Health monitoring of axially-cracked pipes by using helically propagating shear-horizontal waves

This paper presents a possibility of structural health monitoring of axially-cracked pipes by using helically propagating shear-horizontal waves. The present approach is motivated by the facts that circumferentially- or helically-incident waves can detect an axial crack in a pipe more sensitively than longitudinally-incident waves and that guided waves are more advantageous for long-range inspection. For effective detection of axial cracks, a shear-horizontal guided wave magnetostrictive transducer that has wide beam directivity but can focus more power along the circumferential direction than the longitudinal direction is designed. Upon inputting a single Gabor pulse to the transmitting transducer, the receiver catches a series of pulses due to its unique directivity pattern. Damage estimation is achieved by comparing the signals measured in cracked pipes and those in an un-cracked pipe.

► The use of helically-propagating SH waves was investigated for effective detection of axial cracks in a pipe.
► A magnetostrictive patch transducer was developed to generate and measure helically-propagating SH waves.
► The phenomenon of the appearance of multiple echo-like pulses in the measured signal was investigated and explained.
► The proposed method produced results sensitive to the length and depth of an axial crack in a pipe.