Elliptical voids commonly form in semiconductor fabrication due to incomplete deposition, void migration, or localized stress concentrations, acting as stress concentrators vulnerable to thermomechanical and thermoelectric effects that may compromise structural integrity. This study investigates the fracture behavior of thermoelectric materials containing elliptical voids under combined mechanical, thermal, and electrical loading. Closed-form solutions for electric potential, temperature, and stress fields are derived for arbitrary loading orientations and void aspect ratios. Based on the strain energy density criterion (S-criterion), both failure initiation and crack propagation trajectories can then be predicted in this study. Results indicate that loading conditions and void aspect ratios significantly impact fracture behavior. The S-criterion captures local crack initiation, while the full-field strain energy density contour plots provide a global perspective. Integrating local and global energy density distributions enables us to obtain a precise prediction of complete fracture trajectories, providing a practical reference for engineers to guide defect-tolerant design, implement targeted reinforcement, and enhance the reliability and service life of thermoelectric and semiconductor devices.

The maintenance, repair, and overhaul (MRO) of gas turbine engines are essential to safe flight operations. Engines operate for extended periods under high temperature, high pressure, and high stress, making them susceptible to damage. Damage can lead to catastrophic engine failure and compromise overall aircraft safety. Videoscope inspection is an indispensable non-destructive testing (NDT) method because it allows internal engine components, such as blades, to be examined without disassembly. However, the conventional method relies heavily on manual processes: an inspector must manually rotate numerous blades while conducting a visual inspection. This introduces significant variability, as the quality and consistency of the results depend strongly on the inspector’s skill and experience. This study presents the development of an automated gas turbine engine blade inspection system based on videoscope testing. The proposed system automates the two primary components of the inspection process. First, it uses a gearbox coupler to automatically rotate the engine blades, ensuring a consistent and stable rotational speed. Second, it employs a damage-diagnosis AI that analyzes the live videoscope feed to automatically detect and classify blade damage. By integrating automated rotation and AI-driven diagnostics, the system significantly improves the reliability, consistency, and efficiency of critical engine inspections.

This work is supported by the Korea Agency for Infrastructure Technology Advancement(KAIA) grant funded by the Ministry of Land, Infrastructure and Transport (RS-2023-00240992).

This study presents a refractive-index measurement method based on total internal reflection (TIR) using a common-path polarimetric interferometer integrated with a polarization camera. The technique exploits the phase retardation generated between the s- and p-polarized components under TIR and reconstructs the spatial phase distribution through a polarimetric phase-retrieval algorithm. The refractive index is determined from the maximum phase difference, a single parameter that provides a direct mapping to the material’s optical properties.

Unlike traditional refractometry, this method does not require precise knowledge of the incidence angle, sample curvature, thickness, or focal length, making it suitable for lenses and optical components with irregular or complex geometries. Experiments on prisms, aspheric lenses, and cylindrical lenses demonstrate a refractive-index resolution of approximately 4.8 × 10⁻⁴ with good repeatability. The primary error source—polarization misalignment—can be effectively minimized through calibration with a reference sample.

In the broader context of non-destructive testing (NDT), this technique provides a fast, contact-free, and highly sensitive means for characterizing optical materials without sample preparation or mechanical alignment, offering valuable capabilities for precision optics and advanced industrial inspection.