A zero-expansion vibration isolation integrated metamaterial structure based on additive manufacturing

Abstract

The application discloses a zero-expansion and vibration reduction integrated metamaterial structure based on additive manufacturing, and relates to the field of lightweight multifunctional structures.The zero-expansion and vibration reduction integrated metamaterial structure comprises a plurality of zero-expansion and vibration reduction units.The zero-expansion and vibration reduction unit comprises an inner frame and an outer frame.The inner frame comprises four support parts connected together at the ends.The outer frame is connected to the other ends of the support parts and is sleeved outside the support parts.The thermal expansion coefficient of the inner frame is less than 50% of the thermal expansion coefficient of the outer frame.The zero-expansion and vibration reduction integrated metamaterial structure has the functions of zero expansion and vibration reduction.

Description

TECHNICAL FIELD

[0001] The application relates to a zero-expansion vibration isolation integrated metamaterial structure for simultaneously realizing passive thermal deformation control and passive vibration control and belongs to the technical field of lightweight multifunctional structures. BACKGROUND

[0002] A new generation of spacecraft has the characteristics of high resolution, strong maneuverability and high attitude stability, and urgently needs material-structure-function integration of the spacecraft structure. How to improve the thermal dimensional stability and vibration isolation characteristics of the structure in the space environment while meeting the lightweight requirement has important research value. In recent years, with the development of additive manufacturing technology, three-dimensional metamaterial structures have broken the design limitations of traditional single-scale and single-function structures due to their high specific bearing and high specific stiffness, and their functional design parameters are multiple and can be widely adjusted, which provides a new technical approach for lightweight multifunctional structure development.

[0003] The existing zero-expansion metamaterials (or "near-zero expansion" metamaterials) at home and abroad are mainly based on the thermal deformation mismatch principle. After the structure is heated, non-uniform thermal deformation occurs in each part, so that the thermal displacement of certain fixed points is extremely small, and the equivalent thermal expansion coefficient of the whole structure is smaller than the thermal expansion coefficient of the parent material. These zero-expansion metamaterials usually do not have vibration control function and will lose the thermal deformation control ability under the influence of micro-vibration.

[0004] The vibration isolation metamaterials developed at home and abroad at present are usually based on the principle of local resonance or quasi-zero stiffness. When the structure is subjected to external excitation, local vibration of the internal microstructure occurs to dissipate mechanical energy, so that the inherent vibration of the instrument does not propagate outward through the base, and the base vibration does not transmit to the precision instrument through the base. The equivalent stiffness of these vibration isolation metamaterials is usually zero, and under the action of thermal load, large shape distortion may occur.

[0005] In view of the above, it is necessary to develop a metamaterial structure with zero expansion and vibration isolation functions. SUMMARY

[0006] The technical problem solved by the application is to overcome the shortcomings of the prior art and provide a metamaterial structure with zero equivalent thermal expansion coefficient and wide zero-frequency vibration isolation function, which overcomes the defects of functional separation of the existing metamaterials and can have zero expansion and vibration isolation functions.

[0007] The technical solution of the application is:

[0008] The application discloses a zero-expansion vibration isolation integrated metamaterial structure based on additive manufacturing, which comprises a plurality of zero-expansion vibration isolation unit cells.

[0009] The one end of the support part is a center end, and the other end is a terminal end; the external frame is located in the middle of the part between the terminal ends of two adjacent support parts, and the cell connection point is protruded to the side away from the center end.

[0010] The zero-expansion vibration isolation unit cells are arranged in a normal orthogonal periodic manner; a cell connection rod is connected between adjacent zero-expansion vibration isolation unit cells, and the cell connection rod is connected to the cell connection point; after the zero-expansion vibration isolation unit cells are arranged periodically, the unit cells are used to fill in the internal part of various bearing frames, and do not affect the connection relationship of the bearing frame itself; and the center line of the external frame is not consistent with the load movement direction.

[0011] The shape of the part between the terminal ends of the two adjacent support parts is a sinusoidal curve; the chord height and the frame width of the sinusoidal curve can be changed to adjust the local resonance frequency range of the unit cell.

[0012] The sinusoidal curve is y = l2sin (pi / l1) x, wherein l2 is the chord height of the sinusoidal curve, and l1 is the straight line length of the external frame between the positions connected with the terminal ends of the two adjacent support parts.

[0013] The part between the terminal ends of the two adjacent support parts is 1 / 2 period of the sinusoidal curve, and the middle part of the part between the terminal ends of the two adjacent support parts is the maximum chord height position of the sinusoidal curve.

[0014] The ratio of l2 to l1 is 1: (0-2000), and the minimum value of l2 is 0.

[0015] The thickness w2 of the internal frame and the thickness w1 of the external frame satisfy the relationship w1 >= 3w2.

[0016] The internal frame is a normal cross shape; the width w1 of the internal frame and the ratio of w1 to w2 can be changed to adjust the equivalent thermal expansion coefficient of the zero-expansion vibration isolation unit cell, so that the expansion coefficient of the zero-expansion vibration isolation unit cell is 0.1 ppm / K to the thermal expansion coefficient of the internal frame material.

[0017] The internal frame is made of titanium alloy material, and the external frame is made of aluminum alloy material.

[0018] According to the above, the application at least has the following beneficial technical effects:

[0019] (1) The super material cell is used to simultaneously realize thermal deformation control and vibration control, and avoids design problems such as functional coupling and functional interference of heterogeneous cells.(2) The super material cell can be periodically extended, so that the configuration design of the zero-expansion-vibration-reduction cell is not affected by the overall structure topology.(3) The structure is simple, and can be combined with heterogeneous material additive manufacturing technology to realize integrated manufacturing of large multifunctional structures. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 A super material cell structure provided by the application is shown in the figure.

[0021] Figure 2 A super material cell periodic extension method provided by the application is shown in the figure.

[0022] Marked as follows: 1, internal frame; 2, external frame; 3, cell connection point; 4, zero-expansion-vibration-reduction cell; 5, connecting rod.

[0023] Figure 2 The curve 6 in the figure is an external frame curve schematic. DETAILED DESCRIPTION

[0024] The application will be described in further detail below with reference to the accompanying drawings and specific embodiments:

[0025] The embodiment of the application discloses a zero-expansion-vibration-reduction integrated super material structure based on additive manufacturing, as shown in Figure 1 and Figure 2 , which comprises a plurality of zero-expansion-vibration-reduction cells 4.

[0026] The zero-expansion-vibration-reduction cell 4 comprises an internal frame 1 and an external frame 2, the internal frame 1 comprises four support parts connected together at the ends, and the external frame 2 is connected to the other end of the support part and is sleeved outside the support part; the thermal expansion coefficient of the internal frame 1 is less than 50% of the thermal expansion coefficient of the external frame 2. In the embodiment, the internal frame 1 is made of titanium alloy material, and the external frame 2 is made of aluminum alloy material.

[0027] The end of the support part connected to each other is the center end, and the other end is the terminal end, the external frame 2 is located in the middle part between the two adjacent support part terminal ends, and the cell connection point 3 protrudes to the side away from the center end. In the embodiment, the internal frame 1 is a right-angled cross shape, and the equivalent thermal expansion coefficient of the cell can be adjusted by changing the width of the internal frame 1.

[0028] The plurality of zero-expansion-vibration-reduction cells 4 are arranged in a right-angled and periodic manner, as shown in Figure 2As shown, adjacent zero-expansion vibration damping and isolation cells 4 are connected by cell connecting rods 5, which are connected to cell connection points 3. After the zero-expansion vibration damping and isolation cells 4 are arranged periodically, they can fill the interior of various load-bearing frames without affecting the connection relationship of the load-bearing frames themselves. Moreover, when the zero-expansion vibration damping and isolation cells 4 are used, their positions satisfy the following: the centerline of the outer frame 2 is not consistent with the direction of load movement.

[0029] The shape of the portion of the outer frame 2 between the ends of two adjacent supports is a sine curve. Changing the chord height and frame width of the sine curve adjusts the range of local resonant frequencies within the cell. The sine curve is y = l2sin(π / l1)x, where l2 is the chord height and l1 is the straight-line length of the outer frame between its connection points with the ends of the two adjacent supports. The ratio of l2 to l1 is 1:(0-2000), and the minimum value of l2 is 0. The portion of the outer frame 2 between the ends of the two adjacent supports is half the period of the sine curve. The middle of this portion is where the chord height of the sine curve is at its maximum, which is also the location of cell connection point 3. The relationship between the thickness w2 of the inner frame 1 and the thickness w1 of the outer frame 2 is that w1 ≥ 3w2.

[0030] Through the above technical solution, an internal frame 1 and an external frame 2 with specific differences in thermal expansion coefficients are selected to design a structure of a metamaterial cell with zero expansion coefficient. The local geometric features of the metamaterial cell, such as curvature, width, and length, are adjusted to enable the cell to have vibration isolation function. A connecting rod 5 is added to the cell at the zero expansion fixed point to realize the periodic extension of the cell. According to the external load conditions, the arrangement of the periodic metamaterial structure is adjusted so that the structure still has zero expansion and vibration reduction and isolation functions under external load.

[0031] The design method for the aforementioned integrated metamaterial structure is as follows:

[0032] Step 1: Based on the target thermal expansion coefficient of cell connection point 3, design the overall configuration of the inner frame 1 and the outer frame 2. The two frames together form the metamaterial cell. The positions of the inner frame 1 and the outer frame 2 in the cell can be interchanged according to the specific design scheme, or other two materials with large differences in thermal expansion coefficients can be selected as the base material.

[0033] Step 2: Adjust the thickness w2 of the aluminum alloy frame and the chord height l2 of the sine curve to change the local stiffness; the smaller w2 is, the smaller the stiffness of the aluminum alloy frame, and the smaller l2 is, the smaller the stiffness of the aluminum alloy frame at the chord height position.

[0034] Step 3: Use finite element analysis to verify the equivalent thermal expansion coefficient of metamaterial cell connection point 3.

[0035] Step 4: Using finite element analysis, apply a displacement boundary condition that varies with time according to a sinusoidal waveform on the left side of the cell, and check the vibration response on the right side of the cell.

[0036] Step 5: Add connecting rod 5 at cell connection point 3 and periodically array it in the plane.

[0037] The implementation principle of this application is as follows:

[0038] After periodically arranging the zero-expansion vibration-damping cells 4, they are filled inside various load-bearing frames without affecting the connection relationship of the load-bearing frames themselves. The equivalent thermal expansion coefficient of the zero-expansion vibration-damping cells 4 themselves is close to zero, so that the equivalent thermal expansion coefficient of the filled load-bearing frames is also close to zero. When the zero-expansion vibration-damping cells 4 undergo local resonance under vibration excitation at specific frequencies, when the filled load-bearing frames work at these excitation frequencies, the vibration energy is dissipated by the local resonance of the cells and will not continue to propagate through the load-bearing frames, thus achieving the effect of vibration isolation.

[0039] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims of the present invention.

Claims

1. A zero-expansion vibration reduction and isolation integrated metamaterial structure based on additive manufacturing, characterized in that: Includes multiple zero-expansion damping cells (4); The zero-expansion vibration reduction cell (4) includes an inner frame (1) and an outer frame (2). The inner frame (1) includes four support parts connected together at their ends. The outer frame (2) is connected to the other end of the support parts and is fitted outside the support parts. The coefficient of thermal expansion of the inner frame (1) is less than 50% of the coefficient of thermal expansion of the outer frame (2). The support parts are connected at one end as the center end and the other end as the end end. The outer frame (2) is located at the middle of the part between the ends of two adjacent support parts as the cell connection point (3). The cell connection point (3) protrudes to the side away from the center end. The zero-expansion vibration reduction and isolation cells (4) are arranged in an orthogonal periodic manner; adjacent zero-expansion vibration reduction and isolation cells (4) are connected by cell connecting rods (5), and the cell connecting rods (5) are connected to the cell connection points (3); after the zero-expansion vibration reduction and isolation cells (4) are arranged periodically, they are used to fill the interior of various load-bearing frames, and the center line of the outer frame (2) is not consistent with the direction of load movement. The inner frame (1) is an orthogonal cross shape. By changing the thickness w1 of the inner frame (1) and its ratio with the thickness w2 of the outer frame (2), the equivalent thermal expansion coefficient of the zero expansion damping cell (4) can be adjusted, so as to achieve a minimum expansion coefficient of 0.1ppm / K to the thermal expansion coefficient of the inner frame (1) material. The shape of the portion of the outer frame (2) between the ends of two adjacent support parts is a sine curve.

2. The zero-expansion vibration reduction and isolation integrated metamaterial structure based on additive manufacturing according to claim 1, characterized in that: The sine curve is y=l2sin(π / l1)x, where l2 is the chord height of the sine curve and l1 is the straight length of the outer frame (2) between the connection positions of the ends of the two adjacent support parts.

3. The zero-expansion vibration reduction and isolation integrated metamaterial structure based on additive manufacturing according to claim 1, characterized in that: The portion of the outer frame (2) between the ends of two adjacent support parts is half the period of a sine curve, and the middle portion of the portion of the outer frame (2) between the ends of two adjacent support parts is the position of the maximum chord height of the sine curve.

4. The zero-expansion vibration reduction and isolation integrated metamaterial structure based on additive manufacturing according to claim 2, characterized in that: The l2:l1=1:(0-2000).

5. The zero-expansion vibration reduction and isolation integrated metamaterial structure based on additive manufacturing according to claim 1, characterized in that: The relationship between the thickness w1 of the inner frame (1) and the thickness w2 of the outer frame (2) is that w1 ≧ 3w2.

6. The zero-expansion vibration reduction and isolation integrated metamaterial structure based on additive manufacturing according to claim 1, characterized in that: The inner frame (1) is made of titanium alloy, and the outer frame (2) is made of aluminum alloy.

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