This article is focused on the comparison between experimental and numerical friction forces obtained for a typical hydraulic 'U' rod seal. The numerical results are obtained by the inverse hydrodynamic lubrication method. The experimental results have been obtained on an original experimental device capable of measuring the friction force between a rod and two seals. The reciprocating rod speed, the temperature and pressure in the test cell are controlled. Despite the fact that the numerical results correspond to an idealized hydrodynamic problem for smooth surfaces, it was found that the numerical model agrees with experimental data when the predicted film thickness is higher than the rod roughness but largely lower than the seal roughness. This suggests that the roughness of the seal disappears under the pressure in the sealed contact and do not play an essential role in the lubrication mechanisms. However, it is clear that for very small film thickness, the full film lubrication theory for smooth surfaces is not convenient. This may imply that in these conditions mixed lubrication cannot be ignored or that adhesion phenomena, not taken into account by the lubrication theory, can appear in the contact areas.
International audienceFor non-conventional or rapid forming processes important gradients of the plastic strain and strain rate can be reached, especially for severe loadings or complex deformation paths applied to the material. It is then required to improve the accuracy of the experimental data generally obtained from high speed mechanical tests as the Split Hopkinson Pressure Bar ones (SHPB). In the same time it is necessary to define quantitatively reliable rheological constitutive equations and adequate values of corresponding material coefficients. This paper proposes to use a Finite Element model for the simulation of the entire SHPB experiment based on a new calibration method of the raw measurements, together with some applications concerning the use of special specimen shapes in order to obtain large ranges variation of plastic strains and strain rate values. A description of an inverse analysis strategy, applied in order to identify the thermo-mechanical behavior laws of the materials and the computation of the corresponding rheological parameters, is also presente
The article presents a promising technology for medical applications - additive technology by thermoplastic extrusion. Some conceptual models for knee prostheses of different constructional forms have been made using FDM technology. Different materials, including biocompatible, were considered and different 3D printing equipment was used to choose the variant with the most optimal characteristics. These conceptual models can have various beneficial applications in medicine, improving the quality and functionality of personalized prostheses.
In the present paper some aspects of the influence of the overlap ratio of the gear set on its dynamic comportment was studied. In this aim, the values of angular acceleration of two helical involute gear sets having the same characteristics -excepting the face width -are determined. The study is performed using a software in the category of The Multibody Dynamics Simulation Solution for simulation the dynamic comportment for various width of the driven gear, at various torques and various angular velocities..
The paper presents the construction and operation of a 3D printer that uses the principle of food raw material extrusion with possible applications in the food industry. The emergence of these additive technologies has led to the obtaining of complex customized three-dimensional products starting from a 3D CAD model. Among the advantages of this technology with applications in the food industry can be listed: obtaining personalized food products with innovative forms especially in the confectionery and pastry area; obtaining food products that have in the component known raw materials (allergies, intolerance), forms, colour, strictly controlled nutritional value; the possibility of integrating this technology in long-term space missions by creating foods of different shapes and compositions. Also, older people can be helped to deal with the problems of chewing and swallowing. The disadvantages of 3D printing technology with applications in the food industry are related to food safety, because strict hygiene conditions and working temperature control must be ensured. Also, the future development of this technology can lead to the saving of large quantities of food raw materials.
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