Identification of crack size and orientation in continuous cylindrical structure using macro-fiber composite

The geometric properties of cylindrical structures are complex as compared with plate-like structures. Structural health monitoring of such structures is thus more complicated. Even though many efforts have been carried out on the detection of cracks in cylindrical structures, the crack sizes and orientations have not received enough attention. Recently, a method to correlate the root-mean-square deviation change of torsional wave pack of signal with axial crack growth has been developed. In this article, based on the same principle and experimental setup, the detection of crack size and orientation is studied. Macro-fiber composite transducers are used as either an actuator or a sensor. First, a crack of finite size is induced in a laboratory specimen. Later, the size is gradually increased along various orientations. The effects of the crack size and transmitted waves, captured by the sensor, are correlated with the root-mean-square deviation values of the torsional wave packs and the longitudinal wave packs. The results show that both size and orientation of the crack can be evaluated based on the proposed method. The system developed in this article is easy to setup, cost-effective, and able to achieve automatic continuous online monitoring with good results.