兆赫兹纵向模态磁致伸缩传感器的设计及其在钢绞线中的试验研究

Megahertz-range Longitudinal Guided Waves Transduction and Experiments in Steel Strands Using Magnetostrictive Sensor

传统的磁致伸缩传感器采用套筒式螺线管线圈,线圈的绕制非常耗时,且需要通过7芯钢绞线自由端进行安装,难以适用于实际工程检测。当中心频率达到兆赫兹时,磁致伸缩传感器具有更高的缺陷检测灵敏度,但套筒式螺线管线圈难以用于兆赫兹磁致伸缩传感器的设计。在分析多段式线圈工作原理的基础上,设计出具有优化结构参数的柔性印刷线圈。该柔性印刷线圈采用蛇形布线形式,具有36段线圈,基于信号叠加原理可提高传感器激励和接收的超声导波能量,并可卷曲贴覆在钢绞线的螺旋表面,使得磁致伸缩传感器具有拆装便捷的特点,适合实际工程检测。将该柔性印刷线圈式磁致伸缩传感器用于7芯钢绞线的试验研究。测试结果表明,传感器的中心频率为1.20 MHz时,激励的超声导波以L(0,1)和L(0,3)模态为主。这为设计7芯钢绞线检测用兆赫兹纵向模态磁致伸缩传感器奠定了基础。

The conventional magnetostrictive sensor（MsS） employs a hard sensing coil which is made by winding electrical wires onto a plastic bobbin.The conventional MsS is hard to apply for practical inspections due to the wire winding is very time-consuming and it must be installed to the seven-wire steel strand via free ends.Meanwhile,a hard coil-based MsS is difficult to have a central frequency in megahertz-range with a higher accuracy in defects detection.An innovative flexible printed meander coil（FPMC）-based MsS is presented for exciting megahertz-range longitudinal guided waves in seven-wire steel strands.The FPMC employs optimal structural parameters after analyzing the work principle of the multi-group coils configuration,and it has 36 groups of coils which can increase the excited and received guided waves energy based on superposition principle.It can be wrapped onto the twisted surface of the strands.Therefore,this FPMC-based MsS is potential to be applied for in situ inspection.The obtained experimental results verify the proposed FPMC-based MsS can excite and receive megahertz-range longitudinal guided waves in seven-wire steel strands,having a central frequency of 1.20 MHz.In the excited guided waves,L（0,1） and L（0,3） mode are the dominated components.The proposed method provides a certain foundation for the megahertz-range MsS design.