阅读说明：本技术 一种具有双自由度局域共振单元的变截面声学超材料梁 (Variable cross-section acoustic metamaterial beam with two-degree-of-freedom local resonance unit ) 是由 温舒瑞 李凤明 熊远皓 郝帅民 于 2019-10-22 设计创作，主要内容包括：一种具有双自由度局域共振单元的变截面声学超材料梁,属于机械振动和噪声控制技术领域,主要为了解决现有技术中的等截面声学超材料的局域共振带隙带宽窄,导致其减振降噪的有效频率范围小,从而限制了声学超材料在工程实际应用的问题,本发明中所述一种具有双自由度局域共振单元的变截面声学超材料梁包括M个阶梯梁组件,M为正整数,M个阶梯梁组件沿长度长方向依次设置,且相邻两个阶梯梁组件之间固定连接,每个阶梯梁组件包括一个阶梯梁主体和一个双自由度局域共振单元,本发明主要应用于声学超材料宽频禁带的减振降噪性能研究。(The invention discloses a variable cross-section acoustic metamaterial beam with a two-degree-of-freedom local resonance unit, which belongs to the technical field of mechanical vibration and noise control and mainly aims to solve the problem that the local resonance band gap of a constant cross-section acoustic metamaterial in the prior art is narrow, so that the effective frequency range of vibration and noise reduction of the constant cross-section acoustic metamaterial is small, and the practical application of the acoustic metamaterial in engineering is limited.)

1. A variable cross-section acoustic metamaterial beam with a two-degree-of-freedom local resonance unit is characterized in that: the variable cross-section acoustic metamaterial beam with the two-degree-of-freedom local resonance unit comprises M stepped beam assemblies, wherein M is a positive integer, the M stepped beam assemblies are sequentially arranged along the length direction, and the two adjacent stepped beam assemblies are fixedly connected.

2. The variable cross-section acoustic metamaterial beam with two-degree-of-freedom local resonance units as in claim 1, wherein: the ladder beam assembly comprises a ladder beam main body (1) and two-degree-of-freedom local resonance units (2), each two-degree-of-freedom local resonance unit (2) is fixedly connected to one ladder beam main body (1), and the ladder beam main bodies (1) in two adjacent ladder beam assemblies are fixedly connected.

3. The variable cross-section acoustic metamaterial beam with two-degree-of-freedom local resonance units as in claim 2, wherein: including thin roof beam section (11) and thick roof beam section (12) in a ladder beam main part (1), thin roof beam section (11) and thick roof beam section (12) are the cuboid, and the one end of thin roof beam section (11) sets up with the one end of thick roof beam section (12) is integrative, and the other end of thick roof beam section (12) in preceding ladder beam main part (1) and the other end fixed connection of thin roof beam section (11) in following ladder beam main part (1) in two adjacent ladder beam main parts (1).

4. The variable cross-section acoustic metamaterial beam with two-degree-of-freedom local resonance units as in claim 3, wherein: the two-degree-of-freedom local resonance unit (2) comprises an upper rubber column (21), a first mass block (22), a lower rubber column (23) and a second mass block (24), wherein the upper rubber column (21), the first mass block (22), the lower rubber column (23) and the second mass block (24) are cylinders, the upper rubber column (21), the first mass block (22), the lower rubber column (23) and the second mass block (24) are sequentially arranged from top to bottom, the bottom end of the upper rubber column (21) is bonded with the top end of the first mass block (22), the bottom end of the first mass block (22) is bonded with the top end of the lower rubber column (23), the bottom end of the lower rubber column (23) is bonded with the top end of the second mass block (24), and the top end of the upper rubber column (21) is bonded with the lower surface of the thin beam section (11).

5. The variable cross-section acoustic metamaterial beam with two-degree-of-freedom local resonance units as in claim 4, wherein: the end face diameter value of the upper rubber column (21) is L1, the width value of the lower surface of the thin beam section (11) is L2, and L1 is L2.

6. The variable cross-section acoustic metamaterial beam with two-degree-of-freedom local resonance units as in claim 5, wherein: the end face circle center of the upper rubber column (21) and the lower surface circle center of the thin beam section (11) are coaxially arranged.

7. The variable cross-section acoustic metamaterial beam with two-degree-of-freedom local resonance units as in claim 1, wherein: the end face diameter values of the upper rubber column (21), the first mass block (22), the lower rubber column (23) and the second mass block (24) are the same.

8. The variable cross-section acoustic metamaterial beam with two-degree-of-freedom local resonance units as in claim 1, wherein: the height of the upper rubber column (21) is smaller than that of the lower rubber column (23).

9. The variable cross-section acoustic metamaterial beam with two-degree-of-freedom local resonance units as in claim 1, wherein: the height of the second mass block (24) is smaller than that of the first mass block (22).

10. The variable cross-section acoustic metamaterial beam with two-degree-of-freedom local resonance units as in claim 1, wherein: the value range of M is 4-10.

Technical Field

The invention belongs to the technical field of mechanical vibration and noise control, and particularly relates to a variable cross-section acoustic metamaterial beam with a two-degree-of-freedom local resonance unit.

Background

The acoustic metamaterial is a local resonance type phonon crystal (periodic structure) with extraordinary physical properties (negative mass density, negative elastic modulus and the like) which are different from materials in the nature. The low-frequency local resonance band gap can be generated in a sub-wavelength band of the structure size, and the characteristic can realize the effect of blocking low-frequency vibration noise through a small-size structure. However, the local resonance band gap bandwidth of the traditional equal-section acoustic metamaterial is narrow, so that the effective frequency range of vibration and noise reduction is small, and the bottleneck greatly limits the wide application of the acoustic metamaterial in engineering practice.

Disclosure of Invention

The invention aims to solve the problem that the effective frequency range of vibration and noise reduction of an equal-section acoustic metamaterial is small due to the narrow local resonance band gap bandwidth of the equal-section acoustic metamaterial in the prior art, so that the practical application of the acoustic metamaterial in engineering is limited, and further provides a variable-section acoustic metamaterial beam with a two-degree-of-freedom local resonance unit.

A variable cross-section acoustic metamaterial beam with a two-degree-of-freedom local resonance unit comprises M stepped beam assemblies, wherein M is a positive integer, the M stepped beam assemblies are sequentially arranged along the length direction, and two adjacent stepped beam assemblies are fixedly connected;

furthermore, the stepped beam assembly comprises a stepped beam main body and two-degree-of-freedom local resonance units, each two-degree-of-freedom local resonance unit is fixedly connected to one stepped beam main body, and the stepped beam main bodies in two adjacent stepped beam assemblies are fixedly connected;

furthermore, the ladder beam main body comprises a thin beam section and a thick beam section, the thin beam section and the thick beam section are both cuboids, one end of the thin beam section and one end of the thick beam section are integrally arranged, and the other end of the thick beam section in the front ladder beam main body and the other end of the thin beam section in the back ladder beam main body in the two adjacent ladder beam main bodies are fixedly connected;

furthermore, the two-degree-of-freedom local resonance unit comprises an upper rubber column, a first mass block, a lower rubber column and a second mass block, wherein the upper rubber column, the first mass block, the lower rubber column and the second mass block are all cylinders, the upper rubber column, the first mass block, the lower rubber column and the second mass block are sequentially arranged from top to bottom, the bottom end of the upper rubber column is bonded with the top end of the first mass block, the bottom end of the first mass block is bonded with the top end of the lower rubber column, the bottom end of the lower rubber column is bonded with the top end of the second mass block, and the top end of the upper rubber column is bonded with the lower surface of the thin beam section;

further, the end face diameter value of the upper rubber column is L1, the width value of the lower surface of the thin beam section is L2, and L1 is L2;

furthermore, the center of the end face of the upper rubber column is coaxial with the center of the lower surface of the thin beam section;

furthermore, the end surface diameter values of the upper rubber column, the first mass block, the lower rubber column and the second mass block are the same;

further, the height of the upper rubber column is smaller than that of the lower rubber column;

further, the height of the second mass block is smaller than that of the first mass block;

further, the value range of M is 4-10.

Compared with the prior art, the invention has the following beneficial effects:

1. the step beam and upper rubber column bonding surface, the upper rubber column and upper mass block bonding surface, the upper mass block and lower rubber column bonding surface and the lower rubber column and lower mass block bonding surface in the device provided by the invention are stably connected, so that corresponding displacement is coordinated. The width of the lower surface of the thin beam section of the stepped beam is designed to be a flat structure with the diameter consistent with that of the cross section of the upper rubber column, so that the stepped beam and the local resonance unit are firmly and reliably bonded.

2. The invention designs a plurality of groups of stepped beam structures with different parameters, which is beneficial to researching and exploring the interaction relation between the Bragg band gap generated by the periodic arrangement of the variable cross-section beam sections and the local resonance band gap generated by the local resonance of the rubber column mass block structure. Has important theoretical and practical significance for discovering new vibration reduction and isolation technical means and ways.

3. Based on the band gap characteristic analysis result of the variable-section acoustic metamaterial beam, the variable-section design can greatly increase the width and the number of the Bragg band gaps, promote the fusion of the Bragg band gaps and the local resonance band gaps, and effectively widen the width of the local resonance band gaps, so that the bottleneck of narrow bandwidth of the local resonance band gaps is broken through, and the excellent vibration reduction and isolation effect is achieved.

4. The invention has simple structure, convenient manufacture and low cost, and saves the expenses for scientific research.

Drawings

FIG. 1 is an isometric view of the present invention;

FIG. 2 is a bottom view of the present invention;

FIG. 3 is a front view of the present invention;

FIG. 4 is a top view of the present invention;

FIG. 5 is an isometric view of a ladder beam assembly of the present invention;

FIG. 6 is a bottom view of the ladder beam assembly of the present invention;

FIG. 7 is a front view of the ladder beam assembly of the present invention;

FIG. 8 is a top view of the ladder beam assembly of the present invention;

FIG. 9 is a left side view of the ladder beam assembly of the present invention;

FIG. 10 is a graph showing the effect of broadening the band gap of the local resonance in accordance with the present invention.

In the figure, a step beam main body 1, a thin beam section 11, a thick beam section 12, a two-degree-of-freedom local resonance unit 2, an upper rubber column 21, a first mass block 22, a lower rubber column 23 and a second mass block 24 are shown.

Detailed Description