Validation of a double-semicircular notched configuration for mechanical testing of orthodontic thermoplastic aligner materials.

The potential of using specimens with a double-semicircular-notched configuration for performing tensile tests of orthodontic thermoplastic aligner materials was explored. Unnotched and double-semicircular-notched specimens were loaded in tension using a universal testing machine to determine their tensile strength, while finite element analysis (FEA) and digital image correlation (DIC) were used to estimate stress and strain, respectively. The shape did affect the tensile strength, demonstrating the importance of unifying the form of the specimen. During the elastic phase under tension, double-semicircular-notched specimens showed similar behavior to unnotched specimens. However, great variance was observed in the strain patterns of the unnotched specimens, which exhibited greater chance of end-failure, while the strain patterns of the double-semicircular-notched specimens showed uniformity. Considerable agreement between the theoretical (FEA) and practical models (DIC) further confirmed the validity of the double-semicircular-notched models.

Two parabolic-hyperbolic oriented partial differential equations for denoising in electronic speckle pattern interferometry fringes.

Oriented partial differential equation (OPDE)-based filtering methods have been demonstrated to be a powerful tool for denoising while preserving all fringes. In this paper we propose new OPDE-filtering models, named parabolic-hyperbolic oriented partial differential equations (PH-OPDEs), based on variational methods. We test the proposed PH-OPDEs on two computer-simulated and two experimentally obtained ESPI fringe patterns with poor quality, and compare our models with related OPDE models. The experimental results have demonstrated that the new models have significantly better performance in numerical stability and computational efficiency as compared with the previous OPDE models.