Research Andapplication Of Periodic Plate Structure Based On Phononic Crystals

Plates and shells are used widely in field of aviation, mechanical equipments, vehicles and domestic appliances, for advantage of its mechanical property. Its vibration attenuation and noise reduction is always a subject which is analyzed in mechanical vibration. With rapid expansion of automobile industry, the production and sale of automobile in china reach to 18 millions in 2010, become to the number one of automobile production and sale in the world. Meanwhile, people ask for higher and higher with ride comfort of vehicle, automobile noise and vibration become one problem which needs to start with immediately. Studies have shown that the noise and vibration interior car are concentrate in low and medium frequencies, the vibration and second vibration of car body are one main noise source. For the passive anti-vibration and noise reduction, people usually use bulk damping structure to deal its high frequency of noise and vibration, but it inefficacy in low and medium frequency. So, a method which is effective, convenient and fast and low cost is searching for now, and it is also a key point which is analyzed in field of plates and shells vibration.Based on Phononic Crystals theory, plates and shells with periodic structure are applied to deal with noise and vibration in this thesis.The theoretical model of periodic plate structure is built firstly, equations according to the structure continuity conditions and relevant boundary conditions are established. At the same time, Bloch theorem is introduced for the structures of periodic. Then, solve of the equations is converted to matrix eigenvalues and eigenvector solving. The eigenvalues are the function of frequency which is depends on the parameter of periodic structure, visualization it, the bandgaps frequency characteristics of periodic structure can got.Bandgaps frequency characteristics of periodic plate structures are investigated by FEM secondly. Finite element model of periodic plate structure is established, and dynamic simulation is taken, thus, the bandgaps of periodic structures is obtained, and verified it with theoretical calculation.Then, practical model is established, bandgaps of periodic structure is gotten by experiment, verified the bandgaps which is gotten with theoretical calculation and FEM, affirms existence of bandgaps in low and medium frequency.Finally, the periodic plate structure is applied in vehicle NVH, compare the interior noise speed tracking, the sound acoustic pressure level is attenuated 3dB average, the sound and vibration energy interior car is attenuated strongly.