Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Engineering Science and Mechanics


Ultrasonic Rayleigh wave is a surface wave which can be used to investigate a surface fLaw; From reflection and transmission coefficients to time of flight of waves, from resonance to spectral analysis of transmitted and reflected waves, many methods were developed to study the features of a surface defect. In these analyses and experiments, one difficulty is to understand the complicated nature of the transmitted wave train. In order to get more meaningful information of a surface discontinuity, understanding of the waves in the transmitted wave train is important;The characteristics of wedge type Rayleigh wave transducer were studied first. The interactions of Rayleigh waves with steps are important and their study was conducted. The result was used on the study of Rayleigh waves interacting with other complicated surface discontinuities. In the transmitted wave train of these interactions, the waves from mode conversions were found to play very important roles. From cut-off Rayleigh waves and the waves of mode conversions, the depths of steps and slits can be estimated correctly. A computer program was developed to recognize the waves desired and to estimate the depths of steps and slits automatically. The study of separation of waves confirmed the complexity of the transmitted waves. The influence of the position of transducer was also studied and the workable range of transducer position was found.



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Chung-Shin Ma



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246 pages