Search

While thermal barrier coatings (TBCs) are being sprayed onto aero-engine turbine blades, or while the engine blade is working, high temperatures and strong impact forces will damage TBCs under thermal cycles, resulting in the coating peeling off from the blades. The current method of using ECT, IRT, or another method alone cannot achieve the real-time detection of coating defects with both high precision and high penetration power. Two detection methods, namely, terahertz pulsed imaging (TPI) and optical coherence tomography (OCT), were combined to evaluate typical defects observed in TBCs (including internal debonding cracks, surface high-temperature cracks, and surface etched cracks). The results showed that the OCT system successfully obtained the micron-level axial resolution, but the detection depth of the OCT system was limited. The TPI system achieved a higher penetration depth than OCT—hence, it can be used for the nondestructive detection and evaluation of the internal debonding defects in the sample—but its resolution needs to be improved. Following this conclusion, a method is proposed using TPI and OCT concurrently for the nondestructive testing and quantitative evaluation of TBCs on etched cracks, thus achieving progress both in terms of depth and resolution. In our experiment, defects with a depth of 519 μm and a width of 100 μm were measured. The proposed method is suitable for situations where multiple defects in TBC samples of blades need to be detected simultaneously during the working process. When there are defects deep inside the sample, more small cracks on the surface can be evaluated to achieve a combination of depth and accuracy. [ABSTRACT FROM AUTHOR]

Summary: In recent years, the demand for reliable and accurate nondestructive evaluation (NDE) of structural systems has been growing and several nondestructive testing (NDT) techniques are being combined to address the issues of uncertainty in the testing results. However, the synergistic combination of multiple NDT techniques and the interpretation of the testing results require the ability to process and analyze data from several sources, a process that is referred to as "data fusion." The latter has received considerable attention since the beginning of the 21st century, thanks to the advances in sensor technologies and data acquisition systems. Also, the new era of "Big Data" where heterogeneous data are measured by different sensors and processed for a unified purpose is another factor contributing to this rapid development and the establishment of new NDT opportunities. This article reviews the recent studies involving NDE data fusion for the inspection of structures and examines the state‐of‐the‐art mathematical expressions used in different fusion algorithms. Challenges in the handling of the NDE data and the application of fusion algorithms are also identified and discussed. A generic framework of applying NDE data fusion is described, and a roadmap for potential research prospects in NDE data fusion is provided. [ABSTRACT FROM AUTHOR]

An acoustic-excitation optical coherence vibrometer (AE-OCV) is proposed for noncontact microstructure vibration measurement and modal analysis. The vibration dynamic parameters of the microstructure can be captured with a subnanometer displacement resolution by the proposed AE-OCV using spectral wavelength calibration algorithm and spectral center correction method. The natural frequency of the microstructure could also be obtained by the developed noncontact AE-OCV system using the swept-frequency acoustic excitation method. Furthermore, a home-made spectrometer based on a high-speed linear camera could provide the system with a frequency measurement range of 0–50 kHz. The developed AE-OCV has an excellent performance in microstructures vibration measurement and modal analysis, especially for high-frequency and nanoscale vibration measurements. It is of great significance to the design of the microelectromechanical system (MEMS), such as the noncontact dynamic measurement of cantilevered beams in atomic force microscopy. [ABSTRACT FROM AUTHOR]

As a promising nondestructive testing (NDT) technique with a very adaptive physical modeling of wave transmission process, terahertz technology is used for the detection and characterization of nonpolar materials and the evaluation of layered and/or defective structures. THz-TDS can also be used to perform spectroscopic analysis and detect structural defects in thermal barrier coatings (TBCs) of aero-engines. Although it is generally difficult to measure the structure of the thin oxide layer of the thermal barrier coatings whose thickness is generally lower than 30 µm (the current axial resolution of the THz-TDS cannot exceed 30 µm). We were able to complete the detection of the oxide layer within 1-29 µm through simulation by using the SWT-BP algorithm. In this study, the analysis was performed on real-world samples, the fitting degree of the SWT-BP algorithm reached 0.77, and the minimum prediction error was less than 0.1 µm. The paper also put forward some improvement measures about the experimental results.

Background: The differential diagnosis of acute and chronic colitis remains a common clinical problem. Optical coherence tomography (OCT) is a non-invasive, high-resolution imaging technique that can be used to measure morphological changes in the intestinal wall and estimate intestinal inflammation. We aimed to conduct an ex vivo experiment on a mouse model investigate the value of OCT as a tool for the differential diagnosis of acute and chronic colitis., Methods: Mice were administered dextran sulfate sodium salt (DSS) to construct acute and chronic colitis models. Acutely- and chronically-affected intestinal walls were scanned by OCT, and then the scanned colonic tissue samples were stained with hematoxylin and eosin (HE). Structural and morphological changes indicating inflammation in the intestinal wall were evaluated in the HE sections and OCT images using different parameters. The parameters were used in one-way analysis of variance (ANOVA) to screen for a differential diagnosis of acute or chronic colitis., Results: For the HE sections, the angle of the mucosal folds, length of the basilar part, and submucosal height and area were statistically significant parameters in the comparisons between the mice with acute colitis and the control-group mice (P<0.05). In the comparisons between chronic colitis mice and control-group mice, the angle of the mucosal folds, length of the basilar part, submucosal height and area, muscularis thickness, submucosal height + muscularis thickness, and mucosal thickness were statistically significant parameters (P<0.05). Finally, in the comparisons between acute colitis mice and those with chronic colitis, the angle of the mucosal folds, submucosal height and area, muscularis thickness, submucosal height + muscularis thickness, and mucosal thickness were statistically significant parameters (P<0.05). For the OCT images, only the length of the basilar part and submucosal height + muscularis thickness were statistically significant parameters between the acute colitis mice and control-group mice (P<0.05). The length of the basilar part and submucosal height + muscularis thickness were statistically significant between chronic colitis mice and control-group mice (P<0.05). In the comparisons between acute colitis mice and those with chronic colitis, only submucosal height + muscularis thickness was a statistically significant parameter (P<0.05)., Conclusions: Certain intestinal wall parameters in OCT can be used to make a differential diagnosis between acute and chronic colitis possible. This study contributes to constructing a potential diagnostic system for evaluating colorectal inflammation using OCT., Competing Interests: Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://qims.amegroups.com/article/view/10.21037/qims-21-1062/coif). The authors have no conflicts of interest to declare., (2022 Quantitative Imaging in Medicine and Surgery. All rights reserved.)