Research On Low Frequency Vibration And Noise Reduction Design Of Aircraft Panel Based On Acoustic Metamaterials

Vibration and noise control of aircraft panel structures has become one of the key technical problems that need to be solved in the design of modern aircraft.On the one hand,vibration of aircraft panel structures has a harmful effect on the operation of instruments.Moreover,sometimes it can even lead to fatigue failure of the panel structures,which will reduce the safety and reliability of aircraft.On the other hand,sound radiation produced by vibration of aircraft panel structures can louden noise in the cabin,influencing the comfort,and even affecting the health of occupants.Therefore,study on vibration and noise reduction design of aircraft panel structures is of great significance for improving the performance and quality of modern aircraft.Traditional vibration and noise reduction techniques of aircraft panel structures mainly include optimization design of the panel structure,attaching damping material and equipping dynamic vibration absorbers.However,due to limitation of additional mass and installation space,such traditional techniques have some disadvantages such as poor efficiency at low frequencies(below 500Hz)or narrow effective frequency band.Therefore,it is necessary to develop new technologies and methods to achieve better vibration and noise reduction performance in broadband low frequency range.In recent years,the concept of "acoustic metamaterials" has provided a new idea to solve the problem of controlling vibration and noise for engineering structures like aircraft panels.Recent studies have shown that a type of new structures designed based on "acoustic metamaterials" can generate band gap of elastic wave in low frequency range.In the band gap,the propagation of elastic wave is prohibited,leading to a significant suppression of low frequency vibration of structures.Hence this type of new structures has broad prospects in the field of vibration and noise reduction.In this paper,the idea of "acoustic metamaterials" is introduced into the design of aircraft panel structure to construct an acoustic metamaterials aircraft panel structure.In order to facilitate the control of low frequency vibration and sound radiation of aircraft panel below 500 Hz,a comprehensive study on the characteristics of band gap,vibration and sound radiation properties is conducted in this thesis.The main research work and conclusions are as follows:1.The characteristics of vibration and sound radiation of complex aircraft panel structure are systematically studied.The vibration and sound radiation model of the aircraft panel structure is established by using a vibro-acoustic finite element method,the influence of structural parameters on the vibration and sound radiation characteristics is analyzed in detail: it is found that the natural frequencies of the panel structure will change obviously with the variation of the thickness of skin,the spacing of frame-ribs and stringers,which has a significant impact on the vibration and sound radiation.2.The band gap behavior and the vibration and noise reduction performance of acoustic metamaterial bare panels(without stiffeners)are explored.It is shown that the acoustic metamaterial bare panel exhibits elastic wave band gap in low frequency range,and within the band gap the vibration and noise radiation of the panel are significantly suppressed.Furthermore,the influence of the main parameters of the structure on the band gap behavior and vibration and noise reduction characteristics is analyzed,which demonstrates that appropriate choice of the lattice constant and resonator damping is helpful to achieve wide band gap,and hence broadband vibration and noise reduction.In addition,an experimental sample is fabricated and measured to confirm that the acoustic metamaterial panel possesses low frequency band gap(below 500 Hz),and can achieve vibration and noise reduction at low frequencies.3.The vibration and noise reduction properties of acoustic metamaterial stiffened panel structures are studied in depth.It is demonstrated that the characteristic of band gap can be employed to reduce vibration and noise of stiffened panel efficiently in low frequency range.The effects of main structure and material parameters on vibration and noise reduction characteristics of acoustic metamaterial stiffened panel are systematically analyzed.Moreover,the optimization design of band gap is carried out using differential evolution algorithm,and wider low frequency band gap is obtained to achieve bandwidth broadened vibration and noise reduction at low frequencies.In summary,an acoustic metamaterial stiffened panel structure is designed based on the idea of "acoustic metamaterials",and then the band gap behavior and vibration and noise reduction performance are comprehensively studied.This work provides a new technical approach for vibration and noise control of aircraft panel structure at low frequencies.The results are also helpful for low frequency vibration and noise reduction design of other panel structures.