Element with low thermal expansion coefficient and adjustable Poisson's ratio based on Invar alloy basic unit of triangular arrow structure and preparation method and application of element

Abstract

The invention discloses a low-thermal-expansion-coefficient adjustable Poisson's ratio element based on triangular arrow structure invar alloy basic units and a preparation method and application of the low-thermal-expansion-coefficient adjustable Poisson's ratio element. The element is obtained in the mode that invar alloy basic units of a triangular arrow structure pass through a quadruple rotation array to obtain a plane, overlapped parts are removed, and then spatial curl connection is conducted. Each basic unit is composed of a triangle and a concave structure located at any vertex of the triangle, and the whole basic unit is of an axial symmetry structure. According to the element, invar alloy serves as a single-component raw material, adjustment and control of the Poisson ratio of the element are achieved through triangular arrow structural design, integration of the low thermal expansion coefficient and the adjustable and controllable Poisson ratio is finally achieved, and the problem that in the prior art, elements with the low thermal expansion coefficient and the adjustable and controllable Poisson ratio adopt multi-component materials is effectively solved; the support can be integrally formed through a laser powder bed melting process, the process is simple, the integrity is high, industrial production is facilitated, and the performance requirement of the star-sensitive satellite support can be met.

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] As a special structure composed of a large number of micropores, porous structures usually have excellent lightweight performance. As a typical porous structure, cylindrical shell structure is widely used in engineering applications such as the automotive industry, aerospace industry, and biomedicine due to its excellent mechanical properties and lightweight performance. Through the systematic design of its microporous structure, personalized customization of various functions can be achieved, such as heat insulation, noise reduction, shock absorption, energy absorption, negative thermal expansion coefficient, and negative Poisson's ratio. Among them, the thermal expansion coefficient is often used to evaluate the deformation degree of solid materials / structures in a temperature-changing environment. Conventional structures / materials usually have a positive thermal expansion coefficient, that is, thermal expansion and contraction characteristics, and this property often brings a large negative impact on structural components in various aerospace fields. For example, star-sensing satellites have been in service in a temperature-changing environment for a long time, and their structural components have a large shape change under temperature-changing loading, which affects the deflection angle of the satellite and reduces the accuracy of signal transmission. The low thermal expansion coefficient cylindrical shell structure can ensure the working accuracy of the components by reducing the thermal deformation of the structural components. In addition, Poisson's ratio is a physical parameter used to describe the shape change of solid materials / structures in orthogonal directions under mechanical loading. Common materials / structures have positive Poisson's ratio performance, that is, when subjected to longitudinal tensile loads, they shrink and deform in the transverse direction. This deformation behavior usually affects the assembly accuracy of star-sensing satellite structural components. The zero Poisson's ratio cylindrical shell structure can maintain its dimensional stability in the orthogonal direction when subjected to unidirectional loads, ensuring the dimensional accuracy of structural components to the greatest extent. Therefore, cylindrical shell structures with low thermal expansion coefficients and zero Poisson's ratio have extremely high application value.

[0003] The existing cylindrical shell structure achieves the integration of low thermal expansion coefficient and zero Poisson's ratio by integrating and regulating the thermal expansion coefficient and Poisson's ratio. However, the existing cylindrical shell structure can only achieve the regulation of thermal expansion coefficient by introducing multiple component materials, which undoubtedly brings great challenges to its preparation and seriously restricts its practical engineering application. Invar alloy provides an effective solution to the above challenges. Invar alloy is an iron-nickel alloy with a nickel content of 36.wt%. Under the influence of the Invar effect, it has an extremely low thermal expansion coefficient (≤2.0ppm / °C) below the Curie temperature (230°C). Thanks to its low laser reflectivity, the mature laser powder bed melting process (PBF-LB) provides a reliable preparation process for the integrated manufacturing of Invar alloy and its complex structural components. Therefore, using Invar alloy as a component material of the cylindrical shell structure inherits the inherent low thermal expansion coefficient of Invar alloy while avoiding the extremely low manufacturability brought by multi-component materials. Furthermore, the regulation of Poisson's ratio is achieved through structural design, and finally the integration of low thermal expansion coefficient and adjustable Poisson's ratio is achieved. The cylindrical shell structure designed by the present invention realizes low thermal expansion and regulation of Poisson's ratio from negative to positive on the basis of ensuring high manufacturability, and can improve the performance of structural components under long-term service conditions of temperature field and force field coupling. For example, the structure can be used as a bracket for star-sensing satellites. Under the coupling of force and temperature, the low thermal expansion coefficient and zero Poisson's ratio performance of the structure provide extremely high dimensional stability for star-sensing satellites, thereby ensuring the accuracy of their information transmission. Summary of the invention

[0004] In view of 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, thereby finally realizing the integration of low thermal expansion coefficient and adjustable Poisson's ratio, and 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 adjustable Poisson's ratio element based on a triangular arrow structure Invar alloy basic unit. The 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. The 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] The third object of the present invention is to provide an application of a low thermal expansion coefficient adjustable Poisson's ratio element based on a triangular arrow structure Invar alloy basic unit for a star-sensing satellite bracket. The basic unit is formed by a combination of an inner concave structure and a triangle, and the adjustable Poisson's ratio theoretical formula is derived by analyzing its deformation behavior, and a quantitative correlation between various geometric parameters and Poisson's ratio values ​​is established, so that according to actual needs, the element that meets the requirements of the star-sensing satellite bracket can be accurately designed.

[0007] In order to achieve the above technical purpose, 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 is obtained by removing the overlapping parts of the plane obtained by the triangular arrow structure Invar alloy basic unit through a four-fold rotation array, and then connecting them through space curling;

[0008] The basic unit is composed of a triangle and a concave structure located at any vertex thereof, and the whole is an axisymmetric structure; the concave structure is composed 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 is composed of two oblique rods of L2 connected to the 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 angles 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 Poisson's ratio control.

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

[0011] Or, take the base vertex of the triangle in the basic unit as the rotation center, and after four rotations, get the base connecting the cells, and then arrange them periodically to get it.

[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, taking the triangular base vertex of the basic unit as the rotation center, the base-connected cell obtained after four-fold rotation can densely pave more cells in the plane per unit area. Therefore, this method has better dense paving characteristics, and the planar structure obtained after array 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 quadruple rotation as the central axis.

[0016] As a preferred solution, the geometric constraints of the angles θ1-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 constraint method 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 rods, and it will be impossible to perform quadruple rotation and subsequent periodic array.

[0019] As a preferred solution, 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:

[0020] Formula 1: ;

[0021] In formula 1: ν represents Poisson's ratio, and represent 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 obtained element is:

[0023] Formula 2: ;

[0024] Formula 3: ;

[0025] Formula 4: ;

[0026] Formula 5: ;

[0027] Formulas 2 to 4 are the calculation process parameters of Formula 5, which are dimensionless coefficients without actual physical meaning. In Formula 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 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 by 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-sensitive 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 an adjustable Poisson's ratio, effectively solving the problem of using multi-component materials in the adjustable Poisson's ratio element in the prior art.

[0032] 2) The preparation method provided by the present invention utilizes the low laser reflectivity of Invar alloy and adopts the laser powder bed melting process to carry out integrated additive manufacturing of the cylindrical shell porous structure. The 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) In the technical solution provided by the present invention, a basic unit is formed by a combination of a concave structure and a triangle. 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 is established. This allows accurate design of components that meet the requirements of a star-sensitive satellite bracket according to 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 solution in the embodiments, the drawings required for use in the content of the invention and the embodiments are briefly described below.

[0035] Figure 1 A 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 realizing low thermal expansion coefficient and Poisson's ratio control design provided in an embodiment of the present invention;

[0041] Reference numerals:

[0042] 1-Triangular arrow basic unit; 2-A type cell; 3-B type cell; 4-A type plane lattice structure; 5-B type 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. Obviously, the described embodiments 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 the 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 obtaining a plane by four-fold rotation array of triangular arrow-shaped Invar alloy basic units, removing overlapping parts, and then connecting them by space curling;

[0047] The basic unit is composed of a triangle and an inward concave structure at any vertex thereof, and is an axisymmetric structure as a whole; 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 methods 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, vertex-connected cells are obtained through quadruple rotation. Subsequently, the corresponding plane is obtained through array and 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 cells are obtained through quadruple rotation by connecting the bottom vertices of the triangle end to end. Subsequently, the corresponding plane is obtained through array and denoted as the B-type plane lattice structure. Then, 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: ;

[0055] Respectively, =-0.5, 0, 0.5 and =-0.5, 0, 0.5 are substituted into Equation 5 to solve 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 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 required by the design goal 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 have minimal thermal deformation in the 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 very 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 conducts 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. At the same time, 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, 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 regulation performance.

Claims

1. A low thermal expansion coefficient adjustable Poisson's ratio element based on a triangular arrow structure Invar alloy basic unit, characterized in that: The plane obtained by quadruple rotation array of triangular arrow structure Invar alloy basic unit, removing the overlapping parts, and then connecting them by space curling; The basic unit is composed of a triangle and a concave structure located at any vertex thereof, and the whole is an axisymmetric structure; the concave structure is composed 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 is composed of two oblique rods of L2 connected to the concave structure and a bottom rod with a length of L4.

2. According to claim 1, a low thermal expansion coefficient adjustable Poisson's ratio element based on a triangular arrow structure Invar alloy basic unit, characterized in that: The method of the four-fold rotation array is: taking the vertex formed by the concave structure in the basic unit as the rotation center, after four-fold rotation, the vertex is connected to the cell, and then it is arranged periodically to obtain; or, taking the vertex of the base of the triangle in the basic unit as the rotation center, after four-fold rotation, the base is connected to the cell, and then it is arranged periodically to obtain.

3. The low thermal expansion coefficient adjustable Poisson's ratio element 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.

4. A low thermal expansion coefficient adjustable Poisson's ratio element based on a triangular arrow structure Invar alloy basic unit according to any one of claims 1 to 3, characterized in that: 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.

5. The low thermal expansion coefficient adjustable Poisson's ratio element based on the triangular arrow structure Invar alloy basic unit according to claim 4, characterized in that: The geometric constraints of the angles θ1-θ3 are: , , ; The length constraints of the inner oblique rod and the triangular oblique rod are: .

6. The low thermal expansion coefficient adjustable Poisson's ratio element 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 represent radial strain and axial strain respectively.

7. The low thermal expansion coefficient adjustable Poisson's ratio element 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: ; Formulas 2 to 4 are the calculation process parameters of Formula 5, which are dimensionless coefficients without actual physical meaning. In Formula 5: and They represent the Poisson's ratio of the components obtained by connecting cells at the vertex and cells at the bottom.

8. A method for preparing a low thermal expansion coefficient adjustable Poisson's ratio element based on a triangular arrow structure Invar alloy basic unit according to any one of claims 1 to 8, characterized in that: The Invar alloy powder is integrally formed through a laser powder bed melting process to obtain the product.

9. Application of a low thermal expansion coefficient adjustable Poisson's ratio element based on a triangular arrow structure Invar alloy basic unit according to any one of claims 1 to 8, characterized in that: Used for star-sensitive satellite bracket.

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