Wave-structure conversion and rainbow trapping effect in complex cross-sectional structures

Abstract

The straight switch rail of the turnout is an engineering structure with variable cross-sections and special-shaped cross-sections. The propagation characteristics of guided waves in it are very complicated. Even for the guided waves of a single mode, the distribution of wave amplitudes varies greatly at different cross-sections of the straight rail. Therefore, this paper innovatively proposes a wave-structure conversion algorithm for variable cross-section structures. Employing this algorithm enables us to discern the pattern of wave amplitude distribution and the evolution of dispersion characteristics as a single mode traverses a straight switch rail. This paper also established a transient finite element model of the straight switch rail. Through the comb-like excitation method based on the principle of group velocity, the propagation of a single guided wave mode in the straight switch rail was simulated, thereby verifying the correctness of the wave-structure conversion algorithm for variable cross-section structures. Meanwhile, the dispersion information of modes in different key cross-sections is obtained based on the algorithm in this paper, and the rainbow trapping effect in straight switch rails is found for the first time. Eventually, the theoretical analysis results and the rainbow trapping phenomenon in the straight switch rail were verified through experiments. The main conclusions obtained are as follows: Under the excitation of specific center frequencies, some modes will exhibit the rainbow trapping effect, which will cease to propagate forward in the healthy straight switch rail and generate a completely reflected echo.