8 research outputs found

    A Hemispherical Contact Model for Simplifying 3D Occlusal Surfaces

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    Statement of problem Currently, dental articulators can recreate mandibular movements and occlusal contacts. However, whether virtual articulators can also provide information about occluding dental surfaces, functional movements, and the mandibular condyles is unclear. Purpose The purpose of this in vitro study was to evaluate the occluding surfaces on dental casts obtained from a patient and approximate them to a hemispherical contact model. Both models were tested by digitizing the Dentatus ARL dental articulator. Material and methods A combination of photogrammetry and structure from motion methods were used to scan a Dentatus ARL articulator and representative dental casts. Using computer-aided engineering and finite element analysis, contact points and action vectors to the forces on occluding surfaces and condyles were obtained for cast and hemispherical models. This experiment was performed using centric occlusion and 3 different condylar inclinations. The Kruskal-Wallis 1-way analysis of variance on ranks test was used to allow all pairwise comparisons between condylar inclination and mechanical action vector values in each location (α=.05). Results Action vectors from the cast model and each location of the hemispherical model were calculated to show the mechanical consequences and the similarity among models. Overall, no significant differences were observed for action vectors (A20 versus A40 versus A60) at each location (dental cast/hemisphere, right condylar, and left condylar) in the analysis of dental casts and the hemisphere model (.382≤P≤.999). Conclusions This study provided graphical information that may assist the dental professional in determining which occlusal contacts should be modified to attain condylar and balanced centric occlusion

    A numerical and experimental study of a new Savonius wind rotor adaptation based on product design requirements

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    This paper presents the numerical-experimental study carried out on a new rotor adapted from a Savonius rotor. Aesthetic, ergonomic and functional requirements have been incorporated into it in order to be part of sustainable consumer products. The new rotor consists of a parametric model adaptable to the dimensions and geometry of the products which it will be part of. A set of translation, symmetry, rotation and scaling operations have been applied to the bucket sections of the Savonius rotor by means of transforming the initial cylindrical buckets into topological surfaces with an organic shape. The new modified Savonius rotor and the conventional Savonius with the same Aspect Ratio have been tested in an open jet wind tunnel in order to verify the influence level of product design parameters on rotor performance, in terms of power coefficient, torque coefficient and mechanical power generated. Experimental tests have been carried out for Reynolds values in the range of [3,430·104 and 1,419·105]. A numerical analysis using an incompressible unsteady Reynolds average Navier Stockes model has been validated by means of the experimental results. Experimental and numerical results coincide with a 3.5% error. The behavior of the turbine has been analyzed by varying the angle of rotation for the sections of its buckets. Using a rotation angle of 45 ° the power coefficient values improve by 32% compared to the values obtained using an angle of 0 °. The rotor has been dimensioned for its application in a patented consumer product of small dimensions and requirements of lateral accessibility to its interior. Under these limited conditions the rotor meets the small-scale energy requirements of the product. The new rotor is designed as an aid to the energy consumption of the product in which it is incorporated, maintaining the advantages of a conventional Savonius rotor as self-starting, easy manufacture and maintenance, obtaining at the same time a product that sells better, is more able to integrate into its environment and is customizable for the consumer.This work has been supported by the University of Jaen through the project titled ”Diseño de un bastón ecológico de senderismo generador eólico hidráulico” Project Code (AC20/2015-12) and (R1A7/2017). The authors would like to thank the Mechanical Engineering Departmentat Jaen University for using the wind tunnel to achieve the experimental study

    Digitalización y visualización 3D de cerámica arqueológica

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    [ES] El sistema de documentación y registro del material arqueológico ha experimentado un notable desarrollo gracias a la aplicación de nuevas tecnologías. Estas innovaciones han resultado bastante útiles en el campo de la documentación, análisis y visualización del material arqueológico. En este artículo se expone una metodología de trabajo para la realización de modelos 3D de cerámica arqueológica. Esta metodología se encuadra dentro del proyecto CATA (Cerámica Arqueológica a Torno de Andalucía), cuyo principal objetivo es la realización de una colección de referencia de formas cerámicas completas documentadas en intervenciones arqueológicas de Andalucía. Dicha colección de referencia contiene información concerniente no sólo al proceso de fabricación, la descripción del tratamiento de superficie, o el contexto de hallazgo de la pieza, sino que también se pueden visualizar modelos 3D, permitiendo un mejor conocimiento de la pieza.[EN] The documentation system of the archaeological material has development in the last years thanks to the application of new technologies. These innovations have been quite useful in the field of the documentation, analysis and visualization of the archaeological artefacts.In this article a methodology for the achievement of 3D model of archaeological pottery is exposed. This methodology fits within the CATA project (Archaeological Wheel Pottery of Andalusia in its acronyms in Spanish). The main objective of the project is the implementation of a database which is accessible by Internet, containing assorted information about pottery vessels and fragments found in Andalusia in different periods. This reference collection contains information concerning not only the manufacture process, the description of the surface treatment, or the context of finding of the ceramics, but also 3D models that allows a better knowledge of the vessel.El desarrollo de todo este trabajo ha sido posible gracias a la concesión por parte de la Consejería de Innovación, Ciencia y Empresa de la Junta de Andalucía del Proyecto de Excelencia HUM 890 Corpus Virtual de Cerámica Arqueológica.Martínez Carrillo, A.; Ruiz Rodríguez, A.; Rubio Paramio, MÁ. (2010). Digitalización y visualización 3D de cerámica arqueológica. Virtual Archaeology Review. 1(2):133-136. https://doi.org/10.4995/var.2010.4715OJS13313612BERMÚDEZ RODRÍGUEZ, Francisco et al. (2000): Intervención virtual en el patrimonio arquitectónico. Las termas romanas de Sant Boi de Llobregat (Barcelona). Actas del XII Congreso INGEGRAF. Valladolid. Junio 2000.IMMLER, Christian (1997): El gran libro de 3D Studio Max. Marcombo. Barcelona.KARASIK, A.; SMILANSKY, U. (2006): Computation of the Capacity of Pottery Vessels Based on Drawn Profiles, Excavations at Tel Beth Shean 1989-1996, vol. I, Mazar A. (ed.), Jerusalem (Israel).LAUDON, K.C.; LAUDON, J.P. (1996): Management Information Systems, Organization and Technology (B.4) Prentice-Hall, Inc., New Jersey (United States).LOUISE, M.S. , DUNBAR, P.B. (1995): Accurately Estimation Vessel Volume from Profile Illustrations, American Atiquity 60/2, pp. 319-334. http://dx.doi.org/10.2307/282143MAGALLÓN LACARTA, J.A. (1999): Generación por ordenador de modelos tridimensionales correspondientes a distintas etapas de la catedral de la Seo. Actas del XI Congreso INGEGRAF. Logroño-Pamplona.MILLER, Phillip et al. (1996-1997): Inside 3D Studio Max.. New Riders Publishing, cop. Indianapolis.RUBIO PARAMIO, M.A. et al. (2002): "Baños Árabes del Palacio de Villardompardo (Jaén). Estudio gráfico-cronológico y diseño de una herramienta multimedia para su promoción". XII Congreso INGEGRAF. Santander

    A new method for the automated design of cooling systems in injection molds

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    This paper presents a new method for the automatic design of the cooling system in injection molds, based on the discrete geometry of the plastic part. In a first phase the new algorithm recognizes the discrete topology of the part, obtaining its depth map and detecting flat, concave regions and slender details which are difficult to cool. The algorithm performs an automatic analysis of the heat transfer, taking into account functional parameters, in order to guarantee a uniform cooling of the part. Based firstly on the limit range distance from which the horizontal straight channels lose cooling effectiveness and secondly on the depth map data, the algorithm provides an optimal layout for the cooling system of the part by adapting it to its geometry. By means of adapting the precision of the algorithm to the molded geometry, both horizontal straight channels for low concavity areas and baffle matrixes for concave regions are used. In a second phase, the parameters of the cooling system such as channel diameter, channel separation etc, are dimensioned by means of genetic optimization algorithms. A second genetic optimization algorithm ensures uniformity and balance in the layout of the cooling system for the plastic part. The result is the design of the cooling system for the plastic part with the same performance as the conformal system. A constant distance between the cooling channels and the part surface is maintained, and at the same time the manufacturing of the mold using CNC techniques and traditional metal materials could be achieved. Complementarily, the algorithm performs an interference analysis with other parts of the mold such as the ejection system. The method does not need a subsequent CAE analysis since it takes into account functional and technical parameters related to heat transfer in its design, thus ensuring its functionality. The algorithm is independent of the CAD modeler used to create the part since it performs a recognition analysis of the part surfaces, being able to be implemented in any CAD system. The data obtained in the design can be used additionally in later applications including the automated design of the injection mold.This work has been supported by the Consejeria de Economia, Innovación, Ciencia y Empleo (Junta de Andalucia-Spain) through the project titled “A vertical design software for integrating operations of automated demoldability, tooling design and cost estimation in injection molded plastic parts. (CELERMOLD)” (Project Code TI-12 TIC 1623). The authors would like to thank the reviewers for comments that improved the exposition

    A numerical and experimental study of the compression uniaxial properties of PLA manufactured with FDM technology based on product specifications

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    This paper presents a numerical and experimental study of the compression uniaxial properties of PLA material manufactured with FDM based on product specifications. A first experimental test in accordance with the requirements and conditions established in the ISO 604 standard characterizes the mechanical and elastic properties of PLA manufactured with FDM technology and product requirements in a uniaxial compression stress field by testing six specimens. A second experimental test allows analyzing the structural behavior of the industrial case, evaluating the compression stiffness, the compression yield stress, the field of displacements and stress along its elastic area until reaching the compression yield stress and the ultimate yield stress data. To improve the structural analysis of the case study, a numerical validation was carried out using two analytical models. The first analytical model applies an interpolation procedure to the experimental results of the tested specimens in order to characterize the uniaxial tension-compression curve versus the nominal deformations by means of an 8-degree polynomial function. The second model defines the plastic material as elastic and isotropic with Young's compression modulus constant and according to the guidelines established in ISO standard 604. The comparison between experimental tests and numerical simulation results for the study case verify that the new model that uses the proposed polynomial function is closer to the experimental solution with only an 0.36% error, in comparison with the model with Young's compression modulus constant that reaches an error of 4.27%. The results of the structural analysis of the mechanical element indicate that the elastic region of the plastic material PLA manufactured with FDM can be modeled numerically as an isotropic material, using the elastic properties from the experimental results of the specimens tested according to ISO standard 604. In this way it is possible to characterize the PLA FDM material as isotropic, obtaining as an advantage its easy definition in the numerical simulation software as it does not require the modification of the constitutive equations in the material database. SEM micrographs have indicated that the fracture of the failed test specimens is of the brittle type, mainly caused by the separation between the central plastic filament layers of the specimens. The results presented suggest that the use of FDM technology with PLA material is promising for the manufacture of low volume industrial components that are subject to compression efforts or for the manufacture of components by the user.This work has been supported by the University of Jaen through the project titled ” Design of a mechanical plastic device for the displacement of collection sheets for olive harvesting” Project Code (AC20/2016-10) and (ID228-R2 A8 2018)

    A new hybrid method for demoldability analysis of discrete geometries

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    In this paper, a new method for demoldability automatic analysis of parts to be manufactured in plastic injection is presented. The algorithm analysis is based on the geometry of the plastic part, which is discretized by a triangular mesh, posing a hybrid discrete demoldability analysis of both the mesh nodes and facets. A first preprocessing phase classifies mesh nodes according to their vertical dimension, assigning each node a plane perpendicular to the given parting direction. By selective projection of facets, closed contours which serve as the basis for calculating the demoldability of the nodes are created. The facets are then cataloged according to demoldability nodes that comprise demoldable, non-demoldable and semi-demoldable facets. Those facets listed as semi- demoldable are fragmented into demoldable and non-demoldable polygonal regions, causing a redefinition of the original mesh as a new virtual geometry. Finally, non-demoldable areas are studied by redirecting the mesh in the direction of the sliding side, and again applying the processing algorithm and cataloging nodes and facets. Resoluble areas of the piece through mobile devices in the mold are obtained. The hybrid analysis model (nodes and facets) takes advantage of working with a discrete model of the plastic part (nodes), supplemented by creating a new virtual geometry (new nodes and facets) that complements the original mesh, providing the designer not only with information about the geometry of the plastic piece but also information on their manufacture, exactly like a CAE tool. The geometry of the part is stored in arrays with information about their manufacture for use in downstream applications.This work has been supported by the Consejeria de Economia, Ciencia y Empleo (Junta de Andalucia—Spain) through the project titled ‘‘A vertical design software for integrating operations of automated demoldability, tooling design and cost estimation in injection molded plastic parts. (CELERMOLD)’’ (Project Code TI- 12 TIC-1623). The authors would like to thank the reviewers for comments that improved the exposition

    A New Method for Quantifying the Asymmetry of Biological Elements by Means of a Photogrammetric Technique Using a Parametric Computer-Aided Design System

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    In the area of zoology, it is of great interest to determine the degree of asymmetry existing in the different animal structures in order to establish it as a variable (biomarker). In this study, a new methodology is proposed for obtaining this variable ‘Asymmetry Index’. Forty-eight Iberian red deer antlers (Cervus elaphus hispanicus) from hunting reserves in the province of Jaen (Spain) have been used. The degree of asymmetry of their antlers between homologous points considered in the two right and left sides of each antler was obtained. The methodology is applied within a parametric Computer-Aided Design system from the photogrammetric restitution of the antler from two photographs. The procedure compares the degree of asymmetry in which the points of each of the right and left sides of the antler are found by means of lengths and angles with respect to an established reference plane based on the geometry of the specimen’s skull. As a result of the study, it has been observed that the Asymmetry Index obtained is lower in those specimens that have a high score in their hunting valuation, so it is considered that this factor can be taken into account as an objective and quantifiable indicator (biomarker)

    A New Methodology, Based on a CAD System, for Evaluating Partial and Global Asymmetries in Deer Antlers from Hunting Quality Assessment Data

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    In the field of biology, the ’biomarkers’ of the different animal species are of great relevance, as well as the relationships between them and the quality of the habitat. A study was proposed, analysing the antlers of the Iberian deer, to measure the bilateral asymmetry of its branches. The antlers are characterised in a 3D CAD model of their axial structure obtained via photogrammetric restitution from two photographs. This method quantifies the global and partial asymmetries of the antler’s structural features. The research evaluated 48 deer antlers from hunting days and taxidermy workshops. To quantify asymmetries, the measurements required are the same as those considered to assess the hunting quality of antlers. Bilateral deviations are estimated for each structural trait and the whole antler. Preliminary results showed a convergence between the values of global asymmetry and hunting quality. The methodology proved to be fast, inexpensive, and easy to implement, which facilitates its use in future asymmetry studies of other biological elements of animal or plant origin. It is only necessary that the starting data, which is the bilateral axial structure of the analysed element, is characterised in a 3D model
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