Design And Analysis Of Low-frequency Programmable Sound-absorbing Structure Based On Paper-cutting Ide

With the progress of science and technology,transportation is becoming more and more developed,which is accompanied by the noise pollution caused by transportation.For example,the noise generated by the high-speed operation of the engine is transmitted to the cabin through the air and the fuselage structure itself,which can cause harm to passengers.Therefore,it is essential to study acoustic structure to achieve noise reduction.In recent years,acoustic metamaterials have attracted much attention,Acoustic metamaterials are artificially designed periodic/aperiodic geometric structures composed of two or more materials,When the size of structural unit cells is smaller than the wave length,the physical characteristics that traditional acoustic structures do not have are realized,such as negative equivalent elastic modulus,negative Poisson’s ratio,negative equivalent mass density,etc,which has been widely used in aerospace,construction,industrial manufacturing and other fields.Although acoustic metamaterials show the advantages of superconventional acoustic properties,but there are some problems such as narrow sound absorption band,difficult absorption of low-frequency,simple sound absorption frequency,complex structure,and difficult design.In order to solve these problems,based on the principle of Helmholtz resonator,this paper designs a programmable kirigami-based lightweight sound absorption structure(KLSAS),it has the characteristics of low-frequency broadband sound absorption in sub-wavelength scale.The sound absorption structure is composed of kirigami structure and cavity.Kirigami structure has the advantages of lightweight,programmable and easy to control,which greatly increases the design freedom of KLSAS,and can meet the requirements of sound absorption performance in different environments.The main research methods,results and innovations of this paper are as follows:(1)This paper designs a KLSAS.The two-dimensional clipping plane structure of kirigami unit is composed of two short slits and one long slit,and the deformation mode of kirigami structure is analyzed.the explicit relationship between the tensile strain and the maximum slit width b after the deformation of kirigami structure is established.Further,the kirigami structure samples were prepared by cutting PVC transparent plate and laser cutting aluminum plate.And the mechanical properties of the relevant materials were obtained by standard tensile test,so that the material properties of the structure could be accurately characterized in the subsequent finite element model.Then,the pre-stretched kirigami structure is bonded with the cavity to obtain the KLSAS.Finally,metallographic microscope was used to measure the maximum slit width b of the stretched kirigami structure.(2)The sound absorption characteristics of KLSAS are studied.Firstly,based on the sound absorption theory of micro-slit,the sound absorption theoretical model of KLSAS is established by equivalent volume method;The numerical simulation model is established by Comsol software.Finally,acoustic impedance tube is used to test the sound absorption characteristics of KLSAS.And compare the three results.The study found: a)The finite element model and theoretical model of KLSAS can better predict the corresponding sound absorption coefficient at different frequencies;b)From the theoretical results,the sound absorption coefficient of single-layer KLSAS is greater than 0.8 in the 603-1283 Hz frequency band,reaching 1.09 times frequency range,and the structural wavelength ratio is1/11.3,which has good comprehensive sound absorption performance.c)From the normalized acoustic impedance and the results of particle vibration velocity and thermal viscosity loss in the simulation results,the sound absorption mechanism of KLSAS is revealed.The higher the sound absorption coefficient,the greater the vibration velocity and thermal viscosity loss,and the sound absorption coefficient is affected by the coupling effect of normalized acoustic resistance and normalized acoustic reactance.(3)The influence of key parameters on the sound absorption performance of kirigami is analyzed.Based on the theoretical model of KLSAS,By using the influence rule of changing design parameters on effective sound absorption frequency band,the KLSAS has good programmable characteristics.It is found that the influence of tensile ratio,basic element size,thickness and cavity depth on sound absorption coefficient is much greater than that of hinge.In order to further improve the sound absorption characteristics of KLSAS,structural optimization method is used to optimize its parameters.With the frequency band width of sound absorption coefficient greater than 0.85 as the optimization objective and the variation range of structural parameters as the constraint,an optimization design model was established and solved by genetic algorithm.The optimized KLSAS can achieve the sound absorption coefficient of more than 0.85 in the frequency band 277-1609 Hz,and the structural wavelength ratio is 1/8.8,realizing the low-frequency,broadband and sub-wavelength scale efficient sound absorption.The KLSAS studied in this paper has good programmable characteristics.Through the reconstruction design of single cell and changing the prestretch,it can meet the sound absorption of different noise bands and achieve the broadband sound absorption effect of lowand middle-frequency,which provides a new idea for the design of low-frequency noise reduction acoustic structure with programmable characteristics.It has a good application prospect in aerospace field,high speed train and other fields which have strict requirements on structural lightweight.