Experimental Investigation of Mode Conversions of the T(0,1) Mode Guided Wave Propagating in an Elbow Pipe

Mode conversions from the fundamental torsional guided wave mode, T(0,1), to the higher-order torsional modes, T(1,1), T(2,1), T(3,1), and T(4,1), at a welded elbow pipe were experimentally investigated in a wide frequency range from 30 to 80 kHz. One ring-shaped transducer system was used as the transmitter and another as the receiver. Both systems consist of eight circumferentially located piezoelectric transducer elements. A novel method for a preferential detection of the torsional modes was proposed on the basis of the circumferential wave structures of the modes, which was utilized for investigations of mode conversions. Dispersion relations of the converted modes in frequency ranges from 30 to 80 kHz were also experimentally investigated, which agreed very well with those of the theoretical calculations.