Publications

2000

• Study of the mechanical behaviour of plasma deposited silica films on polycarbonates and steel
  
  • Hofrichter Alfred
  • Constantinescu Andrei
  • Benayoun Stéphane
  • Bulkin Pavel
  • Drévillon Bernard
  Journal of Vacuum Science & Technology A, American Vacuum Society, 2000, 18, pp.2012-2014. In the present study, we deposited amorphous hydrogenated silicon oxide films on polycarbonate, stainless steel, and silicon by plasma enhanced chemical vapor deposition using a low pressure, high density integrated distributed electron cyclotron resonance plasma reactor. Substrate curvature, vibrating slab, and Vickers indentation experiments were used to evaluate the intrinsic stress, the Young modulus of the films, and the composite hardness of the film–substrate system. The indentation experiments were modeled by finite element analysis and the calculated values were compared to experimentally measured hardness values. A reasonable accordance with the experiment was found both for stainless-steel and polycarbonate substrates, indicating that the modeling is valid and may be used to enhance the interpretation of the indentation experiments. The calculations show an important bending of the film in the noncontact region in the case of a Vickers indentation on a coated polycarbonate sample. The analysis of the thus-induced strain distribution in the coating indicates that the measured diagonal might be overestimated and not representative of the real contact area. The calculations indicate that the yield limit of the plasma-deposited silica films is of about 4 GPa. (10.1116/1.582464)
  DOI : 10.1116/1.582464
• Effet de la fréquence de sollicitation et de l'environnement sur la propagation des fissures de fatigue en mode II dans l'acier maraging M250
  
  • Doquet V.
  , 2000. No abstract provided
• Stability and Nonlinear Solid Mechanics
  
  • Nguyen Quoc Son
  , 2000, pp.416 pages. Although the problem of stability and bifurcation is well understood in Mechanics, very few treatises have been devoted to stability and bifurcation analysis in dissipative media, in particular with regard to present and fundamental problems in Solid Mechanics such as plasticity, fracture and contact mechanics. Stability and Nonlinear Solid Mechanics addresses this lack of material, and proposes to the reader not only a unified presentation of nonlinear problems in Solid Mechanics, but also a complete and unitary analysis on stability and bifurcation problems arising within this framework. Main themes inlude : . elasticity and plasticity problems in small and finite deformation . general concepts of stability and bifurcation and basic results . elastic buckling . plastic buckling of structures . standard dissipative systems obeying maximum dissipation. These themes are developped in 20 chapters and illustrated by various analytical and numerical results. The coverage given here extends beyond the limited boundaries of previous works, resulting in a text of lasting interest and value to postgraduate students, researchers and practitioners working in mechanical, civil and aerospace engineering, as well as materials science.
• Behaviour characterisations of sheet metals, metallic honeycombs and foams at high and medium strain rates
  
  • Zhao H.
  • Gary G.
  Key Engineering Materials, Trans Tech Publications, 2000, 177-180, pp.225-230. This paper deals with dynamic testing and modelling of the metallic materials and soft structural material made of metals such aluminium honeycombs and foams. Tests are performed with the SHPB (Split Hopkinson Pressure Bar) system which is frequently used in a range of strain rates which correspond to those involved in most of civil industrial applications. Improvements of the SHPB were necessary in order to obtain reliable results on soft structural materials. Some experimental results and their modelling for metals as well as for aluminium honeycombs and foams wil1 be presented. (10.4028/www.scientific.net/KEM.177-180.225)
  DOI : 10.4028/www.scientific.net/KEM.177-180.225
• Computational and experimental investigations of the local strain field in elastoplastic two-phase materials
  
  • Doumalin Pascal
  • Bornert Michel
  • Soppa Ewa
  , 2000, pp.323-328.
• Surface deformation analysis of composites by mesomechanics
  
  • Soppa E.
  • Doumalin Pascal
  • Bornert Michel
  • Schmauder S.
  , 2000, 3, pp.443-449. No abstract provided
• Micromechanical applications of digital image correlation techniques
  
  • Doumalin P.
  • Bornert Michel
  , 2000, pp.67-74. No abstract provided
• A Concept for Earthquake-Resistant Design of Underground Structures: Stress Response Spectrum
  
  • Kurose Ayumi
  • Bérest Pierre
  , 2000, pp.1043-1049. This paper introduces a method to evaluate the mechanical effects induced in the cross-section of an underground structure, constructed in a medium of great thickness, under earthquake ground motion. Damage observations after large earthquakes (e.g., Kobe, 1995) have shown the cross-sectional vulnerability of underground structures at shallow or great depth. Present earthquake-resistant design standards only suggest calculation methods for structures constructed in a soil laying over a rigid basement and cannot be applied to a structure constructed in a medium of great thickness, such as a tunnel, an underground hydrocarbon storage facility or a nuclear-waste disposal site. Thus, development of a systematic method to evaluate the seismic effects induced in the cross-section of a structure in an unbounded medium is of interest. The approach proposed here is conceptually similar to that used for earthquake response analysis of buildings: using a simple but realistic model of an underground linear structure (a 2D cavity with circular cross-section in an infinite, elastic, linear, homogeneous and isotropic medium) and real earthquake records, we propose a response spectrum more suitable, than the usual velocity or acceleration response spectrum, for analyzing the structural stability of underground construction during earthquakes: the Stress Response Spectrum (SRS), which is defined as the maximum value of the maximum shear stress at the cavity wall during the duration of ground motion. The SRS values are computed by using 21 earthquake motions (provided by the Japan Meteorological Agency) of magnitude higher than 4, which were recorded by the Japan Nuclear Cycle Research Institute (JNC) in a 315-meter deep gallery excavated in an a granodioritic rock mass at the Kamaishi Mine in Iwate, Japan. In light of the numerical analysis, the SRS appears to be a potential tool for the earthquake-response analysis of underground structures. The Stress Response Spectrum will provide engineers with the order of magnitude of mechanical effects in an underground structure for a given earthquake motion; conversely, for a given target SRS, may assist in producing a design earthquake more suitable for analysis of deep underground structures than those currently available.
• Modelisation d un contact plan/plan entre un graphite et du Ti6Al4V renforce TiC : essai de tribocorrosion anneau/disque, analyse de l usure des materiaux
  
  • Serre I.
  • Celati N.
  • Pradeilles Duval R. M.
  , 2000. No abstract provided
• Thermodynamical description of moving discontinuities : application to fracture and wear
  
  • Stolz C.
  , 2000, pp.1463-1468. No abstract provided
• Dissipation intrinsèque d'un matériau sableux
  
  • Luong M. P.
  , 2000, pp.127-132. No abstract provided
• Solid-fluid phase transformation within grain boundaries
  
  • Leroy Yves M
  • Ghoussoub Joumana
  , 2000. The overall compaction of porous rocks due to intergranular pressure solution (IPS) results from the dissolution of minerals within contact regions and the diffusive transport through the grain boundary of the dissolved species towards the fluid-filled pore space. The grain boundary structure can be imagined to be composed of dry contact zones, thin fluid films and fluid-filled cavities. The connectiveness and tortuosity of this structure determine the effective diffusivity of grain contacts and thus the potential of porous rock to compact by the action of IPS. The evolution in time of the grain-boundary structure, and thus of the effective diffusivity, is discussed here with the help of two 2D initial- and boundary-value problems which are solved by analytical and numerical means. The evolution of the solid–fluid interfaces within the grain boundary is governed by a phase transformation between the non-hydrostatically stressed elastic solid and the trapped fluid assumed in mechanical equilibrium. The characteristic time is provided by a linear kinetic law. The evolution of the structure away from a state of thermodynamic equilibrium during a loading normal to the grain boundary is found to occur in two steps. The first one consists of a diffuse morphology evolution in time and results in an enhancement of any initial stress concentration. The second step is characterized by a rapid and localized dissolution in the region of stress concentration. The latency period prior to localization is governed by the magnitude of the non-hydrostatic remote stress as well as the microstructural geometric factor responsible for the initial stress concentration at the solid–fluid interface. The localized dissolution is shown to provide a mechanism for the fluid to penetrate a previously dry contact region by marginal dissolution and thus to create a fluid film. However, the newly formed thin fluid layer is found to be unstable pointing to a possible repeated reorganization or dynamic evolution of the grain boundary internal structure during the action of IPS. (10.1016/S0022-5096(01)00012-6)
  DOI : 10.1016/S0022-5096(01)00012-6
• Plastic heterogeneities of a copper multicrystal deformed in uniaxial tension: experimental study and finite element simulations
  
  • Delaire F.
  • Raphanel Jean L
  • Rey Colette
  Acta Materialia, Elsevier, 2000, 48, pp.1075-1087. A copper sample made of a single layer of grains is plastically deformed by uniaxial tension at room temperature and low strain rate. The deformation field is measured by means of grids deposited on the polished surface of the undeformed specimen and local orientations are recorded using electron back scattering diagrams in a scanning electron microscope. These measures are compared with simulations made by a finite element code using a physically based model for the deformation and hardening of face centered cubic crystals. A good agreement is found between measured and computed values. The simulations give access to much more detail about the history of glide in each grain and help establish which systems are active at a local level. They also provide the evolution of internal variables such as dislocation densities. A new insight into intergranular accommodation as well as intragranular heterogeneities is provided. (10.1016/S1359-6454(99)00408-5)
  DOI : 10.1016/S1359-6454(99)00408-5
• An inverse approach to determine the non-linear properties of induction heat-treated steels
  
  • Niclas André
  • Bourgeois Lament
  European Journal of Mechanics - A/Solids, Elsevier, 2000, 19, pp.69-88. The identification of the through-the-thickness variation of the non-linear properties of a steel structure due to a heat treatment by induction is considered. An inverse approach to that problem is proposed, which is based on a 4-point bending test of a heat-treated parallelepipedic bar. It includes a layer-removal method for measuring residual stresses. Precisely, two different inverse methods are described. For a medium carbon steel, an application based on experimental data is performed, which shows the efficiency of our approach and a good agreement between the two methods. (10.1016/S0997-7538(00)00152-2)
  DOI : 10.1016/S0997-7538(00)00152-2
• Application of modal analysis and synthesis of reed and pipe to numerical simulations of a clarinet
  
  • Facchinetti Matteo
  • Boutillon Xavier
  • Constantinescu Andrei
  , 2000, 108 (5), pp.2590-2590. A finite-element model of a complete clarinet is proposed in order to simulate the acoustical dynamics of the instrument. Following the work of Pinard and Laine on isolated reeds [unpublished reports of the Ecole Polytechnique], modal analysis of clarinet reeds performed with holographic interferometry has been compared with modal synthesis derived from the FEM. In this linear model, the reed is considered alone first, then coupled to the mouthpiece, and finally to the mouthpiece and the barrel. The good agreement between the two approaches makes the mixed solid-acoustical FEM usable in a numerical simulation of the whole clarinet. The rest of the pipe is modeled by lumped mechanical elements whose parameters are fitted with measurements of the acoustical input impedance. Eigenmodes of the complete system—reed, mouthpiece, barrel, pipe—are computed and damping is subsequently attributed to each mode. The evolution of the system subject to nonlinear boundary conditions—incoming airflow, one-sided contact of the reed against the curved lay of the mouthpiece—is computed in the time domain: at each time step, external forces and internal variables are projected onto the modal basis and the evolution of each modal amplitude is integrated. Findings of the simulations will be discussed. <p style="color:red">[NO PDF]</p> (10.1121/1.4743630)
  DOI : 10.1121/1.4743630
• Une approche non destructive pour l'identification de contraintes de contact
  
  • Ben Abdallah J.
  • Bonnet Marc
  Comptes Rendus de l'Academie des Sciences Serie II, Gauthier-Villars, 2000, 328, pp.525-529. Cette note concerne une méthode non destructive d'identification de la distribution de contraintes de contact entre un poinçon rigide et un massif élastique semi-infini au moyen de mesures du déplacement normal et des déformations tangentielles à la surface libre du massif. Les résultats numériques, obtenus pour des configurations axisymétriques, valident cette méthode, y compris en présence de données expérimentales inexactes et quand la zone de contact n'est pas a priori exactement connue (expérience d'indentation). (10.1016/S1620-7742(00)00022-2)
  DOI : 10.1016/S1620-7742(00)00022-2
• Genetic Programming and Domain Knowledge: Beyond the limitations of grammar-guided Machine Discovery
  
  • Ratle Alain
  • Sebag Michèle
  , 2000, pp.211-220. Application of Genetic Programming to the discovery of empirical laws is often impaired by the huge size of the domains involved. In physical applications, dimensional analysis is a powerful way to trim out the size of these spaces This paper presents a way of enforcing dimensional constraints through formal grammars in the GP framework. As one major limitation for grammar-guided GP comes from the initialization procedure (how to find admissible and sufficiently diverse trees with a limited depth), an initialization procedure based on dynamic grammar pruning is proposed. The approach is validated on the problem of identification of a materials response to a mechanical test. (10.1007/3-540-45356-3_21)
  DOI : 10.1007/3-540-45356-3_21
• Treatment of singular integrals in 3D symmetric Galerkin boundary element method
  
  • Mouhoubi Saida
  • Ulmet L.
  • Bonnet Marc
  , 2000. No abstract provided
• On viscous fluid flow near the moving crack tip
  
  • Bui Huy Duong
  • Guyon Corinne
  • Thomas Bernadette
  , 2000, 76, pp.63-74. We consider a crack partially filled with a fluid. We show that the presence of a lag avoids the appearance of pressure and velocity singularities. For the static equilibrium, we recall the previous result on the Capillary Stress Intensity Factor which provides a purely mechanical explanation of the Rehbinder effect, according to which the toughness of the material can be lowered by humidity. For the steady state propagation of a crack due to viscous fluid flow, we set the coupled system of non-linear equations. (10.1007/0-306-46946-4_4)
  DOI : 10.1007/0-306-46946-4_4
• Modelisation of dynamic crack propagation criteria
  
  • Karimzada T.
  • Maigre H.
  Journal de Physique IV Proceedings, EDP Sciences, 2000, 10, pp.461-466. The aim of this study is the analysis of the dynamic crack propagation criteria in materials under impact loading. We want to define which mechanical quantities monitor the propagation, then use these parameters in numerical simulations and finally compare the results with dynamic propagation experiments. First, we propose a 1D semi-analytical model. In this model several mechanical quantities can be used to define the propagation criterion, like the energy release rate... The effect of the applied loading and the reflections of waves is also very important, leading sometimes to a stick-slip propagation. Next, we present a 2D modelisation. In this case, it is not possible to study analytically the effect each criterion and we need to use a numerical simulation. We propose a numerical method based on finite element. The propagation is simulated by releasing nodes with a the release criterion defined from the propagation criterion. The numerical scheme is chosen to respect the equivalence between the total dissipation and the fracture dissipation. In parallel, we have performed dynamic propagation experiments on PMMA. The samples are DCB specimens loading with a wedge in a Kolsky set-up. During each test, the location of the crack has been recorded 4 times with high speed cameras (1 microsecond shutter). (10.1051/jp4:2000977)
  DOI : 10.1051/jp4:2000977
• Spatial localization of the error of constitutive law for the identification of defects in elastic bodies
  
  • Bui Huy Duong
  • Constantinescu Andreï
  Archives of Mechanics, Polish Scientific Publishers Pwn, 2000, 52, pp.511-522. The error on constitutive law (ECL) is a cost functional currently used in inverse problems for identifying interior distribution of coefficients of partial differential equations from overspecified boundary conditions. In previous works, different authors have shown that the ECL permits a good spatial localization of the perturbations of the coefficients. The purpose of this paper is to justify this spatial localization property. The result is obtained for the elliptic equations of elasticity using boundary integral representations of the solutions and comparing the linear and the perturbed solution of the problem.
• A BEM- and adjoint variable-based approach to crack shape sensitivity analysis
  
  • Bonnet Marc
  • Burczynski T.
  • Nowakowski M.
  , 2000, pp.169-176. This communication addresses a computation strategy, based on the adjoint variable approach and BIE/BEM formulations of the direct problem, for evaluating crack or void shape sensitivities of objective functionals. Boundary-only expressions for such sensitivities are sought, in the context of linear elastodynamics. In the case of a void, boundary-only expressions for sensitivities of integral functionals defined on (part of) the external boundary are easy to obtain by the standard adjoint variable approach. When the void degenerates to a crack, the previous result ceases to be applicable, however, because non-integrable terms arise due to crack-tip singularities. We show, for two classes of crack perturbations, that boundaryonly sensitivity expressions using an adjoint state can still be obtained: (1) simple transformations (translation, rotation or expansion of the crack) of arbitrarily shaped domains, and (2) general two-dimensional geometries and crack perturbations. In the latter case, the shape sensitivity is expressed using the primal and adjoint stress intensity factors. Numerical tests of the latter kind of sensitivity expression are presented for a 2-D body with an internal crack, in plane-strain elastodynamics. The influence of crack shape perturbations on an objective functional is examined. The sensitivity results obtained using the present strategy compare well with finite difference evaluations.
• Infrared thermography of the tensile behavior of natural gut string
  
  • Luong M. P.
  , 2000, pp.423-430. No abstract provided
• On the indentification of planar cracks in 3D acoustics
  
  • Bui Huy Duong
  • Constantinescu Andrei
  • Maigre Hubert
  , 2000, pp.181-190.
• Deformation mechanisms and strain localization at the brittle-ductile transition of the continental crust in extension
  
  • Gueydan Frédéric
  • Leroy Yves
  • Jolivet Laurent
  , 2000.