脉冲涡流检测提离效应的抑制方法

脉冲涡流检测中由于探头倾斜或被测对象表面不光滑等原因容易产生提离效应,提离效应严重影响着脉冲涡流无损检测的结果。提出了一种基于差分信号二阶微分零时刻值匹配补偿的方法。首先建立相应的提离参考数据库,然后通过索引二阶微分零时刻值匹配提离参考信号,计算补偿比,利用补偿公式对提离效应进行抑制。通过试验发现,经该方法处理后的有提离差分信号能够与无提离的差分信号可以很好的吻合,消除了提离效应对差分信号的影响。试验结果表明了该方法能够对多层金属结构的内部缺陷检测具有较好的提离抑制效果。

Reduction of Lift-off Effects to Pulsed Eddy Current Testing

Pulsed eddy current testing（PEC）is susceptible to lift-off effect because of the probe inclination or irregular sample surface,which has serious influence on the result of pulsed eddy current testing.A new technique to reduce lift-off effect based on second-order differential at starting point is proposed.The first thing is to build a lift-off reference database first,and afterwards to determine the lift-off value of experimental signals in the inspection by indexing second-order differential value at starting point in the lift-off reference database.Then the compensation ratio is calculated and a compensation formula is used to suppress the lift-off effect.After being processed by proposed method,the differential signals with lift-off noise agree well with the differential signals without lift-off noise.Experimental results show that the lift-off effect has been significantly reduced by using this method in internal defect detection of multi-layer metal structure with pulsed eddy current method.