Research On The Characteristics Of Vibration Propagation In Periodic Structures

Periodic structures exist in many engineering fields. Its vibration controlling is still a very important problem for a long time. The band gaps can exist in the special designed periodic structures. Within the gaps, the propagation of vibration is forbidden. And the vibration only propagates along the certain directions and regions for certain frequencies during pass bands in two-dimensional periodic structures. The two characteristics of vibration propagation in periodic structures will provide a new way to control the vibration in engineering field.With the calculation methods, together with finite element method and experimental tests, the characteristics of flexural vibration propagation in periodic beams and grids, which are applied widely in engineering, are investigated deeply and systemically. The main work and achievements are as follows:1. The finite element method and Bloch theorem are integrated to calculate the characteristics of vibration propagation in periodic beams and grids. And more, the spectral finite element method is introduced to improve the calculation convergence. These numerical methods provide the powerful tools to investigate the characteristics of vibration propagation in periodic structures.2. The flexural vibration gaps in periodic beams and grids are studied deeply and systemically. The flexural vibration gaps can exist in periodic beams and two-dimensional periodic grids. Also, the effect of structure parameters on the gaps are investigated and summarized.3. The directional propagation characteristics of flexural vibration in two dimensional periodic grids are studied. The directions and regions of wave's propagation in this grid structure for certain frequencies during pass bands are predicted with the iso-frequency contour lines of the phase constant surface.4. The experiment samples are designed and manufactured. Also the experiment test systems for investigating the characteristics of vibration propagation in periodic structures are established. For the first time, the directional characteristics are found in the experiment result. The experiment results are good agreement with the theoretical results.In summary, the characteristics of vibration propagation in periodic structures are studied theoretically and experimentally in this thesis. The research results in this dissertation are meaningful in the theory of the periodic structure as well as its application to vibration/noise control.