Search

The study presented in this paper deals with the wear phenomena which occurs during loaded rolling contact in industrial machinery. The local deformation of the local contact zone associated to the existence of tangential load generates micro slips and superficial wear. This damage leads to machinery diseases, for example in cam-roller system the kinetic of the machine may not be as smooth as initially needed. As a complement of the previous presentation in [1] authors show simulation of the wear profile which is due to successive passages of the roller on the cam path. This simulation is managed taking into account the dispersion of not well known parameters by a stochastic approach. These methods may be applied to other mechanical applications such as roller bearing analysis, for example. In this paper, we restrict our study to the quasi-stationary of a roller on a cylindrical specimen case where normal load, geometry and speed are constant during simulation. The study takes into account experimental dispersions via the construction of probabilistic density function associated with uncertain parameters such as the relative position of solids or contact characteristics such as the coefficient of friction μ. [ABSTRACT FROM AUTHOR]

The modelling of industrial systems is a very hard task because of both the number and diversity of parameters to take into account, and the complex relations between these parameters. In this paper, we are interested on the study of a fully automated Integrated Circuit (IC) semiconductor manufacturing plant (lab). In the semiconductor literature, lab behaviour analysis has very often been performed using discrete-event simulation models, but little work has been devoted to the conceptualisation of the modelling approach. Other works focus on the analysis of single parts of the lab, by simplifying the relations between its components. In such a context, the aim of this paper is to use formal methodologies to model all the components of a wafer lab, that is, its physical and control systems, as well as the fabrication process. This model specification can then be used to build a simulation model for the dynamic factory behaviour analysis. [ABSTRACT FROM AUTHOR]

In this paper, the hydrodynamic characteristics of stirred tanks equipped with a mono and double screws with both classic and modified profiles have been numerically investigated. The computer simulations are conducted within a computational fluid dynamic (CFD) code, based on resolution of the Navier-Stokes equations with a finite volume discretization. The numerical results showed that the velocity field is more efficient with the modified screw profile than the one with a simple profile. In the case of the double screw, the importance of viscous dissipation and pumping has been assessed. Also, the pumping and the energetic efficiency reach the highest values. The good agreement between the numerical results and the experimental data confirm the validity of the analysis method. [ABSTRACT FROM AUTHOR]

This paper presents the optimization of functional tolerancing by dispersions method, this later has made this evidence in manufacturing dimensions optimization. In this work the dispersions method on the basis of unknown variables is combined with the minimal transfer method for automatically the modelling of the functional requirements of a mechanical assembly. The simulation is constructed around two procedures. The first procedure executes the extraction of the functional requirements, the second procedure results in the optimization of the dispersions. The functional dimensions are synthesized by uses of the optimised values of the dispersions to compute the mean values and tolerances of the functional dimensions in the chains. They are in adequacy with the writing within the meaning of the ISO standard of the functional dimensions. [ABSTRACT FROM AUTHOR]

In this paper, some improvements in the RL model are presented in order to solve transient dynamics problems. The initial model, based on the thermo mechanics behaviour of alloy coupled with the heat equation has been implemented in a unite-element code for low frequency dynamics in previous works. Using this non linear model for transient dynamics (structural response to impact excitation) leads to non-physical solutions or to non convergence of the time integration algorithm. These behaviours are clue t;o strong non- linearities of equations that govern the transformation kinetics between both phases (austenite/martensite). Adding a relaxation term in differential equations allows the algorithms to converge without disturbing the original system. This term can be associated to a physical effect which is the propagation velocity of the phase transformation, classically considered as instantaneous in static or quasi-static simulations. The results are shown using a 2D structure excited by an impact force. [ABSTRACT FROM AUTHOR]

CAD and virtual reality tools are useful to simulate the manipulation of rigid parts, and particularly their collisions. Real time simulation need to take into account the deformation of flexible part; this suppose the computation of the deformation of parts in real time, with mechanical contact. The finite-element method can not allow a real-time response for a non-linear mechanical model (geometry, material, mechanical contact). A methodology divided into two phases is proposed. First, the learning phase consists on a calculation campaign of characteristic load cases, in respect of the requirements of the real time simulation. Then, the real time phase, used the results of the first phase by interpolation. Only the first one is exposed in this paper. The aim is to obtain quickly a reduced response. In order to attempt this goal, model reduction methods are used. We focus on three reduction levels : adaptive method, POD approach, and hyper reduction. A crush of a cylinder in rubber is used to expose the performance of the model reduction methods. [ABSTRACT FROM AUTHOR]

In this paper, the mechanical behaviour of a titanium alloys is modelised for the cold forming processes. The elasto-plastic constitutive law is decomposed in an anisotropic plastic criterion, an isotropic hardening and a kinematic hardening. Non quadratic criteria have been developed by Cazacu et al. (Orthotropic yield criterion for hexagonal closed packed metals, Tnt. J. Plasticity 22 (2006) 1171-1194), to model the plasticity of hexagonal closed packed materials. The implementation of this model in a finite element software switches between two bases, the equilibrium is calculated in a reference basis and the anisotropy axes define a local basis, updated by the deformation gradient. An identification procedure, based on tensile tests, allows to define all the parameters needed to model the elasto-plastic behaviour. Simulation of cold forming processes (bulging and deep drawing) have been done to validate this model. Numerical results are compared with experimental data, obtained from speckles analysis. [ABSTRACT FROM AUTHOR]

Fluid-structure interaction in tube bundles: homogenisation methods, physical analysis. It is well known that the movements of a structure may be strongly influenced by fluid. This topic, called "Fluid Structure Interaction" is important in many industrial applications. Tube bundles immersed in fluid are found in many cases, especially in nuclear industry: (core reactors, steam generators,...). The fluid leads to "inertial effects" (with a decrease of the vibration frequencies) and "dissipative effects" (with higher damping). The paper first presents the methods used for the simulation of the dynamic behaviour of tithe bundles immersed in a fluid, with industrial examples. The methods used are based on the Euler equations for the fluid (perfect fluid), which allow to take into account the inertial effects. It is possible to take into account dissipative effects also, by using a Rayleigh damping. The conclusion focuses on improvements of the methods, in order to take into account with more accuracy the influence of the fluid, mainly the dissipative effects, which may be very important, especially in the case of a global fluid flow. [ABSTRACT FROM AUTHOR]

Abstract: To determine the strain and stress in the biological soft tissues such as ligaments, tendons or arterial walls, anisotropic hyperelastic constitutive laws are often used in the context of finite element analysis [J.A. Weiss, B.N. Maker, S. Govindjee, Finite element implementation of incompressible, transversely isotropic hyperelasticity, Comp. Meth. Appl. Mech. Engng. 135 (1996) 107–128]. In the present paper, we propose to realize such a study together with a analytical study. This study allows for the understanding of the reason why it does not exist a one-to-one correspondence between the principal stretch and the fourth invariant of the dilatation tensor for the material model proposed by Holzapfel, Gasser and Ogden [G.A. Holzapfel, T.C. Gasser, R.W. Ogden, A new constitutive framework for arterial wall mechanics and a comparative study of material models, J. Elasticity 61 (2000) 1–48; T.C. Gasser, R.W. Ogden, G.A. Holzapfel, Hyperelastic modelling of arterial layers with distributed collagen fibre orientations, J. R. Soc. Interface 3 (2006) 15–35]. In fact, the relationship becomes non-bijective when the angle between the collagen fibers and the circumferential direction is greater that a critical angle of 54.73°. Importance of this critical angle was also discussed by Guo et al. (2006). To cite this article: F. Peyraut et al., C. R. Mecanique 337 (2009). [Copyright &y& Elsevier]

For FEM-based numerical simulation, one must know the particular mechanical properties. This paper presents a thermomechanical characterization study on two ternary alloys (92.5Pb-5Sn-2.5Ag and 95.5Pb-2.5Ag-2Sn) used in the electronics industry. By means of Dynamic Mechanical Analysis (DMA), the effects of temperature (from +35 to +125 °C) and stress rates (from 0.1 to 10 N.min-1) on mechanical properties -- secant modulus, yield strength and ultimate tensile strength -- of 92.5Pb-5Sn-2.5Ag/95.5Pb-2.5Ag-2Sn alloy were investigated. [ABSTRACT FROM AUTHOR]