Pulsed eddy current detection method based on fast Fourier transform dynamic trajectory
A technology of Fourier transform and pulsed eddy current, applied in the direction of measuring devices, material magnetic variables, instruments, etc., can solve the problems that the frequency domain information cannot be fully utilized, the lift-off interference cannot be effectively suppressed, and the lift-off effect has a great influence. Achieve fast detection speed, strong anti-interference ability and good effect
Active Publication Date: 2017-08-08
NANCHANG HANGKONG UNIVERSITY
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Problems solved by technology
The above method has the following disadvantages: (1) the feature quantity in the time domain is used for signal representation, which cannot make full use of the rich frequency domain information; (2) the lift-off effect has a great impact on the detection, and it cannot effectively suppress the unknown lift-off in the detection process. away from interference
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[0045] Embodiment: A preferred embodiment of the present invention is enumerated below. The pulsed eddy current detection method based on fast Fourier transform dynamic trajectory, the implementation process is as follows:
[0046] 1) Firstly, place the probe on the test block of the same material as the inspected piece, which can be judged to be flawless 101, and the probe is not lifted off, and the signal at this time is collected as the reference signal R 102, and the lift-off height gradually increases 103, and the collected For N lift-off signals, a pure lift-off signal database 104 is established and recorded as {L(n); n=0, 1, . . . , N-1}.
[0047] For example, the lift-off height (mm) is 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 in sequence, and 7 lift-off signals are generated, n=0, 1, 2, 3, 4, 5, 6.
[0048] 2) Next, FFT decomposition 105 is performed on the pure lift-off signal, and the amplitude and phase information of each harmonic frequency after decomposition are drawn ...
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The invention discloses a pulsed eddy current detection method based on fast Fourier transform dynamic trajectory, the steps of which are: setting a defect-free area; collecting reference signals; debugging the lift-off height; establishing a pure lift-off signal database; After the FFT analysis, the complex spectrum dynamic trajectory database of each harmonic of the pure lift-off signal is established; the dynamic scanning signal of the tested part is collected; the dynamic scanning signal of the tested part is decomposed by FFT; the dynamic trajectory and the dynamic trajectory of the complex spectrum of each harmonic of the tested part are analyzed The included angle of the dynamic trajectory of the corresponding harmonic of the pure lift-off; translate the dynamic trajectory of the inspected part to the point where the lift-off is zero; synthesize the dynamic scanning signal of the inspected part after translation; obtain the defect signal of the inspected part after suppressing the lift-off effect. The invention utilizes the rich frequency spectrum of the pulse signal, combines the complex frequency spectrum feature vector with the dynamic trajectory, can detect defects, and effectively suppress the lift-off effect in the detection process, and has the characteristics of fast detection speed, good effect and strong anti-interference ability.
Description
technical field [0001] The invention belongs to the field of eddy current nondestructive testing, and relates to a pulsed eddy current testing method, in particular to a pulsed eddy current testing method based on fast Fourier transform dynamic trajectory. Background technique [0002] Eddy current testing (Eddy Current Testing, ET) is a non-destructive testing method based on the principle of electromagnetic induction, and its detection object is the surface and near-surface defects of conductive materials. Pulsed eddy current (pulsed eddy current, PEC) technology is developed rapidly on the basis of conventional eddy current testing. Unlike traditional technology that uses a single frequency as excitation, pulsed excitation is used, 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 the sensor. If t...
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IPC IPC(8): G01N27/90G01N27/9013
Inventor 付跃文李朝夕
Owner NANCHANG HANGKONG UNIVERSITY