Study On Band Gap Mechanism Of Adjustable Radial Elastic Metamaterial Structure

In the industrial field of a variety of mechanical equipment in the work will inevitably make the machinery vibration,serious or even fatal failure,resulting in safety accidents,and the nature of vibration is due to the elastic wave propagation effect in the structure.Elastic metamaterial structures have the characteristics of low frequency band gap,which provides a new idea for low frequency vibration control.Based on the elastic metamaterial theory,this paper designs the adjustable radial elastic metamaterial structure,which can control the vibration and noise problems in the mechanical structure,and has important theoretical and engineering value to guide the design and application of elastic metamaterial structure.Firstly,a radial elastic metamaterial structure with adjustable blades is designed.The structure is arranged periodically in radial,circumferential and axial directions.The matrix is composed of four circular arc plates.The cladding layer is composed of a ring which is close to the base and three connecting rods similar to the blade.The scatterer is a hollow cylinder.The energy band structure and frequency response of elastic wave in this kind of structure are calculated by finite element method,and the eigenmode diagram of the upper and lower edge of the band gap is analyzed.It is found that the structure opens the low-frequency complete band gap of 72.065hz-95.466hz.Based on the local resonance mechanism,the coupling between the vibration of the scatterer and the elastic wave propagating in the matrix is the key to open the band gap.In addition,the effect of structural geometry parameters on the band gap is studied.The results show that the band gap can be moved up or down by changing the angle of the connecting rod,the number of connecting rods and the thickness of the hollow cylinder.In order to further improve the flexibility of band gap regulation,an adjustable honeycomb radial elastic metamaterial structure is designed and studied.The structure of the coating layer is arranged periodically along the circumferential and axial direction.The main body of the coating layer is honeycomb,which is closely connected with the hollow cylinder through the coating layer,and the scatterer is located in the center.It is found that the structure can open 8.5hz-11hz ultra-low frequency band gap.In order to further achieve the effect of band gap regulation,the honeycomb coating was filled with different amount and different materials,and the regulation effect of different filling methods on the band gap was studied.The results show that the edge filling mode has little effect on the band gap regulation;the internal filling mode can move the band gap up by 6.5hz-8.6hz;the herringbone filling mode can open the low-frequency broadband gap of 29hz-36hz,and the extra filling band gap of herringbone internal steel material can obtain a larger range of regulation.Therefore,different filling methods can achieve the purpose of band gap regulation.The main purpose of this paper is to open an ultra-low frequency band gap and to achieve active control of the band gap to a certain extent,so as to promote the application of radial elastic metamaterial structure in low noise mechanical structure.On the one hand,this research can promote the development of radial elastic metamaterial theory,and enrich and perfect the physical connotation of phononic crystals.On the other hand,it can promote the application of disk or cylindrical shell in aerospace,ships,vehicles and high-precision machine tools.It is expected to broaden people's technical ideas for solving vibration and noise problems,It provides a theoretical reference for other vibration and noise reduction problems.