Research On Periodic Structures' Energy Dissipation Mechanism And Practical Application

With the periodic arrangements of materials or geometric parameters,periodic structures enjoy the so-called bandgap effect.Within the frequencies of bandgap,acoustic wave or vibration wave transmitting in periodic structures can be effectively inhibited,thereby endowing periodic structures with a great application prospect in control of vibtaion and noise.This research focuses on the dissipation of vibration and noise energy within periodic structures,including bandgap's formation mechanism,factors affecting properties of bandgaps,energy dissipation mechanism beyond bandgaps and structure vibration characteristics.Based on the study of energy dissipation,periodic vibration reduction models are designed,and experiments are further carried out to validate the designed structures' effects on vibration reduction.(1)Single cell models of periodic structure are established,with which the band structure is computed and its accuracy is verified by analyzing vibration response properties of periodic structures.After that,based on calculated band structures,the influences of factors such as lattice constant,filling factor,materials of matrix and inclusion on energy dissipation are researched.(2)In order to solve the typical problems existing in periodic structures like limited strength and stress concentration at the boundaries of different materials,one-dimensional periodic sandwich structures are designed,where the restraint layer is homogeneous Aluminum plate and the core is epoxy and silicon rubber.The vibration characteristics of designed periodic sandwich structures on various boundary conditions are researched with vibration testing experiments,and the accuracy of one-dimensional periodic structure bandgap computation is validated as well.(3)Taking a typical ship centrifugal pump and the vibration source and the frequency containing its excitation peak values are confirmed by analyzing the sear vibration characteristics.The two-dimensional periodic structure is designed according to the obtained frequency ranges so as to control the seat vibration.The designed periodic structure is plugged into the base plate of cabin where the centrifugal pump set up.According to the results gained from harmonic response analysis and noise radiation computation,the application of two-dimensional periodic structure effectively controls the virabtion response of cabin,and makes its noise radiation power level decline by 1.88 dB.(4)Regarding the air/steel two-dimensional periodic structure,the advanced FE method computing bandgaps is proposed,which can solve the convergence problem due to the significant difference material attributes of two-phase periodic structure;the wave inhibition range beyond bandgaps,namely deaf band,is observed by researching the energy dissipation within and beyond bandgaps with the finite periodic structure's sound level.Besides,the influences of materials,filling factor and geometry of the inclusion on deaf band are explored,followed by the experiments verifying the analytical results of band gap characteristics.