用于检测厚铝板缺陷的体波EMAT优化方法

Optimal method of bulk wave EMATs used in thick aluminum plate with single flat-bottom hole

针对电磁超声换能器(electromagnetic acoustic transducer,EMAT)的换能效率低,易受外界环境噪声影响导致回波信号较小、信噪比较低的问题,提出一种使用正交试验的优化方法进行改进。该方法基于电磁场涡流效应、质点弹性动力学的波动方程及有限元法,建立了一个检测厚铝板单平底孔缺陷、收发一体的体波EMAT二维有限元模型。该模型应用正交试验和极差分析法,通过对比不同结构下的缺陷回波电压信号强弱程度,分析磁铁和线圈的结构参数对其的影响,获得了优化的模型结构参数值。同时,得出在本结构下磁铁与线圈的最佳宽度比。通过实验验证了优化结果的有效性,缺陷回波电压峰-峰值的实验与仿真结果相符。

Aiming at the problem that the transduction efficiency of electromagnetic acoustic transducers （EMATs） is relatively poor, easily affected by the noise of external environment, which result in small echo signal and low SNR, an optimization method using orthogonal test was introduced. According to the theory of electromagnetics eddy current effect, particle elastodynamics wave equation, and finite element method, a two-dimensional finite element model was established for the bulk wave EMATs in the pulse- echo arrangement, operating on the thick aluminum plate with a single fiat-bottom hole. The orthogonal test and extreme difference analysis were applied to consider the parameters of the magnet and coil , which impact on defect echo signal voltage value in different construct, and the optimized model parameters were obtained. Meanwhile, the optimal ratio of magnet width and coil width is gained in this structure. The optimized result validity is verified by the experimental results. It is shown that the experimental peak-peak value of defect reflected waves are in good agreement with simulation.