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

Abstract

The invention discloses a pulsed eddy current detection method and a pulsed eddy current detection device for eliminating a lift-off effect. The detection method specifically comprises the following steps of: 1, acquiring detection signal time domain curves of a tested part under different lift-off heights at different known defect depth positions, acquiring a reference signal time domain curve without lift-off height at a non-defect position of the tested part, and performing differential processing and characteristic value extraction processing on the time domain curves of a detection signal and a reference signal to acquire a relation curve of the differential peak voltage fitting straight line slope and the defect depth; and 2, performing quantitative evaluation on an unknown defect depth of the tested part, acquiring the detection signal time domain curves under different lift-off heights at the unknown defect depth positions, performing differential processing and characteristic value extraction on the time domain curves of the detection signal and the reference signal, and substituting the processing result into a solved expression to acquire the unknown defect depth of the tested part. According to the method, the influence of the lift-off effect in a pulsed eddy current detection system is eliminated.

Description

technical field [0001] The invention belongs to the technical field of non-destructive testing, and in particular relates to a pulsed eddy current testing method and device design for eliminating the lift-off effect. Background technique [0002] Pulsed eddy current testing technology is a new application field of eddy current testing. It uses the time when the measured maximum magnetic field appears to determine the defect position, thus realizing the non-destructive testing and quantitative description of defects. This technology is often used in the safety inspection of aircraft fuselage structure and engine, the reliability inspection of steam pipelines in nuclear power facilities and transportation pipelines such as oil and natural gas, and the quality control in the production process of various metal parts such as plates, rods, and pipes, etc. . The pulsed eddy current non-destructive testing technology changes the traditional eddy current testing, multi-frequency ed...

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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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