A dual-material microstructure with negative thermal expansion properties
By designing a dual-material microstructure with negative thermal expansion properties, using materials and interlaced structures with different thermal expansion coefficients, the problems of instability and high cost of existing materials during temperature changes are solved, and efficient thermal expansion performance adjustment and structure are achieved. Compactness.
Patent Information
- Application Number
- CN202210485734.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-05-06
- Publication Date
- 2025-01-03
- Estimated Expiration
- 2042-05-06
AI Technical Summary
The thermal expansion coefficient of existing materials is greater than zero when the temperature changes, resulting in unstable structure, and the negative thermal expansion materials are costly and difficult to prepare. They are prone to phase change during the composite process, affecting the consistency of the expansion coefficient.
Using two materials with different thermal expansion coefficients but both positive, through microstructure design, combined with annular structure and L-shaped structure, and using laser selection melting technology to form a double-material microstructure with negative thermal expansion properties, through interlaced structure design and The geometric parameter adjustment achieves the adjustability of the macroscopic thermal expansion coefficient.
Linear deformation within a certain temperature range is achieved, the compactness of the structure and thermal expansion performance are improved, the cost of materials is reduced, and the impact of phase change on the expansion coefficient is avoided, and the metamaterial with negative thermal expansion properties is realized.
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Figure CN114914699B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a dual-material microstructure with negative thermal expansion properties, belonging to the technical field of negative thermal expansion mechanical metamaterials. Background Art
[0002] With the development of industries such as aerospace and precision instruments, the thermal expansion coefficient of most natural materials is usually greater than zero when the temperature changes, that is, thermal expansion and contraction will occur. This thermal deformation caused by temperature changes will cause changes in the fine structure, making the system unstable or even destroyed. The current common solution is to compound positive thermal expansion materials with negative thermal expansion materials to achieve a near-zero expansion effect.
[0003] Existing materials that achieve negative thermal expansion or micro thermal expansion by changing composition and microstructure, such as ZrW2O8, Sc2(WO4)3 and other materials, have isotropic thermal expansion coefficients, but these materials are expensive and difficult to prepare. The mechanism of negative thermal expansion is not yet clear. At the same time, these negative thermal expansion materials are prone to phase change under external conditions during the preparation of composite materials, and the expansion coefficients before and after the phase change are quite different.
[0004] Metamaterials are different from traditional materials that regulate their properties by changing their composition and organization. Metamaterials focus on constructing suitable artificial microstructure units and optimizing the geometric structure of artificial microstructure units to obtain new materials. The structural materials obtained in this way show equivalent mechanical properties, and materials can be designed according to requirements to obtain specific mechanical properties. Therefore, it is very necessary to prepare metamaterials with negative thermal expansion properties on a macro scale through microstructure design using two materials with different but positive thermal expansion coefficients. Summary of the invention
[0005] The purpose of the present invention is to use two materials with different but positive thermal expansion coefficients to prepare a metamaterial with negative thermal expansion properties on a macro scale through microstructure design.
[0006] The technical solution of the present invention is as follows:
[0007] A dual-material microstructure with negative thermal expansion properties comprises an annular structure 1, a connecting plate 2 and an L-shaped structure 3, wherein the annular structure 1 has a notch, two annular structures 1 are connected by a connecting plate 2, and two ends of the connecting plate 2 are respectively inserted into the notches of the two annular structures 1; the L-shaped structure 3 is composed of a vertically connected A rod and a B rod, the A rods of the two L-shaped structures 3 are respectively inserted into the notches of the two annular structures 1, and there is a gap between the A rod and the connecting plate 2; the annular structure 1 is composed of an inner circular ring 1-1 with a notch and an outer circular ring 1-2 with a notch; the inner circular ring 1-1 and the L-shaped structure 3 use a material with a thermal expansion coefficient of a1, the outer circular ring 1-2 and the connecting plate 2 use a material with a thermal expansion coefficient of a2, and 0<a1<a2.
[0008] It is further defined that the ring walls of the inner ring 1-1 and the outer ring 1-2 have the same thickness.
[0009] It is further defined that the lower surface of one end of the connecting plate 2 is connected to the lower portion of the notch of the annular structure 1 located on the same side of the end, and the upper surface of the other end of the connecting plate 2 is connected to the upper portion of the notch of the annular structure 1 located on the same side of the end.
[0010] It is further defined that the inner diameter r1 of the annular structure 1 is 2 mm, and the outer diameter r2 is 3 mm; the inner point opening angle α of the notch of the annular structure 1 is 50°, and the outer point opening angle β is 32.73°.
[0011] It is further defined that the length L of the connecting plate 2 is 4 mm and the width is 0.6 mm.
[0012] It is further defined that the length c of the A rod is 2.69 mm, the width f is 0.5-0.8 mm, the length b of the B rod is 3-3.6 mm, and the width a is 0.5-0.7 mm.
[0013] Further defined, a1 is 1.9e-5 and a2 is 1.5e-6.
[0014] It is further defined that the connection plate 2 is composed of an upper sheet layer 2-1 and a lower sheet layer 2-2 stacked together, the upper sheet layer 2-1 is made of a material with a thermal expansion coefficient of a1, and the lower sheet layer 2-2 is made of a material with a thermal expansion coefficient of a2.
[0015] It is further defined that the two L-shaped structures 3 have the same shape but are composed of different materials, one of which uses a material with a thermal expansion coefficient of a1, and the A rod in the other L-shaped structure 3 uses a material with a thermal expansion coefficient of a1, and the B rod is composed of a second layer 3-2 using a material with a thermal expansion coefficient of a1 and a first layer 3-1 using a material with a thermal expansion coefficient of a2, and the first layer 3-1 is connected to the A rod.
[0016] The dual-material microstructure with negative thermal expansion properties is integrally formed by laser selective melting technology.
[0017] The present invention has the following beneficial effects:
[0018] (1) The present invention uses a bimetallic ring set and connects two bimetallic rings in series with a metal sheet. The driving force for deformation relies on the warping deformation of the bimetallic ring and the displacement of the metal sheet caused by the warping of the bimetallic ring. Through the staggered structure design, the structural symmetry is changed from symmetry about the Y axis to symmetry about a straight line in the XY plane, thereby improving the compactness of the structure in the Y direction. While not significantly increasing the structural size in the Y direction, it can accommodate the deformation of the two bimetallic rings. Within a certain temperature range, it can achieve a linear relationship between deformation and temperature change, thereby obtaining a bimaterial microstructure with negative thermal expansion properties.
[0019] (2) The bi-material microstructure with negative thermal expansion properties provided by the present invention is composed of two materials with different thermal expansion coefficients. The two materials constitute a bimetallic ring in the microstructure. When the temperature rises, the bimetallic ring will warp, causing the metal sheet to move, thereby causing the overall structure to shrink. The microstructure can achieve the adjustability of the thermal expansion coefficient of the macro material and the temperature-driven linear elastic deformation by adjusting the geometric parameters and thermal expansion coefficient of the bimetallic ring and the metal sheet.
[0020] (3) In addition, the bi-material microstructure with negative thermal expansion properties provided by the present invention can adjust the thermal expansion coefficient of the material by selecting different metal materials, or adjusting the geometric parameters of the bimetallic ring and the bimetallic strip in the microstructure, so that the macroscopic thermal expansion coefficient of the metamaterial can be adjusted, thereby further realizing negative thermal expansion performance. At the same time, since the displacement of the bimetallic ring and the bimetallic strip is linearly related to the temperature change, the deformation of the microstructure is also linearly related to the temperature change. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 This is a schematic diagram of the three-dimensional structure of the handcuffs configuration microstructure in which the intermediate connecting structure is a single metal sheet in Example 1;
[0022] Figure 2 It is a front view of the handcuffs configuration microstructure of Example 1;
[0023] Figure 3 This is a diagram showing the finite element simulation results of the Y-direction deformation of the handcuff configuration microstructure in Example 1;
[0024] Figure 4 This is a diagram showing the finite element simulation results of the X-direction deformation of the handcuff configuration microstructure in Example 1;
[0025] Figure 5 This is a diagram showing the finite element simulation results of the Z-direction deformation of the handcuff configuration microstructure in Example 1;
[0026] Figure 6 This is a schematic diagram of the three-dimensional structure of the handcuffs microstructure in Example 2, in which the intermediate connecting structure is a bimetallic sheet;
[0027] Figure 7 It is a front view of the handcuffs configuration microstructure of Example 2;
[0028] Figure 8 This is a diagram showing the finite element simulation results of the Y-direction deformation of the handcuff configuration microstructure in Example 2;
[0029] Fig. 9 This is a diagram showing the finite element simulation results of the X-direction deformation of the handcuff configuration microstructure in Example 2;
[0030] Fig.10 It is a schematic diagram of deformation amount of the deformed structure;
[0031] In the figure, 1-annular structure, 1-1-inner ring, 1-2-outer ring, 2-connecting plate, 2-1-upper layer, 2-2-lower layer, 3-L-shaped structure, 3-1-first layer, 3-2-second layer DETAILED DESCRIPTION
[0032] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained through commercial channels by those skilled in the art.
[0033] Embodiment 1:
[0034] The connecting plate 2 of the handcuffs microstructure of this embodiment is a single metal sheet:
[0035] like Figure 1 and Figure 2As shown, the handcuffs microstructure with a single metal sheet as the intermediate connection structure includes a ring structure 1, a connection plate 2 and an L-shaped structure 3. The ring structure 1 has a gap. Two ring structures 1 are connected by a connection plate 2. The two ends of the connection plate 2 are respectively inserted into the gaps of the two ring structures 1; the L-shaped structure 3 is composed of a vertically connected A rod and a B rod. The A rods of the two L-shaped structures 3 are respectively inserted into the gaps of the two ring structures 1, and there is a gap between the A rod and the connection plate 2. The ring structure 1 is composed of an inner ring 1-1 with a gap and an outer ring 1-2 with a gap. The inner ring 1-1 and the L-shaped structure 3 use a material with a thermal expansion coefficient of a1, and the outer ring 1-2 and the connection plate 2 use a material with a thermal expansion coefficient of a2, and the above 0<a1<a2, and the ring wall thickness of the inner ring 1-1 and the outer ring 1-2 is the same. In this way, the two metal rings are set and the two bimetallic rings are connected in series with a connecting plate 2. The driving force for the deformation relies on the warping deformation of the bimetallic rings and the displacement of the connecting plate 2 caused by the warping of the bimetallic rings. Through the staggered structure design, the symmetry of the entire microstructure is changed from symmetry about the Y axis to symmetry about a straight line in the XY plane, thereby improving the compactness of the structure in the Y direction. While not significantly increasing the structural size in the Y direction, it can accommodate the deformation of the two bimetallic rings. Within a certain temperature range, it can be achieved that the deformation changes linearly with the temperature, thereby obtaining a bimaterial microstructure with negative thermal expansion properties.
[0036] The lower surface of one end of the connecting plate 2 is connected to the lower part of the notch of the annular structure 1 located on the same side of the end, and the upper surface of the other end of the connecting plate 2 is connected to the upper part of the notch of the annular structure 1 located on the same side of the end.
[0037] like Figure 2 As shown, the inner diameter of the ring structure 1 is r1, which is 2 mm, and the outer diameter r2 is 3 mm; the inner point opening angle α of the notch of the ring structure 1 is 50°, and the outer point opening angle β is 32.73°. The length L of the connecting plate 2 is 4 mm, and the width is 0.6 mm. The length c of the A rod is 2.69 mm, and the width f is 0.5 mm. The length b of the B rod is 3.46 mm, and the width a is 0.62 mm.
[0038] The negative thermal expansion characteristics of the handcuffs microstructure of this embodiment were numerically simulated using the finite element simulation software abaqus. The elastic modulus of the material was set to E = 147 GPa, the Poisson's ratio was μ = 0.3, and the thermal expansion coefficients were α1 = 1.9e-5 and α2 = 1.5e-6. Since there is bending deformation during the deformation of the microstructure, the unit type of the finite element simulation is a quadratic wedge unit to ensure the accuracy of the simulation. The results are as follows:
[0039] (1) The results of the finite element simulation of the handcuffs microstructure deformation in the Y direction are as follows Figure 3As shown in the figure, it can be seen that the deformation of the handcuff configuration in the Y direction is very significant. The bimetallic ring as a deformation driving structure provides two types of deformation forms for the structure of this configuration. One is the "curling" behavior of the two bimetallic rings, which causes the structure to shrink significantly in the Y direction. The other is the "warping" behavior of the bimetallic ring endpoints, which causes the middle connection structure to warp, thereby also providing a relatively considerable Y-direction contraction. Driven by the above two deformations, the deformation of the lower endpoint of the handcuff configuration structure in the Y direction reached 0.374mm, and the deformation rate reached 6.45%.
[0040] (2) The results of the finite element simulation of the handcuffs microstructure deformation in the X direction are shown in Figure 4 As shown, for the handcuffs microstructure, the deformation in the X direction should be controllable. The maximum deformation in the X direction of the handcuffs structure occurs at the bottom and top of the left and right rings of the structure, and the displacement in the X direction of the lower end point of the structure is 0.0316 mm, which is 0.316% of the X-direction structure size.
[0041] (3) The results of the finite element simulation of the Z-direction deformation of the handcuffs microstructure are as follows Figure 5 As shown, the deformation of the entire structure in the Z direction is mainly concentrated at the two ends of the Z direction, which is caused by the high thermal expansion material at the edge. The maximum deformation is 0.0036 mm, which is very small and can be ignored.
[0042] Embodiment 2:
[0043] The connecting plate 2 of the handcuffs microstructure of this embodiment is a bimetallic sheet:
[0044] like Figure 6 and Figure 7 As shown, the difference between this embodiment and embodiment 1 is that the connecting plate 2 is composed of an upper layer 2-1 and a lower layer 2-2 stacked together, the upper layer 2-1 uses a material with a thermal expansion coefficient of a1, the lower layer 2-2 uses a material with a thermal expansion coefficient of a2, and the upper layer 2-1 and the lower layer 2-2 have the same size; the two L-shaped structures 3 have the same shape and different constituent materials, one of which uses a material with a thermal expansion coefficient of a1, and the A rod in the other L-shaped structure 3 uses a material with a thermal expansion coefficient of a1, and the B rod is composed of a second layer 3-2 using a material with a thermal expansion coefficient of a1 and a first layer 3-1 using a material with a thermal expansion coefficient of a2, the first layer 3-1 is connected to the A rod, and the first layer 3-1 and the second layer 3-2 have the same thickness.
[0045] The negative thermal expansion characteristics of the handcuffs microstructure of this embodiment were numerically simulated using the finite element simulation software abaqus. The elastic modulus of the material was set to E = 147 GPa, the Poisson's ratio was μ = 0.3, and the thermal expansion coefficients were α1 = 1.9e-5 and α2 = 1.5e-6. The results are as follows:
[0046] (1) The results of the finite element simulation of the handcuffs microstructure deformation in the Y direction are as follows Figure 8 As shown, the connection plate 2 is changed to a bimetallic sheet, which has little effect on the deformation of the handcuffs microstructure in the Y direction, reaching 0.37 mm, and the deformation rate is 6.38%.
[0047] (2) The results of the finite element simulation of the handcuffs microstructure deformation in the X direction are shown in Fig. 9 As shown, the connection plate 2 is changed to a bimetallic sheet, which has a greater impact on the handcuffs configuration microstructure in the X direction. The displacement in the X direction after the improvement is 0.0051 mm, which is 16.14% of the displacement before the improvement. It can be seen that the bimetallic sheet used in the lower end connection structure can significantly reduce the displacement in the X direction.
[0048] For the displacement of the lower end point of the handcuffs microstructure, due to the symmetry of the left and right structures, the total deformation of the structure should be twice the deformation of the unilateral structure; the displacement of the unilateral structure is divided into two parts: one part is the displacement caused by the bending and curling of the bimetallic ring, and the other part is the displacement caused by the warping of the connecting plate, such as Fig.10 As shown,
[0049] The deformation of the single-side structure is the sum of the deformation of the ring structure and the displacement of the connecting plate in the Y direction caused by the angular torsion, as shown in the following equations (1), (2) and (3):
[0050] Y=2×y 单 (1)
[0051] y 单 =y 内 +y 连接 (2)
[0052]
[0053] Where Y is the displacement of the lower end point of the microstructure, in millimeters (mm); L is the length of the connecting plate; y 单 is the displacement caused by the unilateral structure; y 内 is the displacement of the inner end point of the ring; y 外 is the displacement of the outer end point of the ring; y 连接 is the displacement of the connecting plate in the single-side structure; d is the section thickness at the opening of the ring, and the calculation formula is as follows;
[0054]
[0055] Where r1 is the inner diameter of the ring; r2 is the outer diameter of the ring; α1 is the inner point opening angle α, and α2 is the outer point opening angle β;
[0056] The displacement of the inner and outer points of the open ring is obtained by fitting, as shown in the following formula (4):
[0057]
[0058] In the formula, a and b are fitting parameters; x is the comprehensive geometric parameter, which is calculated as follows:
[0059]
[0060] In the formula, x1 is the outer diameter of the ring; x2 is the thickness of the ring;
[0061] The formula derived above can be used to calculate the cross-sectional thickness of the ring opening as d = 1.0658 mm, y 内 =0.099241333mm, y 外 =0.152586716mm, the calculated value of the displacement of the lower endpoint of the structural unit is Ycalculated=0.3989mm, while the actual displacement value obtained by simulation with Abaqus software is Ysimulated=0.3816, and the relative error between the two is 4.54%.
[0062] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and 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 dual-material microstructure with negative thermal expansion properties, characterized in that: The invention comprises an annular structure (1), a connecting plate (2) and an L-shaped structure (3), wherein the annular structure (1) has a notch, two annular structures (1) are connected by a connecting plate (2), and two ends of the connecting plate (2) are respectively inserted into the notches of the two annular structures (1); the L-shaped structure (3) is composed of an A rod and a B rod connected vertically, the A rods of the two L-shaped structures (3) are respectively inserted into the notches of the two annular structures (1), and there is a gap between the A rod and the connecting plate (2); the annular structure (1) is composed of an inner circular ring (1-1) with a notch and an outer circular ring (1-2) with a notch; the inner circular ring (1-1) and the L-shaped structure (3) are made of a material with a thermal expansion coefficient of a1, and the outer circular ring (1-2) and the connecting plate (2) are made of a material with a thermal expansion coefficient of a2, 0<a1<a2.
2. A dual-material microstructure with negative thermal expansion properties according to claim 1, characterized in that: The inner ring (1-1) and the outer ring (1-2) have the same ring wall thickness.
3. A dual-material microstructure with negative thermal expansion properties according to claim 1, characterized in that: The lower surface of one end of the connecting plate (2) is connected to the lower part of the notch of the annular structure (1) located on the same side as the end, and the upper surface of the other end of the connecting plate (2) is connected to the upper part of the notch of the annular structure (1) located on the same side as the end.
4. A dual-material microstructure with negative thermal expansion properties according to claim 1, characterized in that: The inner diameter r1 of the annular structure (1) is 2 mm, and the outer diameter r2 is 3 mm; the inner point opening angle α of the notch of the annular structure (1) is 50°, and the outer point opening angle β is 32.73°.
5. A dual-material microstructure with negative thermal expansion properties according to claim 1, characterized in that: The length L of the connecting plate (2) is 4 mm, and the width is 0.6 mm.
6. A dual-material microstructure with negative thermal expansion properties according to claim 1, characterized in that: The length c of the A rod is 2.69 mm, and the width f is 0.5-0.8 mm. The length b of the B rod is 3-3.6 mm, and the width a is 0.5-0.7 mm.
7. A dual-material microstructure with negative thermal expansion properties according to claim 1, characterized in that: The a1 is 1.9e -5 , a2 is 1.5e -6 .
8. A dual-material microstructure with negative thermal expansion properties according to claim 1, characterized in that: The connecting plate (2) may also be composed of an upper layer (2-1) and a lower layer (2-2) stacked together, wherein the upper layer (2-1) is made of a material with a thermal expansion coefficient of a1, and the lower layer (2-2) is made of a material with a thermal expansion coefficient of a2.
9. A dual-material microstructure with negative thermal expansion properties according to claim 1, characterized in that: The two L-shaped structures (3) may also have the same shape but different constituent materials, wherein one of the L-shaped structures uses a material having a thermal expansion coefficient of a1, and in the other L-shaped structure (3), the A rod uses a material having a thermal expansion coefficient of a1, and the B rod is composed of a second sheet layer (3-2) using a material having a thermal expansion coefficient of a1 and a first sheet layer (3-1) using a material having a thermal expansion coefficient of a2, and the first sheet layer (3-1) is connected to the A rod.
10. A dual-material microstructure with negative thermal expansion properties according to claim 1, characterized in that: The dual-material microstructure with negative thermal expansion properties is integrally formed using laser selective melting technology.