Generation and Detection of Guided waves in a Pipe with Defect using Rapidly Quenched Magnetostrictive Ribbons

In the present investigation, rapidly quenched ribbons prepared by melt spinning technique have been used as magnetostrictive sensor (MsS) element for generation and detection of guided waves traversing through a pipe. The materials we have used in the present study are the rapidly quenched Fe80Si8B12 and Fe40Ni40B20 which have high magnetostriction constant. The experiments have been conducted on bare Al tube after generating proper dispersion curves. The experiments have been carried out using as-spun and annealed ribbons. After optimizing the ac magnetizing field, dc bias field, frequency (from software), longitudinal guided waves were generated in tubes using magnetostrictive sensor (MsS) ribbons. Measurements were carried out to test the sensitivity of this sensor to both circumferential discontinuity (saw cut) and defect free bare aluminum tubes at 76 kHz frequency. The effect of defect size on the sensor signal was also investigated. Using the present technique, the defects were not only identified but their location in the pipe was also estimated.