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Sinou J.-J.,CNRS Tribology and Dynamic Systems Laboratory
Journal of Vibration and Acoustics, Transactions of the ASME | Year: 2012

This paper proposes to use a polynomial chaos expansion approach to compute stochastic complex eigenvalues and eigenvectors of structures including damping or gyroscopic effects. Its application to a finite element rotor model is compared to Monte Carlo simulations. This lets us validate the method and emphasize its advantages. Three different uncertain configurations are studied. For each, a stochastic Campbell diagram is proposed and interpreted and critical speeds dispersion is evaluated. Furthermore, an adaptation of the Modal Accordance Criterion (MAC) is proposed in order to monitor the eigenvectors dispersion. © 2012 American Society of Mechanical Engineers.


Sinou J.-J.,CNRS Tribology and Dynamic Systems Laboratory | Faverjon B.,CNRS Contacts and Structural Mechanics Laboratory
Journal of Sound and Vibration | Year: 2012

The aim of this paper is to investigate the effects of the presence of a transverse crack in a rotating shaft under uncertain physical parameters in order to obtain some indications that might be useful in detecting the presence of a crack in rotating system. The random dynamic response of the cracked rotor is evaluated by expanding the changing stiffness of the crack (i.e. the breathing mechanism) as a random truncated Fourier series. To avoid the use of the Monte Carlo simulations (MCS), an alternative procedure that is based on a combination of the Harmonic Balance Method and the Stochastic Finite Element Method (SFEM) using the Polynomial Chaos Expansion (PCE) is proposed. So the response of the Fourier components of the cracked rotor is expanded in the polynomial chaoses. The random dynamic response obtained by applying this procedure is compared with that evaluated through numerical integration based on the Harmonic Balance Method and the Monte Carlo simulations. © 2011 Elsevier Ltd. All rights reserved.


Didier J.,CNRS Tribology and Dynamic Systems Laboratory | Sinou J.-J.,CNRS Tribology and Dynamic Systems Laboratory | Faverjon B.,CNRS Contacts and Structural Mechanics Laboratory
Journal of Sound and Vibration | Year: 2012

In this paper, the quantification of uncertainty effects on the variability of the nonlinear response in rotor systems with multi-faults (such as unbalance, asymmetric shaft, bow, parallel and angular misalignments) is investigated. To take account of uncertainties in this kind of nonlinear problem, it is proposed to use the Harmonic Balance Method (HBM) with a polynomial chaos expansion (PCE). The efficiency and robustness of the proposed methodology is demonstrated by comparison with Monte Carlo simulations (MCS) for different kinds and levels of uncertainties. © 2011 Elsevier Ltd. All rights reserved.


Feulvarch E.,CNRS Tribology and Dynamic Systems Laboratory
Comptes Rendus - Mecanique | Year: 2012

A Lagrangian approach is proposed for modeling interdiffusion phenomena in solid metals. In the first section, a formulation of diffusion equations in terms of mass fraction is developed. The specificity of this approach lies in the choice of the convection velocity. In this work, it is defined as being equal to the massic average velocity. An interdiffusion strain rate tensor is also proposed to model the mass movements induced by interdiffusion phenomena. In the second section, a finite element procedure is proposed to simulate the coupled problem which includes diffusion equations and momentum balance. A one-dimensional example is presented to show the relevance of the approach developed for an interdiffusion couple. © 2012 Académie des sciences.


Sinou J.-J.,CNRS Tribology and Dynamic Systems Laboratory
Mechanics Research Communications | Year: 2012

The identification of new scientific challenges, as well as the increasing high-performance computing support, indicates that the benefits of applying novel nonlinear techniques for crack detection will continue to grow. So, significant effort has been invested in recent years to develop effective techniques to detect crack in mechanical structures. The objective of this paper is to discuss and propose a robust diagnostic of damage based on non-linear vibrational measurements with particular regard to the Higher-Order Frequency Response Functions. An important observation is that the appearances of the non-linear harmonic components and the emerging anti-resonances in Higher-Order Frequency Response Functions can provide useful information on the presence of cracks and may be used on an on-line crack monitoring system for small levels of damage. Efficiency of the proposed methodology is illustrated through numerical examples for a pipeline beam including a breathing crack. © 2012 Elsevier Ltd. All rights reserved.


Mathia T.G.,CNRS Tribology and Dynamic Systems Laboratory | Pawlus P.,Rzeszow University of Technology | Wieczorowski M.,Poznan University of Technology
Wear | Year: 2011

This paper describes future trends in surface metrology. Measurement techniques are briefly mentioned. A special attention was paid to tactile and optical methods. Selected problems of surface topography characterization are described. The effects of sampling and filtering on surface topography representation are analysed. Structured surfaces are becoming both technologically and economically critical. Therefore their description is a problem of a great practical importance. Multi-process textures are very important from functional point of view. Various methods of their description are compared. Surface texturing as a means for enhancing tribological properties of frictional pairs started to be extremely popular from for about last 10 years. The effects of surface texturing on improving tribological properties of sliding assemblies are analysed. The other influences of surface topography are mentioned in this paper. © 2010 Elsevier B.V.


Sarrouy E.,CNRS Tribology and Dynamic Systems Laboratory | Dessombz O.,CNRS Tribology and Dynamic Systems Laboratory | Sinou J.-J.,CNRS Tribology and Dynamic Systems Laboratory
Journal of Sound and Vibration | Year: 2013

This paper proposes numerical developments based on polynomial chaos (PC) expansions to process stochastic eigenvalue problems efficiently. These developments are applied to the problem of linear stability calculations for a simplified brake system: the stability of a finite element model of a brake is investigated when its friction coefficient or the contact stiffness are modeled as random parameters. Getting rid of the statistical point of view of the PC method but keeping the principle of a polynomial decomposition of eigenvalues and eigenvectors, the stochastic space is decomposed into several elements to realize a low degree piecewise polynomial approximation of these quantities. An approach relying on continuation principles is compared to the classical dichotomy method to build the partition. Moreover, a criterion for testing accuracy of the decomposition over each cell of the partition without requiring evaluation of exact eigenmodes is proposed and implemented. Several random distributions are tested, including a uniform-like law for description of friction coefficient variation. Results are compared to Monte Carlo simulations so as to determine the method accuracy and efficiency. Some general rules relative to the influence of the friction coefficient or the contact stiffness are also inferred from these calculations. © 2012 Elsevier Ltd.


Fabbri A.,CNRS Tribology and Dynamic Systems Laboratory | Fen-Chong T.,University Paris Est Creteil
Cold Regions Science and Technology | Year: 2013

The goal of this paper is to investigate the validity of indirectly built ice content curves from porous network characterization tests to predict the behavior of a freezing cement based material. To do so, the results obtained by the two classical methods, namely the mercury intrusion porosimetry (MIP) and the gravimetric water desorption (WD) tests, are compared with the direct measurement of the ice content with a dielectric capacitive apparatus. A corrective approach, based on an interface energy analysis between the in-pore phases, is proposed in order to increase the accuracy of MIP based prediction of the ice saturation curve. The impact of the method used to estimate the ice saturation curve on the behavior of freezing porous medium is evaluated and discussed in the framework of poromechanics. © 2013 Elsevier B.V.


Rigaud E.,CNRS Tribology and Dynamic Systems Laboratory | Le Bot A.,CNRS Tribology and Dynamic Systems Laboratory
Wear | Year: 2013

Experiments are performed to analyze wear generated by low load sliding impacts on ferrite steel and stainless steel samples. Low load impacts are defined by a normal force such that the apparent contact pressure remains below the yield strength of the material. Nevertheless, concentration of pressure at the top of asperities may generate local plastic deformation. Beyond a running-in period, repetitive oblique impacts cause wear. A high frequency acquisition of dynamical contact forces allows an accurate characterization of impacts (rate, duration, strength) and forces (tangential and normal components and their ratio). These data are correlated with wear volume. The effect of the incidence angle is discussed. The results obtained confirm the combined effects of incidence angle and force ratio on the effective wear of impacts. An erosive wear model is introduced whose results explain all experimental observations. The normalized shear energy seems to be relevant in accounting for the measured evolution of wear with impacts orientation. © 2013 Elsevier B.V.


Bruchon J.,CNRS Tribology and Dynamic Systems Laboratory | Drapier S.,CNRS Tribology and Dynamic Systems Laboratory | Valdivieso F.,Ecole Nationale Superieure des Mines de Saint - Etienne CMP
International Journal for Numerical Methods in Engineering | Year: 2011

Within the context of the sintering process simulation, this paper proposes a numerical strategy for the direct simulation of the matter transport by surface diffusion, in two and three dimensions. The level set formulation of the surface diffusion problem is first established. The resulting equations are solved by using a finite element method. A stabilization technique is then introduced, in order to avoid the spurious oscillations of the grain boundary that are a consequence of the dependence of the surface velocity on the fourth-order derivative of the level set function. The convergence and the accuracy of this approach are proved by investigating the change in an elliptic interface under surface diffusion. Cases in direct relation with the sintering process are analyzed besides: sintering between two grains of the same size or of two different sizes. Finally, 3D simulations involving a small number of particles show the ability of the proposed strategy to deal with strong deformations of the grain surface (formation of necks) and to access directly important parameters such as the closed porosity rate. © 2010 John Wiley & Sons, Ltd.

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