Nondestructive evaluation of multilayered paint films in ambient atmosphere using terahertz reflection spectroscopy

Choi, Jindoo; Kwon, Won Sik; Kim, Kyung-Soo; Kim, Soohyun

doi:10.1016/j.ndteint.2016.02.011

Cited by 14 publications

(3 citation statements)

References 30 publications

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“…part of the condition-based maintenance strategy and helps lower the maintenance cost. Similarly, accurate paint thickness measurement is a critical requirement in the automotive industry, and THz spectroscopy is a useful tool for such applications [29,30]. NDE of fibre-reinforced composites is another area where THz spectroscopy can be used [31].…”

Section: Introductionmentioning

confidence: 99%

Non-destructive evaluation of coatings using terahertz reflection spectroscopy

Sachin¹,

Vijayan²,

Kini³

2022

J. Opt.

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Terahertz time-domain spectroscopy (THz-TDS) provides a non-contact, non-destructive method for evaluating different materials and their properties. This short review discusses the commonly used numerical models for the non-destructive estimation of thickness, refractive index, surface and interface roughness of paints, thermal barrier coatings, and polymer coatings using THz-TDS in the reflection geometry. To demonstrate the applicability of these models, we used paint layers on metallic substrates and extracted different paraments by fitting the experimental THz-TDS data. We conclude by discussing further steps to improve the efficiency of the fitting procedure used to extract the layer parameters.

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Section: Introductionmentioning

confidence: 99%

Non-destructive evaluation of coatings using terahertz reflection spectroscopy

Sachin¹,

Vijayan²,

Kini³

2022

J. Opt.

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“…Approaches with a higher resolution, that can provide a global picture of the individual layer thickness for an entire multilayer coating, in a nondestructive and noncontact fashion, are therefore of considerable interest. Terahertz (THz) time-of-flight (TOF) tomography, as a nondestructive, noncontact, and nonionizing approach, has achieved success for a range of applications, including pharmaceuticals [8], [9], archaeology [10], [11], steel production [12], [13], and security [14], [15]. In particular, THz TOF tomography has been applied to measure individual layers in multilayer paint coatings in Refs.…”

Section: Introductionmentioning

confidence: 99%

Thickness characterization of multi-layer coated steel by terahertz time-of-flight tomography

Zhai

Locquet

Roquelet

et al. 2020

NDT & E International

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Terahertz time-of-flight tomography is employed to characterize the individual layers in a multilayer coating on steel substrates. The multilayers, containing up to three layers, consist first of a cataphoretic layer, sealer, and varnish progressing upward from the steel substrate. The individual layer thicknesses were reconstructed from the experimental data using autoregressive spectral extrapolation based on the modified covariance method (AR/MCM), which extrapolates the frequency components of the transfer function into the low signal-tonoise-ratio (SNR) regions from the high SNR regions. Due to the high sensitivity of AR/MCM to the presence of noises, wavelet denoising, in some cases, was needed to precondition the data prior to application of AR/MCM. The method is verified numerically and experimentally, showing that it can reconstruct individual layers in the 10-m range, and good agreement is found between the thicknesses of individual layers extracted by AR/MCM and characterized by eddy-current measurements.

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“…This reflectivity can be turned to advantage in the NDE of coatings on metals. To date, THz imaging has been demonstrated on automobile paints [17] and marine paints [18], thermal barrier coatings of gas turbine blade [19], and marine protective coatings [20]. Various efforts have also been made to enhance the depth resolution of THz imaging, for example using the time-domain numerical parameter fitting method based on multiple regression analysis [21], fitting the theoretical model with the experiment transfer function in the frequency domain [22], and multivariate analysis [23].…”

Section: Introductionmentioning

confidence: 99%

Terahertz Quantitative Nondestructive Evaluation of Failure Modes in Polymer-Coated Steel

Locquet¹,

Citrin²

2017

IEEE J. Select. Topics Quantum Electron.

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Terahertz reflective imaging is applied to characterize the failure modes in a polymer coating on a steel plate. The coating was initially scratched, then after accelerated aging, several types of failure have occurred. In order to resolve the thin coating (∼50 µm), terahertz frequency-wavelet domain deconvolution is implemented. With the deconvolved signals, the temporally overlapping echoes of the incident, roughly singlecycle terahertz pulse are clearly resolved, and three important failure modes, viz. corrosion, delamination, and blistering, are characterized quantitatively. Terahertz images in three dimensions clearly exhibit the coating thickness distribution across the entire damaged coating, highlighting the terahertz features associated with different failure modes, thus demonstrating that terahertz imaging can be considered as an effective modality for characterizing damage mechanisms in polymer coatings on metals.

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Nondestructive evaluation of multilayered paint films in ambient atmosphere using terahertz reflection spectroscopy

Cited by 14 publications

References 30 publications

Non-destructive evaluation of coatings using terahertz reflection spectroscopy

Non-destructive evaluation of coatings using terahertz reflection spectroscopy

Thickness characterization of multi-layer coated steel by terahertz time-of-flight tomography

Terahertz Quantitative Nondestructive Evaluation of Failure Modes in Polymer-Coated Steel

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