Reflection of the s0 Lamb mode from a flat bottom circular hole

A study of the interaction of the so Lamb wave with a flat bottom circular hole in a plate is presented. The majority of the study was performed using a three-dimensional finite element model, representing an area of the plate with a circular flat-bottom hole (33% or 50% of the plate thickness deep). In the first part of the work, the incident so wave was specified to be a plane wave. The specular reflection was predicted and showed the importance of several factors: the interference phenomena between reflections from the leading and trailing edges of the hole and secondary reflections, and the decay in amplitude of the reflected wave. Some results of this case are also compared with analytical solutions based on modal superposition. In the second part of the work, the Lamb wave mode is excited by a small circular source. The specular reflection is predicted and compared with experimental results. An assessment is made of the significance of the path lengths, wavelengths, and defect sizes on the reflection characteristics. Good agreement is found between all techniques. (c) 2005 Acoustical Society of America.