Defect detection in concrete-covered pipe by using smart magnetostrictive patch transducer and demagnetizing factors

The crack in pipe riser covered by a wall is difficult to test because the concrete causes large attenuation and mode conversion. Both reasons make it difficult to analyze the signal. This work reports the design of an axially magnetized magnetostrictive patch transducer (MPT) for efficient transduction of longitudinal guided wave, which can be used to detect defects in concrete-covered pipe risers. First, the theoretical background about demagnetizing field was introduced. The influence of the demagnetizing factors on the transducer efficient was discussed. Second, there kinds of existed MPTs were compared with the proposed smart MPT. In the comparison experiments of defect detection in concreted-covered pipe risers, the developed smart MPT performed better than those three MPTs. Finally, the smart MPT was applied in a defect detection of concrete-covered pipe riser sample. The experimental results for the smart MPT showed that the smart MPT can potentially be applied in pipe’s defect detection.