CN104118151B - A kind of nacreous layer bionical vibration isolation material of broad band low frequency - Google Patents

Abstract

The invention discloses the bionical vibration isolation material of the nacreous layer of a kind of broad band low frequency, have a periodic structure, described periodic structure is made up of multiple basic structural units；Described basic structural unit includes the structure sheaf one being sequentially connected with along described periodic structure short transverse, articulamentum and structure sheaf two；Described articulamentum includes four secondary articulamentums in 2 × 2 matrix arrangement, and described four secondary articulamentums equidistantly arrange；Described secondary articulamentum includes a structure sheaf three and the articulamentum one of the top and bottom laying respectively at described structure sheaf three and articulamentum two；Described structure sheaf one, the material of described structure sheaf two and described structure sheaf three is material one, and the material of described articulamentum one and described articulamentum two is material two；The density of described material one is y_mat, 1 × 10³kg/m³≤y_mat≤20×10³kg/m³；The elastic modelling quantity of described material two is x_mat, 0.1Mpa≤x_mat≤100Mpa.The basic structural unit of the present invention has comparatively wide low bandgap and the programmable feature of band gap.

Description

A kind of nacreous layer bionical vibration isolation material of broad band low frequency

Technical field

The present invention relates to a kind of vibration isolation material, the specifically bionical vibration isolation material of the nacreous layer of a kind of broad band low frequency.

Background technology

Traditional damping technology core is to adopt damping vibration attenuation material, such as rubber, the materials such as resin, these materials are usually single-phase macromolecular material or the mixture of several macromolecular material, macromolecular material is by long, molecular composition that is soft curling and that tangle mutually, intermolecular also chemical bond coupling once in a while, and there is significantly high damped coefficient.Damping is the process dissipated by the energy that the energy conversion of system vibration in vibration processes is other forms, can pass through the internal friction between its internal macromolecule, and the energy of other forms includes heat energy, electric energy, magnetic energy etc..Damping can reduce the vibratory output of system, the amount of being hit and noise level.During free vibration, damping makes amplitude constantly decay.During forced vibration, damping consumes excitation to system work, reduces the amplitude of system.

Viscoelastic damping damping material has the characteristic of viscous liquid loss of energy under flow regime and the characteristic of elastic solid material storage energy concurrently, can pass through viscous note structurally, form big composite damping structure, to reach the purpose of vibration damping.

Conventional damper damping material based on internal friction Energy Dissipation Mechanism, not notable for low frequency vibration damping effect, and there is the not programmable problem of object tape broadband, field for different bandwidth frequency needs to design different types of material, and vibration damping scope can not cover vibration and broader choacoustic frequency scope.For special dimension, it is desirable to effectiveness in vibration suppression is notable, it is possible to the elastic wave in shielding particular frequency range, the friction processing environment that such as high-accuracy system of processing needs, the sound shielding environment in particular frequency range, conventional damper damping material can not be competent at.

Summary of the invention

According to conventional damper damping material set forth above, low frequency vibration damping effect is not notable, and there is the not programmable technical problem of object tape broadband, and the bionical vibration isolation material of nacreous layer of a kind of broad band low frequency is provided.

The technological means that the present invention adopts is as follows:

The bionical vibration isolation material of nacreous layer of a kind of broad band low frequency, has a periodic structure, and described periodic structure is made up of multiple basic structural units；

Described basic structural unit includes the structure sheaf one being sequentially connected with along described periodic structure short transverse, articulamentum and structure sheaf two；

Described articulamentum includes four secondary articulamentums in 2 × 2 matrix arrangement, and described four secondary articulamentums equidistantly arrange, owing to isolation frequency scope is not produced impact by the size of spacing, therefore, as long as the present invention ensures that described spacing exists；

Described secondary articulamentum includes a structure sheaf three and the articulamentum one of the top and bottom laying respectively at described structure sheaf three and articulamentum two；

Described structure sheaf one, the material of described structure sheaf two and described structure sheaf three is material one, and the material of described articulamentum one and described articulamentum two is material two；

The density of described material one is y_mat, 1 × 10³kg/m³≤y_mat≤20×10³kg/m³；

The elastic modelling quantity of described material two is x_mat, 0.1Mpa≤x_mat≤100Mpa。

Further, the outer surface of described periodic structure is coated with damping material.

Further, described periodic structure and the alternately laminated setting of damping material, i.e. one layer of described periodic structure, one layer of alternately laminated setting of damping material.

Further, described basic structural unit with m × m × n dot matrix morphologic arrangement, wherein m and n respectively positive integer be more than or equal to 1；

The bottom surface of described basic structural unit is square, and described periodic structure is of a size of ma × ma × nb, and wherein a is the bottom surface length of side of described basic structural unit, and b is the height of described basic structural unit；

The bottom surface of described structure sheaf one is square, and the bottom surface length of side of described structure sheaf one is a；

The bottom surface of described structure sheaf two is square, and the bottom surface length of side of described structure sheaf two is a；

The bottom surface of described structure sheaf three is square, and the bottom surface length of side of described structure sheaf three is a₁, 2a₁=a；

The bottom surface of described articulamentum one is square, and the bottom surface length of side of described articulamentum one is a₂；

The bottom surface of described articulamentum two is square, and the bottom surface length of side of described articulamentum two is a₂；

The height of described structure sheaf three is b₁, the height of described structure sheaf one and the height of described structure sheaf two are b₁/ 2, the height of described articulamentum one and the height of described articulamentum two are b₂, 2b₁+2b₂=b；,

The connecting length of described articulamentum one and described structure sheaf one, the connecting length of described articulamentum one and described structure sheaf three, described articulamentum two is z with the connecting length of described structure sheaf three and the connecting length of described articulamentum two and described structure sheaf two_geo, z_geo=a₂。

A kind of method that present invention also offers bionical vibration isolation material of nacreous layer designing above-mentioned a kind of broad band low frequency, it is characterised in that:

1)x_matAnd y_matConfirmation

Pass through formula $f_{\mathrm{upper}}=f_1^{\mathrm{up}}\left(x_{\mathrm{mat}}\right)$ With $f_{\mathrm{lower}}=\frac{f_1^{\mathrm{low}}\left(x_{\mathrm{mat}}\right)*f_2^{\mathrm{low}}\left(y_{\mathrm{mat}}\right)}{n_{\mathrm{mat}}}$ Calculate x_matAnd y_mat,

$f_1^{\mathrm{up}}\left(x_{\mathrm{mat}}\right)=0.0248x_{\mathrm{mat}}^3-4.7808x_{\mathrm{mat}}^2+362.47x_{\mathrm{mat}}+425.075,$

$f_1^{\mathrm{low}}\left(x_{\mathrm{mat}}\right)=0.0224x_{\mathrm{mat}}^3-4.3173x_{\mathrm{mat}}^2+331.8x_{\mathrm{mat}}+45.4886,$

$f_2^{\mathrm{low}}\left(y_{\mathrm{mat}}\right)=-0.121y_{\mathrm{mat}}^3+4.945y_{\mathrm{mat}}^2-68.196y_{\mathrm{mat}}+449.75,$

n_mat=299.28,

f_upperFor the coboundary of isolation frequency scope, f_lowerLower boundary for isolation frequency scope；

2) a, b, a₁, a₂, b₁And b₂Confirmation

By formula a_upper=32729.8/f_upper, a_lower=5909.1/f_lowerAnd b=2b₁+2b₂Calculate a and b,

Work as a_upper=a_lowerTime, a=a_upper=a_lower；

Work as a_upper≠a_lowerTime, a=(a_upper+a_lower)/2；

Wherein, a/b₁=x_geo, a₂/b₂=y_geo, a₂=z_geo, 1≤x_geo≤ 9,2≤y_geo≤ 8,0 < z_geo≤30mm；

Pass through formula $f_{\mathrm{upper}}=g_1^{\mathrm{up}}\left(y_{\mathrm{geo}}\right)$ With $f_{\mathrm{lower}}=\frac{g_1^{\mathrm{low}}\left(x_{\mathrm{geo}}\right)*g_2^{\mathrm{low}}\left(y_{\mathrm{geo}}\right)*g_3^{\mathrm{low}}\left(z_{\mathrm{geo}}\right)}{n_{\mathrm{geo}}}$ Calculate x_geo, y_geoAnd z_geo,

Assume parameter x_geoAnd z_geoProduce similar band gap impact effect, namely

$g_1^{\mathrm{low}}\left(x_{\mathrm{geo}}\right)=g_3^{\mathrm{low}}\left(z_{\mathrm{geo}}\right),$ Owing to passing through $f_{\mathrm{upper}}=g_1^{\mathrm{up}}\left(y_{\mathrm{geo}}\right)$ May determine that parameter y_geo, only remaining x_geoAnd z_geoParameter is undetermined, but is becauseOnly one of which equation, it is impossible to determine two undetermined parameters, say, that can there is multiple situation many groups solution and all meet equationThe present invention only provides the straightforward procedure determining one of which solution, so carrying out such hypothesis；

$g_1^{\mathrm{up}}\left(y_{\mathrm{geo}}\right)=-0.6625y_{\mathrm{geo}}^2+85.765y_{\mathrm{geo}}+298.68,$

$g_1^{\mathrm{low}}\left(x_{\mathrm{geo}}\right)=-1.9643x_{\mathrm{geo}}^2+46.3029x_{\mathrm{geo}}-12.8063,$

$g_2^{\mathrm{low}}\left(y_{\mathrm{geo}}\right)=-2.075y_{\mathrm{geo}}^2+54.27y_{\mathrm{geo}}-15.82,$

$g_3^{\mathrm{low}}\left(z_{\mathrm{geo}}\right)=-0.0994z_{\mathrm{geo}}^2+10.185z_{\mathrm{geo}}-7.49,$

n_geo=7126.Further, as given frequency f, formula is passed through

Calculate f_upperAnd f_lower, wherein f is the mid frequency of isolation frequency scope, it is assumed that a=a_upper=a_lower。

Compared with prior art, the basic structural unit of the present invention has comparatively wide low bandgap, and material parameter and geometric parameter can be adjusted according to the vibration environment of vibration isolation material application, such that it is able to adjust the target bandgap range of vibration isolation material, the present invention has the designability of band gap, vibration isolating effect highly significant in bandgap range, can be designed for varying environment, reach the effect to elastic wave shielding, the present invention can also combine with traditional damping material, improves vibration isolating effect further.

The present invention can be widely popularized in fields such as vibration isolation materials for the foregoing reasons.

Accompanying drawing explanation

Below in conjunction with the drawings and specific embodiments, the present invention is further detailed explanation.

Fig. 1 is the basic structural unit space schematic diagram of the present invention.

Fig. 2 is the top view of the basic structural unit of the present invention.

Fig. 3 is the basic structural unit side view of the present invention.

Fig. 4 is the specific embodiment of the present invention and other materials carries out longitudinal transfer curve figure of contrasting.

Fig. 5 is the specific embodiment of the present invention and other materials carries out the lateral transport performance diagram that contrasts.

The three-dimensional energy band graph of a relation of the specific embodiment of the present invention during Fig. 6.

Fig. 7 is the bionical vibration isolation material structural representation of nacreous layer of a kind of broad band low frequency being provided with mounting seat.

Detailed description of the invention

As depicted in figs. 1 and 2, the bionical vibration isolation material of nacreous layer of a kind of broad band low frequency, there is a periodic structure, described periodic structure is made up of multiple basic structural units；

Described basic structural unit includes the structure sheaf 1 being sequentially connected with along described periodic structure short transverse, articulamentum and structure sheaf 22；

Described articulamentum includes four secondary articulamentums in 2 × 2 matrix arrangement, and described four secondary articulamentums equidistantly arrange, and spacing is 5mm；

Described secondary articulamentum includes a structure sheaf 33 and the articulamentum 1 of the top and bottom laying respectively at described structure sheaf 33 and articulamentum 25, and described spacing is the 5mm spacing referring between four described structure sheafs 33；

Described structure sheaf 1, the material of described structure sheaf 22 and described structure sheaf 33 is material one, and the material of described articulamentum 1 and described articulamentum 25 is material two；

The density of described material one is y_mat, 1 × 10³kg/m³≤y_mat≤20×10³kg/m³；

The elastic modelling quantity of described material two is x_mat, 0.1Mpa≤x_mat≤100Mpa。

Described basic structural unit is with m × m × n dot matrix morphologic arrangement, wherein m=n=3；

The bottom surface of described basic structural unit is square, and described periodic structure is of a size of 3a × 3a × 3b, and wherein a is the bottom surface length of side of described basic structural unit, and b is the height of described basic structural unit；

The bottom surface of described structure sheaf 1 is square, and the bottom surface length of side of described structure sheaf 1 is a；

The bottom surface of described structure sheaf 22 is square, and the bottom surface length of side of described structure sheaf 22 is a；

The bottom surface of described structure sheaf 33 is square, and the bottom surface length of side of described structure sheaf 33 is a₁, 2a₁=a；

The bottom surface of described articulamentum 1 is square, and the bottom surface length of side of described articulamentum 1 is a₂；

The bottom surface of described articulamentum 25 is square, and the bottom surface length of side of described articulamentum 25 is a₂；

The height of described structure sheaf 33 is b₁, the height of described structure sheaf 1 and the height of described structure sheaf 22 are b₁/ 2, the height of described articulamentum 1 and the height of described articulamentum 25 are b₂, 2b₁+2b₂=b；

The connecting length of described articulamentum 1 and described structure sheaf 1, the connecting length of described articulamentum 1 and described structure sheaf 33, described articulamentum 25 is z with the connecting length of described structure sheaf 33 and the connecting length of described articulamentum 25 and described structure sheaf 22_geo, z_geo=a₂。

Given frequency f is 276Hz, passes through computing formula:a_upper=32729.8/f_upper, a_lower=5909.1/f_lowerAnd a=a_upper=a_lower,

Can obtain $a=\frac{32729.8+5909.1}{2\&times;276}=70\mathrm{mm},$

And then obtain f_upper=467.5685Hz, f_lower=84.4155Hz,

x_matAnd y_matConfirmation:

Pass through formula $f_{\mathrm{upper}}=f_1^{\mathrm{up}}\left(x_{\mathrm{mat}}\right)$ With $f_{\mathrm{lower}}=\frac{f_1^{\mathrm{low}}\left(x_{\mathrm{mat}}\right)*f_2^{\mathrm{low}}\left(y_{\mathrm{mat}}\right)}{n_{\mathrm{mat}}}$ Calculate x_matAnd y_mat,

$f_1^{\mathrm{up}}\left(x_{\mathrm{mat}}\right)=0.0248x_{\mathrm{mat}}^3-4.7808x_{\mathrm{mat}}^2+362.47x_{\mathrm{mat}}+425.075,$

$f_1^{\mathrm{low}}\left(x_{\mathrm{mat}}\right)=0.0224x_{\mathrm{mat}}^3-4.3173x_{\mathrm{mat}}^2+331.8x_{\mathrm{mat}}+45.4886,$

$f_2^{\mathrm{low}}\left(y_{\mathrm{mat}}\right)=-0.121y_{\mathrm{mat}}^3+4.945y_{\mathrm{mat}}^2-68.196y_{\mathrm{mat}}+449.75,$

n_mat=299.28,

Due to equationAt 0.1Mpa≤x_matIt is dull in≤100Mpa, it is possible to try to achieve x_mat=0.1174MPa, similar to the elastic modelling quantity of silicone rubber, described articulamentum 1 and described articulamentum 25 choose silicone rubber as using material.

$\frac{f_1^{\mathrm{low}}\left(x_{\mathrm{mat}}\right)*f_2^{\mathrm{low}}\left(y_{\mathrm{mat}}\right)}{n_{\mathrm{mat}}}=84.4155\mathrm{Hz},$ Due to equation $\frac{f_1^{\mathrm{low}}\left(x_{\mathrm{mat}}\right)*f_2^{\mathrm{low}}\left(y_{\mathrm{mat}}\right)}{n_{\mathrm{mat}}}$ 1 × 10³kg/m³≤y_mat≤20×10³kg/m³It is inside dull, it is possible to try to achieve y_mat=2.6975 × 10³kg/m³, similar to the density of aluminum, described structure sheaf 1, described structure sheaf 22 and described structure sheaf 33 choose aluminum as using material.

A, b, a₁, a₂, b₁And b₂Confirmation:

By formula a_upper=32729.8/f_upper, a_lower=5909.1/f_lowerAnd b=2b₁+2b₂Calculate a and b, a=a_upper=a_lower=70mm；

Wherein, a/b₁=x_geo, a₂/b₂=y_geo, a₂=z_geo, 1≤x_geo≤ 9,2≤y_geo≤ 8,0 < z_geo≤30mm；

Pass through formula $f_{\mathrm{upper}}=g_1^{\mathrm{up}}\left(y_{\mathrm{geo}}\right)$ With $f_{\mathrm{lower}}=\frac{g_1^{\mathrm{low}}\left(x_{\mathrm{geo}}\right)*g_2^{\mathrm{low}}\left(y_{\mathrm{geo}}\right)*g_3^{\mathrm{low}}\left(z_{\mathrm{geo}}\right)}{n_{\mathrm{geo}}}$ Calculate x_geo, y_geoAnd z_geo,

$g_1^{\mathrm{up}}\left(y_{\mathrm{geo}}\right)=-0.6625y_{\mathrm{geo}}^2+85.765y_{\mathrm{geo}}+298.68,$

$g_1^{\mathrm{low}}\left(x_{\mathrm{geo}}\right)=-1.9643x_{\mathrm{geo}}^2+46.3029x_{\mathrm{geo}}-12.8063,$

$g_2^{\mathrm{low}}\left(y_{\mathrm{geo}}\right)=-2.075y_{\mathrm{geo}}^2+54.27y_{\mathrm{geo}}-15.82,$

$g_3^{\mathrm{low}}\left(z_{\mathrm{geo}}\right)=-0.0994z_{\mathrm{geo}}^2+10.185z_{\mathrm{geo}}-7.49,$

n_geo=7126；

Due to equationAt 2≤y_geoIt is dull in≤8, it is possible to try to achieve y_geo=2, thenz_geo=a₂, 2b₂=a₂；

$\frac{g_1^{\mathrm{low}}\left(x_{\mathrm{geo}}\right)*g_2^{\mathrm{low}}\left(y_{\mathrm{geo}}\right)*g_3^{\mathrm{low}}\left(z_{\mathrm{geo}}\right)}{n_{\mathrm{geo}}}84.4155\mathrm{Hz},$

Abbreviation obtainsAssume parameter x_geoAnd z_geoProduce similar band gap impact effect, namely

$g_1^{\mathrm{low}}\left(x_{\mathrm{geo}}\right)=84.4134\mathrm{Hz},g_3^{\mathrm{low}}\left(z_{\mathrm{geo}}\right)=84.4134\mathrm{Hz},$

Due to equationAt 1≤x_geoIt is dull in≤9, it is possible to try to achieve x_geo=2.3299, due to equationAt 0 < z_geoIt is dull in≤30mm, it is possible to try to achieve z_geo=9.9994mm.Such that it is able to obtain b₁=30.0442mm, a₂=9.9994mm, b₂=4.9997mm,B=2b₁+2b₂=70.0878mm.

The bionical vibration isolation material of nacreous layer (being illustrated as three-dimensional nacreous layer material) and the aluminium block (being illustrated as aluminum) of described a kind of broad band low frequency, silicone rubber block (is illustrated as silicone rubber) and the simple stratified material of aluminium sheet and the alternately laminated setting of silicane rubber plate (being illustrated as the simple stratified material of aluminum-silicone rubber) performance contrasts, examining or check the transmission characteristic of its vertical and horizontal, line number of going forward side by side value is tested.Transmission coefficient and outfan dynamic respond are divided by input dynamic respond, usual response curve describes with logarithmic form, comparing result is as shown in Figure 4 and Figure 5, from figure, curve can be seen that, the bionical vibration isolation material of nacreous layer of described a kind of broad band low frequency is in the frequency range of low-frequency ultra-wideband gap, being laterally or longitudinally all have significant effectiveness in vibration suppression, its attenuating can reach 200dB, is far longer than other three kinds of materials.

As shown in Figure 6, the letter of abscissa is the wave vector characteristic point in the first brief Brillouin zone, namely characterizes complete three-dimensional direction of wave travel；Curve in Fig. 6 is dispersion curve or band structure, characterizes the relation of wave vector and frequency, it can be seen that the spread speed of different frequency ripple and direction；Under three-dimensional situation, the bionical vibration isolation material of nacreous layer of described a kind of broad band low frequency there will be comparatively wide low bandgap (84.4155Hz-467.5685Hz), three-dimensional material can have more rich dispersion relation at low frequency region, and at high-frequency region, a plurality of straight band occurs equally, thus multiple more continuous band gap occurs.This can cause that the frequency decay district of non-constant width occurs, it is adaptable to the needs of engineering vibration and noise reducing.

As it is shown in fig. 7, the upper and lower surface of the bionical vibration isolation material of nacreous layer of described a kind of broad band low frequency is respectively equipped with mounting seat.

The above; it is only the present invention preferably detailed description of the invention; but protection scope of the present invention is not limited thereto; any those familiar with the art is in the technical scope that the invention discloses; it is equal to replacement according to technical scheme and inventive concept thereof or is changed, all should be encompassed within protection scope of the present invention.

Claims (4)

1. the bionical vibration isolation material of the nacreous layer of a broad band low frequency, it is characterised in that having a periodic structure, described periodic structure is made up of multiple basic structural units；

Described basic structural unit includes the structure sheaf one being sequentially connected with along described periodic structure short transverse, articulamentum and structure sheaf two；

Described articulamentum includes four secondary articulamentums in 2 × 2 matrix arrangement, and described four secondary articulamentums equidistantly arrange；

Described secondary articulamentum includes a structure sheaf three and the articulamentum one of the top and bottom laying respectively at described structure sheaf three and articulamentum two；

Described structure sheaf one, the material of described structure sheaf two and described structure sheaf three is material one, and the material of described articulamentum one and described articulamentum two is material two；

The density of described material one is y_mat, 1 × 10³kg/m³≤y_mat≤20×10³kg/m³；

The elastic modelling quantity of described material two is x_mat, 0.1Mpa≤x_mat≤100Mpa；

The outer surface of described periodic structure is coated with damping material；

Described periodic structure and the alternately laminated setting of damping material.

2. the bionical vibration isolation material of nacreous layer of a kind of broad band low frequency according to claim 1, it is characterised in that: described basic structural unit with m × m × n dot matrix morphologic arrangement, wherein m and n respectively positive integer be more than or equal to 1；

The bottom surface of described basic structural unit is square, and described periodic structure is of a size of ma × ma × nb, and wherein a is the bottom surface length of side of described basic structural unit, and b is the height of described basic structural unit；

The bottom surface of described structure sheaf one is square, and the bottom surface length of side of described structure sheaf one is a；

The bottom surface of described structure sheaf two is square, and the bottom surface length of side of described structure sheaf two is a；

The bottom surface of described structure sheaf three is square, and the bottom surface length of side of described structure sheaf three is a₁, 2a₁=a；

The bottom surface of described articulamentum one is square, and the bottom surface length of side of described articulamentum one is a₂；

The bottom surface of described articulamentum two is square, and the bottom surface length of side of described articulamentum two is a₂；

The height of described structure sheaf three is b₁, the height of described structure sheaf one and the height of described structure sheaf two are b₁/ 2, the height of described articulamentum one and the height of described articulamentum two are b₂, 2b₁+2b₂=b；

The connecting length of described articulamentum one and described structure sheaf one, the connecting length of described articulamentum one and described structure sheaf three, described articulamentum two is z with the connecting length of described structure sheaf three and the connecting length of described articulamentum two and described structure sheaf two_geo, z_geo=a₂。

3. the method for the bionical vibration isolation material of nacreous layer of a kind of broad band low frequency designed described in claim 2, it is characterised in that:

1)x_matAnd y_matConfirmation

By formula f_upper=f₁ ^up(x_mat) andCalculate x_matAnd y_mat,

$f_1^{up}\left(x_{mat}\right)=0.0248x_{mat}^3-4.7808x_{mat}^2+362.47x_{mat}+425.075,$

$f_1^{low}\left(x_{mat}\right)=0.0224x_{mat}^3-4.3173x_{mat}^2+331.8x_{mat}+45.4886,$

$f_2^{low}\left(y_{mat}\right)=-0.121y_{mat}^3+4.945y_{mat}^2-68.196y_{mat}+449.75,$

n_mat=299.28,

f_upperFor the coboundary of isolation frequency scope, f_lowerLower boundary for isolation frequency scope；

2) a, b, a_1,, a₂, b₁And b₂Confirmation

By formula a_upper=32729.8/f_upper, a_lower=5909.1/f_lowerAnd b=2b₁+2b₂Calculate a and b,

Work as a_upper=a_lowerTime, a=a_upper=a_lower；

Work as a_upper≠a_lowerTime, a=(a_upper+a_lower)/2；

Wherein, a/b₁=x_geo, a₂/b₂=y_geo, a₂=z_geo, 1≤x_geo≤ 9,2≤y_geo≤ 8,0 < z_geo≤30mm；

Pass through formula $f_{upper}=g_1^{up}\left(y_{geo}\right)$ With $f_{lower}=\frac{g_1^{low}\left(x_{geo}\right)*g_2^{low}\left(y_{geo}\right)*g_3^{low}\left(z_{geo}\right)}{n_{geo}}$ Calculate x_geo, y_geoAnd z_geo,

Assume parameter x_geoAnd z_geoProduce similar band gap impact effect, namely

$g_1^{low}\left(x_{geo}\right)=g_3^{low}\left(z_{geo}\right),$

$g_1^{up}\left(y_{geo}\right)=-0.6625y_{geo}^2+85.765y_{geo}+298.69,$

$g_1^{low}\left(x_{geo}\right)=-1.9643x_{geo}^2+46.3029x_{geo}-12.8063,$

$g_2^{low}\left(y_{geo}\right)=-2.075y_{geo}^2+54.27y_{geo}-15.82,$

$g_3^{low}\left(z_{geo}\right)=-0.0994z_{geo}^2+10.185z_{geo}-7.49,$

n_geo=7126.

4. method according to claim 3, it is characterised in that: as given frequency f, pass through formula

Calculate f_upperAnd f_lower, wherein f is the mid frequency of isolation frequency scope, it is assumed that a=a_upper=a_lower。