Development of a multiblock procedure for automated generation of two-dimensional quadrilateral meshes of gear drives

This article describes a new multiblock procedure for automated generation of two-dimensional quadrilateral meshes of gear drives. The typical steps of the multiblock schemes have been investigated in depth to obtain a fast and simple way to mesh planar sections of gear teeth, allowing local mesh refinement and minimizing the appearance of distorted elements in the mesh. The proposed procedure is completed with two different mesh quality enhancement techniques. One of them is applied before the mesh is generated, and reduces the distortion of the mesh without increasing the computational time of the meshing process. The other one is applied once the mesh is generated, and reduces the distortion of the elements by means of a mesh smoothing method. The performance of the proposed procedure has been illustrated with several numerical examples, which demonstrate its ability to mesh different gear geometries under several meshing boundary conditions

Merger as a Formula to Establish European Cooperative Societies

Council Regulation (EC) No 1.435/2003, of 22 July 2003, concerning the European Co-operative Statute (ECS), constitutes the legal basis for the creation of european cooperatives, facilitating the development of their cross-border activities and contributing to their economic development. So, the aim of this regulation is to enable the creation of European cooperatives by physical persons or legal entities resident or established under the laws of different Member States, but it also makes possible the establishment of European cooperatives by merger or transformation of existing cooperatives from different Member States. The aim of this paper is to show the specific features of formation of crossborder cooperatives by merger, covered by the ECS, with special attention to those aspects that distance them from the internal formation by merger, within the Spanish legal framework. For the purpose of comparison, Spain will be considered as regards the regulations governing mergers, depending on whether the ECS or the Spanish Cooperative Law is taken into consideration.Statute for a European Cooperative Society, Spanish cooperative regulation, cooperative mergers, crossborder activity, Agribusiness,

Infinite-dimensional representations of the rotation group and Dirac's monopole problem

Within the context of infinite-dimensional representations of the rotation group the Dirac monopole problem is studied in details. Irreducible infinite-dimensional representations, being realized in the indefinite metric Hilbert space, are given by linear unbounded operators in infinite-dimensional topological spaces, supplied with a weak topology and associated weak convergence. We argue that an arbitrary magnetic charge is allowed, and the Dirac quantization condition can be replaced by a generalized quantization rule yielding a new quantum number, the so-called topological spin, which is related to the weight of the Dirac string.Comment: JHEP style. Extended version of hep-th/0403146. Revised version, title and some notations are changed. References and Appendix B are adde

A 2D finite element based approach to predict the temperature field in polymer spur gear transmissions

This article describes a new numerical approach to determine the temperature field of polymer spur gears during their operation. The approach is based on an uncoupled procedure in which a mechanical problem is solved to determine the amount of heat that is generated by friction during the meshing of the gears, and then this heat is considered as a thermal load to perform a thermal analysis of a finite element model of the transmission. The amount of heat generated by friction is determined from the results of a numerical loaded tooth contact analysis of the transmission, which is based on the finite element method. The generality of the finite element method enables this approach to be applied to any kind of spur gear transmission, regardless of the geometry and the material of the gears and lubrication conditions. The resulting approach is applied to determine the temperature field of a spur gear transmission where polymer and metallic gears are combined, under several different operating conditions. The results obtained from this approach are compared to those obtained from experimental analyses, showing a good degree of similarity between them

Contribution of the deflection of tapered roller bearings to the misalignment of the pinion in a pinion-rack transmission

The misalignment of the gears is one of the main causes of premature failure in gear transmissions. This misalignment can be caused by different phenomena where the deformation of the elastic elements of the transmission usually has a major importance. In this paper, a pinion and rack transmission is used to investigate the misalignment of the pinion produced by the deflection of both shaft and bearings, focusing in the contribution of the bearings to this misalignment. For this task, a design space with 261 different cases of pinion and rack transmission has been explored. For each case, a realistic 3D FEM model (including gears, shaft and roller bearings) has been created and the coupled structural and contact problem has been solved. From the results of the FEM models, the different parameters of misalignment of the pinion have been computed and analyzed through five studies. These studies revealed the high importance of the elasticity of the bearings in the misalignment of the pinion and, in general, the important error that can be assumed when the bearings are not included in the structural models of gear transmissions.The authors express their deep gratitude to the Spanish Ministry of Science and Innovation (MICINN) for the financial support of research project ref. DPI2013-47702-C2-2-P

Análisis de la ampliación de los recursos locales hortofrutícolas mediante la internacionalización: Potencial del sector cooperativo hortofrutícola

El presente trabajo analiza la posibilidad de ampliar los recursos locales de las cooperativas hortofrutícolas mediante la internacionalización de su actividad. Para ello se examinan las estrategias de internacionalización disponibles para estas entidades y se analiza el potencial del sector hortofrutícola, mediante el estudio de los datos básicos del sector comparando entidades asociativas con las no cooperativas. Dichos datos nos permiten evaluar su potencial exportador, resultando mucho mayor en las cooperativas hortofrutícolas. Sin embargo la internacionalización se manifiesta principalmente a través de la exportación mediante acuerdos comerciales, y en menor medida, mediante la constitución de sociedades mercantiles participadas por la cooperativa, por lo que no redunda en incrementos de la intercooperación a nivel internacional, mientras sí que existen a nivel nacional. Por tanto, las conclusiones alcanzadas destacan un elevado grado de internacionalización de las cooperativas hortofrutícolas frente al sector no cooperativo y con respecto a otros sectores agroalimentarios.Cooperativas hortofrutícolas, internacionalizacion, potencial exportador., Agribusiness, Agricultural and Food Policy, Community/Rural/Urban Development, Labor and Human Capital,

An adaptive mesh refinement approach for solving nonHertzian elastic contact problems

Semi-analytical methods are a common way of solving non-hertzian contact problems when designing mechanical components. These methods require of the discretization of the domain into a set of pressure elements and their accuracy and computational cost are related to the number of elements in which the domain is discretized. But, while the accuracy increases as the pressure element mesh is refined, the computational cost increases quadratically with the number of pressure elements. So in the great majority of the cases, a commitment between accuracy and computational cost must be achieved. In this work, a new approach has been developed to improve the performance of semi-analytical methods for solving contact problems. This approach uses an adaptive mesh refinement strategy, based on the quadtree decomposition of the domain. As a result, the computational cost decreases, while the accuracy of the method remains constant

Adaptive Mesh Refinement Strategy for the Semi-Analytical Solution of Frictionless Elastic Contact Problems

Semi-analytical methods are commonly used to solve contact problems. These methods require the discretization of the domain into a mesh of pressure elements. In general, it can be said that their accuracy increases as the pressure element mesh is refined. However, the refinement of the pressure element mesh also implies an increase in their computational cost. So, in the great majority of the cases, a commitment between accuracy and computational cost must be achieved. In this work, a new approach is presented, whose main purpose is to improve the efficiency of the semi-analytical methods that are used to solve contact problems. To do so, an adaptive refinement of the pressure element mesh is implemented. This strategy allows for a reduction of the computational cost of the method, while its accuracy remains unaffected

A simple procedure for generating locally refined 2D quadrilateral finite element meshes of gears

This article describes a new procedure for automated generation of two-dimensional locally refined quadrilateral meshes of gear drives. In this new procedure, a base mesh is generated using a multiblock meshing procedure. Then, selected elements of the base mesh are subdivided to obtain a refined mesh in certain parts of the gear teeth. The proposed procedure is completed with a mesh quality enhancement technique, which is based on an optimization-based smoothing. It also includes strategies that allow to automatically identify and refine those areas of the gear that are typically subjected to elevated stress gradients. The performance of the proposed procedure is illustrated with numerical examples, and it is compared to other existing meshing procedures, both in terms of mesh distortion and accuracy of the results