Change in mode configurations and propagation velocity of guided waves through an elbow section of a pipe

Guided waves, propagating over long distances with low damping along the longitudinal direction of pipes, are expected as an efficient method for non-destructive testing of such long structures. In industrial applications, structures to be inspected often have both straight sections and curved sections. Therefore, it is important to consider appropriate conditions for transmitting guided waves propagating with less damping through multiple areas with different shapes. This research theoretically analyzes and experimentally verifies propagation of guided waves from a straight section to an elbow section of a pipe, and discusses change of the mode configurations and the propagation velocity under the influence of the elbow curvature of the pipe. The results show a good possibility of predicting the receiver signals detecting guided waves through an elbow section of a pipe, by clarifying change of the mode configurations and the propagation velocity under the influence of the elbow curvature in a semi-analytical way. The approach shown in this study will be useful for propagating guided waves efficiently in pipes with elbow sections.