Research On Vibration And Sound Propagation In Lightweight Lattice Structure

Porous and periodic lattice structures have the superior performance oflightweight, sound isolation and vibration isolation. These structures can beextensively applied in aerospace, high-speed trains, cars, ships and submarines andarouse great enthusiasm of researchers. So far, the research on the sound isolationand vibration isolation problems in lattice structures is mainly about relativelysimple two-dimensional lattice sandwich structures. However, these studies are stillrare, such as the establishment of the vibration and sound isolation theoretical modelof three-dimensional lattice structures, the analysis of vibration and soundpropagation characteristics and the optimal design, the multi-component phononiccrystal structures integrated to the lattice sandwich structures, the control of thestructural vibration by using vibration frequency stop band characteristics ofphononic crystal structures and the influence of the defects on them considered. Sothe vibration and sound propagation of lightweight lattice structure is studied in thiscontext.The vibration equations and vibro-acoustic coupling control equations ofsimply supported tetrahedral lattice truss sandwich plates are established by usingReissner sandwich plate theory. These control equations are solved by the boundaryconditions, the test functions and Fourier transform. The results of theoretical andnumerical solutions of the structural natural frequency and sound transmission lossmatch well in a certain frequency range, and then the reason that sound transmissionloss are suddenly reduced to form a sound trough is analyzed.Based on the above, the effects of different sandwich height, rod radius, platethickness, length, width and material of sandwich plate and the angle of sonicincidence on the vibration and sound isolation characteristics are studied. Thecomprehensive performance evaluation index are created, and then good overallperformance sandwich plate is obtained through the optimization of the vibrationand sound isolation characteristics and compared with the two-dimensionalhoneycomb sandwich plate afterwards.The finite element method is used to research the influence on the longitudinaland bending vibration propagation of two-dimensional three-component grid andthin plate caused by damping and excitation position, and then the vibrationpropagation of square lattice honeycomb sandwich plate which is composed of thesetwo kinds of structures is analyzed. It is found that the vibration of sandwich plate iswell suppressed in the frequency stop band.The vibration propagation of defective square lattice honeycomb sandwich plate is further considered and then the vibration propagation of this one and the onewithout defects are comparatively analyzed. It is shown that the position of vibrationfrequency stop band and the area of vibration suppression are changed by thesandwich defects. Finally the vibration propagation of more complex defectivelattice structures are deeply studied through the Sierpinski carpet structures.The results of this paper are meaningful reference value in the design of soundisolation and vibration isolation of lightweight lattice structures.