Detection of Shear Horizontal Guided Waves Propagating in Aluminum Plate with Thinning Region

元データ 2011-07-25 著者(集計中)


We propose a new method for wall-thinning inspection based on mode conversion of shear horizontal (SH) guided waves, which is represented as group velocity change. Group velocities of higher modes of SH guided wave propagating in a plate-like wave guide depend on the thickness and frequency due to dispersive characteristic. There exists a cut-off thickness for each higher mode, below which the associated mode cannot propagate and mode conversion to lower ones is expected, leading to discontinuous velocity change. Here, the fundamental SH<sub>0</sub> and first asymmetric SH<sub>1</sub> modes are generated by the periodic-permanent-magnet electromagnetic acoustic transducer (PPM-EMAT) and propagated in aluminum plates containing thinning regions. A broad-range piezoelectric pinducer is used to detect the propagating wave in order to explore the mode conversions phenomena. We directly observed that the generated SH<sub>1</sub> mode converts to SH<sub>0</sub> mode in thinning region and converts back to SH<sub>1</sub> mode when the thickness returns to original.