Structure Design And Low Frequency Vibration And Noise Control Of New Phononic Crystals

Artificial acoustic structures have been widely studied by scholars at home and abroad due to their excellent acoustic control characteristics and mechanical properties.As a kind of artificial acoustic structures,phononic crystals can inhibit the free propagation of elastic waves in the band gap frequency range.Low-frequency vibration and noise control has always been a difficult problem to be solved in the engineering field.Traditional vibration and noise control methods,such as additional acoustic baffles,porous sound-absorbing materials,are only applicable to medium-high frequency vibration and noise control.The research on vibration and noise control using the low frequency band gap of phononic crystals has broad prospects.Therefore,it is of great theoretical significance and engineering practical value to carry out low frequency band structure design,band gap characteristic analysis and vibration and noise control research on phononic crystals.Based on the local resonance mechanism and the Bragg scattering mechanism,the structure design and vibration and noise control of the new two-dimensional phononic crystal are studied in this thesis.It mainly includes the following four aspects: the mechanism of the band gap of the double side hollow scatterer phononic crystals,the influence of the structural design of the cladding layer on the low-frequency band gap of the lightweight phononic crystals,the calculation of the sound insulation and vibration reduction capacity of the new phononic crystal array plate and the analysis of the influencing factors,and the test of the vibration and noise of the phononic crystals applied to the automobile air-conditioning compressor.The specific research works are as follows:(1)Based on the local resonance mechanism and Bragg scattering mechanism,a two-sided hollow scatterer phononic crystal model is established,the generation mechanism of each band gap is analyzed,the transmission loss curve of the phononic crystal array is calculated,and the rationality of the first complete band gap range is verified.The effects of the height of the scatterer,the notch angle of the cladding and the width of the connecting short plate on the local resonance band gap and Bragg band gap of the new phononic crystal are studied.(2)Establish phononic crystal models with different number and distribution of claddings.The first complete band gap of the new type of light-weight phononic crystal is studied by establishing the phononic crystal models of different connection forms between the claddings and the scatterers.And study the influence of the damping of the claddings on the transmission loss of phononic crystals.The equivalent spring mass system model is established,and the accuracy of the energy band calculation is verified by the analytical method.(3)The acoustic-structure finite element calculation model of the new type of phononic crystal array plate is established,and the acoustic response and structural vibration response of the new type of phononic crystal array plate and the ordinary steel plate under the same background pressure field acoustic pressure excitation are compared,and verified with the semi analytical method.The influence of the number of missing cells in the array and the scattering material on the sound insulation and vibration reduction of the phononic crystal array plate is analyzed.(4)Based on the above phononic crystal model and theoretical method,the phononic crystal model applied to automobile air conditioning compressor is formed considering the actual application scenario and production cost and other factors,the band gap range of the phononic crystal is calculated,and the arrangement position and form of the phononic crystal in the housing of the automobile air conditioning compressor are studied.Each component material is customized to assemble the actual phononic crystal,and the compressor vibration and noise bench test and vehicle test are carried out to analyze the control effect of phononic crystal on low-frequency vibration and noise in practical engineering applications.