基于磁致伸缩电磁超声导波的钢板焊缝缺陷检测

针对工业现场使用压电超声波检测焊缝缺陷时需使用耦合剂的问题,研究了通过无须耦合剂的基于磁致伸缩电磁超声对薄钢板焊缝中缺陷进行检测的方法,并且针对电磁超声换能效率低、信号微弱的问题,通过仿真优化了回折线圈结构参数,选择了三分裂回折线圈,并探究了导波频率对缺陷检测灵敏度的影响。仿真结果表明:相比于无分裂线圈,选择三分裂回折线圈后激励信号面内位移幅值提高了94.2%,随着导波频率增加,缺陷反射回波幅值表现出先增大再减小的变化规律。实验结果表明:S0模态Lamb波垂直入射焊缝时,焊缝本身产生的回波与缺陷信号相比相对较小,缺陷检测阈值达到1 mm,缺陷定位误差小于2 mm,证明了电磁超声导波具备检测焊缝中毫米级缺陷的能力。

Weld Defect Detection of Steel Plate Based on Magnetostrictive Electromagnetic Ultrasonic Guided Wave

In order to solve the problem of using couplant when using piezoelectric ultrasonic to detect weld defects in industrial field,the method of detecting defects in thin steel plate welds based on magnetostrictive electromagnetic ultrasonic method without couplant is studied.In view of the low efficiency of electromagnetic ultrasonic energy transfer and weak signal,the structural parameters of the meander coil are optimized through simulation,the three-split meander coil is selected,and the influence of the guided wave frequency on the defect detection sensitivity is explored.The simulation results show that the in-plane displacement amplitude of the excitation signal is increased by 94.2% when the three-split meander coil is selected compared with the non-split coil.The experimental results show that when the S0 mode Lamb wave is perpendicular to the weld,the echo generated by the weld itself is relatively small compared to the defect signal,the defect detection threshold reaches 1 mm,and the positioning error is within 2 mm.The method has the ability to detect millimeter-scale defects in welds.