Role of Surface Texture on Workpiece Angular Deformation in Cross Wedge Rolling

The cross wedge rolling process is commonly used for the manufacturing of shaft or for preforms, being used for preliminary operation of forming cycle. The presence of angular deformation produced during the rolling process is analyzed in this paper. This work shows some experimental results obtained on parts made of steel in semi-industrial condition. Visioplasticity technique is used to measure the angular displacement occurring in some sections with reference to the adjacent ones. Thus the test samples are prepared to include surface grooves filled up with quite similar steel grade. After rolling process, angular deformations are highlighted by observations and external deformation profile. Influence of surface texture of the forming area is experimentally demonstrated. Moreover, the numerical simulation with the software FORGE is used to verify the adequacy between the observed phenomena and forecasts which can be obtained today.Conclusions about the relative influence of friction factors on the internal stresses creation are finally presented to better identify potential occurrence of these phenomena. Strain diagrams are used to bring out the magnitude of angular variations depending on local plastic strain on parts. Possible consequences for process optimization are raised

Contact Pressure Measurement System in Cross Wedge Rolling

In the cross wedge rolling process (CWR), plastic deformation is geared by a driving torque transmitted by friction on die surface. Friction plays a role which has to be further identified in this metal forming process. The local contact pressure between a cylindrical billet and flat dies seems to be a relevant parameter to characterize the severe contact conditions during the rolling. This paper deals with an experimental measurement technology, which has been designed and implemented on a semi-industrial CWR test bench with plate configuration. This measurement system using pin and piezoelectric sensor is presented, with an analysis of the system operation and design detail. Characterization of systematic error and calibration tests are then explained. Additional tests performed on hot steel preforms allow to check the ability of the contact pressure measurement system to resist under severe operating conditions. Realistic results for varying temperatures are then discussed

Contact Pressure Measurement System in Cross Wedge Rolling

In the cross wedge rolling process (CWR), plastic deformation is geared by a driving torque transmitted by friction on die surface. Friction plays a role which has to be further identified in this metal forming process. The local contact pressure between a cylindrical billet and flat dies seems to be a relevant parameter to characterize the severe contact conditions during the rolling. This paper deals with an experimental measurement technology, which has been designed and implemented on a semi-industrial CWR test bench with plate configuration. This measurement system using pin and piezoelectric sensor is presented, with an analysis of the system operation and design detail. Characterization of systematic error and calibration tests are then explained. Additional tests performed on hot steel preforms allow to check the ability of the contact pressure measurement system to resist under severe operating conditions. Realistic results for varying temperatures are then discussed

Light--absorbed orbital angular momentum in the linear response regime

In exploring the light-induced dynamics within the linear response regime, this study investigates the induced orbital angular momentum on a wide variety of electronic structures. We derive a general expression for the torque induced by light on different electronic systems based on their characteristic dielectric tensor. We demonstrate that this phenomenon diverges from the inverse Faraday effect as it produces an orbital magnetization persistent post-illumination. Indeed, our results reveal that, while isotropic non-dissipative materials do not absorb orbital angular momentum from circularly polarized light, any symmetry-breaking arrangement of matter, be it spatial or temporal, introduces novel channels for the absorption of orbital angular momentum, or magnetization. Most notably, in dissipative materials, circularly polarized light imparts a torque corresponding to a change in orbital angular momentum of $\hbar$ per absorbed photon. The potential of these mechanisms to drive helicity-dependent magnetic phenomena paves the way for a deeper understanding of light-matter interactions. Notably, the application of pump-probe techniques in tandem with our findings allows experimentalists to quantitatively assess the amount of orbital angular momentum transferred to electrons in matter, thus hopefully enhancing our ability to steer ultrafast light-induced magnetization dynamics

The role of PSA and prostate markers in screening and diagnosing prostate cancer

Objective: To create a PDT practical guide for its multiple applications in the treatment of digestive cancers.Objectif : réaliser un guide pratique de la PDT dans ses différentes applications en cancérologie digestive

L'organisation de la production métallurgique dans une ville gallo-romaine : le travail du fer à Alésia

Compte tenu des différentes études pluridisciplinaires publiées sur les activités métallurgiques du site d'Alésia nous proposons dans cet article une synthèse diachronique concernant l'organisation des ateliers et de leur production à destinations interne et externe. En effet, l'oppidum d'Alésia disposait dès le Ier siècle av. J.-C. de nombreuses forges d'où sortaient des produits de qualité. Le développement de la ville gallo-romaine vit se mettre en place plusieurs quartiers de bronziers et de forgerons notamment à l'est et au sud du centre urbain. Les études de déchets de travail et de semi-produits effectuées en laboratoire, couplées avec celle des dizaines d'ateliers ruraux du Haut-Auxois, ont permis de définir la place qu'occupaient les forges d'Alésia dans la chaîne de production du fer : essentiellement l'élaboration des objets. Mais, une petite réduction du minerai de fer est présente et surtout l'épuration de métal importé brut dans les forges adaptées à ces deux phases du travail. La production des ateliers d'Alésia, comme celle des trois autres groupements de la région dont Sombernon et Blessey-Salmaise, pourvoyait non seulement aux besoins de la ville mais aussi de ses campagnes en fournissant à leurs forges un métal épuré prêt à l'emploi. Un dense réseau routier rayonnant du Mont-Auxois facilitait ces échanges.Taking into consideration the published interdisciplinary studies on metal working at Alésia, this paper proposes a diachronic synthesis of the workshops and their production (internal and exported). From the 1st century BC, the Alésia oppidum had many smithies producing high quality goods. In the gallo-roman town, several bronze founding and blacksmiths quarters developed mainly to the East and South of the urban centre. The laboratory study of waste and half finished products from Alésia and from several rural workshops in the Auxerre region has helped to ascertain the role played by the Alésia smithies in the iron production which was essentially based on the production of objects. However, some metal reduction, either economical or specialized, was carried out as well as the purifying of imported iron in adapted smithies. The production from the Alésia workshops and also from 3 other regional groups of which Sombernon and Blessey-Salmaise, provided purified ready-to-use metal not only for the needs of the town but also for the surrounding settlements. A dense road network radiated out from the Mount Auxois facilitating this exchange.Angesichts der verschiedenen, bereits veröffentlichten fachübergreifenden Studien über das Metallhandwerk in Alésia schlagen wir in diesem Artikel eine diachrone Synthese der Organisation der Werkstättenund ihrer für interne und externe Zwecke bestimmten Produktion vor. Tatsächlich verfügte das Oppidum von Alésia seit dem 1. Jh. v. Chr. über zahlreicheSchmieden, in denen Qualitätsprodukte hergestellt wurden. Mit der Entfaltung der gallo-römischen Stadt enstanden, insbesondere östlich und südlich des Stadtzentrums, mehrere Handwerkerviertel, in denen Bronzegießer und Schmiede tätig waren. Dank der Untersuchung der Abfallprodukte und Halbfabrikate im Labor, gekoppelt mit der Untersuchung dutzender ländlicher Werkstätten des Haut-Auxois konnte der Platz definiert werden, den die Schmieden von Alésia in der Eisenherstellung einnahmen: hier wurden vor allem Fertigprodukte hergestellt. Obwohl auch Erz reduziert wurde, überwog in den, beiden Arbeitsprozessen angepassten, Schmieden doch die Läuterung importierten Rohmetalls. Die Produktion der Werkstätten von Alésia, sowie die der drei anderen Gruppierungen der Region, darunter Sombernon und Blessey-Salmaise, versorgte nicht nur die Stadt selbst sondern auch deren Umland, indem sie dessen Schmieden mit geläutertem, gebrauchsfertigem Metall belieferte. Ein dichtes Straßennetz dessen Ausgangspunkt der Mont-Auxois war, begünstigte diesen Austausch

L'organisation de la production métallurgique dans une ville gallo-romaine : le travail du fer à Alésia

Compte tenu des différentes études pluridisciplinaires publiées sur les activités métallurgiques du site d'Alésia nous proposons dans cet article une synthèse diachronique concernant l'organisation des ateliers et de leur production à destinations interne et externe. En effet, l'oppidum d'Alésia disposait dès le Ier siècle av. J.-C. de nombreuses forges d'où sortaient des produits de qualité. Le développement de la ville gallo-romaine vit se mettre en place plusieurs quartiers de bronziers et de forgerons notamment à l'est et au sud du centre urbain. Les études de déchets de travail et de semi-produits effectuées en laboratoire, couplées avec celle des dizaines d'ateliers ruraux du Haut-Auxois, ont permis de définir la place qu'occupaient les forges d'Alésia dans la chaîne de production du fer : essentiellement l'élaboration des objets. Mais, une petite réduction du minerai de fer est présente et surtout l'épuration de métal importé brut dans les forges adaptées à ces deux phases du travail. La production des ateliers d'Alésia, comme celle des trois autres groupements de la région dont Sombernon et Blessey-Salmaise, pourvoyait non seulement aux besoins de la ville mais aussi de ses campagnes en fournissant à leurs forges un métal épuré prêt à l'emploi. Un dense réseau routier rayonnant du Mont-Auxois facilitait ces échanges.Taking into consideration the published interdisciplinary studies on metal working at Alésia, this paper proposes a diachronic synthesis of the workshops and their production (internal and exported). From the 1st century BC, the Alésia oppidum had many smithies producing high quality goods. In the gallo-roman town, several bronze founding and blacksmiths quarters developed mainly to the East and South of the urban centre. The laboratory study of waste and half finished products from Alésia and from several rural workshops in the Auxerre region has helped to ascertain the role played by the Alésia smithies in the iron production which was essentially based on the production of objects. However, some metal reduction, either economical or specialized, was carried out as well as the purifying of imported iron in adapted smithies. The production from the Alésia workshops and also from 3 other regional groups of which Sombernon and Blessey-Salmaise, provided purified ready-to-use metal not only for the needs of the town but also for the surrounding settlements. A dense road network radiated out from the Mount Auxois facilitating this exchange.Angesichts der verschiedenen, bereits veröffentlichten fachübergreifenden Studien über das Metallhandwerk in Alésia schlagen wir in diesem Artikel eine diachrone Synthese der Organisation der Werkstättenund ihrer für interne und externe Zwecke bestimmten Produktion vor. Tatsächlich verfügte das Oppidum von Alésia seit dem 1. Jh. v. Chr. über zahlreicheSchmieden, in denen Qualitätsprodukte hergestellt wurden. Mit der Entfaltung der gallo-römischen Stadt enstanden, insbesondere östlich und südlich des Stadtzentrums, mehrere Handwerkerviertel, in denen Bronzegießer und Schmiede tätig waren. Dank der Untersuchung der Abfallprodukte und Halbfabrikate im Labor, gekoppelt mit der Untersuchung dutzender ländlicher Werkstätten des Haut-Auxois konnte der Platz definiert werden, den die Schmieden von Alésia in der Eisenherstellung einnahmen: hier wurden vor allem Fertigprodukte hergestellt. Obwohl auch Erz reduziert wurde, überwog in den, beiden Arbeitsprozessen angepassten, Schmieden doch die Läuterung importierten Rohmetalls. Die Produktion der Werkstätten von Alésia, sowie die der drei anderen Gruppierungen der Region, darunter Sombernon und Blessey-Salmaise, versorgte nicht nur die Stadt selbst sondern auch deren Umland, indem sie dessen Schmieden mit geläutertem, gebrauchsfertigem Metall belieferte. Ein dichtes Straßennetz dessen Ausgangspunkt der Mont-Auxois war, begünstigte diesen Austausch

Structural analysis of fMRI data revisited: improving the sensitivity and reliability of fMRI group studies.

International audienceGroup studies of functional magnetic resonance imaging datasets are usually based on the computation of the mean signal across subjects at each voxel (random effects analyses), assuming that all subjects have been set in the same anatomical space (normalization). Although this approach allows for a correct specificity (rate of false detections), it is not very efficient for three reasons: i) its underlying hypotheses, perfect coregistration of the individual datasets and normality of the measured signal at the group level are frequently violated; ii) the group size is small in general, so that asymptotic approximations on the parameters distributions do not hold; iii) the large size of the images requires some conservative strategies to control the false detection rate, at the risk of increasing the number of false negatives. Given that it is still very challenging to build generative or parametric models of intersubject variability, we rely on a rule based, bottom-up approach: we present a set of procedures that detect structures of interest from each subject's data, then search for correspondences across subjects and outline the most reproducible activation regions in the group studied. This framework enables a strict control on the number of false detections. It is shown here that this analysis demonstrates increased validity and improves both the sensitivity and reliability of group analyses compared with standard methods. Moreover, it directly provides information on the spatial position correspondence or variability of the activated regions across subjects, which is difficult to obtain in standard voxel-based analyses

Development of a Tool Design Method in Cross Wedge Rolling: Description and Applications

Lien vers le site de l'éditeur : http://www.scientific.net/KEM.611-612.1694Till now, the definition of cross wedge rolling dies requires know-how and important expertise from the designers. A decision-making methodology is being developed to provide sequential and logical steps to draw easier and faster the tool geometry. This methodology is based on designing rules found in literature that link the geometrical parameters of the desired rolled part and the geometrical parameters of the tool. Nevertheless, in the literature, the rules are not always consistent because the admissible domain for a parameter can differ from one author to another. In order to take into account this variability, a stability index is associated to each rule and to the designed tool. The methodology allows updating of the existing rules and the implementation of new rules. The set of parameters defining the geometry of the tool can be exported in the CAD/CAM software and FEM software. A case-study is presented to illustrate and validate the methodology