The unidirectional excitation of guided waves with an increased power using multiple transducer arrays in pipelines for structural health monitoring

Ultrasonic guided waves with features can be used for non-destructive testing (NDT) and structural health monitoring (SHM) on large-scale engineering structures, such as plates, pipelines, and rails. In this paper, an array of transducers with multiple rings for excitation scheme is proposed to enhance the energy of unidirectional guided waves for defect detection on cylindrical structures. The Gaussian-windowed pulse as an incident signal is designed based on the method of elastic waves superposition. The numerical simulations in ABAQUS are modeled to generate unidirectionally a pure torsional wave mode T(0,1) at the center frequency of 35 kHz using an increased number of rings of transducers on a steel pipe. The predictive results are validated experimentally. The performance of guided wave testing is evaluated using two and three rings of transducers for inspecting a 2% cross-sectional area (CSA) defect on an 8-inch schedule 40 steel pipe. Results that show guided waves as an active-excitation method can be developing for SHM of steel pipelines. Based on the method of the unidirectional enhancement of guided wave technique excitation, there are many potential applications for developing guided wave technique in other large-scale structures for SHM.