Real-time dynamic behavior analysis of thin film during in-situ SEM tensile testing.

Thin films are widely used in micro/nano-electronics. To accurately evaluate the mechanical behavior of thin films, it is important to analyze their dynamic behavior during mechanical testing in real-time. However, high-magnification SEM (Scanning Electron Microscope) images for applying strain measurement require time-consuming. In this study, we propose a method for real-time dynamic behavior analysis of thin films using in-situ SEM testing and image-based strain measurement, to obtain the mechanical properties of the thin film material to ensure reliability. We developed an in-situ SEM tensile tester that can be installed within the limited space of a chamber and optimized the magnification and resolution settings to obtain images at 1 frame per second. Therefore, we applied an image-based strain measurement method as continuously acquired high-magnification images from SEM. This method enables us to analyze the dynamic behavior of thin film materials, including failure mechanism.

New estimation method of limit pressures for thick curved pipes under internal pressure applicable to various bend angles.

In this study, a new estimation method of limit pressures (loads) is suggested for reliability design of curved pipes under high internal pressure and temperature. The curved pipes are used in boiler pipes in a supercritical thermal power plants. To find any design parameters and their dimensions in reliability design of curved pipes, various boilers in supercritical thermal power plants in operation were investigated. In order to analyse the effect of the design parameters on the limit pressure, the design of experiment (DOE) was applied to design a curved pipes with various combinations of design parameters, and then the FE limit load analyses were performed to obtain limit pressures. The thickness of the curved pipe has the greatest effect on the limit pressure among the design parameters. Although the bend angle is design parameter, the proposed estimation methods for easily calculating the limit load do not include the bend angle and then there have been difficulties in reliability design of curved pipes with any band angle. Therefore, to solve such difficulties, two estimation methods of limit pressure (load) including bend angle were suggested and the validity of the proposed estimation methods of limit load (plastic pressure) under internal pressure was objectively verified through statistical error analysis with the 60 FE analysis results which are different from the data used when the method was derived. The proposed estimation method applicable to various bend angles shows the best results in the evaluation of mean error, maximum error, and standard deviation of error, which are evaluation criteria. The proposed estimation method shows a very good result compared to existing methods, having the mean error of 0.89%, a maximum error of 2.50%, and a standard deviation of 0.70% for all data regardless of the bend angle.

Impact of marginal defects on the accuracy of automated finish line detection in tooth preparation.

AIM: The present study aimed to evaluate the accuracy of automated detection of preparation finish lines in teeth with defective margins. MATERIALS AND METHODS: An extracted first molar was prepared for a full veneer crown, and marginal defects were created and scanned (discontinuity of finish line: 0.5, 1.0, and 1.5 mm; additional line angle: connected, partially connected, and disconnected). Six virtual defect models were entered into CAD software and the preparation finish line was designated by 20 clinicians (CAD-experienced group: n = 10; CAD-inexperienced group: n = 10) using the automated finish line detection method. The accuracy of automatic detection was evaluated by calculating the 3D deviation of the registered finish line. The Kruskal-Wallis and Mann-Whitney U tests were used for between-group comparisons (α = 0.05). RESULTS: The deviation values of the registered finish lines were significantly different according to conditions with different amounts of finish line discontinuity (P < 0.001). There was no statistical difference in the deviation of the registered finish line between models with additional line angles around the margin. Moreover, no statistical difference was found in the results between CAD-experienced and CAD-inexperienced operators. CONCLUSIONS: The accuracy of automated finish line detection for tooth preparation can differ when the finish line is discontinuous. The presence of an additional line angle around the preparation margin and prior experience in dental CAD software do not affect the accuracy of automated finish line detection.