Study on Relationship between Amplitudes of Reflection Signals and Positions of Magnetostrictive Transducer

As one of key techniques for guided waves NDT based on magnetostrictive effect, the transducer is a “bridge” which plays an important role in practical inspection. In the experiments, we find that the guided wave echo-signals detected in pipes are affected by the position of the magnetostrictive transducer. First, guided waves’ generation mechanism and its propagating characteristics in pipes are theoretically analyzed. Second, several experiments are carried out to verify this theory. At last, the relationship between amplitudes of the refection signals and positions of the transducer are discussed. For a given detected steel pipe, when the transducer is installed on different position of pipe, the varieties of guided wave signals are detected and analyzed using computer. The various curves between amplitudes of the refection signals and positions of the transducer are obtained,and the “wave crest” and “wave trough” appeare periodically. In the practical inspection, the positions where the “wave crest” appeares in the curves should be selected as location of the transducer. To generate and receive the most perfect signals whose wave energy is stronger and the signal-to-noise ratio increased greatly, the positions of guided wave transducer should be optimally selected according to different type pipes. The experimental results are very well agreed with the theoretical analysis.