弯曲波-纵波彩虹捕获效应及其模式转换

When broadband elastic waves propagate in a graded structure， the waves of different frequency components will stop propagating forward and have energy accumulation at different positions of the structure，which is called elastic wave rainbow trapping. Mode conversion refers to the phenomenon in which the polarization of elastic waves changes during propagation. The use of rainbow trapping to achieve mode conversion of elastic waves is an emerging research direction in the field of wave manipulation. In order to achieve bidirectional mode conversion of flexural wave and longitudinal wave through rainbow trapping，a beam with graded pillars is proposed in this paper. The band structures of the subunits are solved by adopting the transfer matrix method，and their correctness is verified by using the finite element method. According to the band structures of the subunits，the mechanism of the flexural-longitudinal wave rainbow trapping and its mode conversion is explained from the perspective of wave number change. The flexural-longitudinal wave rainbow trapping is verified by finite element frequency domain simulation. The bidirectional mode conversion of flexural wave and longitudinal wave when flexural-longitudinal wave rainbow trapping occurs is verified by finite element time domain simulation.