Two-dimensional wave structure analysis of SH-like guided waves in finite cross-section waveguide

Finite cross-section components are widely used in infrastructure construction, such as rail and flat steel. The traditional infinite plate theory cannot describe the wave structures in the finite cross-section waveguide. In this study, the wave structures of the SH-like guided waves are analyzed theoretically, which show that there are two-dimensional wave structures in the finite cross-section waveguide. Based on wave finite element method (WFEM) and displacement constraints, the dispersion curve for SH-like guided wave in a rectangular plate is obtained. The two-dimensional wave structures of SH-like guided waves are calculated, and the particle vibrations of different SH-like guided wave modes are analyzed. The excitation method of different modes was designed by using multiple periodic-permanent-magnet electromagnetic acoustic transducers (PPM EMATs). Four modes of SH-like guided waves are generated, and the frequency-wavenumber domain analysis of the experimental signals is carried out to verify dispersion curves of different modes. Results show that some 2DFFT results of experimental signals are offset from the dispersion curves, and some of them agree well with the dispersion curves. Further studies show that the offset of the 2DFFT results is due to the strong Lamb wave generated by the three-dimensional deformation, and the coupling of Lamb wave and SH-like guided waves forms a coupled wave with multiple vibration directions. These findings provide a basis for understanding the wave structures in finite cross-section waveguides and using SH-like guided waves to detect finite cross-section components.