CN103808795B - 一种新型脉冲检测算法 - Google Patents

一种新型脉冲检测算法 Download PDF

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CN103808795B
CN103808795B CN201410053440.3A CN201410053440A CN103808795B CN 103808795 B CN103808795 B CN 103808795B CN 201410053440 A CN201410053440 A CN 201410053440A CN 103808795 B CN103808795 B CN 103808795B
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CN103808795A (zh
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王帅
王金鹤
王宇
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Ningbo LuBang Digital Technology Co., Ltd
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Huzhou University
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Abstract

本发明涉及一种新型脉冲检测算法,利用标准信号进行对比检测和分析,所述标准信号为在无缺陷试样上测得的信号,表示为y2(t),包括两个步骤:第一步:数据采集,确定参考信号和缺陷信号样本,在空气中采样,测得十组采样信号,经过滤波,得到一组采样信号y1(t),采样信号和标准信号y2(t)作为两组参考信号,在同一缺陷上不同提离情况下采样,得到十组实测的缺陷信号,经过滤波,取两组缺陷信号x(t),第二步:频谱差值;本发明能很好地提取低频特征值,从而对缺陷深度进行定量研究,精度高,实用性强。

Description

一种新型脉冲检测算法
技术领域
本发明涉及一种无损检测中噪声消除方法,具体涉及一种新型脉冲检测算法。
背景技术
脉冲涡流检测过程中,探头与检测试件之间的距离不可避免地会发生变化,产生提离效应。检测中的漏检和误差往往来自于此,因此消除提离影响对提高检测精度至关重要。目前提离效应的消除大多是对时域提取特征进行分析处理,由于瞬态信号受到外界因素的影响,因而消除提离的效果不理想。
发明内容
本发明克服了现有技术的不足,提出了一种新型脉冲检测算法,所述算法充分利用脉冲涡流检测信号频率成分丰富的特点,在频域对其进行处理,可以提取更多有用信息,更好地消除提离效应。对方波激励信号进行傅里叶级数展开后,可以看到方波的频率分量非常丰富,既有低频分量,也有高频分量,其中低频分量透入深度更深。所以脉冲涡流可以实现从导体表层到深层的检测。高频激励下的检测信号主要反映提离信息,而低频激励下的检测信号主要反映缺陷信息。提离存在时的检测信号既包含了被测试件的信息,也包含了空气中的信息,因此通过对时域中的检测信号进行频域变换后,去掉在空气中的检测信息,然后分析信号中的低频成分,就可以有效地消除提离,实现对缺陷的定量检测。
本发明的技术方案为:一种新型脉冲检测算法,利用标准信号进行对比检测和分析,所述标准信号为在无缺陷试样上测得的信号,表示为y2(t),包括两个步骤:
第一步:数据采集,确定参考信号和缺陷信号样本
在空气中采样,测得十组采样信号,经过滤波,得到一组采样信号y1(t),采样信号和标准信号y2(t)作为两组参考信号,在同一缺陷上不同提离情况下采样,得到十组实测的缺陷信号,经过滤波,取两组缺陷信号x(t)。
第二步:频谱差值
对同一缺陷上不同提离的缺陷信号以及两个参考信号进行傅里叶变换,得到两组缺陷信号傅里叶时域表示X(n)和两组参考信号傅里叶时域表示Y1(n)和Y2(n);让Y2(n),X(n)分别与Y1(n)+Y1(n)xY2(n),Y1(n)+X(n)xY2(n)相减,取绝对值后,得到差值公式:
取Xl(n)与Yl(n)的差,得到
Y(n)=δ(Xl(n)-Yl(n))
其中,δ(n)为Xl(n)-Yl(n)的函数,Y(n)包含了低频特征峰值,即缺陷信息。
本发明具有如下有益效果:
1)本发明能很好地提取低频特征值,从而对缺陷深度进行定量研究。
2)本发明能有效地消除提离效应,提高缺陷的定量检测精度。
具体实施方式
在本发明算法中,首先确定参考信号和缺陷信号样本
在空气中采样,测得十组采样信号,经过滤波,得到一组采样信号y1(t), 采样信号和标准信号y2(t)作为两组参考信号,在同一缺陷上不同提离情况下采样,得到十组实测的缺陷信号,经过滤波,取两组缺陷信号x(t)。依据时域信号的数学模型为:根据涡流检测原理,导体中电流密度减小到导体截面表层电流密度的1/e处的深度δ可表示为:
式中f为脉冲频率;σ为电导率;μ为磁导率e为自然底数,e=2.71828183。
对方波激励信号进行傅里叶级数展开后,方波的频率既有低频分量,也有高频分量,其中低频分量透入深度更深。所以脉冲涡流可以实现从导体表层到深层的检测。高频激励下的检测信号主要反映提离信息,而低频激励下的检测信号主要反映缺陷信息。提离存在时的检测信号既包含了被测试件的信息,也包含了空气中的信息,因此通过对时域中的检测信号进行频域变换后,去掉在空气中的检测信息,然后分析信号中的低频成分,就可以有效地消除提离,实现对缺陷的定量检测。
对同一缺陷上不同提离的缺陷信号以及两个参考信号进行傅里叶变换,得到两组缺陷信号傅里叶时域表示X(n)和两组参考信号傅里叶时域表示Y1(n)和Y2(n);让Y2(n),X(n)分别与Y1(n)+Y1(n)xY2(n),Y1(n)+X(n)xY2(n)相减,取绝对值后,
得到差值公式:
取Xl(n)与Yl(n)的差,得到
Y(n)=δ(Xl(n)-Yl(n))
其中,δ(n)为Xl(n)-Yl(n)的函数,Y(n)包含了低频特征峰值,即缺陷信息。

Claims (1)

1.一种脉冲检测算法,其特征是:利用标准信号进行对比检测和分析,所述标准信号为在无缺陷试样上测得的信号,表示为y2(t),包括两个步骤:
第一步:数据采集,确定参考信号和缺陷信号样本
在空气中采样,测得十组采样信号,经过滤波,得到一组采样信号y1(t),采样信号和标准信号y2(t)作为两组参考信号,在同一缺陷上不同提离情况下采样,得到十组实测的缺陷信号,经过滤波,取两组缺陷信号x(t);
第二步:频谱差值
对同一缺陷上不同提离的缺陷信号以及两组参考信号进行傅里叶变换,得到两组缺陷信号傅里叶时域表示X(n)和两组参考信号傅里叶时域表示Y1(n)和Y2(n);
让Y2(n)与Y1(n)+Y1(n)x Y2(n)相减,取绝对值后,得到差值公式:
Y / ( n ) = | Y 2 ( n ) - Y 1 ( n ) - Y 1 ( n ) × Y 2 ( n ) | m a x [ X ( n ) - Y 1 ( n ) ]
让X(n)与Y1(n)+X(n)x Y2(n)相减,取绝对值后,得到差值公式:
X / ( n ) = | X ( n ) - Y 1 ( n ) - X ( n ) × Y 2 ( n ) | m a x [ X ( n ) - Y 1 ( n ) ]
取X/(n)与Y/(n)的差,得到
Y(n)=δ(X/(n)-Y/(n))
其中,δ(n)为X/(n)-Y/(n)的函数,Y(n)包含了低频特征峰值,即缺陷信息。
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CN109632947B (zh) * 2019-01-29 2022-12-02 中国特种设备检测研究院 基于传递函数的脉冲涡流检测方法、装置及存储介质

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