| Summary: | 碩士 === 長庚大學 === 機械工程研究所 === 89 === The research is focused on the dispersion behavior of acoustic wedge waves propagating along the tip of ring-type wedges with a laser ultrasound technique and finite element analysis. The measurements results indicate that the dispersion relation of the fundamental antisymmetric flexural（ASF）mode has a negative slope in the phase velocity-frequency dispersion space for a nearly truncation-free ring-type wedge. It is also observed that, at the low-frequency, or long-wavelength limit, the fundamental ASF mode of the ring-type wedge has a phase velocity higher than that a straight wedge due to the curvature effect. And FEM result support this discover. However, at the high-frequency, or short wavelength limit, the fundamental ASF mode of the ring-type wedges become insensitive to the curvature effect and dominated by the truncation effect.
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