Megahertz-range magnetostrictive sensor for exciting longitudinal guided waves in steel rods/strands

A flexible printed meander coil (FPMC)-based magnetostrictive sensor (MsS) which has a central frequency around 1.25 MHz is presented in this paper. The FPMC-based MsS can be easily wrapped onto the twisted strand surface and disassembled from the strand. It can be also installed onto the central rod of the strand after being wrapped into multiple layers. That is, this FPMC-based MsS can fit for the tested sample of different diameters. With the proposed megahertz-range FPMC-based MsS, the rods/strands inspection system is potential to be applied for practical inspections, having higher axial inspection resolution and sensitivity to small defects.