Electrodynamics of Magnetic Pulse Welding Machines: Global and Local Electrical Analogues

In this paper, a theoretical, experimental and numerical study of MPW machines is carried out. While it is known that such machines are very complex by nature because of the coupling between different parts, we used simple electrical analogues to describe its dynamics. A RLC circuit modeling the whole machine is depicted and experimental results are shown. A further study including numerical simulations allows to compute the current distribution and estimate the magnetic field within the coil but also the magnetic pressure generated in the process, all using a 2D model and reasonable assumptions. A late theoretical study opens the way for innovative experimental measurements regarding the kinetics of the deformations of metallic tubes, but also their mechanical behavior before the welding process, making use of their capacitive properties

Discrete modelling of electrical transfer in multi-contact systems

International audienceIn this work we propose to study the electrical transfer in metallic granular materials under mechanical loading. A new model of electrical conductance and the associated numerical treatment in the Discrete Element Method (DEM) framework are presented. The approach differs from the Holm's model by considering several electrical potentials inside a particle. The electrical properties of the different paths in granular medium depend on the contact reaction through the Hertz's theory. A DEM modelling allows to study the electromechanical behaviour of granular materials. Numerical simulations are carried out in 1D and 2D and are compared to experimental results in the case of a metal-metal contact. The results show a good agreement with experimental ones

DEM ball bearing model and defect diagnosis by electrical measurement

International audienceWeproposeinthispaperanewmethodforthemonitoringanddiagnosisofbearing defectswhichutilisesthesensitivityandtherichnessofthelocalelectricalsignatureof the ballbearings.Experimentalresultsshowthecapabilityoftheelectricalmeasurement to betraytheexistenceofdefect.Anewmodelofballbearingispresentedbasedon DiscreteElementMethod(DEM),inwhichthemechanicalbehaviorofballbearingis reproduced correctly.Numericalsimulationsarecarriedouttohighlighttheinfluenceof angularvelocityontheelectricalsignalofhealthyballbearing.Moreover,thenumerical simulationsareperformedinthecaseofdefectedballbearing.Theelectricalsignals obtainedareingoodagreementwiththeoreticalfrequencies.Thenumericalstudy underscorethecapabilityofelectricalresponsetodetectgeometricaldefects

Evaluation of the injection moulding conditions in soy/nanoclay based composites

International audienceBiocomposites, and generally bio-based plastics, are seen as a promising alternative to conventional plastics because they are based on renewable natural components (eco-friendly) with a lower cost. Biocomposites using soy protein and glycerol were obtained with an injection moulding technique as the thennoprocessing method. Nanoclay (Montmorillonite, MMT-Na+) was included to improve physicochemical properties of novel SPI/MMT nanocomposites prepared by injection moulding, primary attending to water uptake capacity (WUC), but also considering rheological and mechanical properties. The influence of processing conditions has been studied in order to assess the modifications taking place in the microstructure and properties of these nanocomposites. Addition of MMT-Na+ improves mechanical properties and WUC of SPI-based materials, depending on processing conditions. Injection pressure only exerts a slight enhancement of mechanical properties and WUC. However, an increase in mixing time leads to a relevant increase in WUC without impairing the mechanical properties of nanocomposites

Modélisation des phénomènes de transferts électriques dans un système multi-contacts par la Méthode des Eléments Discrets

National audienceSee http://hal.archives-ouvertes.fr/docs/00/59/29/52/ANNEX/r_S0OXR5UH.pd