Enhancement of unidirectional excitation of guided torsional T(0,1) mode by linear superposition of multiple rings of transducers

The higher performance of the guided wave technique for non-destructive testing (NDT) and structural health monitoring (SHM) on large-scale engineering structures is still a requirement in industries. In this paper, the unidirectional excitation function of guided waves by adding many rings of transducers (even or odd number) is described to enhance the wave power output of the inspection system. A parametric analysis based on the wave superposition is developed to predict the maximum power output amplitudes depending on varied ring spacings between the transducer arrays in the different centre frequencies. The proposed approach is tested numerically and then validated through an experiment in which torsional wave mode T(0,1) is excited in a pipe by one, two and three rings of 24 transducers operating in time-delays and different amplitude factors. The performance of transducer arrays for increasing the power output of excitation in the forward direction and cancelling signals in the reserve direction has been evaluated using experimental measurements.