Magnetizing frequency dependence of magneto-acoustic emission in pipeline steel

Magnetoacoustic emission (MAE) in pipeline steel was investigated and found to increase linearly with the magnetizing frequency. The rate of increase of MAE RMS voltage with frequency was found to depend on the magnitude of the magnetic flux density. The observed MAE waveforms have been analyzed in terms of the frequency dependence of their RMS voltage and the pulse-height distribution of MAE voltage pulses. With increasing magnetizing frequency, the smaller amplitude MAE pulses are replaced by large amplitude pulses, and the total number of MAE pulses also increases. The results are discussed in light of existing models of domain wall motion and magnetoacoustic emission