Research On Semi-analytical Finite Element Analysis Of Ultrasonic Guided Wave Propagation Characteristics

Semi-analytical finite element method (SAFE) is a method used to obtain the dispersion curves of guided wave propagating in the structures with complex cross-sections. According to SAFE method, guided wave is propagating along the waveguide in the form of simple harmonic wave so that we only need to do the finite element discretization on the waveguide section, saving much time and computing space. Since the SAFE method is applicable to the waveguide medium with complex cross-sectional shape, it is being used more and more widely. Research on the propagation characteristics of the guided wave using the SAFE method is a good guide for the design of transducers and the actual monitoring of rail broken.In this paper, the research situation at home and abroad is overviewed, following by the comparison between finite element method and semi-analytical finite element method. Firstly, the basic knowledge of guided waves is introduced. The principle of SAFE method is described, taking the isotropic freedom aluminum plate as an example. The phase velocity and the group velocity dispersion curves of Lamb wave in aluminum plate are calculated. The signal extraction and processing is performed using the2-D Fourier transform in order to do the modal analysis. Comparing the theoretical and experimental results, it is confirmed that the SAFE method is valid in the analysis of propagation characteristics of guided wave. Secondly, Lamb wave is used to detect grooves and holes of different sizes in a TC4titanium plates. The optimal test mode obtained by SAFE method is excited using a variable angle probe. The size and location of the defects can be determined according to the echo wave showed on the oscilloscope. Finally, the SAFE method is applied to the analysis of the guide wave in rail. Using a1.5m long50kg/m rail as the study object, the rail’s equivalent damped loss factor is measured and the attenuation curve is plotted using a sandwich transducer and a352C33low frequency acceleration sensor as the excitation and receiving units respectively. I hope this work can serve as a ready reference for everyone in the follow-up research.