Due to the growing demand for very high performance in aeronautical mechanisms and systems, particular attention must be paid on the bearing modeling and design. In this framework, a fundamental role is played by high peripheral speed and very low power losses. Looking toward this direction, this paper presents an improved model of rolling bearings able to describe the system dynamic behavior and the important effect of different kinds of power losses (friction losses, fluid dynamic losses, etc.). The proposed model is characterized by a high numerical efficiency and allows the investigation of the rolling bearing behavior both under transient and steady conditions. A comparison between the experimental and simulated results is also presented in this paper. The analysis of the results is encouraging and shows a good agreement between experiments and model simulations.

The effects of Mg++ on the spatial organization of nuclei from rat hepatocytes are analyzed in the range 0-60 mM, in the presence of suitable concentrations of KCl to reproduce physiological conditions. It is shown that the scatter-signal distribution measured by means of a flow microfluorimeter is greatly affected by this range of Mg concentrations. By coupling this result to phase-contrast-automated image analysis, it is possible to identify a shrinking process induced by Mg++ in the range 0-2.5 mM, which reaches a plateau in the range 5-20 mM and is followed by a swelling process in the range 30-60 mM. The same Mg ranges are shown to affect the intercalation of the fluorochrome acridine orange into chromatin, suggesting that the shrinking-swelling phenomenon has also a molecular correspondence at the genome level. Possible implications in terms of the influence of Mg++ on the organization of chromatin inside intact cells are briefly discussed.

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Tilting pad journal bearings (TPJBs) are key components in modern rotating machines. They require accurate modeling to describe their behavior, and we considered the thermo-elasto-hydrodynamic approach. Thermo-elasto-hydrodynamic (TEHD) models are a powerful tool for machine design and analysis, but they have to assure a good compromise between accuracy and numerical efficiency. Current multi-physics TEHD models of TPJBs are very accurate; however, their numerical efficiency is still far from being satisfying for industrial applications. To partially fill this gap, we propose an innovative modeling approach based on efficient flexible multibody techniques, such as the Floating Frame of Reference Formulation (FFRF) and some extensions that can be easily coupled with different fluid dynamic models to describe the whole TPJB. The model was tested on a real TPJB geometry and validated through experimental tests. The results are encouraging and show the effectiveness of the proposed approach. Finally, the model proposed can be applied in different engineering fields, such as Oil & Gas and aeronautics, where TPJBs are typically used, where it is fundamental to always reach better performance with low energy consumption and where it is particularly important to have an efficient and accurate model to simulate long period times with brief simulation times.

In recent decades, the request for more efficient performances in the aeronautical sector moved researchers to pay particular attention to all the related mechanisms and systems, especially with respect to the saving of power. In this context, the bearing modeling and design, as well as gear coupling, play a fundamental role. Moreover, the need for low power losses also concerns the study and the implementation of advanced lubrication systems, especially for high peripheral speed. With the previous aims, this paper presents a new validated model for toothed gears, added to a bearing model; with the link of these different submodels, the whole model describes the system’s dynamic behavior, taking into account the different kinds of power losses (windage losses, fluid dynamic losses, etc.) generated by the mechanical system parts (especially rolling bearings and gears). As the bearing model, the proposed model is characterized by high numerical efficiency and allows the investigation of different rolling bearings and gears with different lubrication conditions and frictions. A comparison between the experimental and simulated results is also presented in this paper. The analysis of the results is encouraging and shows a good agreement between experiments and model simulations, with particular attention to the power losses in the bearing and gears.