Neural network-based hybrid signal processing approach for resolving thin marine protective coating by terahertz pulsed imaging

Tu, Wanli; Zhong, Shuncong; Shen, Yaochun; Incecik, Atilla; Fu, Xibin

doi:10.1016/j.oceaneng.2018.12.051

Cited by 34 publications

(15 citation statements)

References 23 publications

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“…Nevertheless, SWT detail coefficients have kept the main characteristic peak position unchanged and also played the role of waveform baseline adjustment. Hence, the SWT approach has the potential to assist a machine learning model to distinguish the thin interface delamination layer and previous studies had proven its effectiveness [15,22]. As shown in Figure 7, to make the cumulative contribution rate reach 100%, it is found that the cumulative contribution rate of the first 31 PCs of the SWT detail data.…”

Section: Resultsmentioning

confidence: 90%

“…Nevertheless, SWT detail coefficients have kept the main characteristic peak position unchanged and also played the role of waveform baseline adjustment. Hence, the SWT approach has the potential to assist a machine learning model to distinguish the thin interface delamination layer and previous studies had proven its effectiveness [15,22]. In this work, the prediction accuracy and reliability of the GA-BP algorithm were estimated via four parameters: root correlation coefficient (R 2 ), mean squared error (MSE), mean squared percentage error (MSPE), and mean absolute percentage error (MAPE).…”

Section: Resultsmentioning

confidence: 99%

“…In this study, the FDTD Solutions software (Lumerical Solutions Inc., Vancouver, Canada) was applied to set up the simulation model and simulate the propagation process of terahertz waves in the TBCs with various thicknesses of top coat and interface delamination. The incident broadband terahertz Gaussian waves in the range of 0.3-1.5 THz were set vertical to the TBCs surface, the reflection echoes were recorded and analyzed for the TBCs interface delamination evaluation [22,23]. Perfectly matched layer (PML) boundary condition was set in the terahertz incidence Z direction, periodic boundary conditions were set in the X and Y directions, and the complex refractive index shown in Figure 2 was imported into the FDTD model as the terahertz property of ceramic top coat to mimic the actual detection process.…”

Section: Terahertz Simulation Signal Obtained By Fdtd Algorithmmentioning

confidence: 99%

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Nondestructive Evaluation of Thermal Barrier Coatings Interface Delamination Using Terahertz Technique Combined with SWT-PCA-GA-BP Algorithm

Wang

Yin

et al. 2020

Coatings

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Thermal barrier coatings (TBCs) are usually subjected to the combined action of compressive stress, tensile stress, and bending shear stress, resulting in the interfacial delamination of TBCs, and finally causing the ceramic top coat to peel off. Hence, it is vital to detect the early-stage subcritical delamination cracks. In this study, a novel hybrid artificial neural network combined with the terahertz nondestructive technology was presented to predict the thickness of interface delamination in the early stage. The finite difference time domain (FDTD) algorithm was used to obtain the raw terahertz time-domain signals of 32 TBCs samples with various thicknesses of interface delamination, not only that, the influence of roughness and the thickness of the ceramic top layer were considered comprehensively when modeling. The stationary wavelet transform (SWT) and principal component analysis (PCA) methods were employed to extract the signal features and reduce the data dimensions before modeling, to make the cumulative contribution rate reach 100%, the first 31 components of the SWT detail data was used as the input data during modeling. Finally, a back propagation (BP) neural network method optimized by the genetic algorithm (GA-BP) was proposed to set up the interface delamination thickness prediction model. As a result, the root correlation coefficient R2 reached over 0.95, the various errors—including the mean square error, mean squared percentage error, and mean absolute percentage error—were less than or equal to 0.53. All these indicators proved that the trained hybrid SWT-PCA-GA-BP model had excellent prediction performance and high accuracy. Finally, this work proposed a novel and convenient interface delamination evaluation method that could also be potentially utilized to evaluate the structural integrity of TBCs.

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Section: Resultsmentioning

confidence: 90%

“…Nevertheless, SWT detail coefficients have kept the main characteristic peak position unchanged and also played the role of waveform baseline adjustment. Hence, the SWT approach has the potential to assist a machine learning model to distinguish the thin interface delamination layer and previous studies had proven its effectiveness [15,22]. In this work, the prediction accuracy and reliability of the GA-BP algorithm were estimated via four parameters: root correlation coefficient (R 2 ), mean squared error (MSE), mean squared percentage error (MSPE), and mean absolute percentage error (MAPE).…”

Section: Resultsmentioning

confidence: 99%

Section: Terahertz Simulation Signal Obtained By Fdtd Algorithmmentioning

confidence: 99%

See 1 more Smart Citation

Nondestructive Evaluation of Thermal Barrier Coatings Interface Delamination Using Terahertz Technique Combined with SWT-PCA-GA-BP Algorithm

Wang

Yin

et al. 2020

Coatings

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“…Examples include applying pattern recognition to discriminate failure modes in composites using AE data; 307 damage classification in carbon fibre–reinforced polymer (CFRP) laminates using artificial neural networks in UT; 308 automatic defect detection through IRT in CFRP laminates 309 and honeycomb composite structures; 310 an automated shearography system for cylindrical surface inspection using machining learning; 252 neural network-based hybrid signal processing for THz pulsed imaging. 311 Despite the exciting achievements in NDT techniques, there is still substantial work required to develop fast and affordable systems for both equipment and data processing methods to promote their practical implementation in industry.…”

Section: Discussionmentioning

confidence: 99%

Non-destructive testing and evaluation of composite materials/structures: A state-of-the-art review

Wang

Zhong

Lee

et al. 2020

Advances in Mechanical Engineering

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348

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Composite materials/structures are advancing in product efficiency, cost-effectiveness and the development of superior specific properties. There are increasing demands in their applications to load-carrying structures in aerospace, wind turbines, transportation, and medical equipment, etc. Thus robust and reliable non-destructive testing (NDT) of composites is essential to reduce safety concerns and maintenance costs. There have been various NDT methods built upon different principles for quality assurance during the whole lifecycle of a composite product. This paper reviews the most established NDT techniques for detection and evaluation of defects/damage evolution in composites. These include acoustic emission, ultrasonic testing, infrared thermography, terahertz testing, shearography, digital image correlation, as well as X-ray and neutron imaging. For each NDT technique, we cover a brief historical background, principles, standard practices, equipment and facilities used for composite research. We also compare and discuss their benefits and limitations, and further summarise their capabilities and applications to composite structures. Each NDT technique has its own potential and rarely achieves a full-scale diagnosis of structural integrity. Future development of NDT techniques for composites will be directed towards intelligent and automated inspection systems with high accuracy and efficient data processing capabilities.

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“…This work group has conducted several research projects on the terahertz non-destructive testing (NDT) of multilayered media structures. It demonstrated the THz NDT of marine protective coatings using the finite-difference time-domain method combined with the stationary wavelet transform (SWT) approach, as can be seen in our previous works [13,14]. This work investigates the THz NDT of various defective structures of multilayer organic coating systems, and performs quantitative analysis and defect identification.…”

Section: Introductionmentioning

confidence: 88%

Non-Destructive Evaluation of Hidden Defects Beneath the Multilayer Organic Protective Coatings Based on Terahertz Technology

Zhong

Luo

et al. 2021

Front. Phys.

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An organic protective coating system plays an important role for the corrosion protection of offshore metallic structures. It is of practical importance to detect possible coating defects and evaluate coating performance for corrosion degradation monitoring. Reliable defect identification can provide timely and effective maintenance to avoid serious consequences. This work investigated various multilayer organic coating systems by terahertz pulse imaging technology and aimed to explore the inspection ability of terahertz non-destructive testing (THz NDT) of protective coatings. Several types of defective coating samples were measured. The comparison of measurements obtained for sites with and without defects was provided. The changes in the signals caused by the presence of defects were explained. Structural analysis, quantitative evaluation, and defect identification were carried out in detail. The results of measurements showed that corrosion defects, paint bulge defects, and paint detachment defects can be distinguished and identified in combination with the causes of defects. It can provide effective technical guidance for terahertz technology to be gradually extended to engineering applications.

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Neural network-based hybrid signal processing approach for resolving thin marine protective coating by terahertz pulsed imaging

Cited by 34 publications

References 23 publications

Nondestructive Evaluation of Thermal Barrier Coatings Interface Delamination Using Terahertz Technique Combined with SWT-PCA-GA-BP Algorithm

Nondestructive Evaluation of Thermal Barrier Coatings Interface Delamination Using Terahertz Technique Combined with SWT-PCA-GA-BP Algorithm

Non-destructive testing and evaluation of composite materials/structures: A state-of-the-art review

Non-Destructive Evaluation of Hidden Defects Beneath the Multilayer Organic Protective Coatings Based on Terahertz Technology

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