Preparation method of a jujube-shaped double-layer deformable honeycomb structure

Abstract

The present invention discloses a method for preparing a jujube-shaped double-layer deformable honeycomb structure, which relates to the field of flexible structure design of variant aircraft. The double-layer deformable honeycomb structure composed of jujube-shaped single cells can be designed by adjusting parameters such as the length of the connecting plate, the length of the bending plate, the width of the flexible unit, the thickness of the flexible unit, and the initial distance between adjacent connecting plates according to the size of the skin, the deformation capacity, and the out-of-plane load-bearing capacity. The present invention solves the contradiction that the flexible skin requires both large in-plane deformation and sufficient out-of-plane load-bearing capacity, and has strong designability and easy process implementation. The present invention is different from the overall processing of other skin structures. The structure is formed by transverse welding of several cut longitudinal flexible plates, which greatly reduces the difficulty of production and has high engineering practicality.

Description

Technical Field

[0001] The invention relates to the field of flexible structure design of variant aircraft, and in particular to a design and manufacturing method of a jujube-shaped double-layer deformable honeycomb structure. Background Art

[0002] Morphing aircraft have to go through complex flight environments throughout the flight mission, and the flight state has to change at any time. Morphing aircraft change the structural shape of the aircraft in real time to maintain the best aerodynamic performance in a wide range of speeds. The wing is the main component that generates lift and has a great impact on the performance of the aircraft. The wing deformation requires the flexible skin structure to provide sufficiently large in-plane deformation and sufficient out-of-plane load-bearing capacity. Therefore, flexible skin with deformation and load-bearing capacity that meet the requirements of wing deformation has become an important challenge in the design of morphing aircraft. Summary of the invention

[0003] At present, most flexible skins adopt corrugated structures or other ingenious structural forms. Among them, the deformable honeycomb structure has the characteristics of light weight, large in-plane deformation and strong out-of-plane bearing capacity, and is one of the more ideal structural forms. The present invention is aimed at a double-layer deformable honeycomb structure of a jujube-shaped unit cell, and proposes a specific design and manufacturing method. The double-layer deformable honeycomb structure composed of the jujube-shaped unit cell can achieve large in-plane deformation, strong out-of-plane bearing capacity, and the unit is easy to replicate, and can be combined into a variety of flexible deformable structures.

[0004] The present invention is achieved in that:

[0005] A method for preparing a jujube-shaped double-layer deformable honeycomb structure, characterized in that the jujube-shaped double-layer deformable honeycomb structure is formed by replicating and expanding a jujube-shaped unit cell, each of which comprises four flexible units; and the flexible units are provided with curved plates at different levels;

[0006] The bending plate on one layer is bent to the right, and forms a jujube-shaped unit cell with the bending plate on the same layer on another flexible unit on the right. The bending plate on another layer on the flexible unit is bent to the other left, and forms a jujube-shaped unit cell with the bending plate on the same layer on another flexible unit on the left. The unit cell structure is replicated and combined to form a double-layer or triple-layer deformable honeycomb structure. There are connecting plates on the flexible unit to connect the roots of the bending plates on different layers together to achieve the natural connection of the deformable honeycomb structures on different layers. The length of the deformable honeycomb is L, the width is W, and the thickness is h. The deformation mainly occurs in the width direction. The structural parameters are the flexible unit length a+2b and the width h, where a is the length of the connecting plate, b is the length of the bending plates at the upper and lower ends, the width h of the flexible unit is equal to the thickness of the deformable honeycomb, both are h; the thickness of the flexible unit t, the initial distance c between the connecting plates of adjacent flexible units, the elastic modulus E of the flexible unit, the slit width d, the number of transverse flexible units m, the number of longitudinal flexible units n; the pore size of the honeycomb grid depends on the distance c between the flexible units and the length a+2b of the flexible units; the number of flexible units m in the width (transverse) direction is preliminarily determined by c, W=mc; the number of flexible units n in the length (longitudinal) direction is determined according to the longitudinal size a+2b of the honeycomb pores, L=n(a+2b);

[0007] The deformation u of each flexible unit bending plate is determined by the deformation requirement U of the deformable honeycomb structure, U=2mu; the lateral deformation u of the bending plate is related to the length b of the bending plate, u≤0.15b, and b and a are determined;

[0008] m, t and h are determined by the out-of-plane stiffness; the out-of-plane normal loads on the L and W planes are arranged into linear loads acting on a beam structure with a length L, a width B0 (after adjusting the beam width B0 to meet the out-of-plane load-bearing requirements, the deformable honeycomb W=B0 is taken), and a height H0 (after adjusting the beam height H0 to meet the out-of-plane load-bearing requirements, the deformable honeycomb thickness h=H0 is taken, and the flexible unit width is the same as the deformable honeycomb thickness). The boundary conditions at both ends are fixed supports, which are the same as the boundary conditions of the finite element analysis. The midpoint displacement w1 is calculated, and the converted midpoint displacement is w2 according to the conversion coefficient; w2 is corrected using the results of the finite element analysis.

[0009] Furthermore, the specific steps to modify w2 using the results of finite element analysis are as follows:

[0010] 1) The jujube-shaped double-layer deformable honeycomb structure is modeled using shell elements, with the horizontal axis as the x-axis, the vertical axis as the y-axis, and the z-axis determined according to the right-hand rule;

[0011] 2) Input structural parameters and material parameters;

[0012] 3) Set the left and right boundary supports according to the actual usage;

[0013] 4) Treat the out-of-plane aerodynamic load as a linear load acting in the z direction of the corresponding node;

[0014] 5) Select the unit type as S8R and divide the grid;

[0015] 6) Submit the work to calculate the midpoint displacement w3, and the correction coefficient is η=w2 / w3; if the deformation at the midpoint exceeds the specified requirements, adjust m, h or t; h does not exceed the specified thickness of the flexible skin; according to the corrected B, m, t and h are determined according to c+u to meet the honeycomb transverse pore requirements, B=mt; (Since the flexible unit bending plate in the deformable honeycomb is in a bent state, the beam structure is only an approximate result. The w3 here is the finite element simulation result to correct w2 and determine the correction coefficient, which is convenient for the subsequent use of theoretical results to infer the actual situation.)

[0016] According to the material mechanics, the end of the cantilever beam is subjected to lateral deformation u and the end angle is 0, and the load required at the end of the bending plate is solved. and the stress at the root of the bending plate Check the strength of the bending plate, the total driving force F = 2nf.

[0017] Furthermore, the bending plate on the flexible unit is divided into an upper bending plate and a lower bending plate, with a connecting plate (5) in the middle. According to the different bending directions of the upper bending plate and the lower bending plate at the same level, the flexible unit can be divided into type A flexible unit and type B flexible unit, which can form unit cell structures of different shapes; the pore length of the type A jujube-shaped unit cell is 2(a+2b), and the pore length of the type B jujube-shaped unit cell is a+2b; the conversion coefficient of the type A jujube-shaped unit cell is 1 / 4, and the conversion coefficient of the type B jujube-shaped unit cell is 5 / 32.

[0018] Furthermore, the flexible unit contains a bending plate, a connecting plate, a slit and a crack-stop hole; the flexible unit has an initial bending shape, and the lateral distance between the end of the bending plate and the connecting plate is c / 2; the A-type flexible unit forms a slit with a length of b (the slit length must be consistent with the length of the bending plate) and a width of d at h / 2 in the width direction, and cuts the bending plate to form two layers of bending plates, namely, an upper layer bending plate (1) at the upper end, a lower layer bending plate (2) at the upper end, an upper layer bending plate (3) at the lower end, and a lower layer bending plate (4) at the lower end; when the ends are subjected to an in-plane load, the upper layer bending plate at the upper end bends to the right, the upper layer bending plate at the lower end bends to the left, the upper layer bending plate at the upper end bends to the left, and the lower layer bending plate at the lower end bends to the right; the B-type flexible unit has a slit at the width Two slits with a length of b and a width of d are formed at 1 / 4h and 3 / 4h in the degree direction, and the bending plate is cut to form a bending plate of three levels; namely, an upper bending plate (1) at the upper end, a lower bending plate (2) at the upper end, an upper bending plate (3) at the lower end, a lower bending plate (4) at the lower end, a middle bending plate (8) at the upper end, and a middle bending plate (9) at the lower end. When the ends are subjected to in-plane loads, the upper bending plate and the lower upper bending plate bend to the right, the upper middle bending plate and the lower middle bending plate bend to the left, and the upper lower bending plate and the lower lower bending plate bend to the right. A crack stop hole (7) is provided at the junction of the bending plate and the connecting plate, that is, at the bottom of the bending plate, and the diameter D of the crack stop hole is more than 3 times the width d of the slit (6).

[0019] Furthermore, the longitudinal flexible unit of the jujube-shaped double-layer deformable honeycomb structure is composed of m flexible plates with a length of n(a+2b), a width of h and a thickness of t, and is formed by marking, punching stop holes and cutting at the cutting positions of the bending plates of each flexible unit in the arrangement manner of b, a, 2b, a, 2b, a, ..., 2b, a, b, and the diameter of the stop holes is more than 3 times the width of the cutting. When making type A longitudinal flexible plates, the cutting positions are at h / 2 of the wide side, and when making type B longitudinal flexible plates, the cutting positions are at h / 4 and 3h / 4 of the wide side.

[0020] Further, the initial bending shape stamping includes:

[0021] The upper bending plate and the lower bending plate of the same layer of the A-type longitudinal flexible plate have opposite bending directions. The bending direction of the upper bending plate in the odd-numbered columns is first right and then left, and the bending direction of the lower bending plate is first left and then right. The bending direction of the upper bending plate in the even-numbered columns is first left and then right, and the bending direction of the lower bending plate is first right and then left.

[0022] The upper and lower bent plates of the same layer of the B-type longitudinal flexible plate have the same bending direction. The upper and lower bent plates of the odd-numbered columns bend to the right, and the middle bent plates bend to the left. The upper and lower bent plates of the even-numbered columns bend to the left, and the middle bent plates bend to the right.

[0023] The stamping process must also meet the requirements of the initial distance c between the connecting plates of adjacent flexible plates and the tangency of the ends of the bent plates of adjacent flexible units; then the bent plates to be connected on the same level of adjacent longitudinal flexible plates are welded; when a lateral pulling force is applied to the support seat, a jujube-shaped double-layer deformable honeycomb structure is automatically formed.

[0024] The beneficial effects of the present invention compared with the prior art are:

[0025] 1. The present invention adopts a jujube-shaped double-layer deformable honeycomb structure, which can achieve large and uniform lateral deformation of the flexible skin and has sufficient out-of-plane load-bearing capacity;

[0026] 2. According to the different skin sizes, deformation capabilities, and out-of-plane load-bearing capabilities, the structure can be designed by adjusting parameters such as the length a of the connecting plate, the length b of the bending plate, the width h of the flexible unit, the thickness t of the flexible unit, and the initial distance c of adjacent connecting plates;

[0027] 3. The present invention solves the contradiction that the flexible skin requires large deformation in the plane and sufficient load-bearing capacity out of the plane, and has strong designability and easy process implementation. The present invention is different from the overall processing of other skin structures. The structure is formed by transverse welding of several cut longitudinal flexible plates, which greatly reduces the difficulty of production and has high engineering practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the structure of type A flexible unit;

[0029] Figure 2 It is a schematic diagram of the structure of type B flexible unit;

[0030] Figure 3 Schematic diagram of a type A jujube-shaped double-layer deformable honeycomb structure in an embodiment of the present invention;

[0031] Figure 4 Schematic diagram of a B-type jujube-shaped double-layer deformable honeycomb structure in an embodiment of the present invention;

[0032] Figure 5 This is a schematic diagram of the A-type jujube-shaped unit cell structure in an embodiment of the present invention;

[0033] Figure 6 Schematic diagram of the B-type jujube-shaped unit cell structure in an embodiment of the present invention;

[0034] Figure 7 Schematic diagram of layered welding of type A longitudinal flexible plates in an embodiment of the present invention;

[0035] Figure 8 Schematic diagram of layered welding of a B-type longitudinal flexible plate in an embodiment of the present invention;

[0036] Among them, 1-upper end upper layer curved plate, 2-upper end lower layer curved plate, 3-lower end upper layer curved plate, 4-lower end lower layer curved plate, 5-connecting plate, 6-cutting slit, 7-stop crack hole, 8-upper end middle layer curved plate, 9-lower end middle layer curved plate. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail by enumerating examples below. It should be noted that the specific implementation described here is only used to explain the present invention and is not used to limit the present invention.

[0038] The jujube-shaped double-layer deformable honeycomb structure of the present invention is formed by replicating and expanding a jujube-shaped unit cell, and each jujube-shaped unit cell contains 4 flexible units. There are curved plates at different levels on the flexible unit; the curved plates at different levels are bent in different directions, and the ends of the curved plates at the same level on adjacent flexible units are welded together to form a jujube-shaped unit cell. The curved plates at a certain level are bent in one (right) direction to form a jujube-shaped unit cell with the curved plates at the same level on another flexible unit (on the right), and the curved plates at another level on the flexible unit are bent in another (left) direction to form a jujube-shaped unit cell with the curved plates at the same level on another flexible unit (on the left). There are connecting plates on the flexible unit to naturally connect the roots of the curved plates at different levels together, thereby realizing the natural connection of deformable honeycomb structures at different levels. The bending plates on the flexible unit are divided into upper bending plates and lower bending plates. According to the different bending directions of the upper bending plates and the lower bending plates at the same level, they can be divided into type A flexible units and type B flexible units, which can form unit cell structures of different shapes. Four type A flexible units form type A jujube-shaped units, and four type B flexible units form type B jujube-shaped units. The unit cell structure can be easily copied and combined to form a double-layer or triple-layer deformable honeycomb structure. The jujube-shaped double-layer deformable honeycomb structure serves as the skeleton of the flexible skin, which is covered with an elastic film, etc. to form a flexible skin.

[0039] The flexible unit contains a bending plate, a connecting plate 5, a slit 6 and a crack stop hole 7. The length of the flexible unit is a+2b and the width is h, where a is the length of the connecting plate and b is the length of the upper and lower bending plates. The flexible unit has an initial bending shape, and the lateral distance between the end of the bending plate and the connecting plate is c / 2. Figure 1 , Figure 2 As shown. A-type flexible unit forms a slit with a length of b and a width of d at h / 2 in the width direction, cutting the curved plate to form a curved plate with two levels. Figure 1The middle bending plate 1 is the upper bending plate at the upper end, the bending plate 3 is the upper bending plate at the lower end, the bending plate 2 is the lower bending plate at the upper end, and the bending plate 4 is the lower bending plate at the lower end. When the ends are subjected to in-plane loads, the upper bending plate at the upper end bends to the right, the upper bending plate at the lower end bends to the left, the upper bending plate at the lower end bends to the left, and the lower bending plate at the lower end bends to the right. The solid line in the figure represents the upper bending plate, and the dotted line represents the lower bending plate. The B-type flexible unit forms two slits with a length of b and a width of d at 1 / 4h and 3 / 4h in the width direction, cutting the bending plate to form three levels of bending plates. Figure 2 The middle bending plate 1 is the upper bending plate at the upper end, the bending plate 4 is the upper bending plate at the lower end, the bending plate 2 is the middle bending plate at the upper end, the bending plate 5 is the middle bending plate at the lower end, the bending plate 3 is the lower bending plate at the upper end, and the bending plate 6 is the lower bending plate at the lower end. When the ends are subjected to in-plane loads, the upper bending plate at the upper end and the upper bending plate at the lower end bend to the right, the upper middle bending plate at the upper end and the lower middle bending plate at the lower end bend to the left, and the upper lower bending plate at the upper end and the lower lower bending plate at the lower end bend to the right. In the figure, the solid line represents the upper bending plate, the dotted line represents the middle bending plate, and the left view of the lower bending plate coincides with the upper bending plate. A crack stop hole is set at the junction of the bending plate and the connecting plate (i.e., the bottom of the bending plate), and the diameter D of the crack stop hole is more than 3 times the slit width d.

[0040] Schematic diagram of double-layer deformable honeycomb structure Figure 3 , Figure 4 As shown, a local structure is taken out from the double-layer deformable honeycomb structure for analysis. The length of this part of the double-layer deformable honeycomb is 4(a+2b), the width is 4c, and it includes 4 rows and 4 columns of flexible units. The bending method of the bending plate of each row of flexible units is the same, and the bending method of the bending plate of each row of flexible units is also the same. Therefore, only the bending method of the bending plate of 2 rows and 2 columns of flexible units needs to be given. According to the different bending directions of the upper and lower bending plates on the same layer of the flexible unit, a type A jujube-shaped single cell structure and a type B jujube-shaped single cell structure can be formed. The structure is as follows: Figure 5 , Figure 6 shown.

[0041] When the A-type jujube-shaped unit cell is subjected to in-plane load, the bending direction of the upper bending plate and the lower bending plate on the same layer of the flexible unit is opposite. The bending mode of the horizontally arranged flexible units is symmetrical. The upper upper bending plate 1 of the upper left flexible unit bends to the right, the lower upper bending plate 3 bends to the left, the upper lower bending plate 2 bends to the left, and the lower lower bending plate 4 bends to the right; the upper upper bending plate 1 of the upper right flexible unit bends to the left, the lower upper bending plate 3 bends to the right, the upper lower bending plate 2 bends to the right, and the lower lower bending plate 4 bends to the left. The bending modes of the longitudinally arranged flexible units are symmetrical. The upper bending plate 1 at the upper end of the lower left flexible unit bends to the left, the upper bending plate 3 at the lower end bends to the right, the lower bending plate 2 at the upper end bends to the right, and the lower bending plate 4 at the lower end bends to the left; the upper bending plate 1 at the upper end of the lower right flexible unit bends to the right, the upper bending plate 3 at the lower end bends to the left, the lower bending plate 2 at the upper end bends to the left, and the lower bending plate 4 at the lower end bends to the right. The ends of the bending plates on the same layer of the adjacent flexible units are welded together tangentially to form a double-layer jujube-shaped unit cell. The upper bending plate forms a complete jujube-shaped unit cell (indicated by a thick solid line), and the lower bending plate and the left (right) jujube-shaped unit cell (indicated by a dotted line) form a complete jujube-shaped unit cell (indicated by a thin solid line). The upper and lower jujube-shaped units are connected together by a connecting plate.

[0042] When the B-type jujube-shaped unit cell is subjected to in-plane load, the upper bending plate and the lower bending plate on the same layer of the flexible unit have the same bending direction, and the bending mode of the laterally arranged flexible units is symmetrical. The upper upper layer bending plate 1 and the lower upper layer bending plate 4 of the upper left flexible unit bend to the right, the upper middle layer bending plate 2 and the lower middle layer bending plate 5 bend to the left, and the upper lower layer bending plate 3 and the lower lower layer bending plate 6 bend to the right; the upper upper layer bending plate 1 and the lower upper layer bending plate 4 of the upper right flexible unit bend to the left, the upper middle layer bending plate 2 and the lower middle layer bending plate 5 bend to the right, and the upper lower layer bending plate 3 and the lower lower layer bending plate 6 bend to the left. The bending modes of the longitudinally arranged flexible units are symmetrical up and down. The upper bending plate 1 at the upper end and the upper bending plate 4 at the lower end of the left lower flexible unit are bent to the right, the upper middle bending plate 2 and the lower middle bending plate 5 are bent to the left, and the upper lower bending plate 3 and the lower lower bending plate 6 are bent to the right; the upper upper bending plate 1 at the upper end and the lower upper bending plate 4 at the lower right lower flexible unit are bent to the left, the upper middle bending plate 2 and the lower middle bending plate 5 are bent to the right, and the upper lower bending plate 3 and the lower lower bending plate 6 are bent to the left. The ends of the bending plates on the same layer of the adjacent flexible units are tangently welded together to form a three-layer jujube-shaped unit cell. The upper bending plate and the lower bending plate form a complete jujube-shaped unit cell (indicated by a thick solid line), and the middle bending plate and the left (right) jujube-shaped unit cell (indicated by a dotted line) form a complete jujube-shaped unit cell (indicated by a thin solid line). The upper, middle and lower jujube-shaped units are connected together by a connecting plate. There is a height difference between the upper honeycomb structure and the middle honeycomb structure (arranged in a way that one row is high and the other row is low).

[0043] Every two rows and two columns of flexible units form a jujube-shaped unit cell. The jujube-shaped unit cells form a jujube shape at a certain level, and form a jujube shape with adjacent jujube-shaped units at another level. The ends of the curved plates on the same level of adjacent jujube-shaped units are welded together tangentially, so that the jujube-shaped unit cells are replicated and expanded, and finally support seats are added on the left and right sides to form a deformable honeycomb structure. The connecting plates of the longitudinally arranged flexible units are on the same straight line, and a whole plate containing n (a+2b) can be used to replace the n flexible units in the same longitudinal column. According to the arrangement of b, a, 2b, a, 2b, a, ..., 2b, a, b, the plates are marked, punched, and cut in the longitudinal direction to make the initial curved shape, and the curved plates that need to be connected on the same level of adjacent longitudinal flexible plates are welded to form A and B type jujube-shaped double-layer deformable honeycomb structures.

[0044] The parameter design method of the jujube-shaped double-layer deformable honeycomb structure of the present invention is as follows.

[0045] The length of the deformable honeycomb is L, the width is W, and the thickness is h. The deformation mainly occurs in the width direction. The structural parameters are: the length of the flexible unit is a+2b, the width is h (the width of the flexible unit is equal to the thickness of the deformable honeycomb, both are h), the length of the connecting plate is a, the length of the bending plate is b, the thickness of the flexible unit is t, the initial distance between the connecting plates of adjacent flexible units is c, the elastic modulus of the flexible unit is E, the slit width is d, the number of transverse flexible units is m, and the number of longitudinal flexible units is n.

[0046] The pore size of the honeycomb grid mainly depends on the distance c between the flexible units and the length a+2b of the flexible units. The pore length of the A-type unit cell is 2(a+2b), and the pore length of the B-type unit cell is a+2b. The number of flexible units in the width direction m is preliminarily determined by c, W=mc. The number of flexible units in the length direction n is determined according to the longitudinal dimension a+2b of the honeycomb pores, L=n(a+2b).

[0047] The deformation u of each flexible unit bending plate is determined by the deformation requirement U of the deformable honeycomb structure, U = 2mu. The lateral deformation u of the bending plate is related to the length b of the bending plate. Considering the small deformation assumption, u≤0.15b, b and a are determined, and the longitudinal deformation under small deformation can be ignored.

[0048] m, t and h are further determined by the out-of-plane stiffness. The out-of-plane normal loads on the L and W planes are organized into linear loads acting on a beam structure of length L, width B0, and height H0. The boundary conditions at both ends are fixed (the same as the boundary conditions of the finite element analysis), and the midpoint displacement w1 is calculated. The conversion coefficient of the A-type unit cell is 1 / 4, and the conversion coefficient of the B-type unit cell is 5 / 32. The midpoint displacement after conversion is w2. The results of the finite element analysis are used to correct w2. The steps are as follows: 1) The shell unit is used to model the jujube-shaped double-layer deformable honeycomb structure, with the horizontal direction as the x-axis and the vertical direction as the y-axis, and the z-axis is determined according to the right-hand rule. 2) Input structural parameters and material parameters. 3) Set the left and right boundary fixation according to actual use. 4) The out-of-plane aerodynamic load is processed into a linear load acting in the z direction of the corresponding node. 5) Select the unit class item as S8R and divide the mesh. 6) Submit the work to calculate the midpoint displacement w3, and the correction coefficient is η=w2 / w3. If the deformation at the midpoint exceeds the specified requirements, adjust m, h or t (h does not exceed the specified thickness of the flexible skin). Based on the corrected B, determine m, t and h according to c+u to meet the honeycomb transverse pore requirements, B=mt.

[0049] According to the material mechanics, the end of the cantilever beam is subjected to lateral deformation u and the end angle is 0, and the load required at the end of the bending plate is solved. and the stress at the root of the bending plate Check the strength of the bending plate, the total driving force F = 2nf.

[0050] The simplicity of making the present invention is as follows.

[0051] The longitudinal flexible unit of the jujube-shaped double-layer deformable honeycomb structure can be composed of m flexible plates with a length of n(a+2b), a width of h, and a thickness of t. The flexible plates of each flexible unit are arranged in the order of b, a, 2b, a, 2b, a, ..., 2b, a, b, and the crack-stopping holes are cut at the slit positions. The diameter of the crack-stopping holes is more than 3 times the slit width. When making A-type longitudinal flexible plates, the slit positions are at h / 2 of the wide side, and when making B-type longitudinal flexible plates, the slit positions are at h / 4 and 3h / 4 of the wide side. The cutting method can be selected from water jet, laser or wire cutting.

[0052] The initial bending shape needs to be Figure 7 , Figure 8The upper and lower bent plates of the same layer of the A-type longitudinal flexible plate have opposite bending directions. The bending directions of the upper bent plates of the odd-numbered columns are first right and then left, and the bending directions of the lower bent plates are first left and then right; the bending directions of the upper bent plates of the even-numbered columns are first left and then right, and the bending directions of the lower bent plates are first right and then left. The upper and lower bent plates of the B-type longitudinal flexible plate have the same bending direction as the lower bent plates of the same layer. The upper and lower bent plates of the odd-numbered columns are bent to the right, and the middle bent plates are bent to the left. The upper and lower bent plates of the even-numbered columns are bent to the left, and the middle bent plates are bent to the right. Stamping must also meet the requirements of the initial distance c between the connecting plates of adjacent flexible plates and the tangency of the ends of the bent plates of adjacent flexible units. Afterwards, the bent plates that need to be connected at the same layer of adjacent longitudinal flexible plates are welded. In this way, when a lateral tension is applied to the support seat, a jujube-shaped double-layer deformable honeycomb structure is automatically formed.

[0053] Specific data examples are listed below to illustrate the present invention.

[0054] The initial parameters are: assuming that the deformable honeycomb length L = 240 mm, the deformable honeycomb width W = 240 mm, the deformable honeycomb thickness h = 10 mm, the material elastic modulus E = 71.7 GPa, the required total lateral deformation U = 60 mm, the normal deformation of the midpoint of the deformable honeycomb under out-of-plane load w ≤ 2 mm, the honeycomb grid pore length does not exceed 50 mm, and the width does not exceed 20 mm.

[0055] According to the pore requirements of the honeycomb grid, it is assumed that the distance between the flexible units c = 8mm and the length of the flexible unit a + 2b = 24mm, thereby determining the number of longitudinal flexible units n = 10 and the number of transverse flexible units m = 30. Each bending plate deforms u = 1mm. According to u ≤ 0.15b, the length of the bending plate b = 9mm and the length of the connecting plate a = 6mm. Assume that the width of the flexible unit h = 10mm and t = 0.2mm. The out-of-plane normal loads on the L and W planes are arranged into linear loads acting on a beam structure with a length of L = 240mm, a width of B = 6mm, and a height of h = 10mm. The boundary conditions at both ends are fixed supports, and the midpoint displacement w1 = 0.34mm is calculated. The conversion coefficient of the A-type unit cell is 1 / 4, and the conversion coefficient of the B-type unit cell is 5 / 32. Taking the A-type unit cell as an example, the midpoint displacement after conversion is w2 = 1.36mm. The results of finite element analysis are used to correct w2. The steps are as follows: 1) Use shell elements to model the jujube-shaped double-layer deformable honeycomb structure, with the horizontal direction as the x-axis and the vertical direction as the y-axis. Determine the z-axis according to the right-hand rule. 2) Input the structural and material parameters. 3) Set the left and right boundary clamps according to the actual usage. 4) Treat the out-of-plane aerodynamic load as a linear load acting in the z direction of the corresponding node. 5) Select the unit class item as S8R and divide the mesh. (6) Submit the work to calculate the midpoint displacement w3 = 1.943mm, the correction coefficient is η = 0.7, and the deformation at the midpoint does not exceed the specified requirements. c + u = 9mm meets the requirements of the honeycomb transverse pores, and t = 0.2mm and h = 10mm are determined.

[0056] According to the conditions of material mechanics that the end of the cantilever beam is subjected to lateral deformation u and the end rotation angle is 0, the required load f at the end of the bending plate is obtained to be 3.93N, and the stress σmax at the root of the bending plate is 531MPa. The strength of the bending plate is checked to meet the requirements, and the total driving force is F=78.6N.

[0057] Taking the production of A-type jujube-shaped double-layer deformable honeycomb structure as an example, the specific production steps are as follows:

[0058] 1) To make the A-type jujube-shaped double-layer deformable honeycomb structure, 30 flexible plates with a length of 240 mm, a width of 10 mm, and a thickness of 0.2 mm should be selected. The flexible plates should be free of cracks and have good flatness;

[0059] 2) Take the lower left corner of the flexible board as the origin, start from (5, 0), draw a 9mm line upward, then draw a 18mm line every 6mm, and the last line is 9mm. Make a crack stop hole with a diameter of 1.0mm at the end point of the line;

[0060] 3) Select a molybdenum wire with a diameter of 0.2 mm, pass the molybdenum wire through the crack stop hole, and perform wire cutting along the scribe line to make an A-type longitudinal flexible plate;

[0061] 4) According to the requirements that the initial distance c between the connecting plates of adjacent flexible units is 8 mm and the ends of the bent plates of adjacent flexible units are tangent, the longitudinal flexible plates are stamped and formed;

[0062] 5) Arrange 30 longitudinal flexible plates along the thickness direction of the connecting plate, and weld the curved plates to be connected on the same layer of adjacent longitudinal flexible plates;

[0063] 6) Weld the support seats to the left side of the first longitudinal flexible plate that bends to the left and the right side of the 30th longitudinal flexible plate that bends to the right.

[0064] Thus, the manufacture of the jujube-shaped double-layer deformable honeycomb structure is completed. When an in-plane lateral pulling force is applied to the support seat, the present invention can achieve a large uniform in-plane lateral deformation and have sufficient out-of-plane stiffness.

[0065] The above description is only a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements without departing from the principle of the present invention, and these improvements should also be regarded as within the protection scope of the present invention.

Claims

1. A method for preparing a jujube-shaped double-layer deformable honeycomb structure, characterized in that: The jujube-shaped double-layer deformable honeycomb structure is formed by replicating and expanding the jujube-shaped unit cell, and each jujube-shaped unit cell contains 4 flexible units; There are curved plates at different levels on the flexible unit; The bending plate on one layer is bent to the right, and forms a jujube-shaped unit cell with the bending plate on the same layer on another flexible unit on the right that is bent to the left. The bending plate on another layer on the flexible unit is bent to the other left, and forms a jujube-shaped unit cell with the bending plate on the same layer on the left that is bent to the right. The unit cell structure is replicated and combined to form a double-layer or triple-layer deformable honeycomb structure. There are connecting plates on the flexible unit to connect the roots of the bending plates on different layers together, so as to realize the natural connection of the deformable honeycomb structures on different layers. The length L, width W and thickness h of the deformable honeycomb are mainly in the width direction. The structural parameters are flexible unit length a+ 2b, width h, where a is the length of the connecting plate, b is the length of the upper and lower bending plates, the width h of the flexible unit is equal to the thickness of the deformable honeycomb, both are h; the thickness of the flexible unit t, the initial distance c between the connecting plates of adjacent flexible units, the elastic modulus E of the flexible unit, the slit width d, the number of transverse flexible units m, the number of longitudinal flexible units n; the pore size of the honeycomb grid depends on the distance c between the flexible units and the length a+2b of the flexible units; the number of flexible units / lines m in the width direction is preliminarily determined by c, W=mc; the number of flexible units n in the length direction is determined according to the longitudinal size a+2b of the honeycomb pores, L=n(a+2b); The deformation u of each flexible unit bending plate is determined by the deformation requirement U of the deformable honeycomb structure, U = 2mu; The lateral deformation u of the bending plate is related to the length b of the bending plate, u≤0.15b, determine b and a; m, t and h are determined by the out-of-plane stiffness; the out-of-plane normal loads on the L and W planes are arranged into linear loads acting on the beam structure with a length of L, a width of B0 and a height of H0. After the out-of-plane load requirements are met by adjusting the beam width B0, the deformable honeycomb W=B0 is taken, and the boundary conditions at both ends are fixed supports, which are the same as the boundary conditions of the finite element analysis. The midpoint displacement w1 is calculated, and the converted midpoint displacement is w2 according to the conversion coefficient; w2 is corrected using the results of the finite element analysis.

2. The method for preparing a jujube-shaped double-layer deformable honeycomb structure according to claim 1, characterized in that: The specific steps to modify w2 using the results of finite element analysis are: 1) The jujube-shaped double-layer deformable honeycomb structure is modeled using shell elements, with the horizontal axis as the x-axis, the vertical axis as the y-axis, and the z-axis determined according to the right-hand rule; 2) Input structural parameters and material parameters; 3) Set the left and right boundary supports according to the actual usage; 4) Treat the out-of-plane aerodynamic load as a linear load acting in the z direction of the corresponding node; 5) Select the unit type as S8R and divide the grid; 6) Submit the work to calculate the midpoint displacement w3, and the correction coefficient is η=w2 / w3; if the deformation at the midpoint exceeds the specified requirements, adjust m, h or t; h does not exceed the specified thickness of the flexible skin; based on the corrected B, determine m, t and h according to c+u to meet the honeycomb transverse pore requirements, B=mt; According to the material mechanics, the end of the cantilever beam is subjected to lateral deformation u and the end angle is 0, and the load required at the end of the bending plate is solved. and the stress at the root of the bending plate Check the strength of the bending plate, the total driving force F = 2nf.

3. The method for preparing a jujube-shaped double-layer deformable honeycomb structure according to claim 1, characterized in that: The bending plates on the flexible unit are divided into an upper bending plate and a lower bending plate, with a connecting plate (5) in the middle. According to the different bending directions of the upper bending plate and the lower bending plate at the same level, the flexible unit can be divided into an A-type flexible unit and a B-type flexible unit. The A-type flexible unit and the B-type flexible unit can form unit cell structures of different shapes; the pore length of the A-type jujube-shaped unit cell is 2(a+2b), and the pore length of the B-type jujube-shaped unit cell is a+2b; the conversion coefficient of the A-type jujube-shaped unit cell is 1 / 4, and the conversion coefficient of the B-type jujube-shaped unit cell is 5 / 32.

4. The method for preparing a jujube-shaped double-layer deformable honeycomb structure according to claim 1, characterized in that: The flexible unit comprises a bending plate, a connecting plate, a slit and a crack-stopping hole; the flexible unit has an initial bending shape, and the lateral distance between the end of the bending plate and the connecting plate is c / 2; the A-type flexible unit forms a slit with a length of b and a width of d at h / 2 in the width direction, and cuts the bending plate to form two layers of bending plates, namely, an upper bending plate (1) at the upper end, a lower bending plate (2) at the upper end, an upper bending plate (3) at the lower end, and a lower bending plate (4) at the lower end; when the end is subjected to an in-plane load, the upper bending plate at the upper end bends to the right, the upper bending plate at the lower end bends to the left, the upper bending plate at the upper end bends to the left, and the lower bending plate at the lower end bends to the right; The B-type flexible unit forms two slits of length b and width d at 1 / 4h and 3 / 4h in the width direction, cutting the bending plate to form three levels of bending plates; namely, the upper bending plate (1) at the upper end, the lower bending plate (2) at the upper end, the upper bending plate (3) at the lower end, the lower bending plate (4) at the lower end, the middle bending plate (8) at the upper end, and the middle bending plate (9) at the lower end. When the ends are subjected to in-plane loads, the upper bending plate and the lower bending plate bend to the right, the upper middle bending plate and the lower middle bending plate bend to the left, and the upper lower bending plate and the lower lower bending plate bend to the right. A crack stop hole (7) is set at the junction of the bending plate and the connecting plate, that is, at the bottom of the bending plate, and the diameter D of the crack stop hole is more than 3 times the width d of the slit (6).

5. The method for preparing a jujube-shaped double-layer deformable honeycomb structure according to claim 1, characterized in that: The longitudinal flexible unit of the jujube-shaped double-layer deformable honeycomb structure is composed of m flexible plates with a length of n(a+2b), a width of h and a thickness of t. The flexible plates of each flexible unit are arranged in the manner of b, a, 2b, a, 2b, a, ..., 2b, a, b, by marking, punching stop holes and cutting. The diameter of the stop holes is more than 3 times the width of the cut. When making type A longitudinal flexible plates, the cut position is at h / 2 of the wide side. When making type B longitudinal flexible plates, the cut position is at h / 4 and 3h / 4 of the wide side.

6. The method for preparing a jujube-shaped double-layer deformable honeycomb structure according to claim 4, characterized in that: The initial bending shape stamping process includes: The upper bending plate and the lower bending plate of the same layer of the A-type longitudinal flexible plate have opposite bending directions. The bending direction of the upper bending plate in the odd-numbered columns is first right and then left, and the bending direction of the lower bending plate is first left and then right. The bending direction of the upper bending plate in the even-numbered columns is first left and then right, and the bending direction of the lower bending plate is first right and then left. The upper and lower bent plates of the same layer of the B-type longitudinal flexible plate have the same bending direction. The upper and lower bent plates of the odd-numbered columns bend to the right, and the middle bent plates bend to the left. The upper and lower bent plates of the even-numbered columns bend to the left, and the middle bent plates bend to the right. The stamping process must also meet the requirements of the initial distance c between the connecting plates of adjacent flexible plates and the tangency of the ends of the bent plates of adjacent flexible units; then the bent plates on the same layer of adjacent longitudinal flexible plates that need to be connected are welded, with a weld width of 2mm; when a lateral pulling force is applied to the support seat, a jujube-shaped double-layer deformable honeycomb structure is automatically formed.

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