Excitation and reception of single torsional wave T (0,1) mode in pipes using face-shear d24 piezoelectric ring array

Excitation of single fundamental torsional wave T (0, 1) mode is of practical importance in inspecting or monitoring the structural integrity of pipelines, as T (0, 1) wave is the only non-dispersive mode in pipe-like structures. This work presents a piezoelectric ring array to excite and receive single T (0, 1) mode which is made up of a series of equally-spaced face-shear d24 PZT elements around the pipe. Firstly, we proposed that single T (0, 1) mode can be excited by the piezoelectric ring, when the number of d24 PZT elements is slightly greater than n , where F ( n , 2) is the highest circumferential order flexural torsional mode within the frequency bandwidth of the drive signal. Then this proposed principle was confirmed by finite element simulations. Later, experimental testing was conducted on a 100 mm outer diameter, 3 mm thick aluminum pipe. Results show that the ring of 24 face-shear d24 PZT elements can suppress all the non-axisymmetric flexural modes at the excitation frequency of 150 kHz so that single T (0, 1) mode is generated. Moreover, such a piezoelectric ring transducer can also filter flexural modes and receive the T (0, 1) mode only at 150 kHz. Note that here the highest circumferential order flexural torsional mode within the frequency bandwidth is F (20, 2), so the experimental results are in good agreement with the proposed principle. The presented ring of face-shear d24 PZT elements is very suitable for severing as the T (0, 1) wave transducer in structural health monitoring system, as it is cost-effective and no external load is required for operation. (paper)