Detection of Axial Cracks in a Bent Pipe Using Emat Torsional Guided Waves

The feeder pipe in the pressurized heavy water reactor (PHWR) is exposed to a possible leakage during operation. Because of the geometrical complexity of the pipe and its inaccessibility due to a high radiation environment, it is difficult to examine the defect by the conventional ultrasonic method. The guided ultrasonic inspection was chosen for the inspection of the pipe. The torsional mode has many advantages for obtaining a higher sensitivity and lower attenuation for the crack. The torsional guided waves were generated and received by an array of electromagnetic acoustic transducers (EMAT). The feasibility of detecting the axial cracks is investigated through a series of experiments with artificial notches on the bent pipe.