钢轨踏面检测电磁超声表面波换能器优化设计

Optimized design of surface wave electromagnetic acoustic transducer for rail tread testing

钢轨踏面疲劳裂纹的产生严重影响了列车的运行安全,及时有效对钢轨踏面裂纹进行检测与评价具有重要意义。电磁超声换能器（EMAT）具有非接触、无需处理粗糙表面,易于实现快速自动检测技术等优点,但是易受提离影响、换能效率低,因此需要对EMAT进行优化设计以提高其检测灵敏度。建立多根分裂曲折线圈接收EMAT的有限元模型,基于正交试验表,分析了曲折线圈导线宽度、高度和根数以及永磁铁尺寸、提离对接收电压信号幅值的影响规律。在此基础上,获得了表面波EMAT的最佳参数组合,并通过实验加以验证。研究结果表明,与传统EMAT线圈相比,多根分裂曲折线圈EMAT的接收信号幅值可以提高50.8%;利用A／B扫检测方法,表面波EMAT可以有效检出钢轨踏面裂纹。

The cracks in the rail tread brings huge risk for train safety,and it is significantly necessary to detect those cracks timely and accurately. Electromagnetic acoustic transducer（ EMAT） can achieve non-contact detection without any couplant or any treatment of rough surface,and is especially prospective in online inspection of high-speed rail lines. However,the EMAT is easily affected by liftoff,and of low transducing efficiency. Thus, it is essentialto optimize the EMAT probe to ensure high detection sensitivity.Consequently,a finite element model of a multi-splitting meander coil EMAT isestablished. Based on orthogonal experiment,effects of the width and height of conductors of the coil,the number of conductors and the magnet dimensions on the amplitude of receiving voltage areanalyzed. Subsequently,the combined parameters of the surface wave EMAT areobtained,and it is verified by experiments. Results show that the amplitude of the receiving signal of the modified EMAT can be improved by 50. 8% compared to the traditional EMAT.Using A-scan and B-scan methods,the cracks in the rail tread can be effectively gauged.