On the long-term performance of solitary wave-based transducers for nondestructive evaluation applications

A nondestructive evaluation (NDE) technique based on highly nonlinear solitary waves (HNSWs) has been developed recently. The technique uses the propagation and detection of HNSWs along 1-D array of spherical particles in which one end is in contact with the structure to be inspected, and the particle at the opposite end induces the waves by means of a mechanical impact. Several studies have demonstrated that the dynamic interaction between the waves and the structure is dependent on the geometric and mechanical properties of the structure and such dependency can be monitored by sensing the waves reflected at the chain/structure interface. The NDE technique is typically performed using the so-called HNSW transducer, which indicates a portable device that consists of an array of particles, a device to trigger the waves, and a sensing element to detect the waves. In this study, the long-term performance of three transducers was investigated by placing them above a test object while the transducers triggered and detected thousands of waves. Any variability of the waves was quantified by extracting simple features such as amplitude, time of flight, and cross-correlation. Sixteen measurements were also captured with short videos at ~1,000 fps. The results of the study demonstrate that the traveling time of the solitary waves is the most reliable parameter. The findings of this study allow to frame a valid strategy to improve the design of the transducers in order to make the HNSW-based technique suitable for long-term monitoring.