A pulsed eddy current thickness measurement method for metal layer

Abstract

The invention discloses a metal layer pulsed eddy current thickness measurement method. The phase jump point of a signal in a time-frequency domain acts as thickness measurement characteristic quantity, a pulsed eddy current detection experiment is performed on multiple standard test pieces of which the thickness is known, and a relation curve between the metal layer thickness and the phase jump point is established and acts as a thickness calibration curve to assist completion of thickness measurement of workpieces to be measured in actual detection. According to the method, extraction of the thickness measurement characteristic quantity is extended to the time-frequency domain from a time domain, and resolution of the signal for parameters to be measured is fully utilized so as to be particularly suitable for thickness measurement of a nonmetal coating layer or a multilayer metal structure. Besides, thickness measurement is realized by utilizing the phase so that probe lift-off interference and metal layer thickness change can be effectively distinguished, anti-interference capacity of detection can be enhanced and accuracy of the measurement result can be guaranteed in comparison with the existing device method of directly adopting the time-domain characteristic quantity.

Description

technical field [0001] The invention belongs to the technical field of non-destructive testing, in particular to a method for measuring the thickness of a metal layer by using pulsed eddy current testing technology. Background technique [0002] In many important industrial applications, it is often necessary to measure the thickness of metal layers as a basis for evaluating the quality, safety and reliability of key components in mechanical structures. Pulsed eddy current testing technology is based on the principle of electromagnetic induction to measure the thickness of metal layers. When the excitation coil loaded with pulse voltage (current) is close to the metal specimen to be tested, a transient electromagnetic field will be induced inside the specimen. When the thickness of the specimen is different, the diffusion time and attenuation degree of the induced electromagnetic field inside the specimen will change. , thus causing the signal change of the detection probe,...

AI Technical Summary

Problems solved by technology

It completes the detection based on the phase feature quantity of the signal in the time-frequency domain, which can not only solve the problem that the interference signal caused by lift-off in the time domain is difficult to distinguish from the useful signal generated by the change of the metal layer thickness, but also realize the detection of single-layer or multi-layer metal specimens, and the thickness measurement of the metal layer in non-metallic coating specimens, to improve the accuracy of the test results

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