Laurent Pino

A Validated Feasibility Prototype for AUV Reconfigurable Magnetic Coupling Thruster

This paper presents the concept and design of a new reconfigurable magnetic-coupling thruster (RMCT). Mechanical models, as well as digital and real-world experiments, are proposed to understand the fundamental aspects of such technology. The principle of RMCT is to reorient the propeller, and therefore the thrust vector, to the desired direction without adding or moving any motors. The focus of this study is to propose a new design to solve the problems raised in a previous work on RMCT and to understand how the transmitted coupling torque behaves with regard to the new kinematics of the propeller shaft. After introducing the models underlying this thruster design, we build a numerical simulation and validate it through experimental results. The performance of this design is then discussed based on open-loop trials and its potential integration and control. The conclusion proposes guidelines for developing an underwater prototype that will be designed and tested on real autonomous underwater vehicles.

Mechanical Behavior of a NiTi Endodontic File During Insertion in an Anatomic Root Canal Using Numerical Simulations

Abstract Superelastic NiTi shape memory alloys (SMA) have biomedical applications including rotary endodontic files. These alloys are used thanks to their flexibility, which is due to solid-solid martensitic transformation. Unfortunately, the intracanal file separation can occur during canal preparation. To avoid this problem and to have a good idea of the mechanical behavior of these instruments, finite elements simulations taking into account the real shape of root canals are proposed in this study. This is possible by using a well-adapted model describing all the particularities of SMA and representative limit conditions. The behavior model has been validated in previous studies under complex loadings. It is implemented in ABAQUS® finite elements software. The anatomic shapes of root canals are extracted by microtomography using a real tooth. They are applied as limit conditions in realized simulations to be as near as possible to clinical conditions. The mechanical behavior of an endodontic file is then simulated during insertion in a root canal without and with rotation. This permits to obtain different information like the loading applied to the instrument during its use, the stress, and the phase transformation fields through the file. This is useful not only for clinical use but also for new NiTi endodontic instruments design.

Experimental Validation of Numerical Simulations of a New-Generation NiTi Endodontic File Under Bending

The superelasticity of NiTi shape memory alloy has been used in endodontics since the 1990s. To study the mechanical behavior of endodontic instruments, a traditional approach consists in experimental investigations. However, finite element analysis constitutes another way to assess their mechanical behavior and to facilitate their design. The main aim of this study is to compare experimental and numerical bending results on different structures (NiTi wire, spreader, and instruments) to estimate the reliability of the finite element simulations. These investigations were carried out as follows. Firstly, experimental material parameters identification was performed using NiTi wires. These parameters were implemented in an appropriate NiTi model. Bending was numerically applied to the meshed structures generated by the finite element method. Experimental tests were performed on real structures under bending, with exactly the same loading, in order to compare experimental and numerical results. These results were in good agreement for each of the considered structures. This enabled the validation of the simulation results and the use of simulations to design new endodontic instruments.

Mechanical Behavior Study of NiTi Endodontic Files Taking into Account Anatomic Shape of Root Canals

Superelastic NiTi SMA is the base of endodontic files. The flexibility of these instruments permits the preparation of root canals. Unfortunately the intracanal file separation can occur. To have a good idea of the mechanical behavior of these instruments, we propose in this study the finite elements simulations taking into account the real shape of root canals. This has been possible by using a well adapted model describing all the particularities of superelastic SMA and by using representative limit conditions.