Scanning magnetostrictive sensor of SH₀ guided wave for steel plate defects

A scanning magnetostrictive sensor (MsS) with optimal coil configuration and high excitation efficiency was developed. Magnetic shield was placed inside the rectangular sensing coil to suppress the cancellation effect between the dynamic magnetic fields provided by the upper and lower wire current, respectively. Therefore, the height of the sensing coil can be reduced while retaining the guided wave detection ability of the sensing coil. U-shape permanent magnetizer was employed for realizing stable magnetization of the FeCo strip so that the excitation efficiency of the sensor can be improved. Finite element simulation was used for optimizing the width and height of the yoke. Experimental tests were conducted in a defective steel plate using the proposed scanning MsS. The results show that the guided wave detection ability of the MsS with permanent magnetizer was significantly improved as compared with that was tested under the condition of remanence. The coefficient of variation of the data obtained during the scanning process is less than 9. 1%, indicating very good stability of the scanning sensor.