Omnidirectional thermo-electric camouflage device with confocal elliptical core-shell structure and its design method

Abstract

The present invention discloses an omnidirectional thermoelectric camouflage device with a confocal elliptical core-shell structure and a design method thereof. The device comprises an anisotropic confocal elliptical core-shell structure and an external background matrix. The confocal elliptical core region represents the camouflage region, and the confocal elliptical shell region represents the camouflage device. The medium of the background matrix has anisotropic material parameters. Under different heat flow and current directions, the anisotropic material parameters of the background matrix region, including thermal conductivity and electrical conductivity, are the same as the anisotropic equivalent parameters, including thermal conductivity and electrical conductivity, of the anisotropic confocal elliptical core-shell structure. This eliminates scattering caused by heat flow and current in different directions, thereby achieving a full range of camouflage functions without disturbing the external temperature and electric field distributions.

Description

Technical Field

[0001] The present invention belongs to the technical field of metamaterials and relates to an omnidirectional thermo-electric camouflage device with a confocal elliptical core-shell structure and a design method thereof. Background Art

[0002] Metamaterials are novel structural materials designed to achieve unique functionalities. They can control physical fields that are unattainable by conventional materials, such as stealth, aggregation, camouflage, and detection. Consequently, they are widely used to control electromagnetic, acoustic, thermal, and optical fields. With further research, metamaterials capable of simultaneously controlling multiple physical fields are more promising for practical application, compared to metamaterials capable of controlling only a single physical field. This allows the simultaneous control of multiple physical fields using a single device, achieving multi-field control functions. This contributes to efficient device utilization and resource conservation.

[0003] Current research on thermoelectric dual-field camouflage devices is limited to isotropic circular structures, without considering the difficulties and challenges of omnidirectional thermoelectric camouflage due to geometric anisotropy. However, depending on the actual application, the geometric shape of the camouflage device is not limited to circles. Anisotropic geometric shapes such as confocal ellipses, rhombuses, and rectangles have been applied to functional devices in other specific environments. Summary of the Invention

[0004] The present invention aims to provide an omnidirectional camouflage device and its design method, applicable to both thermal and electric fields. Regardless of the direction of heat and current flow, the device eliminates scattering caused by objects, rendering them invisible in the thermoelectric dual field. This camouflage achieves detection without disturbing the external temperature and electric field distributions, thus avoiding detection by relevant detection equipment. The thermoelectric dual-field camouflage device has potential applications in aerospace and other related technical fields.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A design method for an omnidirectional thermo-electric camouflage device based on an anisotropic confocal elliptical core-shell structure is disclosed. The omnidirectional thermo-electric camouflage device based on the anisotropic confocal elliptical core-shell structure is divided into a first region, a second region, and a third region from the inside out. The first region is used for camouflage and has an anisotropic elliptical shape. The second region is a camouflage device and has a hollow anisotropic elliptical shape. The first and second regions constitute the anisotropic confocal elliptical core-shell structure. The media within the first and second regions are made of isotropic materials. The third region serves as a background matrix for achieving the omnidirectional thermo-electric camouflage function. The media within the third region has anisotropic material parameters. Under different heat flow and current directions, the anisotropic material parameters of the third region, including thermal conductivity and electrical conductivity, are identical to the anisotropic equivalent parameters of the anisotropic confocal elliptical core-shell structure, including thermal conductivity and electrical conductivity. Consequently, regardless of changes in the direction of the external temperature gradient and potential gradient, objects in the first region will not disturb the temperature field and electric field distribution in the third region.

[0007] Preferably, the anisotropic material parameters of the third region are achieved by a composite structure made of isotropic material.

[0008] Preferably, the composite structure is composed of a matrix material and circular inclusion materials with different pore sizes.

[0009] Preferably, the preparation method of the composite structure is as follows:

[0010] First, the equivalent medium theory is used to structure the third region with anisotropic thermal conductivity and electrical conductivity into a multilayer structure with alternating layers, where the material parameters of each layer are isotropic and arbitrary. Further, the single particle structure method is used for each layer structure to transform it into a new structure consisting of a matrix and circular inclusions. The materials of the matrix and circular inclusions are isotropic materials already used in industrial production. Preferably, in the multilayer structure, the thermal conductivity of any odd-numbered layer is defined as κ1, and the electrical conductivity is defined as σ1. The thermal conductivity of any even-numbered layer is defined as κ2, and the electrical conductivity is defined as σ2. The thermal conductivity of the matrix part of the odd-numbered and even-numbered layered structures is κ, respectively. 基体1 , κ 基体2 , the conductivity is σ 基体1 , σ 基体2 The thermal conductivity of the circular inclusion part of the odd-layer and even-layer structure is κ 圆夹1 , κ 圆夹2 , the conductivity is σ 圆夹1 , σ 圆夹2 , should satisfy: κ 基体1 (κ 圆夹1 )<κ1<κ 圆夹1 (κ 基体1 ), σ 基体1 (σ圆夹1 )<σ1<σ 圆夹1 (σ 基体1 ),κ 基体2 (κ 圆夹2 )<κ2<κ 圆夹2 (κ 基体2 ),σ 基体2 (σ 圆夹2 )<σ2<σ 圆夹2 (σ 基体2 ).

[0011] In the present invention, the geometric parameters of the second region are obtained by a parameter optimization method, and the optimization control condition is: by designing and optimizing the geometric parameters of the region, the geometric parameters of the odd-even layer circular inclusions in the third region solved in the future under the temperature field are equal to the geometric parameters of the odd-even layer circular inclusions in the third region solved under the electric field, that is, the geometric parameters of the odd-even layer circular inclusions in the third region are required to be applicable to both the thermoelectric and dual fields.

[0012] The present invention also provides an omnidirectional thermo-electric camouflage device obtained according to the above design method.

[0013] The present invention is first based on the theory of neutral inclusion. After fully considering the geometric anisotropy of the confocal ellipse, the anisotropic equivalent parameters (thermal conductivity and electrical conductivity) of the confocal ellipse core-shell structure under different heat flows and current directions are theoretically solved. Then, the material parameters of the background matrix need to be consistent with the equivalent material parameters of the confocal ellipse core-shell structure derived, that is, the thermal conductivity and electrical conductivity of the background matrix need to be set to anisotropic parameters to meet the omnidirectional camouflage function in thermal and electric fields. In addition, in order to further meet actual engineering applications, the present invention, based on effective medium theory and single particle structure method, uses common materials to build a novel composite structure to realize anisotropic background matrix. This composite structure not only will embody the special anisotropic material properties of the original background matrix, but also needs to be easy to manufacture. Compared with prior art, the beneficial effects of the present invention are as follows:

[0014] The thermoelectric camouflage device of the present invention has an anisotropic geometry and is applicable to temperature and electric fields in any direction. Current research on thermoelectric camouflage primarily focuses on circular core-shell structures, which have an isotropic geometry and therefore do not need to consider the direction of the temperature and electric fields. However, for anisotropic geometries, the geometric anisotropy of the device must be fully considered. Based on this, the material parameters required for omnidirectional camouflage are determined. The present invention enables omnidirectional thermoelectric camouflage based on an anisotropic confocal elliptical core-shell structure. That is, when heat and current flow in any direction, the camouflage device with anisotropic geometry can achieve thermoelectric camouflage. Furthermore, the thermoelectric camouflage device of the present invention achieves camouflage without disturbing the temperature and electric field distribution of the background environment. This invention expands the geometry of thermoelectric camouflage devices from an isotropic circle to an anisotropic confocal ellipse, achieving omnidirectional thermoelectric camouflage, and has potential applications in aerospace and other technical fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is the geometric area distribution diagram of the omnidirectional thermoelectric camouflage device with anisotropic confocal elliptical core-shell structure.

[0016] The numbers in the figure are: 1 represents the elliptical core, 2 represents the elliptical shell, and 3 represents the background matrix. The thermal conductivity of the elliptical core is κ c The conductivity is σ c The geometric dimensions of the major and minor axes are lc1 and lc2. The thermal conductivity of the elliptical shell is κ s The conductivity is σ s The geometric dimensions of the major and minor axes are ls1 and ls2. The thermal conductivity of the background matrix is κ b The conductivity is σ b .

[0017] Figure 2 Schematic diagram of the structure of the omnidirectional thermoelectric camouflage device with anisotropic confocal elliptical core-shell structure.

[0018] Figure 3 Graph showing the distribution of temperature field simulation results for the anisotropic confocal elliptical camouflage device of Example 1 and the control group under normalized horizontal and vertical temperature gradient directions.

[0019] Figure 4 Graph showing the distribution of electric field simulation results for the anisotropic confocal elliptical camouflage device of Example 1 and the control group under normalized horizontal and vertical potential gradient directions.

[0020] Figure 5 The figure is a specific preparation flow chart of the composite structure.

[0021] Figure 6These are experimental artifact images of the omnidirectional thermoelectric camouflage device based on a confocal elliptical core-shell structure of a composite structure and an experimental artifact image of the control group.

[0022] Figure 7 Graph showing the distribution of temperature field experimental results for the anisotropic confocal elliptical camouflage device of Example 2 and the control group under normalized horizontal and vertical temperature gradient directions.

[0023] Figure 8 Graph showing the distribution of electric field experimental results for the anisotropic confocal elliptical camouflage device of Example 2 and the control group under normalized horizontal and vertical potential gradient directions. DETAILED DESCRIPTION

[0024] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] Figure 1 This is the geometric area distribution diagram of the anisotropic confocal elliptical core-shell structure omnidirectional thermoelectric camouflage device of the present invention. Both the temperature gradient and the potential gradient are normalized. Figure 1 In the equation, 1 represents the elliptical core, i.e. the first region, 2 represents the elliptical shell, i.e. the second region, and 3 represents the background matrix, i.e. the third region. The thermal conductivity of the elliptical core is κ c The conductivity is σ c The geometric dimensions of the major and minor axes are lc1 and lc2. The thermal conductivity of the elliptical shell is κ s The conductivity is σ s The geometric dimensions of the major and minor axes are ls1 and ls2. The thermal conductivity of the background matrix is κ b The conductivity is σ b .

[0026] Figure 2 This is a schematic diagram of the structure of an omnidirectional thermoelectric camouflage device with an anisotropic confocal elliptical core-shell structure. The material parameters of the background matrix in the third region are achieved by using a composite structure made of isotropic materials. The composite structure consists of a matrix material and circular inclusions with different pore sizes. See the schematic diagram of the process for constructing the composite structure for details. Figure 5 , as follows:

[0027] First, the equivalent medium theory is used to convert the anisotropic thermal conductivity and electrical conductivity (i.e. Figure 5The third region of the thermal conductivity and electrical conductivity matrix in (a) is structured into a multilayer structure with alternating layers, in which the material parameters of each layer are isotropic and arbitrary, which is not easy to implement in engineering (the thermal conductivity of the odd-numbered layers is κ1 and the electrical conductivity is σ1; the thermal conductivity of the even-numbered layers is κ2 and the electrical conductivity is σ2). We further use the single-particle structure method for each layer structure to transform it into a new structure consisting of a matrix and circular inclusions, and the materials of the matrix and circular inclusions are common isotropic ordinary materials. It should be noted that the matrix part of the odd-numbered and even-numbered layered structures (κ 基体1 , κ 基体2 , σ 基体1 , σ 基体2 ) and the circular inclusion part (κ 圆夹1 , κ 圆夹2 , σ 圆夹1 , σ 圆夹2 ) can be any material parameter, but must satisfy κ 基体1 (κ 圆夹1 )<κ1<κ 圆夹1 (κ 基体1 ),σ 基体1 (σ 圆夹1 )<σ1<σ 圆夹1 (σ 基体1 ),κ 基体2 (κ 圆夹2 )<κ2<κ 圆夹2 (κ 基体2 ),σ 基体2 (σ 圆夹2 )<σ2<σ 圆夹2 (σ 基体2 ). The circular inclusions in odd-numbered and even-numbered layers have different aperture geometries.

[0028] In the present invention, the method for selecting and setting the camouflage device material and geometric parameters is as follows:

[0029] 1. Material parameters

[0030] First, the first area is the area for achieving camouflage, and the material parameters of this area need to be selected according to the actual application requirements and can be arbitrary. The second area is the camouflage device, and the material selection of this area is also arbitrary, for example, stainless steel, copper, aluminum alloy, magnesium alloy, etc. can be selected. The selection of the base material and the circular inclusion material of the odd and even layers of the composite structure in the third area is also arbitrary. Taking into account the possible resistance at the splicing interface of different materials, the base material selection of the odd and even layers of the composite structure of the present invention is consistent with that of the second area, but it is arbitrary in principle. The circular inclusions of the odd and even layers of the composite structure in the third area and the first area are selected as air to simplify the workpiece preparation process and save costs.

[0031] 2. Geometric Parameters

[0032] The geometric parameters of the first region need to be designed based on the actual application requirements and can be arbitrary. The geometric parameters of the second region need to be obtained through parameter optimization. The optimization control condition is: by designing and optimizing the geometric parameters of this region, the geometric parameters of the odd- and even-layer circular inclusions in the third region, calculated under the temperature field, are equal to those calculated under the electric field. In other words, the geometric parameters of the odd- and even-layer circular inclusions in the third region must be applicable to both the thermoelectric and electric fields. The widths of the odd and even-layer substrates in the third region are equal. Given the known outer length, the more layers, the more accurate the result. The geometric dimensions of the odd and even-layer circular inclusions in the third region are determined by the anisotropic background matrix, the widths of the odd and even-layer substrates, and the materials of the substrates and the circular inclusions. In other words, once these parameters are known, the geometric dimensions of the circular inclusions corresponding to the odd and even layers can be calculated, which are applicable to both the thermoelectric and electric fields.

[0033] Next, the thermoelectric camouflage device will be analyzed based on anisotropic background matrix and composite structure.

[0034] Example 1

[0035] The confocal elliptical core-shell structure was placed in an anisotropic background matrix, with the first and second regions made of air and 6061 aluminum alloy. Normalized temperature gradients and electric potential gradients were applied in the horizontal and vertical directions, respectively. A control group (i.e., an air core without an elliptical shell was placed in the anisotropic background matrix) was set up to compare and verify the omnidirectional thermoelectric camouflage function of the camouflage device. The corresponding temperature field and electric field finite element simulation results are shown in Figure 3 and Figure 4 The analysis shows that: in the control group without the camouflage device, no matter whether the temperature gradient is applied horizontally or vertically, the air core causes the temperature field disturbance in the external background matrix [see Figure 3(a1), 3(a2)]. When the air core is covered by the camouflage device, the external temperature field disturbance is automatically eliminated [see Figure 3 (b1), 3(b2)]. The simulation results of the electric field show the same trend of change, that is, the presence of the camouflage device can eliminate the electric field disturbance in the background matrix and make the equipotential lines in the background matrix straight again [see Figure 4 (b1), 4(b2)]. In this way, the omnidirectional camouflage of the confocal elliptical camouflage device in the thermoelectric dual field is achieved.

[0036] This embodiment does not involve the design of the composite structure, but the material parameters of the background anisotropy still need to be consistent with the theoretically derived equivalent anisotropic thermal conductivity and electrical conductivity of the confocal elliptical core-shell structure under different heat flow current directions. This is the design concept of neutral inclusion.

[0037] Example 2

[0038] The confocal elliptical core-shell structure is placed in a composite structure, wherein the materials of the first region and the second region are air and 6061 aluminum alloy. Figure 6 The experimental workpiece of the omnidirectional thermoelectric camouflage device based on the confocal elliptical core-shell structure of the composite structure [ Figure 6 (b)] and the control group [ Figure 6 (a)] The experimental workpiece diagram. The composite structure consists of 36 layers of alternating layers. The matrix of each layer is made of 6061 aluminum alloy, and the pores are still air. The pore size geometry of different pores needs to be determined according to the anisotropic background matrix and the width of each layer of the layered structure. The horizontal and vertical temperature and potential boundary conditions and the control group settings are consistent with Example 1. The corresponding temperature field and electric field experimental results are shown in Figure 7 and Figure 8 The analysis shows that the experimental results of the temperature field and the electric field show the same trend of change. That is, in the control group without the camouflage device, no matter how the direction of the temperature and potential gradient changes, the air core will cause the temperature field [see Figure 7 (a1), 7 (a2)] and the electric field [see Figure 7 (a1), 7 (a2)] in the external composite structure. Figure 8 (a1),8(a2)], when the air core is covered by the camouflage device, the temperature field in the composite structure [see Figure 7 (b1),7(b2)] and electric field [see Figure 8 The disturbances (b1), 8(b2)] disappear, and the isothermal and equipotential lines become straight again. This experimentally demonstrates the omnidirectional camouflage of the confocal elliptical camouflage device in the thermoelectric dual field using a composite structure.

[0039] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A design method for an omnidirectional thermo-electric camouflage device based on an anisotropic confocal elliptical core-shell structure, characterized in that: The omnidirectional thermo-electric camouflage device based on the anisotropic confocal elliptical core-shell structure is divided into a first region, a second region, and a third region from the inside out. The first region is used for camouflage and is an anisotropic elliptical shape. The second region is a camouflage device and is a hollow anisotropic elliptical shape. The first and second regions constitute an anisotropic confocal elliptical core-shell structure. The media in the first and second regions are made of isotropic materials. The third region is a background matrix for achieving the omnidirectional thermo-electric camouflage function. The media in the third region has anisotropic material parameters. Under different heat flow and current directions, the anisotropic material parameters of the third region, including thermal conductivity and electrical conductivity, are the same as the anisotropic equivalent parameters, including thermal conductivity and electrical conductivity, in the anisotropic confocal elliptical core-shell structure. Therefore, no matter how the direction of the external temperature gradient and potential gradient changes, the object in the first region will not disturb the temperature field and electric field distribution in the third region. The anisotropic material parameters of the third region are achieved by a composite structure made of isotropic materials; the composite structure is composed of a matrix material and circular inclusions with different pore sizes; the composite structure is prepared as follows: First, the equivalent medium theory is used to structure the third region with anisotropic thermal conductivity and electrical conductivity into a multilayer structure with alternating layers, in which the material parameters of each layer are isotropic and arbitrary. Further, the single-particle structure method is used for each layer structure to transform it into a new structure consisting of a matrix and circular inclusions. The materials of the matrix and circular inclusions are isotropic materials already available in industrial production. In the multilayer structure, the thermal conductivity of any odd-numbered layer is defined as κ1, and the electrical conductivity is defined as σ1. The thermal conductivity of any even-numbered layer is defined as k2, and the electrical conductivity is defined as σ2. The thermal conductivities of the matrix parts of the odd-numbered and even-numbered layered structures are κ and σ, respectively. 基体1 , κ 基体2 , the conductivity is σ 基体1 , σ 基体2 The thermal conductivity of the circular inclusion part of the odd-layer and even-layer structure is κ 圆夹1 , κ 圆夹2 , the conductivity is σ 圆夹1 , σ 圆夹2 , should satisfy: κ 基体1 (κ 圆夹1 )<κ1<κ 圆夹1 (κ 基体1 ),σ 基体1 (σ 圆夹1 )<σ1<σ 圆夹1 (σ 基体1 ),κ 基体2 (κ 圆夹2 )<κ2<κ 圆夹2 (κ 基体2 ),σ 基体2 (σ 圆夹2 )<σ2<σ 圆夹2 (σ 基体2 ); The geometric parameters of the second region are obtained through parameter optimization. The optimization control condition is: by designing and optimizing the geometric parameters of this region, the geometric parameters of the odd- and even-layer circular inclusions in the third region solved in the future under the temperature field are equal to the geometric parameters of the odd- and even-layer circular inclusions in the third region solved under the electric field. That is, the geometric parameters of the odd- and even-layer circular inclusions in the third region are required to be applicable to both the thermoelectric and dual fields.

2. An omnidirectional thermo-electric camouflage device obtained according to the design method of claim 1.

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