Pulse eddy current detection lift-off effect inhibiting method based on high-pass filtering

A high-pass filtering, lift-off effect technology, applied in the direction of material magnetic variables, etc., can solve the problem of the influence of voltage noise of differential signals, and achieve the effect of accurate indication, accurate indication, and accurate lift-off height.

Inactive Publication Date: 2015-02-04
NANCHANG HANGKONG UNIVERSITY
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Problems solved by technology

However, the voltage of the differential signal in the time domain is also susceptible to noise

Method used

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  • Pulse eddy current detection lift-off effect inhibiting method based on high-pass filtering
  • Pulse eddy current detection lift-off effect inhibiting method based on high-pass filtering
  • Pulse eddy current detection lift-off effect inhibiting method based on high-pass filtering

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Embodiment

[0050] Example : realize the embodiment flow process of the present invention as follows:

[0051] 1) First, place the probe 1 on a test block of the same material as the tested sample 2, which can be judged to be free of defects, and the probe 1 has not been lifted off. The signal at this time is collected as a reference signal. The lift-off height gradually increases, and the N lift-off calibration signals, establish a lift-off calibration signal database and record it as {L(n);n=0,1,…,N-1}.

[0052] For example, the lift-off height (mm) is 0, 0.1, 0.3, 0.5, 0.8, 1.0, 1.5, 2.0 in sequence, and 8 lift-off calibration signals are generated, n=0, 1, 2, 3, 4, 5, 6, 7.

[0053] 2) Secondly, perform high-pass filtering on the lift-off calibration signal and reference signal, subtract the filtered reference signal from the filtered lift-off calibration signal to obtain a differential signal, extract its differential peak value, establish a differential peak value database and re...

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Abstract

The invention discloses a pulse eddy current detection lift-off effect inhibiting method based on high-pass filtering. The method specifically comprises the following steps: setting an area free of defect; collecting a reference signal; debugging life-off height; establishing a calibrating signal database; establishing differential peak value database; collecting an initial test signal; extracting a differential peak value; determining a database reference number; selecting a lift-off calibrating signal; and obtaining a test signal without the lift-off effect. According to the method disclosed by the invention, as a novel characteristic quantity is used for judging lift-off approximate altitude, after high-pass filtering, the differential peak value of the signal can well indicate a lift-off distance, so that the physical meaning is clear. Moreover, the lift-off height can be accurately indicated, so that the method has an application value in actual detection.

Description

technical field [0001] The invention belongs to the field of electromagnetic eddy current nondestructive testing, relates to a method for suppressing the lift-off effect, in particular to a method for automatically eliminating the lift-off effect in the process of pulsed eddy current testing based on high-pass filtering. Background technique [0002] Eddy current testing is a non-destructive testing method based on the principle of electromagnetic induction, and its testing objects are surface and near-surface defects of conductive materials. Pulsed eddy current testing technology is rapidly developed on the basis of traditional eddy current testing. Unlike traditional technology that uses a single frequency as excitation, it uses pulsed excitation, which is a periodic rectangular pulse. The electromagnetic field of the pulse excitation current excites the pulse eddy current in the conductor, and the electromagnetic field generated by the pulse eddy current is received by th...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N27/90
Inventor 付跃文李朝夕
Owner NANCHANG HANGKONG UNIVERSITY
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