浅薄缺陷的脉冲漏磁信号特征量提取

The Extraction of Characteristic Quantity of Pulsed Magnetic Flux Leakage Signal of Shallow Defects

为提高脉冲漏磁对浅薄缺陷的检测能力,提出了一种处理检测信号的二次差分方法,分离出在涡流效应的阻尼作用下产生的脉冲漏磁信号中的涡流分量,即二次差分信号。从二次差分信号中提取出了浅薄缺陷深度的新特征量——峰值时间Pt,并验证了二次差分方法的可行性。试验结果表明,和信号幅值大小相比,将Pt作为浅薄缺陷特征量,在检测浅薄缺陷时对缺陷深度的分辨率较高,同时能够克服检测探头提离所引起的缺陷特征量分辨率严重下降的问题。

In order to enhance the testing ability of pulsed magnetic flux leakage（PMFL） for shallow defects, the method of second difference for dealing with testing signals was put forward, which separated the eddy current components, namely second differential signals, caused by the damping of eddy current effect from the signals in pulsed magnetic flux leakage. From second differential signals, a new characteristic quantity of the depth of shallow defects--peak time Pt was extracted and the feasibility of the method of second difference was verified. The experimental results showed that compared with the value of signal amplitude, the resolution of the depth of defects was higher while testing shallow defects if Pt was taken as the characteristic quantity of shallow defects and at the same time, the problem of the seriously decreasing resolution of the characteristic quantity of defects caused by the lift--off of the testing probe could be solved.