A pulsed eddy current detection method and device for eliminating lift-off effect

Abstract

The invention discloses a pulsed eddy current detection method and device for eliminating the lift-off effect. The detection method specifically includes: Step 1. Obtain detection signals at different lift-off heights for the tested piece at different known defect depth positions Time-domain curve and obtain the time-domain curve of the reference signal without lift-off height at the non-defective position of the test piece, and perform differential processing and extraction of eigenvalues ​​on the time-domain curves of the detection signal and reference signal to obtain differential peak voltage fitting The relationship curve between the slope of the straight line and the depth of the defect; Step 1. Quantitatively evaluate the unknown defect depth of the tested piece, obtain the time domain curve of the detection signal at different lift-off heights at the position of the unknown defect depth, and compare the detection signal with the reference signal The time-domain curve is differentially processed and the eigenvalues ​​are extracted, and the processing results are substituted into the obtained expression to obtain the unknown defect depth of the tested piece. This method eliminates the influence of the lift-off effect in the pulsed eddy current testing system.

Description

technical field [0001] The invention belongs to the technical field of non-destructive testing, in particular to the design of a pulsed eddy current testing method and device for eliminating lift-off effect. Background technique [0002] Pulsed eddy current testing technology is a new application field of eddy current testing. It determines the defect position by the time when the maximum value of the measured magnetic field appears, so as to realize the non-destructive testing and quantitative description of the defect. This technology is often used in the safety inspection of aircraft fuselage structures and engines, the reliability inspection of steam pipelines in nuclear power facilities and transportation pipelines such as oil and natural gas, and the quality monitoring in the production process of various plates, rods, pipes and other metal parts, etc. . The pulsed eddy current nondestructive testing technology changes the way of using sinusoidal signal to excite the ...

AI Technical Summary

Problems solved by technology

Multiple reference signals are preferably obtained, and the maximum magnitude gradient for each reference signal is preferably determined, the corresponding reference signal having the largest magnitude gradient closest to the test signal is identified, and that corresponding reference signal is selected in the correlation compensation procedure, but the method There are the following problems: ① In order to improve the detection accuracy, this scheme needs to obtain multiple sets of reference data, each measurement needs to measure the reference signal, and the lift-off value of the reference signal is known, and the gradient with the closest test signal must be selected The reference data to determine the difference between the selected reference signal and the test signal; ②This method is more complex in operation, and it also needs to perform differential operations on the signal to determine the gradient; ③This scheme uses an integral transmitter coil and receiver The probe of the array, the typical receiver array has 16 or 32 sensors, and the device is relatively complicated; ④ In the follow-up AD-LOC method compensation program, it is necessary to judge whether there is lift-off, determine the existing lift-off, and determine the lift-off After the lift-off exists, it is necessary to select the lift-off reference, calculate the compensation ratio, and subtract the weighted lift-off reference data from the test data to compensate the lift-off

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