Coating thickness measuring method under unknown ultrasonic velocity condition

Abstract

The invention discloses a coating thickness measuring method under an unknown ultrasonic velocity condition, and belongs to the technical field of ultrasonic non-destructive testing of materials. A set of an ultrasonic pulse echo detection system composed of an ultrasonic flaw detector, a delay block probe, a digital oscilloscope and a computer with MATLAB software is adopted in the measuring method. For the problems that echo signal aliasing exists and sound velocity is unknown in the ultrasonic coating thickness measuring process, and the coating thickness cannot be measured due to the fact that fluctuation exists under the different technological parameters or non-homogeneous conditions, an ultrasonic pulse echo technique is adopted, and the coating thickness of a sample and the ultrasonic velocity are simultaneously inverted by combining an ultrasonic sound pressure reflection coefficient magnitude spectrum analyzing method with a correlation coefficient matching method. The measuring method has the advantages of being clear and definite in principle, easy to achieve, high in matching precision and the like, the limitations that an existing Gauss-Newton inversion method is complex in calculation, higher in requirement for initial value selection and difficult to be applied to engineering application are overcome, and the good application and popularization prospect is achieved.

Description

technical field [0001] The invention relates to a coating thickness measurement method under the condition of unknown ultrasonic sound velocity, and belongs to the technical field of ultrasonic nondestructive testing of materials. Background technique [0002] Coating materials have been widely used in many fields such as aerospace, oil and gas transportation, automobile manufacturing and biomedical engineering, and occupy an increasingly important position in the field of engineering technology. Among a series of indicators that characterize the performance of the coating, the thickness is not only a parameter that characterizes the geometric size of the coating itself, but also has a great impact on the performance and life of the coating. It is impossible for the coating thickness to reach or exceed the design value. If the desired effect is achieved, and the thickness is too large or uneven, it may reduce its bonding strength and service life, cause the plasticity of the...

AI Technical Summary

Problems solved by technology

Aiming at the problem that the coating thickness cannot be measured due to the aliasing of echo signals, unknown sound velocity and fluctuations under different process parameters or heterogeneous conditions in the process of ultrasonic thickness measurement of coatings, ultrasonic pulse echo technology is adopted, combined with ultrasonic sound pressure reflection Simultaneous inversion of sample coating thickness and ultrasonic sound velocity by coefficient amplitude spectrum analysis method and correlation coefficient matching method

This method has the advantages of clear principle, easy implementation, and high matching accuracy. It overcomes the limitations of the existing Gauss-Newton inversion method, such as complex calculation, high requirements for initial value selection, and difficulty in engineering applications. It has good promotion and application prospect

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