电磁超声横波检测钢板减薄缺陷的有限元分析

摘要

The shear waves in measured specimen excitated by EMAT(electromagnetic acoustic transduc-er)can be applied to detect thickness and internal defect of specimen.Finite element analysis was applied to simulate the mechanism of electromagnetic ultrasonic excitation of shear wave.Through the es-tablishment of three-dimensional model of EMAT and electromagnetism coupling calculation,the distribu-tion of the surface magnetic field,eddy current and Lorenz force were obtained,the results show the mech-anism of EMAT wave excitation,which provides reference for the design of the electromagnetic ultrasonic transducer.With the coupling of electromagnetics and structural dynamics calculation,the propagation of shear waves in the specimen thickness direction was obtained,results show that the shear wave propagates in the specimen along the thickness direction,and the energy is attenuated trend.In addition,the structure dynamics analysis of the defective plate provides that the wave fluctuations occur obvious change and decay when they encounter the defect.It proves the wave excitation of EMAT can effectively detect the de-fects inside the specimen.According to the results of simulation and experiments,the method of quantitati-ving defect by shear wave detection was put forward.%电磁超声换能器（EMAT）在试件中激发的横波（剪切波）能够应用于试件厚度和内部缺陷检测，为了研究电磁超声激发横波的机理，采用有限元分析的方法，对其进行仿真分析。通过建立EMAT三维模型，进行电磁学耦合计算，获得被测试件表面磁场、涡流、洛伦兹力的分布规律，显示了EMAT激发横波的机理过程，为电磁超声换能器的设计提供参考；通过电磁学与动力学的耦合计算，获得横波在试件厚度方向的传播规律，结果表明，横波在试件中沿厚度方向传播，并且能量呈衰减趋势；对含缺陷钢板进行结构动力学分析，发现当波传播遇到缺陷时波动发生明显的改变和衰减，得出EMAT激发的横波可用以检测试件底面减薄缺陷，并通过试验验证提出横波检测缺陷时定量缺陷深度的方法。