The Research Of Manipulating The Reflections Of Acoustic Waves By Employing Acoustic Metamaterials

Acoustic metamaterials is one of the most popular research issues in the past years.There are lots of new ideas and findings,which promote the development of technology.We propose several new materials and structures in this paper based on the acoustic metamaterials.We also analyze these models theoretically and the finite element numerical simulations are carried out to validate their accuracy.In the first chapter,we introduce the background of acoustic metamaterials.We also analyze the types and uses of acoustic metamaterials.Finally,the development status is briefly summarized.In the second chapter,we mainly introduce the relevant theoretical basis and the quasi-static parameters calculation method of the periodic structures of acoustic metamaterials.Late,we review the finite element calculation method to analyze the periodic structures.We take the microstructures of penta-mode materials as an example and introduce the specific operation process.In the third chapter,we study the conditions that the acoustic cloak metamaterials should satisfy when the objects to be concealed have different heights.By changing the thickness of the membrane,we succeed in changing the acoustic impedance and the acoustic reflection phase of the metamaterials.The thickness of the membrane is far smaller than the size of the metamaterials,and the acoustic impedance mainly depends on the thickness of the membrane.Finally,we validate the effectiveness of the cloak metamaterials under different incident angles.In the fourth chapter,according to the generalized Snell's law,we propose a 3D ultrathin acoustic metasurface by using membrane materials.Through designing the elements of metasurface,we use the proposed metasurface for acoustic focusing.This metasurface has a benefit of ultrathin and tunable focusing spot.Thanks to the discretization of the elements,it is easily to reconstruct a new metasurface.In the fifth chapter,we propose a method to achieve acoustic underwater cloak by using penta-mode materials.It has the advantages of operational flexibility and wide bandwidth.We adjust the geometric parameters of the unit cell of the cloak to ensure its acoustic parameters are consistent with the desired values.The simulation result confirms its effectiveness.Moreover,we construct a larger cloak area by using more unit cells in the cloak without redesigning the unit cell.This simplistic design method may have potential application value.In the sixth chapter,we summarize all the content and discuss the research directions and problems for further optimization.