Coating Thickness Detection Method Based on Fresnel Matrix Thz Wave Propagation Model

Abstract

The invention discloses a coating thickness detection method based on a Fresnel matrix THz wave propagation model. Starting from the electromagnetic field theoretical model, a normal incident THz wave is established according to a reflective THz time-domain spectrum system used when detecting the coating thickness. Reflective propagation one-dimensional electric field model in multi-layer dielectric structure, based on which Fresnel coefficient matrix and phase matrix are introduced, Fresnel coefficient matrix THz wave propagation model is proposed, and the model is verified; The least squares thickness optimization method of the Nell coefficient matrix THz wave propagation model realizes the quantitative detection of the coating thickness, and solves the coating thickness through iterative optimization, so that the minimum residual square sum of the difference between the simulation result and the measurement result is the smallest, realizing High-precision optimization of thickness parameters; introduce the distance parameter D between the THz transmitter and the tested part TS , and visualize the distance error between the THz transmitter and the tested part, further improving the accuracy of coating thickness detection.

Description

technical field [0001] The invention belongs to the field of non-destructive testing, and in particular relates to a high-precision coating thickness testing method based on a Fresnel matrix THz wave propagation model. Background technique [0002] With the continuous development of science and technology and the continuous improvement of mechanical structure processing technology, engineering has put forward higher requirements for the performance of modern components. Since the performance improvement of modern components usually depends on the special properties of materials, in order to ensure the reliability of components It is necessary to use corresponding technical means to protect and strengthen materials, and coatings are usually used to improve product performance such as durability and reliability of components. Considering the complex environment that components may encounter in actual engineering applications, only one layer of coating may not be able to meet t...

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Problems solved by technology

[0005] Since the THz wave thickness measurement method measures the thickness of the coating through the time-of-flight difference of the reflected echoes of the THz wave at the interface of different media, when the coating is a thin layer (in fact, the coating is usually even Thin layer), usually because the time-of-flight difference is too small, it is difficult to distinguish the upper and lower surface echoes of the coating in a timely and effective manner, which will lead to low detection accuracy, poor efficiency or even undetectable coating thickness. The phenomenon

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