A method for non-destructive measurement of coating thickness by ultrasonic signal spectrum filtering technology

Abstract

The invention provides a method for measuring thickness of coatings through the ultrasonic signal spectrum filter technology in a nondestructive mode, and belongs to the technical field of ultrasonic non-destructive testing. The method includes the steps that normalization processing is conducted on reflective sound pressure P[reflection] (x1) by ultrasonic incident sound pressure P[incidence] (x0), and then normalization sound pressure reflection coefficients R (x1-x0) of the coatings are acquired, and the R (x1-x0) is expanded to plural Fourier series through the spectrum analysis technology and divided into an independent real part function Real (f) and an independent imaginary part Imag (f); Fourier transformation is conducted on a real part function V[real] (f) in an effective frequency band acquired through windowing processing to acquire a power spectrum M (tau) of the real part function V real (f), FFT filtering bandwidths are selected according to the occurrence positions of maximum values of the power spectrum, the V[real] (f) is sequentially filtered to acquire a series of cosine functions, the periods of the cosine functions are read, propagation sound time ti of ultrasonic waves in the coatings is calculated, and then the thickness of the coatings is represented by the cooperation of longitudinal wave sound velocity of the coatings. The method is not affected by material attributes and the process environment, the problems that in a conventional ultrasonic method, aliasing occurs in time domains, and resonant frequency of the spectrum is difficult to recognize are solved, and the problem of ultrasonic thickness measurement of the multiple coatings is solved.

Description

technical field [0001] The invention relates to a method for non-destructively measuring coating thickness by ultrasonic signal spectrum filtering technology, which belongs to the technical field of ultrasonic non-destructive testing. Background technique [0002] Advanced coating technology is used in many fields of national defense and national economy such as national defense and military industry, machinery manufacturing, transportation, petrochemical industry, metallurgy and mining, electric power and energy. With people's continuous pursuit of high speed, high efficiency and high quality, the requirements for surface properties of materials are getting higher and higher, and higher requirements are put forward for coating materials and coating preparation processes, from the original single-layer coating technology to double-layer coating technology. The development of new technologies such as composite coatings and gradient functional composite coatings. The detectio...

AI Technical Summary

Problems solved by technology

This method is not affected by material properties and process environment, overcomes the problems of aliasing in the time domain and difficulty in identifying spectral resonance frequencies of conventional ultrasonic methods, and solves the problem of ultrasonic thickness measurement of double-layer coatings

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