TWO EFFICIENT METHODS OF MODE SELECTION IN A WAVE GUIDE INSONIFIED BY A TRANSDUCER MOUNTED ON ITS SECTION

Guided waves are multimodal and dispersive: relating a time‐of‐flight to a distance is difficult. To solve this one can –i) use narrow bandwidth excitation so that only few modes can propagate –ii) in that bandwidth, impose a source to favor one mode. For sources acting from the guiding surface, methods of mode selection exist. Here, two methods are described for sources acting from the section. For various geometries, frequencies where tangential stress vanishes or is negligible are exhibited. By mimicking the normal stress in the section using a multiple‐element transducer, one generates solely the mode chosen. Examples show the effectiveness of these approaches.