, and the Poisson's ratio is calculated by calculating the shape change during the compression process. The test results are as follows Figure 6 As shown in the figure, the thermal expansion coefficient of the element in the radial direction is 1.84ppm / °C when heated from room temperature to 200°C, and the thermal expansion coefficient in the axial direction is 1.89ppm / °C. The Poisson's ratio of the element in the elastic strain range of 0~3% with loading strain is 0.038, which fully verifies its low thermal expansion coefficient and Poisson's ratio control performance.

Claims

1. A low thermal expansion coefficient and adjustable Poisson's ratio component based on a triangular arrow structure Invar alloy basic unit, characterized by: The plane is obtained by quadruple rotation of the triangular arrow structure Invar alloy basic unit, removing the overlapping parts, and then connecting them through spatial curling; The basic unit is composed of a triangle and an inward concave structure at any vertex thereof, and the whole is an axisymmetric structure; the inward concave structure is composed of two inner oblique rods of length L1 extending from the vertices of the triangle and two outer oblique rods of length L3 connecting the extended end points of the inner oblique rods with the symmetry axis of the basic unit; the triangle is composed of two oblique rods of length L2 connected to the inward concave structure and a bottom rod of length L4; The quadruple rotation array is formed by taking the vertex formed by the concave structure in the basic unit as the rotation center, performing quadruple rotation, connecting the vertex to the cell, and then arranging it periodically to obtain the array; or taking the vertex of the base of the triangle in the basic unit as the rotation center, performing quadruple rotation, connecting the base to the cell, and then arranging it periodically to obtain the array; Each oblique rod and bottom rod in the basic unit is a square cross-section rod with a thickness of t; the spatial curling method is to use the orthogonal vector of the plane normal vector obtained by the four-fold rotation arrangement as the central axis for curling connection.

2. The low thermal expansion coefficient and adjustable Poisson's ratio component based on the triangular arrow structure Invar alloy basic unit according to claim 1, characterized in that: In the concave structure of the basic unit, the angle between the inner oblique rod and the symmetry axis of the basic unit is θ1, the angle between the outer oblique rod and the symmetry axis of the basic unit is θ3, and the angle between the triangular oblique rod and the symmetry axis of the basic unit is θ2.

3. The low thermal expansion coefficient and adjustable Poisson's ratio component based on the triangular arrow structure Invar alloy basic unit according to claim 2, characterized in that: The geometric constraints of the angles θ1 to θ3 are: 45°<θ1<90°, 0°<θ2<θ1, θ3=45°; the length constraints of the inner oblique rod and the triangular oblique rod are: L1cosθ1 <L2cosθ2,t / L1≤0.1。 4. The low thermal expansion coefficient and adjustable Poisson's ratio component based on the triangular arrow structure Invar alloy basic unit according to claim 1, characterized in that: The Poisson's ratio of the element is the inverse of the ratio of the radial strain to the axial strain when the element is subjected to stress loading. The specific calculation process is: Formula 1: ; In formula 1: ν represents Poisson's ratio, and denote radial strain and axial strain, respectively.

5. The low thermal expansion coefficient and adjustable Poisson's ratio component based on the triangular arrow structure Invar alloy basic unit according to claim 2, characterized in that: When the cell is a vertex-connected cell or a bottom-edge-connected cell, the Poisson's ratio calculation process of the resulting element is: Formula 2: ; Formula 3: ; Formula 4: ; Formula 5: ; Equations 2 to 4 are the calculation process parameters of Equation 5, which are dimensionless coefficients with no actual physical meaning. In Equation 5: and They represent the Poisson's ratio of the components obtained by connecting cells at the vertex and cells at the bottom.

6. A method for preparing a low thermal expansion coefficient and adjustable Poisson's ratio element based on a triangular arrow structure Invar alloy basic unit according to any one of claims 1 to 5, characterized in that: The Invar alloy powder is formed into one piece through a laser powder bed melting process.

7. Application of a low thermal expansion coefficient and adjustable Poisson's ratio element based on a triangular arrow-shaped Invar alloy basic unit according to any one of claims 1 to 5, characterized in that: Used for star-sensitive satellite bracket.

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