Publications

2001

• Increasing the maximum strain measured with the elastic and viscoelastic Hopkinson bars
  
  • Othman Ramzi
  • Bussac Marie-Noëlle
  • Collet Pierre
  • Gary Gérard
  , 2001.
• θ-Subsumption in a Constraint Satisfaction Perspective
  
  • Maloberti Jérôme
  • Sebag Michèle
  , 2001, 2157, pp.164-178. The covering test intensively used in Inductive Logic Programming, i.e. θ-subsumption, is formally equivalent to a Constraint Satisfaction problem (CSP). This paper presents a general reformulation of θ-subsumption into a binary CSP, and a new θ-subsumption algorithm, termed Django, which combines some main trend CSP heuristics and other heuristics specifically designed for θ-subsumption. Django is evaluated after the CSP standards, shifting from a worst-case complexity perspective to a statistical framework, centered on the notion of Phase Transition (PT). In the PT region lie the hardest on average CSP instances; and this region has been shown of utmost relevance to ILP [4]. Experiments on artificial θ-subsumption problems designed to illustrate the phase transition phenomenon, show that Django is faster by several orders of magnitude than previous θ-subsumption algorithms, within and outside the PT region. (10.1007/3-540-44797-0_14)
  DOI : 10.1007/3-540-44797-0_14
• On shakedown theorems in hardening plasticity
  
  • Nguyen Quoc Son
  • Pham Duc Chinh
  Comptes rendus de l’Académie des sciences. Série IIb, Mécanique, Elsevier, 2001, 329, pp.307-314. The model of generalized standard materials gives a convenient framework to extend Koiter's shakedown theorems into hardening plasticity. The extension of the static shakedown theorem (Melan–Koiter's theorem), proposed previously in [5], is considered here. It leads to the definition of safety coefficients in hardening plasticity by duality. Static and kinematic approaches are discussed for the models of isotropic hardening, of linear kinematic hardening (Ziegler–Prager's model) and of limited kinematic hardening. This discussion also leads to an extension of Koiter's kinematic shakedown theorem and to a second kinematic coefficient. (10.1016/S1620-7742(01)01321-6)
  DOI : 10.1016/S1620-7742(01)01321-6
• Grain-size-sensitive flow and shear-stress enhancement at the brittle-ductile transition of the continental crust
  
  • Gueydan Frédéric
  • Leroy Yves
  • Jolivet Laurent
  International Journal of Earth Sciences, Springer Verlag, 2001, 90 (1), pp.181-196. Localized shear zones along low-angle normal faults have been identified in regions of extension at the brittle–ductile transition of the continental crust. The possibility of the strain localizing at a depth of 10 km is interpreted here as a consequence of an increase in the equivalent shear stress applied to the flow of the lower crust. This enhancement of the flow stress is seen as a prerequisite for the triggering of brittle deformation mechanisms leading to strain localization. The lower crust rheology used to examine this stress increase is strain-rate, temperature and grain-size dependent, due to the coupling of dislocation and diffusion creep. The model structure proposed consists of a top layer, the upper crust, gliding rigidly above a bottom layer, the lower crust, which deforms in simple shear. During a short time interval (1400 years), the equivalent shear stress is found to increase by a factor of up to 3 (67 MPa for anorthite and 17 MPa for quartz). For anorthite, this stress could explain the activation of a Mohr-Coulomb failure with a friction coefficient of 0.2, which is reasonable at the depth of 10 km. Dislocation creep is activated during a rapid change in the prescribed velocity, whereas diffusion creep dominates if the velocity is held constant, highlighting the importance of grain-size sensitivity for lower crustal rheology. (10.1007/s005310000160)
  DOI : 10.1007/s005310000160
• Modélisation micromécanique de la phase lamellaire des alliages TiAl
  
  • Gélébart Lionel
  • Bretheau Thierry
  • Crépin Jérôme
  • Bornert Michel
  , 2001.
• Taking advantage of complete or partial geometrical symmetry in Symmetric Galerkin BEM formulations
  
  • Bonnet Marc
  , 2001. No abstract provided
• Observation infrarouge de l'endommagement des cordes de tennis
  
  • Luong M. P.
  , 2001. No abstract provided
• Multidisciplinary design of woven composites
  
  • Zarka J.
  • Doux T.
  , 2001. No abstract provided
• Multiaxial fatigue criteria based on a multiscale approach
  
  • Dang Van K.
  , 2001, pp.457-463. Prediction of high-cycle fatigue resistance is of great importance for structural design. In spite of this clear industrial need, until now modeling of metal behavior in a high-cycle fatigue regime was often based on empirical approaches: the Wöhler curve and the Goodman-Haigh or Gerber diagrams are still the very popular tools for engineers. However, these concepts are not appropriate when studying the multiaxial stress cycles that are frequently encountered on modem mechanical components. These multiaxial stresses arise from factors such as external loadings, the geometry of the structure, which can induce multiaxiality even if the loading is uniaxial, and finally residual stresses. (10.1016/B978-012443341-0/50052-1)
  DOI : 10.1016/B978-012443341-0/50052-1
• Branch crack development from the flank of a fatigue crack propagating in mode II
  
  • Doquet Véronique
  • Frelat Joël
  Fatigue and Fracture of Engineering Materials and Structures, Wiley-Blackwell, 2001, 24 (3), pp.207-214. The propagation of fatigue cracks in mode II often leads to the development of a branch starting from a crack flank, some distance behind the tip and not to the expected bifurcation at the crack tip. This type of branch is suggested to initiate by decohesion along a secondary slip plane and to grow in mode I due to the tensile component of the mode II stress field. Finite element calculations are performed to evaluate the stress intensity factors for the main crack and the branch as a function of the position of the latter. It is shown that the branch has a substantial shielding effect on the main crack and generates contact forces along its flanks. The simultaneous and competitive growth of the main crack and the branch in fatigue is simulated step by step using kinetic data for mode II and mode I obtained for a maraging steel. (10.1046/j.1460-2695.2001.00384.x)
  DOI : 10.1046/j.1460-2695.2001.00384.x
• Homogénéisation en mécanique des matériaux
  
  • Bornert Michel
  • Bretheau Thierry
  • Gilormini Pierre
  , 2001, pp.250 pages.
• Approches multi-échelles en Mécanique des Matériaux
  
  • Zaoui A.
  , 2001.
• On the Use of Visco-Elastodynamic BIEM Solutions for Underground Cavity Detection
  
  • Guzina B. B.
  • Nintcheu S.
  • Bonnet Marc
  , 2001, pp.491-498. No abstract provided
• Utilisation de symétries géométriques totales ou partielles dans la méthode des éléments de frontière
  
  • Bonnet Marc
  , 2001, pp.659-666. No abstract provided
• A spectral method for wave dispersion analysis. Application to an aluminum rod
  
  • Ohtman Ramzi
  • Blanc Robert
  • Bussac Marie-Noëlle
  • Collet Pierre
  • Gary Gérard
  , 2001, pp.71-76. The spectral analysis of a single wave measurement (for instance strain measurement) on a rod exhibits multiple resonant frequencies. Wave celerity is inferred from the resonance position and attenuation is deduced from the resonance bandwidth. Dispersion is therefore computed on a countable set of frequencies. This method does not need any limitation of the loading pulse. When applied to an aluminium rod, the method allows for the measurement of the damping and the dispersion relations for a frequency range up to 50 kHz. It is found out in this case that damping is non zero. Results are checked using the wave propagation description in a real rod. They show to be of a high accuracy. This method can be applied to any one-dimensional and single-mode propagating waves (for example flexural waves in beams).
• Approches par les potentiels
  
  • Bornert Michel
  • Suquet P.
  , 2001, pp.45-90.
• Plasticité: approches en champ moyen
  
  • Zaoui A.
  , 2001, pp.17-44.
• Approche expérimentale de l'homogénisation
  
  • Bretheau T.
  , 2001, pp.147-169.
• Changement d'échelle: motivation et méthodologie
  
  • Zaoui A.
  , 2001, pp.19-39.
• On a predictive macroscopic contact-sliding wear model based on micromechanical considerations
  
  • Dragon-Louiset Marta
  International Journal of Solids and Structures, Elsevier, 2001, 38, pp.1625-1639. A model for the mild wear of two contacting solids and an analytical example are proposed in this article. The model includes the presence of an interface made of damaged materials, fluid and wear debris. It consists in a wear criterion, an interface law and complementary relations deduced from the mass conservation. A thermodynamical analysis provides energy-release rates associated with the evolution of the surfaces in contact and the mass fluxes due to wear. They are used as characteristic quantities in the formulation of the wear criterion and wear velocities. Given that the physics of the interface modify the global contact conditions, micromechanical considerations are developed and result in an interface law, modeling its evolution with an internal parameter: the volume fraction of wear debris. The relation between this parameter and wear velocities is obtained with the mass conservation equation, which completes the model and allows to apply it in a numerical simulation. As an example, a problem of a rigid punch sliding on an elastic worn-out half-plane is treated by means of integral equations, accounting on the presence of an interface according to the previous modeling. Stresses and strains are obtained analytically, as asymptotic expansion fields. (10.1016/S0020-7683(00)00065-2)
  DOI : 10.1016/S0020-7683(00)00065-2
• On the identification of elastoviscoplastic constitutive laws from indentation tests
  
  • Constantinescu Andreï
  • Tardieu Nicolas
  Inverse Problems in Engineering, Informa UK (Taylor & Francis), 2001, 9, pp.19-44. This paper addresses the identification of the parameters of a nonlinear constitutive law from indentation tests. The identification problem is considered as a constrained minimization problem and the gradient is computed using the adjoint state method, in spite of the difficulties of the underlying contact problem. This provides a general framework to perform optimization in some problems involving contact conditions and nonlinear material behaviour. The case of a Maxwell viscoelastic and a Norton-Hoff elastoviscoplastic constitutive law are treated extensively and a series of numerical identification examples are shown. (10.1080/174159701088027751)
  DOI : 10.1080/174159701088027751
• Compared numerical techniques for FEM-BEM coupling
  
  • Mouhoubi Saida
  • Ulmet Laurent
  • Bonnet Marc
  , 2001, pp.249-258.
• Assessment of Welded Structures by a Local Multiaxial Fatigue Approach
  
  • Dang Van Ky
  • Bignonnet André
  • Fayard Jean-Luc
  • Janosch Jean-Jacques
  Fatigue and Fracture of Engineering Materials and Structures, Wiley-Blackwell, 2001, 24 (5), pp.369-376. A new local multiaxial computing method for the fatigue assessment of welded structures is presented. This approach is based on the use of an equivalent stress derived from the multiaxial fatigue criterion proposed by Dang Van for plain machined specimens. Application to fillet welds allows a better description of the influence of local geometries and residual stress states. These factors are related to the weld process and the quality of the weld. This approach, associated with definite shell finite element meshing rules in order to take account of the increase of local rigidity introduced by the weld, is also successfully used to assess the fatigue resistance of welded automotive structures. (10.1046/j.1460-2695.2001.00399.x)
  DOI : 10.1046/j.1460-2695.2001.00399.x
• Back analysis of loading parameters in shallow tunnels
  
  • Deng Desheng
  • Minh Duc Nguyen
  • Constantinescu Andrei
  , 2001 (1), pp.177-183. Convergence Confinement (CV-CF) Method is currently used in geo-engineering practice as a plane strain approximate tunnel calculation, for example, in the scope of a NATM construction procedure. However, although improvements have been recently achieved for some simple cases, this method is impeded by undetermination of the deconfining ratio value λo at the moment when support is laid. A back analysis method has been proposed on the basis of the Virtual Work Principle, in which the original CV-CF model is compared through an iterative process to a modified model in which the field measurements are prescribed. The parameter λo and the lateral stress ratio k0 of soil mass are back analysed. This method is very robust and works also for non linear rock mass behavior. For illustration of this back analysis method, 2D shallow tunnel calculation data are used as experimental data. (10.1201/9781003078562-21)
  DOI : 10.1201/9781003078562-21
• Experimental and numerical analysis of localization during sequential test for an IF-Ti steel
  
  • Hoc Thierry
  • Rey Collette
  • Raphanel Jean
  Acta Materialia, Elsevier, 2001, 49, pp.1835-1846. Localization of plastic deformation in polycrystals often occurs after a change of loading path. An experimental study using several techniques at different scales (scanning electron microscopy, microgrids, local orientation measurements, transmission electron microscopy) has been conducted on mild steel sheets (interstitial free titanium steel) prestrained by plane tension and then deformed by uniaxial tension along the first tensile axis or the transverse axis. In this way localization has been linked to microstructural anisotropy developed during the first loading path. A model based on crystalline plasticity has then been introduced in a finite element code (Abaqus) with a description of intragranular hardening linked to the evolution of the dislocation densities on each slip system. The simulations make use of a finite element representative pattern based on actual grain distribution in the aggregate. The computations predict a localization in good agreement with the experimental data and show a link between saturation of dislocation densities and concentration of plastic deformation. (10.1016/S1359-6454(01)00076-3)
  DOI : 10.1016/S1359-6454(01)00076-3