一种基于电磁-声复合检测方法的分时策略研究

Electromagnetic acoustic transducer (EMAT) can be used as a kind of nondestructive testing method for on-line monitoring of pipeline defects. Due to circuit oscillations and other reasons, EMAT exists blind area. The pulsed eddy current testing and electromagnetic acoustic transducer (PECT-EMAT) hybrid testing methods enable electromagnetic ultrasonic monitoring, which use the pulsed eddy currents generated during the detection process to inspect defects on and near the surface of the pipeline. Recently, most research shows that the excitation strategy of the hybrid testing method is single frequency, which makes the detection range of pulsed eddy current testing limited. In order to reduce the blind area of the composite methods, a time-sharing excitation strategy with different frequencies is put forward. Firstly, a time-sharing detection system was established. Through controlling the RF switch and the excitation frequency, EMAT is excited by a signal of high frequency and PECT is excited by a signal of low frequency. Then, the detection capabilities of EMAT and PECT at different excitation frequencies are compared by simulations and experiments. The results both show that the time-sharing strategy can not only improve the signal-noise ratio of EMAT, but also improve the detection range of PECT.