UC San Diego

There are many advantages for NDE (Non-Destructive Evaluation) by using guided ultrasonic waves for structural diagnostic. Guided waves are composed of longitudinal waves and shear waves. From the data acquisition respect, guided waves provide higher ranges compared to bulk wave testing. However, many challenges appear when guided waves are used for detecting, such as many modes corresponding to one frequency, and dispersion properties on the group velocity and phase velocity.

This thesis simulates guided-wave propagation by using the SAFE (Semi-Analytical Finite Element) method. From this method, only the cross section needs to be discretized. The wave propagation direction is approximated by analytical harmonic solutions. By building many large complex stiffness matrices, material viscoelastic property is considered. The solutions, such as group velocity dispersion curves (without material attenuation), phase velocity dispersion curves, energy velocity dispersion curves (with material attenuation), are generated from the SAFE codes. Moreover, SAFE codes can simulate forced solutions more efficiently than full discretization methods of traditional finite element analysis.

Two applications of guided wave propagation are shown on this thesis, multilayered anisotropic composites and railroad tracks.