Simulation numérique d'un disque de frein automobile par une methode de calcul eulerien

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Une méthode de calcul de structures soumises à des chargements mobiles

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Multiscale approach for anisothermal high-cycle fatigue

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Optimization of a stabilized x-fem formulation for frictional cracks

International audienceAn efficient stabilized nonlinear LATIN solver dedicated to frictional cracks in the X-FEM framework is proposed. The performance of such a solver has already been emphasized in detail in a previous paper of Gravouil et al. [Stabilized global–local X-FEM for 3D non-planar frictional crack using relevant meshes, Int. J. Numer. Methods Eng. 88 (2011)1449–1475] Here, an optimization of the search direction of the LATIN solver is proposed. Intrinsic a priori formulas are proposed independently on the friction coefficient, the finite element mesh, the geometry and the boundary conditions. About one hundred thousand of calculations have been carried out in order to show the existence of a unique set of parameters ensuring the optimal convergence rate. The number of iterations required to reach the given level of accuracy is plotted versus two numerical parameters introduced, the search direction k and the stabilization operator . A considerable decrease in the number of iterations and thus in the computing time is obtained, an important condition to carry out with a maximum efficiency of 3D simulations

Simulation Tools for Virtual Homologation of Pantographs

This paper addresses the use of numerical simulations to extend the physical pantograph homologation to virtual processes. Based on existing standards criteria, the methodology presented here leads to time reduction and cost savings in an effort for the acceptance of a new vehicle already accepted in other countries. The main goal is to guarantee full confidence in the proposed methodology and to make the final homologation decision easier to take. It is composed of three steps: "validation", "modification" and "extension". Firstly, an enhanced validation tool is proposed to improve comparisons between simulation and inline measurements. Secondly, several kinds of irregularities are introduced in the numerical models such as contact wire height and aerodynamic forces to make the simulations closer to the operating conditions. Finally, a new graphical tool is proposed in order to assess the dynamic behaviour of the interoperable pantograph catenary couple in a large range of operational conditions. Called a "homologation map", this mapping tool gathers existing limits from the standards on the same graph. This procedure is exemplified by extending the homologation of a French pantograph under the German catenary and applied to multiple units

Determination of the stabilized response of a structure undergoing cyclic thermal-mechanical loads by a direct cyclic method

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XFEM crack propagation under rolling contact fatigue

5th Fatigue Design Conference, Cetim, Senlis, FRANCE, NOV 27-28, 2013International audienceTo assure the security, heavy monitoring and maintenance procedures for the fatigue of rails are set up by infrastructure managers. In order to go towards a more cost efficient railway system, it is essential to optimize the maintenance of rails: frequency of monitoring, rail replacement strategy, grinding policy... To progress in this area, a numerical modeling tool has been developed thanks to a long-term collaboration between railway organizations (SNCF, RFF, RATP), rail producer (Tata Steel) and research institutes and universities (INRETS, LMS, MECAMIX, INSA) within the IDR2 consortium (Initiative for Development and for Research on Rail). This modelling starts with a dynamical simulation of the vehicle rolling on a track, from which the cyclic mechanical state of the rail is calculated by means of a 3D finite element simulation and an original and time-cost efficient direct stationary algorithm. Finally, a fatigue analysis of the rail is performed with the Dang Van criterion. The modeling tool has been recently completed with the simulation of the crack propagation in the rails. A two-scale frictional contact fatigue crack model developed within the X-FEM framework is used to solve the crack problem. Using this approach, contact and friction between the crack faces is taken into account in the simulation. Realistic residual stresses, coming from dedicated software developed by SNCF are introduced in the propagation simulation via projection of the asymptotic mechanical fields. 2D Crack growth is performed taking into account the residual stresses. The results highlight their influence on the crack growth rate. Finally 3D preliminary results are introduced