Research On Asymmetric Phenomena Of Elastic Wave In Piezoelectric Metamaterial

The asymmetric transmission mechanism of elastic wave is very important for enhanced sensing,amplification and asymmetric control of elastic waves,and is expected to provide a new solution for the design of new sensors.Meanwhile,metamaterials are a good medium for studying the asymmetric transmission of elastic waves because of their incomparable properties compared to natural materials.Based on piezoelectric metamaterials,the asymmetric propagation of longitudinal wave and flexure wave is studied in this paper.The research content consists of three parts: asymmetric scattering of curved wave,non-reciprocity attenuation of p-wave on beam and curved wave on L-shaped beam respectively.It includes:(1)Asymmetric scattering of flexural wave is realized by Parity-Time(PT)symmetric system.The concept of PT symmetric system is derived from quantum mechanics.In the first part,a PT symmetric beam is designed for flexural wave.Firstly,the PT symmetry condition is derived,then based on the effective medium method and finite element method,it is verified that the effective parameters of the gain and loss unit meet the PT symmetry condition,and the tunability of the exceptional points is studied by changing the resonant frequency.Finally,the scattering characteristics of PT symmetric beam are analyzed by transfer matrix method and finite element method.(2)In the second part,the non-reciprocity attenuation of longitudinal wave on beam is studied by employing unidirectional circuit.Firstly,the transfer matrix of the unit is derived,and then the dispersion curve of the unit is calculated by combining Bloch theorem.Finally,the non-reciprocity attenuation of longitudinal wave is intuitively illustrated by numerical simulation.(3)In the third part,the unidirectional circuit mentioned above is employed again to study the non-reciprocal attenuation of flexural wave on L-shaped beam.The research steps are the same to the second part,and the influence of negative capacitance and resistance on the non-reciprocal attenuation is discussed.In general,the three kinds of asymmetric transmission phenomena studied here have certain theoretical significance for the study of the asymmetric t ransmission mechanism of elastic waves.