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Baseline-Free Crack Detection in Nuclear Power Plants



This paper presents a new methodology that allows instantaneous detection of structural defects in pipeline structures without using prior baseline data. The proposed technique is based on the fact that the multiple identical guided wave paths can exist in the cylindrical structures due to the axisymmetric geometry. This study instantaneously detected structural defects in the cylindrical specimen from the differences of multiple guided wave signals, which show axisymmetric geometry. For guided wave generation, four transducers were attached along the circumference of the cylinder with equal spacing at a certain axial location. For guided wave sensing, another four transducers were attached in the same way at the difference axial location. Each pair of transducer is used for guided wave generation and sensing in a pitch-andcatch manner. Since the wave propagation paths with different axisymmetric geometry have the different pitch-and-catch distance, all of measured signals can be grouped accordingly. When the test specimen is intact, all signals in each group will have almost similar waveforms. However, if any structural defect exists along the wave propagation path, the multiple response signals with the same pitch-and-catch distance show some discrepancy. Since the proposed technique does not require baseline signals in the whole process, it has been demonstrated that robust damage detection can be achieved even under varying temperature conditions.

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