회절초음파를 이용한 노치 피로균열의 균열깊이 평가

초록

This paper proposed a methodology based on ultrasonic diffraction technique to inspect the depth of a crack initiated from a notch of CT specimen by fatigue test, and its usefulness was verified by experiments. Especially, in order to identify accurately the diffractive waves from the crack tip in the situation where there are extra diffractive elements such as a notch, we have tried imaging by transducer scan and analyzed the propagation path of diffracted wave. Two specimens with and without a crack were experimented. Higher frequency and larger refractive angle of transducer showed a tendency to decrease the error in the measurements, and the measured crack depth showed an error less than 0.38 mm in case of 4 MHz 60°-60°. The proposed methodology is applicable to weak diffractive sources, and so that it would be useful to inspect micro cracks and for their depth sizing.

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