Research On The Band Gap Mechanism And The Applicaion Of Periodic Structure Based On Phononic Crystals

Phononic crystals are the periodic elastic materials or structures. As the low-peak of wide frequency band gaps in phononic crystals is higher, it is difficult to be used in the control of vibration and noise. In this dissertation, the band gaps mechanism, especially low frequency band gaps mechanism of periodic structures was studied and the key factor that influences the low frequency band gaps mechanism is found and proved. The problems restricting the application of it in low-frequency vibration/noise are solved. The research results are meaningful for the application in the control of vibration/noise and will offer us new ways inside vehicle vibration and sound control.The major innovations of this dissertation are as follows:A manual weave one-dimensional two-component phononic crystal was studied. Through establishing the manual weave phononic crystals'dynamics model, the elastic wave band gaps was calculated and concerned with the phononic crystal material characteristic. The study is available for low & high frequency noise and vibration control.The vibration model of periodic multiplayer structure is established and the phononic band gaps was calculated. By choosing the proper materials, the low frequency phononic band gaps can be gained. The results provide theory base for applications in control of noise and vibration. And then by analyzing the periodic mass-spring structure model, the elastic wave band gaps of periodic multiplayer structure can be estimated and the wave band gap of periodic multiplayer structure was validated by the experiment and application in vibration and noise control inside automobile was opened up.By analyzing the vibration model of two-dimensional (2D), the elastic wave band gaps of 2D was calculated. The mechanism of band gaps was gained and then the results provide theory base for weaving 2D phononic crystals being used noise and vibration control.Finally numerical calculation method was applied to calculate the frequency response of finite periodic structure, and two results match well. The conclusions are well validated by the experiment.The finite periodic structure of three-dimensional is very complex. The finite difference time domain method was appied to calculate the the frequency response of 3D finite periodic structure and then the frequency responses of difference structures and difference materials were gained. The results were validate by experiment.In order to solve the applications of the periodic structure, transfer channels of vehicle body must be measured. The vehicle body is complex structure. Complex structure is composed of multiple materials and its shape is also irregular. It is very difficult to gain complex structure transfer function and inner sound field. In order to measure complex structure transfer function and calculate inner sound field, transfer function of integration is mentioned. By establishing virtual system, transfer function of integration can be measured and the inner sound field can also be calculated. In the experiment, automobile body transfer function of integration is measured and experimental method of establishing virtual system is very valid.Finally, the wave band gap of periodic multiplayer structure was validated by the experiment and application in vibration and noise control inside automobile was opened up.