Comparison of an array of EMATs technique and a magnetostrictive sensor technique for a guided wave inspection of a pipe

The leakage of a pipe in nuclear power plants is a significant concern from the point of view of nuclear safety. Because of the geometrical complexity of a pipe and an inaccessibility due to a high radiation, it is difficult to inspect it by the conventional ultrasonic methods. The guided ultrasonic method can be useful for the inspection of a pipe in those harsh environments. Based on the analysis of the dispersion curves for a pipe, a torsional vibration mode, T(0,1) was selected for the detection of cracks. The T(0,1) mode has many advantages, such as a higher sensitivity for a crack from the viewpoint of its non-dispersion characteristics and its wave structure. The torsional mode can be generated by using either an array of electromagnetic acoustic transducers (EMATs) technique or a magnetostrictive sensor technique. The detectability of the cracks was estimated through a series of experiments with artificial notches on a pipe.