CN114838072A - Negative Poisson ratio honeycomb cell element and multi-cell structure introducing square function curved edge - Google Patents
Negative Poisson ratio honeycomb cell element and multi-cell structure introducing square function curved edge Download PDFInfo
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- CN114838072A CN114838072A CN202210577295.3A CN202210577295A CN114838072A CN 114838072 A CN114838072 A CN 114838072A CN 202210577295 A CN202210577295 A CN 202210577295A CN 114838072 A CN114838072 A CN 114838072A
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
- F16F1/00—Springs
- F16F1/02—Springs made of steel or other material having low internal friction; Wound, torsion, leaf, cup, ring or the like springs, the material of the spring not being relevant
- F16F1/025—Springs made of steel or other material having low internal friction; Wound, torsion, leaf, cup, ring or the like springs, the material of the spring not being relevant characterised by having a particular shape
Abstract
The invention discloses a negative Poisson ratio honeycomb cell element and a multi-cell structure with square function curved edges, which are characterized in that: comprises two symmetrically arranged square function curved edges which are concave towards a symmetric axis; two ends of each square function curved side are respectively connected with an equal-length straight side, and the two straight sides are arranged in parallel, so that the two square function curved sides and the two straight sides are arranged at intervals and connected end to form a closed structure. The plurality of cells extend in a transverse replica connection, and the plurality of cells are connected in a staggered manner in a vertical direction by sharing a curved edge. Better energy absorption capability and lower peak impact force can be achieved.
Description
Technical Field
The invention relates to the field of mechanics metamaterials, in particular to a negative Poisson ratio honeycomb structure with a square function curved edge introduced.
Background
The collision safety of automobiles has become a hot spot of the current domestic and foreign research, so that the related energy-absorbing structure and material are more and more paid attention. Compared with the traditional solid material, the honeycomb material can expand new design dimension from the interior thereof, and the performance of the honeycomb material can be influenced by changing the structure and arrangement mode of the interior. The negative Poisson ratio structure is a special structure formed by changing the internal structure form, and has a special negative Poisson ratio effect, namely the material is widened in a direction perpendicular to the stretching direction when being stretched and narrowed in a direction perpendicular to the compression direction when being compressed, so that the material has the characteristics of light weight, vibration isolation, high energy absorption, high damping and the like, and is expected to become one of indispensable materials in the fields of spaceflight, automobiles, military affairs and the like.
Under the action of impact load, different cell structure forms can have a remarkable influence on the local dynamic mechanical behavior of the material. At present, the research on the impact performance of the negative Poisson ratio structure is mainly focused on the concave hexagonal structure of the honeycomb structure, and the concave hexagon mainly has two types of traditional straight sides and sinusoidal curved sides at present. However, it has been found by comparison that there is room for improvement in both energy absorption capacity and peak impact force for the conventional hexagonal structure as well as the sinusoidal edge structure proposed by the applicant itself.
Disclosure of Invention
In view of the above technical problems, the present invention provides a negative poisson ratio honeycomb cell and a multi-cell structure with square function curved sides introduced, so as to achieve better energy absorption capability and lower peak impact force.
The technical problem to be solved by the invention is realized by the following technical scheme:
a negative poisson's ratio cellular cell incorporating a square function curved edge, characterized by: comprises two symmetrically arranged square function curved edges which are concave towards a symmetric axis; two ends of each square function curved side are respectively connected with a straight side with equal length, the two straight sides are arranged in parallel, and an included angle formed by each square function curved side and the adjacent straight side in the cell element is smaller than 90 degrees, so that the two square function curved sides and the two straight sides are arranged at intervals and connected end to form a closed structure.
In the above technical solution, a part of the curved side of the square function is a segment extracted from the square function; the section is copied and then is connected to the tail of the section in a 180-degree rotating manner to form another section, and the length of the other section is twice that of the section; the other section is axially symmetrical or mirrored in the vertical direction to obtain a third section, and the tail part of the third section is connected with the head part of the first section to form an integral bilateral-symmetrical square function curved edge.
In the above-mentioned technical solution, a part of the curved side of the square function is a square function y ═ a · x 2 In the section of the extraction, A is the coefficient of the square function, and the value range of A is (0, 0.32).
In the above technical schemeThe length of a part of the curved side of the square function is equal to A.x from the square function y 2 The length of x within the interval (0,2.5) extracted in (c).
In the above-mentioned technical solution, a part of the curved side of the square function is selected from the square function y of 0.16 · x 2 One section of (1).
In the above technical solution, the cell is a flat or plate-shaped thin shell.
In the above technical solution, the preparation material of the cell element is metallic aluminum.
In the above technical solution, the cell element is manufactured by stamping, extruding or 3D printing.
A negative poisson's ratio cellular structure incorporating a square function curved edge, comprising a plurality of said cells; the plurality of cells extend in a transverse replica connection, and the plurality of cells are connected in a staggered manner in a vertical direction by sharing a curved edge.
Furthermore, a plurality of cell elements are connected in a vertical mode in a staggered mode by sharing a curved edge with half length.
Thus, the present invention provides a negative poisson's ratio honeycomb structure that introduces a square function curved edge. The single cell structure comprises a plurality of single cell structures, each single cell structure consists of two square function curved sides and two vertical sides, the curved sides are symmetrical up and down and left and right, the vertical arms at two sides are connected with the upper curved sides and the lower curved sides and are parallel, and the included angle between the curved sides and the vertical arms is less than 90 degrees; copying the cells along the horizontal direction, and performing staggered copying along the vertical direction to obtain a multi-cell structure; the invention has good negative Poisson ratio effect, can obviously reduce peak impact stress relative to a sine curved edge honeycomb structure when being impacted, and has more excellent energy absorption capability.
Compared with the prior art, the invention has the following advantages:
compared with the traditional concave hexagonal structure and the sinusoidal function curved edge honeycomb structure invented by the applicant at the earlier stage, the negative Poisson's ratio structure with the square function curved edge has stronger energy absorption capacity, and can obviously reduce the peak impact force.
Experimental data show that the square function curved edge configuration is superior to a sine function curved edge configuration in energy absorption level, and the peak impact force of the square function curved edge configuration is about 34.39% lower than that of the sine function curved edge configuration.
Experimental data show that the square function curved edge configuration is superior to the inner hexagon configuration in energy absorption level, and the peak impact force of the square function curved edge configuration is lower than that of the inner hexagon configuration by about 44.7%.
Therefore, the impact of the concave lines of the cell structure is changed, the energy absorption level is improved, and simultaneously, the peak impact force can be obviously reduced.
Drawings
The invention will be further described with reference to the accompanying drawings and examples, in which:
FIG. 1 is a schematic diagram of a square function curved edge negative Poisson ratio cell structure according to an embodiment of the present invention.
FIG. 2 is a schematic diagram of a process for forming a square function curved edge negative Poisson ratio cell structure according to an embodiment of the present invention.
FIG. 3 is a schematic view of an in-plane impact of a honeycomb multicellular structure in an embodiment of the present invention.
FIG. 4 is a graph showing the specific energy absorption of two honeycomb structures according to the present invention in a sine and square function with an impact of 10 m/s.
FIG. 5 is a graph showing the specific energy absorption of two honeycomb structures according to the present invention, with a 90m/s impact sine and square function.
FIG. 6 is a graphical representation of the stress strain of two honeycomb structures with a sinusoidal and a square function of the impact at 10m/s in an example of the invention.
FIG. 7 is a graph illustrating specific energy absorption of two honeycomb structures in accordance with an embodiment of the present invention in a hexagonal configuration and square function at an impact of 10 m/s.
FIG. 8 is a graphical illustration of the specific energy absorption of two honeycomb structures in a 90m/s impact internal hexagonal configuration and square function in an embodiment of the present invention.
FIG. 9 is a graphical representation of the stress strain of two honeycomb structures in an embodiment of the present invention in a hexagonal configuration and square function at 10m/s impact.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Referring to FIG. 1, the present invention will be described in detail with reference to the following drawings and examples:
as shown in FIG. 1, the unit cell configuration 110 with introduced square function curved sides implemented according to the present invention is composed of two square function curved sides (112 and 113) and two vertical sides 111, the curved sides 112 and 113 are symmetrical up and down and left and right, the vertical arms at two sides are connected with the upper and lower curved sides and are parallel, the length is h, and the included angle between the curved sides (112 and 113) and the vertical arm 110 is less than 90 degrees.
The cells 110 of fig. 1 are horizontally replicated and vertically interleaved to form the multi-cell structure 100, as shown in fig. 3.
In the above technical solution, the cell 110 is a flat or flat thin shell. A certain thickness can also be set according to the needs.
In the above technical solution, the preparation material of the cell element 110 is metal aluminum or other metal or nonmetal with energy absorption effect.
In the above technical solution, the cell element 110 is manufactured by stamping, extruding or 3D printing.
As shown in fig. 2, the basis function equation of the square function of the curved-edge clipping of the cell 110 is: y is A.x 2 Where A is the coefficient of the square function. And copying and overturning the curved side (one fourth of the horizontal straight line length l) of the square function in the (0,2.5) interval by 180 degrees, and performing axial symmetry along the vertical center line passing through the origin to obtain a 10mm square function curved side whole with the horizontal straight line length l, and replacing the 10mm square function curved side whole with the side of an inner hexagonal honeycomb cell with the length of 10mm and the width of 8mm to obtain the square function curved side negative Poisson's ratio honeycomb structure. The square function coefficient a has a value range of (0, 0.32).
In the exemplary embodiment in fig. 1 and 2, y is 0.16 · x 2 The curved edge of (2) was modeled and further studied.
For the honeycomb material, the energy absorption characteristic index can reflect the energy absorption capacity of the structure, and the specific energy absorption is the most important index for evaluating the energy absorption capacity of the structure, and the expression is as follows:
in the formula, E v The expression of the energy absorbed by the unit volume structure is
Δ ρ is the relative density of the honeycomb material, ρ s Is the density of the matrix material, epsilon cr Is the nominal strain, ε, at which the nominal stress reaches the first stress peak d For locking strain, the strain corresponding to the dense honeycomb material entering the densification stage is expressed as epsilon d ＝1-1.4(Δρ/ρ s )。
In order to compare the energy absorption characteristics of the square function curve honeycomb structure, a sinusoidal curved edge honeycomb structure is selected as a control group, and the two structures are subjected to dynamic model analysis by adopting Hypermesh/Ls-Dyna combined simulation.
Comparative example 1:
as shown in fig. 3, a test piece of a more square function curve honeycomb multicellular structure 100 is placed between two parallel rigid plates 2. The honeycomb structure 100 is made of aluminum metal material, and assuming that it is an ideal elastoplastic model, the out-of-plane thickness along the z-axis direction is 1mm, and the density is 2700kg/m 3 Young's modulus 69GPa, Poisson's ratio 0.33 and yield stress 76 GPa. To ensure convergence, 5 integration points were used in the thickness direction. The left and right rigid plates are rigid bodies with the density of 7850kg/m 3 The Young's modulus was 200 GPa. The fixed end rigid body is fixed, and all other directional degrees of freedom are limited. The rigid body of the impact end is in surface-to-surface contact with the honeycomb structure, and the friction coefficient is 0.2. To prevent the compressed honeycomb structure multi-cell structure 100 from penetrating the rigid body, the model applies a single-sided automatic contact algorithm. In order to prevent the honeycomb structure from bending out of the surface and impacting in the impact process, all out-of-surface displacement of the honeycomb structure is restrained. In addition, the impact end rigid plate is in a structure with constant speed of 10m/s and 90m/s to negative Poisson ratioImpact is performed.
The results are shown in FIGS. 4, 5, and 6: at the impact speed of 10m/s, the curves of the square function curved edge configuration and the sine function curved edge configuration are nearly similar in the impact starting stage, the specific energy absorption of the square function curved edge configuration is gradually higher than that of the sine function curved edge configuration along with the increase of the compression amount, and the square function curved edge configuration is always ahead of the sine function curved edge configuration in the subsequent compression process. At an impact speed of 90m/s, the two are more consistent than the energy absorption curve due to the enhanced inertia effect. Further observation of the stress-strain curve revealed that at v 10m/s, the peak impact stress for the square function curved edge configuration was 0.349MPa, while the peak impact stress for the sine function curved edge configuration was 0.532 MPa. Therefore, the square function curved edge configuration has a better energy absorption level than the sine function curved edge configuration, and the peak impact force of the square function curved edge configuration is about 34.39% lower than that of the sine function curved edge configuration.
Comparative example 2:
in order to compare the energy absorption characteristics of the square function curve honeycomb structure, an inner hexagonal honeycomb structure is selected as a comparison group, and the two structures are subjected to dynamic model analysis by adopting Hypermesh/Ls-Dyna combined simulation. As shown in fig. 3, a honeycomb test piece was placed between two parallel rigid plates. The honeycomb material is made of aluminum metal material, and is assumed to be an ideal elastic-plastic model, the out-of-plane thickness along the z-axis direction is 1mm, and the density is 2700kg/m 3 Young's modulus 69GPa, Poisson's ratio 0.33 and yield stress 76 GPa. To ensure convergence, 5 integration points were used in the thickness direction. The left and right rigid plates are rigid bodies with the density of 7850kg/m 3 The Young's modulus was 200 GPa. The fixed end rigid body is fixed, and all other directional degrees of freedom are limited. The rigid body of the impact end is in surface-to-surface contact with the honeycomb structure, and the friction coefficient is 0.2. To prevent the compressed honeycomb from penetrating the rigid body, the model applies a single-sided automatic contact algorithm. In order to prevent the honeycomb structure from bending out of the surface and impacting in the impact process, all out-of-surface displacement of the honeycomb structure is restrained. In addition, the impact end rigid plate impacts the negative Poisson ratio structure at constant speeds of 30m/s and 90m/s, respectively.
The results are shown in FIGS. 4, 5, and 6: under the two impact velocities of 30m/s and 90m/s, the specific energy absorption relation of the square function curved edge configuration and the internal hexagon configuration is consistent: the curves of the square function curved edge structure and the inner hexagon structure at the initial stage of the impact are nearly similar, and with the increase of the compression amount, after the strain exceeds 0.1, the specific energy absorption of the square function curved edge structure exceeds the inner hexagon structure, and the square function curved edge structure always leads the inner hexagon structure in the subsequent compression process. Further combining the force-displacement curve results, at v-30 m/s, the peak impact force for the square function curved edge configuration was 124.1N, while the peak impact force for the inner hexagon configuration was 224.3N. Therefore, the square function curved edge configuration has a better energy absorption level than the inner hexagon configuration, and the peak impact force of the square function curved edge configuration is lower than that of the inner hexagon configuration by about 44.7%.
It will be understood that modifications and variations can be made by persons skilled in the art in light of the above teachings and all such modifications and variations are intended to be included within the scope of the invention as defined in the appended claims.
Claims (10)
1. A negative poisson's ratio cellular cell incorporating a square function curved edge, characterized by: comprises two symmetrically arranged square function curved edges which are concave towards a symmetric axis; two ends of each square function curved side are respectively connected with a straight side with equal length, the two straight sides are arranged in parallel, and an included angle formed by each square function curved side and the adjacent straight side in the cell element is smaller than 90 degrees, so that the two square function curved sides and the two straight sides are arranged at intervals and connected end to form a closed structure.
2. The negative poisson's ratio cellular cell of claim 1, wherein: one part of the curved side of the square function is a section extracted from the square function; the section is copied and then is connected to the tail of the section in a 180-degree rotating manner to form another section, and the length of the other section is twice that of the section; the other section is axially symmetrical or mirrored in the vertical direction to obtain a third section, and the tail part of the third section is connected with the head part of the first section to form an integral bilateral-symmetrical square function curved edge.
3. The negative poisson's ratio cellular cell of claim 1, wherein: part of the curved side of the square function is a square function y ═ A · x 2 In the section of the extraction, A is the coefficient of the square function, and the value range of A is (0, 0.32).
4. The negative poisson's ratio cellular cell of claim 1, wherein: the length of a part of the curved side of the square function is equal to A.x from the square function y 2 The length of x within the interval (0,2.5) extracted in (c).
5. The negative poisson's ratio cellular cell of claim 1, wherein: part of the curved side of the square function is selected from the square function y which is 0.16 x 2 One section of (1).
6. The negative poisson's ratio cellular cell of claim 1, wherein: the cell is a plane or flat plate thin shell.
7. The negative poisson's ratio cellular cell of claim 1, wherein: the preparation material of the cell element is metallic aluminum.
8. The negative poisson's ratio cellular cell of claim 1, wherein: the cell element is manufactured by stamping, extruding or 3D printing and forming.
9. A negative poisson's ratio cellular structure incorporating a square function curved edge, comprising a plurality of cells according to any one of claims 1 to 8; the plurality of cells extend in a transverse replica connection, and the plurality of cells are connected in a staggered manner in a vertical direction by sharing a curved edge.
10. The negative poisson's ratio cellular structure incorporating square function curved edges as claimed in claim 8 wherein the plurality of cells are vertically interconnected by sharing a half length curved edge.
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| CN115199693A (en) * | 2022-09-16 | 2022-10-18 | 南京航空航天大学 | Optimize reentrant corner constitutional unit and panel |
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